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https://dev.mysql.com/doc/refman/8.4/en/backup-strategy-example.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h2 class="title">
<a name="backup-strategy-example">
</a>
9.3 Example Backup and Recovery Strategy
</h2>
</div>
</div>
</div>
<div class="toc">
<dl class="toc">
<dt>
<span class="section">
<a href="backup-policy.html">
9.3.1 Establishing a Backup Policy
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="recovery-from-backups.html">
9.3.2 Using Backups for Recovery
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="backup-strategy-summary.html">
9.3.3 Backup Strategy Summary
</a>
</span>
</dt>
</dl>
</div>
<p>
This section discusses a procedure for performing backups that
enables you to recover data after several types of crashes:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
Operating system crash
</p>
</li>
<li class="listitem">
<p>
Power failure
</p>
</li>
<li class="listitem">
<p>
File system crash
</p>
</li>
<li class="listitem">
<p>
Hardware problem (hard drive, motherboard, and so forth)
</p>
</li>
</ul>
</div>
<p>
The example commands do not include options such as
<a class="link" href="connection-options.html#option_general_user">
<code class="option">
--user
</code>
</a>
and
<a class="link" href="connection-options.html#option_general_password">
<code class="option">
--password
</code>
</a>
for the
<a class="link" href="mysqldump.html" title="6.5.4 mysqldump — A Database Backup Program">
<span class="command">
<strong>
mysqldump
</strong>
</span>
</a>
and
<a class="link" href="mysql.html" title="6.5.1 mysql — The MySQL Command-Line Client">
<span class="command">
<strong>
mysql
</strong>
</span>
</a>
client
programs. You should include such options as necessary to enable
client programs to connect to the MySQL server.
</p>
<p>
Assume that data is stored in the
<code class="literal">
InnoDB
</code>
storage engine, which has support for transactions and automatic
crash recovery. Assume also that the MySQL server is under load at
the time of the crash. If it were not, no recovery would ever be
needed.
</p>
<p>
For cases of operating system crashes or power failures, we can
assume that MySQL's disk data is available after a restart. The
<code class="literal">
InnoDB
</code>
data files might not contain consistent
data due to the crash, but
<code class="literal">
InnoDB
</code>
reads its
logs and finds in them the list of pending committed and
noncommitted transactions that have not been flushed to the data
files.
<code class="literal">
InnoDB
</code>
automatically rolls back those
transactions that were not committed, and flushes to its data
files those that were committed. Information about this recovery
process is conveyed to the user through the MySQL error log. The
following is an example log excerpt:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-simple"><div class="docs-select-all right" id="sa74325296"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-simple">InnoDB<span class="token operator">:</span> Database was not shut down normally<span class="token punctuation">.</span>
InnoDB<span class="token operator">:</span> Starting recovery from log files<span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span>
InnoDB<span class="token operator">:</span> Starting log scan based on checkpoint at
InnoDB<span class="token operator">:</span> log sequence number 0 13674004
InnoDB<span class="token operator">:</span> Doing recovery<span class="token operator">:</span> scanned up to log sequence number 0 13739520
InnoDB<span class="token operator">:</span> Doing recovery<span class="token operator">:</span> scanned up to log sequence number 0 13805056
InnoDB<span class="token operator">:</span> Doing recovery<span class="token operator">:</span> scanned up to log sequence number 0 13870592
InnoDB<span class="token operator">:</span> Doing recovery<span class="token operator">:</span> scanned up to log sequence number 0 13936128
<span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span>
InnoDB<span class="token operator">:</span> Doing recovery<span class="token operator">:</span> scanned up to log sequence number 0 20555264
InnoDB<span class="token operator">:</span> Doing recovery<span class="token operator">:</span> scanned up to log sequence number 0 20620800
InnoDB<span class="token operator">:</span> Doing recovery<span class="token operator">:</span> scanned up to log sequence number 0 20664692
InnoDB<span class="token operator">:</span> 1 uncommitted transaction<span class="token punctuation">(</span>s<span class="token punctuation">)</span> which must be rolled back
InnoDB<span class="token operator">:</span> Starting rollback of uncommitted transactions
InnoDB<span class="token operator">:</span> Rolling back trx no 16745
InnoDB<span class="token operator">:</span> Rolling back of trx no 16745 completed
InnoDB<span class="token operator">:</span> Rollback of uncommitted transactions completed
InnoDB<span class="token operator">:</span> Starting an apply batch of log records to the database<span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span>
InnoDB<span class="token operator">:</span> Apply batch completed
InnoDB<span class="token operator">:</span> Started
mysqld<span class="token operator">:</span> ready for connections</code></pre>
</div>
<p>
For the cases of file system crashes or hardware problems, we can
assume that the MySQL disk data is
<span class="emphasis">
<em>
not
</em>
</span>
available after a restart. This means that MySQL fails to start
successfully because some blocks of disk data are no longer
readable. In this case, it is necessary to reformat the disk,
install a new one, or otherwise correct the underlying problem.
Then it is necessary to recover our MySQL data from backups, which
means that backups must already have been made. To make sure that
is the case, design and implement a backup policy.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/performance-schema-events-transactions-current-table.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="performance-schema-events-transactions-current-table">
</a>
29.12.7.1 The events_transactions_current Table
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045072363776">
</a>
<a class="indexterm" name="idm46045072362272">
</a>
<p>
The
<a class="link" href="performance-schema-events-transactions-current-table.html" title="29.12.7.1 The events_transactions_current Table">
<code class="literal">
events_transactions_current
</code>
</a>
table contains current transaction events. The table stores
one row per thread showing the current status of the thread's
most recent monitored transaction event, so there is no system
variable for configuring the table size. For example:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa31548682"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token operator">*</span>
<span class="token keyword">FROM</span> performance_schema<span class="token punctuation">.</span>events_transactions_current <span class="token keyword">LIMIT</span> <span class="token number">1</span>\G
<span class="token output"><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span> 1. row <span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span>
THREAD_ID<span class="token punctuation">:</span> 26
EVENT_ID<span class="token punctuation">:</span> 7
END_EVENT_ID<span class="token punctuation">:</span> NULL
EVENT_NAME<span class="token punctuation">:</span> transaction
STATE<span class="token punctuation">:</span> ACTIVE
TRX_ID<span class="token punctuation">:</span> NULL
GTID<span class="token punctuation">:</span> 3E11FA47-71CA-11E1-9E33-C80AA9429562<span class="token punctuation">:</span>56
XID<span class="token punctuation">:</span> NULL
XA_STATE<span class="token punctuation">:</span> NULL
SOURCE<span class="token punctuation">:</span> transaction.cc<span class="token punctuation">:</span>150
TIMER_START<span class="token punctuation">:</span> 420833537900000
TIMER_END<span class="token punctuation">:</span> NULL
TIMER_WAIT<span class="token punctuation">:</span> NULL
ACCESS_MODE<span class="token punctuation">:</span> READ WRITE
ISOLATION_LEVEL<span class="token punctuation">:</span> REPEATABLE READ
AUTOCOMMIT<span class="token punctuation">:</span> NO
NUMBER_OF_SAVEPOINTS<span class="token punctuation">:</span> 0
NUMBER_OF_ROLLBACK_TO_SAVEPOINT<span class="token punctuation">:</span> 0
NUMBER_OF_RELEASE_SAVEPOINT<span class="token punctuation">:</span> 0
OBJECT_INSTANCE_BEGIN<span class="token punctuation">:</span> NULL
NESTING_EVENT_ID<span class="token punctuation">:</span> 6
NESTING_EVENT_TYPE<span class="token punctuation">:</span> STATEMENT</span></code></pre>
</div>
<p>
Of the tables that contain transaction event rows,
<a class="link" href="performance-schema-events-transactions-current-table.html" title="29.12.7.1 The events_transactions_current Table">
<code class="literal">
events_transactions_current
</code>
</a>
is
the most fundamental. Other tables that contain transaction
event rows are logically derived from the current events. For
example, the
<a class="link" href="performance-schema-events-transactions-history-table.html" title="29.12.7.2 The events_transactions_history Table">
<code class="literal">
events_transactions_history
</code>
</a>
and
<a class="link" href="performance-schema-events-transactions-history-long-table.html" title="29.12.7.3 The events_transactions_history_long Table">
<code class="literal">
events_transactions_history_long
</code>
</a>
tables are collections of the most recent transaction events
that have ended, up to a maximum number of rows per thread and
globally across all threads, respectively.
</p>
<p>
For more information about the relationship between the three
transaction event tables, see
<a class="xref" href="performance-schema-event-tables.html" title="29.9 Performance Schema Tables for Current and Historical Events">
Section 29.9, “Performance Schema Tables for Current and Historical Events”
</a>
.
</p>
<p>
For information about configuring whether to collect
transaction events, see
<a class="xref" href="performance-schema-transaction-tables.html" title="29.12.7 Performance Schema Transaction Tables">
Section 29.12.7, “Performance Schema Transaction Tables”
</a>
.
</p>
<p>
The
<a class="link" href="performance-schema-events-transactions-current-table.html" title="29.12.7.1 The events_transactions_current Table">
<code class="literal">
events_transactions_current
</code>
</a>
table has these columns:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<code class="literal">
THREAD_ID
</code>
,
<code class="literal">
EVENT_ID
</code>
</p>
<p>
The thread associated with the event and the thread
current event number when the event starts. The
<code class="literal">
THREAD_ID
</code>
and
<code class="literal">
EVENT_ID
</code>
values taken together uniquely
identify the row. No two rows have the same pair of
values.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
END_EVENT_ID
</code>
</p>
<p>
This column is set to
<code class="literal">
NULL
</code>
when the
event starts and updated to the thread current event
number when the event ends.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
EVENT_NAME
</code>
</p>
<p>
The name of the instrument from which the event was
collected. This is a
<code class="literal">
NAME
</code>
value from
the
<a class="link" href="performance-schema-setup-instruments-table.html" title="29.12.2.3 The setup_instruments Table">
<code class="literal">
setup_instruments
</code>
</a>
table.
Instrument names may have multiple parts and form a
hierarchy, as discussed in
<a class="xref" href="performance-schema-instrument-naming.html" title="29.6 Performance Schema Instrument Naming Conventions">
Section 29.6, “Performance Schema Instrument Naming Conventions”
</a>
.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
STATE
</code>
</p>
<p>
The current transaction state. The value is
<code class="literal">
ACTIVE
</code>
(after
<a class="link" href="commit.html" title="15.3.1 START TRANSACTION, COMMIT, and ROLLBACK Statements">
<code class="literal">
START
TRANSACTION
</code>
</a>
or
<a class="link" href="commit.html" title="15.3.1 START TRANSACTION, COMMIT, and ROLLBACK Statements">
<code class="literal">
BEGIN
</code>
</a>
),
<code class="literal">
COMMITTED
</code>
(after
<a class="link" href="commit.html" title="15.3.1 START TRANSACTION, COMMIT, and ROLLBACK Statements">
<code class="literal">
COMMIT
</code>
</a>
), or
<code class="literal">
ROLLED
BACK
</code>
(after
<a class="link" href="commit.html" title="15.3.1 START TRANSACTION, COMMIT, and ROLLBACK Statements">
<code class="literal">
ROLLBACK
</code>
</a>
).
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
TRX_ID
</code>
</p>
<p>
Unused.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
GTID
</code>
</p>
<p>
The GTID column contains the value of
<a class="link" href="replication-options-gtids.html#sysvar_gtid_next">
<code class="literal">
gtid_next
</code>
</a>
, which can be
one of
<code class="literal">
ANONYMOUS
</code>
,
<code class="literal">
AUTOMATIC
</code>
, or a GTID using the format
<code class="literal">
UUID:NUMBER
</code>
. For transactions that use
<a class="link" href="replication-options-gtids.html#sysvar_gtid_next">
<code class="literal">
gtid_next=AUTOMATIC
</code>
</a>
,
which is all normal client transactions, the GTID column
changes when the transaction commits and the actual GTID
is assigned. If
<a class="link" href="replication-options-gtids.html#sysvar_gtid_mode">
<code class="literal">
gtid_mode
</code>
</a>
is either
<code class="literal">
ON
</code>
or
<code class="literal">
ON_PERMISSIVE
</code>
, the GTID column changes
to the transaction's GTID. If
<code class="literal">
gtid_mode
</code>
is either
<code class="literal">
OFF
</code>
or
<code class="literal">
OFF_PERMISSIVE
</code>
, the GTID column changes
to
<code class="literal">
ANONYMOUS
</code>
.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
XID_FORMAT_ID
</code>
,
<code class="literal">
XID_GTRID
</code>
, and
<code class="literal">
XID_BQUAL
</code>
</p>
<p>
The elements of the XA transaction identifier. They have
the format described in
<a class="xref" href="xa-statements.html" title="15.3.8.1 XA Transaction SQL Statements">
Section 15.3.8.1, “XA Transaction SQL Statements”
</a>
.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
XA_STATE
</code>
</p>
<p>
The state of the XA transaction. The value is
<code class="literal">
ACTIVE
</code>
(after
<a class="link" href="xa-statements.html" title="15.3.8.1 XA Transaction SQL Statements">
<code class="literal">
XA
START
</code>
</a>
),
<code class="literal">
IDLE
</code>
(after
<a class="link" href="xa-statements.html" title="15.3.8.1 XA Transaction SQL Statements">
<code class="literal">
XA
END
</code>
</a>
),
<code class="literal">
PREPARED
</code>
(after
<a class="link" href="xa-statements.html" title="15.3.8.1 XA Transaction SQL Statements">
<code class="literal">
XA
PREPARE
</code>
</a>
),
<code class="literal">
ROLLED BACK
</code>
(after
<a class="link" href="xa-statements.html" title="15.3.8.1 XA Transaction SQL Statements">
<code class="literal">
XA
ROLLBACK
</code>
</a>
), or
<code class="literal">
COMMITTED
</code>
(after
<a class="link" href="xa-statements.html" title="15.3.8.1 XA Transaction SQL Statements">
<code class="literal">
XA
COMMIT
</code>
</a>
).
</p>
<p>
On a replica, the same XA transaction can appear in the
<a class="link" href="performance-schema-events-transactions-current-table.html" title="29.12.7.1 The events_transactions_current Table">
<code class="literal">
events_transactions_current
</code>
</a>
table with different states on different threads. This is
because immediately after the XA transaction is prepared,
it is detached from the replica's applier thread, and can
be committed or rolled back by any thread on the replica.
The
<a class="link" href="performance-schema-events-transactions-current-table.html" title="29.12.7.1 The events_transactions_current Table">
<code class="literal">
events_transactions_current
</code>
</a>
table displays the current status of the most recent
monitored transaction event on the thread, and does not
update this status when the thread is idle. So the XA
transaction can still be displayed in the
<code class="literal">
PREPARED
</code>
state for the original applier
thread, after it has been processed by another thread. To
positively identify XA transactions that are still in the
<code class="literal">
PREPARED
</code>
state and need to be
recovered, use the
<a class="link" href="xa-statements.html" title="15.3.8.1 XA Transaction SQL Statements">
<code class="literal">
XA
RECOVER
</code>
</a>
statement rather than the Performance
Schema transaction tables.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
SOURCE
</code>
</p>
<p>
The name of the source file containing the instrumented
code that produced the event and the line number in the
file at which the instrumentation occurs. This enables you
to check the source to determine exactly what code is
involved.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
TIMER_START
</code>
,
<code class="literal">
TIMER_END
</code>
,
<code class="literal">
TIMER_WAIT
</code>
</p>
<p>
Timing information for the event. The unit for these
values is picoseconds (trillionths of a second). The
<code class="literal">
TIMER_START
</code>
and
<code class="literal">
TIMER_END
</code>
values indicate when event
timing started and ended.
<code class="literal">
TIMER_WAIT
</code>
is
the event elapsed time (duration).
</p>
<p>
If an event has not finished,
<code class="literal">
TIMER_END
</code>
is the current timer value and
<code class="literal">
TIMER_WAIT
</code>
is the time elapsed so far
(
<code class="literal">
TIMER_END
</code>
−
<code class="literal">
TIMER_START
</code>
).
</p>
<p>
If an event is produced from an instrument that has
<code class="literal">
TIMED = NO
</code>
, timing information is not
collected, and
<code class="literal">
TIMER_START
</code>
,
<code class="literal">
TIMER_END
</code>
, and
<code class="literal">
TIMER_WAIT
</code>
are all
<code class="literal">
NULL
</code>
.
</p>
<p>
For discussion of picoseconds as the unit for event times
and factors that affect time values, see
<a class="xref" href="performance-schema-timing.html" title="29.4.1 Performance Schema Event Timing">
Section 29.4.1, “Performance Schema Event Timing”
</a>
.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
ACCESS_MODE
</code>
</p>
<p>
The transaction access mode. The value is
<code class="literal">
READ
WRITE
</code>
or
<code class="literal">
READ ONLY
</code>
.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
ISOLATION_LEVEL
</code>
</p>
<p>
The transaction isolation level. The value is
<a class="link" href="innodb-transaction-isolation-levels.html#isolevel_repeatable-read">
<code class="literal">
REPEATABLE READ
</code>
</a>
,
<a class="link" href="innodb-transaction-isolation-levels.html#isolevel_read-committed">
<code class="literal">
READ COMMITTED
</code>
</a>
,
<a class="link" href="innodb-transaction-isolation-levels.html#isolevel_read-uncommitted">
<code class="literal">
READ UNCOMMITTED
</code>
</a>
, or
<a class="link" href="innodb-transaction-isolation-levels.html#isolevel_serializable">
<code class="literal">
SERIALIZABLE
</code>
</a>
.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
AUTOCOMMIT
</code>
</p>
<p>
Whether autocommit mode was enabled when the transaction
started.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
NUMBER_OF_SAVEPOINTS
</code>
,
<code class="literal">
NUMBER_OF_ROLLBACK_TO_SAVEPOINT
</code>
,
<code class="literal">
NUMBER_OF_RELEASE_SAVEPOINT
</code>
</p>
<p>
The number of
<a class="link" href="savepoint.html" title="15.3.4 SAVEPOINT, ROLLBACK TO SAVEPOINT, and RELEASE SAVEPOINT Statements">
<code class="literal">
SAVEPOINT
</code>
</a>
,
<a class="link" href="savepoint.html" title="15.3.4 SAVEPOINT, ROLLBACK TO SAVEPOINT, and RELEASE SAVEPOINT Statements">
<code class="literal">
ROLLBACK TO
SAVEPOINT
</code>
</a>
, and
<a class="link" href="savepoint.html" title="15.3.4 SAVEPOINT, ROLLBACK TO SAVEPOINT, and RELEASE SAVEPOINT Statements">
<code class="literal">
RELEASE
SAVEPOINT
</code>
</a>
statements issued during the
transaction.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
OBJECT_INSTANCE_BEGIN
</code>
</p>
<p>
Unused.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
NESTING_EVENT_ID
</code>
</p>
<p>
The
<code class="literal">
EVENT_ID
</code>
value of the event within
which this event is nested.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
NESTING_EVENT_TYPE
</code>
</p>
<p>
The nesting event type. The value is
<code class="literal">
TRANSACTION
</code>
,
<code class="literal">
STATEMENT
</code>
,
<code class="literal">
STAGE
</code>
, or
<code class="literal">
WAIT
</code>
. (
<code class="literal">
TRANSACTION
</code>
does not appear because transactions cannot be nested.)
</p>
</li>
</ul>
</div>
<p>
The
<a class="link" href="performance-schema-events-transactions-current-table.html" title="29.12.7.1 The events_transactions_current Table">
<code class="literal">
events_transactions_current
</code>
</a>
table has these indexes:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
Primary key on (
<code class="literal">
THREAD_ID
</code>
,
<code class="literal">
EVENT_ID
</code>
)
</p>
</li>
</ul>
</div>
<p>
<a class="link" href="truncate-table.html" title="15.1.37 TRUNCATE TABLE Statement">
<code class="literal">
TRUNCATE TABLE
</code>
</a>
is permitted for
the
<a class="link" href="performance-schema-events-transactions-current-table.html" title="29.12.7.1 The events_transactions_current Table">
<code class="literal">
events_transactions_current
</code>
</a>
table. It removes the rows.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/not-enough-file-handles.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="not-enough-file-handles">
</a>
B.3.2.16 File Not Found and Similar Errors
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045054193856">
</a>
<a class="indexterm" name="idm46045054192400">
</a>
<p>
If you get
<code class="literal">
ERROR
'
<em class="replaceable">
<code>
file_name
</code>
</em>
' not found (errno:
23)
</code>
,
<code class="literal">
Can't open file:
<em class="replaceable">
<code>
file_name
</code>
</em>
(errno: 24)
</code>
, or
any other error with
<code class="literal">
errno 23
</code>
or
<code class="literal">
errno 24
</code>
from MySQL, it means that you have
not allocated enough file descriptors for the MySQL server.
You can use the
<a class="link" href="perror.html" title="6.8.1 perror — Display MySQL Error Message Information">
<span class="command">
<strong>
perror
</strong>
</span>
</a>
utility to get a
description of what the error number means:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-terminal"><div class="docs-select-all right" id="sa54150127"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-terminal"><span class="token prompt">$> </span><span class="token command">perror</span> 23
OS error code 23<span class="token punctuation">:</span> File table overflow
<span class="token prompt">$> </span><span class="token command">perror</span> 24
OS error code 24<span class="token punctuation">:</span> Too many open files
<span class="token prompt">$> </span><span class="token command">perror</span> 11
OS error code 11<span class="token punctuation">:</span> Resource temporarily unavailable</code></pre>
</div>
<p>
The problem here is that
<a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
<span class="command">
<strong>
mysqld
</strong>
</span>
</a>
is trying
to keep open too many files simultaneously. You can either
tell
<a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
<span class="command">
<strong>
mysqld
</strong>
</span>
</a>
not to open so many files at
once or increase the number of file descriptors available to
<a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
<span class="command">
<strong>
mysqld
</strong>
</span>
</a>
.
</p>
<p>
To tell
<a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
<span class="command">
<strong>
mysqld
</strong>
</span>
</a>
to keep open fewer files at
a time, you can make the table cache smaller by reducing the
value of the
<a class="link" href="server-system-variables.html#sysvar_table_open_cache">
<code class="literal">
table_open_cache
</code>
</a>
system variable (the default value is 64). This may not
entirely prevent running out of file descriptors because in
some circumstances the server may attempt to extend the cache
size temporarily, as described in
<a class="xref" href="table-cache.html" title="10.4.3.1 How MySQL Opens and Closes Tables">
Section 10.4.3.1, “How MySQL Opens and Closes Tables”
</a>
. Reducing the value of
<a class="link" href="server-system-variables.html#sysvar_max_connections">
<code class="literal">
max_connections
</code>
</a>
also reduces
the number of open files (the default value is 100).
</p>
<a class="indexterm" name="idm46045054172912">
</a>
<p>
To change the number of file descriptors available to
<a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
<span class="command">
<strong>
mysqld
</strong>
</span>
</a>
, you can use the
<a class="link" href="mysqld-safe.html#option_mysqld_safe_open-files-limit">
<code class="option">
--open-files-limit
</code>
</a>
option
to
<a class="link" href="mysqld-safe.html" title="6.3.2 mysqld_safe — MySQL Server Startup Script">
<span class="command">
<strong>
mysqld_safe
</strong>
</span>
</a>
or set the
<a class="link" href="server-system-variables.html#sysvar_open_files_limit">
<code class="literal">
open_files_limit
</code>
</a>
system
variable. See
<a class="xref" href="server-system-variables.html" title="7.1.8 Server System Variables">
Section 7.1.8, “Server System Variables”
</a>
. The
easiest way to set these values is to add an option to your
option file. See
<a class="xref" href="option-files.html" title="6.2.2.2 Using Option Files">
Section 6.2.2.2, “Using Option Files”
</a>
. If you have
an old version of
<a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
<span class="command">
<strong>
mysqld
</strong>
</span>
</a>
that does not
support setting the open files limit, you can edit the
<a class="link" href="mysqld-safe.html" title="6.3.2 mysqld_safe — MySQL Server Startup Script">
<span class="command">
<strong>
mysqld_safe
</strong>
</span>
</a>
script. There is a
commented-out line
<span class="command">
<strong>
ulimit -n 256
</strong>
</span>
in the
script. You can remove the
<code class="literal">
#
</code>
character to
uncomment this line, and change the number
<code class="literal">
256
</code>
to set the number of file descriptors
to be made available to
<a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
<span class="command">
<strong>
mysqld
</strong>
</span>
</a>
.
</p>
<p>
<a class="link" href="mysqld-safe.html#option_mysqld_safe_open-files-limit">
<code class="option">
--open-files-limit
</code>
</a>
and
<span class="command">
<strong>
ulimit
</strong>
</span>
can increase the number of file
descriptors, but only up to the limit imposed by the operating
system. There is also a
<span class="quote">
“
<span class="quote">
hard
</span>
”
</span>
limit that can be
overridden only if you start
<a class="link" href="mysqld-safe.html" title="6.3.2 mysqld_safe — MySQL Server Startup Script">
<span class="command">
<strong>
mysqld_safe
</strong>
</span>
</a>
or
<a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
<span class="command">
<strong>
mysqld
</strong>
</span>
</a>
as
<code class="literal">
root
</code>
(just
remember that you also need to start the server with the
<a class="link" href="server-options.html#option_mysqld_user">
<code class="option">
--user
</code>
</a>
option in this case so
that it does not continue to run as
<code class="literal">
root
</code>
after it starts up). If you need to increase the operating
system limit on the number of file descriptors available to
each process, consult the documentation for your system.
</p>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
If you run the
<span class="command">
<strong>
tcsh
</strong>
</span>
shell,
<span class="command">
<strong>
ulimit
</strong>
</span>
does not work!
<span class="command">
<strong>
tcsh
</strong>
</span>
also reports incorrect values when
you ask for the current limits. In this case, you should
start
<a class="link" href="mysqld-safe.html" title="6.3.2 mysqld_safe — MySQL Server Startup Script">
<span class="command">
<strong>
mysqld_safe
</strong>
</span>
</a>
using
<span class="command">
<strong>
sh
</strong>
</span>
.
</p>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/subquery-errors.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="subquery-errors">
</a>
15.2.15.10 Subquery Errors
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045179643472">
</a>
<a class="indexterm" name="idm46045179641984">
</a>
<p>
There are some errors that apply only to subqueries. This
section describes them.
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
Unsupported subquery syntax:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-none"><div class="docs-select-all right" id="sa73379320"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-none">ERROR 1235 (ER_NOT_SUPPORTED_YET)
SQLSTATE = 42000
Message = "This version of MySQL doesn't yet support
'LIMIT & IN/ALL/ANY/SOME subquery'"</code></pre>
</div>
<p>
This means that MySQL does not support statements like the
following:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa63377028"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SELECT</span> <span class="token operator">*</span> <span class="token keyword">FROM</span> t1 <span class="token keyword">WHERE</span> s1 <span class="token keyword">IN</span> <span class="token punctuation">(</span><span class="token keyword">SELECT</span> s2 <span class="token keyword">FROM</span> t2 <span class="token keyword">ORDER</span> <span class="token keyword">BY</span> s1 <span class="token keyword">LIMIT</span> <span class="token number">1</span><span class="token punctuation">)</span></code></pre>
</div>
</li>
<li class="listitem">
<p>
Incorrect number of columns from subquery:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-none"><div class="docs-select-all right" id="sa49968939"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-none">ERROR 1241 (ER_OPERAND_COL)
SQLSTATE = 21000
Message = "Operand should contain 1 column(s)"</code></pre>
</div>
<p>
This error occurs in cases like this:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa78063251"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SELECT</span> <span class="token punctuation">(</span><span class="token keyword">SELECT</span> column1<span class="token punctuation">,</span> column2 <span class="token keyword">FROM</span> t2<span class="token punctuation">)</span> <span class="token keyword">FROM</span> t1<span class="token punctuation">;</span></code></pre>
</div>
<p>
You may use a subquery that returns multiple columns, if the
purpose is row comparison. In other contexts, the subquery
must be a scalar operand. See
<a class="xref" href="row-subqueries.html" title="15.2.15.5 Row Subqueries">
Section 15.2.15.5, “Row Subqueries”
</a>
.
</p>
</li>
<li class="listitem">
<p>
Incorrect number of rows from subquery:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-none"><div class="docs-select-all right" id="sa85943609"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-none">ERROR 1242 (ER_SUBSELECT_NO_1_ROW)
SQLSTATE = 21000
Message = "Subquery returns more than 1 row"</code></pre>
</div>
<p>
This error occurs for statements where the subquery must
return at most one row but returns multiple rows. Consider
the following example:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa72780581"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SELECT</span> <span class="token operator">*</span> <span class="token keyword">FROM</span> t1 <span class="token keyword">WHERE</span> column1 <span class="token operator">=</span> <span class="token punctuation">(</span><span class="token keyword">SELECT</span> column1 <span class="token keyword">FROM</span> t2<span class="token punctuation">)</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
If
<code class="literal">
SELECT column1 FROM t2
</code>
returns just
one row, the previous query works. If the subquery returns
more than one row, error 1242 occurs. In that case, the
query should be rewritten as:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa25949540"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SELECT</span> <span class="token operator">*</span> <span class="token keyword">FROM</span> t1 <span class="token keyword">WHERE</span> column1 <span class="token operator">=</span> <span class="token keyword">ANY</span> <span class="token punctuation">(</span><span class="token keyword">SELECT</span> column1 <span class="token keyword">FROM</span> t2<span class="token punctuation">)</span><span class="token punctuation">;</span></code></pre>
</div>
</li>
<li class="listitem">
<p>
Incorrectly used table in subquery:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-none"><div class="docs-select-all right" id="sa1565898"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-none">Error 1093 (ER_UPDATE_TABLE_USED)
SQLSTATE = HY000
Message = "You can't specify target table 'x'
for update in FROM clause"</code></pre>
</div>
<p>
This error occurs in cases such as the following, which
attempts to modify a table and select from the same table in
the subquery:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa38864519"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">UPDATE</span> t1 <span class="token keyword">SET</span> column2 <span class="token operator">=</span> <span class="token punctuation">(</span><span class="token keyword">SELECT</span> <span class="token function">MAX</span><span class="token punctuation">(</span>column1<span class="token punctuation">)</span> <span class="token keyword">FROM</span> t1<span class="token punctuation">)</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
You can use a common table expression or derived table to
work around this. See
<a class="xref" href="subquery-restrictions.html" title="15.2.15.12 Restrictions on Subqueries">
Section 15.2.15.12, “Restrictions on Subqueries”
</a>
.
</p>
</li>
</ul>
</div>
<p>
All of the errors described in this section also apply when
using
<a class="link" href="table.html" title="15.2.16 TABLE Statement">
<code class="literal">
TABLE
</code>
</a>
in subqueries.
</p>
<p>
For transactional storage engines, the failure of a subquery
causes the entire statement to fail. For nontransactional
storage engines, data modifications made before the error was
encountered are preserved.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/replication-multi-source.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="replication-multi-source">
</a>
19.1.5 MySQL Multi-Source Replication
</h3>
</div>
</div>
</div>
<div class="toc">
<dl class="toc">
<dt>
<span class="section">
<a href="replication-multi-source-configuration.html">
19.1.5.1 Configuring Multi-Source Replication
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="replication-multi-source-provision-replica.html">
19.1.5.2 Provisioning a Multi-Source Replica for GTID-Based Replication
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="replication-multi-source-adding-gtid-master.html">
19.1.5.3 Adding GTID-Based Sources to a Multi-Source Replica
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="replication-multi-source-adding-binlog-master.html">
19.1.5.4 Adding Binary Log Based Replication Sources to a Multi-Source Replica
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="replication-multi-source-start-replica.html">
19.1.5.5 Starting Multi-Source Replicas
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="replication-multi-source-stop-replica.html">
19.1.5.6 Stopping Multi-Source Replicas
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="replication-multi-source-reset-replica.html">
19.1.5.7 Resetting Multi-Source Replicas
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="replication-multi-source-monitoring.html">
19.1.5.8 Monitoring Multi-Source Replication
</a>
</span>
</dt>
</dl>
</div>
<a class="indexterm" name="idm46045145327696">
</a>
<a class="indexterm" name="idm46045145326608">
</a>
<a class="indexterm" name="idm46045145325104">
</a>
<a class="indexterm" name="idm46045145323600">
</a>
<p>
Multi-source replication in MySQL 8.4 enables a replica
to receive transactions from multiple immediate sources in parallel.
In a multi-source replication topology, a replica creates a
replication channel for each source that it should receive
transactions from. For more information on how replication channels
function, see
<a class="xref" href="replication-channels.html" title="19.2.2 Replication Channels">
Section 19.2.2, “Replication Channels”
</a>
.
</p>
<p>
You might choose to implement multi-source replication to achieve
goals like these:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
Backing up multiple servers to a single server.
</p>
</li>
<li class="listitem">
<p>
Merging table shards.
</p>
</li>
<li class="listitem">
<p>
Consolidating data from multiple servers to a single server.
</p>
</li>
</ul>
</div>
<p>
Multi-source replication does not implement any conflict detection
or resolution when applying transactions, and those tasks are left
to the application if required.
</p>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
Each channel on a multi-source replica must replicate from a
different source. You cannot set up multiple replication channels
from a single replica to a single source. This is because the
server IDs of replicas must be unique in a replication topology.
The source distinguishes replicas only by their server IDs, not by
the names of the replication channels, so it cannot recognize
different replication channels from the same replica.
</p>
</div>
<p>
A multi-source replica can also be set up as a multi-threaded
replica, by setting the system variable
<a class="link" href="replication-options-replica.html#sysvar_replica_parallel_workers">
<code class="literal">
replica_parallel_workers
</code>
</a>
to a value
greater than 0. When you do this on a multi-source replica, each
channel on the replica has the specified number of applier threads,
plus a coordinator thread to manage them. You cannot configure the
number of applier threads for individual channels.
</p>
<p>
MySQL 8.4 also supports replication filters on specific
replication channels with multi-source replicas. Channel specific
replication filters can be used when the same database or table is
present on multiple sources, and you only need the replica to
replicate it from one source. For GTID-based replication, if the
same transaction might arrive from multiple sources (such as in a
diamond topology), you must ensure the filtering setup is the same
on all channels. For more information, see
<a class="xref" href="replication-rules-channel-based-filters.html" title="19.2.5.4 Replication Channel Based Filters">
Section 19.2.5.4, “Replication Channel Based Filters”
</a>
.
</p>
<p>
This section provides tutorials on how to configure sources and
replicas for multi-source replication, how to start, stop and reset
multi-source replicas, and how to monitor multi-source replication.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/.html | <div class="docs-auto-hide-page-toc" id="docs-body">
<div class="book" lang="en">
<div class="titlepage">
<div>
<div>
<h1 class="title">
<a name="refman">
</a>
MySQL 8.4 Reference Manual
</h1>
</div>
<div>
<h2 class="subtitle">
Including MySQL NDB Cluster 8.4
</h2>
</div>
<div>
<div class="abstract">
<p class="title">
<b>
Abstract
</b>
</p>
<p>
This is the MySQL Reference Manual. It documents MySQL
8.4 through 8.4.4, as well as NDB
Cluster 8.4 through 8.4.4,
respectively. It may include documentation of features of MySQL
versions that have not yet been released. For information about
which versions have been released, see the
<a class="ulink" href="/doc/relnotes/mysql/8.4/en/" target="_top">
MySQL
8.4 Release Notes
</a>
.
</p>
<p>
<b>
MySQL 8.4 features.
</b>
This manual describes features that are not included in every
edition of MySQL 8.4; such features may not be
included in the edition of MySQL 8.4 licensed to
you. If you have any questions about the features included in
your edition of MySQL 8.4, refer to your MySQL
8.4 license agreement or contact your Oracle
sales representative.
</p>
<p>
For notes detailing the changes in each release, see the
<a class="ulink" href="/doc/relnotes/mysql/8.4/en/" target="_top">
MySQL
8.4 Release Notes
</a>
.
</p>
<p>
For legal information, including licensing information, see the
<a class="xref" href="preface.html" title="Preface and Legal Notices">
Preface and Legal Notices
</a>
.
</p>
<p>
For help with using MySQL, please visit the
<a class="ulink" href="http://forums.mysql.com" target="_blank">
MySQL Forums
</a>
, where you
can discuss your issues with other MySQL users.
</p>
<p>
Document generated on:
2024-11-12
(revision: 80245)
</p>
</div>
</div>
</div>
<hr/>
</div>
<div class="toc">
<p>
<b>
Table of Contents
</b>
</p>
<dl class="toc">
<dt>
<span class="preface">
<a href="preface.html">
Preface and Legal Notices
</a>
</span>
</dt>
<dt>
<span class="chapter">
<a href="introduction.html">
1 General Information
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="manual-info.html">
1.1 About This Manual
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="what-is.html">
1.2 Overview of the MySQL Database Management System
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="what-is-mysql.html">
1.2.1 What is MySQL?
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="features.html">
1.2.2 The Main Features of MySQL
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="history.html">
1.2.3 History of MySQL
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="mysql-releases.html">
1.3 MySQL Releases: Innovation and LTS
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-nutshell.html">
1.4 What Is New in MySQL 8.4 since MySQL 8.0
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="added-deprecated-removed.html">
1.5 Server and Status Variables and Options Added, Deprecated, or Removed in
MySQL 8.4 since 8.0
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="bug-reports.html">
1.6 How to Report Bugs or Problems
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="compatibility.html">
1.7 MySQL Standards Compliance
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="extensions-to-ansi.html">
1.7.1 MySQL Extensions to Standard SQL
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="differences-from-ansi.html">
1.7.2 MySQL Differences from Standard SQL
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="constraints.html">
1.7.3 How MySQL Deals with Constraints
</a>
</span>
</dt>
</dl>
</dd>
</dl>
</dd>
<dt>
<span class="chapter">
<a href="installing.html">
2 Installing MySQL
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="general-installation-issues.html">
2.1 General Installation Guidance
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="platform-support.html">
2.1.1 Supported Platforms
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="which-version.html">
2.1.2 Which MySQL Version and Distribution to Install
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="getting-mysql.html">
2.1.3 How to Get MySQL
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="verifying-package-integrity.html">
2.1.4 Verifying Package Integrity Using MD5 Checksums or GnuPG
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="installation-layouts.html">
2.1.5 Installation Layouts
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="compiler-characteristics.html">
2.1.6 Compiler-Specific Build Characteristics
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="binary-installation.html">
2.2 Installing MySQL on Unix/Linux Using Generic Binaries
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="windows-installation.html">
2.3 Installing MySQL on Microsoft Windows
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="windows-choosing-package.html">
2.3.1 Choosing an Installation Package
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-configurator.html">
2.3.2 Configuration: Using MySQL Configurator
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="windows-install-archive.html">
2.3.3 Configuration: Manually
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="windows-troubleshooting.html">
2.3.4 Troubleshooting a Microsoft Windows MySQL Server Installation
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="windows-postinstallation.html">
2.3.5 Windows Postinstallation Procedures
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="windows-restrictions.html">
2.3.6 Windows Platform Restrictions
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="macos-installation.html">
2.4 Installing MySQL on macOS
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="macos-installation-notes.html">
2.4.1 General Notes on Installing MySQL on macOS
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="macos-installation-pkg.html">
2.4.2 Installing MySQL on macOS Using Native Packages
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="macos-installation-launchd.html">
2.4.3 Installing and Using the MySQL Launch Daemon
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="macos-installation-prefpane.html">
2.4.4 Installing and Using the MySQL Preference Pane
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="linux-installation.html">
2.5 Installing MySQL on Linux
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="linux-installation-yum-repo.html">
2.5.1 Installing MySQL on Linux Using the MySQL Yum Repository
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="linux-installation-apt-repo.html">
2.5.2 Installing MySQL on Linux Using the MySQL APT Repository
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="linux-installation-sles-repo.html">
2.5.3 Using the MySQL SLES Repository
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="linux-installation-rpm.html">
2.5.4 Installing MySQL on Linux Using RPM Packages from Oracle
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="linux-installation-debian.html">
2.5.5 Installing MySQL on Linux Using Debian Packages from Oracle
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="linux-installation-docker.html">
2.5.6 Deploying MySQL on Linux with Docker Containers
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="linux-installation-native.html">
2.5.7 Installing MySQL on Linux from the Native Software Repositories
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="linux-installation-juju.html">
2.5.8 Installing MySQL on Linux with Juju
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="using-systemd.html">
2.5.9 Managing MySQL Server with systemd
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="uln-installation.html">
2.6 Installing MySQL Using Unbreakable Linux Network (ULN)
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="solaris-installation.html">
2.7 Installing MySQL on Solaris
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="solaris-installation-pkg.html">
2.7.1 Installing MySQL on Solaris Using a Solaris PKG
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="source-installation.html">
2.8 Installing MySQL from Source
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="source-installation-methods.html">
2.8.1 Source Installation Methods
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="source-installation-prerequisites.html">
2.8.2 Source Installation Prerequisites
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="source-installation-layout.html">
2.8.3 MySQL Layout for Source Installation
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="installing-source-distribution.html">
2.8.4 Installing MySQL Using a Standard Source Distribution
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="installing-development-tree.html">
2.8.5 Installing MySQL Using a Development Source Tree
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="source-ssl-library-configuration.html">
2.8.6 Configuring SSL Library Support
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="source-configuration-options.html">
2.8.7 MySQL Source-Configuration Options
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="compilation-problems.html">
2.8.8 Dealing with Problems Compiling MySQL
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="source-configuration-third-party.html">
2.8.9 MySQL Configuration and Third-Party Tools
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="source-installation-doxygen.html">
2.8.10 Generating MySQL Doxygen Documentation Content
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="postinstallation.html">
2.9 Postinstallation Setup and Testing
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="data-directory-initialization.html">
2.9.1 Initializing the Data Directory
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="starting-server.html">
2.9.2 Starting the Server
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="testing-server.html">
2.9.3 Testing the Server
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="default-privileges.html">
2.9.4 Securing the Initial MySQL Account
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="automatic-start.html">
2.9.5 Starting and Stopping MySQL Automatically
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="perl-support.html">
2.10 Perl Installation Notes
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="perl-installation.html">
2.10.1 Installing Perl on Unix
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="activestate-perl.html">
2.10.2 Installing ActiveState Perl on Windows
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="perl-support-problems.html">
2.10.3 Problems Using the Perl DBI/DBD Interface
</a>
</span>
</dt>
</dl>
</dd>
</dl>
</dd>
<dt>
<span class="chapter">
<a href="upgrading.html">
3 Upgrading MySQL
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="upgrade-before-you-begin.html">
3.1 Before You Begin
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="upgrade-paths.html">
3.2 Upgrade Paths
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="upgrade-best-practices.html">
3.3 Upgrade Best Practices
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="upgrading-what-is-upgraded.html">
3.4 What the MySQL Upgrade Process Upgrades
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="upgrading-from-previous-series.html">
3.5 Changes in MySQL 8.4
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="upgrade-prerequisites.html">
3.6 Preparing Your Installation for Upgrade
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="upgrade-binary-package.html">
3.7 Upgrading MySQL Binary or Package-based Installations on Unix/Linux
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="updating-yum-repo.html">
3.8 Upgrading MySQL with the MySQL Yum Repository
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="updating-apt-repo.html">
3.9 Upgrading MySQL with the MySQL APT Repository
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="updating-sles-repo.html">
3.10 Upgrading MySQL with the MySQL SLES Repository
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="windows-upgrading.html">
3.11 Upgrading MySQL on Windows
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="upgrade-docker-mysql.html">
3.12 Upgrading a Docker Installation of MySQL
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="upgrade-troubleshooting.html">
3.13 Upgrade Troubleshooting
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="rebuilding-tables.html">
3.14 Rebuilding or Repairing Tables or Indexes
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="copying-databases.html">
3.15 Copying MySQL Databases to Another Machine
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="chapter">
<a href="downgrading.html">
4 Downgrading MySQL
</a>
</span>
</dt>
<dt>
<span class="chapter">
<a href="tutorial.html">
5 Tutorial
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="connecting-disconnecting.html">
5.1 Connecting to and Disconnecting from the Server
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="entering-queries.html">
5.2 Entering Queries
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="database-use.html">
5.3 Creating and Using a Database
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="creating-database.html">
5.3.1 Creating and Selecting a Database
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="creating-tables.html">
5.3.2 Creating a Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="loading-tables.html">
5.3.3 Loading Data into a Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="retrieving-data.html">
5.3.4 Retrieving Information from a Table
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="getting-information.html">
5.4 Getting Information About Databases and Tables
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="batch-mode.html">
5.5 Using mysql in Batch Mode
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="examples.html">
5.6 Examples of Common Queries
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="example-maximum-column.html">
5.6.1 The Maximum Value for a Column
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="example-maximum-row.html">
5.6.2 The Row Holding the Maximum of a Certain Column
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="example-maximum-column-group.html">
5.6.3 Maximum of Column per Group
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="example-maximum-column-group-row.html">
5.6.4 The Rows Holding the Group-wise Maximum of a Certain Column
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="example-user-variables.html">
5.6.5 Using User-Defined Variables
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="example-foreign-keys.html">
5.6.6 Using Foreign Keys
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="searching-on-two-keys.html">
5.6.7 Searching on Two Keys
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="calculating-days.html">
5.6.8 Calculating Visits Per Day
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="example-auto-increment.html">
5.6.9 Using AUTO_INCREMENT
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="apache.html">
5.7 Using MySQL with Apache
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="chapter">
<a href="programs.html">
6 MySQL Programs
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="programs-overview.html">
6.1 Overview of MySQL Programs
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="programs-using.html">
6.2 Using MySQL Programs
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="invoking-programs.html">
6.2.1 Invoking MySQL Programs
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="program-options.html">
6.2.2 Specifying Program Options
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="connection-options.html">
6.2.3 Command Options for Connecting to the Server
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="connecting.html">
6.2.4 Connecting to the MySQL Server Using Command Options
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="connecting-using-uri-or-key-value-pairs.html">
6.2.5 Connecting to the Server Using URI-Like Strings or Key-Value Pairs
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="connecting-using-dns-srv.html">
6.2.6 Connecting to the Server Using DNS SRV Records
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="transport-protocols.html">
6.2.7 Connection Transport Protocols
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="connection-compression-control.html">
6.2.8 Connection Compression Control
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="setting-environment-variables.html">
6.2.9 Setting Environment Variables
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="programs-server.html">
6.3 Server and Server-Startup Programs
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="mysqld.html">
6.3.1 mysqld — The MySQL Server
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysqld-safe.html">
6.3.2 mysqld_safe — MySQL Server Startup Script
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-server.html">
6.3.3 mysql.server — MySQL Server Startup Script
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysqld-multi.html">
6.3.4 mysqld_multi — Manage Multiple MySQL Servers
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="programs-installation.html">
6.4 Installation-Related Programs
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="comp-err.html">
6.4.1 comp_err — Compile MySQL Error Message File
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-secure-installation.html">
6.4.2 mysql_secure_installation — Improve MySQL Installation Security
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-tzinfo-to-sql.html">
6.4.3 mysql_tzinfo_to_sql — Load the Time Zone Tables
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="programs-client.html">
6.5 Client Programs
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="mysql.html">
6.5.1 mysql — The MySQL Command-Line Client
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysqladmin.html">
6.5.2 mysqladmin — A MySQL Server Administration Program
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysqlcheck.html">
6.5.3 mysqlcheck — A Table Maintenance Program
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysqldump.html">
6.5.4 mysqldump — A Database Backup Program
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysqlimport.html">
6.5.5 mysqlimport — A Data Import Program
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysqlshow.html">
6.5.6 mysqlshow — Display Database, Table, and Column Information
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysqlslap.html">
6.5.7 mysqlslap — A Load Emulation Client
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="programs-admin-utils.html">
6.6 Administrative and Utility Programs
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="ibd2sdi.html">
6.6.1 ibd2sdi — InnoDB Tablespace SDI Extraction Utility
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="innochecksum.html">
6.6.2 innochecksum — Offline InnoDB File Checksum Utility
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="myisam-ftdump.html">
6.6.3 myisam_ftdump — Display Full-Text Index information
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="myisamchk.html">
6.6.4 myisamchk — MyISAM Table-Maintenance Utility
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="myisamlog.html">
6.6.5 myisamlog — Display MyISAM Log File Contents
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="myisampack.html">
6.6.6 myisampack — Generate Compressed, Read-Only MyISAM Tables
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-config-editor.html">
6.6.7 mysql_config_editor — MySQL Configuration Utility
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-migrate-keyring.html">
6.6.8 mysql_migrate_keyring — Keyring Key Migration Utility
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysqlbinlog.html">
6.6.9 mysqlbinlog — Utility for Processing Binary Log Files
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysqldumpslow.html">
6.6.10 mysqldumpslow — Summarize Slow Query Log Files
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="programs-development.html">
6.7 Program Development Utilities
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="mysql-config.html">
6.7.1 mysql_config — Display Options for Compiling Clients
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="my-print-defaults.html">
6.7.2 my_print_defaults — Display Options from Option Files
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="programs-miscellaneous.html">
6.8 Miscellaneous Programs
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="perror.html">
6.8.1 perror — Display MySQL Error Message Information
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="environment-variables.html">
6.9 Environment Variables
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="unix-signal-response.html">
6.10 Unix Signal Handling in MySQL
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="chapter">
<a href="server-administration.html">
7 MySQL Server Administration
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="mysqld-server.html">
7.1 The MySQL Server
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="server-configuration.html">
7.1.1 Configuring the Server
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="server-configuration-defaults.html">
7.1.2 Server Configuration Defaults
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="server-configuration-validation.html">
7.1.3 Server Configuration Validation
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="server-option-variable-reference.html">
7.1.4 Server Option, System Variable, and Status Variable Reference
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="server-system-variable-reference.html">
7.1.5 Server System Variable Reference
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="server-status-variable-reference.html">
7.1.6 Server Status Variable Reference
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="server-options.html">
7.1.7 Server Command Options
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="server-system-variables.html">
7.1.8 Server System Variables
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="using-system-variables.html">
7.1.9 Using System Variables
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="server-status-variables.html">
7.1.10 Server Status Variables
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="sql-mode.html">
7.1.11 Server SQL Modes
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="connection-management.html">
7.1.12 Connection Management
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="ipv6-support.html">
7.1.13 IPv6 Support
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="network-namespace-support.html">
7.1.14 Network Namespace Support
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="time-zone-support.html">
7.1.15 MySQL Server Time Zone Support
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="resource-groups.html">
7.1.16 Resource Groups
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="server-side-help-support.html">
7.1.17 Server-Side Help Support
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="session-state-tracking.html">
7.1.18 Server Tracking of Client Session State
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="server-shutdown.html">
7.1.19 The Server Shutdown Process
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="data-directory.html">
7.2 The MySQL Data Directory
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="system-schema.html">
7.3 The mysql System Schema
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="server-logs.html">
7.4 MySQL Server Logs
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="log-destinations.html">
7.4.1 Selecting General Query Log and Slow Query Log Output Destinations
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="error-log.html">
7.4.2 The Error Log
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="query-log.html">
7.4.3 The General Query Log
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="binary-log.html">
7.4.4 The Binary Log
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="slow-query-log.html">
7.4.5 The Slow Query Log
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="log-file-maintenance.html">
7.4.6 Server Log Maintenance
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="components.html">
7.5 MySQL Components
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="component-loading.html">
7.5.1 Installing and Uninstalling Components
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="obtaining-component-information.html">
7.5.2 Obtaining Component Information
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="error-log-components.html">
7.5.3 Error Log Components
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="query-attribute-components.html">
7.5.4 Query Attribute Components
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="scheduler-component.html">
7.5.5 Scheduler Component
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="server-plugins.html">
7.6 MySQL Server Plugins
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="plugin-loading.html">
7.6.1 Installing and Uninstalling Plugins
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="obtaining-plugin-information.html">
7.6.2 Obtaining Server Plugin Information
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="thread-pool.html">
7.6.3 MySQL Enterprise Thread Pool
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="rewriter-query-rewrite-plugin.html">
7.6.4 The Rewriter Query Rewrite Plugin
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="ddl-rewriter.html">
7.6.5 The ddl_rewriter Plugin
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="version-tokens.html">
7.6.6 Version Tokens
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="clone-plugin.html">
7.6.7 The Clone Plugin
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="daemon-keyring-proxy-plugin.html">
7.6.8 The Keyring Proxy Bridge Plugin
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="plugin-services.html">
7.6.9 MySQL Plugin Services
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="server-loadable-functions.html">
7.7 MySQL Server Loadable Functions
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="function-loading.html">
7.7.1 Installing and Uninstalling Loadable Functions
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="obtaining-loadable-function-information.html">
7.7.2 Obtaining Information About Loadable Functions
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="multiple-servers.html">
7.8 Running Multiple MySQL Instances on One Machine
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="multiple-data-directories.html">
7.8.1 Setting Up Multiple Data Directories
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="multiple-windows-servers.html">
7.8.2 Running Multiple MySQL Instances on Windows
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="multiple-unix-servers.html">
7.8.3 Running Multiple MySQL Instances on Unix
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="multiple-server-clients.html">
7.8.4 Using Client Programs in a Multiple-Server Environment
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="debugging-mysql.html">
7.9 Debugging MySQL
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="debugging-server.html">
7.9.1 Debugging a MySQL Server
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="debugging-client.html">
7.9.2 Debugging a MySQL Client
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="lock-order-tool.html">
7.9.3 The LOCK_ORDER Tool
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="dbug-package.html">
7.9.4 The DBUG Package
</a>
</span>
</dt>
</dl>
</dd>
</dl>
</dd>
<dt>
<span class="chapter">
<a href="security.html">
8 Security
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="general-security-issues.html">
8.1 General Security Issues
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="security-guidelines.html">
8.1.1 Security Guidelines
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="password-security.html">
8.1.2 Keeping Passwords Secure
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="security-against-attack.html">
8.1.3 Making MySQL Secure Against Attackers
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="security-options.html">
8.1.4 Security-Related mysqld Options and Variables
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="changing-mysql-user.html">
8.1.5 How to Run MySQL as a Normal User
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="load-data-local-security.html">
8.1.6 Security Considerations for LOAD DATA LOCAL
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="secure-client-programming.html">
8.1.7 Client Programming Security Guidelines
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="access-control.html">
8.2 Access Control and Account Management
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="user-names.html">
8.2.1 Account User Names and Passwords
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="privileges-provided.html">
8.2.2 Privileges Provided by MySQL
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="grant-tables.html">
8.2.3 Grant Tables
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="account-names.html">
8.2.4 Specifying Account Names
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="role-names.html">
8.2.5 Specifying Role Names
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="connection-access.html">
8.2.6 Access Control, Stage 1: Connection Verification
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="request-access.html">
8.2.7 Access Control, Stage 2: Request Verification
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="creating-accounts.html">
8.2.8 Adding Accounts, Assigning Privileges, and Dropping Accounts
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="reserved-accounts.html">
8.2.9 Reserved Accounts
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="roles.html">
8.2.10 Using Roles
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="account-categories.html">
8.2.11 Account Categories
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="partial-revokes.html">
8.2.12 Privilege Restriction Using Partial Revokes
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="privilege-changes.html">
8.2.13 When Privilege Changes Take Effect
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="assigning-passwords.html">
8.2.14 Assigning Account Passwords
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="password-management.html">
8.2.15 Password Management
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="expired-password-handling.html">
8.2.16 Server Handling of Expired Passwords
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="pluggable-authentication.html">
8.2.17 Pluggable Authentication
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="multifactor-authentication.html">
8.2.18 Multifactor Authentication
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="proxy-users.html">
8.2.19 Proxy Users
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="account-locking.html">
8.2.20 Account Locking
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="user-resources.html">
8.2.21 Setting Account Resource Limits
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="problems-connecting.html">
8.2.22 Troubleshooting Problems Connecting to MySQL
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="account-activity-auditing.html">
8.2.23 SQL-Based Account Activity Auditing
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="encrypted-connections.html">
8.3 Using Encrypted Connections
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="using-encrypted-connections.html">
8.3.1 Configuring MySQL to Use Encrypted Connections
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="encrypted-connection-protocols-ciphers.html">
8.3.2 Encrypted Connection TLS Protocols and Ciphers
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="creating-ssl-rsa-files.html">
8.3.3 Creating SSL and RSA Certificates and Keys
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="windows-and-ssh.html">
8.3.4 Connecting to MySQL Remotely from Windows with SSH
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="reusing-ssl-sessions.html">
8.3.5 Reusing SSL Sessions
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="security-plugins.html">
8.4 Security Components and Plugins
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="authentication-plugins.html">
8.4.1 Authentication Plugins
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="connection-control.html">
8.4.2 The Connection-Control Plugins
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="validate-password.html">
8.4.3 The Password Validation Component
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="keyring.html">
8.4.4 The MySQL Keyring
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="audit-log.html">
8.4.5 MySQL Enterprise Audit
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="audit-api-message-emit.html">
8.4.6 The Audit Message Component
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="firewall.html">
8.4.7 MySQL Enterprise Firewall
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="data-masking.html">
8.5 MySQL Enterprise Data Masking and De-Identification
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="data-masking-components-vs-plugin.html">
8.5.1 Data-Masking Components Versus the Data-Masking Plugin
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="data-masking-components.html">
8.5.2 MySQL Enterprise Data Masking and De-Identification Components
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="data-masking-plugin.html">
8.5.3 MySQL Enterprise Data Masking and De-Identification Plugin
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="enterprise-encryption.html">
8.6 MySQL Enterprise Encryption
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="enterprise-encryption-installation.html">
8.6.1 MySQL Enterprise Encryption Installation and Upgrading
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="enterprise-encryption-configuring.html">
8.6.2 Configuring MySQL Enterprise Encryption
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="enterprise-encryption-usage.html">
8.6.3 MySQL Enterprise Encryption Usage and Examples
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="enterprise-encryption-function-reference.html">
8.6.4 MySQL Enterprise Encryption Function Reference
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="enterprise-encryption-functions.html">
8.6.5 MySQL Enterprise Encryption Component Function Descriptions
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="selinux.html">
8.7 SELinux
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="selinux-checking.html">
8.7.1 Check if SELinux is Enabled
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="selinux-mode.html">
8.7.2 Changing the SELinux Mode
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="selinux-policies.html">
8.7.3 MySQL Server SELinux Policies
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="selinux-file-context.html">
8.7.4 SELinux File Context
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="selinux-context-tcp-port.html">
8.7.5 SELinux TCP Port Context
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="selinux-troubleshooting.html">
8.7.6 Troubleshooting SELinux
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="fips-mode.html">
8.8 FIPS Support
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="chapter">
<a href="backup-and-recovery.html">
9 Backup and Recovery
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="backup-types.html">
9.1 Backup and Recovery Types
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="backup-methods.html">
9.2 Database Backup Methods
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="backup-strategy-example.html">
9.3 Example Backup and Recovery Strategy
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="backup-policy.html">
9.3.1 Establishing a Backup Policy
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="recovery-from-backups.html">
9.3.2 Using Backups for Recovery
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="backup-strategy-summary.html">
9.3.3 Backup Strategy Summary
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="using-mysqldump.html">
9.4 Using mysqldump for Backups
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="mysqldump-sql-format.html">
9.4.1 Dumping Data in SQL Format with mysqldump
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="reloading-sql-format-dumps.html">
9.4.2 Reloading SQL-Format Backups
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysqldump-delimited-text.html">
9.4.3 Dumping Data in Delimited-Text Format with mysqldump
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="reloading-delimited-text-dumps.html">
9.4.4 Reloading Delimited-Text Format Backups
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysqldump-tips.html">
9.4.5 mysqldump Tips
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="point-in-time-recovery.html">
9.5 Point-in-Time (Incremental) Recovery
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="point-in-time-recovery-binlog.html">
9.5.1 Point-in-Time Recovery Using Binary Log
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="point-in-time-recovery-positions.html">
9.5.2 Point-in-Time Recovery Using Event Positions
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="myisam-table-maintenance.html">
9.6 MyISAM Table Maintenance and Crash Recovery
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="myisam-crash-recovery.html">
9.6.1 Using myisamchk for Crash Recovery
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="myisam-check.html">
9.6.2 How to Check MyISAM Tables for Errors
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="myisam-repair.html">
9.6.3 How to Repair MyISAM Tables
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="myisam-optimization.html">
9.6.4 MyISAM Table Optimization
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="myisam-maintenance-schedule.html">
9.6.5 Setting Up a MyISAM Table Maintenance Schedule
</a>
</span>
</dt>
</dl>
</dd>
</dl>
</dd>
<dt>
<span class="chapter">
<a href="optimization.html">
10 Optimization
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="optimize-overview.html">
10.1 Optimization Overview
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="statement-optimization.html">
10.2 Optimizing SQL Statements
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="select-optimization.html">
10.2.1 Optimizing SELECT Statements
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="subquery-optimization.html">
10.2.2 Optimizing Subqueries, Derived Tables, View References, and Common Table
Expressions
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="information-schema-optimization.html">
10.2.3 Optimizing INFORMATION_SCHEMA Queries
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="performance-schema-optimization.html">
10.2.4 Optimizing Performance Schema Queries
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="data-change-optimization.html">
10.2.5 Optimizing Data Change Statements
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="permission-optimization.html">
10.2.6 Optimizing Database Privileges
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="miscellaneous-optimization-tips.html">
10.2.7 Other Optimization Tips
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="optimization-indexes.html">
10.3 Optimization and Indexes
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="mysql-indexes.html">
10.3.1 How MySQL Uses Indexes
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="primary-key-optimization.html">
10.3.2 Primary Key Optimization
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="spatial-index-optimization.html">
10.3.3 SPATIAL Index Optimization
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="foreign-key-optimization.html">
10.3.4 Foreign Key Optimization
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="column-indexes.html">
10.3.5 Column Indexes
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="multiple-column-indexes.html">
10.3.6 Multiple-Column Indexes
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="verifying-index-usage.html">
10.3.7 Verifying Index Usage
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="index-statistics.html">
10.3.8 InnoDB and MyISAM Index Statistics Collection
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="index-btree-hash.html">
10.3.9 Comparison of B-Tree and Hash Indexes
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="index-extensions.html">
10.3.10 Use of Index Extensions
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="generated-column-index-optimizations.html">
10.3.11 Optimizer Use of Generated Column Indexes
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="invisible-indexes.html">
10.3.12 Invisible Indexes
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="descending-indexes.html">
10.3.13 Descending Indexes
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="timestamp-lookups.html">
10.3.14 Indexed Lookups from TIMESTAMP Columns
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="optimizing-database-structure.html">
10.4 Optimizing Database Structure
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="data-size.html">
10.4.1 Optimizing Data Size
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="optimize-data-types.html">
10.4.2 Optimizing MySQL Data Types
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="optimize-multi-tables.html">
10.4.3 Optimizing for Many Tables
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="internal-temporary-tables.html">
10.4.4 Internal Temporary Table Use in MySQL
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="database-count-limit.html">
10.4.5 Limits on Number of Databases and Tables
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="table-size-limit.html">
10.4.6 Limits on Table Size
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="column-count-limit.html">
10.4.7 Limits on Table Column Count and Row Size
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="optimizing-innodb.html">
10.5 Optimizing for InnoDB Tables
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="optimizing-innodb-storage-layout.html">
10.5.1 Optimizing Storage Layout for InnoDB Tables
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="optimizing-innodb-transaction-management.html">
10.5.2 Optimizing InnoDB Transaction Management
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="innodb-performance-ro-txn.html">
10.5.3 Optimizing InnoDB Read-Only Transactions
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="optimizing-innodb-logging.html">
10.5.4 Optimizing InnoDB Redo Logging
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="optimizing-innodb-bulk-data-loading.html">
10.5.5 Bulk Data Loading for InnoDB Tables
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="optimizing-innodb-queries.html">
10.5.6 Optimizing InnoDB Queries
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="optimizing-innodb-ddl-operations.html">
10.5.7 Optimizing InnoDB DDL Operations
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="optimizing-innodb-diskio.html">
10.5.8 Optimizing InnoDB Disk I/O
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="optimizing-innodb-configuration-variables.html">
10.5.9 Optimizing InnoDB Configuration Variables
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="optimizing-innodb-many-tables.html">
10.5.10 Optimizing InnoDB for Systems with Many Tables
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="optimizing-myisam.html">
10.6 Optimizing for MyISAM Tables
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="optimizing-queries-myisam.html">
10.6.1 Optimizing MyISAM Queries
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="optimizing-myisam-bulk-data-loading.html">
10.6.2 Bulk Data Loading for MyISAM Tables
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="repair-table-optimization.html">
10.6.3 Optimizing REPAIR TABLE Statements
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="optimizing-memory-tables.html">
10.7 Optimizing for MEMORY Tables
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="execution-plan-information.html">
10.8 Understanding the Query Execution Plan
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="using-explain.html">
10.8.1 Optimizing Queries with EXPLAIN
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="explain-output.html">
10.8.2 EXPLAIN Output Format
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="explain-extended.html">
10.8.3 Extended EXPLAIN Output Format
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="explain-for-connection.html">
10.8.4 Obtaining Execution Plan Information for a Named Connection
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="estimating-performance.html">
10.8.5 Estimating Query Performance
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="controlling-optimizer.html">
10.9 Controlling the Query Optimizer
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="controlling-query-plan-evaluation.html">
10.9.1 Controlling Query Plan Evaluation
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="switchable-optimizations.html">
10.9.2 Switchable Optimizations
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="optimizer-hints.html">
10.9.3 Optimizer Hints
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="index-hints.html">
10.9.4 Index Hints
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="cost-model.html">
10.9.5 The Optimizer Cost Model
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="optimizer-statistics.html">
10.9.6 Optimizer Statistics
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="buffering-caching.html">
10.10 Buffering and Caching
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="innodb-buffer-pool-optimization.html">
10.10.1 InnoDB Buffer Pool Optimization
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="myisam-key-cache.html">
10.10.2 The MyISAM Key Cache
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="statement-caching.html">
10.10.3 Caching of Prepared Statements and Stored Programs
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="locking-issues.html">
10.11 Optimizing Locking Operations
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="internal-locking.html">
10.11.1 Internal Locking Methods
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="table-locking.html">
10.11.2 Table Locking Issues
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="concurrent-inserts.html">
10.11.3 Concurrent Inserts
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="metadata-locking.html">
10.11.4 Metadata Locking
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="external-locking.html">
10.11.5 External Locking
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="optimizing-server.html">
10.12 Optimizing the MySQL Server
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="disk-issues.html">
10.12.1 Optimizing Disk I/O
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="symbolic-links.html">
10.12.2 Using Symbolic Links
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="optimizing-memory.html">
10.12.3 Optimizing Memory Use
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="optimize-benchmarking.html">
10.13 Measuring Performance (Benchmarking)
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="select-benchmarking.html">
10.13.1 Measuring the Speed of Expressions and Functions
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="custom-benchmarks.html">
10.13.2 Using Your Own Benchmarks
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="monitoring-performance-schema.html">
10.13.3 Measuring Performance with performance_schema
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="thread-information.html">
10.14 Examining Server Thread (Process) Information
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="processlist-access.html">
10.14.1 Accessing the Process List
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="thread-commands.html">
10.14.2 Thread Command Values
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="general-thread-states.html">
10.14.3 General Thread States
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="source-thread-states.html">
10.14.4 Replication Source Thread States
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="replica-io-thread-states.html">
10.14.5 Replication I/O (Receiver) Thread States
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="replica-sql-thread-states.html">
10.14.6 Replication SQL Thread States
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="replica-connection-thread-states.html">
10.14.7 Replication Connection Thread States
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-thread-states.html">
10.14.8 NDB Cluster Thread States
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="event-scheduler-thread-states.html">
10.14.9 Event Scheduler Thread States
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="optimizer-tracing.html">
10.15 Tracing the Optimizer
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="optimizer-tracing-typical-usage.html">
10.15.1 Typical Usage
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="system-variables-controlling-tracing.html">
10.15.2 System Variables Controlling Tracing
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="traceable-statements.html">
10.15.3 Traceable Statements
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="tuning-trace-purging.html">
10.15.4 Tuning Trace Purging
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="tracing-memory-usage.html">
10.15.5 Tracing Memory Usage
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="privilege-checking.html">
10.15.6 Privilege Checking
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="interaction-with-debug-option.html">
10.15.7 Interaction with the --debug Option
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="optimizer-trace-system-variable.html">
10.15.8 The optimizer_trace System Variable
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="end-markers-in-json-system-variable.html">
10.15.9 The end_markers_in_json System Variable
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="optimizer-features-to-trace.html">
10.15.10 Selecting Optimizer Features to Trace
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="trace-general-structure.html">
10.15.11 Trace General Structure
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="tracing-example.html">
10.15.12 Example
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="displaying-traces.html">
10.15.13 Displaying Traces in Other Applications
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="preventing-use-of-optimizer-trace.html">
10.15.14 Preventing the Use of Optimizer Trace
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="optimizer-trace-testing.html">
10.15.15 Testing Optimizer Trace
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="optimizer-trace-implementation.html">
10.15.16 Optimizer Trace Implementation
</a>
</span>
</dt>
</dl>
</dd>
</dl>
</dd>
<dt>
<span class="chapter">
<a href="language-structure.html">
11 Language Structure
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="literals.html">
11.1 Literal Values
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="string-literals.html">
11.1.1 String Literals
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="number-literals.html">
11.1.2 Numeric Literals
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="date-and-time-literals.html">
11.1.3 Date and Time Literals
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="hexadecimal-literals.html">
11.1.4 Hexadecimal Literals
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="bit-value-literals.html">
11.1.5 Bit-Value Literals
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="boolean-literals.html">
11.1.6 Boolean Literals
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="null-values.html">
11.1.7 NULL Values
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="identifiers.html">
11.2 Schema Object Names
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="identifier-length.html">
11.2.1 Identifier Length Limits
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="identifier-qualifiers.html">
11.2.2 Identifier Qualifiers
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="identifier-case-sensitivity.html">
11.2.3 Identifier Case Sensitivity
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="identifier-mapping.html">
11.2.4 Mapping of Identifiers to File Names
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="function-resolution.html">
11.2.5 Function Name Parsing and Resolution
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="keywords.html">
11.3 Keywords and Reserved Words
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="user-variables.html">
11.4 User-Defined Variables
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="expressions.html">
11.5 Expressions
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="query-attributes.html">
11.6 Query Attributes
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="comments.html">
11.7 Comments
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="chapter">
<a href="charset.html">
12 Character Sets, Collations, Unicode
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="charset-general.html">
12.1 Character Sets and Collations in General
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="charset-mysql.html">
12.2 Character Sets and Collations in MySQL
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="charset-repertoire.html">
12.2.1 Character Set Repertoire
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="charset-metadata.html">
12.2.2 UTF-8 for Metadata
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="charset-syntax.html">
12.3 Specifying Character Sets and Collations
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="charset-collation-names.html">
12.3.1 Collation Naming Conventions
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="charset-server.html">
12.3.2 Server Character Set and Collation
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="charset-database.html">
12.3.3 Database Character Set and Collation
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="charset-table.html">
12.3.4 Table Character Set and Collation
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="charset-column.html">
12.3.5 Column Character Set and Collation
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="charset-literal.html">
12.3.6 Character String Literal Character Set and Collation
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="charset-national.html">
12.3.7 The National Character Set
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="charset-introducer.html">
12.3.8 Character Set Introducers
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="charset-examples.html">
12.3.9 Examples of Character Set and Collation Assignment
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="charset-compatibility.html">
12.3.10 Compatibility with Other DBMSs
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="charset-connection.html">
12.4 Connection Character Sets and Collations
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="charset-applications.html">
12.5 Configuring Application Character Set and Collation
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="charset-errors.html">
12.6 Error Message Character Set
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="charset-conversion.html">
12.7 Column Character Set Conversion
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="charset-collations.html">
12.8 Collation Issues
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="charset-collate.html">
12.8.1 Using COLLATE in SQL Statements
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="charset-collate-precedence.html">
12.8.2 COLLATE Clause Precedence
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="charset-collation-compatibility.html">
12.8.3 Character Set and Collation Compatibility
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="charset-collation-coercibility.html">
12.8.4 Collation Coercibility in Expressions
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="charset-binary-collations.html">
12.8.5 The binary Collation Compared to _bin Collations
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="charset-collation-effect.html">
12.8.6 Examples of the Effect of Collation
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="charset-collation-information-schema.html">
12.8.7 Using Collation in INFORMATION_SCHEMA Searches
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="charset-unicode.html">
12.9 Unicode Support
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="charset-unicode-utf8mb4.html">
12.9.1 The utf8mb4 Character Set (4-Byte UTF-8 Unicode Encoding)
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="charset-unicode-utf8mb3.html">
12.9.2 The utf8mb3 Character Set (3-Byte UTF-8 Unicode Encoding)
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="charset-unicode-utf8.html">
12.9.3 The utf8 Character Set (Deprecated alias for utf8mb3)
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="charset-unicode-ucs2.html">
12.9.4 The ucs2 Character Set (UCS-2 Unicode Encoding)
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="charset-unicode-utf16.html">
12.9.5 The utf16 Character Set (UTF-16 Unicode Encoding)
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="charset-unicode-utf16le.html">
12.9.6 The utf16le Character Set (UTF-16LE Unicode Encoding)
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="charset-unicode-utf32.html">
12.9.7 The utf32 Character Set (UTF-32 Unicode Encoding)
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="charset-unicode-conversion.html">
12.9.8 Converting Between 3-Byte and 4-Byte Unicode Character Sets
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="charset-charsets.html">
12.10 Supported Character Sets and Collations
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="charset-unicode-sets.html">
12.10.1 Unicode Character Sets
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="charset-we-sets.html">
12.10.2 West European Character Sets
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="charset-ce-sets.html">
12.10.3 Central European Character Sets
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="charset-se-me-sets.html">
12.10.4 South European and Middle East Character Sets
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="charset-baltic-sets.html">
12.10.5 Baltic Character Sets
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="charset-cyrillic-sets.html">
12.10.6 Cyrillic Character Sets
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="charset-asian-sets.html">
12.10.7 Asian Character Sets
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="charset-binary-set.html">
12.10.8 The Binary Character Set
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="charset-restrictions.html">
12.11 Restrictions on Character Sets
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="error-message-language.html">
12.12 Setting the Error Message Language
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="adding-character-set.html">
12.13 Adding a Character Set
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="character-arrays.html">
12.13.1 Character Definition Arrays
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="string-collating.html">
12.13.2 String Collating Support for Complex Character Sets
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="multibyte-characters.html">
12.13.3 Multi-Byte Character Support for Complex Character Sets
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="adding-collation.html">
12.14 Adding a Collation to a Character Set
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="charset-collation-implementations.html">
12.14.1 Collation Implementation Types
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="adding-collation-choosing-id.html">
12.14.2 Choosing a Collation ID
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="adding-collation-simple-8bit.html">
12.14.3 Adding a Simple Collation to an 8-Bit Character Set
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="adding-collation-unicode-uca.html">
12.14.4 Adding a UCA Collation to a Unicode Character Set
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="charset-configuration.html">
12.15 Character Set Configuration
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="locale-support.html">
12.16 MySQL Server Locale Support
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="chapter">
<a href="data-types.html">
13 Data Types
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="numeric-types.html">
13.1 Numeric Data Types
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="numeric-type-syntax.html">
13.1.1 Numeric Data Type Syntax
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="integer-types.html">
13.1.2 Integer Types (Exact Value) - INTEGER, INT, SMALLINT, TINYINT,
MEDIUMINT, BIGINT
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="fixed-point-types.html">
13.1.3 Fixed-Point Types (Exact Value) - DECIMAL, NUMERIC
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="floating-point-types.html">
13.1.4 Floating-Point Types (Approximate Value) - FLOAT, DOUBLE
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="bit-type.html">
13.1.5 Bit-Value Type - BIT
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="numeric-type-attributes.html">
13.1.6 Numeric Type Attributes
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="out-of-range-and-overflow.html">
13.1.7 Out-of-Range and Overflow Handling
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="date-and-time-types.html">
13.2 Date and Time Data Types
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="date-and-time-type-syntax.html">
13.2.1 Date and Time Data Type Syntax
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="datetime.html">
13.2.2 The DATE, DATETIME, and TIMESTAMP Types
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="time.html">
13.2.3 The TIME Type
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="year.html">
13.2.4 The YEAR Type
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="timestamp-initialization.html">
13.2.5 Automatic Initialization and Updating for TIMESTAMP and DATETIME
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="fractional-seconds.html">
13.2.6 Fractional Seconds in Time Values
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-calendar.html">
13.2.7 What Calendar Is Used By MySQL?
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="date-and-time-type-conversion.html">
13.2.8 Conversion Between Date and Time Types
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="two-digit-years.html">
13.2.9 2-Digit Years in Dates
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="string-types.html">
13.3 String Data Types
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="string-type-syntax.html">
13.3.1 String Data Type Syntax
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="char.html">
13.3.2 The CHAR and VARCHAR Types
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="binary-varbinary.html">
13.3.3 The BINARY and VARBINARY Types
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="blob.html">
13.3.4 The BLOB and TEXT Types
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="enum.html">
13.3.5 The ENUM Type
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="set.html">
13.3.6 The SET Type
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="spatial-types.html">
13.4 Spatial Data Types
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="spatial-type-overview.html">
13.4.1 Spatial Data Types
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="opengis-geometry-model.html">
13.4.2 The OpenGIS Geometry Model
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="gis-data-formats.html">
13.4.3 Supported Spatial Data Formats
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="geometry-well-formedness-validity.html">
13.4.4 Geometry Well-Formedness and Validity
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="spatial-reference-systems.html">
13.4.5 Spatial Reference System Support
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="creating-spatial-columns.html">
13.4.6 Creating Spatial Columns
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="populating-spatial-columns.html">
13.4.7 Populating Spatial Columns
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="fetching-spatial-data.html">
13.4.8 Fetching Spatial Data
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="optimizing-spatial-analysis.html">
13.4.9 Optimizing Spatial Analysis
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="creating-spatial-indexes.html">
13.4.10 Creating Spatial Indexes
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="using-spatial-indexes.html">
13.4.11 Using Spatial Indexes
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="json.html">
13.5 The JSON Data Type
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="data-type-defaults.html">
13.6 Data Type Default Values
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="storage-requirements.html">
13.7 Data Type Storage Requirements
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="choosing-types.html">
13.8 Choosing the Right Type for a Column
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="other-vendor-data-types.html">
13.9 Using Data Types from Other Database Engines
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="chapter">
<a href="functions.html">
14 Functions and Operators
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="built-in-function-reference.html">
14.1 Built-In Function and Operator Reference
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="loadable-function-reference.html">
14.2 Loadable Function Reference
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="type-conversion.html">
14.3 Type Conversion in Expression Evaluation
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="non-typed-operators.html">
14.4 Operators
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="operator-precedence.html">
14.4.1 Operator Precedence
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="comparison-operators.html">
14.4.2 Comparison Functions and Operators
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="logical-operators.html">
14.4.3 Logical Operators
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="assignment-operators.html">
14.4.4 Assignment Operators
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="flow-control-functions.html">
14.5 Flow Control Functions
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="numeric-functions.html">
14.6 Numeric Functions and Operators
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="arithmetic-functions.html">
14.6.1 Arithmetic Operators
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mathematical-functions.html">
14.6.2 Mathematical Functions
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="date-and-time-functions.html">
14.7 Date and Time Functions
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="string-functions.html">
14.8 String Functions and Operators
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="string-comparison-functions.html">
14.8.1 String Comparison Functions and Operators
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="regexp.html">
14.8.2 Regular Expressions
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="string-functions-charset.html">
14.8.3 Character Set and Collation of Function Results
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="fulltext-search.html">
14.9 Full-Text Search Functions
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="fulltext-natural-language.html">
14.9.1 Natural Language Full-Text Searches
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="fulltext-boolean.html">
14.9.2 Boolean Full-Text Searches
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="fulltext-query-expansion.html">
14.9.3 Full-Text Searches with Query Expansion
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="fulltext-stopwords.html">
14.9.4 Full-Text Stopwords
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="fulltext-restrictions.html">
14.9.5 Full-Text Restrictions
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="fulltext-fine-tuning.html">
14.9.6 Fine-Tuning MySQL Full-Text Search
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="full-text-adding-collation.html">
14.9.7 Adding a User-Defined Collation for Full-Text Indexing
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="fulltext-search-ngram.html">
14.9.8 ngram Full-Text Parser
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="fulltext-search-mecab.html">
14.9.9 MeCab Full-Text Parser Plugin
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="cast-functions.html">
14.10 Cast Functions and Operators
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="xml-functions.html">
14.11 XML Functions
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="bit-functions.html">
14.12 Bit Functions and Operators
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="encryption-functions.html">
14.13 Encryption and Compression Functions
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="locking-functions.html">
14.14 Locking Functions
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="information-functions.html">
14.15 Information Functions
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="spatial-analysis-functions.html">
14.16 Spatial Analysis Functions
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="spatial-function-reference.html">
14.16.1 Spatial Function Reference
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="spatial-function-argument-handling.html">
14.16.2 Argument Handling by Spatial Functions
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="gis-wkt-functions.html">
14.16.3 Functions That Create Geometry Values from WKT Values
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="gis-wkb-functions.html">
14.16.4 Functions That Create Geometry Values from WKB Values
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="gis-mysql-specific-functions.html">
14.16.5 MySQL-Specific Functions That Create Geometry Values
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="gis-format-conversion-functions.html">
14.16.6 Geometry Format Conversion Functions
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="gis-property-functions.html">
14.16.7 Geometry Property Functions
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="spatial-operator-functions.html">
14.16.8 Spatial Operator Functions
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="spatial-relation-functions.html">
14.16.9 Functions That Test Spatial Relations Between Geometry Objects
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="spatial-geohash-functions.html">
14.16.10 Spatial Geohash Functions
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="spatial-geojson-functions.html">
14.16.11 Spatial GeoJSON Functions
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="spatial-aggregate-functions.html">
14.16.12 Spatial Aggregate Functions
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="spatial-convenience-functions.html">
14.16.13 Spatial Convenience Functions
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="json-functions.html">
14.17 JSON Functions
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="json-function-reference.html">
14.17.1 JSON Function Reference
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="json-creation-functions.html">
14.17.2 Functions That Create JSON Values
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="json-search-functions.html">
14.17.3 Functions That Search JSON Values
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="json-modification-functions.html">
14.17.4 Functions That Modify JSON Values
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="json-attribute-functions.html">
14.17.5 Functions That Return JSON Value Attributes
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="json-table-functions.html">
14.17.6 JSON Table Functions
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="json-validation-functions.html">
14.17.7 JSON Schema Validation Functions
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="json-utility-functions.html">
14.17.8 JSON Utility Functions
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="replication-functions.html">
14.18 Replication Functions
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="group-replication-functions.html">
14.18.1 Group Replication Functions
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="gtid-functions.html">
14.18.2 Functions Used with Global Transaction Identifiers (GTIDs)
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="replication-functions-async-failover.html">
14.18.3 Asynchronous Replication Channel Failover Functions
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="replication-functions-synchronization.html">
14.18.4 Position-Based Synchronization Functions
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="aggregate-functions-and-modifiers.html">
14.19 Aggregate Functions
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="aggregate-functions.html">
14.19.1 Aggregate Function Descriptions
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="group-by-modifiers.html">
14.19.2 GROUP BY Modifiers
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="group-by-handling.html">
14.19.3 MySQL Handling of GROUP BY
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="group-by-functional-dependence.html">
14.19.4 Detection of Functional Dependence
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="window-functions.html">
14.20 Window Functions
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="window-function-descriptions.html">
14.20.1 Window Function Descriptions
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="window-functions-usage.html">
14.20.2 Window Function Concepts and Syntax
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="window-functions-frames.html">
14.20.3 Window Function Frame Specification
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="window-functions-named-windows.html">
14.20.4 Named Windows
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="window-function-restrictions.html">
14.20.5 Window Function Restrictions
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="performance-schema-functions.html">
14.21 Performance Schema Functions
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="internal-functions.html">
14.22 Internal Functions
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="miscellaneous-functions.html">
14.23 Miscellaneous Functions
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="precision-math.html">
14.24 Precision Math
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="precision-math-numbers.html">
14.24.1 Types of Numeric Values
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="precision-math-decimal-characteristics.html">
14.24.2 DECIMAL Data Type Characteristics
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="precision-math-expressions.html">
14.24.3 Expression Handling
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="precision-math-rounding.html">
14.24.4 Rounding Behavior
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="precision-math-examples.html">
14.24.5 Precision Math Examples
</a>
</span>
</dt>
</dl>
</dd>
</dl>
</dd>
<dt>
<span class="chapter">
<a href="sql-statements.html">
15 SQL Statements
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="sql-data-definition-statements.html">
15.1 Data Definition Statements
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="atomic-ddl.html">
15.1.1 Atomic Data Definition Statement Support
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="alter-database.html">
15.1.2 ALTER DATABASE Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="alter-event.html">
15.1.3 ALTER EVENT Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="alter-function.html">
15.1.4 ALTER FUNCTION Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="alter-instance.html">
15.1.5 ALTER INSTANCE Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="alter-logfile-group.html">
15.1.6 ALTER LOGFILE GROUP Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="alter-procedure.html">
15.1.7 ALTER PROCEDURE Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="alter-server.html">
15.1.8 ALTER SERVER Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="alter-table.html">
15.1.9 ALTER TABLE Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="alter-tablespace.html">
15.1.10 ALTER TABLESPACE Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="alter-view.html">
15.1.11 ALTER VIEW Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="create-database.html">
15.1.12 CREATE DATABASE Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="create-event.html">
15.1.13 CREATE EVENT Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="create-function.html">
15.1.14 CREATE FUNCTION Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="create-index.html">
15.1.15 CREATE INDEX Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="create-logfile-group.html">
15.1.16 CREATE LOGFILE GROUP Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="create-procedure.html">
15.1.17 CREATE PROCEDURE and CREATE FUNCTION Statements
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="create-server.html">
15.1.18 CREATE SERVER Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="create-spatial-reference-system.html">
15.1.19 CREATE SPATIAL REFERENCE SYSTEM Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="create-table.html">
15.1.20 CREATE TABLE Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="create-tablespace.html">
15.1.21 CREATE TABLESPACE Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="create-trigger.html">
15.1.22 CREATE TRIGGER Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="create-view.html">
15.1.23 CREATE VIEW Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="drop-database.html">
15.1.24 DROP DATABASE Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="drop-event.html">
15.1.25 DROP EVENT Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="drop-function.html">
15.1.26 DROP FUNCTION Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="drop-index.html">
15.1.27 DROP INDEX Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="drop-logfile-group.html">
15.1.28 DROP LOGFILE GROUP Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="drop-procedure.html">
15.1.29 DROP PROCEDURE and DROP FUNCTION Statements
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="drop-server.html">
15.1.30 DROP SERVER Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="drop-spatial-reference-system.html">
15.1.31 DROP SPATIAL REFERENCE SYSTEM Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="drop-table.html">
15.1.32 DROP TABLE Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="drop-tablespace.html">
15.1.33 DROP TABLESPACE Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="drop-trigger.html">
15.1.34 DROP TRIGGER Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="drop-view.html">
15.1.35 DROP VIEW Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="rename-table.html">
15.1.36 RENAME TABLE Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="truncate-table.html">
15.1.37 TRUNCATE TABLE Statement
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="sql-data-manipulation-statements.html">
15.2 Data Manipulation Statements
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="call.html">
15.2.1 CALL Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="delete.html">
15.2.2 DELETE Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="do.html">
15.2.3 DO Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="except.html">
15.2.4 EXCEPT Clause
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="handler.html">
15.2.5 HANDLER Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="import-table.html">
15.2.6 IMPORT TABLE Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="insert.html">
15.2.7 INSERT Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="intersect.html">
15.2.8 INTERSECT Clause
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="load-data.html">
15.2.9 LOAD DATA Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="load-xml.html">
15.2.10 LOAD XML Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="parenthesized-query-expressions.html">
15.2.11 Parenthesized Query Expressions
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="replace.html">
15.2.12 REPLACE Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="select.html">
15.2.13 SELECT Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="set-operations.html">
15.2.14 Set Operations with UNION, INTERSECT, and EXCEPT
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="subqueries.html">
15.2.15 Subqueries
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="table.html">
15.2.16 TABLE Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="update.html">
15.2.17 UPDATE Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="union.html">
15.2.18 UNION Clause
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="values.html">
15.2.19 VALUES Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="with.html">
15.2.20 WITH (Common Table Expressions)
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="sql-transactional-statements.html">
15.3 Transactional and Locking Statements
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="commit.html">
15.3.1 START TRANSACTION, COMMIT, and ROLLBACK Statements
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="cannot-roll-back.html">
15.3.2 Statements That Cannot Be Rolled Back
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="implicit-commit.html">
15.3.3 Statements That Cause an Implicit Commit
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="savepoint.html">
15.3.4 SAVEPOINT, ROLLBACK TO SAVEPOINT, and RELEASE SAVEPOINT Statements
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="lock-instance-for-backup.html">
15.3.5 LOCK INSTANCE FOR BACKUP and UNLOCK INSTANCE Statements
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="lock-tables.html">
15.3.6 LOCK TABLES and UNLOCK TABLES Statements
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="set-transaction.html">
15.3.7 SET TRANSACTION Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="xa.html">
15.3.8 XA Transactions
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="sql-replication-statements.html">
15.4 Replication Statements
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="replication-statements-source.html">
15.4.1 SQL Statements for Controlling Source Servers
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="replication-statements-replica.html">
15.4.2 SQL Statements for Controlling Replica Servers
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="replication-statements-group.html">
15.4.3 SQL Statements for Controlling Group Replication
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="sql-prepared-statements.html">
15.5 Prepared Statements
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="prepare.html">
15.5.1 PREPARE Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="execute.html">
15.5.2 EXECUTE Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="deallocate-prepare.html">
15.5.3 DEALLOCATE PREPARE Statement
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="sql-compound-statements.html">
15.6 Compound Statement Syntax
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="begin-end.html">
15.6.1 BEGIN ... END Compound Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="statement-labels.html">
15.6.2 Statement Labels
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="declare.html">
15.6.3 DECLARE Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="stored-program-variables.html">
15.6.4 Variables in Stored Programs
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="flow-control-statements.html">
15.6.5 Flow Control Statements
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="cursors.html">
15.6.6 Cursors
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="condition-handling.html">
15.6.7 Condition Handling
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="condition-handling-restrictions.html">
15.6.8 Restrictions on Condition Handling
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="sql-server-administration-statements.html">
15.7 Database Administration Statements
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="account-management-statements.html">
15.7.1 Account Management Statements
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="resource-group-statements.html">
15.7.2 Resource Group Management Statements
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="table-maintenance-statements.html">
15.7.3 Table Maintenance Statements
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="component-statements.html">
15.7.4 Component, Plugin, and Loadable Function Statements
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="clone.html">
15.7.5 CLONE Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="set-statement.html">
15.7.6 SET Statements
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="show.html">
15.7.7 SHOW Statements
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="other-administrative-statements.html">
15.7.8 Other Administrative Statements
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="sql-utility-statements.html">
15.8 Utility Statements
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="describe.html">
15.8.1 DESCRIBE Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="explain.html">
15.8.2 EXPLAIN Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="help.html">
15.8.3 HELP Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="use.html">
15.8.4 USE Statement
</a>
</span>
</dt>
</dl>
</dd>
</dl>
</dd>
<dt>
<span class="chapter">
<a href="data-dictionary.html">
16 MySQL Data Dictionary
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="data-dictionary-schema.html">
16.1 Data Dictionary Schema
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="data-dictionary-file-removal.html">
16.2 Removal of File-based Metadata Storage
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="data-dictionary-transactional-storage.html">
16.3 Transactional Storage of Dictionary Data
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="data-dictionary-object-cache.html">
16.4 Dictionary Object Cache
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="data-dictionary-information-schema.html">
16.5 INFORMATION_SCHEMA and Data Dictionary Integration
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="serialized-dictionary-information.html">
16.6 Serialized Dictionary Information (SDI)
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="data-dictionary-usage-differences.html">
16.7 Data Dictionary Usage Differences
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="data-dictionary-limitations.html">
16.8 Data Dictionary Limitations
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="chapter">
<a href="innodb-storage-engine.html">
17 The InnoDB Storage Engine
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="innodb-introduction.html">
17.1 Introduction to InnoDB
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="innodb-benefits.html">
17.1.1 Benefits of Using InnoDB Tables
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="innodb-best-practices.html">
17.1.2 Best Practices for InnoDB Tables
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="innodb-check-availability.html">
17.1.3 Verifying that InnoDB is the Default Storage Engine
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="innodb-benchmarking.html">
17.1.4 Testing and Benchmarking with InnoDB
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="mysql-acid.html">
17.2 InnoDB and the ACID Model
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="innodb-multi-versioning.html">
17.3 InnoDB Multi-Versioning
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="innodb-architecture.html">
17.4 InnoDB Architecture
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="innodb-in-memory-structures.html">
17.5 InnoDB In-Memory Structures
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="innodb-buffer-pool.html">
17.5.1 Buffer Pool
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="innodb-change-buffer.html">
17.5.2 Change Buffer
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="innodb-adaptive-hash.html">
17.5.3 Adaptive Hash Index
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="innodb-redo-log-buffer.html">
17.5.4 Log Buffer
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="innodb-on-disk-structures.html">
17.6 InnoDB On-Disk Structures
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="innodb-tables.html">
17.6.1 Tables
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="innodb-indexes.html">
17.6.2 Indexes
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="innodb-tablespace.html">
17.6.3 Tablespaces
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="innodb-doublewrite-buffer.html">
17.6.4 Doublewrite Buffer
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="innodb-redo-log.html">
17.6.5 Redo Log
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="innodb-undo-logs.html">
17.6.6 Undo Logs
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="innodb-locking-transaction-model.html">
17.7 InnoDB Locking and Transaction Model
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="innodb-locking.html">
17.7.1 InnoDB Locking
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="innodb-transaction-model.html">
17.7.2 InnoDB Transaction Model
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="innodb-locks-set.html">
17.7.3 Locks Set by Different SQL Statements in InnoDB
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="innodb-next-key-locking.html">
17.7.4 Phantom Rows
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="innodb-deadlocks.html">
17.7.5 Deadlocks in InnoDB
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="innodb-transaction-scheduling.html">
17.7.6 Transaction Scheduling
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="innodb-configuration.html">
17.8 InnoDB Configuration
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="innodb-init-startup-configuration.html">
17.8.1 InnoDB Startup Configuration
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="innodb-read-only-instance.html">
17.8.2 Configuring InnoDB for Read-Only Operation
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="innodb-performance-buffer-pool.html">
17.8.3 InnoDB Buffer Pool Configuration
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="innodb-performance-thread_concurrency.html">
17.8.4 Configuring Thread Concurrency for InnoDB
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="innodb-performance-multiple_io_threads.html">
17.8.5 Configuring the Number of Background InnoDB I/O Threads
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="innodb-linux-native-aio.html">
17.8.6 Using Asynchronous I/O on Linux
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="innodb-configuring-io-capacity.html">
17.8.7 Configuring InnoDB I/O Capacity
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="innodb-performance-spin_lock_polling.html">
17.8.8 Configuring Spin Lock Polling
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="innodb-purge-configuration.html">
17.8.9 Purge Configuration
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="innodb-performance-optimizer-statistics.html">
17.8.10 Configuring Optimizer Statistics for InnoDB
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="index-page-merge-threshold.html">
17.8.11 Configuring the Merge Threshold for Index Pages
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="innodb-dedicated-server.html">
17.8.12 Enabling Automatic InnoDB Configuration for a Dedicated MySQL Server
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="innodb-compression.html">
17.9 InnoDB Table and Page Compression
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="innodb-table-compression.html">
17.9.1 InnoDB Table Compression
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="innodb-page-compression.html">
17.9.2 InnoDB Page Compression
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="innodb-row-format.html">
17.10 InnoDB Row Formats
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="innodb-disk-management.html">
17.11 InnoDB Disk I/O and File Space Management
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="innodb-disk-io.html">
17.11.1 InnoDB Disk I/O
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="innodb-file-space.html">
17.11.2 File Space Management
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="innodb-checkpoints.html">
17.11.3 InnoDB Checkpoints
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="innodb-file-defragmenting.html">
17.11.4 Defragmenting a Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="innodb-truncate-table-reclaim-space.html">
17.11.5 Reclaiming Disk Space with TRUNCATE TABLE
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="innodb-online-ddl.html">
17.12 InnoDB and Online DDL
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="innodb-online-ddl-operations.html">
17.12.1 Online DDL Operations
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="innodb-online-ddl-performance.html">
17.12.2 Online DDL Performance and Concurrency
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="innodb-online-ddl-space-requirements.html">
17.12.3 Online DDL Space Requirements
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="online-ddl-memory-management.html">
17.12.4 Online DDL Memory Management
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="online-ddl-parallel-thread-configuration.html">
17.12.5 Configuring Parallel Threads for Online DDL Operations
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="innodb-online-ddl-single-multi.html">
17.12.6 Simplifying DDL Statements with Online DDL
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="innodb-online-ddl-failure-conditions.html">
17.12.7 Online DDL Failure Conditions
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="innodb-online-ddl-limitations.html">
17.12.8 Online DDL Limitations
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="innodb-data-encryption.html">
17.13 InnoDB Data-at-Rest Encryption
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="innodb-parameters.html">
17.14 InnoDB Startup Options and System Variables
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="innodb-information-schema.html">
17.15 InnoDB INFORMATION_SCHEMA Tables
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="innodb-information-schema-compression-tables.html">
17.15.1 InnoDB INFORMATION_SCHEMA Tables about Compression
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="innodb-information-schema-transactions.html">
17.15.2 InnoDB INFORMATION_SCHEMA Transaction and Locking Information
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="innodb-information-schema-system-tables.html">
17.15.3 InnoDB INFORMATION_SCHEMA Schema Object Tables
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="innodb-information-schema-fulltext_index-tables.html">
17.15.4 InnoDB INFORMATION_SCHEMA FULLTEXT Index Tables
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="innodb-information-schema-buffer-pool-tables.html">
17.15.5 InnoDB INFORMATION_SCHEMA Buffer Pool Tables
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="innodb-information-schema-metrics-table.html">
17.15.6 InnoDB INFORMATION_SCHEMA Metrics Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="innodb-information-schema-temp-table-info.html">
17.15.7 InnoDB INFORMATION_SCHEMA Temporary Table Info Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="innodb-information-schema-files-table.html">
17.15.8 Retrieving InnoDB Tablespace Metadata from INFORMATION_SCHEMA.FILES
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="innodb-performance-schema.html">
17.16 InnoDB Integration with MySQL Performance Schema
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="monitor-alter-table-performance-schema.html">
17.16.1 Monitoring ALTER TABLE Progress for InnoDB Tables Using Performance
Schema
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="monitor-innodb-mutex-waits-performance-schema.html">
17.16.2 Monitoring InnoDB Mutex Waits Using Performance Schema
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="innodb-monitors.html">
17.17 InnoDB Monitors
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="innodb-monitor-types.html">
17.17.1 InnoDB Monitor Types
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="innodb-enabling-monitors.html">
17.17.2 Enabling InnoDB Monitors
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="innodb-standard-monitor.html">
17.17.3 InnoDB Standard Monitor and Lock Monitor Output
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="innodb-backup-recovery.html">
17.18 InnoDB Backup and Recovery
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="innodb-backup.html">
17.18.1 InnoDB Backup
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="innodb-recovery.html">
17.18.2 InnoDB Recovery
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="innodb-and-mysql-replication.html">
17.19 InnoDB and MySQL Replication
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="innodb-troubleshooting.html">
17.20 InnoDB Troubleshooting
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="error-creating-innodb.html">
17.20.1 Troubleshooting InnoDB I/O Problems
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="innodb-troubleshooting-recovery.html">
17.20.2 Troubleshooting Recovery Failures
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="forcing-innodb-recovery.html">
17.20.3 Forcing InnoDB Recovery
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="innodb-troubleshooting-datadict.html">
17.20.4 Troubleshooting InnoDB Data Dictionary Operations
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="innodb-error-handling.html">
17.20.5 InnoDB Error Handling
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="innodb-limits.html">
17.21 InnoDB Limits
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="innodb-restrictions-limitations.html">
17.22 InnoDB Restrictions and Limitations
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="chapter">
<a href="storage-engines.html">
18 Alternative Storage Engines
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="storage-engine-setting.html">
18.1 Setting the Storage Engine
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="myisam-storage-engine.html">
18.2 The MyISAM Storage Engine
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="myisam-start.html">
18.2.1 MyISAM Startup Options
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="key-space.html">
18.2.2 Space Needed for Keys
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="myisam-table-formats.html">
18.2.3 MyISAM Table Storage Formats
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="myisam-table-problems.html">
18.2.4 MyISAM Table Problems
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="memory-storage-engine.html">
18.3 The MEMORY Storage Engine
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="csv-storage-engine.html">
18.4 The CSV Storage Engine
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="se-csv-repair.html">
18.4.1 Repairing and Checking CSV Tables
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="se-csv-limitations.html">
18.4.2 CSV Limitations
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="archive-storage-engine.html">
18.5 The ARCHIVE Storage Engine
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="blackhole-storage-engine.html">
18.6 The BLACKHOLE Storage Engine
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="merge-storage-engine.html">
18.7 The MERGE Storage Engine
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="merge-table-advantages.html">
18.7.1 MERGE Table Advantages and Disadvantages
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="merge-table-problems.html">
18.7.2 MERGE Table Problems
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="federated-storage-engine.html">
18.8 The FEDERATED Storage Engine
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="federated-description.html">
18.8.1 FEDERATED Storage Engine Overview
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="federated-create.html">
18.8.2 How to Create FEDERATED Tables
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="federated-usagenotes.html">
18.8.3 FEDERATED Storage Engine Notes and Tips
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="federated-storage-engine-resources.html">
18.8.4 FEDERATED Storage Engine Resources
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="example-storage-engine.html">
18.9 The EXAMPLE Storage Engine
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="storage-engines-other.html">
18.10 Other Storage Engines
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="pluggable-storage-overview.html">
18.11 Overview of MySQL Storage Engine Architecture
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="pluggable-storage.html">
18.11.1 Pluggable Storage Engine Architecture
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="pluggable-storage-common-layer.html">
18.11.2 The Common Database Server Layer
</a>
</span>
</dt>
</dl>
</dd>
</dl>
</dd>
<dt>
<span class="chapter">
<a href="replication.html">
19 Replication
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="replication-configuration.html">
19.1 Configuring Replication
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="binlog-replication-configuration-overview.html">
19.1.1 Binary Log File Position Based Replication Configuration Overview
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="replication-howto.html">
19.1.2 Setting Up Binary Log File Position Based Replication
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="replication-gtids.html">
19.1.3 Replication with Global Transaction Identifiers
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="replication-mode-change-online.html">
19.1.4 Changing GTID Mode on Online Servers
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="replication-multi-source.html">
19.1.5 MySQL Multi-Source Replication
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="replication-options.html">
19.1.6 Replication and Binary Logging Options and Variables
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="replication-administration.html">
19.1.7 Common Replication Administration Tasks
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="replication-implementation.html">
19.2 Replication Implementation
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="replication-formats.html">
19.2.1 Replication Formats
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="replication-channels.html">
19.2.2 Replication Channels
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="replication-threads.html">
19.2.3 Replication Threads
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="replica-logs.html">
19.2.4 Relay Log and Replication Metadata Repositories
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="replication-rules.html">
19.2.5 How Servers Evaluate Replication Filtering Rules
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="replication-security.html">
19.3 Replication Security
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="replication-encrypted-connections.html">
19.3.1 Setting Up Replication to Use Encrypted Connections
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="replication-binlog-encryption.html">
19.3.2 Encrypting Binary Log Files and Relay Log Files
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="replication-privilege-checks.html">
19.3.3 Replication Privilege Checks
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="replication-solutions.html">
19.4 Replication Solutions
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="replication-solutions-backups.html">
19.4.1 Using Replication for Backups
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="replication-solutions-unexpected-replica-halt.html">
19.4.2 Handling an Unexpected Halt of a Replica
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="replication-solutions-rbr-monitoring.html">
19.4.3 Monitoring Row-based Replication
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="replication-solutions-diffengines.html">
19.4.4 Using Replication with Different Source and Replica Storage Engines
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="replication-solutions-scaleout.html">
19.4.5 Using Replication for Scale-Out
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="replication-solutions-partitioning.html">
19.4.6 Replicating Different Databases to Different Replicas
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="replication-solutions-performance.html">
19.4.7 Improving Replication Performance
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="replication-solutions-switch.html">
19.4.8 Switching Sources During Failover
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="replication-asynchronous-connection-failover.html">
19.4.9 Switching Sources and Replicas with Asynchronous Connection Failover
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="replication-semisync.html">
19.4.10 Semisynchronous Replication
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="replication-delayed.html">
19.4.11 Delayed Replication
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="replication-notes.html">
19.5 Replication Notes and Tips
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="replication-features.html">
19.5.1 Replication Features and Issues
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="replication-compatibility.html">
19.5.2 Replication Compatibility Between MySQL Versions
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="replication-upgrade.html">
19.5.3 Upgrading or Downgrading a Replication Topology
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="replication-problems.html">
19.5.4 Troubleshooting Replication
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="replication-bugs.html">
19.5.5 How to Report Replication Bugs or Problems
</a>
</span>
</dt>
</dl>
</dd>
</dl>
</dd>
<dt>
<span class="chapter">
<a href="group-replication.html">
20 Group Replication
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="group-replication-background.html">
20.1 Group Replication Background
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="group-replication-replication-technologies.html">
20.1.1 Replication Technologies
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="group-replication-use-cases.html">
20.1.2 Group Replication Use Cases
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="group-replication-deploying-in-multi-primary-or-single-primary-mode.html">
20.1.3 Multi-Primary and Single-Primary Modes
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="group-replication-details.html">
20.1.4 Group Replication Services
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="group-replication-plugin-architecture.html">
20.1.5 Group Replication Plugin Architecture
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="group-replication-getting-started.html">
20.2 Getting Started
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="group-replication-deploying-in-single-primary-mode.html">
20.2.1 Deploying Group Replication in Single-Primary Mode
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="group-replication-deploying-locally.html">
20.2.2 Deploying Group Replication Locally
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="group-replication-requirements-and-limitations.html">
20.3 Requirements and Limitations
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="group-replication-requirements.html">
20.3.1 Group Replication Requirements
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="group-replication-limitations.html">
20.3.2 Group Replication Limitations
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="group-replication-monitoring.html">
20.4 Monitoring Group Replication
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="group-replication-gtids.html">
20.4.1 GTIDs and Group Replication
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="group-replication-server-states.html">
20.4.2 Group Replication Server States
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="group-replication-replication-group-members.html">
20.4.3 The replication_group_members Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="group-replication-replication-group-member-stats.html">
20.4.4 The replication_group_member_stats Table
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="group-replication-operations.html">
20.5 Group Replication Operations
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="group-replication-configuring-online-group.html">
20.5.1 Configuring an Online Group
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="group-replication-restarting-group.html">
20.5.2 Restarting a Group
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="group-replication-consistency-guarantees.html">
20.5.3 Transaction Consistency Guarantees
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="group-replication-distributed-recovery.html">
20.5.4 Distributed Recovery
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="group-replication-ipv6.html">
20.5.5 Support For IPv6 And For Mixed IPv6 And IPv4 Groups
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="group-replication-enterprise-backup.html">
20.5.6 Using MySQL Enterprise Backup with Group Replication
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="group-replication-security.html">
20.6 Group Replication Security
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="group-replication-connection-security.html">
20.6.1 Communication Stack for Connection Security Management
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="group-replication-secure-socket-layer-support-ssl.html">
20.6.2 Securing Group Communication Connections with Secure Socket Layer (SSL)
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="group-replication-distributed-recovery-securing.html">
20.6.3 Securing Distributed Recovery Connections
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="group-replication-ip-address-permissions.html">
20.6.4 Group Replication IP Address Permissions
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="group-replication-performance.html">
20.7 Group Replication Performance and Troubleshooting
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="group-replication-fine-tuning-the-group-communication-thread.html">
20.7.1 Fine Tuning the Group Communication Thread
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="group-replication-flow-control.html">
20.7.2 Flow Control
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="group-replication-single-consensus-leader.html">
20.7.3 Single Consensus Leader
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="group-replication-message-compression.html">
20.7.4 Message Compression
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="group-replication-performance-message-fragmentation.html">
20.7.5 Message Fragmentation
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="group-replication-performance-xcom-cache.html">
20.7.6 XCom Cache Management
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="group-replication-responses-failure.html">
20.7.7 Responses to Failure Detection and Network Partitioning
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="group-replication-network-partitioning.html">
20.7.8 Handling a Network Partition and Loss of Quorum
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-gr-memory-monitoring-ps-instruments.html">
20.7.9 Monitoring Group Replication Memory Usage with Performance Schema Memory
Instrumentation
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="group-replication-upgrade.html">
20.8 Upgrading Group Replication
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="group-replication-online-upgrade-combining-versions.html">
20.8.1 Combining Different Member Versions in a Group
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="group-replication-offline-upgrade.html">
20.8.2 Group Replication Offline Upgrade
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="group-replication-online-upgrade.html">
20.8.3 Group Replication Online Upgrade
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="group-replication-options.html">
20.9 Group Replication Variables
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="group-replication-system-variables.html">
20.9.1 Group Replication System Variables
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="group-replication-status-variables.html">
20.9.2 Group Replication Status Variables
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="group-replication-frequently-asked-questions.html">
20.10 Frequently Asked Questions
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="chapter">
<a href="mysql-shell-userguide.html">
21 MySQL Shell
</a>
</span>
</dt>
<dt>
<span class="chapter">
<a href="document-store.html">
22 Using MySQL as a Document Store
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="document-store-interfaces.html">
22.1 Interfaces to a MySQL Document Store
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="document-store-concepts.html">
22.2 Document Store Concepts
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-shell-tutorial-javascript.html">
22.3 JavaScript Quick-Start Guide: MySQL Shell for Document Store
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="mysql-shell-tutorial-javascript-shell.html">
22.3.1 MySQL Shell
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-shell-tutorial-javascript-download.html">
22.3.2 Download and Import world_x Database
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-shell-tutorial-javascript-documents-collections.html">
22.3.3 Documents and Collections
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-shell-tutorial-javascript-relational-tables.html">
22.3.4 Relational Tables
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-shell-tutorial-javascript-documents-in-tables.html">
22.3.5 Documents in Tables
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="mysql-shell-tutorial-python.html">
22.4 Python Quick-Start Guide: MySQL Shell for Document Store
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="mysql-shell-tutorial-python-shell.html">
22.4.1 MySQL Shell
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-shell-tutorial-python-download.html">
22.4.2 Download and Import world_x Database
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-shell-tutorial-python-documents-collections.html">
22.4.3 Documents and Collections
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-shell-tutorial-python-relational-tables.html">
22.4.4 Relational Tables
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-shell-tutorial-python-documents-in-tables.html">
22.4.5 Documents in Tables
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="x-plugin.html">
22.5 X Plugin
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="x-plugin-checking-installation.html">
22.5.1 Checking X Plugin Installation
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="x-plugin-disabling.html">
22.5.2 Disabling X Plugin
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="x-plugin-encrypted-connections.html">
22.5.3 Using Encrypted Connections with X Plugin
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="x-plugin-sha2-cache-plugin.html">
22.5.4 Using X Plugin with the Caching SHA-2 Authentication Plugin
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="x-plugin-connection-compression.html">
22.5.5 Connection Compression with X Plugin
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="x-plugin-options-variables.html">
22.5.6 X Plugin Options and Variables
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="x-plugin-system-monitoring.html">
22.5.7 Monitoring X Plugin
</a>
</span>
</dt>
</dl>
</dd>
</dl>
</dd>
<dt>
<span class="chapter">
<a href="mysql-innodb-cluster-introduction.html">
23 InnoDB Cluster
</a>
</span>
</dt>
<dt>
<span class="chapter">
<a href="mysql-innodb-replicaset-introduction.html">
24 InnoDB ReplicaSet
</a>
</span>
</dt>
<dt>
<span class="chapter">
<a href="mysql-cluster.html">
25 MySQL NDB Cluster 8.4
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="mysql-cluster-general-info.html">
25.1 General Information
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-overview.html">
25.2 NDB Cluster Overview
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="mysql-cluster-basics.html">
25.2.1 NDB Cluster Core Concepts
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-nodes-groups.html">
25.2.2 NDB Cluster Nodes, Node Groups, Fragment Replicas, and Partitions
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-overview-requirements.html">
25.2.3 NDB Cluster Hardware, Software, and Networking Requirements
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-what-is-new.html">
25.2.4 What is New in MySQL NDB Cluster 8.4
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-added-deprecated-removed.html">
25.2.5 Options, Variables, and Parameters Added, Deprecated or Removed in NDB
8.4
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-compared.html">
25.2.6 MySQL Server Using InnoDB Compared with NDB Cluster
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-limitations.html">
25.2.7 Known Limitations of NDB Cluster
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="mysql-cluster-installation.html">
25.3 NDB Cluster Installation
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="mysql-cluster-install-linux.html">
25.3.1 Installation of NDB Cluster on Linux
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-install-windows.html">
25.3.2 Installing NDB Cluster on Windows
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-install-configuration.html">
25.3.3 Initial Configuration of NDB Cluster
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-install-first-start.html">
25.3.4 Initial Startup of NDB Cluster
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-install-example-data.html">
25.3.5 NDB Cluster Example with Tables and Data
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-install-shutdown-restart.html">
25.3.6 Safe Shutdown and Restart of NDB Cluster
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-upgrade-downgrade.html">
25.3.7 Upgrading and Downgrading NDB Cluster
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="mysql-cluster-configuration.html">
25.4 Configuration of NDB Cluster
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="mysql-cluster-quick.html">
25.4.1 Quick Test Setup of NDB Cluster
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-configuration-overview.html">
25.4.2 Overview of NDB Cluster Configuration Parameters, Options, and Variables
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-config-file.html">
25.4.3 NDB Cluster Configuration Files
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-interconnects.html">
25.4.4 Using High-Speed Interconnects with NDB Cluster
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="mysql-cluster-programs.html">
25.5 NDB Cluster Programs
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="mysql-cluster-programs-ndbd.html">
25.5.1 ndbd — The NDB Cluster Data Node Daemon
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-programs-ndbinfo-select-all.html">
25.5.2 ndbinfo_select_all — Select From ndbinfo Tables
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-programs-ndbmtd.html">
25.5.3 ndbmtd — The NDB Cluster Data Node Daemon (Multi-Threaded)
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-programs-ndb-mgmd.html">
25.5.4 ndb_mgmd — The NDB Cluster Management Server Daemon
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-programs-ndb-mgm.html">
25.5.5 ndb_mgm — The NDB Cluster Management Client
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-programs-ndb-blob-tool.html">
25.5.6 ndb_blob_tool — Check and Repair BLOB and TEXT columns of NDB Cluster
Tables
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-programs-ndb-config.html">
25.5.7 ndb_config — Extract NDB Cluster Configuration Information
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-programs-ndb-delete-all.html">
25.5.8 ndb_delete_all — Delete All Rows from an NDB Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-programs-ndb-desc.html">
25.5.9 ndb_desc — Describe NDB Tables
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-programs-ndb-drop-index.html">
25.5.10 ndb_drop_index — Drop Index from an NDB Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-programs-ndb-drop-table.html">
25.5.11 ndb_drop_table — Drop an NDB Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-programs-ndb-error-reporter.html">
25.5.12 ndb_error_reporter — NDB Error-Reporting Utility
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-programs-ndb-import.html">
25.5.13 ndb_import — Import CSV Data Into NDB
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-programs-ndb-index-stat.html">
25.5.14 ndb_index_stat — NDB Index Statistics Utility
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-programs-ndb-move-data.html">
25.5.15 ndb_move_data — NDB Data Copy Utility
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-programs-ndb-perror.html">
25.5.16 ndb_perror — Obtain NDB Error Message Information
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-programs-ndb-print-backup-file.html">
25.5.17 ndb_print_backup_file — Print NDB Backup File Contents
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-programs-ndb-print-file.html">
25.5.18 ndb_print_file — Print NDB Disk Data File Contents
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-programs-ndb-print-frag-file.html">
25.5.19 ndb_print_frag_file — Print NDB Fragment List File Contents
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-programs-ndb-print-schema-file.html">
25.5.20 ndb_print_schema_file — Print NDB Schema File Contents
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-programs-ndb-print-sys-file.html">
25.5.21 ndb_print_sys_file — Print NDB System File Contents
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-programs-ndb-redo-log-reader.html">
25.5.22 ndb_redo_log_reader — Check and Print Content of Cluster Redo Log
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-programs-ndb-restore.html">
25.5.23 ndb_restore — Restore an NDB Cluster Backup
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-programs-ndb-secretsfile-reader.html">
25.5.24 ndb_secretsfile_reader — Obtain Key Information from an Encrypted NDB
Data File
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-programs-ndb-select-all.html">
25.5.25 ndb_select_all — Print Rows from an NDB Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-programs-ndb-select-count.html">
25.5.26 ndb_select_count — Print Row Counts for NDB Tables
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-programs-ndb-show-tables.html">
25.5.27 ndb_show_tables — Display List of NDB Tables
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-programs-ndb-sign-keys.html">
25.5.28 ndb_sign_keys — Create, Sign, and Manage TLS Keys and Certificates for NDB
Cluster
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-programs-ndb-size-pl.html">
25.5.29 ndb_size.pl — NDBCLUSTER Size Requirement Estimator
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-programs-ndb-top.html">
25.5.30 ndb_top — View CPU usage information for NDB threads
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-programs-ndb-waiter.html">
25.5.31 ndb_waiter — Wait for NDB Cluster to Reach a Given Status
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-programs-ndbxfrm.html">
25.5.32 ndbxfrm — Compress, Decompress, Encrypt, and Decrypt
Files Created by NDB Cluster
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="mysql-cluster-management.html">
25.6 Management of NDB Cluster
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="mysql-cluster-mgm-client-commands.html">
25.6.1 Commands in the NDB Cluster Management Client
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-logs-ndb-messages.html">
25.6.2 NDB Cluster Log Messages
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-event-reports.html">
25.6.3 Event Reports Generated in NDB Cluster
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-start-phases.html">
25.6.4 Summary of NDB Cluster Start Phases
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-rolling-restart.html">
25.6.5 Performing a Rolling Restart of an NDB Cluster
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-single-user-mode.html">
25.6.6 NDB Cluster Single User Mode
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-online-add-node.html">
25.6.7 Adding NDB Cluster Data Nodes Online
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-backup.html">
25.6.8 Online Backup of NDB Cluster
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-importing-data.html">
25.6.9 Importing Data Into MySQL Cluster
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-mysqld.html">
25.6.10 MySQL Server Usage for NDB Cluster
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-disk-data.html">
25.6.11 NDB Cluster Disk Data Tables
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-online-operations.html">
25.6.12 Online Operations with ALTER TABLE in NDB Cluster
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-privilege-synchronization.html">
25.6.13 Privilege Synchronization and NDB_STORED_USER
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-tde.html">
25.6.14 File System Encryption for NDB Cluster
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-tls.html">
25.6.15 TLS Link Encryption for NDB Cluster
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-ndb-api-statistics.html">
25.6.16 NDB API Statistics Counters and Variables
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-ndbinfo.html">
25.6.17 ndbinfo: The NDB Cluster Information Database
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-information-schema-tables.html">
25.6.18 INFORMATION_SCHEMA Tables for NDB Cluster
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-ps-tables.html">
25.6.19 NDB Cluster and the Performance Schema
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-sql-statements.html">
25.6.20 Quick Reference: NDB Cluster SQL Statements
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-security.html">
25.6.21 NDB Cluster Security Issues
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="mysql-cluster-replication.html">
25.7 NDB Cluster Replication
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="mysql-cluster-replication-abbreviations.html">
25.7.1 NDB Cluster Replication: Abbreviations and Symbols
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-replication-general.html">
25.7.2 General Requirements for NDB Cluster Replication
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-replication-issues.html">
25.7.3 Known Issues in NDB Cluster Replication
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-replication-schema.html">
25.7.4 NDB Cluster Replication Schema and Tables
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-replication-preparation.html">
25.7.5 Preparing the NDB Cluster for Replication
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-replication-starting.html">
25.7.6 Starting NDB Cluster Replication (Single Replication Channel)
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-replication-two-channels.html">
25.7.7 Using Two Replication Channels for NDB Cluster Replication
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-replication-failover.html">
25.7.8 Implementing Failover with NDB Cluster Replication
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-replication-backups.html">
25.7.9 NDB Cluster Backups With NDB Cluster Replication
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-replication-multi-source.html">
25.7.10 NDB Cluster Replication: Bidirectional and Circular Replication
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-replication-mta.html">
25.7.11 NDB Cluster Replication Using the Multithreaded Applier
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-replication-conflict-resolution.html">
25.7.12 NDB Cluster Replication Conflict Resolution
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="mysql-cluster-news.html">
25.8 NDB Cluster Release Notes
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="chapter">
<a href="partitioning.html">
26 Partitioning
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="partitioning-overview.html">
26.1 Overview of Partitioning in MySQL
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="partitioning-types.html">
26.2 Partitioning Types
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="partitioning-range.html">
26.2.1 RANGE Partitioning
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="partitioning-list.html">
26.2.2 LIST Partitioning
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="partitioning-columns.html">
26.2.3 COLUMNS Partitioning
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="partitioning-hash.html">
26.2.4 HASH Partitioning
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="partitioning-key.html">
26.2.5 KEY Partitioning
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="partitioning-subpartitions.html">
26.2.6 Subpartitioning
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="partitioning-handling-nulls.html">
26.2.7 How MySQL Partitioning Handles NULL
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="partitioning-management.html">
26.3 Partition Management
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="partitioning-management-range-list.html">
26.3.1 Management of RANGE and LIST Partitions
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="partitioning-management-hash-key.html">
26.3.2 Management of HASH and KEY Partitions
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="partitioning-management-exchange.html">
26.3.3 Exchanging Partitions and Subpartitions with Tables
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="partitioning-maintenance.html">
26.3.4 Maintenance of Partitions
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="partitioning-info.html">
26.3.5 Obtaining Information About Partitions
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="partitioning-pruning.html">
26.4 Partition Pruning
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="partitioning-selection.html">
26.5 Partition Selection
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="partitioning-limitations.html">
26.6 Restrictions and Limitations on Partitioning
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="partitioning-limitations-partitioning-keys-unique-keys.html">
26.6.1 Partitioning Keys, Primary Keys, and Unique Keys
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="partitioning-limitations-storage-engines.html">
26.6.2 Partitioning Limitations Relating to Storage Engines
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="partitioning-limitations-functions.html">
26.6.3 Partitioning Limitations Relating to Functions
</a>
</span>
</dt>
</dl>
</dd>
</dl>
</dd>
<dt>
<span class="chapter">
<a href="stored-objects.html">
27 Stored Objects
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="stored-programs-defining.html">
27.1 Defining Stored Programs
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="stored-routines.html">
27.2 Using Stored Routines
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="stored-routines-syntax.html">
27.2.1 Stored Routine Syntax
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="stored-routines-privileges.html">
27.2.2 Stored Routines and MySQL Privileges
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="stored-routines-metadata.html">
27.2.3 Stored Routine Metadata
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="stored-routines-last-insert-id.html">
27.2.4 Stored Procedures, Functions, Triggers, and LAST_INSERT_ID()
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="triggers.html">
27.3 Using Triggers
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="trigger-syntax.html">
27.3.1 Trigger Syntax and Examples
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="trigger-metadata.html">
27.3.2 Trigger Metadata
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="event-scheduler.html">
27.4 Using the Event Scheduler
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="events-overview.html">
27.4.1 Event Scheduler Overview
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="events-configuration.html">
27.4.2 Event Scheduler Configuration
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="events-syntax.html">
27.4.3 Event Syntax
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="events-metadata.html">
27.4.4 Event Metadata
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="events-status-info.html">
27.4.5 Event Scheduler Status
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="events-privileges.html">
27.4.6 The Event Scheduler and MySQL Privileges
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="views.html">
27.5 Using Views
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="view-syntax.html">
27.5.1 View Syntax
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="view-algorithms.html">
27.5.2 View Processing Algorithms
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="view-updatability.html">
27.5.3 Updatable and Insertable Views
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="view-check-option.html">
27.5.4 The View WITH CHECK OPTION Clause
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="view-metadata.html">
27.5.5 View Metadata
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="stored-objects-security.html">
27.6 Stored Object Access Control
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="stored-programs-logging.html">
27.7 Stored Program Binary Logging
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="stored-program-restrictions.html">
27.8 Restrictions on Stored Programs
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="view-restrictions.html">
27.9 Restrictions on Views
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="chapter">
<a href="information-schema.html">
28 INFORMATION_SCHEMA Tables
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="information-schema-introduction.html">
28.1 Introduction
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="information-schema-table-reference.html">
28.2 INFORMATION_SCHEMA Table Reference
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="general-information-schema-tables.html">
28.3 INFORMATION_SCHEMA General Tables
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="information-schema-general-table-reference.html">
28.3.1 INFORMATION_SCHEMA General Table Reference
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="information-schema-administrable-role-authorizations-table.html">
28.3.2 The INFORMATION_SCHEMA ADMINISTRABLE_ROLE_AUTHORIZATIONS Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="information-schema-applicable-roles-table.html">
28.3.3 The INFORMATION_SCHEMA APPLICABLE_ROLES Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="information-schema-character-sets-table.html">
28.3.4 The INFORMATION_SCHEMA CHARACTER_SETS Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="information-schema-check-constraints-table.html">
28.3.5 The INFORMATION_SCHEMA CHECK_CONSTRAINTS Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="information-schema-collations-table.html">
28.3.6 The INFORMATION_SCHEMA COLLATIONS Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="information-schema-collation-character-set-applicability-table.html">
28.3.7 The INFORMATION_SCHEMA COLLATION_CHARACTER_SET_APPLICABILITY Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="information-schema-columns-table.html">
28.3.8 The INFORMATION_SCHEMA COLUMNS Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="information-schema-columns-extensions-table.html">
28.3.9 The INFORMATION_SCHEMA COLUMNS_EXTENSIONS Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="information-schema-column-privileges-table.html">
28.3.10 The INFORMATION_SCHEMA COLUMN_PRIVILEGES Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="information-schema-column-statistics-table.html">
28.3.11 The INFORMATION_SCHEMA COLUMN_STATISTICS Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="information-schema-enabled-roles-table.html">
28.3.12 The INFORMATION_SCHEMA ENABLED_ROLES Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="information-schema-engines-table.html">
28.3.13 The INFORMATION_SCHEMA ENGINES Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="information-schema-events-table.html">
28.3.14 The INFORMATION_SCHEMA EVENTS Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="information-schema-files-table.html">
28.3.15 The INFORMATION_SCHEMA FILES Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="information-schema-key-column-usage-table.html">
28.3.16 The INFORMATION_SCHEMA KEY_COLUMN_USAGE Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="information-schema-keywords-table.html">
28.3.17 The INFORMATION_SCHEMA KEYWORDS Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="information-schema-ndb-transid-mysql-connection-map-table.html">
28.3.18 The INFORMATION_SCHEMA ndb_transid_mysql_connection_map Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="information-schema-optimizer-trace-table.html">
28.3.19 The INFORMATION_SCHEMA OPTIMIZER_TRACE Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="information-schema-parameters-table.html">
28.3.20 The INFORMATION_SCHEMA PARAMETERS Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="information-schema-partitions-table.html">
28.3.21 The INFORMATION_SCHEMA PARTITIONS Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="information-schema-plugins-table.html">
28.3.22 The INFORMATION_SCHEMA PLUGINS Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="information-schema-processlist-table.html">
28.3.23 The INFORMATION_SCHEMA PROCESSLIST Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="information-schema-profiling-table.html">
28.3.24 The INFORMATION_SCHEMA PROFILING Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="information-schema-referential-constraints-table.html">
28.3.25 The INFORMATION_SCHEMA REFERENTIAL_CONSTRAINTS Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="information-schema-resource-groups-table.html">
28.3.26 The INFORMATION_SCHEMA RESOURCE_GROUPS Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="information-schema-role-column-grants-table.html">
28.3.27 The INFORMATION_SCHEMA ROLE_COLUMN_GRANTS Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="information-schema-role-routine-grants-table.html">
28.3.28 The INFORMATION_SCHEMA ROLE_ROUTINE_GRANTS Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="information-schema-role-table-grants-table.html">
28.3.29 The INFORMATION_SCHEMA ROLE_TABLE_GRANTS Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="information-schema-routines-table.html">
28.3.30 The INFORMATION_SCHEMA ROUTINES Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="information-schema-schemata-table.html">
28.3.31 The INFORMATION_SCHEMA SCHEMATA Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="information-schema-schemata-extensions-table.html">
28.3.32 The INFORMATION_SCHEMA SCHEMATA_EXTENSIONS Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="information-schema-schema-privileges-table.html">
28.3.33 The INFORMATION_SCHEMA SCHEMA_PRIVILEGES Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="information-schema-statistics-table.html">
28.3.34 The INFORMATION_SCHEMA STATISTICS Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="information-schema-st-geometry-columns-table.html">
28.3.35 The INFORMATION_SCHEMA ST_GEOMETRY_COLUMNS Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="information-schema-st-spatial-reference-systems-table.html">
28.3.36 The INFORMATION_SCHEMA ST_SPATIAL_REFERENCE_SYSTEMS Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="information-schema-st-units-of-measure-table.html">
28.3.37 The INFORMATION_SCHEMA ST_UNITS_OF_MEASURE Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="information-schema-tables-table.html">
28.3.38 The INFORMATION_SCHEMA TABLES Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="information-schema-tables-extensions-table.html">
28.3.39 The INFORMATION_SCHEMA TABLES_EXTENSIONS Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="information-schema-tablespaces-extensions-table.html">
28.3.40 The INFORMATION_SCHEMA TABLESPACES_EXTENSIONS Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="information-schema-table-constraints-table.html">
28.3.41 The INFORMATION_SCHEMA TABLE_CONSTRAINTS Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="information-schema-table-constraints-extensions-table.html">
28.3.42 The INFORMATION_SCHEMA TABLE_CONSTRAINTS_EXTENSIONS Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="information-schema-table-privileges-table.html">
28.3.43 The INFORMATION_SCHEMA TABLE_PRIVILEGES Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="information-schema-triggers-table.html">
28.3.44 The INFORMATION_SCHEMA TRIGGERS Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="information-schema-user-attributes-table.html">
28.3.45 The INFORMATION_SCHEMA USER_ATTRIBUTES Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="information-schema-user-privileges-table.html">
28.3.46 The INFORMATION_SCHEMA USER_PRIVILEGES Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="information-schema-views-table.html">
28.3.47 The INFORMATION_SCHEMA VIEWS Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="information-schema-view-routine-usage-table.html">
28.3.48 The INFORMATION_SCHEMA VIEW_ROUTINE_USAGE Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="information-schema-view-table-usage-table.html">
28.3.49 The INFORMATION_SCHEMA VIEW_TABLE_USAGE Table
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="innodb-information-schema-tables.html">
28.4 INFORMATION_SCHEMA InnoDB Tables
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="information-schema-innodb-table-reference.html">
28.4.1 INFORMATION_SCHEMA InnoDB Table Reference
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="information-schema-innodb-buffer-page-table.html">
28.4.2 The INFORMATION_SCHEMA INNODB_BUFFER_PAGE Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="information-schema-innodb-buffer-page-lru-table.html">
28.4.3 The INFORMATION_SCHEMA INNODB_BUFFER_PAGE_LRU Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="information-schema-innodb-buffer-pool-stats-table.html">
28.4.4 The INFORMATION_SCHEMA INNODB_BUFFER_POOL_STATS Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="information-schema-innodb-cached-indexes-table.html">
28.4.5 The INFORMATION_SCHEMA INNODB_CACHED_INDEXES Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="information-schema-innodb-cmp-table.html">
28.4.6 The INFORMATION_SCHEMA INNODB_CMP and INNODB_CMP_RESET Tables
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="information-schema-innodb-cmpmem-table.html">
28.4.7 The INFORMATION_SCHEMA INNODB_CMPMEM and INNODB_CMPMEM_RESET Tables
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="information-schema-innodb-cmp-per-index-table.html">
28.4.8 The INFORMATION_SCHEMA INNODB_CMP_PER_INDEX and
INNODB_CMP_PER_INDEX_RESET Tables
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="information-schema-innodb-columns-table.html">
28.4.9 The INFORMATION_SCHEMA INNODB_COLUMNS Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="information-schema-innodb-datafiles-table.html">
28.4.10 The INFORMATION_SCHEMA INNODB_DATAFILES Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="information-schema-innodb-fields-table.html">
28.4.11 The INFORMATION_SCHEMA INNODB_FIELDS Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="information-schema-innodb-foreign-table.html">
28.4.12 The INFORMATION_SCHEMA INNODB_FOREIGN Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="information-schema-innodb-foreign-cols-table.html">
28.4.13 The INFORMATION_SCHEMA INNODB_FOREIGN_COLS Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="information-schema-innodb-ft-being-deleted-table.html">
28.4.14 The INFORMATION_SCHEMA INNODB_FT_BEING_DELETED Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="information-schema-innodb-ft-config-table.html">
28.4.15 The INFORMATION_SCHEMA INNODB_FT_CONFIG Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="information-schema-innodb-ft-default-stopword-table.html">
28.4.16 The INFORMATION_SCHEMA INNODB_FT_DEFAULT_STOPWORD Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="information-schema-innodb-ft-deleted-table.html">
28.4.17 The INFORMATION_SCHEMA INNODB_FT_DELETED Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="information-schema-innodb-ft-index-cache-table.html">
28.4.18 The INFORMATION_SCHEMA INNODB_FT_INDEX_CACHE Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="information-schema-innodb-ft-index-table-table.html">
28.4.19 The INFORMATION_SCHEMA INNODB_FT_INDEX_TABLE Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="information-schema-innodb-indexes-table.html">
28.4.20 The INFORMATION_SCHEMA INNODB_INDEXES Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="information-schema-innodb-metrics-table.html">
28.4.21 The INFORMATION_SCHEMA INNODB_METRICS Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="information-schema-innodb-session-temp-tablespaces-table.html">
28.4.22 The INFORMATION_SCHEMA INNODB_SESSION_TEMP_TABLESPACES Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="information-schema-innodb-tables-table.html">
28.4.23 The INFORMATION_SCHEMA INNODB_TABLES Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="information-schema-innodb-tablespaces-table.html">
28.4.24 The INFORMATION_SCHEMA INNODB_TABLESPACES Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="information-schema-innodb-tablespaces-brief-table.html">
28.4.25 The INFORMATION_SCHEMA INNODB_TABLESPACES_BRIEF Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="information-schema-innodb-tablestats-table.html">
28.4.26 The INFORMATION_SCHEMA INNODB_TABLESTATS View
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="information-schema-innodb-temp-table-info-table.html">
28.4.27 The INFORMATION_SCHEMA INNODB_TEMP_TABLE_INFO Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="information-schema-innodb-trx-table.html">
28.4.28 The INFORMATION_SCHEMA INNODB_TRX Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="information-schema-innodb-virtual-table.html">
28.4.29 The INFORMATION_SCHEMA INNODB_VIRTUAL Table
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="thread-pool-information-schema-tables.html">
28.5 INFORMATION_SCHEMA Thread Pool Tables
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="information-schema-thread-pool-table-reference.html">
28.5.1 INFORMATION_SCHEMA Thread Pool Table Reference
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="information-schema-tp-thread-group-state-table.html">
28.5.2 The INFORMATION_SCHEMA TP_THREAD_GROUP_STATE Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="information-schema-tp-thread-group-stats-table.html">
28.5.3 The INFORMATION_SCHEMA TP_THREAD_GROUP_STATS Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="information-schema-tp-thread-state-table.html">
28.5.4 The INFORMATION_SCHEMA TP_THREAD_STATE Table
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="connection-control-information-schema-tables.html">
28.6 INFORMATION_SCHEMA Connection-Control Tables
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="information-schema-connection-control-table-reference.html">
28.6.1 INFORMATION_SCHEMA Connection-Control Table Reference
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="information-schema-connection-control-failed-login-attempts-table.html">
28.6.2 The INFORMATION_SCHEMA CONNECTION_CONTROL_FAILED_LOGIN_ATTEMPTS Table
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="firewall-information-schema-tables.html">
28.7 INFORMATION_SCHEMA MySQL Enterprise Firewall Tables
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="information-schema-firewall-table-reference.html">
28.7.1 INFORMATION_SCHEMA Firewall Table Reference
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="information-schema-mysql-firewall-users-table.html">
28.7.2 The INFORMATION_SCHEMA MYSQL_FIREWALL_USERS Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="information-schema-mysql-firewall-whitelist-table.html">
28.7.3 The INFORMATION_SCHEMA MYSQL_FIREWALL_WHITELIST Table
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="extended-show.html">
28.8 Extensions to SHOW Statements
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="chapter">
<a href="performance-schema.html">
29 MySQL Performance Schema
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="performance-schema-quick-start.html">
29.1 Performance Schema Quick Start
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="performance-schema-build-configuration.html">
29.2 Performance Schema Build Configuration
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="performance-schema-startup-configuration.html">
29.3 Performance Schema Startup Configuration
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="performance-schema-runtime-configuration.html">
29.4 Performance Schema Runtime Configuration
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="performance-schema-timing.html">
29.4.1 Performance Schema Event Timing
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="performance-schema-filtering.html">
29.4.2 Performance Schema Event Filtering
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="performance-schema-pre-filtering.html">
29.4.3 Event Pre-Filtering
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="performance-schema-instrument-filtering.html">
29.4.4 Pre-Filtering by Instrument
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="performance-schema-object-filtering.html">
29.4.5 Pre-Filtering by Object
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="performance-schema-thread-filtering.html">
29.4.6 Pre-Filtering by Thread
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="performance-schema-consumer-filtering.html">
29.4.7 Pre-Filtering by Consumer
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="performance-schema-consumer-configurations.html">
29.4.8 Example Consumer Configurations
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="performance-schema-filtering-names.html">
29.4.9 Naming Instruments or Consumers for Filtering Operations
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="performance-schema-instrumentation-checking.html">
29.4.10 Determining What Is Instrumented
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="performance-schema-queries.html">
29.5 Performance Schema Queries
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="performance-schema-instrument-naming.html">
29.6 Performance Schema Instrument Naming Conventions
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="performance-schema-status-monitoring.html">
29.7 Performance Schema Status Monitoring
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="performance-schema-atom-molecule-events.html">
29.8 Performance Schema Atom and Molecule Events
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="performance-schema-event-tables.html">
29.9 Performance Schema Tables for Current and Historical Events
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="performance-schema-statement-digests.html">
29.10 Performance Schema Statement Digests and Sampling
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="performance-schema-table-characteristics.html">
29.11 Performance Schema General Table Characteristics
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="performance-schema-table-descriptions.html">
29.12 Performance Schema Table Descriptions
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="performance-schema-table-reference.html">
29.12.1 Performance Schema Table Reference
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="performance-schema-setup-tables.html">
29.12.2 Performance Schema Setup Tables
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="performance-schema-instance-tables.html">
29.12.3 Performance Schema Instance Tables
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="performance-schema-wait-tables.html">
29.12.4 Performance Schema Wait Event Tables
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="performance-schema-stage-tables.html">
29.12.5 Performance Schema Stage Event Tables
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="performance-schema-statement-tables.html">
29.12.6 Performance Schema Statement Event Tables
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="performance-schema-transaction-tables.html">
29.12.7 Performance Schema Transaction Tables
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="performance-schema-connection-tables.html">
29.12.8 Performance Schema Connection Tables
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="performance-schema-connection-attribute-tables.html">
29.12.9 Performance Schema Connection Attribute Tables
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="performance-schema-user-variable-tables.html">
29.12.10 Performance Schema User-Defined Variable Tables
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="performance-schema-replication-tables.html">
29.12.11 Performance Schema Replication Tables
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="performance-schema-ndb-cluster-tables.html">
29.12.12 Performance Schema NDB Cluster Tables
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="performance-schema-lock-tables.html">
29.12.13 Performance Schema Lock Tables
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="performance-schema-system-variable-tables.html">
29.12.14 Performance Schema System Variable Tables
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="performance-schema-status-variable-tables.html">
29.12.15 Performance Schema Status Variable Tables
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="performance-schema-thread-pool-tables.html">
29.12.16 Performance Schema Thread Pool Tables
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="performance-schema-firewall-tables.html">
29.12.17 Performance Schema Firewall Tables
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="performance-schema-keyring-tables.html">
29.12.18 Performance Schema Keyring Tables
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="performance-schema-clone-tables.html">
29.12.19 Performance Schema Clone Tables
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="performance-schema-summary-tables.html">
29.12.20 Performance Schema Summary Tables
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="performance-schema-telemetry-tables.html">
29.12.21 Performance Schema Telemetry Tables
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="performance-schema-miscellaneous-tables.html">
29.12.22 Performance Schema Miscellaneous Tables
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="performance-schema-option-variable-reference.html">
29.13 Performance Schema Option and Variable Reference
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="performance-schema-options.html">
29.14 Performance Schema Command Options
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="performance-schema-system-variables.html">
29.15 Performance Schema System Variables
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="performance-schema-status-variables.html">
29.16 Performance Schema Status Variables
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="performance-schema-memory-model.html">
29.17 The Performance Schema Memory-Allocation Model
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="performance-schema-and-plugins.html">
29.18 Performance Schema and Plugins
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="performance-schema-examples.html">
29.19 Using the Performance Schema to Diagnose Problems
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="performance-schema-query-profiling.html">
29.19.1 Query Profiling Using Performance Schema
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="performance-schema-obtaining-parent-events.html">
29.19.2 Obtaining Parent Event Information
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="performance-schema-restrictions.html">
29.20 Restrictions on Performance Schema
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="chapter">
<a href="sys-schema.html">
30 MySQL sys Schema
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="sys-schema-prerequisites.html">
30.1 Prerequisites for Using the sys Schema
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="sys-schema-usage.html">
30.2 Using the sys Schema
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="sys-schema-progress-reporting.html">
30.3 sys Schema Progress Reporting
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="sys-schema-reference.html">
30.4 sys Schema Object Reference
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="sys-schema-object-index.html">
30.4.1 sys Schema Object Index
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="sys-schema-tables.html">
30.4.2 sys Schema Tables and Triggers
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="sys-schema-views.html">
30.4.3 sys Schema Views
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="sys-schema-procedures.html">
30.4.4 sys Schema Stored Procedures
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="sys-schema-functions.html">
30.4.5 sys Schema Stored Functions
</a>
</span>
</dt>
</dl>
</dd>
</dl>
</dd>
<dt>
<span class="chapter">
<a href="connectors-apis.html">
31 Connectors and APIs
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="connector-cpp-info.html">
31.1 MySQL Connector/C++
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="connector-j-info.html">
31.2 MySQL Connector/J
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="connector-net-info.html">
31.3 MySQL Connector/NET
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="connector-odbc-info.html">
31.4 MySQL Connector/ODBC
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="connector-python-info.html">
31.5 MySQL Connector/Python
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="connector-nodejs-info.html">
31.6 MySQL Connector/Node.js
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="c-api-info.html">
31.7 MySQL C API
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="apis-php-info.html">
31.8 MySQL PHP API
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="apis-perl.html">
31.9 MySQL Perl API
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="apis-python.html">
31.10 MySQL Python API
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="apis-ruby.html">
31.11 MySQL Ruby APIs
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="apis-ruby-mysqlruby.html">
31.11.1 The MySQL/Ruby API
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="apis-ruby-rubymysql.html">
31.11.2 The Ruby/MySQL API
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="apis-tcl.html">
31.12 MySQL Tcl API
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="apis-eiffel.html">
31.13 MySQL Eiffel Wrapper
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="chapter">
<a href="mysql-enterprise.html">
32 MySQL Enterprise Edition
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="mysql-enterprise-backup.html">
32.1 MySQL Enterprise Backup Overview
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-enterprise-security.html">
32.2 MySQL Enterprise Security Overview
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-enterprise-encryption.html">
32.3 MySQL Enterprise Encryption Overview
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-enterprise-audit.html">
32.4 MySQL Enterprise Audit Overview
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-enterprise-firewall.html">
32.5 MySQL Enterprise Firewall Overview
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-enterprise-thread-pool.html">
32.6 MySQL Enterprise Thread Pool Overview
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-enterprise-data-masking.html">
32.7 MySQL Enterprise Data Masking and De-Identification Overview
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-enterprise-monitor.html">
32.8 MySQL Enterprise Monitor Overview
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-enterprise-telemetry.html">
32.9 MySQL Telemetry
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="chapter">
<a href="workbench.html">
33 MySQL Workbench
</a>
</span>
</dt>
<dt>
<span class="chapter">
<a href="mysql-oci-marketplace.html">
34 MySQL on OCI Marketplace
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="mysql-oci-marketplace-prereqs.html">
34.1 Prerequisites to Deploying MySQL EE on Oracle Cloud Infrastructure
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-oci-marketplace-deploy.html">
34.2 Deploying MySQL EE on Oracle Cloud Infrastructure
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-oci-marketplace-network-configuration.html">
34.3 Configuring Network Access
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-oci-marketplace-connecting.html">
34.4 Connecting
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-oci-marketplace-maintenance.html">
34.5 Maintenance
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="chapter">
<a href="telemetry.html">
35 Telemetry
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="telemetry-trace-install.html">
35.1 Installing OpenTelemetry Support
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="telemetry-system-variables.html">
35.2 Telemetry Variables
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="telemetry-trace.html">
35.3 OpenTelemetry Trace
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="telemetry-trace-configuration.html">
35.3.1 Configuring Trace Telemetry
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="telemetry-trace-format.html">
35.3.2 Trace Format
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="telemetry-metrics.html">
35.4 OpenTelemetry Metrics
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="telemetry-metrics-configuration.html">
35.4.1 Configuring Metrics Telemetry
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="telemetry-metrics-meters.html">
35.4.2 Server Meters
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="telemetry-metrics-meter-metrics.html">
35.4.3 Server Metrics
</a>
</span>
</dt>
</dl>
</dd>
</dl>
</dd>
<dt>
<span class="appendix">
<a href="faqs.html">
A MySQL 8.4 Frequently Asked Questions
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="faqs-general.html">
A.1 MySQL 8.4 FAQ: General
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="faqs-storage-engines.html">
A.2 MySQL 8.4 FAQ: Storage Engines
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="faqs-sql-modes.html">
A.3 MySQL 8.4 FAQ: Server SQL Mode
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="faqs-stored-procs.html">
A.4 MySQL 8.4 FAQ: Stored Procedures and Functions
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="faqs-triggers.html">
A.5 MySQL 8.4 FAQ: Triggers
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="faqs-views.html">
A.6 MySQL 8.4 FAQ: Views
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="faqs-information-schema.html">
A.7 MySQL 8.4 FAQ: INFORMATION_SCHEMA
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="faqs-migration.html">
A.8 MySQL 8.4 FAQ: Migration
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="faqs-security.html">
A.9 MySQL 8.4 FAQ: Security
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="faqs-mysql-cluster.html">
A.10 MySQL 8.4 FAQ: NDB Cluster
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="faqs-cjk.html">
A.11 MySQL 8.4 FAQ: MySQL Chinese, Japanese, and Korean
Character Sets
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="faqs-connectors-apis.html">
A.12 MySQL 8.4 FAQ: Connectors & APIs
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="faqs-c-api.html">
A.13 MySQL 8.4 FAQ: C API, libmysql
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="faqs-replication.html">
A.14 MySQL 8.4 FAQ: Replication
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="faqs-thread-pool.html">
A.15 MySQL 8.4 FAQ: MySQL Enterprise Thread Pool
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="faqs-innodb-change-buffer.html">
A.16 MySQL 8.4 FAQ: InnoDB Change Buffer
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="faqs-tablespace-encryption.html">
A.17 MySQL 8.4 FAQ: InnoDB Data-at-Rest Encryption
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="faqs-virtualization.html">
A.18 MySQL 8.4 FAQ: Virtualization Support
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="appendix">
<a href="error-handling.html">
B Error Messages and Common Problems
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="error-message-elements.html">
B.1 Error Message Sources and Elements
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="error-interfaces.html">
B.2 Error Information Interfaces
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="problems.html">
B.3 Problems and Common Errors
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="what-is-crashing.html">
B.3.1 How to Determine What Is Causing a Problem
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="common-errors.html">
B.3.2 Common Errors When Using MySQL Programs
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="administration-issues.html">
B.3.3 Administration-Related Issues
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="query-issues.html">
B.3.4 Query-Related Issues
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="optimizer-issues.html">
B.3.5 Optimizer-Related Issues
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="table-definition-issues.html">
B.3.6 Table Definition-Related Issues
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="known-issues.html">
B.3.7 Known Issues in MySQL
</a>
</span>
</dt>
</dl>
</dd>
</dl>
</dd>
<dt>
<span class="appendix">
<a href="indexes.html">
C Indexes
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="index">
<a href="ix01.html">
General Index
</a>
</span>
</dt>
<dt>
<span class="index">
<a href="dynindex-cfunc.html">
C Function Index
</a>
</span>
</dt>
<dt>
<span class="index">
<a href="dynindex-command.html">
Command Index
</a>
</span>
</dt>
<dt>
<span class="index">
<a href="dynindex-function.html">
Function Index
</a>
</span>
</dt>
<dt>
<span class="index">
<a href="dynindex-is.html">
INFORMATION_SCHEMA Index
</a>
</span>
</dt>
<dt>
<span class="index">
<a href="dynindex-jointype.html">
Join Types Index
</a>
</span>
</dt>
<dt>
<span class="index">
<a href="dynindex-operator.html">
Operator Index
</a>
</span>
</dt>
<dt>
<span class="index">
<a href="dynindex-option.html">
Option Index
</a>
</span>
</dt>
<dt>
<span class="index">
<a href="dynindex-priv.html">
Privileges Index
</a>
</span>
</dt>
<dt>
<span class="index">
<a href="dynindex-sqlmode.html">
SQL Modes Index
</a>
</span>
</dt>
<dt>
<span class="index">
<a href="dynindex-statement.html">
Statement/Syntax Index
</a>
</span>
</dt>
<dt>
<span class="index">
<a href="dynindex-statvar.html">
Status Variable Index
</a>
</span>
</dt>
<dt>
<span class="index">
<a href="dynindex-sysvar.html">
System Variable Index
</a>
</span>
</dt>
<dt>
<span class="index">
<a href="dynindex-isolevel.html">
Transaction Isolation Level Index
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="glossary">
<a href="glossary.html">
MySQL Glossary
</a>
</span>
</dt>
</dl>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/using-mysqldump.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h2 class="title">
<a name="using-mysqldump">
</a>
9.4 Using mysqldump for Backups
</h2>
</div>
</div>
</div>
<div class="toc">
<dl class="toc">
<dt>
<span class="section">
<a href="mysqldump-sql-format.html">
9.4.1 Dumping Data in SQL Format with mysqldump
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="reloading-sql-format-dumps.html">
9.4.2 Reloading SQL-Format Backups
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysqldump-delimited-text.html">
9.4.3 Dumping Data in Delimited-Text Format with mysqldump
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="reloading-delimited-text-dumps.html">
9.4.4 Reloading Delimited-Text Format Backups
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysqldump-tips.html">
9.4.5 mysqldump Tips
</a>
</span>
</dt>
</dl>
</div>
<a class="indexterm" name="idm46045231112928">
</a>
<a class="indexterm" name="idm46045231111472">
</a>
<div class="tip" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Tip
</div>
<p>
Consider using the
<a class="ulink" href="/doc/mysql-shell/8.4/en/mysql-shell-utilities-dump-instance-schema.html" target="_top">
MySQL Shell dump utilities
</a>
, which provide parallel dumping with multiple threads, file compression, and progress information display, as well as cloud features such as Oracle Cloud Infrastructure Object Storage streaming, and MySQL HeatWave Service compatibility checks and modifications. Dumps can be easily imported into a MySQL Server instance or a MySQL HeatWave Service DB System using the
<a class="ulink" href="/doc/mysql-shell/8.4/en/mysql-shell-utilities-load-dump.html" target="_top">
MySQL Shell load dump utilities
</a>
. Installation instructions for MySQL Shell can be found
<a class="ulink" href="/doc/mysql-shell/8.4/en/mysql-shell-install.html" target="_top">
here
</a>
.
</p>
</div>
<p>
This section describes how to use
<a class="link" href="mysqldump.html" title="6.5.4 mysqldump — A Database Backup Program">
<span class="command">
<strong>
mysqldump
</strong>
</span>
</a>
to
produce dump files, and how to reload dump files. A dump file can
be used in several ways:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
As a backup to enable data recovery in case of data loss.
</p>
</li>
<li class="listitem">
<p>
As a source of data for setting up replicas.
</p>
</li>
<li class="listitem">
<p>
As a source of data for experimentation:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
To make a copy of a database that you can use without
changing the original data.
</p>
</li>
<li class="listitem">
<p>
To test potential upgrade incompatibilities.
</p>
</li>
</ul>
</div>
</li>
</ul>
</div>
<p>
<a class="link" href="mysqldump.html" title="6.5.4 mysqldump — A Database Backup Program">
<span class="command">
<strong>
mysqldump
</strong>
</span>
</a>
produces two types of output,
depending on whether the
<a class="link" href="mysqldump.html#option_mysqldump_tab">
<code class="option">
--tab
</code>
</a>
option is given:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
Without
<a class="link" href="mysqldump.html#option_mysqldump_tab">
<code class="option">
--tab
</code>
</a>
,
<a class="link" href="mysqldump.html" title="6.5.4 mysqldump — A Database Backup Program">
<span class="command">
<strong>
mysqldump
</strong>
</span>
</a>
writes SQL statements to the
standard output. This output consists of
<code class="literal">
CREATE
</code>
statements to create dumped objects
(databases, tables, stored routines, and so forth), and
<code class="literal">
INSERT
</code>
statements to load data into tables.
The output can be saved in a file and reloaded later using
<a class="link" href="mysql.html" title="6.5.1 mysql — The MySQL Command-Line Client">
<span class="command">
<strong>
mysql
</strong>
</span>
</a>
to recreate the dumped objects.
Options are available to modify the format of the SQL
statements, and to control which objects are dumped.
</p>
</li>
<li class="listitem">
<p>
With
<a class="link" href="mysqldump.html#option_mysqldump_tab">
<code class="option">
--tab
</code>
</a>
,
<a class="link" href="mysqldump.html" title="6.5.4 mysqldump — A Database Backup Program">
<span class="command">
<strong>
mysqldump
</strong>
</span>
</a>
produces two output files for
each dumped table. The server writes one file as tab-delimited
text, one line per table row. This file is named
<code class="filename">
<em class="replaceable">
<code>
tbl_name
</code>
</em>
.txt
</code>
in the output directory. The server also sends a
<a class="link" href="create-table.html" title="15.1.20 CREATE TABLE Statement">
<code class="literal">
CREATE TABLE
</code>
</a>
statement for the
table to
<a class="link" href="mysqldump.html" title="6.5.4 mysqldump — A Database Backup Program">
<span class="command">
<strong>
mysqldump
</strong>
</span>
</a>
, which writes it as a
file named
<code class="filename">
<em class="replaceable">
<code>
tbl_name
</code>
</em>
.sql
</code>
in the output directory.
</p>
</li>
</ul>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/general-installation-issues.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h2 class="title">
<a name="general-installation-issues">
</a>
2.1 General Installation Guidance
</h2>
</div>
</div>
</div>
<div class="toc">
<dl class="toc">
<dt>
<span class="section">
<a href="platform-support.html">
2.1.1 Supported Platforms
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="which-version.html">
2.1.2 Which MySQL Version and Distribution to Install
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="getting-mysql.html">
2.1.3 How to Get MySQL
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="verifying-package-integrity.html">
2.1.4 Verifying Package Integrity Using MD5 Checksums or GnuPG
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="installation-layouts.html">
2.1.5 Installation Layouts
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="compiler-characteristics.html">
2.1.6 Compiler-Specific Build Characteristics
</a>
</span>
</dt>
</dl>
</div>
<p>
The immediately following sections contain the information necessary
to choose, download, and verify your distribution. The instructions
in later sections of the chapter describe how to install the
distribution that you choose. For binary distributions, see the
instructions at
<a class="xref" href="binary-installation.html" title="2.2 Installing MySQL on Unix/Linux Using Generic Binaries">
Section 2.2, “Installing MySQL on Unix/Linux Using Generic Binaries”
</a>
or the
corresponding section for your platform if available. To build MySQL
from source, use the instructions in
<a class="xref" href="source-installation.html" title="2.8 Installing MySQL from Source">
Section 2.8, “Installing MySQL from Source”
</a>
.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/sys-table-exists.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="sys-table-exists">
</a>
30.4.4.26 The table_exists() Procedure
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045061087728">
</a>
<a class="indexterm" name="idm46045061086256">
</a>
<p>
Tests whether a given table exists as a regular table, a
<code class="literal">
TEMPORARY
</code>
table, or a view. The procedure
returns the table type in an
<code class="literal">
OUT
</code>
parameter.
If both a temporary and a permanent table exist with the given
name,
<code class="literal">
TEMPORARY
</code>
is returned.
</p>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h5 class="title">
<a name="sys-table-exists-parameters">
</a>
Parameters
</h5>
</div>
</div>
</div>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<code class="literal">
in_db VARCHAR(64)
</code>
: The name of the
database in which to check for table existence.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
in_table VARCHAR(64)
</code>
: The name of the
table to check the existence of.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
out_exists ENUM('', 'BASE TABLE', 'VIEW',
'TEMPORARY')
</code>
: The return value. This is an
<code class="literal">
OUT
</code>
parameter, so it must be a
variable into which the table type can be stored. When
the procedure returns, the variable has one of the
following values to indicate whether the table exists:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
<code class="literal">
''
</code>
: The table name does not exist
as a base table,
<code class="literal">
TEMPORARY
</code>
table,
or view.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
BASE TABLE
</code>
: The table name exists
as a base (permanent) table.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
VIEW
</code>
: The table name exists as a
view.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
TEMPORARY
</code>
: The table name exists
as a
<code class="literal">
TEMPORARY
</code>
table.
</p>
</li>
</ul>
</div>
</li>
</ul>
</div>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h5 class="title">
<a name="sys-table-exists-example">
</a>
Example
</h5>
</div>
</div>
</div>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa75778984"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">CREATE</span> <span class="token keyword">DATABASE</span> db1<span class="token punctuation">;</span>
<span class="token output">Query OK, 1 row affected (0.01 sec)</span>
<span class="token prompt">mysql></span> <span class="token keyword">USE</span> db1<span class="token punctuation">;</span>
<span class="token keyword">Database</span> <span class="token keyword">changed</span>
<span class="token prompt">mysql></span> <span class="token keyword">CREATE</span> <span class="token keyword">TABLE</span> t1 <span class="token punctuation">(</span>id <span class="token datatype">INT</span> <span class="token keyword">PRIMARY</span> <span class="token keyword">KEY</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output">Query OK, 0 rows affected (0.03 sec)</span>
<span class="token prompt">mysql></span> <span class="token keyword">CREATE</span> <span class="token keyword">TABLE</span> t2 <span class="token punctuation">(</span>id <span class="token datatype">INT</span> <span class="token keyword">PRIMARY</span> <span class="token keyword">KEY</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output">Query OK, 0 rows affected (0.20 sec)</span>
<span class="token prompt">mysql></span> <span class="token keyword">CREATE</span> <span class="token keyword">view</span> v_t1 <span class="token keyword">AS</span> <span class="token keyword">SELECT</span> <span class="token operator">*</span> <span class="token keyword">FROM</span> t1<span class="token punctuation">;</span>
<span class="token output">Query OK, 0 rows affected (0.02 sec)</span>
<span class="token prompt">mysql></span> <span class="token keyword">CREATE</span> <span class="token keyword">TEMPORARY</span> <span class="token keyword">TABLE</span> t1 <span class="token punctuation">(</span>id <span class="token datatype">INT</span> <span class="token keyword">PRIMARY</span> <span class="token keyword">KEY</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output">Query OK, 0 rows affected (0.00 sec)</span>
<span class="token prompt">mysql></span> <span class="token keyword">CALL</span> sys<span class="token punctuation">.</span>table_exists<span class="token punctuation">(</span><span class="token string">'db1'</span><span class="token punctuation">,</span> <span class="token string">'t1'</span><span class="token punctuation">,</span> <span class="token variable">@exists</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token keyword">SELECT</span> <span class="token variable">@exists</span><span class="token punctuation">;</span>
<span class="token output">Query OK, 0 rows affected (0.01 sec)</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> @exists <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> TEMPORARY <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output">1 row in set (0.00 sec)</span>
<span class="token prompt">mysql></span> <span class="token keyword">CALL</span> sys<span class="token punctuation">.</span>table_exists<span class="token punctuation">(</span><span class="token string">'db1'</span><span class="token punctuation">,</span> <span class="token string">'t2'</span><span class="token punctuation">,</span> <span class="token variable">@exists</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token keyword">SELECT</span> <span class="token variable">@exists</span><span class="token punctuation">;</span>
<span class="token output">Query OK, 0 rows affected (0.02 sec)</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> @exists <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> BASE TABLE <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output">1 row in set (0.00 sec)</span>
<span class="token prompt">mysql></span> <span class="token keyword">CALL</span> sys<span class="token punctuation">.</span>table_exists<span class="token punctuation">(</span><span class="token string">'db1'</span><span class="token punctuation">,</span> <span class="token string">'v_t1'</span><span class="token punctuation">,</span> <span class="token variable">@exists</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token keyword">SELECT</span> <span class="token variable">@exists</span><span class="token punctuation">;</span>
<span class="token output">Query OK, 0 rows affected (0.02 sec)</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> @exists <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> VIEW <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output">1 row in set (0.00 sec)</span>
<span class="token prompt">mysql></span> <span class="token keyword">CALL</span> sys<span class="token punctuation">.</span>table_exists<span class="token punctuation">(</span><span class="token string">'db1'</span><span class="token punctuation">,</span> <span class="token string">'t3'</span><span class="token punctuation">,</span> <span class="token variable">@exists</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token keyword">SELECT</span> <span class="token variable">@exists</span><span class="token punctuation">;</span>
<span class="token output">Query OK, 0 rows affected (0.00 sec)</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> @exists <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output">1 row in set (0.00 sec)</span></code></pre>
</div>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/mysql-cluster-params-other.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="mysql-cluster-params-other">
</a>
25.4.2.4 Other NDB Cluster Configuration Parameters
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045121392848">
</a>
<a class="indexterm" name="idm46045121391392">
</a>
<a class="indexterm" name="idm46045121390304">
</a>
<a class="indexterm" name="idm46045121389232">
</a>
<p>
The listings in this section provide information about
parameters used in the
<code class="literal">
[computer]
</code>
,
<code class="literal">
[tcp]
</code>
, and
<code class="literal">
[shm]
</code>
sections
of a
<code class="filename">
config.ini
</code>
file for configuring NDB
Cluster. For detailed descriptions and additional information
about individual parameters, see
<a class="xref" href="mysql-cluster-tcp-definition.html" title="25.4.3.10 NDB Cluster TCP/IP Connections">
Section 25.4.3.10, “NDB Cluster TCP/IP Connections”
</a>
, or
<a class="xref" href="mysql-cluster-shm-definition.html" title="25.4.3.12 NDB Cluster Shared-Memory Connections">
Section 25.4.3.12, “NDB Cluster Shared-Memory Connections”
</a>
, as appropriate.
</p>
<p>
The following parameters apply to the
<code class="filename">
config.ini
</code>
file's
<code class="literal">
[computer]
</code>
section:
</p>
<div class="itemizedlist">
<a name="ndbparam-summary-list-computer">
</a>
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-computer-definition.html#ndbparam-computer-hostname">
HostName
</a>
</code>
:
Host name or IP address of this computer.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-computer-definition.html#ndbparam-computer-id">
Id
</a>
</code>
:
Unique identifier for this computer.
</p>
</li>
</ul>
</div>
<p>
The following parameters apply to the
<code class="filename">
config.ini
</code>
file's
<code class="literal">
[tcp]
</code>
section:
</p>
<div class="itemizedlist">
<a name="ndbparam-summary-list-tcp">
</a>
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-tcp-definition.html#ndbparam-tcp-allowunresolvedhostnames">
AllowUnresolvedHostNames
</a>
</code>
:
When false (default), failure by management node to resolve
host name results in fatal error; when true, unresolved host
names are reported as warnings only.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-tcp-definition.html#ndbparam-tcp-checksum">
Checksum
</a>
</code>
:
If checksum is enabled, all signals between nodes are
checked for errors.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-tcp-definition.html#ndbparam-tcp-group">
Group
</a>
</code>
:
Used for group proximity; smaller value is interpreted as
being closer.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-tcp-definition.html#ndbparam-tcp-hostname1">
HostName1
</a>
</code>
:
Name or IP address of first of two computers joined by TCP
connection.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-tcp-definition.html#ndbparam-tcp-hostname2">
HostName2
</a>
</code>
:
Name or IP address of second of two computers joined by TCP
connection.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-tcp-definition.html#ndbparam-tcp-nodeid1">
NodeId1
</a>
</code>
:
ID of node (data node, API node, or management node) on one
side of connection.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-tcp-definition.html#ndbparam-tcp-nodeid2">
NodeId2
</a>
</code>
:
ID of node (data node, API node, or management node) on one
side of connection.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-tcp-definition.html#ndbparam-tcp-nodeidserver">
NodeIdServer
</a>
</code>
:
Set server side of TCP connection.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-tcp-definition.html#ndbparam-tcp-overloadlimit">
OverloadLimit
</a>
</code>
:
When more than this many unsent bytes are in send buffer,
connection is considered overloaded.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-tcp-definition.html#ndbparam-tcp-preferipversion">
PreferIPVersion
</a>
</code>
:
Indicate DNS resolver preference for IP version 4 or 6.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-tcp-definition.html#ndbparam-tcp-presendchecksum">
PreSendChecksum
</a>
</code>
:
If this parameter and Checksum are both enabled, perform
pre-send checksum checks, and check all TCP signals between
nodes for errors.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-tcp-definition.html#ndbparam-tcp-proxy">
Proxy
</a>
</code>
:
....
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-tcp-definition.html#ndbparam-tcp-receivebuffermemory">
ReceiveBufferMemory
</a>
</code>
:
Bytes of buffer for signals received by this node.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-tcp-definition.html#ndbparam-tcp-requirelinktls">
RequireLinkTls
</a>
</code>
:
Read-only; is set to true if either endpoint of this
connection requires TLS.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-tcp-definition.html#ndbparam-tcp-sendbuffermemory">
SendBufferMemory
</a>
</code>
:
Bytes of TCP buffer for signals sent from this node.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-tcp-definition.html#ndbparam-tcp-sendsignalid">
SendSignalId
</a>
</code>
:
Sends ID in each signal. Used in trace files. Defaults to
true in debug builds.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-tcp-definition.html#ndbparam-tcp-tcpspintime">
TcpSpinTime
</a>
</code>
:
Time to spin before going to sleep when receiving.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-tcp-definition.html#ndbparam-tcp-tcp_maxseg_size">
TCP_MAXSEG_SIZE
</a>
</code>
:
Value used for TCP_MAXSEG.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-tcp-definition.html#ndbparam-tcp-tcp_rcv_buf_size">
TCP_RCV_BUF_SIZE
</a>
</code>
:
Value used for SO_RCVBUF.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-tcp-definition.html#ndbparam-tcp-tcp_snd_buf_size">
TCP_SND_BUF_SIZE
</a>
</code>
:
Value used for SO_SNDBUF.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-tcp-definition.html#ndbparam-tcp-tcpbind_inaddr_any">
TcpBind_INADDR_ANY
</a>
</code>
:
Bind InAddrAny instead of host name for server part of
connection.
</p>
</li>
</ul>
</div>
<p>
The following parameters apply to the
<code class="filename">
config.ini
</code>
file's
<code class="literal">
[shm]
</code>
section:
</p>
<div class="itemizedlist">
<a name="ndbparam-summary-list-shm">
</a>
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-shm-definition.html#ndbparam-shm-checksum">
Checksum
</a>
</code>
:
If checksum is enabled, all signals between nodes are
checked for errors.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-shm-definition.html#ndbparam-shm-group">
Group
</a>
</code>
:
Used for group proximity; smaller value is interpreted as
being closer.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-shm-definition.html#ndbparam-shm-hostname1">
HostName1
</a>
</code>
:
Name or IP address of first of two computers joined by SHM
connection.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-shm-definition.html#ndbparam-shm-hostname2">
HostName2
</a>
</code>
:
Name or IP address of second of two computers joined by SHM
connection.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-shm-definition.html#ndbparam-shm-nodeid1">
NodeId1
</a>
</code>
:
ID of node (data node, API node, or management node) on one
side of connection.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-shm-definition.html#ndbparam-shm-nodeid2">
NodeId2
</a>
</code>
:
ID of node (data node, API node, or management node) on one
side of connection.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-shm-definition.html#ndbparam-shm-nodeidserver">
NodeIdServer
</a>
</code>
:
Set server side of SHM connection.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-shm-definition.html#ndbparam-shm-overloadlimit">
OverloadLimit
</a>
</code>
:
When more than this many unsent bytes are in send buffer,
connection is considered overloaded.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-shm-definition.html#ndbparam-shm-presendchecksum">
PreSendChecksum
</a>
</code>
:
If this parameter and Checksum are both enabled, perform
pre-send checksum checks, and check all SHM signals between
nodes for errors.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-shm-definition.html#ndbparam-shm-sendbuffermemory">
SendBufferMemory
</a>
</code>
:
Bytes in shared memory buffer for signals sent from this
node.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-shm-definition.html#ndbparam-shm-sendsignalid">
SendSignalId
</a>
</code>
:
Sends ID in each signal. Used in trace files.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-shm-definition.html#ndbparam-shm-shmkey">
ShmKey
</a>
</code>
:
Shared memory key; when set to 1, this is calculated by NDB.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-shm-definition.html#ndbparam-shm-shmspintime">
ShmSpinTime
</a>
</code>
:
When receiving, number of microseconds to spin before
sleeping.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-shm-definition.html#ndbparam-shm-shmsize">
ShmSize
</a>
</code>
:
Size of shared memory segment.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-shm-definition.html#ndbparam-shm-signum">
Signum
</a>
</code>
:
Signal number to be used for signalling.
</p>
</li>
</ul>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/performance-schema-rwlock-instances-table.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="performance-schema-rwlock-instances-table">
</a>
29.12.3.4 The rwlock_instances Table
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045073490960">
</a>
<a class="indexterm" name="idm46045073489472">
</a>
<p>
The
<a class="link" href="performance-schema-rwlock-instances-table.html" title="29.12.3.4 The rwlock_instances Table">
<code class="literal">
rwlock_instances
</code>
</a>
table lists
all the
<a class="link" href="glossary.html#glos_rw_lock" title="rw-lock">
rwlock
</a>
(read write
lock) instances seen by the Performance Schema while the
server executes. An
<code class="literal">
rwlock
</code>
is a
synchronization mechanism used in the code to enforce that
threads at a given time can have access to some common
resource following certain rules. The resource is said to be
<span class="quote">
“
<span class="quote">
protected
</span>
”
</span>
by the
<code class="literal">
rwlock
</code>
. The
access is either shared (many threads can have a read lock at
the same time), exclusive (only one thread can have a write
lock at a given time), or shared-exclusive (a thread can have
a write lock while permitting inconsistent reads by other
threads). Shared-exclusive access is otherwise known as an
<code class="literal">
sxlock
</code>
and optimizes concurrency and
improves scalability for read-write workloads.
</p>
<p>
Depending on how many threads are requesting a lock, and the
nature of the locks requested, access can be either granted in
shared mode, exclusive mode, shared-exclusive mode or not
granted at all, waiting for other threads to finish first.
</p>
<p>
The
<a class="link" href="performance-schema-rwlock-instances-table.html" title="29.12.3.4 The rwlock_instances Table">
<code class="literal">
rwlock_instances
</code>
</a>
table has
these columns:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<code class="literal">
NAME
</code>
</p>
<p>
The instrument name associated with the lock.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
OBJECT_INSTANCE_BEGIN
</code>
</p>
<p>
The address in memory of the instrumented lock.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
WRITE_LOCKED_BY_THREAD_ID
</code>
</p>
<p>
When a thread currently has an
<code class="literal">
rwlock
</code>
locked in exclusive (write) mode,
<code class="literal">
WRITE_LOCKED_BY_THREAD_ID
</code>
is the
<code class="literal">
THREAD_ID
</code>
of the locking thread,
otherwise it is
<code class="literal">
NULL
</code>
.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
READ_LOCKED_BY_COUNT
</code>
</p>
<p>
When a thread currently has an
<code class="literal">
rwlock
</code>
locked in shared (read) mode,
<code class="literal">
READ_LOCKED_BY_COUNT
</code>
is incremented by
1. This is a counter only, so it cannot be used directly
to find which thread holds a read lock, but it can be used
to see whether there is a read contention on an
<code class="literal">
rwlock
</code>
, and see how many readers are
currently active.
</p>
</li>
</ul>
</div>
<p>
The
<a class="link" href="performance-schema-rwlock-instances-table.html" title="29.12.3.4 The rwlock_instances Table">
<code class="literal">
rwlock_instances
</code>
</a>
table has
these indexes:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
Primary key on (
<code class="literal">
OBJECT_INSTANCE_BEGIN
</code>
)
</p>
</li>
<li class="listitem">
<p>
Index on (
<code class="literal">
NAME
</code>
)
</p>
</li>
<li class="listitem">
<p>
Index on (
<code class="literal">
WRITE_LOCKED_BY_THREAD_ID
</code>
)
</p>
</li>
</ul>
</div>
<p>
<a class="link" href="truncate-table.html" title="15.1.37 TRUNCATE TABLE Statement">
<code class="literal">
TRUNCATE TABLE
</code>
</a>
is not permitted
for the
<a class="link" href="performance-schema-rwlock-instances-table.html" title="29.12.3.4 The rwlock_instances Table">
<code class="literal">
rwlock_instances
</code>
</a>
table.
</p>
<p>
By performing queries on both of the following tables, a
monitoring application or a DBA may detect some bottlenecks or
deadlocks between threads that involve locks:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<a class="link" href="performance-schema-events-waits-current-table.html" title="29.12.4.1 The events_waits_current Table">
<code class="literal">
events_waits_current
</code>
</a>
, to see
what
<code class="literal">
rwlock
</code>
a thread is waiting for
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="performance-schema-rwlock-instances-table.html" title="29.12.3.4 The rwlock_instances Table">
<code class="literal">
rwlock_instances
</code>
</a>
, to see
which other thread currently owns an
<code class="literal">
rwlock
</code>
</p>
</li>
</ul>
</div>
<p>
There is a limitation: The
<a class="link" href="performance-schema-rwlock-instances-table.html" title="29.12.3.4 The rwlock_instances Table">
<code class="literal">
rwlock_instances
</code>
</a>
can be used only
to identify the thread holding a write lock, but not the
threads holding a read lock.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/group-replication-functions-for-maximum-consensus.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="group-replication-functions-for-maximum-consensus">
</a>
14.18.1.3 Functions to Inspect and Configure the Maximum Consensus Instances of a
Group
</h4>
</div>
</div>
</div>
<p>
The following functions enable you to inspect and configure
the maximum number of consensus instances that a group can
execute in parallel.
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<a name="function_group-replication-get-write-concurrency">
</a>
<a class="link" href="group-replication-functions-for-maximum-consensus.html#function_group-replication-get-write-concurrency">
<code class="literal">
group_replication_get_write_concurrency()
</code>
</a>
</p>
<a class="indexterm" name="idm46045193840688">
</a>
<a class="indexterm" name="idm46045193839584">
</a>
<p>
Check the maximum number of consensus instances that a
group can execute in parallel.
</p>
<p>
Syntax:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-clike"><div class="docs-select-all right" id="sa47727355"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-clike">INT <span class="token function">group_replication_get_write_concurrency</span><span class="token punctuation">(</span><span class="token punctuation">)</span></code></pre>
</div>
<p>
This function has no parameters.
</p>
<p>
Return value:
</p>
<p>
The maximum number of consensus instances currently set
for the group.
</p>
<p>
Example:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa77872663"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SELECT</span> group_replication_get_write_concurrency<span class="token punctuation">(</span><span class="token punctuation">)</span></code></pre>
</div>
<p>
For more information, see
<a class="xref" href="group-replication-group-write-consensus.html" title="20.5.1.3 Using Group Replication Group Write Consensus">
Section 20.5.1.3, “Using Group Replication Group Write Consensus”
</a>
.
</p>
</li>
<li class="listitem">
<p>
<a name="function_group-replication-set-write-concurrency">
</a>
<a class="link" href="group-replication-functions-for-maximum-consensus.html#function_group-replication-set-write-concurrency">
<code class="literal">
group_replication_set_write_concurrency()
</code>
</a>
</p>
<a class="indexterm" name="idm46045193829392">
</a>
<a class="indexterm" name="idm46045193828288">
</a>
<p>
Configures the maximum number of consensus instances that
a group can execute in parallel. The
<a class="link" href="privileges-provided.html#priv_group-replication-admin">
<code class="literal">
GROUP_REPLICATION_ADMIN
</code>
</a>
privilege is required to use this function.
</p>
<p>
Syntax:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-clike"><div class="docs-select-all right" id="sa26475990"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-clike">STRING <span class="token function">group_replication_set_write_concurrency</span><span class="token punctuation">(</span><em class="replaceable">instances</em><span class="token punctuation">)</span></code></pre>
</div>
<p>
Arguments:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
<em class="replaceable">
<code>
members
</code>
</em>
: Sets the maximum
number of consensus instances that a group can execute
in parallel. Default value is 10, valid values are
integers in the range of 10 to 200.
</p>
</li>
</ul>
</div>
<p>
Return value:
</p>
<p>
Any resulting error as a string.
</p>
<p>
Example:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa38612973"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SELECT</span> group_replication_set_write_concurrency<span class="token punctuation">(</span><em class="replaceable">instances</em><span class="token punctuation">)</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
For more information, see
<a class="xref" href="group-replication-group-write-consensus.html" title="20.5.1.3 Using Group Replication Group Write Consensus">
Section 20.5.1.3, “Using Group Replication Group Write Consensus”
</a>
.
</p>
</li>
</ul>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/alter-resource-group.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="alter-resource-group">
</a>
15.7.2.1 ALTER RESOURCE GROUP Statement
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045172845712">
</a>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa60824122"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">ALTER</span> <span class="token keyword">RESOURCE</span> <span class="token keyword">GROUP</span> <em class="replaceable">group_name</em>
<span class="token punctuation">[</span><span class="token keyword">VCPU</span> <span class="token punctuation">[</span><span class="token operator">=</span><span class="token punctuation">]</span> <em class="replaceable">vcpu_spec</em> <span class="token punctuation">[</span><span class="token punctuation">,</span> <em class="replaceable">vcpu_spec</em><span class="token punctuation">]</span> <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">]</span>
<span class="token punctuation">[</span><span class="token keyword">THREAD_PRIORITY</span> <span class="token punctuation">[</span><span class="token operator">=</span><span class="token punctuation">]</span> <em class="replaceable">N</em><span class="token punctuation">]</span>
<span class="token punctuation">[</span><span class="token keyword">ENABLE</span><span class="token operator">|</span><span class="token keyword">DISABLE</span> <span class="token punctuation">[</span><span class="token keyword">FORCE</span><span class="token punctuation">]</span><span class="token punctuation">]</span>
<em class="replaceable">vcpu_spec</em>: {<em class="replaceable">N</em> <span class="token operator">|</span> <em class="replaceable">M</em> <span class="token operator">-</span> <em class="replaceable">N</em>}</code></pre>
</div>
<p>
<a class="link" href="alter-resource-group.html" title="15.7.2.1 ALTER RESOURCE GROUP Statement">
<code class="literal">
ALTER RESOURCE GROUP
</code>
</a>
is used for
resource group management (see
<a class="xref" href="resource-groups.html" title="7.1.16 Resource Groups">
Section 7.1.16, “Resource Groups”
</a>
). This statement alters
modifiable attributes of an existing resource group. It requires
the
<a class="link" href="privileges-provided.html#priv_resource-group-admin">
<code class="literal">
RESOURCE_GROUP_ADMIN
</code>
</a>
privilege.
</p>
<p>
<em class="replaceable">
<code>
group_name
</code>
</em>
identifies which resource
group to alter. If the group does not exist, an error occurs.
</p>
<p>
The attributes for CPU affinity, priority, and whether the group
is enabled can be modified with
<a class="link" href="alter-resource-group.html" title="15.7.2.1 ALTER RESOURCE GROUP Statement">
<code class="literal">
ALTER
RESOURCE GROUP
</code>
</a>
. These attributes are specified the
same way as described for
<a class="link" href="create-resource-group.html" title="15.7.2.2 CREATE RESOURCE GROUP Statement">
<code class="literal">
CREATE RESOURCE
GROUP
</code>
</a>
(see
<a class="xref" href="create-resource-group.html" title="15.7.2.2 CREATE RESOURCE GROUP Statement">
Section 15.7.2.2, “CREATE RESOURCE GROUP Statement”
</a>
).
Only the attributes specified are altered. Unspecified
attributes retain their current values.
</p>
<p>
The
<code class="literal">
FORCE
</code>
modifier is used with
<code class="literal">
DISABLE
</code>
. It determines statement behavior if
the resource group has any threads assigned to it:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
If
<code class="literal">
FORCE
</code>
is not given, existing threads
in the group continue to run until they terminate, but new
threads cannot be assigned to the group.
</p>
</li>
<li class="listitem">
<p>
If
<code class="literal">
FORCE
</code>
is given, existing threads in
the group are moved to their respective default group
(system threads to
<code class="literal">
SYS_default
</code>
, user
threads to
<code class="literal">
USR_default
</code>
).
</p>
</li>
</ul>
</div>
<p>
The name and type attributes are set at group creation time and
cannot be modified thereafter with
<a class="link" href="alter-resource-group.html" title="15.7.2.1 ALTER RESOURCE GROUP Statement">
<code class="literal">
ALTER
RESOURCE GROUP
</code>
</a>
.
</p>
<p>
Examples:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
Alter a group CPU affinity:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa28986253"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">ALTER</span> <span class="token keyword">RESOURCE</span> <span class="token keyword">GROUP</span> rg1 <span class="token keyword">VCPU</span> <span class="token operator">=</span> <span class="token number">0</span><span class="token operator">-</span><span class="token number">63</span><span class="token punctuation">;</span></code></pre>
</div>
</li>
<li class="listitem">
<p>
Alter a group thread priority:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa32295961"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">ALTER</span> <span class="token keyword">RESOURCE</span> <span class="token keyword">GROUP</span> rg2 <span class="token keyword">THREAD_PRIORITY</span> <span class="token operator">=</span> <span class="token number">5</span><span class="token punctuation">;</span></code></pre>
</div>
</li>
<li class="listitem">
<p>
Disable a group, moving any threads assigned to it to the
default groups:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa30097167"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">ALTER</span> <span class="token keyword">RESOURCE</span> <span class="token keyword">GROUP</span> rg3 <span class="token keyword">DISABLE</span> <span class="token keyword">FORCE</span><span class="token punctuation">;</span></code></pre>
</div>
</li>
</ul>
</div>
<p>
Resource group management is local to the server on which it
occurs.
<a class="link" href="alter-resource-group.html" title="15.7.2.1 ALTER RESOURCE GROUP Statement">
<code class="literal">
ALTER RESOURCE GROUP
</code>
</a>
statements are not written to the binary log and are not
replicated.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/group-replication-network-partitioning.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="group-replication-network-partitioning">
</a>
20.7.8 Handling a Network Partition and Loss of Quorum
</h3>
</div>
</div>
</div>
<a class="indexterm" name="idm46045131888752">
</a>
<p>
The group needs to achieve consensus whenever a change that needs
to be replicated happens. This is the case for regular
transactions but is also required for group membership changes and
some internal messaging that keeps the group consistent. Consensus
requires a majority of group members to agree on a given decision.
When a majority of group members is lost, the group is unable to
progress and blocks because it cannot secure majority or quorum.
</p>
<p>
Quorum may be lost when there are multiple involuntary failures,
causing a majority of servers to be removed abruptly from the
group. For example, in a group of 5 servers, if 3 of them become
silent at once, the majority is compromised and thus no quorum can
be achieved. In fact, the remaining two are not able to tell if
the other 3 servers have crashed or whether a network partition
has isolated these 2 alone and therefore the group cannot be
reconfigured automatically.
</p>
<p>
On the other hand, if servers exit the group voluntarily, they
instruct the group that it should reconfigure itself. In practice,
this means that a server that is leaving tells others that it is
going away. This means that other members can reconfigure the
group properly, the consistency of the membership is maintained
and the majority is recalculated. For example, in the above
scenario of 5 servers where 3 leave at once, if the 3 leaving
servers warn the group that they are leaving, one by one, then the
membership is able to adjust itself from 5 to 2, and at the same
time, securing quorum while that happens.
</p>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
Loss of quorum is by itself a side-effect of bad planning. Plan
the group size for the number of expected failures (regardless
whether they are consecutive, happen all at once or are
sporadic).
</p>
</div>
<p>
For a group in single-primary mode, the primary might have
transactions that are not yet present on other members at the time
of the network partition. If you are considering excluding the
primary from the new group, be aware that such transactions might
be lost. A member with extra transactions cannot rejoin the group,
and the attempt results in an error with the message
<span class="errortext">
This member has more executed transactions than those
present in the group
</span>
. Set the
<a class="link" href="group-replication-system-variables.html#sysvar_group_replication_unreachable_majority_timeout">
<code class="literal">
group_replication_unreachable_majority_timeout
</code>
</a>
system variable for the group members to avoid this situation.
</p>
<p>
The following sections explain what to do if the system partitions
in such a way that no quorum is automatically achieved by the
servers in the group.
</p>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h4 class="title">
<a name="group-replication-detecting-partitions">
</a>
Detecting Partitions
</h4>
</div>
</div>
</div>
<p>
The
<a class="link" href="performance-schema-replication-group-members-table.html" title="29.12.11.16 The replication_group_members Table">
<code class="literal">
replication_group_members
</code>
</a>
performance schema table presents the status of each server in
the current view from the perspective of this server. The
majority of the time the system does not run into partitioning,
and therefore the table shows information that is consistent
across all servers in the group. In other words, the status of
each server on this table is agreed by all in the current view.
However, if there is network partitioning, and quorum is lost,
then the table shows the status
<code class="literal">
UNREACHABLE
</code>
for those servers that it cannot contact. This information is
exported by the local failure detector built into Group
Replication.
</p>
<div class="figure">
<a name="idm46045131874944">
</a>
<p class="title">
<b>
Figure 20.14 Losing Quorum
</b>
</p>
<div class="figure-contents">
<div class="mediaobject">
<img alt="Five server instances, S1, S2, S3, S4, and S5, are deployed as an interconnected group, which is a stable group. When three of the servers, S3, S4, and S5, fail, the majority is lost and the group can no longer proceed without intervention." src="images/gr-majority-lost.png" style="width: 100%; max-width: 243px;"/>
</div>
</div>
</div>
<br class="figure-break"/>
<p>
To understand this type of network partition the following
section describes a scenario where there are initially 5 servers
working together correctly, and the changes that then happen to
the group once only 2 servers are online. The scenario is
depicted in the
figure.
</p>
<p>
As such, lets assume that there is a group with these 5 servers
in it:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
Server s1 with member identifier
<code class="literal">
199b2df7-4aaf-11e6-bb16-28b2bd168d07
</code>
</p>
</li>
<li class="listitem">
<p>
Server s2 with member identifier
<code class="literal">
199bb88e-4aaf-11e6-babe-28b2bd168d07
</code>
</p>
</li>
<li class="listitem">
<p>
Server s3 with member identifier
<code class="literal">
1999b9fb-4aaf-11e6-bb54-28b2bd168d07
</code>
</p>
</li>
<li class="listitem">
<p>
Server s4 with member identifier
<code class="literal">
19ab72fc-4aaf-11e6-bb51-28b2bd168d07
</code>
</p>
</li>
<li class="listitem">
<p>
Server s5 with member identifier
<code class="literal">
19b33846-4aaf-11e6-ba81-28b2bd168d07
</code>
</p>
</li>
</ul>
</div>
<p>
Initially the group is running fine and the servers are happily
communicating with each other. You can verify this by logging
into s1 and looking at its
<a class="link" href="performance-schema-replication-group-members-table.html" title="29.12.11.16 The replication_group_members Table">
<code class="literal">
replication_group_members
</code>
</a>
performance schema table. For example:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa5590121"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> MEMBER_ID<span class="token punctuation">,</span>MEMBER_STATE<span class="token punctuation">,</span> MEMBER_ROLE <span class="token keyword">FROM</span> performance_schema<span class="token punctuation">.</span>replication_group_members<span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> MEMBER_ID <span class="token punctuation">|</span> MEMBER_STATE <span class="token punctuation">|</span> MEMBER_ROLE <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 1999b9fb<span class="token punctuation">-</span>4aaf<span class="token punctuation">-</span>11e6<span class="token punctuation">-</span>bb54<span class="token punctuation">-</span>28b2bd168d07 <span class="token punctuation">|</span> ONLINE <span class="token punctuation">|</span> SECONDARY <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 199b2df7<span class="token punctuation">-</span>4aaf<span class="token punctuation">-</span>11e6<span class="token punctuation">-</span>bb16<span class="token punctuation">-</span>28b2bd168d07 <span class="token punctuation">|</span> ONLINE <span class="token punctuation">|</span> PRIMARY <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 199bb88e<span class="token punctuation">-</span>4aaf<span class="token punctuation">-</span>11e6<span class="token punctuation">-</span>babe<span class="token punctuation">-</span>28b2bd168d07 <span class="token punctuation">|</span> ONLINE <span class="token punctuation">|</span> SECONDARY <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 19ab72fc<span class="token punctuation">-</span>4aaf<span class="token punctuation">-</span>11e6<span class="token punctuation">-</span>bb51<span class="token punctuation">-</span>28b2bd168d07 <span class="token punctuation">|</span> ONLINE <span class="token punctuation">|</span> SECONDARY <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 19b33846<span class="token punctuation">-</span>4aaf<span class="token punctuation">-</span>11e6<span class="token punctuation">-</span>ba81<span class="token punctuation">-</span>28b2bd168d07 <span class="token punctuation">|</span> ONLINE <span class="token punctuation">|</span> SECONDARY <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
</div>
<p>
However, moments later there is a catastrophic failure and
servers s3, s4 and s5 stop unexpectedly. A few seconds after
this, looking again at the
<a class="link" href="performance-schema-replication-group-members-table.html" title="29.12.11.16 The replication_group_members Table">
<code class="literal">
replication_group_members
</code>
</a>
table on
s1 shows that it is still online, but several others members are
not. In fact, as seen below they are marked as
<code class="literal">
UNREACHABLE
</code>
. Moreover, the system could not
reconfigure itself to change the membership, because the
majority has been lost.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa81705083"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> MEMBER_ID<span class="token punctuation">,</span>MEMBER_STATE <span class="token keyword">FROM</span> performance_schema<span class="token punctuation">.</span>replication_group_members<span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> MEMBER_ID <span class="token punctuation">|</span> MEMBER_STATE <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 1999b9fb<span class="token punctuation">-</span>4aaf<span class="token punctuation">-</span>11e6<span class="token punctuation">-</span>bb54<span class="token punctuation">-</span>28b2bd168d07 <span class="token punctuation">|</span> UNREACHABLE <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 199b2df7<span class="token punctuation">-</span>4aaf<span class="token punctuation">-</span>11e6<span class="token punctuation">-</span>bb16<span class="token punctuation">-</span>28b2bd168d07 <span class="token punctuation">|</span> ONLINE <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 199bb88e<span class="token punctuation">-</span>4aaf<span class="token punctuation">-</span>11e6<span class="token punctuation">-</span>babe<span class="token punctuation">-</span>28b2bd168d07 <span class="token punctuation">|</span> ONLINE <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 19ab72fc<span class="token punctuation">-</span>4aaf<span class="token punctuation">-</span>11e6<span class="token punctuation">-</span>bb51<span class="token punctuation">-</span>28b2bd168d07 <span class="token punctuation">|</span> UNREACHABLE <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 19b33846<span class="token punctuation">-</span>4aaf<span class="token punctuation">-</span>11e6<span class="token punctuation">-</span>ba81<span class="token punctuation">-</span>28b2bd168d07 <span class="token punctuation">|</span> UNREACHABLE <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
</div>
<p>
The table shows that s1 is now in a group that has no means of
progressing without external intervention, because a majority of
the servers are unreachable. In this particular case, the group
membership list needs to be reset to allow the system to
proceed, which is explained in this section. Alternatively, you
could also choose to stop Group Replication on s1 and s2 (or
stop completely s1 and s2), figure out what happened with s3, s4
and s5 and then restart Group Replication (or the servers).
</p>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h4 class="title">
<a name="group-replication-unblocking-a-partition">
</a>
Unblocking a Partition
</h4>
</div>
</div>
</div>
<p>
Group replication enables you to reset the group membership list
by forcing a specific configuration. For instance in the case
above, where s1 and s2 are the only servers online, you could
choose to force a membership configuration consisting of only s1
and s2. This requires checking some information about s1 and s2
and then using the
<a class="link" href="group-replication-system-variables.html#sysvar_group_replication_force_members">
<code class="literal">
group_replication_force_members
</code>
</a>
variable.
</p>
<div class="figure">
<a name="idm46045131843632">
</a>
<p class="title">
<b>
Figure 20.15 Forcing a New Membership
</b>
</p>
<div class="figure-contents">
<div class="mediaobject">
<img alt="Three of the servers in a group, S3, S4, and S5, have failed, so the majority is lost and the group can no longer proceed without intervention. With the intervention described in the following text, S1 and S2 are able to form a stable group by themselves." src="images/gr-majority-lost-to-stable-group.png" style="width: 100%; max-width: 243px;"/>
</div>
</div>
</div>
<br class="figure-break"/>
<p>
Suppose that you are back in the situation where s1 and s2 are
the only servers left in the group. Servers s3, s4 and s5 have
left the group unexpectedly. To make servers s1 and s2 continue,
you want to force a membership configuration that contains only
s1 and s2.
</p>
<div class="warning" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Warning
</div>
<p>
This procedure uses
<a class="link" href="group-replication-system-variables.html#sysvar_group_replication_force_members">
<code class="literal">
group_replication_force_members
</code>
</a>
and should be considered a last resort remedy. It
<span class="emphasis">
<em>
must
</em>
</span>
be used with extreme care and only
for overriding loss of quorum. If misused, it could create an
artificial split-brain scenario or block the entire system
altogether.
</p>
</div>
<p>
When forcing a new membership configuration, make sure that any
servers are going to be forced out of the group are indeed
stopped. In the scenario depicted above, if s3, s4 and s5 are
not really unreachable but instead are online, they may have
formed their own functional partition (they are 3 out of 5,
hence they have the majority). In that case, forcing a group
membership list with s1 and s2 could create an artificial
split-brain situation. Therefore it is important before forcing
a new membership configuration to ensure that the servers to be
excluded are indeed shut down and if they are not, shut them
down before proceeding.
</p>
<div class="warning" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Warning
</div>
<p>
For a group in single-primary mode, the primary might have
transactions that are not yet present on other members at the
time of the network partition. If you are considering
excluding the primary from the new group, be aware that such
transactions might be lost. A member with extra transactions
cannot rejoin the group, and the attempt results in an error
with the message
<span class="errortext">
This member has more executed
transactions than those present in the group
</span>
. Set
the
<a class="link" href="group-replication-system-variables.html#sysvar_group_replication_unreachable_majority_timeout">
<code class="literal">
group_replication_unreachable_majority_timeout
</code>
</a>
system variable for the group members to avoid this situation.
</p>
</div>
<p>
Recall that the system is blocked and the current configuration
is the following (as perceived by the local failure detector on
s1):
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa45391294"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> MEMBER_ID<span class="token punctuation">,</span>MEMBER_STATE <span class="token keyword">FROM</span> performance_schema<span class="token punctuation">.</span>replication_group_members<span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> MEMBER_ID <span class="token punctuation">|</span> MEMBER_STATE <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 1999b9fb<span class="token punctuation">-</span>4aaf<span class="token punctuation">-</span>11e6<span class="token punctuation">-</span>bb54<span class="token punctuation">-</span>28b2bd168d07 <span class="token punctuation">|</span> UNREACHABLE <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 199b2df7<span class="token punctuation">-</span>4aaf<span class="token punctuation">-</span>11e6<span class="token punctuation">-</span>bb16<span class="token punctuation">-</span>28b2bd168d07 <span class="token punctuation">|</span> ONLINE <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 199bb88e<span class="token punctuation">-</span>4aaf<span class="token punctuation">-</span>11e6<span class="token punctuation">-</span>babe<span class="token punctuation">-</span>28b2bd168d07 <span class="token punctuation">|</span> ONLINE <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 19ab72fc<span class="token punctuation">-</span>4aaf<span class="token punctuation">-</span>11e6<span class="token punctuation">-</span>bb51<span class="token punctuation">-</span>28b2bd168d07 <span class="token punctuation">|</span> UNREACHABLE <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 19b33846<span class="token punctuation">-</span>4aaf<span class="token punctuation">-</span>11e6<span class="token punctuation">-</span>ba81<span class="token punctuation">-</span>28b2bd168d07 <span class="token punctuation">|</span> UNREACHABLE <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
</div>
<p>
The first thing to do is to check what is the local address
(group communication identifier) for s1 and s2. Log in to s1 and
s2 and get that information as follows.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa67979432"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token variable">@@group_replication_local_address</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
Once you know the group communication addresses of s1
(
<code class="literal">
127.0.0.1:10000
</code>
) and s2
(
<code class="literal">
127.0.0.1:10001
</code>
), you can use that on one of
the two servers to inject a new membership configuration, thus
overriding the existing one that has lost quorum. To do that on
s1:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa9550509"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SET</span> <span class="token keyword">GLOBAL</span> group_replication_force_members<span class="token operator">=</span><span class="token string">"127.0.0.1:10000,127.0.0.1:10001"</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
This unblocks the group by forcing a different configuration.
Check
<a class="link" href="performance-schema-replication-group-members-table.html" title="29.12.11.16 The replication_group_members Table">
<code class="literal">
replication_group_members
</code>
</a>
on
both s1 and s2 to verify the group membership after this change.
First on s1.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa41302978"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> MEMBER_ID<span class="token punctuation">,</span>MEMBER_STATE <span class="token keyword">FROM</span> performance_schema<span class="token punctuation">.</span>replication_group_members<span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> MEMBER_ID <span class="token punctuation">|</span> MEMBER_STATE <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> b5ffe505<span class="token punctuation">-</span>4ab6<span class="token punctuation">-</span>11e6<span class="token punctuation">-</span>b04b<span class="token punctuation">-</span>28b2bd168d07 <span class="token punctuation">|</span> ONLINE <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> b60907e7<span class="token punctuation">-</span>4ab6<span class="token punctuation">-</span>11e6<span class="token punctuation">-</span>afb7<span class="token punctuation">-</span>28b2bd168d07 <span class="token punctuation">|</span> ONLINE <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
</div>
<p>
And then on s2.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa64059566"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token operator">*</span> <span class="token keyword">FROM</span> performance_schema<span class="token punctuation">.</span>replication_group_members<span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> MEMBER_ID <span class="token punctuation">|</span> MEMBER_STATE <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> b5ffe505<span class="token punctuation">-</span>4ab6<span class="token punctuation">-</span>11e6<span class="token punctuation">-</span>b04b<span class="token punctuation">-</span>28b2bd168d07 <span class="token punctuation">|</span> ONLINE <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> b60907e7<span class="token punctuation">-</span>4ab6<span class="token punctuation">-</span>11e6<span class="token punctuation">-</span>afb7<span class="token punctuation">-</span>28b2bd168d07 <span class="token punctuation">|</span> ONLINE <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
</div>
<p>
After you have used the
<a class="link" href="group-replication-system-variables.html#sysvar_group_replication_force_members">
<code class="literal">
group_replication_force_members
</code>
</a>
system variable to successfully force a new group membership and
unblock the group, ensure that you clear the system variable.
<a class="link" href="group-replication-system-variables.html#sysvar_group_replication_force_members">
<code class="literal">
group_replication_force_members
</code>
</a>
must be empty in order to issue a
<a class="link" href="start-group-replication.html" title="15.4.3.1 START GROUP_REPLICATION Statement">
<code class="literal">
START
GROUP_REPLICATION
</code>
</a>
statement.
</p>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/optimize-character.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="optimize-character">
</a>
10.4.2.2 Optimizing for Character and String Types
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045226765424">
</a>
<p>
For character and string columns, follow these guidelines:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
Use binary collation order for fast comparison and sort
operations, when you do not need language-specific
collation features. You can use the
<a class="link" href="cast-functions.html#operator_binary">
<code class="literal">
BINARY
</code>
</a>
operator to use binary
collation within a particular query.
</p>
</li>
<li class="listitem">
<p>
When comparing values from different columns, declare
those columns with the same character set and collation
wherever possible, to avoid string conversions while
running the query.
</p>
</li>
<li class="listitem">
<p>
For column values less than 8KB in size, use binary
<code class="literal">
VARCHAR
</code>
instead of
<code class="literal">
BLOB
</code>
. The
<code class="literal">
GROUP BY
</code>
and
<code class="literal">
ORDER BY
</code>
clauses can generate
temporary tables, and these temporary tables can use the
<code class="literal">
MEMORY
</code>
storage engine if the original
table does not contain any
<code class="literal">
BLOB
</code>
columns.
</p>
</li>
<li class="listitem">
<p>
If a table contains string columns such as name and
address, but many queries do not retrieve those columns,
consider splitting the string columns into a separate
table and using join queries with a foreign key when
necessary. When MySQL retrieves any value from a row, it
reads a data block containing all the columns of that row
(and possibly other adjacent rows). Keeping each row
small, with only the most frequently used columns, allows
more rows to fit in each data block. Such compact tables
reduce disk I/O and memory usage for common queries.
</p>
</li>
<li class="listitem">
<p>
When you use a randomly generated value as a primary key
in an
<code class="literal">
InnoDB
</code>
table, prefix it with an
ascending value such as the current date and time if
possible. When consecutive primary values are physically
stored near each other,
<code class="literal">
InnoDB
</code>
can
insert and retrieve them faster.
</p>
</li>
<li class="listitem">
<p>
See
<a class="xref" href="optimize-numeric.html" title="10.4.2.1 Optimizing for Numeric Data">
Section 10.4.2.1, “Optimizing for Numeric Data”
</a>
for reasons why a
numeric column is usually preferable to an equivalent
string column.
</p>
</li>
</ul>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/symbolic-links-to-tables.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="symbolic-links-to-tables">
</a>
10.12.2.2 Using Symbolic Links for MyISAM Tables on Unix
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045222456288">
</a>
<a class="indexterm" name="idm46045222454800">
</a>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
Symbolic link support as described here, along with the
<a class="link" href="server-options.html#option_mysqld_symbolic-links">
<code class="option">
--symbolic-links
</code>
</a>
option that
controls it, and is deprecated; expect these to be removed
in a future version of MySQL. In addition, the option is
disabled by default.
</p>
</div>
<p>
Symlinks are fully supported only for
<code class="literal">
MyISAM
</code>
tables. For files used by tables for
other storage engines, you may get strange problems if you try
to use symbolic links. For
<code class="literal">
InnoDB
</code>
tables,
use the alternative technique explained in
<a class="xref" href="innodb-create-table-external.html" title="17.6.1.2 Creating Tables Externally">
Section 17.6.1.2, “Creating Tables Externally”
</a>
instead.
</p>
<p>
Do not symlink tables on systems that do not have a fully
operational
<code class="literal">
realpath()
</code>
call. (Linux and
Solaris support
<code class="literal">
realpath()
</code>
). To determine
whether your system supports symbolic links, check the value
of the
<a class="link" href="server-system-variables.html#sysvar_have_symlink">
<code class="literal">
have_symlink
</code>
</a>
system
variable using this statement:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa38333477"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SHOW</span> <span class="token keyword">VARIABLES</span> <span class="token operator">LIKE</span> <span class="token string">'have_symlink'</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
The handling of symbolic links for
<code class="literal">
MyISAM
</code>
tables works as follows:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
In the data directory, you always have the data
(
<code class="filename">
.MYD
</code>
) file and the index
(
<code class="filename">
.MYI
</code>
) file. The data file and index
file can be moved elsewhere and replaced in the data
directory by symlinks.
</p>
</li>
<li class="listitem">
<p>
You can symlink the data file and the index file
independently to different directories.
</p>
</li>
<li class="listitem">
<p>
To instruct a running MySQL server to perform the
symlinking, use the
<code class="literal">
DATA DIRECTORY
</code>
and
<code class="literal">
INDEX DIRECTORY
</code>
options to
<a class="link" href="create-table.html" title="15.1.20 CREATE TABLE Statement">
<code class="literal">
CREATE TABLE
</code>
</a>
. See
<a class="xref" href="create-table.html" title="15.1.20 CREATE TABLE Statement">
Section 15.1.20, “CREATE TABLE Statement”
</a>
. Alternatively, if
<a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
<span class="command">
<strong>
mysqld
</strong>
</span>
</a>
is not running, symlinking can
be accomplished manually using
<span class="command">
<strong>
ln -s
</strong>
</span>
from the command line.
</p>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
The path used with either or both of the
<code class="literal">
DATA
DIRECTORY
</code>
and
<code class="literal">
INDEX
DIRECTORY
</code>
options may not include the MySQL
<code class="literal">
data
</code>
directory. (Bug #32167)
</p>
</div>
</li>
<li class="listitem">
<p>
<a class="link" href="myisamchk.html" title="6.6.4 myisamchk — MyISAM Table-Maintenance Utility">
<span class="command">
<strong>
myisamchk
</strong>
</span>
</a>
does not replace a symlink
with the data file or index file. It works directly on the
file to which the symlink points. Any temporary files are
created in the directory where the data file or index file
is located. The same is true for the
<a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement">
<code class="literal">
ALTER TABLE
</code>
</a>
,
<a class="link" href="optimize-table.html" title="15.7.3.4 OPTIMIZE TABLE Statement">
<code class="literal">
OPTIMIZE TABLE
</code>
</a>
, and
<a class="link" href="repair-table.html" title="15.7.3.5 REPAIR TABLE Statement">
<code class="literal">
REPAIR TABLE
</code>
</a>
statements.
</p>
</li>
<li class="listitem">
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
When you drop a table that is using symlinks,
<span class="emphasis">
<em>
both the symlink and the file to which the
symlink points are dropped
</em>
</span>
. This is an
extremely good reason
<span class="emphasis">
<em>
not
</em>
</span>
to run
<a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
<span class="command">
<strong>
mysqld
</strong>
</span>
</a>
as the
<code class="literal">
root
</code>
operating system user or permit operating system users
to have write access to MySQL database directories.
</p>
</div>
</li>
<li class="listitem">
<p>
If you rename a table with
<a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement">
<code class="literal">
ALTER TABLE
... RENAME
</code>
</a>
or
<a class="link" href="rename-table.html" title="15.1.36 RENAME TABLE Statement">
<code class="literal">
RENAME
TABLE
</code>
</a>
and you do not move the table to another
database, the symlinks in the database directory are
renamed to the new names and the data file and index file
are renamed accordingly.
</p>
</li>
<li class="listitem">
<p>
If you use
<a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement">
<code class="literal">
ALTER TABLE
... RENAME
</code>
</a>
or
<a class="link" href="rename-table.html" title="15.1.36 RENAME TABLE Statement">
<code class="literal">
RENAME
TABLE
</code>
</a>
to move a table to another database, the
table is moved to the other database directory. If the
table name changed, the symlinks in the new database
directory are renamed to the new names and the data file
and index file are renamed accordingly.
</p>
</li>
<li class="listitem">
<p>
If you are not using symlinks, start
<a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
<span class="command">
<strong>
mysqld
</strong>
</span>
</a>
with the
<a class="link" href="server-options.html#option_mysqld_symbolic-links">
<code class="option">
--skip-symbolic-links
</code>
</a>
option to ensure that no one can use
<a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
<span class="command">
<strong>
mysqld
</strong>
</span>
</a>
to drop or rename a file outside
of the data directory.
</p>
</li>
</ul>
</div>
<p>
These table symlink operations are not supported:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement">
<code class="literal">
ALTER TABLE
</code>
</a>
ignores the
<code class="literal">
DATA DIRECTORY
</code>
and
<code class="literal">
INDEX
DIRECTORY
</code>
table options.
</p>
</li>
</ul>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/sys-schema-table-statistics-with-buffer.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="sys-schema-table-statistics-with-buffer">
</a>
30.4.3.30 The schema_table_statistics_with_buffer and
x$schema_table_statistics_with_buffer Views
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045062354896">
</a>
<a class="indexterm" name="idm46045062353376">
</a>
<a class="indexterm" name="idm46045062351856">
</a>
<a class="indexterm" name="idm46045062350336">
</a>
<p>
These views summarize table statistics, including
<code class="literal">
InnoDB
</code>
buffer pool statistics. By default,
rows are sorted by descending total wait time (tables with
most contention first).
</p>
<p>
These views user a helper view,
<code class="literal">
x$ps_schema_table_statistics_io
</code>
.
</p>
<p>
The
<a class="link" href="sys-schema-table-statistics-with-buffer.html" title="30.4.3.30 The schema_table_statistics_with_buffer and x$schema_table_statistics_with_buffer Views">
<code class="literal">
schema_table_statistics_with_buffer
</code>
</a>
and
<a class="link" href="sys-schema-table-statistics-with-buffer.html" title="30.4.3.30 The schema_table_statistics_with_buffer and x$schema_table_statistics_with_buffer Views">
<code class="literal">
x$schema_table_statistics_with_buffer
</code>
</a>
views have these columns:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<code class="literal">
table_schema
</code>
</p>
<p>
The schema that contains the table.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
table_name
</code>
</p>
<p>
The table name.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
rows_fetched
</code>
</p>
<p>
The total number of rows read from the table.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
fetch_latency
</code>
</p>
<p>
The total wait time of timed read I/O events for the
table.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
rows_inserted
</code>
</p>
<p>
The total number of rows inserted into the table.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
insert_latency
</code>
</p>
<p>
The total wait time of timed insert I/O events for the
table.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
rows_updated
</code>
</p>
<p>
The total number of rows updated in the table.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
update_latency
</code>
</p>
<p>
The total wait time of timed update I/O events for the
table.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
rows_deleted
</code>
</p>
<p>
The total number of rows deleted from the table.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
delete_latency
</code>
</p>
<p>
The total wait time of timed delete I/O events for the
table.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
io_read_requests
</code>
</p>
<p>
The total number of read requests for the table.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
io_read
</code>
</p>
<p>
The total number of bytes read from the table.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
io_read_latency
</code>
</p>
<p>
The total wait time of reads from the table.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
io_write_requests
</code>
</p>
<p>
The total number of write requests for the table.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
io_write
</code>
</p>
<p>
The total number of bytes written to the table.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
io_write_latency
</code>
</p>
<p>
The total wait time of writes to the table.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
io_misc_requests
</code>
</p>
<p>
The total number of miscellaneous I/O requests for the
table.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
io_misc_latency
</code>
</p>
<p>
The total wait time of miscellaneous I/O requests for the
table.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
innodb_buffer_allocated
</code>
</p>
<p>
The total number of
<code class="literal">
InnoDB
</code>
buffer bytes
allocated for the table.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
innodb_buffer_data
</code>
</p>
<p>
The total number of
<code class="literal">
InnoDB
</code>
data bytes
allocated for the table.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
innodb_buffer_free
</code>
</p>
<p>
The total number of
<code class="literal">
InnoDB
</code>
nondata
bytes allocated for the table
(
<code class="literal">
innodb_buffer_allocated
</code>
−
<code class="literal">
innodb_buffer_data
</code>
).
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
innodb_buffer_pages
</code>
</p>
<p>
The total number of
<code class="literal">
InnoDB
</code>
pages
allocated for the table.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
innodb_buffer_pages_hashed
</code>
</p>
<p>
The total number of
<code class="literal">
InnoDB
</code>
hashed pages
allocated for the table.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
innodb_buffer_pages_old
</code>
</p>
<p>
The total number of
<code class="literal">
InnoDB
</code>
old pages
allocated for the table.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
innodb_buffer_rows_cached
</code>
</p>
<p>
The total number of
<code class="literal">
InnoDB
</code>
cached rows
for the table.
</p>
</li>
</ul>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/version-tokens-usage.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="version-tokens-usage">
</a>
7.6.6.3 Using Version Tokens
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045256082144">
</a>
<p>
Before using Version Tokens, install it according to the
instructions provided at
<a class="xref" href="version-tokens-installation.html" title="7.6.6.2 Installing or Uninstalling Version Tokens">
Section 7.6.6.2, “Installing or Uninstalling Version Tokens”
</a>
.
</p>
<p>
A scenario in which Version Tokens can be useful is a system
that accesses a collection of MySQL servers but needs to manage
them for load balancing purposes by monitoring them and
adjusting server assignments according to load changes. Such a
system comprises these elements:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
The collection of MySQL servers to be managed.
</p>
</li>
<li class="listitem">
<p>
An administrative or management application that
communicates with the servers and organizes them into
high-availability groups. Groups serve different purposes,
and servers within each group may have different
assignments. Assignment of a server within a certain group
can change at any time.
</p>
</li>
<li class="listitem">
<p>
Client applications that access the servers to retrieve and
update data, choosing servers according to the purposes
assigned them. For example, a client should not send an
update to a read-only server.
</p>
</li>
</ul>
</div>
<p>
Version Tokens permit server access to be managed according to
assignment without requiring clients to repeatedly query the
servers about their assignments:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
The management application performs server assignments and
establishes version tokens on each server to reflect its
assignment. The application caches this information to
provide a central access point to it.
</p>
<p>
If at some point the management application needs to change
a server assignment (for example, to change it from
permitting writes to read only), it changes the server's
version token list and updates its cache.
</p>
</li>
<li class="listitem">
<p>
To improve performance, client applications obtain cache
information from the management application, enabling them
to avoid having to retrieve information about server
assignments for each statement. Based on the type of
statements it issues (for example, reads versus writes), a
client selects an appropriate server and connects to it.
</p>
</li>
<li class="listitem">
<p>
In addition, the client sends to the server its own
client-specific version tokens to register the assignment it
requires of the server. For each statement sent by the
client to the server, the server compares its own token list
with the client token list. If the server token list
contains all tokens present in the client token list with
the same values, there is a match and the server executes
the statement.
</p>
<p>
On the other hand, perhaps the management application has
changed the server assignment and its version token list. In
this case, the new server assignment may now be incompatible
with the client requirements. A token mismatch between the
server and client token lists occurs and the server returns
an error in reply to the statement. This is an indication to
the client to refresh its version token information from the
management application cache, and to select a new server to
communicate with.
</p>
</li>
</ul>
</div>
<p>
The client-side logic for detecting version token errors and
selecting a new server can be implemented different ways:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
The client can handle all version token registration,
mismatch detection, and connection switching itself.
</p>
</li>
<li class="listitem">
<p>
The logic for those actions can be implemented in a
connector that manages connections between clients and MySQL
servers. Such a connector might handle mismatch error
detection and statement resending itself, or it might pass
the error to the application and leave it to the application
to resend the statement.
</p>
</li>
</ul>
</div>
<p>
The following example illustrates the preceding discussion in
more concrete form.
</p>
<p>
When Version Tokens initializes on a given server, the server's
version token list is empty. Token list maintenance is performed
by calling functions. The
<a class="link" href="privileges-provided.html#priv_version-token-admin">
<code class="literal">
VERSION_TOKEN_ADMIN
</code>
</a>
privilege (or
the deprecated
<a class="link" href="privileges-provided.html#priv_super">
<code class="literal">
SUPER
</code>
</a>
privilege)
is required to call any of the Version Token functions, so token
list modification is expected to be done by a management or
administrative application that has that privilege.
</p>
<p>
Suppose that a management application communicates with a set of
servers that are queried by clients to access employee and
product databases (named
<code class="literal">
emp
</code>
and
<code class="literal">
prod
</code>
, respectively). All servers are
permitted to process data retrieval statements, but only some of
them are permitted to make database updates. To handle this on a
database-specific basis, the management application establishes
a list of version tokens on each server. In the token list for a
given server, token names represent database names and token
values are
<code class="literal">
read
</code>
or
<code class="literal">
write
</code>
depending on whether the database must be used in read-only
fashion or whether it can take reads and writes.
</p>
<p>
Client applications register a list of version tokens they
require the server to match by setting a system variable.
Variable setting occurs on a client-specific basis, so different
clients can register different requirements. By default, the
client token list is empty, which matches any server token list.
When a client sets its token list to a nonempty value, matching
may succeed or fail, depending on the server version token list.
</p>
<p>
To define the version token list for a server, the management
application calls the
<a class="link" href="version-tokens-reference.html#function_version-tokens-set">
<code class="literal">
version_tokens_set()
</code>
</a>
function.
(There are also functions for modifying and displaying the token
list, described later.) For example, the application might send
these statements to a group of three servers:
</p>
<p>
Server 1:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa20987873"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> version_tokens_set<span class="token punctuation">(</span><span class="token string">'emp=read;prod=read'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> version_tokens_set('emp=read;prod=read') <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 2 version tokens set. <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
</div>
<p>
Server 2:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa27927533"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> version_tokens_set<span class="token punctuation">(</span><span class="token string">'emp=write;prod=read'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> version_tokens_set('emp=write;prod=read') <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 2 version tokens set. <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
</div>
<p>
Server 3:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa62273943"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> version_tokens_set<span class="token punctuation">(</span><span class="token string">'emp=read;prod=write'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> version_tokens_set('emp=read;prod=write') <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 2 version tokens set. <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
</div>
<p>
The token list in each case is specified as a
semicolon-separated list of
<code class="literal">
<em class="replaceable">
<code>
name
</code>
</em>
=
<em class="replaceable">
<code>
value
</code>
</em>
</code>
pairs. The resulting token list values result in these server
assignments:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
Any server accepts reads for either database.
</p>
</li>
<li class="listitem">
<p>
Only server 2 accepts updates for the
<code class="literal">
emp
</code>
database.
</p>
</li>
<li class="listitem">
<p>
Only server 3 accepts updates for the
<code class="literal">
prod
</code>
database.
</p>
</li>
</ul>
</div>
<p>
In addition to assigning each server a version token list, the
management application also maintains a cache that reflects the
server assignments.
</p>
<p>
Before communicating with the servers, a client application
contacts the management application and retrieves information
about server assignments. Then the client selects a server based
on those assignments. Suppose that a client wants to perform
both reads and writes on the
<code class="literal">
emp
</code>
database.
Based on the preceding assignments, only server 2 qualifies. The
client connects to server 2 and registers its server
requirements there by setting its
<a class="link" href="version-tokens-reference.html#sysvar_version_tokens_session">
<code class="literal">
version_tokens_session
</code>
</a>
system
variable:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa39079437"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SET</span> <span class="token variable">@@SESSION.version_tokens_session</span> <span class="token operator">=</span> <span class="token string">'emp=write'</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
For subsequent statements sent by the client to server 2, the
server compares its own version token list to the client list to
check whether they match. If so, statements execute normally:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa92347027"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">UPDATE</span> emp<span class="token punctuation">.</span>employee <span class="token keyword">SET</span> salary <span class="token operator">=</span> salary <span class="token operator">*</span> <span class="token number">1.1</span> <span class="token keyword">WHERE</span> id <span class="token operator">=</span> <span class="token number">4981</span><span class="token punctuation">;</span>
<span class="token output">Query OK, 1 row affected (0.07 sec)</span>
<span class="token output">Rows matched: 1 Changed: 1 Warnings: 0</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> last_name<span class="token punctuation">,</span> first_name <span class="token keyword">FROM</span> emp<span class="token punctuation">.</span>employee <span class="token keyword">WHERE</span> id <span class="token operator">=</span> <span class="token number">4981</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> last_name <span class="token punctuation">|</span> first_name <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> Smith <span class="token punctuation">|</span> Abe <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output">1 row in set (0.01 sec)</span></code></pre>
</div>
<p>
Discrepancies between the server and client version token lists
can occur two ways:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
A token name in the
<a class="link" href="version-tokens-reference.html#sysvar_version_tokens_session">
<code class="literal">
version_tokens_session
</code>
</a>
value is not present in the server token list. In this case,
an
<a class="ulink" href="/doc/mysql-errors/8.4/en/server-error-reference.html#error_er_vtoken_plugin_token_not_found" target="_top">
<code class="literal">
ER_VTOKEN_PLUGIN_TOKEN_NOT_FOUND
</code>
</a>
error occurs.
</p>
</li>
<li class="listitem">
<p>
A token value in the
<a class="link" href="version-tokens-reference.html#sysvar_version_tokens_session">
<code class="literal">
version_tokens_session
</code>
</a>
value differs from the value of the corresponding token in
the server token list. In this case, an
<a class="ulink" href="/doc/mysql-errors/8.4/en/server-error-reference.html#error_er_vtoken_plugin_token_mismatch" target="_top">
<code class="literal">
ER_VTOKEN_PLUGIN_TOKEN_MISMATCH
</code>
</a>
error occurs.
</p>
</li>
</ul>
</div>
<p>
As long as the assignment of server 2 does not change, the
client continues to use it for reads and writes. But suppose
that the management application wants to change server
assignments so that writes for the
<code class="literal">
emp
</code>
database must be sent to server 1 instead of server 2. To do
this, it uses
<a class="link" href="version-tokens-reference.html#function_version-tokens-edit">
<code class="literal">
version_tokens_edit()
</code>
</a>
to modify
the
<code class="literal">
emp
</code>
token value on the two servers (and
updates its cache of server assignments):
</p>
<p>
Server 1:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa52042938"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> version_tokens_edit<span class="token punctuation">(</span><span class="token string">'emp=write'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> version_tokens_edit('emp=write') <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 1 version tokens updated. <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
</div>
<p>
Server 2:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa36092642"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> version_tokens_edit<span class="token punctuation">(</span><span class="token string">'emp=read'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> version_tokens_edit('emp=read') <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 1 version tokens updated. <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
</div>
<p>
<a class="link" href="version-tokens-reference.html#function_version-tokens-edit">
<code class="literal">
version_tokens_edit()
</code>
</a>
modifies
the named tokens in the server token list and leaves other
tokens unchanged.
</p>
<p>
The next time the client sends a statement to server 2, its own
token list no longer matches the server token list and an error
occurs:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa73002427"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">UPDATE</span> emp<span class="token punctuation">.</span>employee <span class="token keyword">SET</span> salary <span class="token operator">=</span> salary <span class="token operator">*</span> <span class="token number">1.1</span> <span class="token keyword">WHERE</span> id <span class="token operator">=</span> <span class="token number">4982</span><span class="token punctuation">;</span>
<span class="token output">ERROR 3136 (42000)<span class="token punctuation">:</span> Version token mismatch for emp. Correct value read</span></code></pre>
</div>
<p>
In this case, the client should contact the management
application to obtain updated information about server
assignments, select a new server, and send the failed statement
to the new server.
</p>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
Each client must cooperate with Version Tokens by sending only
statements in accordance with the token list that it registers
with a given server. For example, if a client registers a
token list of
<code class="literal">
'emp=read'
</code>
, there is nothing
in Version Tokens to prevent the client from sending updates
for the
<code class="literal">
emp
</code>
database. The client itself
must refrain from doing so.
</p>
</div>
<p>
For each statement received from a client, the server implicitly
uses locking, as follows:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
Take a shared lock for each token named in the client token
list (that is, in the
<a class="link" href="version-tokens-reference.html#sysvar_version_tokens_session">
<code class="literal">
version_tokens_session
</code>
</a>
value)
</p>
</li>
<li class="listitem">
<p>
Perform the comparison between the server and client token
lists
</p>
</li>
<li class="listitem">
<p>
Execute the statement or produce an error depending on the
comparison result
</p>
</li>
<li class="listitem">
<p>
Release the locks
</p>
</li>
</ul>
</div>
<p>
The server uses shared locks so that comparisons for multiple
sessions can occur without blocking, while preventing changes to
the tokens for any session that attempts to acquire an exclusive
lock before it manipulates tokens of the same names in the
server token list.
</p>
<p>
The preceding example uses only a few of the functions included
in the Version Tokens plugin library, but there are others. One
set of functions permits the server's list of version tokens to
be manipulated and inspected. Another set of functions permits
version tokens to be locked and unlocked.
</p>
<p>
These functions permit the server's list of version tokens to be
created, changed, removed, and inspected:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<a class="link" href="version-tokens-reference.html#function_version-tokens-set">
<code class="literal">
version_tokens_set()
</code>
</a>
completely replaces the current list and assigns a new list.
The argument is a semicolon-separated list of
<code class="literal">
<em class="replaceable">
<code>
name
</code>
</em>
=
<em class="replaceable">
<code>
value
</code>
</em>
</code>
pairs.
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="version-tokens-reference.html#function_version-tokens-edit">
<code class="literal">
version_tokens_edit()
</code>
</a>
enables
partial modifications to the current list. It can add new
tokens or change the values of existing tokens. The argument
is a semicolon-separated list of
<code class="literal">
<em class="replaceable">
<code>
name
</code>
</em>
=
<em class="replaceable">
<code>
value
</code>
</em>
</code>
pairs.
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="version-tokens-reference.html#function_version-tokens-delete">
<code class="literal">
version_tokens_delete()
</code>
</a>
deletes tokens from the current list. The argument is a
semicolon-separated list of token names.
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="version-tokens-reference.html#function_version-tokens-show">
<code class="literal">
version_tokens_show()
</code>
</a>
displays the current token list. It takes no argument.
</p>
</li>
</ul>
</div>
<p>
Each of those functions, if successful, returns a binary string
indicating what action occurred. The following example
establishes the server token list, modifies it by adding a new
token, deletes some tokens, and displays the resulting token
list:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa51438718"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> version_tokens_set<span class="token punctuation">(</span><span class="token string">'tok1=a;tok2=b'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> version_tokens_set('tok1=a;tok2=b') <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 2 version tokens set. <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> version_tokens_edit<span class="token punctuation">(</span><span class="token string">'tok3=c'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> version_tokens_edit('tok3=c') <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 1 version tokens updated. <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> version_tokens_delete<span class="token punctuation">(</span><span class="token string">'tok2;tok1'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> version_tokens_delete('tok2;tok1') <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 2 version tokens deleted. <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> version_tokens_show<span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> version_tokens_show() <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> tok3=c; <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
</div>
<p>
Warnings occur if a token list is malformed:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa53491971"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> version_tokens_set<span class="token punctuation">(</span><span class="token string">'tok1=a; =c'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> version_tokens_set('tok1=a; =c') <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 1 version tokens set. <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output">1 row in set, 1 warning (0.00 sec)</span>
<span class="token prompt">mysql></span> <span class="token keyword">SHOW</span> <span class="token keyword">WARNINGS</span>\G
<span class="token output"><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span> 1. row <span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span>
Level<span class="token punctuation">:</span> Warning
Code<span class="token punctuation">:</span> 42000
Message<span class="token punctuation">:</span> Invalid version token pair encountered. The list provided
is only partially updated.
</span><span class="token output">1 row in set (0.00 sec)</span></code></pre>
</div>
<p>
As mentioned previously, version tokens are defined using a
semicolon-separated list of
<code class="literal">
<em class="replaceable">
<code>
name
</code>
</em>
=
<em class="replaceable">
<code>
value
</code>
</em>
</code>
pairs. Consider this invocation of
<a class="link" href="version-tokens-reference.html#function_version-tokens-set">
<code class="literal">
version_tokens_set()
</code>
</a>
:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa8350183"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> version_tokens_set<span class="token punctuation">(</span><span class="token string">'tok1=b;;; tok2= a = b ; tok1 = 1\'2 3"4'</span><span class="token punctuation">)</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> version_tokens_set('tok1=b;;; tok2= a = b ; tok1 = 1\'2 3"4') <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 3 version tokens set. <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
</div>
<p>
Version Tokens interprets the argument as follows:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
Whitespace around names and values is ignored. Whitespace
within names and values is permitted. (For
<a class="link" href="version-tokens-reference.html#function_version-tokens-delete">
<code class="literal">
version_tokens_delete()
</code>
</a>
,
which takes a list of names without values, whitespace
around names is ignored.)
</p>
</li>
<li class="listitem">
<p>
There is no quoting mechanism.
</p>
</li>
<li class="listitem">
<p>
Order of tokens is not significant except that if a token
list contains multiple instances of a given token name, the
last value takes precedence over earlier values.
</p>
</li>
</ul>
</div>
<p>
Given those rules, the preceding
<a class="link" href="version-tokens-reference.html#function_version-tokens-set">
<code class="literal">
version_tokens_set()
</code>
</a>
call results
in a token list with two tokens:
<code class="literal">
tok1
</code>
has the
value
<code class="literal">
1'2 3"4
</code>
, and
<code class="literal">
tok2
</code>
has the value
<code class="literal">
a = b
</code>
. To verify this, call
<a class="link" href="version-tokens-reference.html#function_version-tokens-show">
<code class="literal">
version_tokens_show()
</code>
</a>
:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa88123125"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> version_tokens_show<span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> version_tokens_show() <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> tok2=a = b;tok1=1'2 3"4; <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
</div>
<p>
If the token list contains two tokens, why did
<a class="link" href="version-tokens-reference.html#function_version-tokens-set">
<code class="literal">
version_tokens_set()
</code>
</a>
return the
value
<code class="literal">
3 version tokens set
</code>
? That occurred
because the original token list contained two definitions for
<code class="literal">
tok1
</code>
, and the second definition replaced the
first.
</p>
<p>
The Version Tokens token-manipulation functions place these
constraints on token names and values:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
Token names cannot contain
<code class="literal">
=
</code>
or
<code class="literal">
;
</code>
characters and have a maximum length of
64 characters.
</p>
</li>
<li class="listitem">
<p>
Token values cannot contain
<code class="literal">
;
</code>
characters.
Length of values is constrained by the value of the
<a class="link" href="server-system-variables.html#sysvar_max_allowed_packet">
<code class="literal">
max_allowed_packet
</code>
</a>
system
variable.
</p>
</li>
<li class="listitem">
<p>
Version Tokens treats token names and values as binary
strings, so comparisons are case-sensitive.
</p>
</li>
</ul>
</div>
<p>
Version Tokens also includes a set of functions enabling tokens
to be locked and unlocked:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<a class="link" href="version-tokens-reference.html#function_version-tokens-lock-exclusive">
<code class="literal">
version_tokens_lock_exclusive()
</code>
</a>
acquires exclusive version token locks. It takes a list of
one or more lock names and a timeout value.
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="version-tokens-reference.html#function_version-tokens-lock-shared">
<code class="literal">
version_tokens_lock_shared()
</code>
</a>
acquires shared version token locks. It takes a list of one
or more lock names and a timeout value.
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="version-tokens-reference.html#function_version-tokens-unlock">
<code class="literal">
version_tokens_unlock()
</code>
</a>
releases version token locks (exclusive and shared). It
takes no argument.
</p>
</li>
</ul>
</div>
<p>
Each locking function returns nonzero for success. Otherwise, an
error occurs:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa90422214"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> version_tokens_lock_shared<span class="token punctuation">(</span><span class="token string">'lock1'</span><span class="token punctuation">,</span> <span class="token string">'lock2'</span><span class="token punctuation">,</span> <span class="token number">0</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> version_tokens_lock_shared('lock1', 'lock2', 0) <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 1 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> version_tokens_lock_shared<span class="token punctuation">(</span><span class="token boolean">NULL</span><span class="token punctuation">,</span> <span class="token number">0</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output">ERROR 3131 (42000)<span class="token punctuation">:</span> Incorrect locking service lock name '(null)'.</span></code></pre>
</div>
<p>
Locking using Version Tokens locking functions is advisory;
applications must agree to cooperate.
</p>
<p>
It is possible to lock nonexisting token names. This does not
create the tokens.
</p>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
Version Tokens locking functions are based on the locking
service described at
<a class="xref" href="locking-service.html" title="7.6.9.1 The Locking Service">
Section 7.6.9.1, “The Locking Service”
</a>
, and
thus have the same semantics for shared and exclusive locks.
(Version Tokens uses the locking service routines built into
the server, not the locking service function interface, so
those functions need not be installed to use Version Tokens.)
Locks acquired by Version Tokens use a locking service
namespace of
<code class="literal">
version_token_locks
</code>
. Locking
service locks can be monitored using the Performance Schema,
so this is also true for Version Tokens locks. For details,
see
<a class="xref" href="locking-service.html#locking-service-monitoring" title="Locking Service Monitoring">
Locking Service Monitoring
</a>
.
</p>
</div>
<p>
For the Version Tokens locking functions, token name arguments
are used exactly as specified. Surrounding whitespace is not
ignored and
<code class="literal">
=
</code>
and
<code class="literal">
;
</code>
characters are permitted. This is because Version Tokens simply
passes the token names to be locked as is to the locking
service.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/sys-ps-is-consumer-enabled.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="sys-ps-is-consumer-enabled">
</a>
30.4.5.10 The ps_is_consumer_enabled() Function
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045060874960">
</a>
<a class="indexterm" name="idm46045060873456">
</a>
<p>
Returns
<code class="literal">
YES
</code>
or
<code class="literal">
NO
</code>
to
indicate whether a given Performance Schema consumer is
enabled, or
<code class="literal">
NULL
</code>
if the argument is
<code class="literal">
NULL
</code>
. If the argument is not a valid
consumer name, an error occurs.
</p>
<p>
This function accounts for the consumer hierarchy, so a
consumer is not considered enabled unless all consumers on
which depends are also enabled. For information about the
consumer hierarchy, see
<a class="xref" href="performance-schema-consumer-filtering.html" title="29.4.7 Pre-Filtering by Consumer">
Section 29.4.7, “Pre-Filtering by Consumer”
</a>
.
</p>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h5 class="title">
<a name="sys-ps-is-consumer-enabled-parameters">
</a>
Parameters
</h5>
</div>
</div>
</div>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<code class="literal">
in_consumer VARCHAR(64)
</code>
: The name of
the consumer to check.
</p>
</li>
</ul>
</div>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h5 class="title">
<a name="sys-ps-is-consumer-enabled-return-value">
</a>
Return Value
</h5>
</div>
</div>
</div>
<p>
An
<code class="literal">
ENUM('YES','NO')
</code>
value.
</p>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h5 class="title">
<a name="sys-ps-is-consumer-enabled-example">
</a>
Example
</h5>
</div>
</div>
</div>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa27099244"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> sys<span class="token punctuation">.</span>ps_is_consumer_enabled<span class="token punctuation">(</span><span class="token string">'thread_instrumentation'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> sys.ps_is_consumer_enabled('thread_instrumentation') <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> YES <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
</div>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/mysql-calendar.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="mysql-calendar">
</a>
13.2.7 What Calendar Is Used By MySQL?
</h3>
</div>
</div>
</div>
<a class="indexterm" name="idm46045213253312">
</a>
<p>
MySQL uses what is known as a
<span class="firstterm">
proleptic Gregorian
calendar
</span>
.
</p>
<p>
Every country that has switched from the Julian to the Gregorian
calendar has had to discard at least ten days during the switch.
To see how this works, consider the month of October 1582, when
the first Julian-to-Gregorian switch occurred.
</p>
<div class="informaltable">
<table summary="The month of October 1582, when the first Julian-to-Gregorian switch occurred. Table headings are days of the week and table rows list the dates for each day of the week. The table is intended to illustrate that there are no dates between October 4 and October 15.">
<colgroup>
<col style="width: 14%"/>
<col style="width: 14%"/>
<col style="width: 14%"/>
<col style="width: 14%"/>
<col style="width: 14%"/>
<col style="width: 14%"/>
<col style="width: 14%"/>
</colgroup>
<thead>
<tr>
<th scope="col">
Monday
</th>
<th scope="col">
Tuesday
</th>
<th scope="col">
Wednesday
</th>
<th scope="col">
Thursday
</th>
<th scope="col">
Friday
</th>
<th scope="col">
Saturday
</th>
<th scope="col">
Sunday
</th>
</tr>
</thead>
<tbody>
<tr>
<th scope="row">
1
</th>
<td>
2
</td>
<td>
3
</td>
<td>
4
</td>
<td>
15
</td>
<td>
16
</td>
<td>
17
</td>
</tr>
<tr>
<th scope="row">
18
</th>
<td>
19
</td>
<td>
20
</td>
<td>
21
</td>
<td>
22
</td>
<td>
23
</td>
<td>
24
</td>
</tr>
<tr>
<th scope="row">
25
</th>
<td>
26
</td>
<td>
27
</td>
<td>
28
</td>
<td>
29
</td>
<td>
30
</td>
<td>
31
</td>
</tr>
</tbody>
</table>
</div>
<p>
There are no dates between October 4 and October 15. This
discontinuity is called the
<span class="firstterm">
cutover
</span>
. Any dates before
the cutover are Julian, and any dates following the cutover are
Gregorian. Dates during a cutover are nonexistent.
</p>
<p>
A calendar applied to dates when it was not actually in use is
called
<span class="firstterm">
proleptic
</span>
. Thus, if
we assume there was never a cutover and Gregorian rules always
rule, we have a proleptic Gregorian calendar. This is what is
used by MySQL, as is required by standard SQL. For this reason,
dates prior to the cutover stored as MySQL
<a class="link" href="datetime.html" title="13.2.2 The DATE, DATETIME, and TIMESTAMP Types">
<code class="literal">
DATE
</code>
</a>
or
<a class="link" href="datetime.html" title="13.2.2 The DATE, DATETIME, and TIMESTAMP Types">
<code class="literal">
DATETIME
</code>
</a>
values must be adjusted
to compensate for the difference. It is important to realize
that the cutover did not occur at the same time in all
countries, and that the later it happened, the more days were
lost. For example, in Great Britain, it took place in 1752, when
Wednesday September 2 was followed by Thursday September 14.
Russia remained on the Julian calendar until 1918, losing 13
days in the process, and what is popularly referred to as its
<span class="quote">
“
<span class="quote">
October Revolution
</span>
”
</span>
occurred in November according
to the Gregorian calendar.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/source-configuration-third-party.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="source-configuration-third-party">
</a>
2.8.9 MySQL Configuration and Third-Party Tools
</h3>
</div>
</div>
</div>
<a class="indexterm" name="idm46045327157504">
</a>
<a class="indexterm" name="idm46045327156016">
</a>
<p>
Third-party tools that need to determine the MySQL version from
the MySQL source can read the
<code class="filename">
MYSQL_VERSION
</code>
file in the top-level source directory. The file lists the pieces
of the version separately. For example, if the version is MySQL
8.4.0, the file looks like this:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-simple"><div class="docs-select-all right" id="sa11651994"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-simple">MYSQL_VERSION_MAJOR<span class="token operator">=</span>8
MYSQL_VERSION_MINOR<span class="token operator">=</span>4
MYSQL_VERSION_PATCH<span class="token operator">=</span>0
MYSQL_VERSION_EXTRA<span class="token operator">=</span>"INNOVATION"</code></pre>
</div>
<p>
To construct a five-digit number from the version components, use
this formula:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-simple"><div class="docs-select-all right" id="sa79772766"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-simple">MYSQL_VERSION_MAJOR<span class="token operator">*</span>10000 <span class="token operator">+</span> MYSQL_VERSION_MINOR<span class="token operator">*</span>100 <span class="token operator">+</span> MYSQL_VERSION_PATCH</code></pre>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/sys-host-summary-by-file-io-type.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="sys-host-summary-by-file-io-type">
</a>
30.4.3.3 The host_summary_by_file_io_type and x$host_summary_by_file_io_type
Views
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045063310800">
</a>
<a class="indexterm" name="idm46045063309344">
</a>
<a class="indexterm" name="idm46045063307840">
</a>
<a class="indexterm" name="idm46045063306336">
</a>
<p>
These views summarize file I/O, grouped by host and event
type. By default, rows are sorted by host and descending total
I/O latency.
</p>
<p>
The
<a class="link" href="sys-host-summary-by-file-io-type.html" title="30.4.3.3 The host_summary_by_file_io_type and x$host_summary_by_file_io_type Views">
<code class="literal">
host_summary_by_file_io_type
</code>
</a>
and
<a class="link" href="sys-host-summary-by-file-io-type.html" title="30.4.3.3 The host_summary_by_file_io_type and x$host_summary_by_file_io_type Views">
<code class="literal">
x$host_summary_by_file_io_type
</code>
</a>
views have these columns:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<code class="literal">
host
</code>
</p>
<p>
The host from which the client connected. Rows for which
the
<code class="literal">
HOST
</code>
column in the underlying
Performance Schema table is
<code class="literal">
NULL
</code>
are
assumed to be for background threads and are reported with
a host name of
<code class="literal">
background
</code>
.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
event_name
</code>
</p>
<p>
The file I/O event name.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
total
</code>
</p>
<p>
The total number of occurrences of the file I/O event for
the host.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
total_latency
</code>
</p>
<p>
The total wait time of timed occurrences of the file I/O
event for the host.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
max_latency
</code>
</p>
<p>
The maximum single wait time of timed occurrences of the
file I/O event for the host.
</p>
</li>
</ul>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/compiler-characteristics.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="compiler-characteristics">
</a>
2.1.6 Compiler-Specific Build Characteristics
</h3>
</div>
</div>
</div>
<a class="indexterm" name="idm46045332657184">
</a>
<p>
In some cases, the compiler used to build MySQL affects the
features available for use. The notes in this section apply for
binary distributions provided by Oracle Corporation or that you
compile yourself from source.
</p>
<p>
<span class="bold">
<strong>
<span class="command">
<strong>
icc
</strong>
</span>
(Intel C++ Compiler)
Builds
</strong>
</span>
</p>
<p>
A server built with
<span class="command">
<strong>
icc
</strong>
</span>
has these
characteristics:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
SSL support is not included.
</p>
</li>
</ul>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/set-transaction.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="set-transaction">
</a>
15.3.7 SET TRANSACTION Statement
</h3>
</div>
</div>
</div>
<a class="indexterm" name="idm46045178293936">
</a>
<a class="indexterm" name="idm46045178292880">
</a>
<a class="indexterm" name="idm46045178291808">
</a>
<a class="indexterm" name="idm46045178290736">
</a>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa14346428"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SET</span> <span class="token punctuation">[</span><span class="token keyword">GLOBAL</span> <span class="token operator">|</span> <span class="token keyword">SESSION</span><span class="token punctuation">]</span> <span class="token keyword">TRANSACTION</span>
<em class="replaceable">transaction_characteristic</em> <span class="token punctuation">[</span><span class="token punctuation">,</span> <em class="replaceable">transaction_characteristic</em><span class="token punctuation">]</span> <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span>
<em class="replaceable">transaction_characteristic</em>: {
<span class="token keyword">ISOLATION</span> <span class="token keyword">LEVEL</span> <span class="token keyword"><em class="replaceable">level</em></span>
<span class="token operator">|</span> <em class="replaceable">access_mode</em>
}
<span class="token keyword"><em class="replaceable">level</em></span>: {
<span class="token keyword">REPEATABLE</span> <span class="token keyword">READ</span>
<span class="token operator">|</span> <span class="token keyword">READ</span> <span class="token keyword">COMMITTED</span>
<span class="token operator">|</span> <span class="token keyword">READ</span> <span class="token keyword">UNCOMMITTED</span>
<span class="token operator">|</span> <span class="token keyword">SERIALIZABLE</span>
}
<em class="replaceable">access_mode</em>: {
<span class="token keyword">READ</span> <span class="token keyword">WRITE</span>
<span class="token operator">|</span> <span class="token keyword">READ</span> <span class="token keyword">ONLY</span>
}</code></pre>
</div>
<p>
This statement specifies
<a class="link" href="glossary.html#glos_transaction" title="transaction">
transaction
</a>
characteristics. It takes a list of one or more characteristic
values separated by commas. Each characteristic value sets the
transaction
<a class="link" href="glossary.html#glos_isolation_level" title="isolation level">
isolation
level
</a>
or access mode. The isolation level is used for
operations on
<a class="link" href="innodb-storage-engine.html" title="Chapter 17 The InnoDB Storage Engine">
<code class="literal">
InnoDB
</code>
</a>
tables. The
access mode specifies whether transactions operate in read/write
or read-only mode.
</p>
<p>
In addition,
<a class="link" href="set-transaction.html" title="15.3.7 SET TRANSACTION Statement">
<code class="literal">
SET TRANSACTION
</code>
</a>
can
include an optional
<code class="literal">
GLOBAL
</code>
or
<code class="literal">
SESSION
</code>
keyword to indicate the scope of the
statement.
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<a class="xref" href="set-transaction.html#set-transaction-isolation-level" title="Transaction Isolation Levels">
Transaction Isolation Levels
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="set-transaction.html#set-transaction-access-mode" title="Transaction Access Mode">
Transaction Access Mode
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="set-transaction.html#set-transaction-scope" title="Transaction Characteristic Scope">
Transaction Characteristic Scope
</a>
</p>
</li>
</ul>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h4 class="title">
<a name="set-transaction-isolation-level">
</a>
Transaction Isolation Levels
</h4>
</div>
</div>
</div>
<p>
To set the transaction isolation level, use an
<code class="literal">
ISOLATION LEVEL
<em class="replaceable">
<code>
level
</code>
</em>
</code>
clause. It is not
permitted to specify multiple
<code class="literal">
ISOLATION LEVEL
</code>
clauses in the same
<a class="link" href="set-transaction.html" title="15.3.7 SET TRANSACTION Statement">
<code class="literal">
SET
TRANSACTION
</code>
</a>
statement.
</p>
<p>
The default isolation level is
<a class="link" href="innodb-transaction-isolation-levels.html#isolevel_repeatable-read">
<code class="literal">
REPEATABLE READ
</code>
</a>
. Other
permitted values are
<a class="link" href="innodb-transaction-isolation-levels.html#isolevel_read-committed">
<code class="literal">
READ
COMMITTED
</code>
</a>
,
<a class="link" href="innodb-transaction-isolation-levels.html#isolevel_read-uncommitted">
<code class="literal">
READ
UNCOMMITTED
</code>
</a>
, and
<a class="link" href="innodb-transaction-isolation-levels.html#isolevel_serializable">
<code class="literal">
SERIALIZABLE
</code>
</a>
. For information
about these isolation levels, see
<a class="xref" href="innodb-transaction-isolation-levels.html" title="17.7.2.1 Transaction Isolation Levels">
Section 17.7.2.1, “Transaction Isolation Levels”
</a>
.
</p>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h4 class="title">
<a name="set-transaction-access-mode">
</a>
Transaction Access Mode
</h4>
</div>
</div>
</div>
<p>
To set the transaction access mode, use a
<code class="literal">
READ
WRITE
</code>
or
<code class="literal">
READ ONLY
</code>
clause. It is
not permitted to specify multiple access-mode clauses in the
same
<a class="link" href="set-transaction.html" title="15.3.7 SET TRANSACTION Statement">
<code class="literal">
SET TRANSACTION
</code>
</a>
statement.
</p>
<p>
By default, a transaction takes place in read/write mode, with
both reads and writes permitted to tables used in the
transaction. This mode may be specified explicitly using
<a class="link" href="set-transaction.html" title="15.3.7 SET TRANSACTION Statement">
<code class="literal">
SET TRANSACTION
</code>
</a>
with an access
mode of
<code class="literal">
READ WRITE
</code>
.
</p>
<p>
If the transaction access mode is set to
<code class="literal">
READ
ONLY
</code>
, changes to tables are prohibited. This may
enable storage engines to make performance improvements that are
possible when writes are not permitted.
</p>
<p>
In read-only mode, it remains possible to change tables created
with the
<code class="literal">
TEMPORARY
</code>
keyword using DML
statements. Changes made with DDL statements are not permitted,
just as with permanent tables.
</p>
<p>
The
<code class="literal">
READ WRITE
</code>
and
<code class="literal">
READ
ONLY
</code>
access modes also may be specified for an
individual transaction using the
<a class="link" href="commit.html" title="15.3.1 START TRANSACTION, COMMIT, and ROLLBACK Statements">
<code class="literal">
START
TRANSACTION
</code>
</a>
statement.
</p>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h4 class="title">
<a name="set-transaction-scope">
</a>
Transaction Characteristic Scope
</h4>
</div>
</div>
</div>
<p>
You can set transaction characteristics globally, for the
current session, or for the next transaction only:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
With the
<code class="literal">
GLOBAL
</code>
keyword:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
The statement applies globally for all subsequent
sessions.
</p>
</li>
<li class="listitem">
<p>
Existing sessions are unaffected.
</p>
</li>
</ul>
</div>
</li>
<li class="listitem">
<p>
With the
<code class="literal">
SESSION
</code>
keyword:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
The statement applies to all subsequent transactions
performed within the current session.
</p>
</li>
<li class="listitem">
<p>
The statement is permitted within transactions, but does
not affect the current ongoing transaction.
</p>
</li>
<li class="listitem">
<p>
If executed between transactions, the statement
overrides any preceding statement that sets the
next-transaction value of the named characteristics.
</p>
</li>
</ul>
</div>
</li>
<li class="listitem">
<p>
Without any
<code class="literal">
SESSION
</code>
or
<code class="literal">
GLOBAL
</code>
keyword:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
The statement applies only to the next single
transaction performed within the session.
</p>
</li>
<li class="listitem">
<p>
Subsequent transactions revert to using the session
value of the named characteristics.
</p>
</li>
<li class="listitem">
<p>
The statement is not permitted within transactions:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa60415574"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">START</span> <span class="token keyword">TRANSACTION</span><span class="token punctuation">;</span>
<span class="token output">Query OK, 0 rows affected (0.02 sec)</span>
<span class="token prompt">mysql></span> <span class="token keyword">SET</span> <span class="token keyword">TRANSACTION</span> <span class="token keyword">ISOLATION</span> <span class="token keyword">LEVEL</span> <span class="token keyword">SERIALIZABLE</span><span class="token punctuation">;</span>
<span class="token output">ERROR 1568 (25001)<span class="token punctuation">:</span> Transaction characteristics can't be changed
while a transaction is in progress</span></code></pre>
</div>
</li>
</ul>
</div>
</li>
</ul>
</div>
<p>
A change to global transaction characteristics requires the
<a class="link" href="privileges-provided.html#priv_connection-admin">
<code class="literal">
CONNECTION_ADMIN
</code>
</a>
privilege (or
the deprecated
<a class="link" href="privileges-provided.html#priv_super">
<code class="literal">
SUPER
</code>
</a>
privilege).
Any session is free to change its session characteristics (even
in the middle of a transaction), or the characteristics for its
next transaction (prior to the start of that transaction).
</p>
<p>
To set the global isolation level at server startup, use the
<a class="link" href="server-options.html#option_mysqld_transaction-isolation">
<code class="option">
--transaction-isolation=
<em class="replaceable">
<code>
level
</code>
</em>
</code>
</a>
option on the command line or in an option file. Values of
<em class="replaceable">
<code>
level
</code>
</em>
for this option use dashes
rather than spaces, so the permissible values are
<a class="link" href="innodb-transaction-isolation-levels.html#isolevel_read-uncommitted">
<code class="literal">
READ-UNCOMMITTED
</code>
</a>
,
<a class="link" href="innodb-transaction-isolation-levels.html#isolevel_read-committed">
<code class="literal">
READ-COMMITTED
</code>
</a>
,
<a class="link" href="innodb-transaction-isolation-levels.html#isolevel_repeatable-read">
<code class="literal">
REPEATABLE-READ
</code>
</a>
, or
<a class="link" href="innodb-transaction-isolation-levels.html#isolevel_serializable">
<code class="literal">
SERIALIZABLE
</code>
</a>
.
</p>
<p>
Similarly, to set the global transaction access mode at server
startup, use the
<a class="link" href="server-options.html#option_mysqld_transaction-read-only">
<code class="option">
--transaction-read-only
</code>
</a>
option.
The default is
<code class="literal">
OFF
</code>
(read/write mode) but the
value can be set to
<code class="literal">
ON
</code>
for a mode of read
only.
</p>
<p>
For example, to set the isolation level to
<a class="link" href="innodb-transaction-isolation-levels.html#isolevel_repeatable-read">
<code class="literal">
REPEATABLE READ
</code>
</a>
and the
access mode to
<code class="literal">
READ WRITE
</code>
, use these lines in
the
<code class="literal">
[mysqld]
</code>
section of an option file:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-ini"><div class="docs-select-all right" id="sa85790961"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-ini"><span class="token selector">[mysqld]</span>
<span class="token constant">transaction-isolation</span> <span class="token attr-value"><span class="token punctuation">=</span> REPEATABLE-READ</span>
<span class="token constant">transaction-read-only</span> <span class="token attr-value"><span class="token punctuation">=</span> OFF</span></code></pre>
</div>
<p>
At runtime, characteristics at the global, session, and
next-transaction scope levels can be set indirectly using the
<a class="link" href="set-transaction.html" title="15.3.7 SET TRANSACTION Statement">
<code class="literal">
SET TRANSACTION
</code>
</a>
statement, as
described previously. They can also be set directly using the
<a class="link" href="set-variable.html" title="15.7.6.1 SET Syntax for Variable Assignment">
<code class="literal">
SET
</code>
</a>
statement to assign values to the
<a class="link" href="server-system-variables.html#sysvar_transaction_isolation">
<code class="literal">
transaction_isolation
</code>
</a>
and
<a class="link" href="server-system-variables.html#sysvar_transaction_read_only">
<code class="literal">
transaction_read_only
</code>
</a>
system
variables:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<a class="link" href="set-transaction.html" title="15.3.7 SET TRANSACTION Statement">
<code class="literal">
SET TRANSACTION
</code>
</a>
permits
optional
<code class="literal">
GLOBAL
</code>
and
<code class="literal">
SESSION
</code>
keywords for setting transaction
characteristics at different scope levels.
</p>
</li>
<li class="listitem">
<p>
The
<a class="link" href="set-variable.html" title="15.7.6.1 SET Syntax for Variable Assignment">
<code class="literal">
SET
</code>
</a>
statement for assigning values to the
<a class="link" href="server-system-variables.html#sysvar_transaction_isolation">
<code class="literal">
transaction_isolation
</code>
</a>
and
<a class="link" href="server-system-variables.html#sysvar_transaction_read_only">
<code class="literal">
transaction_read_only
</code>
</a>
system variables has syntaxes for setting these variables at
different scope levels.
</p>
</li>
</ul>
</div>
<p>
The following tables show the characteristic scope level set by
each
<a class="link" href="set-transaction.html" title="15.3.7 SET TRANSACTION Statement">
<code class="literal">
SET TRANSACTION
</code>
</a>
and
variable-assignment syntax.
</p>
<div class="table">
<a name="set-transaction-characteristic-syntax">
</a>
<p class="title">
<b>
Table 15.9 SET TRANSACTION Syntax for Transaction Characteristics
</b>
</p>
<div class="table-contents">
<table summary="Syntax for setting transaction characteristics using SET TRANSACTION and affected scope.">
<colgroup>
<col style="width: 60%"/>
<col style="width: 40%"/>
</colgroup>
<thead>
<tr>
<th>
Syntax
</th>
<th>
Affected Characteristic Scope
</th>
</tr>
</thead>
<tbody>
<tr>
<td>
<code class="literal">
SET GLOBAL TRANSACTION
<em class="replaceable">
<code>
transaction_characteristic
</code>
</em>
</code>
</td>
<td>
Global
</td>
</tr>
<tr>
<td>
<code class="literal">
SET SESSION TRANSACTION
<em class="replaceable">
<code>
transaction_characteristic
</code>
</em>
</code>
</td>
<td>
Session
</td>
</tr>
<tr>
<td>
<code class="literal">
SET TRANSACTION
<em class="replaceable">
<code>
transaction_characteristic
</code>
</em>
</code>
</td>
<td>
Next transaction only
</td>
</tr>
</tbody>
</table>
</div>
</div>
<br class="table-break"/>
<div class="table">
<a name="set-variable-characteristic-syntax">
</a>
<p class="title">
<b>
Table 15.10 SET Syntax for Transaction Characteristics
</b>
</p>
<div class="table-contents">
<table summary="Syntax for setting transaction characteristics using SET and affected scope.">
<colgroup>
<col style="width: 60%"/>
<col style="width: 40%"/>
</colgroup>
<thead>
<tr>
<th>
Syntax
</th>
<th>
Affected Characteristic Scope
</th>
</tr>
</thead>
<tbody>
<tr>
<td>
<code class="literal">
SET GLOBAL
<em class="replaceable">
<code>
var_name
</code>
</em>
=
<em class="replaceable">
<code>
value
</code>
</em>
</code>
</td>
<td>
Global
</td>
</tr>
<tr>
<td>
<code class="literal">
SET @@GLOBAL.
<em class="replaceable">
<code>
var_name
</code>
</em>
=
<em class="replaceable">
<code>
value
</code>
</em>
</code>
</td>
<td>
Global
</td>
</tr>
<tr>
<td>
<code class="literal">
SET PERSIST
<em class="replaceable">
<code>
var_name
</code>
</em>
=
<em class="replaceable">
<code>
value
</code>
</em>
</code>
</td>
<td>
Global
</td>
</tr>
<tr>
<td>
<code class="literal">
SET @@PERSIST.
<em class="replaceable">
<code>
var_name
</code>
</em>
=
<em class="replaceable">
<code>
value
</code>
</em>
</code>
</td>
<td>
Global
</td>
</tr>
<tr>
<td>
<code class="literal">
SET PERSIST_ONLY
<em class="replaceable">
<code>
var_name
</code>
</em>
=
<em class="replaceable">
<code>
value
</code>
</em>
</code>
</td>
<td>
No runtime effect
</td>
</tr>
<tr>
<td>
<code class="literal">
SET @@PERSIST_ONLY.
<em class="replaceable">
<code>
var_name
</code>
</em>
=
<em class="replaceable">
<code>
value
</code>
</em>
</code>
</td>
<td>
No runtime effect
</td>
</tr>
<tr>
<td>
<code class="literal">
SET SESSION
<em class="replaceable">
<code>
var_name
</code>
</em>
=
<em class="replaceable">
<code>
value
</code>
</em>
</code>
</td>
<td>
Session
</td>
</tr>
<tr>
<td>
<code class="literal">
SET @@SESSION.
<em class="replaceable">
<code>
var_name
</code>
</em>
=
<em class="replaceable">
<code>
value
</code>
</em>
</code>
</td>
<td>
Session
</td>
</tr>
<tr>
<td>
<code class="literal">
SET
<em class="replaceable">
<code>
var_name
</code>
</em>
=
<em class="replaceable">
<code>
value
</code>
</em>
</code>
</td>
<td>
Session
</td>
</tr>
<tr>
<td>
<code class="literal">
SET @@
<em class="replaceable">
<code>
var_name
</code>
</em>
=
<em class="replaceable">
<code>
value
</code>
</em>
</code>
</td>
<td>
Next transaction only
</td>
</tr>
</tbody>
</table>
</div>
<div class="table-contents">
<table cellpadding="0" cellspacing="0" style="position: fixed; top: 0px; display: none; left: 401px; width: 540px;">
<thead>
<tr>
<th style="width: 323.438px;">
Syntax
</th>
<th style="width: 215.625px;">
Affected Characteristic Scope
</th>
</tr>
</thead>
</table>
</div>
</div>
<br class="table-break"/>
<p>
It is possible to check the global and session values of
transaction characteristics at runtime:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa89646443"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SELECT</span> <span class="token variable">@@GLOBAL.transaction_isolation</span><span class="token punctuation">,</span> <span class="token variable">@@GLOBAL.transaction_read_only</span><span class="token punctuation">;</span>
<span class="token keyword">SELECT</span> <span class="token variable">@@SESSION.transaction_isolation</span><span class="token punctuation">,</span> <span class="token variable">@@SESSION.transaction_read_only</span><span class="token punctuation">;</span></code></pre>
</div>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/x-plugin-encrypted-connections.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="x-plugin-encrypted-connections">
</a>
22.5.3 Using Encrypted Connections with X Plugin
</h3>
</div>
</div>
</div>
<p>
This section explains how to configure X Plugin to use encrypted
connections. For more background information, see
<a class="xref" href="encrypted-connections.html" title="8.3 Using Encrypted Connections">
Section 8.3, “Using Encrypted Connections”
</a>
.
</p>
<p>
To enable configuring support for encrypted connections, X Plugin
has
<code class="literal">
mysqlx_ssl_
<em class="replaceable">
<code>
xxx
</code>
</em>
</code>
system variables, which can have different values from the
<code class="literal">
ssl_
<em class="replaceable">
<code>
xxx
</code>
</em>
</code>
system
variables used with MySQL Server. For example, X Plugin can have
SSL key, certificate, and certificate authority files that differ
from those used for MySQL Server. These variables are described at
<a class="xref" href="x-plugin-options-system-variables.html" title="22.5.6.2 X Plugin Options and System Variables">
Section 22.5.6.2, “X Plugin Options and System Variables”
</a>
. Similarly,
X Plugin has its own
<code class="literal">
Mysqlx_ssl_
<em class="replaceable">
<code>
xxx
</code>
</em>
</code>
status variables that correspond to the MySQL Server
encrypted-connection
<code class="literal">
Ssl_
<em class="replaceable">
<code>
xxx
</code>
</em>
</code>
status
variables. See
<a class="xref" href="x-plugin-status-variables.html" title="22.5.6.3 X Plugin Status Variables">
Section 22.5.6.3, “X Plugin Status Variables”
</a>
.
</p>
<p>
At initialization, X Plugin determines its TLS context for
encrypted connections as follows:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
If all
<code class="literal">
mysqlx_ssl_
<em class="replaceable">
<code>
xxx
</code>
</em>
</code>
system variables have their default values, X Plugin uses the
same TLS context as the MySQL Server main connection
interface, which is determined by the values of the
<code class="literal">
ssl_
<em class="replaceable">
<code>
xxx
</code>
</em>
</code>
system
variables.
</p>
</li>
<li class="listitem">
<p>
If any
<code class="literal">
mysqlx_ssl_
<em class="replaceable">
<code>
xxx
</code>
</em>
</code>
variable has a nondefault value, X Plugin uses the TLS
context defined by the values of its own system variables.
(This is the case if any
<code class="literal">
mysqlx_ssl_
<em class="replaceable">
<code>
xxx
</code>
</em>
</code>
system variable is set to a value different from its default.)
</p>
</li>
</ul>
</div>
<p>
This means that, on a server with X Plugin enabled, you can
choose to have MySQL Protocol and X Protocol connections share
the same encryption configuration by setting only the
<code class="literal">
ssl_
<em class="replaceable">
<code>
xxx
</code>
</em>
</code>
variables,
or have separate encryption configurations for MySQL Protocol and
X Protocol connections by configuring the
<code class="literal">
ssl_
<em class="replaceable">
<code>
xxx
</code>
</em>
</code>
and
<code class="literal">
mysqlx_ssl_
<em class="replaceable">
<code>
xxx
</code>
</em>
</code>
variables separately.
</p>
<p>
To have MySQL Protocol and X Protocol connections use the same
encryption configuration, set only the
<code class="literal">
ssl_
<em class="replaceable">
<code>
xxx
</code>
</em>
</code>
system
variables in
<code class="filename">
my.cnf
</code>
:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-ini"><div class="docs-select-all right" id="sa80050261"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-ini"><span class="token selector">[mysqld]</span>
<span class="token constant">ssl_ca</span><span class="token attr-value"><span class="token punctuation">=</span>ca.pem</span>
<span class="token constant">ssl_cert</span><span class="token attr-value"><span class="token punctuation">=</span>server-cert.pem</span>
<span class="token constant">ssl_key</span><span class="token attr-value"><span class="token punctuation">=</span>server-key.pem</span></code></pre>
</div>
<p>
To configure encryption separately for MySQL Protocol and
X Protocol connections, set both the
<code class="literal">
ssl_
<em class="replaceable">
<code>
xxx
</code>
</em>
</code>
and
<code class="literal">
mysqlx_ssl_
<em class="replaceable">
<code>
xxx
</code>
</em>
</code>
system variables in
<code class="filename">
my.cnf
</code>
:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-ini"><div class="docs-select-all right" id="sa75845865"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-ini"><span class="token selector">[mysqld]</span>
<span class="token constant">ssl_ca</span><span class="token attr-value"><span class="token punctuation">=</span>ca1.pem</span>
<span class="token constant">ssl_cert</span><span class="token attr-value"><span class="token punctuation">=</span>server-cert1.pem</span>
<span class="token constant">ssl_key</span><span class="token attr-value"><span class="token punctuation">=</span>server-key1.pem</span>
<span class="token constant">mysqlx_ssl_ca</span><span class="token attr-value"><span class="token punctuation">=</span>ca2.pem</span>
<span class="token constant">mysqlx_ssl_cert</span><span class="token attr-value"><span class="token punctuation">=</span>server-cert2.pem</span>
<span class="token constant">mysqlx_ssl_key</span><span class="token attr-value"><span class="token punctuation">=</span>server-key2.pem</span></code></pre>
</div>
<p>
For general information about configuring connection-encryption
support, see
<a class="xref" href="using-encrypted-connections.html" title="8.3.1 Configuring MySQL to Use Encrypted Connections">
Section 8.3.1, “Configuring MySQL to Use Encrypted Connections”
</a>
. That
discussion is written for MySQL Server, but the parameter names
are similar for X Plugin. (The X Plugin
<code class="literal">
mysqlx_ssl_
<em class="replaceable">
<code>
xxx
</code>
</em>
</code>
system variable names correspond to the MySQL Server
<code class="literal">
ssl_
<em class="replaceable">
<code>
xxx
</code>
</em>
</code>
system
variable names.)
</p>
<p>
The
<a class="link" href="server-system-variables.html#sysvar_tls_version">
<code class="literal">
tls_version
</code>
</a>
system variable
that determines the permitted TLS versions for MySQL Protocol
connections also applies to X Protocol connections. The permitted
TLS versions for both types of connections are therefore the same.
</p>
<p>
Encryption per connection is optional, but a specific user can be
required to use encryption for X Protocol and MySQL Protocol
connections by including an appropriate
<code class="literal">
REQUIRE
</code>
clause in the
<a class="link" href="create-user.html" title="15.7.1.3 CREATE USER Statement">
<code class="literal">
CREATE USER
</code>
</a>
statement
that creates the user. For details, see
<a class="xref" href="create-user.html" title="15.7.1.3 CREATE USER Statement">
Section 15.7.1.3, “CREATE USER Statement”
</a>
. Alternatively, to require all users
to use encryption for X Protocol and MySQL Protocol connections,
enable the
<a class="link" href="server-system-variables.html#sysvar_require_secure_transport">
<code class="literal">
require_secure_transport
</code>
</a>
system
variable. For additional information, see
<a class="xref" href="using-encrypted-connections.html#mandatory-encrypted-connections" title="Configuring Encrypted Connections as Mandatory">
Configuring Encrypted Connections as Mandatory
</a>
.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/replication-features-errors.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="replication-features-errors">
</a>
19.5.1.29 Replica Errors During Replication
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045135163632">
</a>
<a class="indexterm" name="idm46045135162144">
</a>
<a class="indexterm" name="idm46045135160656">
</a>
<a class="indexterm" name="idm46045135159168">
</a>
<p>
If a statement produces the same error (identical error code) on
both the source and the replica, the error is logged, but
replication continues.
</p>
<p>
If a statement produces different errors on the source and the
replica, the replication SQL thread terminates, and the replica
writes a message to its error log and waits for the database
administrator to decide what to do about the error. This
includes the case that a statement produces an error on the
source or the replica, but not both. To address the issue,
connect to the replica manually and determine the cause of the
problem.
<a class="link" href="show-replica-status.html" title="15.7.7.35 SHOW REPLICA STATUS Statement">
<code class="literal">
SHOW REPLICA STATUS
</code>
</a>
is
useful for this. Then fix the problem and run
<a class="link" href="start-replica.html" title="15.4.2.4 START REPLICA Statement">
<code class="literal">
START REPLICA
</code>
</a>
. For example, you
might need to create a nonexistent table before you can start
the replica again.
</p>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
If a temporary error is recorded in the replica's error log,
you do not necessarily have to take any action suggested in
the quoted error message. Temporary errors should be handled
by the client retrying the transaction. For example, if the
replication SQL thread records a temporary error relating to
a deadlock, you do not need to restart the transaction
manually on the replica, unless the replication SQL thread
subsequently terminates with a nontemporary error message.
</p>
</div>
<p>
</p>
<p>
If this error code validation behavior is not desirable, some or
all errors can be masked out (ignored) with the
<a class="link" href="replication-options-replica.html#sysvar_replica_skip_errors">
<code class="option">
--replica-skip-errors
</code>
</a>
option.
</p>
<p>
For nontransactional storage engines such as
<a class="link" href="myisam-storage-engine.html" title="18.2 The MyISAM Storage Engine">
<code class="literal">
MyISAM
</code>
</a>
, it is possible to have a
statement that only partially updates a table and returns an
error code. This can happen, for example, on a multiple-row
insert that has one row violating a key constraint, or if a long
update statement is killed after updating some of the rows. If
that happens on the source, the replica expects execution of the
statement to result in the same error code. If it does not, the
replication SQL thread stops as described previously.
</p>
<p>
If you are replicating between tables that use different storage
engines on the source and replica, keep in mind that the same
statement might produce a different error when run against one
version of the table, but not the other, or might cause an error
for one version of the table, but not the other. For example,
since
<code class="literal">
MyISAM
</code>
ignores foreign key constraints,
an
<a class="link" href="insert.html" title="15.2.7 INSERT Statement">
<code class="literal">
INSERT
</code>
</a>
or
<a class="link" href="update.html" title="15.2.17 UPDATE Statement">
<code class="literal">
UPDATE
</code>
</a>
statement accessing an
<code class="literal">
InnoDB
</code>
table on the source might cause a
foreign key violation but the same statement performed on a
<code class="literal">
MyISAM
</code>
version of the same table on the
replica would produce no such error, causing replication to
stop.
</p>
<p>
Replication filter rules are applied first, prior to making any
privilege or row format checks, making it possible to filter out
any transactions that fail validation; no checks are performed
and thus no errors are raised for transactions which have been
filtered out. This means that the replica can accept only that
part of the database to which a given user has been granted
access (as long as any updates to this part of the database use
the row-based replication format). This may be helpful when
performing an upgrade or when migrating to a system or
application that uses administration tables to which the inbound
replication user does not have access. See also
<a class="xref" href="replication-rules.html" title="19.2.5 How Servers Evaluate Replication Filtering Rules">
Section 19.2.5, “How Servers Evaluate Replication Filtering Rules”
</a>
.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/x-plugin-system-monitoring.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="x-plugin-system-monitoring">
</a>
22.5.7 Monitoring X Plugin
</h3>
</div>
</div>
</div>
<p>
For general X Plugin monitoring, use the status variables that it
exposes. See
<a class="xref" href="x-plugin-status-variables.html" title="22.5.6.3 X Plugin Status Variables">
Section 22.5.6.3, “X Plugin Status Variables”
</a>
. For
information specifically about monitoring the effects of message
compression, see
<a class="xref" href="x-plugin-connection-compression.html#x-plugin-connection-compression-monitoring" title="Monitoring Connection Compression for X Plugin">
Monitoring Connection Compression for X Plugin
</a>
.
</p>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h4 class="title">
<a name="x-plugin-generated-statements">
</a>
Monitoring SQL Generated by X Plugin
</h4>
</div>
</div>
</div>
<p>
This section describes how to monitor the SQL statements which
X Plugin generates when you run X DevAPI operations. When you
execute a CRUD statement, it is translated into SQL and executed
against the server. To be able to monitor the generated SQL, the
Performance Schema tables must be enabled. The SQL is registered
under the
<a class="link" href="performance-schema-events-statements-current-table.html" title="29.12.6.1 The events_statements_current Table">
<code class="literal">
performance_schema.events_statements_current
</code>
</a>
,
<a class="link" href="performance-schema-events-statements-history-table.html" title="29.12.6.2 The events_statements_history Table">
<code class="literal">
performance_schema.events_statements_history
</code>
</a>
,
and
<a class="link" href="performance-schema-events-statements-history-long-table.html" title="29.12.6.3 The events_statements_history_long Table">
<code class="literal">
performance_schema.events_statements_history_long
</code>
</a>
tables. The following example uses the
<code class="literal">
world_x
</code>
schema, imported as part of the
quickstart tutorials in this section. We use MySQL Shell in
Python mode, and the
<code class="literal">
\sql
</code>
command which
enables you to issue SQL statements without changing to SQL
mode. This is important, because if you instead try to switch to
SQL mode, the procedure shows the result of this operation
rather than the X DevAPI operation. The
<code class="literal">
\sql
</code>
command is used in the same way if you are using MySQL Shell in
JavaScript mode.
</p>
<div class="orderedlist">
<ol class="orderedlist" type="1">
<li class="listitem">
<p>
Check if the
<code class="literal">
events_statements_history
</code>
consumer is enabled. Issue:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-mysqlsh"><div class="docs-select-all right" id="sa22698618"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-mysqlsh"><span class="token prompt">mysql-py></span> \sql SELECT enabled FROM performance_schema<span class="token punctuation">.</span>setup_consumers WHERE NAME <span class="token operator">=</span> <span class="token string">'events_statements_history'</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> enabled <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> YES <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
</div>
</li>
<li class="listitem">
<p>
Check if all instruments report data to the consumer. Issue:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-mysqlsh"><div class="docs-select-all right" id="sa45184430"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-mysqlsh"><span class="token prompt">mysql-py></span> \sql SELECT NAME<span class="token punctuation">,</span> ENABLED<span class="token punctuation">,</span> TIMED FROM performance_schema<span class="token punctuation">.</span>setup_instruments WHERE NAME LIKE <span class="token string">'statement/%'</span> AND NOT <span class="token punctuation">(</span>ENABLED and TIMED<span class="token punctuation">)</span></code></pre>
</div>
<p>
If this statement reports at least one row, you need to
enable the instruments. See
<a class="xref" href="performance-schema-runtime-configuration.html" title="29.4 Performance Schema Runtime Configuration">
Section 29.4, “Performance Schema Runtime Configuration”
</a>
.
</p>
</li>
<li class="listitem">
<p>
Get the thread ID of the current connection. Issue:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-mysqlsh"><div class="docs-select-all right" id="sa51018284"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-mysqlsh"><span class="token prompt">mysql-py></span> \sql SELECT thread_id INTO @id FROM performance_schema<span class="token punctuation">.</span>threads WHERE processlist_id<span class="token operator">=</span><span class="token function">connection_id</span><span class="token punctuation">(</span><span class="token punctuation">)</span></code></pre>
</div>
</li>
<li class="listitem">
<p>
Execute the X DevAPI CRUD operation for which you want to
see the generated SQL. For example, issue:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-mysqlsh"><div class="docs-select-all right" id="sa28678093"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-mysqlsh"><span class="token prompt">mysql-py></span> db<span class="token punctuation">.</span>CountryInfo<span class="token punctuation">.</span><span class="token function">find</span><span class="token punctuation">(</span><span class="token string">"Name = :country"</span><span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">bind</span><span class="token punctuation">(</span><span class="token string">"country"</span><span class="token punctuation">,</span> <span class="token string">"Italy"</span><span class="token punctuation">)</span></code></pre>
</div>
<p>
You must not issue any further operations for the next step
to show the correct result.
</p>
</li>
<li class="listitem">
<p>
Show the last SQL query made by this thread ID. Issue:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-mysqlsh"><div class="docs-select-all right" id="sa86832275"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-mysqlsh"><span class="token prompt">mysql-py></span> \sql SELECT THREAD_ID<span class="token punctuation">,</span> MYSQL_ERRNO<span class="token punctuation">,</span>SQL_TEXT FROM performance_schema<span class="token punctuation">.</span>events_statements_history WHERE THREAD_ID<span class="token operator">=</span>@id ORDER BY TIMER_START DESC LIMIT <span class="token number">1</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> THREAD_ID <span class="token punctuation">|</span> MYSQL_ERRNO <span class="token punctuation">|</span> SQL_TEXT <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 29 <span class="token punctuation">|</span> 0 <span class="token punctuation">|</span> SELECT doc FROM `world_x`.`CountryInfo` WHERE (JSON_EXTRACT(doc,'$.Name') = 'Italy') <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
</div>
<p>
The result shows the SQL generated by X Plugin based on the
most recent statement, in this case the X DevAPI CRUD
operation from the previous step.
</p>
</li>
</ol>
</div>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/other-vendor-data-types.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h2 class="title">
<a name="other-vendor-data-types">
</a>
13.9 Using Data Types from Other Database Engines
</h2>
</div>
</div>
</div>
<a class="indexterm" name="idm46045210375504">
</a>
<a class="indexterm" name="idm46045210374048">
</a>
<a class="indexterm" name="idm46045210372560">
</a>
<a class="indexterm" name="idm46045210371072">
</a>
<a class="indexterm" name="idm46045210369584">
</a>
<p>
To facilitate the use of code written for SQL implementations from
other vendors, MySQL maps data types as shown in the following
table. These mappings make it easier to import table definitions
from other database systems into MySQL.
</p>
<div class="informaltable">
<table summary="Mapping of MySQL data types to data types from other vendors.">
<colgroup>
<col style="width: 35%"/>
<col style="width: 55%"/>
</colgroup>
<thead>
<tr>
<th>
Other Vendor Type
</th>
<th>
MySQL Type
</th>
</tr>
</thead>
<tbody>
<tr>
<td>
<a class="link" href="integer-types.html" title="13.1.2 Integer Types (Exact Value) - INTEGER, INT, SMALLINT, TINYINT, MEDIUMINT, BIGINT">
<code class="literal">
BOOL
</code>
</a>
</td>
<td>
<a class="link" href="integer-types.html" title="13.1.2 Integer Types (Exact Value) - INTEGER, INT, SMALLINT, TINYINT, MEDIUMINT, BIGINT">
<code class="literal">
TINYINT
</code>
</a>
</td>
</tr>
<tr>
<td>
<a class="link" href="integer-types.html" title="13.1.2 Integer Types (Exact Value) - INTEGER, INT, SMALLINT, TINYINT, MEDIUMINT, BIGINT">
<code class="literal">
BOOLEAN
</code>
</a>
</td>
<td>
<a class="link" href="integer-types.html" title="13.1.2 Integer Types (Exact Value) - INTEGER, INT, SMALLINT, TINYINT, MEDIUMINT, BIGINT">
<code class="literal">
TINYINT
</code>
</a>
</td>
</tr>
<tr>
<td>
<code class="literal">
CHARACTER VARYING(
<em class="replaceable">
<code>
M
</code>
</em>
)
</code>
</td>
<td>
<code class="literal">
VARCHAR(
<em class="replaceable">
<code>
M
</code>
</em>
)
</code>
</td>
</tr>
<tr>
<td>
<a class="link" href="fixed-point-types.html" title="13.1.3 Fixed-Point Types (Exact Value) - DECIMAL, NUMERIC">
<code class="literal">
FIXED
</code>
</a>
</td>
<td>
<a class="link" href="fixed-point-types.html" title="13.1.3 Fixed-Point Types (Exact Value) - DECIMAL, NUMERIC">
<code class="literal">
DECIMAL
</code>
</a>
</td>
</tr>
<tr>
<td>
<a class="link" href="floating-point-types.html" title="13.1.4 Floating-Point Types (Approximate Value) - FLOAT, DOUBLE">
<code class="literal">
FLOAT4
</code>
</a>
</td>
<td>
<a class="link" href="floating-point-types.html" title="13.1.4 Floating-Point Types (Approximate Value) - FLOAT, DOUBLE">
<code class="literal">
FLOAT
</code>
</a>
</td>
</tr>
<tr>
<td>
<a class="link" href="floating-point-types.html" title="13.1.4 Floating-Point Types (Approximate Value) - FLOAT, DOUBLE">
<code class="literal">
FLOAT8
</code>
</a>
</td>
<td>
<a class="link" href="floating-point-types.html" title="13.1.4 Floating-Point Types (Approximate Value) - FLOAT, DOUBLE">
<code class="literal">
DOUBLE
</code>
</a>
</td>
</tr>
<tr>
<td>
<a class="link" href="integer-types.html" title="13.1.2 Integer Types (Exact Value) - INTEGER, INT, SMALLINT, TINYINT, MEDIUMINT, BIGINT">
<code class="literal">
INT1
</code>
</a>
</td>
<td>
<a class="link" href="integer-types.html" title="13.1.2 Integer Types (Exact Value) - INTEGER, INT, SMALLINT, TINYINT, MEDIUMINT, BIGINT">
<code class="literal">
TINYINT
</code>
</a>
</td>
</tr>
<tr>
<td>
<a class="link" href="integer-types.html" title="13.1.2 Integer Types (Exact Value) - INTEGER, INT, SMALLINT, TINYINT, MEDIUMINT, BIGINT">
<code class="literal">
INT2
</code>
</a>
</td>
<td>
<a class="link" href="integer-types.html" title="13.1.2 Integer Types (Exact Value) - INTEGER, INT, SMALLINT, TINYINT, MEDIUMINT, BIGINT">
<code class="literal">
SMALLINT
</code>
</a>
</td>
</tr>
<tr>
<td>
<a class="link" href="integer-types.html" title="13.1.2 Integer Types (Exact Value) - INTEGER, INT, SMALLINT, TINYINT, MEDIUMINT, BIGINT">
<code class="literal">
INT3
</code>
</a>
</td>
<td>
<a class="link" href="integer-types.html" title="13.1.2 Integer Types (Exact Value) - INTEGER, INT, SMALLINT, TINYINT, MEDIUMINT, BIGINT">
<code class="literal">
MEDIUMINT
</code>
</a>
</td>
</tr>
<tr>
<td>
<a class="link" href="integer-types.html" title="13.1.2 Integer Types (Exact Value) - INTEGER, INT, SMALLINT, TINYINT, MEDIUMINT, BIGINT">
<code class="literal">
INT4
</code>
</a>
</td>
<td>
<a class="link" href="integer-types.html" title="13.1.2 Integer Types (Exact Value) - INTEGER, INT, SMALLINT, TINYINT, MEDIUMINT, BIGINT">
<code class="literal">
INT
</code>
</a>
</td>
</tr>
<tr>
<td>
<code class="literal">
INT8
</code>
</td>
<td>
<a class="link" href="integer-types.html" title="13.1.2 Integer Types (Exact Value) - INTEGER, INT, SMALLINT, TINYINT, MEDIUMINT, BIGINT">
<code class="literal">
BIGINT
</code>
</a>
</td>
</tr>
<tr>
<td>
<code class="literal">
LONG VARBINARY
</code>
</td>
<td>
<a class="link" href="blob.html" title="13.3.4 The BLOB and TEXT Types">
<code class="literal">
MEDIUMBLOB
</code>
</a>
</td>
</tr>
<tr>
<td>
<code class="literal">
LONG VARCHAR
</code>
</td>
<td>
<a class="link" href="blob.html" title="13.3.4 The BLOB and TEXT Types">
<code class="literal">
MEDIUMTEXT
</code>
</a>
</td>
</tr>
<tr>
<td>
<code class="literal">
LONG
</code>
</td>
<td>
<a class="link" href="blob.html" title="13.3.4 The BLOB and TEXT Types">
<code class="literal">
MEDIUMTEXT
</code>
</a>
</td>
</tr>
<tr>
<td>
<a class="link" href="integer-types.html" title="13.1.2 Integer Types (Exact Value) - INTEGER, INT, SMALLINT, TINYINT, MEDIUMINT, BIGINT">
<code class="literal">
MIDDLEINT
</code>
</a>
</td>
<td>
<a class="link" href="integer-types.html" title="13.1.2 Integer Types (Exact Value) - INTEGER, INT, SMALLINT, TINYINT, MEDIUMINT, BIGINT">
<code class="literal">
MEDIUMINT
</code>
</a>
</td>
</tr>
<tr>
<td>
<a class="link" href="fixed-point-types.html" title="13.1.3 Fixed-Point Types (Exact Value) - DECIMAL, NUMERIC">
<code class="literal">
NUMERIC
</code>
</a>
</td>
<td>
<a class="link" href="fixed-point-types.html" title="13.1.3 Fixed-Point Types (Exact Value) - DECIMAL, NUMERIC">
<code class="literal">
DECIMAL
</code>
</a>
</td>
</tr>
</tbody>
</table>
</div>
<div class="informaltable">
<table cellpadding="0" cellspacing="0" style="position: fixed; top: 0px; display: none; left: 401px; width: 490px;">
<thead>
<tr>
<th style="width: 190.125px;">
Other Vendor Type
</th>
<th style="width: 298.797px;">
MySQL Type
</th>
</tr>
</thead>
</table>
</div>
<p>
Data type mapping occurs at table creation time, after which the
original type specifications are discarded. If you create a table
with types used by other vendors and then issue a
<code class="literal">
DESCRIBE
<em class="replaceable">
<code>
tbl_name
</code>
</em>
</code>
statement, MySQL reports the table structure using the equivalent
MySQL types. For example:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa34805913"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">CREATE</span> <span class="token keyword">TABLE</span> t <span class="token punctuation">(</span>a <span class="token datatype">BOOL</span><span class="token punctuation">,</span> b <span class="token keyword">FLOAT8</span><span class="token punctuation">,</span> c <span class="token keyword">LONG</span> <span class="token datatype">VARCHAR</span><span class="token punctuation">,</span> d <span class="token datatype">NUMERIC</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output">Query OK, 0 rows affected (0.00 sec)</span>
<span class="token prompt">mysql></span> <span class="token keyword">DESCRIBE</span> t<span class="token punctuation">;</span>
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<span class="token output">4 rows in set (0.01 sec)</span></code></pre>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/cost-model.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="cost-model">
</a>
10.9.5 The Optimizer Cost Model
</h3>
</div>
</div>
</div>
<a class="indexterm" name="idm46045223352240">
</a>
<a class="indexterm" name="idm46045223350784">
</a>
<p>
To generate execution plans, the optimizer uses a cost model
that is based on estimates of the cost of various operations
that occur during query execution. The optimizer has a set of
compiled-in default
<span class="quote">
“
<span class="quote">
cost constants
</span>
”
</span>
available to
it to make decisions regarding execution plans.
</p>
<p>
The optimizer also has a database of cost estimates to use
during execution plan construction. These estimates are stored
in the
<code class="literal">
server_cost
</code>
and
<code class="literal">
engine_cost
</code>
tables in the
<code class="literal">
mysql
</code>
system database and are configurable at
any time. The intent of these tables is to make it possible to
easily adjust the cost estimates that the optimizer uses when it
attempts to arrive at query execution plans.
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<a class="xref" href="cost-model.html#cost-model-operation" title="Cost Model General Operation">
Cost Model General Operation
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="cost-model.html#cost-model-database" title="The Cost Model Database">
The Cost Model Database
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="cost-model.html#cost-model-database-modifications" title="Making Changes to the Cost Model Database">
Making Changes to the Cost Model Database
</a>
</p>
</li>
</ul>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h4 class="title">
<a name="cost-model-operation">
</a>
Cost Model General Operation
</h4>
</div>
</div>
</div>
<p>
The configurable optimizer cost model works like this:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
The server reads the cost model tables into memory at
startup and uses the in-memory values at runtime. Any
non-
<code class="literal">
NULL
</code>
cost estimate specified in the
tables takes precedence over the corresponding compiled-in
default cost constant. Any
<code class="literal">
NULL
</code>
estimate indicates to the optimizer to use the compiled-in
default.
</p>
</li>
<li class="listitem">
<p>
At runtime, the server may re-read the cost tables. This
occurs when a storage engine is dynamically loaded or when
a
<a class="link" href="flush.html#flush-optimizer-costs">
<code class="literal">
FLUSH OPTIMIZER_COSTS
</code>
</a>
statement is executed.
</p>
</li>
<li class="listitem">
<p>
Cost tables enable server administrators to easily adjust
cost estimates by changing entries in the tables. It is
also easy to revert to a default by setting an
entry's cost to
<code class="literal">
NULL
</code>
. The
optimizer uses the in-memory cost values, so changes to
the tables should be followed by
<a class="link" href="flush.html#flush-optimizer-costs">
<code class="literal">
FLUSH OPTIMIZER_COSTS
</code>
</a>
to
take effect.
</p>
</li>
<li class="listitem">
<p>
The in-memory cost estimates that are current when a
client session begins apply throughout that session until
it ends. In particular, if the server re-reads the cost
tables, any changed estimates apply only to subsequently
started sessions. Existing sessions are unaffected.
</p>
</li>
<li class="listitem">
<p>
Cost tables are specific to a given server instance. The
server does not replicate cost table changes to replicas.
</p>
</li>
</ul>
</div>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h4 class="title">
<a name="cost-model-database">
</a>
The Cost Model Database
</h4>
</div>
</div>
</div>
<p>
The optimizer cost model database consists of two tables in
the
<code class="literal">
mysql
</code>
system database that contain cost
estimate information for operations that occur during query
execution:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<a class="indexterm" name="idm46045223326544">
</a>
<a class="indexterm" name="idm46045223325056">
</a>
<code class="literal">
server_cost
</code>
: Optimizer cost estimates
for general server operations
</p>
</li>
<li class="listitem">
<p>
<a class="indexterm" name="idm46045223322016">
</a>
<a class="indexterm" name="idm46045223320528">
</a>
<code class="literal">
engine_cost
</code>
: Optimizer cost estimates
for operations specific to particular storage engines
</p>
</li>
</ul>
</div>
<p>
The
<code class="literal">
server_cost
</code>
table contains these
columns:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<code class="literal">
cost_name
</code>
</p>
<p>
The name of a cost estimate used in the cost model. The
name is not case-sensitive. If the server does not
recognize the cost name when it reads this table, it
writes a warning to the error log.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
cost_value
</code>
</p>
<p>
The cost estimate value. If the value is
non-
<code class="literal">
NULL
</code>
, the server uses it as the
cost. Otherwise, it uses the default estimate (the
compiled-in value). DBAs can change a cost estimate by
updating this column. If the server finds that the cost
value is invalid (nonpositive) when it reads this table,
it writes a warning to the error log.
</p>
<p>
To override a default cost estimate (for an entry that
specifies
<code class="literal">
NULL
</code>
), set the cost to a
non-
<code class="literal">
NULL
</code>
value. To revert to the
default, set the value to
<code class="literal">
NULL
</code>
. Then
execute
<a class="link" href="flush.html#flush-optimizer-costs">
<code class="literal">
FLUSH
OPTIMIZER_COSTS
</code>
</a>
to tell the server to re-read
the cost tables.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
last_update
</code>
</p>
<p>
The time of the last row update.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
comment
</code>
</p>
<p>
A descriptive comment associated with the cost estimate.
DBAs can use this column to provide information about why
a cost estimate row stores a particular value.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
default_value
</code>
</p>
<p>
The default (compiled-in) value for the cost estimate.
This column is a read-only generated column that retains
its value even if the associated cost estimate is changed.
For rows added to the table at runtime, the value of this
column is
<code class="literal">
NULL
</code>
.
</p>
</li>
</ul>
</div>
<p>
The primary key for the
<code class="literal">
server_cost
</code>
table
is the
<code class="literal">
cost_name
</code>
column, so it is not
possible to create multiple entries for any cost estimate.
</p>
<p>
The server recognizes these
<code class="literal">
cost_name
</code>
values for the
<code class="literal">
server_cost
</code>
table:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<code class="literal">
disk_temptable_create_cost
</code>
,
<code class="literal">
disk_temptable_row_cost
</code>
</p>
<p>
The cost estimates for internally created temporary tables
stored in a disk-based storage engine (either
<code class="literal">
InnoDB
</code>
or
<code class="literal">
MyISAM
</code>
).
Increasing these values increases the cost estimate of
using internal temporary tables and makes the optimizer
prefer query plans with less use of them. For information
about such tables, see
<a class="xref" href="internal-temporary-tables.html" title="10.4.4 Internal Temporary Table Use in MySQL">
Section 10.4.4, “Internal Temporary Table Use in MySQL”
</a>
.
</p>
<p>
The larger default values for these disk parameters
compared to the default values for the corresponding
memory parameters
(
<code class="literal">
memory_temptable_create_cost
</code>
,
<code class="literal">
memory_temptable_row_cost
</code>
) reflects the
greater cost of processing disk-based tables.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
key_compare_cost
</code>
</p>
<a class="indexterm" name="idm46045223287536">
</a>
<a class="indexterm" name="idm46045223286464">
</a>
<p>
The cost of comparing record keys. Increasing this value
causes a query plan that compares many keys to become more
expensive. For example, a query plan that performs a
<code class="literal">
filesort
</code>
becomes relatively more
expensive compared to a query plan that avoids sorting by
using an index.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
memory_temptable_create_cost
</code>
,
<code class="literal">
memory_temptable_row_cost
</code>
</p>
<p>
The cost estimates for internally created temporary tables
stored in the
<code class="literal">
MEMORY
</code>
storage engine.
Increasing these values increases the cost estimate of
using internal temporary tables and makes the optimizer
prefer query plans with less use of them. For information
about such tables, see
<a class="xref" href="internal-temporary-tables.html" title="10.4.4 Internal Temporary Table Use in MySQL">
Section 10.4.4, “Internal Temporary Table Use in MySQL”
</a>
.
</p>
<p>
The smaller default values for these memory parameters
compared to the default values for the corresponding disk
parameters (
<code class="literal">
disk_temptable_create_cost
</code>
,
<code class="literal">
disk_temptable_row_cost
</code>
) reflects the
lesser cost of processing memory-based tables.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
row_evaluate_cost
</code>
</p>
<p>
The cost of evaluating record conditions. Increasing this
value causes a query plan that examines many rows to
become more expensive compared to a query plan that
examines fewer rows. For example, a table scan becomes
relatively more expensive compared to a range scan that
reads fewer rows.
</p>
</li>
</ul>
</div>
<p>
The
<code class="literal">
engine_cost
</code>
table contains these
columns:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<code class="literal">
engine_name
</code>
</p>
<p>
The name of the storage engine to which this cost estimate
applies. The name is not case-sensitive. If the value is
<code class="literal">
default
</code>
, it applies to all storage
engines that have no named entry of their own. If the
server does not recognize the engine name when it reads
this table, it writes a warning to the error log.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
device_type
</code>
</p>
<p>
The device type to which this cost estimate applies. The
column is intended for specifying different cost estimates
for different storage device types, such as hard disk
drives versus solid state drives. Currently, this
information is not used and 0 is the only permitted value.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
cost_name
</code>
</p>
<p>
Same as in the
<code class="literal">
server_cost
</code>
table.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
cost_value
</code>
</p>
<p>
Same as in the
<code class="literal">
server_cost
</code>
table.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
last_update
</code>
</p>
<p>
Same as in the
<code class="literal">
server_cost
</code>
table.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
comment
</code>
</p>
<p>
Same as in the
<code class="literal">
server_cost
</code>
table.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
default_value
</code>
</p>
<p>
The default (compiled-in) value for the cost estimate.
This column is a read-only generated column that retains
its value even if the associated cost estimate is changed.
For rows added to the table at runtime, the value of this
column is
<code class="literal">
NULL
</code>
, with the exception that
if the row has the same
<code class="literal">
cost_name
</code>
value
as one of the original rows, the
<code class="literal">
default_value
</code>
column has the same value
as that row.
</p>
</li>
</ul>
</div>
<p>
The primary key for the
<code class="literal">
engine_cost
</code>
table
is a tuple comprising the (
<code class="literal">
cost_name
</code>
,
<code class="literal">
engine_name
</code>
,
<code class="literal">
device_type
</code>
) columns, so it is not possible
to create multiple entries for any combination of values in
those columns.
</p>
<p>
The server recognizes these
<code class="literal">
cost_name
</code>
values for the
<code class="literal">
engine_cost
</code>
table:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<code class="literal">
io_block_read_cost
</code>
</p>
<p>
The cost of reading an index or data block from disk.
Increasing this value causes a query plan that reads many
disk blocks to become more expensive compared to a query
plan that reads fewer disk blocks. For example, a table
scan becomes relatively more expensive compared to a range
scan that reads fewer blocks.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
memory_block_read_cost
</code>
</p>
<p>
Similar to
<code class="literal">
io_block_read_cost
</code>
, but
represents the cost of reading an index or data block from
an in-memory database buffer.
</p>
</li>
</ul>
</div>
<p>
If the
<code class="literal">
io_block_read_cost
</code>
and
<code class="literal">
memory_block_read_cost
</code>
values differ, the
execution plan may change between two runs of the same query.
Suppose that the cost for memory access is less than the cost
for disk access. In that case, at server startup before data
has been read into the buffer pool, you may get a different
plan than after the query has been run because then the data
is in memory.
</p>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h4 class="title">
<a name="cost-model-database-modifications">
</a>
Making Changes to the Cost Model Database
</h4>
</div>
</div>
</div>
<p>
For DBAs who wish to change the cost model parameters from
their defaults, try doubling or halving the value and
measuring the effect.
</p>
<p>
Changes to the
<code class="literal">
io_block_read_cost
</code>
and
<code class="literal">
memory_block_read_cost
</code>
parameters are most
likely to yield worthwhile results. These parameter values
enable cost models for data access methods to take into
account the costs of reading information from different
sources; that is, the cost of reading information from disk
versus reading information already in a memory buffer. For
example, all other things being equal, setting
<code class="literal">
io_block_read_cost
</code>
to a value larger than
<code class="literal">
memory_block_read_cost
</code>
causes the optimizer
to prefer query plans that read information already held in
memory to plans that must read from disk.
</p>
<p>
This example shows how to change the default value for
<code class="literal">
io_block_read_cost
</code>
:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa91188971"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">UPDATE</span> mysql<span class="token punctuation">.</span>engine_cost
<span class="token keyword">SET</span> cost_value <span class="token operator">=</span> <span class="token number">2.0</span>
<span class="token keyword">WHERE</span> cost_name <span class="token operator">=</span> <span class="token string">'io_block_read_cost'</span><span class="token punctuation">;</span>
<span class="token keyword">FLUSH</span> <span class="token keyword">OPTIMIZER_COSTS</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
This example shows how to change the value of
<code class="literal">
io_block_read_cost
</code>
only for the
<code class="literal">
InnoDB
</code>
storage engine:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa89095771"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">INSERT</span> <span class="token keyword">INTO</span> mysql<span class="token punctuation">.</span>engine_cost
<span class="token keyword">VALUES</span> <span class="token punctuation">(</span><span class="token string">'InnoDB'</span><span class="token punctuation">,</span> <span class="token number">0</span><span class="token punctuation">,</span> <span class="token string">'io_block_read_cost'</span><span class="token punctuation">,</span> <span class="token number">3.0</span><span class="token punctuation">,</span>
<span class="token keyword">CURRENT_TIMESTAMP</span><span class="token punctuation">,</span> <span class="token string">'Using a slower disk for InnoDB'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token keyword">FLUSH</span> <span class="token keyword">OPTIMIZER_COSTS</span><span class="token punctuation">;</span></code></pre>
</div>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/performance-schema-option-variable-reference.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h2 class="title">
<a name="performance-schema-option-variable-reference">
</a>
29.13 Performance Schema Option and Variable Reference
</h2>
</div>
</div>
</div>
<div class="table">
<a name="idm46045066915600">
</a>
<p class="title">
<b>
Table 29.16 Performance Schema Variable Reference
</b>
</p>
<div class="table-contents">
<table frame="box" rules="all" summary="Reference for Performance Schema command-line options, system variables, and status variables.">
<colgroup>
<col style="width: 20%"/>
<col style="width: 15%"/>
<col style="width: 15%"/>
<col style="width: 15%"/>
<col style="width: 15%"/>
<col style="width: 15%"/>
<col style="width: 15%"/>
</colgroup>
<thead>
<tr>
<th scope="col">
Name
</th>
<th scope="col">
Cmd-Line
</th>
<th scope="col">
Option File
</th>
<th scope="col">
System Var
</th>
<th scope="col">
Status Var
</th>
<th scope="col">
Var Scope
</th>
<th scope="col">
Dynamic
</th>
</tr>
</thead>
<tbody>
<tr>
<th scope="row">
<a class="link" href="performance-schema-system-variables.html#sysvar_performance_schema">
performance_schema
</a>
</th>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
</td>
<td>
Global
</td>
<td>
No
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="performance-schema-status-variables.html#statvar_Performance_schema_accounts_lost">
Performance_schema_accounts_lost
</a>
</th>
<td>
</td>
<td>
</td>
<td>
</td>
<td>
Yes
</td>
<td>
Global
</td>
<td>
No
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="performance-schema-system-variables.html#sysvar_performance_schema_accounts_size">
performance_schema_accounts_size
</a>
</th>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
</td>
<td>
Global
</td>
<td>
No
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="performance-schema-status-variables.html#statvar_Performance_schema_cond_classes_lost">
Performance_schema_cond_classes_lost
</a>
</th>
<td>
</td>
<td>
</td>
<td>
</td>
<td>
Yes
</td>
<td>
Global
</td>
<td>
No
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="performance-schema-status-variables.html#statvar_Performance_schema_cond_instances_lost">
Performance_schema_cond_instances_lost
</a>
</th>
<td>
</td>
<td>
</td>
<td>
</td>
<td>
Yes
</td>
<td>
Global
</td>
<td>
No
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="performance-schema-options.html#option_mysqld_performance-schema-consumer-events-stages-current">
performance-schema-consumer-events-stages-current
</a>
</th>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
</td>
<td>
</td>
<td>
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="performance-schema-options.html#option_mysqld_performance-schema-consumer-events-stages-history">
performance-schema-consumer-events-stages-history
</a>
</th>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
</td>
<td>
</td>
<td>
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="performance-schema-options.html#option_mysqld_performance-schema-consumer-events-stages-history-long">
performance-schema-consumer-events-stages-history-long
</a>
</th>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
</td>
<td>
</td>
<td>
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="performance-schema-options.html#option_mysqld_performance-schema-consumer-events-statements-cpu">
performance-schema-consumer-events-statements-cpu
</a>
</th>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
</td>
<td>
</td>
<td>
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="performance-schema-options.html#option_mysqld_performance-schema-consumer-events-statements-current">
performance-schema-consumer-events-statements-current
</a>
</th>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
</td>
<td>
</td>
<td>
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="performance-schema-options.html#option_mysqld_performance-schema-consumer-events-statements-history">
performance-schema-consumer-events-statements-history
</a>
</th>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
</td>
<td>
</td>
<td>
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="performance-schema-options.html#option_mysqld_performance-schema-consumer-events-statements-history-long">
performance-schema-consumer-events-statements-history-long
</a>
</th>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
</td>
<td>
</td>
<td>
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="performance-schema-options.html#option_mysqld_performance-schema-consumer-events-transactions-current">
performance-schema-consumer-events-transactions-current
</a>
</th>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
</td>
<td>
</td>
<td>
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="performance-schema-options.html#option_mysqld_performance-schema-consumer-events-transactions-history">
performance-schema-consumer-events-transactions-history
</a>
</th>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
</td>
<td>
</td>
<td>
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="performance-schema-options.html#option_mysqld_performance-schema-consumer-events-transactions-history-long">
performance-schema-consumer-events-transactions-history-long
</a>
</th>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
</td>
<td>
</td>
<td>
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="performance-schema-options.html#option_mysqld_performance-schema-consumer-events-waits-current">
performance-schema-consumer-events-waits-current
</a>
</th>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
</td>
<td>
</td>
<td>
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="performance-schema-options.html#option_mysqld_performance-schema-consumer-events-waits-history">
performance-schema-consumer-events-waits-history
</a>
</th>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
</td>
<td>
</td>
<td>
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="performance-schema-options.html#option_mysqld_performance-schema-consumer-events-waits-history-long">
performance-schema-consumer-events-waits-history-long
</a>
</th>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
</td>
<td>
</td>
<td>
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="performance-schema-options.html#option_mysqld_performance-schema-consumer-global-instrumentation">
performance-schema-consumer-global-instrumentation
</a>
</th>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
</td>
<td>
</td>
<td>
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="performance-schema-options.html#option_mysqld_performance-schema-consumer-statements-digest">
performance-schema-consumer-statements-digest
</a>
</th>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
</td>
<td>
</td>
<td>
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="performance-schema-options.html#option_mysqld_performance-schema-consumer-thread-instrumentation">
performance-schema-consumer-thread-instrumentation
</a>
</th>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
</td>
<td>
</td>
<td>
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="performance-schema-status-variables.html#statvar_Performance_schema_digest_lost">
Performance_schema_digest_lost
</a>
</th>
<td>
</td>
<td>
</td>
<td>
</td>
<td>
Yes
</td>
<td>
Global
</td>
<td>
No
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="performance-schema-system-variables.html#sysvar_performance_schema_digests_size">
performance_schema_digests_size
</a>
</th>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
</td>
<td>
Global
</td>
<td>
No
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="performance-schema-system-variables.html#sysvar_performance_schema_events_stages_history_long_size">
performance_schema_events_stages_history_long_size
</a>
</th>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
</td>
<td>
Global
</td>
<td>
No
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="performance-schema-system-variables.html#sysvar_performance_schema_events_stages_history_size">
performance_schema_events_stages_history_size
</a>
</th>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
</td>
<td>
Global
</td>
<td>
No
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="performance-schema-system-variables.html#sysvar_performance_schema_events_statements_history_long_size">
performance_schema_events_statements_history_long_size
</a>
</th>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
</td>
<td>
Global
</td>
<td>
No
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="performance-schema-system-variables.html#sysvar_performance_schema_events_statements_history_size">
performance_schema_events_statements_history_size
</a>
</th>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
</td>
<td>
Global
</td>
<td>
No
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="performance-schema-system-variables.html#sysvar_performance_schema_events_transactions_history_long_size">
performance_schema_events_transactions_history_long_size
</a>
</th>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
</td>
<td>
Global
</td>
<td>
No
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="performance-schema-system-variables.html#sysvar_performance_schema_events_transactions_history_size">
performance_schema_events_transactions_history_size
</a>
</th>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
</td>
<td>
Global
</td>
<td>
No
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="performance-schema-system-variables.html#sysvar_performance_schema_events_waits_history_long_size">
performance_schema_events_waits_history_long_size
</a>
</th>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
</td>
<td>
Global
</td>
<td>
No
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="performance-schema-system-variables.html#sysvar_performance_schema_events_waits_history_size">
performance_schema_events_waits_history_size
</a>
</th>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
</td>
<td>
Global
</td>
<td>
No
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="performance-schema-status-variables.html#statvar_Performance_schema_file_classes_lost">
Performance_schema_file_classes_lost
</a>
</th>
<td>
</td>
<td>
</td>
<td>
</td>
<td>
Yes
</td>
<td>
Global
</td>
<td>
No
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="performance-schema-status-variables.html#statvar_Performance_schema_file_handles_lost">
Performance_schema_file_handles_lost
</a>
</th>
<td>
</td>
<td>
</td>
<td>
</td>
<td>
Yes
</td>
<td>
Global
</td>
<td>
No
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="performance-schema-status-variables.html#statvar_Performance_schema_file_instances_lost">
Performance_schema_file_instances_lost
</a>
</th>
<td>
</td>
<td>
</td>
<td>
</td>
<td>
Yes
</td>
<td>
Global
</td>
<td>
No
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="performance-schema-status-variables.html#statvar_Performance_schema_hosts_lost">
Performance_schema_hosts_lost
</a>
</th>
<td>
</td>
<td>
</td>
<td>
</td>
<td>
Yes
</td>
<td>
Global
</td>
<td>
No
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="performance-schema-system-variables.html#sysvar_performance_schema_hosts_size">
performance_schema_hosts_size
</a>
</th>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
</td>
<td>
Global
</td>
<td>
No
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="performance-schema-options.html#option_mysqld_performance-schema-instrument">
performance-schema-instrument
</a>
</th>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
</td>
<td>
</td>
<td>
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="performance-schema-status-variables.html#statvar_Performance_schema_locker_lost">
Performance_schema_locker_lost
</a>
</th>
<td>
</td>
<td>
</td>
<td>
</td>
<td>
Yes
</td>
<td>
Global
</td>
<td>
No
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="performance-schema-system-variables.html#sysvar_performance_schema_max_cond_classes">
performance_schema_max_cond_classes
</a>
</th>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
</td>
<td>
Global
</td>
<td>
No
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="performance-schema-system-variables.html#sysvar_performance_schema_max_cond_instances">
performance_schema_max_cond_instances
</a>
</th>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
</td>
<td>
Global
</td>
<td>
No
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="performance-schema-system-variables.html#sysvar_performance_schema_max_digest_length">
performance_schema_max_digest_length
</a>
</th>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
</td>
<td>
Global
</td>
<td>
No
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="performance-schema-system-variables.html#sysvar_performance_schema_max_file_classes">
performance_schema_max_file_classes
</a>
</th>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
</td>
<td>
Global
</td>
<td>
No
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="performance-schema-system-variables.html#sysvar_performance_schema_max_file_handles">
performance_schema_max_file_handles
</a>
</th>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
</td>
<td>
Global
</td>
<td>
No
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="performance-schema-system-variables.html#sysvar_performance_schema_max_file_instances">
performance_schema_max_file_instances
</a>
</th>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
</td>
<td>
Global
</td>
<td>
No
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="performance-schema-system-variables.html#sysvar_performance_schema_max_memory_classes">
performance_schema_max_memory_classes
</a>
</th>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
</td>
<td>
Global
</td>
<td>
No
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="performance-schema-system-variables.html#sysvar_performance_schema_max_metadata_locks">
performance_schema_max_metadata_locks
</a>
</th>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
</td>
<td>
Global
</td>
<td>
No
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="performance-schema-system-variables.html#sysvar_performance_schema_max_meter_classes">
performance_schema_max_meter_classes
</a>
</th>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
</td>
<td>
Global
</td>
<td>
No
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="performance-schema-system-variables.html#sysvar_performance_schema_max_metric_classes">
performance_schema_max_metric_classes
</a>
</th>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
</td>
<td>
Global
</td>
<td>
No
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="performance-schema-system-variables.html#sysvar_performance_schema_max_mutex_classes">
performance_schema_max_mutex_classes
</a>
</th>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
</td>
<td>
Global
</td>
<td>
No
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="performance-schema-system-variables.html#sysvar_performance_schema_max_mutex_instances">
performance_schema_max_mutex_instances
</a>
</th>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
</td>
<td>
Global
</td>
<td>
No
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="performance-schema-system-variables.html#sysvar_performance_schema_max_prepared_statements_instances">
performance_schema_max_prepared_statements_instances
</a>
</th>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
</td>
<td>
Global
</td>
<td>
No
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="performance-schema-system-variables.html#sysvar_performance_schema_max_program_instances">
performance_schema_max_program_instances
</a>
</th>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
</td>
<td>
Global
</td>
<td>
No
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="performance-schema-system-variables.html#sysvar_performance_schema_max_rwlock_classes">
performance_schema_max_rwlock_classes
</a>
</th>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
</td>
<td>
Global
</td>
<td>
No
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="performance-schema-system-variables.html#sysvar_performance_schema_max_rwlock_instances">
performance_schema_max_rwlock_instances
</a>
</th>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
</td>
<td>
Global
</td>
<td>
No
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="performance-schema-system-variables.html#sysvar_performance_schema_max_socket_classes">
performance_schema_max_socket_classes
</a>
</th>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
</td>
<td>
Global
</td>
<td>
No
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="performance-schema-system-variables.html#sysvar_performance_schema_max_socket_instances">
performance_schema_max_socket_instances
</a>
</th>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
</td>
<td>
Global
</td>
<td>
No
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="performance-schema-system-variables.html#sysvar_performance_schema_max_stage_classes">
performance_schema_max_stage_classes
</a>
</th>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
</td>
<td>
Global
</td>
<td>
No
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="performance-schema-system-variables.html#sysvar_performance_schema_max_statement_classes">
performance_schema_max_statement_classes
</a>
</th>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
</td>
<td>
Global
</td>
<td>
No
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="performance-schema-system-variables.html#sysvar_performance_schema_max_statement_stack">
performance_schema_max_statement_stack
</a>
</th>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
</td>
<td>
Global
</td>
<td>
No
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="performance-schema-system-variables.html#sysvar_performance_schema_max_table_handles">
performance_schema_max_table_handles
</a>
</th>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
</td>
<td>
Global
</td>
<td>
No
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="performance-schema-system-variables.html#sysvar_performance_schema_max_table_instances">
performance_schema_max_table_instances
</a>
</th>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
</td>
<td>
Global
</td>
<td>
No
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="performance-schema-system-variables.html#sysvar_performance_schema_max_thread_classes">
performance_schema_max_thread_classes
</a>
</th>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
</td>
<td>
Global
</td>
<td>
No
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="performance-schema-system-variables.html#sysvar_performance_schema_max_thread_instances">
performance_schema_max_thread_instances
</a>
</th>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
</td>
<td>
Global
</td>
<td>
No
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="performance-schema-status-variables.html#statvar_Performance_schema_memory_classes_lost">
Performance_schema_memory_classes_lost
</a>
</th>
<td>
</td>
<td>
</td>
<td>
</td>
<td>
Yes
</td>
<td>
Global
</td>
<td>
No
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="performance-schema-status-variables.html#statvar_Performance_schema_metadata_lock_lost">
Performance_schema_metadata_lock_lost
</a>
</th>
<td>
</td>
<td>
</td>
<td>
</td>
<td>
Yes
</td>
<td>
Global
</td>
<td>
No
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="performance-schema-status-variables.html#statvar_Performance_schema_meter_lost">
Performance_schema_meter_lost
</a>
</th>
<td>
</td>
<td>
</td>
<td>
</td>
<td>
Yes
</td>
<td>
Global
</td>
<td>
No
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="performance-schema-status-variables.html#statvar_Performance_schema_metric_lost">
Performance_schema_metric_lost
</a>
</th>
<td>
</td>
<td>
</td>
<td>
</td>
<td>
Yes
</td>
<td>
Global
</td>
<td>
No
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="performance-schema-status-variables.html#statvar_Performance_schema_mutex_classes_lost">
Performance_schema_mutex_classes_lost
</a>
</th>
<td>
</td>
<td>
</td>
<td>
</td>
<td>
Yes
</td>
<td>
Global
</td>
<td>
No
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="performance-schema-status-variables.html#statvar_Performance_schema_mutex_instances_lost">
Performance_schema_mutex_instances_lost
</a>
</th>
<td>
</td>
<td>
</td>
<td>
</td>
<td>
Yes
</td>
<td>
Global
</td>
<td>
No
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="performance-schema-status-variables.html#statvar_Performance_schema_nested_statement_lost">
Performance_schema_nested_statement_lost
</a>
</th>
<td>
</td>
<td>
</td>
<td>
</td>
<td>
Yes
</td>
<td>
Global
</td>
<td>
No
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="performance-schema-status-variables.html#statvar_Performance_schema_prepared_statements_lost">
Performance_schema_prepared_statements_lost
</a>
</th>
<td>
</td>
<td>
</td>
<td>
</td>
<td>
Yes
</td>
<td>
Global
</td>
<td>
No
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="performance-schema-status-variables.html#statvar_Performance_schema_program_lost">
Performance_schema_program_lost
</a>
</th>
<td>
</td>
<td>
</td>
<td>
</td>
<td>
Yes
</td>
<td>
Global
</td>
<td>
No
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="performance-schema-status-variables.html#statvar_Performance_schema_rwlock_classes_lost">
Performance_schema_rwlock_classes_lost
</a>
</th>
<td>
</td>
<td>
</td>
<td>
</td>
<td>
Yes
</td>
<td>
Global
</td>
<td>
No
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="performance-schema-status-variables.html#statvar_Performance_schema_rwlock_instances_lost">
Performance_schema_rwlock_instances_lost
</a>
</th>
<td>
</td>
<td>
</td>
<td>
</td>
<td>
Yes
</td>
<td>
Global
</td>
<td>
No
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="performance-schema-status-variables.html#statvar_Performance_schema_session_connect_attrs_lost">
Performance_schema_session_connect_attrs_lost
</a>
</th>
<td>
</td>
<td>
</td>
<td>
</td>
<td>
Yes
</td>
<td>
Global
</td>
<td>
No
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="performance-schema-system-variables.html#sysvar_performance_schema_session_connect_attrs_size">
performance_schema_session_connect_attrs_size
</a>
</th>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
</td>
<td>
Global
</td>
<td>
No
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="performance-schema-system-variables.html#sysvar_performance_schema_setup_actors_size">
performance_schema_setup_actors_size
</a>
</th>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
</td>
<td>
Global
</td>
<td>
No
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="performance-schema-system-variables.html#sysvar_performance_schema_setup_objects_size">
performance_schema_setup_objects_size
</a>
</th>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
</td>
<td>
Global
</td>
<td>
No
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="performance-schema-status-variables.html#statvar_Performance_schema_socket_classes_lost">
Performance_schema_socket_classes_lost
</a>
</th>
<td>
</td>
<td>
</td>
<td>
</td>
<td>
Yes
</td>
<td>
Global
</td>
<td>
No
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="performance-schema-status-variables.html#statvar_Performance_schema_socket_instances_lost">
Performance_schema_socket_instances_lost
</a>
</th>
<td>
</td>
<td>
</td>
<td>
</td>
<td>
Yes
</td>
<td>
Global
</td>
<td>
No
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="performance-schema-status-variables.html#statvar_Performance_schema_stage_classes_lost">
Performance_schema_stage_classes_lost
</a>
</th>
<td>
</td>
<td>
</td>
<td>
</td>
<td>
Yes
</td>
<td>
Global
</td>
<td>
No
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="performance-schema-status-variables.html#statvar_Performance_schema_statement_classes_lost">
Performance_schema_statement_classes_lost
</a>
</th>
<td>
</td>
<td>
</td>
<td>
</td>
<td>
Yes
</td>
<td>
Global
</td>
<td>
No
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="performance-schema-status-variables.html#statvar_Performance_schema_table_handles_lost">
Performance_schema_table_handles_lost
</a>
</th>
<td>
</td>
<td>
</td>
<td>
</td>
<td>
Yes
</td>
<td>
Global
</td>
<td>
No
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="performance-schema-status-variables.html#statvar_Performance_schema_table_instances_lost">
Performance_schema_table_instances_lost
</a>
</th>
<td>
</td>
<td>
</td>
<td>
</td>
<td>
Yes
</td>
<td>
Global
</td>
<td>
No
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="performance-schema-status-variables.html#statvar_Performance_schema_thread_classes_lost">
Performance_schema_thread_classes_lost
</a>
</th>
<td>
</td>
<td>
</td>
<td>
</td>
<td>
Yes
</td>
<td>
Global
</td>
<td>
No
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="performance-schema-status-variables.html#statvar_Performance_schema_thread_instances_lost">
Performance_schema_thread_instances_lost
</a>
</th>
<td>
</td>
<td>
</td>
<td>
</td>
<td>
Yes
</td>
<td>
Global
</td>
<td>
No
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="performance-schema-status-variables.html#statvar_Performance_schema_users_lost">
Performance_schema_users_lost
</a>
</th>
<td>
</td>
<td>
</td>
<td>
</td>
<td>
Yes
</td>
<td>
Global
</td>
<td>
No
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="performance-schema-system-variables.html#sysvar_performance_schema_users_size">
performance_schema_users_size
</a>
</th>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
Yes
</td>
<td>
</td>
<td>
Global
</td>
<td>
No
</td>
</tr>
</tbody>
</table>
</div>
<div class="table-contents">
<table cellpadding="0" cellspacing="0" style="position: fixed; top: 0px; display: none; left: 401px; width: 763px;">
<thead>
<tr>
<th scope="col" style="width: 433.609px;">
Name
</th>
<th scope="col" style="width: 43.6875px;">
Cmd-Line
</th>
<th scope="col" style="width: 56.0938px;">
Option File
</th>
<th scope="col" style="width: 58.6406px;">
System Var
</th>
<th scope="col" style="width: 52.2812px;">
Status Var
</th>
<th scope="col" style="width: 48.4375px;">
Var Scope
</th>
<th scope="col" style="width: 69.2969px;">
Dynamic
</th>
</tr>
</thead>
</table>
</div>
</div>
<br class="table-break"/>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/sys-format-statement.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="sys-format-statement">
</a>
30.4.5.5 The format_statement() Function
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045060981456">
</a>
<a class="indexterm" name="idm46045060979984">
</a>
<p>
Given a string (normally representing an SQL statement),
reduces it to the length given by the
<code class="literal">
statement_truncate_len
</code>
configuration
option, and returns the result. No truncation occurs if the
string is shorter than
<code class="literal">
statement_truncate_len
</code>
. Otherwise, the
middle part of the string is replaced by an ellipsis
(
<code class="literal">
...
</code>
).
</p>
<p>
This function is useful for formatting possibly lengthy
statements retrieved from Performance Schema tables to a known
fixed maximum length.
</p>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h5 class="title">
<a name="sys-format-statement-parameters">
</a>
Parameters
</h5>
</div>
</div>
</div>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<code class="literal">
statement LONGTEXT
</code>
: The statement to
format.
</p>
</li>
</ul>
</div>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h5 class="title">
<a name="sys-format-statement-configuration-options">
</a>
Configuration Options
</h5>
</div>
</div>
</div>
<p>
<a class="link" href="sys-format-statement.html" title="30.4.5.5 The format_statement() Function">
<code class="literal">
format_statement()
</code>
</a>
operation
can be modified using the following configuration options or
their corresponding user-defined variables (see
<a class="xref" href="sys-sys-config.html" title="30.4.2.1 The sys_config Table">
Section 30.4.2.1, “The sys_config Table”
</a>
):
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<code class="literal">
statement_truncate_len
</code>
,
<code class="literal">
@sys.statement_truncate_len
</code>
</p>
<p>
The maximum length of statements returned by the
<a class="link" href="sys-format-statement.html" title="30.4.5.5 The format_statement() Function">
<code class="literal">
format_statement()
</code>
</a>
function. Longer statements are truncated to this
length. The default is 64.
</p>
</li>
</ul>
</div>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h5 class="title">
<a name="sys-format-statement-return-value">
</a>
Return Value
</h5>
</div>
</div>
</div>
<p>
A
<code class="literal">
LONGTEXT
</code>
value.
</p>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h5 class="title">
<a name="sys-format-statement-example">
</a>
Example
</h5>
</div>
</div>
</div>
<p>
By default,
<a class="link" href="sys-format-statement.html" title="30.4.5.5 The format_statement() Function">
<code class="literal">
format_statement()
</code>
</a>
truncates statements to be no more than 64 characters.
Setting
<code class="literal">
@sys.statement_truncate_len
</code>
changes the truncation length for the current session:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa97222247"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SET</span> <span class="token variable">@stmt</span> <span class="token operator">=</span> <span class="token string">'SELECT variable, value, set_time, set_by FROM sys_config'</span><span class="token punctuation">;</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> sys<span class="token punctuation">.</span>format_statement<span class="token punctuation">(</span><span class="token variable">@stmt</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> sys.format_statement(@stmt) <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> SELECT variable, value, set_time, set_by FROM sys_config <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token prompt">mysql></span> <span class="token keyword">SET</span> <span class="token variable">@sys.statement_truncate_len</span> <span class="token operator">=</span> <span class="token number">32</span><span class="token punctuation">;</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> sys<span class="token punctuation">.</span>format_statement<span class="token punctuation">(</span><span class="token variable">@stmt</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> sys.format_statement(@stmt) <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> SELECT variabl ... ROM sys_config <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
</div>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/performance-schema-lock-tables.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="performance-schema-lock-tables">
</a>
29.12.13 Performance Schema Lock Tables
</h3>
</div>
</div>
</div>
<div class="toc">
<dl class="toc">
<dt>
<span class="section">
<a href="performance-schema-data-locks-table.html">
29.12.13.1 The data_locks Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="performance-schema-data-lock-waits-table.html">
29.12.13.2 The data_lock_waits Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="performance-schema-metadata-locks-table.html">
29.12.13.3 The metadata_locks Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="performance-schema-table-handles-table.html">
29.12.13.4 The table_handles Table
</a>
</span>
</dt>
</dl>
</div>
<p>
The Performance Schema exposes lock information through these
tables:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<a class="link" href="performance-schema-data-locks-table.html" title="29.12.13.1 The data_locks Table">
<code class="literal">
data_locks
</code>
</a>
: Data locks held and
requested
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="performance-schema-data-lock-waits-table.html" title="29.12.13.2 The data_lock_waits Table">
<code class="literal">
data_lock_waits
</code>
</a>
: Relationships
between data lock owners and data lock requestors blocked by
those owners
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="performance-schema-metadata-locks-table.html" title="29.12.13.3 The metadata_locks Table">
<code class="literal">
metadata_locks
</code>
</a>
: Metadata locks
held and requested
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="performance-schema-table-handles-table.html" title="29.12.13.4 The table_handles Table">
<code class="literal">
table_handles
</code>
</a>
: Table locks held
and requested
</p>
</li>
</ul>
</div>
<p>
The following sections describe these tables in more detail.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/query-log.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="query-log">
</a>
7.4.3 The General Query Log
</h3>
</div>
</div>
</div>
<a class="indexterm" name="idm46045258419968">
</a>
<a class="indexterm" name="idm46045258418896">
</a>
<p>
The general query log is a general record of what
<a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
<span class="command">
<strong>
mysqld
</strong>
</span>
</a>
is doing. The server writes information
to this log when clients connect or disconnect, and it logs each
SQL statement received from clients. The general query log can be
very useful when you suspect an error in a client and want to know
exactly what the client sent to
<a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
<span class="command">
<strong>
mysqld
</strong>
</span>
</a>
.
</p>
<p>
Each line that shows when a client connects also includes
<code class="literal">
using
<em class="replaceable">
<code>
connection_type
</code>
</em>
</code>
to indicate
the protocol used to establish the connection.
<em class="replaceable">
<code>
connection_type
</code>
</em>
is one of
<code class="literal">
TCP/IP
</code>
(TCP/IP connection established without
SSL),
<code class="literal">
SSL/TLS
</code>
(TCP/IP connection established
with SSL),
<code class="literal">
Socket
</code>
(Unix socket file
connection),
<code class="literal">
Named Pipe
</code>
(Windows named pipe
connection), or
<code class="literal">
Shared Memory
</code>
(Windows shared
memory connection).
</p>
<p>
<a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
<span class="command">
<strong>
mysqld
</strong>
</span>
</a>
writes statements to the query log in
the order that it receives them, which might differ from the order
in which they are executed. This logging order is in contrast with
that of the binary log, for which statements are written after
they are executed but before any locks are released. In addition,
the query log may contain statements that only select data while
such statements are never written to the binary log.
</p>
<p>
When using statement-based binary logging on a replication source
server, statements received by its replicas are written to the
query log of each replica. Statements are written to the query log
of the source if a client reads events with the
<a class="link" href="mysqlbinlog.html" title="6.6.9 mysqlbinlog — Utility for Processing Binary Log Files">
<span class="command">
<strong>
mysqlbinlog
</strong>
</span>
</a>
utility and passes them to the
server.
</p>
<p>
However, when using row-based binary logging, updates are sent as
row changes rather than SQL statements, and thus these statements
are never written to the query log when
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_format">
<code class="literal">
binlog_format
</code>
</a>
is
<code class="literal">
ROW
</code>
. A given update also might not be written
to the query log when this variable is set to
<code class="literal">
MIXED
</code>
, depending on the statement used. See
<a class="xref" href="replication-sbr-rbr.html" title="19.2.1.1 Advantages and Disadvantages of Statement-Based and Row-Based Replication">
Section 19.2.1.1, “Advantages and Disadvantages of Statement-Based and Row-Based
Replication”
</a>
, for more information.
</p>
<p>
By default, the general query log is disabled. To specify the
initial general query log state explicitly, use
<a class="link" href="server-system-variables.html#sysvar_general_log">
<code class="option">
--general_log[={0|1}]
</code>
</a>
. With no
argument or an argument of 1,
<a class="link" href="server-system-variables.html#sysvar_general_log">
<code class="option">
--general_log
</code>
</a>
enables the log. With
an argument of 0, this option disables the log. To specify a log
file name, use
<a class="link" href="server-system-variables.html#sysvar_general_log_file">
<code class="option">
--general_log_file=
<em class="replaceable">
<code>
file_name
</code>
</em>
</code>
</a>
.
To specify the log destination, use the
<a class="link" href="server-system-variables.html#sysvar_log_output">
<code class="literal">
log_output
</code>
</a>
system variable (as
described in
<a class="xref" href="log-destinations.html" title="7.4.1 Selecting General Query Log and Slow Query Log Output Destinations">
Section 7.4.1, “Selecting General Query Log and Slow Query Log Output Destinations”
</a>
).
</p>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
If you specify the
<code class="literal">
TABLE
</code>
log destination, see
<a class="xref" href="log-destinations.html#log-destinations-tables-open-files" title="Log Tables and “Too many open files” Errors">
Log Tables and
<span class="quote">
“
<span class="quote">
Too many open files
</span>
”
</span>
Errors
</a>
.
</p>
</div>
<p>
If you specify no name for the general query log file, the default
name is
<code class="filename">
<em class="replaceable">
<code>
host_name
</code>
</em>
.log
</code>
. The
server creates the file in the data directory unless an absolute
path name is given to specify a different directory.
</p>
<p>
To disable or enable the general query log or change the log file
name at runtime, use the global
<a class="link" href="server-system-variables.html#sysvar_general_log">
<code class="literal">
general_log
</code>
</a>
and
<a class="link" href="server-system-variables.html#sysvar_general_log_file">
<code class="literal">
general_log_file
</code>
</a>
system
variables. Set
<a class="link" href="server-system-variables.html#sysvar_general_log">
<code class="literal">
general_log
</code>
</a>
to 0
(or
<code class="literal">
OFF
</code>
) to disable the log or to 1 (or
<code class="literal">
ON
</code>
) to enable it. Set
<a class="link" href="server-system-variables.html#sysvar_general_log_file">
<code class="literal">
general_log_file
</code>
</a>
to specify the
name of the log file. If a log file already is open, it is closed
and the new file is opened.
</p>
<p>
When the general query log is enabled, the server writes output to
any destinations specified by the
<a class="link" href="server-system-variables.html#sysvar_log_output">
<code class="literal">
log_output
</code>
</a>
system variable. If
you enable the log, the server opens the log file and writes
startup messages to it. However, further logging of queries to the
file does not occur unless the
<code class="literal">
FILE
</code>
log
destination is selected. If the destination is
<code class="literal">
NONE
</code>
, the server writes no queries even if the
general log is enabled. Setting the log file name has no effect on
logging if the log destination value does not contain
<code class="literal">
FILE
</code>
.
</p>
<p>
Server restarts and log flushing do not cause a new general query
log file to be generated (although flushing closes and reopens
it). To rename the file and create a new one, use the following
commands:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-terminal"><div class="docs-select-all right" id="sa62949868"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-terminal"><span class="token prompt">$> </span><span class="token command">mv</span> <em class="replaceable">host_name</em><span class="token punctuation">.</span>log <em class="replaceable">host_name</em>-old<span class="token punctuation">.</span>log
<span class="token prompt">$> </span><span class="token command">mysqladmin</span> flush-logs general
<span class="token prompt">$> </span><span class="token command">mv</span> <em class="replaceable">host_name</em>-old<span class="token punctuation">.</span>log <em class="replaceable">backup-directory</em></code></pre>
</div>
<p>
On Windows, use
<span class="command">
<strong>
rename
</strong>
</span>
rather than
<span class="command">
<strong>
mv
</strong>
</span>
.
</p>
<p>
You can also rename the general query log file at runtime by
disabling the log:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa26413783"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SET</span> <span class="token keyword">GLOBAL</span> general_log <span class="token operator">=</span> <span class="token string">'OFF'</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
With the log disabled, rename the log file externally (for
example, from the command line). Then enable the log again:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa92307903"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SET</span> <span class="token keyword">GLOBAL</span> general_log <span class="token operator">=</span> <span class="token string">'ON'</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
This method works on any platform and does not require a server
restart.
</p>
<p>
To disable or enable general query logging for the current
session, set the session
<a class="link" href="server-system-variables.html#sysvar_sql_log_off">
<code class="literal">
sql_log_off
</code>
</a>
variable to
<code class="literal">
ON
</code>
or
<code class="literal">
OFF
</code>
. (This assumes
that the general query log itself is enabled.)
</p>
<p>
Passwords in statements written to the general query log are
rewritten by the server not to occur literally in plain text.
Password rewriting can be suppressed for the general query log by
starting the server with the
<a class="link" href="server-options.html#option_mysqld_log-raw">
<code class="option">
--log-raw
</code>
</a>
option. This option may
be useful for diagnostic purposes, to see the exact text of
statements as received by the server, but for security reasons is
not recommended for production use. See also
<a class="xref" href="password-logging.html" title="8.1.2.3 Passwords and Logging">
Section 8.1.2.3, “Passwords and Logging”
</a>
.
</p>
<p>
An implication of password rewriting is that statements that
cannot be parsed (due, for example, to syntax errors) are not
written to the general query log because they cannot be known to
be password free. Use cases that require logging of all statements
including those with errors should use the
<a class="link" href="server-options.html#option_mysqld_log-raw">
<code class="option">
--log-raw
</code>
</a>
option, bearing in mind
that this also bypasses password rewriting.
</p>
<p>
Password rewriting occurs only when plain text passwords are
expected. For statements with syntax that expect a password hash
value, no rewriting occurs. If a plain text password is supplied
erroneously for such syntax, the password is logged as given,
without rewriting.
</p>
<p>
The
<a class="link" href="server-system-variables.html#sysvar_log_timestamps">
<code class="literal">
log_timestamps
</code>
</a>
system
variable controls the time zone of timestamps in messages written
to the general query log file (as well as to the slow query log
file and the error log). It does not affect the time zone of
general query log and slow query log messages written to log
tables, but rows retrieved from those tables can be converted from
the local system time zone to any desired time zone with
<a class="link" href="date-and-time-functions.html#function_convert-tz">
<code class="literal">
CONVERT_TZ()
</code>
</a>
or by setting the
session
<a class="link" href="server-system-variables.html#sysvar_time_zone">
<code class="literal">
time_zone
</code>
</a>
system
variable.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/partitioning-types.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h2 class="title">
<a name="partitioning-types">
</a>
26.2 Partitioning Types
</h2>
</div>
</div>
</div>
<div class="toc">
<dl class="toc">
<dt>
<span class="section">
<a href="partitioning-range.html">
26.2.1 RANGE Partitioning
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="partitioning-list.html">
26.2.2 LIST Partitioning
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="partitioning-columns.html">
26.2.3 COLUMNS Partitioning
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="partitioning-hash.html">
26.2.4 HASH Partitioning
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="partitioning-key.html">
26.2.5 KEY Partitioning
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="partitioning-subpartitions.html">
26.2.6 Subpartitioning
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="partitioning-handling-nulls.html">
26.2.7 How MySQL Partitioning Handles NULL
</a>
</span>
</dt>
</dl>
</div>
<a class="indexterm" name="idm46045084868544">
</a>
<p>
This section discusses the types of partitioning which are
available in MySQL 8.4. These include the types
listed here:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<b>
RANGE partitioning.
</b>
This type of partitioning assigns rows to partitions based
on column values falling within a given range. See
<a class="xref" href="partitioning-range.html" title="26.2.1 RANGE Partitioning">
Section 26.2.1, “RANGE Partitioning”
</a>
. For information about
an extension to this type,
<code class="literal">
RANGE COLUMNS
</code>
,
see
<a class="xref" href="partitioning-columns-range.html" title="26.2.3.1 RANGE COLUMNS partitioning">
Section 26.2.3.1, “RANGE COLUMNS partitioning”
</a>
.
</p>
</li>
<li class="listitem">
<p>
<b>
LIST partitioning.
</b>
Similar to partitioning by
<code class="literal">
RANGE
</code>
, except
that the partition is selected based on columns matching one
of a set of discrete values. See
<a class="xref" href="partitioning-list.html" title="26.2.2 LIST Partitioning">
Section 26.2.2, “LIST Partitioning”
</a>
. For information about
an extension to this type,
<code class="literal">
LIST COLUMNS
</code>
,
see
<a class="xref" href="partitioning-columns-list.html" title="26.2.3.2 LIST COLUMNS partitioning">
Section 26.2.3.2, “LIST COLUMNS partitioning”
</a>
.
</p>
</li>
<li class="listitem">
<p>
<b>
HASH partitioning.
</b>
With this type of partitioning, a partition is selected
based on the value returned by a user-defined expression
that operates on column values in rows to be inserted into
the table. The function may consist of any expression valid
in MySQL that yields an integer value. See
<a class="xref" href="partitioning-hash.html" title="26.2.4 HASH Partitioning">
Section 26.2.4, “HASH Partitioning”
</a>
.
</p>
<p>
An extension to this type,
<code class="literal">
LINEAR HASH
</code>
, is
also available, see
<a class="xref" href="partitioning-linear-hash.html" title="26.2.4.1 LINEAR HASH Partitioning">
Section 26.2.4.1, “LINEAR HASH Partitioning”
</a>
.
</p>
</li>
<li class="listitem">
<p>
<b>
KEY partitioning.
</b>
This type of partitioning is similar to partitioning by
<code class="literal">
HASH
</code>
, except that only one or more
columns to be evaluated are supplied, and the MySQL server
provides its own hashing function. These columns can contain
other than integer values, since the hashing function
supplied by MySQL guarantees an integer result regardless of
the column data type. An extension to this type,
<code class="literal">
LINEAR KEY
</code>
, is also available. See
<a class="xref" href="partitioning-key.html" title="26.2.5 KEY Partitioning">
Section 26.2.5, “KEY Partitioning”
</a>
.
</p>
</li>
</ul>
</div>
<a class="indexterm" name="idm46045084848752">
</a>
<a class="indexterm" name="idm46045084847264">
</a>
<p>
A very common use of database partitioning is to segregate data by
date. Some database systems support explicit date partitioning,
which MySQL does not implement in 8.4. However, it is
not difficult in MySQL to create partitioning schemes based on
<a class="link" href="datetime.html" title="13.2.2 The DATE, DATETIME, and TIMESTAMP Types">
<code class="literal">
DATE
</code>
</a>
,
<a class="link" href="time.html" title="13.2.3 The TIME Type">
<code class="literal">
TIME
</code>
</a>
, or
<a class="link" href="datetime.html" title="13.2.2 The DATE, DATETIME, and TIMESTAMP Types">
<code class="literal">
DATETIME
</code>
</a>
columns, or based on
expressions making use of such columns.
</p>
<p>
When partitioning by
<code class="literal">
KEY
</code>
or
<code class="literal">
LINEAR
KEY
</code>
, you can use a
<a class="link" href="datetime.html" title="13.2.2 The DATE, DATETIME, and TIMESTAMP Types">
<code class="literal">
DATE
</code>
</a>
,
<a class="link" href="time.html" title="13.2.3 The TIME Type">
<code class="literal">
TIME
</code>
</a>
, or
<a class="link" href="datetime.html" title="13.2.2 The DATE, DATETIME, and TIMESTAMP Types">
<code class="literal">
DATETIME
</code>
</a>
column as the partitioning
column without performing any modification of the column value.
For example, this table creation statement is perfectly valid in
MySQL:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa53486086"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">TABLE</span> members <span class="token punctuation">(</span>
firstname <span class="token datatype">VARCHAR</span><span class="token punctuation">(</span><span class="token number">25</span><span class="token punctuation">)</span> <span class="token operator">NOT</span> <span class="token boolean">NULL</span><span class="token punctuation">,</span>
lastname <span class="token datatype">VARCHAR</span><span class="token punctuation">(</span><span class="token number">25</span><span class="token punctuation">)</span> <span class="token operator">NOT</span> <span class="token boolean">NULL</span><span class="token punctuation">,</span>
username <span class="token datatype">VARCHAR</span><span class="token punctuation">(</span><span class="token number">16</span><span class="token punctuation">)</span> <span class="token operator">NOT</span> <span class="token boolean">NULL</span><span class="token punctuation">,</span>
email <span class="token datatype">VARCHAR</span><span class="token punctuation">(</span><span class="token number">35</span><span class="token punctuation">)</span><span class="token punctuation">,</span>
joined <span class="token datatype">DATE</span> <span class="token operator">NOT</span> <span class="token boolean">NULL</span>
<span class="token punctuation">)</span>
<span class="token keyword">PARTITION</span> <span class="token keyword">BY</span> <span class="token keyword">KEY</span><span class="token punctuation">(</span>joined<span class="token punctuation">)</span>
<span class="token keyword">PARTITIONS</span> <span class="token number">6</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
In MySQL 8.4, it is also possible to use a
<a class="link" href="datetime.html" title="13.2.2 The DATE, DATETIME, and TIMESTAMP Types">
<code class="literal">
DATE
</code>
</a>
or
<a class="link" href="datetime.html" title="13.2.2 The DATE, DATETIME, and TIMESTAMP Types">
<code class="literal">
DATETIME
</code>
</a>
column as the partitioning
column using
<code class="literal">
RANGE COLUMNS
</code>
and
<code class="literal">
LIST
COLUMNS
</code>
partitioning.
</p>
<p>
Other partitioning types require a partitioning expression that
yields an integer value or
<code class="literal">
NULL
</code>
. If you wish to
use date-based partitioning by
<code class="literal">
RANGE
</code>
,
<code class="literal">
LIST
</code>
,
<code class="literal">
HASH
</code>
, or
<code class="literal">
LINEAR HASH
</code>
, you can simply employ a function
that operates on a
<a class="link" href="datetime.html" title="13.2.2 The DATE, DATETIME, and TIMESTAMP Types">
<code class="literal">
DATE
</code>
</a>
,
<a class="link" href="time.html" title="13.2.3 The TIME Type">
<code class="literal">
TIME
</code>
</a>
, or
<a class="link" href="datetime.html" title="13.2.2 The DATE, DATETIME, and TIMESTAMP Types">
<code class="literal">
DATETIME
</code>
</a>
column and returns such a
value, as shown here:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa4048087"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">TABLE</span> members <span class="token punctuation">(</span>
firstname <span class="token datatype">VARCHAR</span><span class="token punctuation">(</span><span class="token number">25</span><span class="token punctuation">)</span> <span class="token operator">NOT</span> <span class="token boolean">NULL</span><span class="token punctuation">,</span>
lastname <span class="token datatype">VARCHAR</span><span class="token punctuation">(</span><span class="token number">25</span><span class="token punctuation">)</span> <span class="token operator">NOT</span> <span class="token boolean">NULL</span><span class="token punctuation">,</span>
username <span class="token datatype">VARCHAR</span><span class="token punctuation">(</span><span class="token number">16</span><span class="token punctuation">)</span> <span class="token operator">NOT</span> <span class="token boolean">NULL</span><span class="token punctuation">,</span>
email <span class="token datatype">VARCHAR</span><span class="token punctuation">(</span><span class="token number">35</span><span class="token punctuation">)</span><span class="token punctuation">,</span>
joined <span class="token datatype">DATE</span> <span class="token operator">NOT</span> <span class="token boolean">NULL</span>
<span class="token punctuation">)</span>
<span class="token keyword">PARTITION</span> <span class="token keyword">BY</span> <span class="token keyword">RANGE</span><span class="token punctuation">(</span> <span class="token function">YEAR</span><span class="token punctuation">(</span>joined<span class="token punctuation">)</span> <span class="token punctuation">)</span> <span class="token punctuation">(</span>
<span class="token keyword">PARTITION</span> p0 <span class="token keyword">VALUES</span> <span class="token keyword">LESS</span> <span class="token keyword">THAN</span> <span class="token punctuation">(</span><span class="token number">1960</span><span class="token punctuation">)</span><span class="token punctuation">,</span>
<span class="token keyword">PARTITION</span> p1 <span class="token keyword">VALUES</span> <span class="token keyword">LESS</span> <span class="token keyword">THAN</span> <span class="token punctuation">(</span><span class="token number">1970</span><span class="token punctuation">)</span><span class="token punctuation">,</span>
<span class="token keyword">PARTITION</span> p2 <span class="token keyword">VALUES</span> <span class="token keyword">LESS</span> <span class="token keyword">THAN</span> <span class="token punctuation">(</span><span class="token number">1980</span><span class="token punctuation">)</span><span class="token punctuation">,</span>
<span class="token keyword">PARTITION</span> p3 <span class="token keyword">VALUES</span> <span class="token keyword">LESS</span> <span class="token keyword">THAN</span> <span class="token punctuation">(</span><span class="token number">1990</span><span class="token punctuation">)</span><span class="token punctuation">,</span>
<span class="token keyword">PARTITION</span> p4 <span class="token keyword">VALUES</span> <span class="token keyword">LESS</span> <span class="token keyword">THAN</span> <span class="token keyword">MAXVALUE</span>
<span class="token punctuation">)</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
Additional examples of partitioning using dates may be found in
the following sections of this chapter:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<a class="xref" href="partitioning-range.html" title="26.2.1 RANGE Partitioning">
Section 26.2.1, “RANGE Partitioning”
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="partitioning-hash.html" title="26.2.4 HASH Partitioning">
Section 26.2.4, “HASH Partitioning”
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="partitioning-linear-hash.html" title="26.2.4.1 LINEAR HASH Partitioning">
Section 26.2.4.1, “LINEAR HASH Partitioning”
</a>
</p>
</li>
</ul>
</div>
<p>
For more complex examples of date-based partitioning, see the
following sections:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<a class="xref" href="partitioning-pruning.html" title="26.4 Partition Pruning">
Section 26.4, “Partition Pruning”
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="partitioning-subpartitions.html" title="26.2.6 Subpartitioning">
Section 26.2.6, “Subpartitioning”
</a>
</p>
</li>
</ul>
</div>
<p>
MySQL partitioning is optimized for use with the
<a class="link" href="date-and-time-functions.html#function_to-days">
<code class="literal">
TO_DAYS()
</code>
</a>
,
<a class="link" href="date-and-time-functions.html#function_year">
<code class="literal">
YEAR()
</code>
</a>
, and
<a class="link" href="date-and-time-functions.html#function_to-seconds">
<code class="literal">
TO_SECONDS()
</code>
</a>
functions. However,
you can use other date and time functions that return an integer
or
<code class="literal">
NULL
</code>
, such as
<a class="link" href="date-and-time-functions.html#function_weekday">
<code class="literal">
WEEKDAY()
</code>
</a>
,
<a class="link" href="date-and-time-functions.html#function_dayofyear">
<code class="literal">
DAYOFYEAR()
</code>
</a>
, or
<a class="link" href="date-and-time-functions.html#function_month">
<code class="literal">
MONTH()
</code>
</a>
. See
<a class="xref" href="date-and-time-functions.html" title="14.7 Date and Time Functions">
Section 14.7, “Date and Time Functions”
</a>
, for more information
about such functions.
</p>
<p>
It is important to remember—regardless of the type of
partitioning that you use—that partitions are always
numbered automatically and in sequence when created, starting with
<code class="literal">
0
</code>
. When a new row is inserted into a
partitioned table, it is these partition numbers that are used in
identifying the correct partition. For example, if your table uses
4 partitions, these partitions are numbered
<code class="literal">
0
</code>
,
<code class="literal">
1
</code>
,
<code class="literal">
2
</code>
, and
<code class="literal">
3
</code>
. For the
<code class="literal">
RANGE
</code>
and
<code class="literal">
LIST
</code>
partitioning types, it is necessary to
ensure that there is a partition defined for each partition
number. For
<code class="literal">
HASH
</code>
partitioning, the
user-supplied expression must evaluate to an integer value. For
<code class="literal">
KEY
</code>
partitioning, this issue is taken care of
automatically by the hashing function which the MySQL server
employs internally.
</p>
<p>
Names of partitions generally follow the rules governing other
MySQL identifiers, such as those for tables and databases.
However, you should note that partition names are not
case-sensitive. For example, the following
<a class="link" href="create-table.html" title="15.1.20 CREATE TABLE Statement">
<code class="literal">
CREATE TABLE
</code>
</a>
statement fails as
shown:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa3271456"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">CREATE</span> <span class="token keyword">TABLE</span> t2 <span class="token punctuation">(</span>val <span class="token datatype">INT</span><span class="token punctuation">)</span>
<span class="token prompt"> -></span> <span class="token keyword">PARTITION</span> <span class="token keyword">BY</span> <span class="token keyword">LIST</span><span class="token punctuation">(</span>val<span class="token punctuation">)</span><span class="token punctuation">(</span>
<span class="token prompt"> -></span> <span class="token keyword">PARTITION</span> mypart <span class="token keyword">VALUES</span> <span class="token keyword">IN</span> <span class="token punctuation">(</span><span class="token number">1</span><span class="token punctuation">,</span><span class="token number">3</span><span class="token punctuation">,</span><span class="token number">5</span><span class="token punctuation">)</span><span class="token punctuation">,</span>
<span class="token prompt"> -></span> <span class="token keyword">PARTITION</span> MyPart <span class="token keyword">VALUES</span> <span class="token keyword">IN</span> <span class="token punctuation">(</span><span class="token number">2</span><span class="token punctuation">,</span><span class="token number">4</span><span class="token punctuation">,</span><span class="token number">6</span><span class="token punctuation">)</span>
<span class="token prompt"> -></span> <span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output">ERROR 1488 (HY000)<span class="token punctuation">:</span> Duplicate partition name mypart</span></code></pre>
</div>
<p>
Failure occurs because MySQL sees no difference between the
partition names
<code class="literal">
mypart
</code>
and
<code class="literal">
MyPart
</code>
.
</p>
<p>
When you specify the number of partitions for the table, this must
be expressed as a positive, nonzero integer literal with no
leading zeros, and may not be an expression such as
<code class="literal">
0.8E+01
</code>
or
<code class="literal">
6-2
</code>
, even if it
evaluates to an integer value. Decimal fractions are not
permitted.
</p>
<p>
In the sections that follow, we do not necessarily provide all
possible forms for the syntax that can be used for creating each
partition type; for this information, see
<a class="xref" href="create-table.html" title="15.1.20 CREATE TABLE Statement">
Section 15.1.20, “CREATE TABLE Statement”
</a>
.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/group-replication-functions-for-new-primary.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="group-replication-functions-for-new-primary">
</a>
14.18.1.1 Function which Configures Group Replication Primary
</h4>
</div>
</div>
</div>
<p>
The following function enables you to set a member of a
single-primary replication group to take over as the primary.
The current primary becomes a read-only secondary, and the
specified group member becomes the read-write primary. The
function can be used on any member of a replication group
running in single-primary mode. This function replaces the
usual primary election process; see
<a class="xref" href="group-replication-change-primary.html" title="20.5.1.1 Changing the Primary">
Section 20.5.1.1, “Changing the Primary”
</a>
, for more
information.
</p>
<p>
If a standard source to replica replication channel is running
on the existing primary member in addition to the Group
Replication channels, you must stop that replication channel
before you can change the primary member. You can identify the
current primary using the
<code class="literal">
MEMBER_ROLE
</code>
column in the Performance Schema
<a class="link" href="performance-schema-replication-group-members-table.html" title="29.12.11.16 The replication_group_members Table">
<code class="literal">
replication_group_members
</code>
</a>
table.
</p>
<p>
Any uncommitted transactions that the group is waiting on must
be committed, rolled back, or terminated before the operation
can complete. You can specify a timeout for transactions that
are running when you use the function. For the timeout to
work, all members of the group must be MySQL version 8.0.29 or
newer.
</p>
<p>
When the timeout expires, for any transactions that did not
yet reach their commit phase, the client session is
disconnected so that the transaction does not proceed.
Transactions that reached their commit phase are allowed to
complete. When you set a timeout, it also prevents new
transactions starting on the primary from that point on.
Explicitly defined transactions (with a
<code class="literal">
START
TRANSACTION
</code>
or
<code class="literal">
BEGIN
</code>
statement)
are subject to the timeout, disconnection, and incoming
transaction blocking even if they do not modify any data. To
allow inspection of the primary while the function is
operating, single statements that do not modify data, as
listed in
<a class="xref" href="group-replication-configuring-consistency-guarantees.html#group-replication-nonblocking" title="Permitted Queries Under Consistency Rules">
Permitted Queries Under Consistency Rules
</a>
, are
permitted to proceed.
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<a name="function_group-replication-set-as-primary">
</a>
<a class="link" href="group-replication-functions-for-new-primary.html#function_group-replication-set-as-primary">
<code class="literal">
group_replication_set_as_primary()
</code>
</a>
</p>
<a class="indexterm" name="idm46045193977344">
</a>
<a class="indexterm" name="idm46045193976304">
</a>
<p>
Appoints a specific member of the group as the new
primary, overriding any election process.
</p>
<p>
Syntax:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-clike"><div class="docs-select-all right" id="sa51465159"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-clike">STRING <span class="token function">group_replication_set_as_primary</span><span class="token punctuation">(</span><em class="replaceable">member_uuid</em><span class="token punctuation">[</span><span class="token punctuation">,</span> <em class="replaceable">timeout</em><span class="token punctuation">]</span><span class="token punctuation">)</span></code></pre>
</div>
<p>
Arguments:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
<em class="replaceable">
<code>
member_uuid
</code>
</em>
: A string
containing the UUID of the member of the group that
you want to become the new primary.
</p>
</li>
<li class="listitem">
<p>
<em class="replaceable">
<code>
timeout
</code>
</em>
: An integer
specifying a timeout in seconds for transactions that
are running on the existing primary when you use the
function. You can set a timeout from 0 seconds
(immediately) up to 3600 seconds (60 minutes). When
you set a timeout, new transactions cannot start on
the primary from that point on. There is no default
setting for the timeout, so if you do not set it,
there is no upper limit to the wait time, and new
transactions can start during that time.
</p>
</li>
</ul>
</div>
<p>
Return value:
</p>
<p>
A string containing the result of the operation, for
example whether it was successful or not.
</p>
<p>
Example:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa35238076"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SELECT</span> group_replication_set_as_primary<span class="token punctuation">(</span>‘<span class="token number">00371d66</span><span class="token operator">-</span><span class="token number">3c45</span><span class="token operator">-</span><span class="token number">11ea</span><span class="token operator">-</span><span class="token number">804b</span><span class="token operator">-</span><span class="token number">080027337932</span>’<span class="token punctuation">,</span> <span class="token number">300</span><span class="token punctuation">)</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
This function waits for all ongoing transactions and DML
operations to finish before electing the new primary. In
MySQL 8.4, it also waits for the completion
of any ongoing DDL statements such as
<a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement">
<code class="literal">
ALTER TABLE
</code>
</a>
. Operations
that are considered DDL statements for this purpose are
listed here:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
<a class="link" href="alter-database.html" title="15.1.2 ALTER DATABASE Statement">
<code class="literal">
ALTER DATABASE
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="alter-function.html" title="15.1.4 ALTER FUNCTION Statement">
<code class="literal">
ALTER FUNCTION
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="alter-instance.html" title="15.1.5 ALTER INSTANCE Statement">
<code class="literal">
ALTER INSTANCE
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="alter-procedure.html" title="15.1.7 ALTER PROCEDURE Statement">
<code class="literal">
ALTER PROCEDURE
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="alter-server.html" title="15.1.8 ALTER SERVER Statement">
<code class="literal">
ALTER SERVER
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
ALTER TABLE
</code>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="alter-tablespace.html" title="15.1.10 ALTER TABLESPACE Statement">
<code class="literal">
ALTER TABLESPACE
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="alter-user.html" title="15.7.1.1 ALTER USER Statement">
<code class="literal">
ALTER USER
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="alter-view.html" title="15.1.11 ALTER VIEW Statement">
<code class="literal">
ALTER VIEW
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="analyze-table.html" title="15.7.3.1 ANALYZE TABLE Statement">
<code class="literal">
ANALYZE TABLE
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="cache-index.html" title="15.7.8.2 CACHE INDEX Statement">
<code class="literal">
CACHE INDEX
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="check-table.html" title="15.7.3.2 CHECK TABLE Statement">
<code class="literal">
CHECK TABLE
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="create-database.html" title="15.1.12 CREATE DATABASE Statement">
<code class="literal">
CREATE DATABASE
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="create-function.html" title="15.1.14 CREATE FUNCTION Statement">
<code class="literal">
CREATE FUNCTION
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="create-index.html" title="15.1.15 CREATE INDEX Statement">
<code class="literal">
CREATE INDEX
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="create-role.html" title="15.7.1.2 CREATE ROLE Statement">
<code class="literal">
CREATE ROLE
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="create-procedure.html" title="15.1.17 CREATE PROCEDURE and CREATE FUNCTION Statements">
<code class="literal">
CREATE PROCEDURE
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="create-server.html" title="15.1.18 CREATE SERVER Statement">
<code class="literal">
CREATE SERVER
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="create-spatial-reference-system.html" title="15.1.19 CREATE SPATIAL REFERENCE SYSTEM Statement">
<code class="literal">
CREATE SPATIAL REFERENCE
SYSTEM
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="create-table.html" title="15.1.20 CREATE TABLE Statement">
<code class="literal">
CREATE TABLE
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="create-tablespace.html" title="15.1.21 CREATE TABLESPACE Statement">
<code class="literal">
CREATE TABLESPACE
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="create-trigger.html" title="15.1.22 CREATE TRIGGER Statement">
<code class="literal">
CREATE TRIGGER
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="create-user.html" title="15.7.1.3 CREATE USER Statement">
<code class="literal">
CREATE USER
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="create-view.html" title="15.1.23 CREATE VIEW Statement">
<code class="literal">
CREATE VIEW
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="drop-database.html" title="15.1.24 DROP DATABASE Statement">
<code class="literal">
DROP DATABASE
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="drop-function.html" title="15.1.26 DROP FUNCTION Statement">
<code class="literal">
DROP FUNCTION
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="drop-index.html" title="15.1.27 DROP INDEX Statement">
<code class="literal">
DROP INDEX
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="drop-procedure.html" title="15.1.29 DROP PROCEDURE and DROP FUNCTION Statements">
<code class="literal">
DROP PROCEDURE
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="drop-role.html" title="15.7.1.4 DROP ROLE Statement">
<code class="literal">
DROP ROLE
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="drop-server.html" title="15.1.30 DROP SERVER Statement">
<code class="literal">
DROP SERVER
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="drop-spatial-reference-system.html" title="15.1.31 DROP SPATIAL REFERENCE SYSTEM Statement">
<code class="literal">
DROP SPATIAL REFERENCE
SYSTEM
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="drop-table.html" title="15.1.32 DROP TABLE Statement">
<code class="literal">
DROP TABLE
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="drop-tablespace.html" title="15.1.33 DROP TABLESPACE Statement">
<code class="literal">
DROP TABLESPACE
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="drop-trigger.html" title="15.1.34 DROP TRIGGER Statement">
<code class="literal">
DROP TRIGGER
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="drop-user.html" title="15.7.1.5 DROP USER Statement">
<code class="literal">
DROP USER
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="drop-view.html" title="15.1.35 DROP VIEW Statement">
<code class="literal">
DROP VIEW
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="grant.html" title="15.7.1.6 GRANT Statement">
<code class="literal">
GRANT
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="load-index.html" title="15.7.8.5 LOAD INDEX INTO CACHE Statement">
<code class="literal">
LOAD INDEX
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="optimize-table.html" title="15.7.3.4 OPTIMIZE TABLE Statement">
<code class="literal">
OPTIMIZE TABLE
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="rename-table.html" title="15.1.36 RENAME TABLE Statement">
<code class="literal">
RENAME TABLE
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="repair-table.html" title="15.7.3.5 REPAIR TABLE Statement">
<code class="literal">
REPAIR TABLE
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="revoke.html" title="15.7.1.8 REVOKE Statement">
<code class="literal">
REVOKE
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="truncate-table.html" title="15.1.37 TRUNCATE TABLE Statement">
<code class="literal">
TRUNCATE TABLE
</code>
</a>
</p>
</li>
</ul>
</div>
<p>
This also includes any open cursors (see
<a class="xref" href="cursors.html" title="15.6.6 Cursors">
Section 15.6.6, “Cursors”
</a>
).
</p>
<p>
For more information, see
<a class="xref" href="group-replication-change-primary.html" title="20.5.1.1 Changing the Primary">
Section 20.5.1.1, “Changing the Primary”
</a>
.
</p>
</li>
</ul>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/audit-log-legacy-filtering.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="audit-log-legacy-filtering">
</a>
8.4.5.10 Legacy Mode Audit Log Filtering
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045236375088">
</a>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
This section describes legacy audit log filtering, which
applies if the
<code class="literal">
audit_log
</code>
plugin is
installed without the accompanying audit tables and functions
needed for rule-based filtering.
</p>
<p>
Legacy Mode Audit Log Filtering is deprecated.
</p>
</div>
<p>
The audit log plugin can filter audited events. This enables you
to control whether audited events are written to the audit log
file based on the account from which events originate or event
status. Status filtering occurs separately for connection events
and statement events.
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<a class="xref" href="audit-log-legacy-filtering.html#audit-log-account-filtering" title="Legacy Event Filtering by Account">
Legacy Event Filtering by Account
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="audit-log-legacy-filtering.html#audit-log-status-filtering" title="Legacy Event Filtering by Status">
Legacy Event Filtering by Status
</a>
</p>
</li>
</ul>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h5 class="title">
<a name="audit-log-account-filtering">
</a>
Legacy Event Filtering by Account
</h5>
</div>
</div>
</div>
<p>
To filter audited events based on the originating account, set
one (not both) of the following system variables at server
startup or runtime. These deprecated variables apply only for
legacy audit log filtering.
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<a class="link" href="audit-log-reference.html#sysvar_audit_log_include_accounts">
<code class="literal">
audit_log_include_accounts
</code>
</a>
:
The accounts to include in audit logging. If this variable
is set, only these accounts are audited.
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="audit-log-reference.html#sysvar_audit_log_exclude_accounts">
<code class="literal">
audit_log_exclude_accounts
</code>
</a>
:
The accounts to exclude from audit logging. If this
variable is set, all but these accounts are audited.
</p>
</li>
</ul>
</div>
<p>
The value for either variable can be
<code class="literal">
NULL
</code>
or a string containing one or more comma-separated account
names, each in
<code class="literal">
<em class="replaceable">
<code>
user_name
</code>
</em>
@
<em class="replaceable">
<code>
host_name
</code>
</em>
</code>
format. By default, both variables are
<code class="literal">
NULL
</code>
, in which case, no account filtering
is done and auditing occurs for all accounts.
</p>
<p>
Modifications to
<a class="link" href="audit-log-reference.html#sysvar_audit_log_include_accounts">
<code class="literal">
audit_log_include_accounts
</code>
</a>
or
<a class="link" href="audit-log-reference.html#sysvar_audit_log_exclude_accounts">
<code class="literal">
audit_log_exclude_accounts
</code>
</a>
affect only connections created subsequent to the
modification, not existing connections.
</p>
<p>
Example: To enable audit logging only for the
<code class="literal">
user1
</code>
and
<code class="literal">
user2
</code>
local
host accounts, set the
<a class="link" href="audit-log-reference.html#sysvar_audit_log_include_accounts">
<code class="literal">
audit_log_include_accounts
</code>
</a>
system variable like this:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa55317096"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SET</span> <span class="token keyword">GLOBAL</span> audit_log_include_accounts <span class="token operator">=</span> <span class="token string">'user1@localhost,user2@localhost'</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
Only one of
<a class="link" href="audit-log-reference.html#sysvar_audit_log_include_accounts">
<code class="literal">
audit_log_include_accounts
</code>
</a>
or
<a class="link" href="audit-log-reference.html#sysvar_audit_log_exclude_accounts">
<code class="literal">
audit_log_exclude_accounts
</code>
</a>
can be non-
<code class="literal">
NULL
</code>
at a time:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
If you set
<a class="link" href="audit-log-reference.html#sysvar_audit_log_include_accounts">
<code class="literal">
audit_log_include_accounts
</code>
</a>
,
the server sets
<a class="link" href="audit-log-reference.html#sysvar_audit_log_exclude_accounts">
<code class="literal">
audit_log_exclude_accounts
</code>
</a>
to
<code class="literal">
NULL
</code>
.
</p>
</li>
<li class="listitem">
<p>
If you attempt to set
<a class="link" href="audit-log-reference.html#sysvar_audit_log_exclude_accounts">
<code class="literal">
audit_log_exclude_accounts
</code>
</a>
,
an error occurs unless
<a class="link" href="audit-log-reference.html#sysvar_audit_log_include_accounts">
<code class="literal">
audit_log_include_accounts
</code>
</a>
is
<code class="literal">
NULL
</code>
. In this case, you must first
clear
<a class="link" href="audit-log-reference.html#sysvar_audit_log_include_accounts">
<code class="literal">
audit_log_include_accounts
</code>
</a>
by setting it to
<code class="literal">
NULL
</code>
.
</p>
</li>
</ul>
</div>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa87541658"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token comment" spellcheck="true">-- This sets audit_log_exclude_accounts to NULL</span>
<span class="token keyword">SET</span> <span class="token keyword">GLOBAL</span> audit_log_include_accounts <span class="token operator">=</span> <span class="token keyword"><em class="replaceable">value</em></span><span class="token punctuation">;</span>
<span class="token comment" spellcheck="true">-- This fails because audit_log_include_accounts is not NULL</span>
<span class="token keyword">SET</span> <span class="token keyword">GLOBAL</span> audit_log_exclude_accounts <span class="token operator">=</span> <span class="token keyword"><em class="replaceable">value</em></span><span class="token punctuation">;</span>
<span class="token comment" spellcheck="true">-- To set audit_log_exclude_accounts, first set</span>
<span class="token comment" spellcheck="true">-- audit_log_include_accounts to NULL</span>
<span class="token keyword">SET</span> <span class="token keyword">GLOBAL</span> audit_log_include_accounts <span class="token operator">=</span> <span class="token boolean">NULL</span><span class="token punctuation">;</span>
<span class="token keyword">SET</span> <span class="token keyword">GLOBAL</span> audit_log_exclude_accounts <span class="token operator">=</span> <span class="token keyword"><em class="replaceable">value</em></span><span class="token punctuation">;</span></code></pre>
</div>
<p>
If you inspect the value of either variable, be aware that
<a class="link" href="show-variables.html" title="15.7.7.41 SHOW VARIABLES Statement">
<code class="literal">
SHOW VARIABLES
</code>
</a>
displays
<code class="literal">
NULL
</code>
as an empty string. To display
<code class="literal">
NULL
</code>
as
<code class="literal">
NULL
</code>
, use
<a class="link" href="select.html" title="15.2.13 SELECT Statement">
<code class="literal">
SELECT
</code>
</a>
instead:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa60685885"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SHOW</span> <span class="token keyword">VARIABLES</span> <span class="token operator">LIKE</span> <span class="token string">'audit_log_include_accounts'</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> Variable_name <span class="token punctuation">|</span> Value <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> audit_log_include_accounts <span class="token punctuation">|</span> <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token variable">@@audit_log_include_accounts</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> @@audit_log_include_accounts <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> NULL <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
</div>
<p>
If a user name or host name requires quoting because it
contains a comma, space, or other special character, quote it
using single quotes. If the variable value itself is quoted
with single quotes, double each inner single quote or escape
it with a backslash. The following statements each enable
audit logging for the local
<code class="literal">
root
</code>
account
and are equivalent, even though the quoting styles differ:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa88243087"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SET</span> <span class="token keyword">GLOBAL</span> audit_log_include_accounts <span class="token operator">=</span> <span class="token string">'root@localhost'</span><span class="token punctuation">;</span>
<span class="token keyword">SET</span> <span class="token keyword">GLOBAL</span> audit_log_include_accounts <span class="token operator">=</span> <span class="token string">''</span><span class="token string">'root'</span><span class="token string">'@'</span><span class="token string">'localhost'</span><span class="token string">''</span><span class="token punctuation">;</span>
<span class="token keyword">SET</span> <span class="token keyword">GLOBAL</span> audit_log_include_accounts <span class="token operator">=</span> <span class="token string">'\'root\'@\'localhost\''</span><span class="token punctuation">;</span>
<span class="token keyword">SET</span> <span class="token keyword">GLOBAL</span> audit_log_include_accounts <span class="token operator">=</span> <span class="token string">"'root'@'localhost'"</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
The last statement does not work if the
<code class="literal">
ANSI_QUOTES
</code>
SQL mode is enabled because in
that mode double quotes signify identifier quoting, not string
quoting.
</p>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h5 class="title">
<a name="audit-log-status-filtering">
</a>
Legacy Event Filtering by Status
</h5>
</div>
</div>
</div>
<p>
To filter audited events based on status, set the following
system variables at server startup or runtime. These
deprecated variables apply only for legacy audit log
filtering. For JSON audit log filtering, different status
variables apply; see
<a class="xref" href="audit-log-reference.html#audit-log-options-variables" title="Audit Log Options and Variables">
Audit Log Options and Variables
</a>
.
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<a class="link" href="audit-log-reference.html#sysvar_audit_log_connection_policy">
<code class="literal">
audit_log_connection_policy
</code>
</a>
:
Logging policy for connection events
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="audit-log-reference.html#sysvar_audit_log_statement_policy">
<code class="literal">
audit_log_statement_policy
</code>
</a>
:
Logging policy for statement events
</p>
</li>
</ul>
</div>
<p>
Each variable takes a value of
<code class="literal">
ALL
</code>
(log all
associated events; this is the default),
<code class="literal">
ERRORS
</code>
(log only failed events), or
<code class="literal">
NONE
</code>
(do not log events). For example, to
log all statement events but only failed connection events,
use these settings:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa83659002"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SET</span> <span class="token keyword">GLOBAL</span> audit_log_statement_policy <span class="token operator">=</span> <span class="token keyword">ALL</span><span class="token punctuation">;</span>
<span class="token keyword">SET</span> <span class="token keyword">GLOBAL</span> audit_log_connection_policy <span class="token operator">=</span> <span class="token keyword">ERRORS</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
Another policy system variable,
<a class="link" href="audit-log-reference.html#sysvar_audit_log_policy">
<code class="literal">
audit_log_policy
</code>
</a>
, is
available but does not afford as much control as
<a class="link" href="audit-log-reference.html#sysvar_audit_log_connection_policy">
<code class="literal">
audit_log_connection_policy
</code>
</a>
and
<a class="link" href="audit-log-reference.html#sysvar_audit_log_statement_policy">
<code class="literal">
audit_log_statement_policy
</code>
</a>
.
It can be set only at server startup.
</p>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
The
<a class="link" href="audit-log-reference.html#sysvar_audit_log_policy">
<code class="literal">
audit_log_policy
</code>
</a>
legacy-mode system variable is deprecated.
</p>
</div>
<p>
At runtime, it is a read-only variable. It takes a value of
<code class="literal">
ALL
</code>
(log all events; this is the default),
<code class="literal">
LOGINS
</code>
(log connection events),
<code class="literal">
QUERIES
</code>
(log statement events), or
<code class="literal">
NONE
</code>
(do not log events). For any of those
values, the audit log plugin logs all selected events without
distinction as to success or failure. Use of
<a class="link" href="audit-log-reference.html#sysvar_audit_log_policy">
<code class="literal">
audit_log_policy
</code>
</a>
at startup
works as follows:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
If you do not set
<a class="link" href="audit-log-reference.html#sysvar_audit_log_policy">
<code class="literal">
audit_log_policy
</code>
</a>
or set
it to its default of
<code class="literal">
ALL
</code>
, any explicit
settings for
<a class="link" href="audit-log-reference.html#sysvar_audit_log_connection_policy">
<code class="literal">
audit_log_connection_policy
</code>
</a>
or
<a class="link" href="audit-log-reference.html#sysvar_audit_log_statement_policy">
<code class="literal">
audit_log_statement_policy
</code>
</a>
apply as specified. If not specified, they default to
<code class="literal">
ALL
</code>
.
</p>
</li>
<li class="listitem">
<p>
If you set
<a class="link" href="audit-log-reference.html#sysvar_audit_log_policy">
<code class="literal">
audit_log_policy
</code>
</a>
to a
non-
<code class="literal">
ALL
</code>
value, that value takes
precedence over and is used to set
<a class="link" href="audit-log-reference.html#sysvar_audit_log_connection_policy">
<code class="literal">
audit_log_connection_policy
</code>
</a>
and
<a class="link" href="audit-log-reference.html#sysvar_audit_log_statement_policy">
<code class="literal">
audit_log_statement_policy
</code>
</a>
,
as indicated in the following table. If you also set
either of those variables to a value other than their
default of
<code class="literal">
ALL
</code>
, the server writes a
message to the error log to indicate that their values are
being overridden.
</p>
<div class="informaltable">
<table summary="How the server uses audit_log_policy to set audit_log_connection_policy and audit_log_statement_policy at startup.">
<colgroup>
<col style="width: 33%"/>
<col style="width: 33%"/>
<col style="width: 33%"/>
</colgroup>
<thead>
<tr>
<th scope="col">
Startup audit_log_policy Value
</th>
<th scope="col">
Resulting audit_log_connection_policy Value
</th>
<th scope="col">
Resulting audit_log_statement_policy Value
</th>
</tr>
</thead>
<tbody>
<tr>
<th scope="row">
<code class="literal">
LOGINS
</code>
</th>
<td>
<code class="literal">
ALL
</code>
</td>
<td>
<code class="literal">
NONE
</code>
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
QUERIES
</code>
</th>
<td>
<code class="literal">
NONE
</code>
</td>
<td>
<code class="literal">
ALL
</code>
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
NONE
</code>
</th>
<td>
<code class="literal">
NONE
</code>
</td>
<td>
<code class="literal">
NONE
</code>
</td>
</tr>
</tbody>
</table>
</div>
</li>
</ul>
</div>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/corrupted-myisam-tables.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="corrupted-myisam-tables">
</a>
18.2.4.1 Corrupted MyISAM Tables
</h4>
</div>
</div>
</div>
<p>
Even though the
<code class="literal">
MyISAM
</code>
table format is very
reliable (all changes to a table made by an SQL statement are
written before the statement returns), you can still get
corrupted tables if any of the following events occur:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
The
<a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
<span class="command">
<strong>
mysqld
</strong>
</span>
</a>
process is killed in the
middle of a write.
</p>
</li>
<li class="listitem">
<p>
An unexpected computer shutdown occurs (for example, the
computer is turned off).
</p>
</li>
<li class="listitem">
<p>
Hardware failures.
</p>
</li>
<li class="listitem">
<p>
You are using an external program (such as
<a class="link" href="myisamchk.html" title="6.6.4 myisamchk — MyISAM Table-Maintenance Utility">
<span class="command">
<strong>
myisamchk
</strong>
</span>
</a>
) to modify a table that is
being modified by the server at the same time.
</p>
</li>
<li class="listitem">
<p>
A software bug in the MySQL or
<code class="literal">
MyISAM
</code>
code.
</p>
</li>
</ul>
</div>
<p>
Typical symptoms of a corrupt table are:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
You get the following error while selecting data from the
table:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-none"><div class="docs-select-all right" id="sa87936792"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-none">Incorrect key file for table: '...'. Try to repair it</code></pre>
</div>
</li>
<li class="listitem">
<p>
Queries don't find rows in the table or return incomplete
results.
</p>
</li>
</ul>
</div>
<p>
You can check the health of a
<code class="literal">
MyISAM
</code>
table
using the
<a class="link" href="check-table.html" title="15.7.3.2 CHECK TABLE Statement">
<code class="literal">
CHECK TABLE
</code>
</a>
statement,
and repair a corrupted
<code class="literal">
MyISAM
</code>
table with
<a class="link" href="repair-table.html" title="15.7.3.5 REPAIR TABLE Statement">
<code class="literal">
REPAIR TABLE
</code>
</a>
. When
<a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
<span class="command">
<strong>
mysqld
</strong>
</span>
</a>
is not running, you can also check or
repair a table with the
<a class="link" href="myisamchk.html" title="6.6.4 myisamchk — MyISAM Table-Maintenance Utility">
<span class="command">
<strong>
myisamchk
</strong>
</span>
</a>
command.
See
<a class="xref" href="check-table.html" title="15.7.3.2 CHECK TABLE Statement">
Section 15.7.3.2, “CHECK TABLE Statement”
</a>
,
<a class="xref" href="repair-table.html" title="15.7.3.5 REPAIR TABLE Statement">
Section 15.7.3.5, “REPAIR TABLE Statement”
</a>
, and
<a class="xref" href="myisamchk.html" title="6.6.4 myisamchk — MyISAM Table-Maintenance Utility">
Section 6.6.4, “myisamchk — MyISAM Table-Maintenance Utility”
</a>
.
</p>
<p>
If your tables become corrupted frequently, you should try to
determine why this is happening. The most important thing to
know is whether the table became corrupted as a result of an
unexpected server exit. You can verify this easily by looking
for a recent
<code class="literal">
restarted mysqld
</code>
message in the
error log. If there is such a message, it is likely that table
corruption is a result of the server dying. Otherwise,
corruption may have occurred during normal operation. This is a
bug. You should try to create a reproducible test case that
demonstrates the problem. See
<a class="xref" href="crashing.html" title="B.3.3.3 What to Do If MySQL Keeps Crashing">
Section B.3.3.3, “What to Do If MySQL Keeps Crashing”
</a>
, and
<a class="xref" href="debugging-mysql.html" title="7.9 Debugging MySQL">
Section 7.9, “Debugging MySQL”
</a>
.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/starting-server.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="starting-server">
</a>
2.9.2 Starting the Server
</h3>
</div>
</div>
</div>
<div class="toc">
<dl class="toc">
<dt>
<span class="section">
<a href="starting-server-troubleshooting.html">
2.9.2.1 Troubleshooting Problems Starting the MySQL Server
</a>
</span>
</dt>
</dl>
</div>
<p>
This section describes how start the server on Unix and Unix-like
systems. (For Windows, see
<a class="xref" href="windows-server-first-start.html" title="2.3.3.5 Starting the Server for the First Time">
Section 2.3.3.5, “Starting the Server for the First Time”
</a>
.) For some suggested
commands that you can use to test whether the server is accessible
and working properly, see
<a class="xref" href="testing-server.html" title="2.9.3 Testing the Server">
Section 2.9.3, “Testing the Server”
</a>
.
</p>
<p>
Start the MySQL server like this if your installation includes
<a class="link" href="mysqld-safe.html" title="6.3.2 mysqld_safe — MySQL Server Startup Script">
<span class="command">
<strong>
mysqld_safe
</strong>
</span>
</a>
:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-terminal"><div class="docs-select-all right" id="sa88520975"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-terminal"><span class="token prompt">$> </span><span class="token command">bin/mysqld_safe</span> <span class="token constant">--user</span><span class="token attr-value"><span class="token punctuation">=</span>mysql</span> &</code></pre>
</div>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
For Linux systems on which MySQL is installed using RPM
packages, server startup and shutdown is managed using systemd
rather than
<a class="link" href="mysqld-safe.html" title="6.3.2 mysqld_safe — MySQL Server Startup Script">
<span class="command">
<strong>
mysqld_safe
</strong>
</span>
</a>
, and
<a class="link" href="mysqld-safe.html" title="6.3.2 mysqld_safe — MySQL Server Startup Script">
<span class="command">
<strong>
mysqld_safe
</strong>
</span>
</a>
is not installed. See
<a class="xref" href="using-systemd.html" title="2.5.9 Managing MySQL Server with systemd">
Section 2.5.9, “Managing MySQL Server with systemd”
</a>
.
</p>
</div>
<p>
Start the server like this if your installation includes systemd
support:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-terminal"><div class="docs-select-all right" id="sa44517247"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-terminal"><span class="token prompt">$> </span><span class="token command">systemctl</span> start mysqld</code></pre>
</div>
<p>
Substitute the appropriate service name if it differs from
<code class="literal">
mysqld
</code>
(for example,
<code class="literal">
mysql
</code>
on SLES systems).
</p>
<p>
It is important that the MySQL server be run using an unprivileged
(non-
<code class="literal">
root
</code>
) login account. To ensure this, run
<a class="link" href="mysqld-safe.html" title="6.3.2 mysqld_safe — MySQL Server Startup Script">
<span class="command">
<strong>
mysqld_safe
</strong>
</span>
</a>
as
<code class="literal">
root
</code>
and
include the
<a class="link" href="mysqld-safe.html#option_mysqld_safe_user">
<code class="option">
--user
</code>
</a>
option as
shown. Otherwise, you should execute the program while logged in
as
<code class="literal">
mysql
</code>
, in which case you can omit the
<a class="link" href="mysqld-safe.html#option_mysqld_safe_user">
<code class="option">
--user
</code>
</a>
option from the
command.
</p>
<p>
For further instructions for running MySQL as an unprivileged
user, see
<a class="xref" href="changing-mysql-user.html" title="8.1.5 How to Run MySQL as a Normal User">
Section 8.1.5, “How to Run MySQL as a Normal User”
</a>
.
</p>
<p>
If the command fails immediately and prints
<code class="literal">
mysqld
ended
</code>
, look for information in the error log (which by
default is the
<code class="filename">
<em class="replaceable">
<code>
host_name
</code>
</em>
.err
</code>
file
in the data directory).
</p>
<p>
If the server is unable to access the data directory it starts or
read the grant tables in the
<code class="literal">
mysql
</code>
schema, it
writes a message to its error log. Such problems can occur if you
neglected to create the grant tables by initializing the data
directory before proceeding to this step, or if you ran the
command that initializes the data directory without the
<code class="option">
--user
</code>
option. Remove the
<code class="filename">
data
</code>
directory and run the command with the
<code class="option">
--user
</code>
option.
</p>
<p>
If you have other problems starting the server, see
<a class="xref" href="starting-server-troubleshooting.html" title="2.9.2.1 Troubleshooting Problems Starting the MySQL Server">
Section 2.9.2.1, “Troubleshooting Problems Starting the MySQL Server”
</a>
. For more
information about
<a class="link" href="mysqld-safe.html" title="6.3.2 mysqld_safe — MySQL Server Startup Script">
<span class="command">
<strong>
mysqld_safe
</strong>
</span>
</a>
, see
<a class="xref" href="mysqld-safe.html" title="6.3.2 mysqld_safe — MySQL Server Startup Script">
Section 6.3.2, “mysqld_safe — MySQL Server Startup Script”
</a>
. For more information about systemd
support, see
<a class="xref" href="using-systemd.html" title="2.5.9 Managing MySQL Server with systemd">
Section 2.5.9, “Managing MySQL Server with systemd”
</a>
.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/mysql-cluster-programs-ndb-print-frag-file.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="mysql-cluster-programs-ndb-print-frag-file">
</a>
25.5.19 ndb_print_frag_file — Print NDB Fragment List File Contents
</h3>
</div>
</div>
</div>
<a class="indexterm" name="idm46045100069120">
</a>
<p>
<a class="link" href="mysql-cluster-programs-ndb-print-frag-file.html" title="25.5.19 ndb_print_frag_file — Print NDB Fragment List File Contents">
<span class="command">
<strong>
ndb_print_frag_file
</strong>
</span>
</a>
obtains information from
a cluster fragment list file. It is intended for use in helping
to diagnose issues with data node restarts.
</p>
<h4>
<a name="idm46045100066160">
</a>
Usage
</h4>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-terminal"><div class="docs-select-all right" id="sa71064168"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-terminal">ndb_print_frag_file <em class="replaceable">file_name</em></code></pre>
</div>
<p>
<em class="replaceable">
<code>
file_name
</code>
</em>
is the name of a cluster
fragment list file, which matches the pattern
<code class="filename">
S
<em class="replaceable">
<code>
X
</code>
</em>
.FragList
</code>
,
where
<em class="replaceable">
<code>
X
</code>
</em>
is a digit in the range 2-9
inclusive, and are found in the data node file system of the
data node having the node ID
<em class="replaceable">
<code>
nodeid
</code>
</em>
,
in directories named
<code class="filename">
ndb_
<em class="replaceable">
<code>
nodeid
</code>
</em>
_fs/D
<em class="replaceable">
<code>
N
</code>
</em>
/DBDIH/
</code>
,
where
<em class="replaceable">
<code>
N
</code>
</em>
is
<code class="literal">
1
</code>
or
<code class="literal">
2
</code>
. Each fragment file contains records of the
fragments belonging to each
<code class="literal">
NDB
</code>
table. For
more information about cluster fragment files, see
<a class="ulink" href="/doc/ndb-internals/en/ndb-internals-ndbd-filesystemdir-files.html" target="_top">
NDB Cluster Data Node File System Directory
</a>
.
</p>
<p>
Like
<a class="link" href="mysql-cluster-programs-ndb-print-backup-file.html" title="25.5.17 ndb_print_backup_file — Print NDB Backup File Contents">
<span class="command">
<strong>
ndb_print_backup_file
</strong>
</span>
</a>
,
<a class="link" href="mysql-cluster-programs-ndb-print-sys-file.html" title="25.5.21 ndb_print_sys_file — Print NDB System File Contents">
<span class="command">
<strong>
ndb_print_sys_file
</strong>
</span>
</a>
, and
<a class="link" href="mysql-cluster-programs-ndb-print-schema-file.html" title="25.5.20 ndb_print_schema_file — Print NDB Schema File Contents">
<span class="command">
<strong>
ndb_print_schema_file
</strong>
</span>
</a>
(and unlike most of the
other
<a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4">
<code class="literal">
NDB
</code>
</a>
utilities that are
intended to be run on a management server host or to connect to
a management server),
<a class="link" href="mysql-cluster-programs-ndb-print-frag-file.html" title="25.5.19 ndb_print_frag_file — Print NDB Fragment List File Contents">
<span class="command">
<strong>
ndb_print_frag_file
</strong>
</span>
</a>
must be run on a cluster data node, since it accesses the data
node file system directly. Because it does not make use of the
management server, this utility can be used when the management
server is not running, and even when the cluster has been
completely shut down.
</p>
<h4>
<a name="idm46045100048848">
</a>
Additional Options
</h4>
<p>
None.
</p>
<h4>
<a name="idm46045100047744">
</a>
Sample Output
</h4>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-terminal"><div class="docs-select-all right" id="sa95100275"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-terminal"><span class="token prompt">$> </span><span class="token command">ndb_print_frag_file</span> /usr/local/mysqld/data/ndb_3_fs/D1/DBDIH/S2<span class="token punctuation">.</span>FragList
Filename<span class="token punctuation">:</span> /usr/local/mysqld/data/ndb_3_fs/D1/DBDIH/S2<span class="token punctuation">.</span>FragList with size 8192
noOfPages = 1 noOfWords = 182
Table Data
<span class="token property">----------</span>
Num Frags<span class="token punctuation">:</span> 2 NoOfReplicas<span class="token punctuation">:</span> 2 hashpointer<span class="token punctuation">:</span> 4294967040
kvalue<span class="token punctuation">:</span> 6 mask<span class="token punctuation">:</span> 0x00000000 method<span class="token punctuation">:</span> HashMap
Storage is on Logged and checkpointed<span class="token punctuation">,</span> survives SR
<span class="token property">------</span> Fragment with FragId<span class="token punctuation">:</span> 0 <span class="token property">--------</span>
Preferred Primary<span class="token punctuation">:</span> 2 numStoredReplicas<span class="token punctuation">:</span> 2 numOldStoredReplicas<span class="token punctuation">:</span> 0 distKey<span class="token punctuation">:</span> 0 LogPartId<span class="token punctuation">:</span> 0
<span class="token property">-------Stored</span> Replica----------
Replica node is<span class="token punctuation">:</span> 2 initialGci<span class="token punctuation">:</span> 2 numCrashedReplicas = 0 nextLcpNo = 1
LcpNo<span class="token punctuation">[</span>0<span class="token punctuation">]</span><span class="token punctuation">:</span> maxGciCompleted<span class="token punctuation">:</span> 1 maxGciStarted<span class="token punctuation">:</span> 2 lcpId<span class="token punctuation">:</span> 1 lcpStatus<span class="token punctuation">:</span> valid
LcpNo<span class="token punctuation">[</span>1<span class="token punctuation">]</span><span class="token punctuation">:</span> maxGciCompleted<span class="token punctuation">:</span> 0 maxGciStarted<span class="token punctuation">:</span> 0 lcpId<span class="token punctuation">:</span> 0 lcpStatus<span class="token punctuation">:</span> invalid
<span class="token property">-------Stored</span> Replica----------
Replica node is<span class="token punctuation">:</span> 3 initialGci<span class="token punctuation">:</span> 2 numCrashedReplicas = 0 nextLcpNo = 1
LcpNo<span class="token punctuation">[</span>0<span class="token punctuation">]</span><span class="token punctuation">:</span> maxGciCompleted<span class="token punctuation">:</span> 1 maxGciStarted<span class="token punctuation">:</span> 2 lcpId<span class="token punctuation">:</span> 1 lcpStatus<span class="token punctuation">:</span> valid
LcpNo<span class="token punctuation">[</span>1<span class="token punctuation">]</span><span class="token punctuation">:</span> maxGciCompleted<span class="token punctuation">:</span> 0 maxGciStarted<span class="token punctuation">:</span> 0 lcpId<span class="token punctuation">:</span> 0 lcpStatus<span class="token punctuation">:</span> invalid
<span class="token property">------</span> Fragment with FragId<span class="token punctuation">:</span> 1 <span class="token property">--------</span>
Preferred Primary<span class="token punctuation">:</span> 3 numStoredReplicas<span class="token punctuation">:</span> 2 numOldStoredReplicas<span class="token punctuation">:</span> 0 distKey<span class="token punctuation">:</span> 0 LogPartId<span class="token punctuation">:</span> 1
<span class="token property">-------Stored</span> Replica----------
Replica node is<span class="token punctuation">:</span> 3 initialGci<span class="token punctuation">:</span> 2 numCrashedReplicas = 0 nextLcpNo = 1
LcpNo<span class="token punctuation">[</span>0<span class="token punctuation">]</span><span class="token punctuation">:</span> maxGciCompleted<span class="token punctuation">:</span> 1 maxGciStarted<span class="token punctuation">:</span> 2 lcpId<span class="token punctuation">:</span> 1 lcpStatus<span class="token punctuation">:</span> valid
LcpNo<span class="token punctuation">[</span>1<span class="token punctuation">]</span><span class="token punctuation">:</span> maxGciCompleted<span class="token punctuation">:</span> 0 maxGciStarted<span class="token punctuation">:</span> 0 lcpId<span class="token punctuation">:</span> 0 lcpStatus<span class="token punctuation">:</span> invalid
<span class="token property">-------Stored</span> Replica----------
Replica node is<span class="token punctuation">:</span> 2 initialGci<span class="token punctuation">:</span> 2 numCrashedReplicas = 0 nextLcpNo = 1
LcpNo<span class="token punctuation">[</span>0<span class="token punctuation">]</span><span class="token punctuation">:</span> maxGciCompleted<span class="token punctuation">:</span> 1 maxGciStarted<span class="token punctuation">:</span> 2 lcpId<span class="token punctuation">:</span> 1 lcpStatus<span class="token punctuation">:</span> valid
LcpNo<span class="token punctuation">[</span>1<span class="token punctuation">]</span><span class="token punctuation">:</span> maxGciCompleted<span class="token punctuation">:</span> 0 maxGciStarted<span class="token punctuation">:</span> 0 lcpId<span class="token punctuation">:</span> 0 lcpStatus<span class="token punctuation">:</span> invalid</code></pre>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/performance-schema-statement-tables.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="performance-schema-statement-tables">
</a>
29.12.6 Performance Schema Statement Event Tables
</h3>
</div>
</div>
</div>
<div class="toc">
<dl class="toc">
<dt>
<span class="section">
<a href="performance-schema-events-statements-current-table.html">
29.12.6.1 The events_statements_current Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="performance-schema-events-statements-history-table.html">
29.12.6.2 The events_statements_history Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="performance-schema-events-statements-history-long-table.html">
29.12.6.3 The events_statements_history_long Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="performance-schema-prepared-statements-instances-table.html">
29.12.6.4 The prepared_statements_instances Table
</a>
</span>
</dt>
</dl>
</div>
<p>
The Performance Schema instruments statement execution.
Statement events occur at a high level of the event hierarchy.
Within the event hierarchy, wait events nest within stage
events, which nest within statement events, which nest within
transaction events.
</p>
<p>
These tables store statement events:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<a class="link" href="performance-schema-events-statements-current-table.html" title="29.12.6.1 The events_statements_current Table">
<code class="literal">
events_statements_current
</code>
</a>
: The
current statement event for each thread.
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="performance-schema-events-statements-history-table.html" title="29.12.6.2 The events_statements_history Table">
<code class="literal">
events_statements_history
</code>
</a>
: The
most recent statement events that have ended per thread.
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="performance-schema-events-statements-history-long-table.html" title="29.12.6.3 The events_statements_history_long Table">
<code class="literal">
events_statements_history_long
</code>
</a>
:
The most recent statement events that have ended globally
(across all threads).
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="performance-schema-prepared-statements-instances-table.html" title="29.12.6.4 The prepared_statements_instances Table">
<code class="literal">
prepared_statements_instances
</code>
</a>
:
Prepared statement instances and statistics
</p>
</li>
</ul>
</div>
<p>
The following sections describe the statement event tables.
There are also summary tables that aggregate information about
statement events; see
<a class="xref" href="performance-schema-statement-summary-tables.html" title="29.12.20.3 Statement Summary Tables">
Section 29.12.20.3, “Statement Summary Tables”
</a>
.
</p>
<p>
For more information about the relationship between the three
<code class="literal">
events_statements_
<em class="replaceable">
<code>
xxx
</code>
</em>
</code>
event tables, see
<a class="xref" href="performance-schema-event-tables.html" title="29.9 Performance Schema Tables for Current and Historical Events">
Section 29.9, “Performance Schema Tables for Current and Historical Events”
</a>
.
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<a class="xref" href="performance-schema-statement-tables.html#performance-schema-statement-tables-configuration" title="Configuring Statement Event Collection">
Configuring Statement Event Collection
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="performance-schema-statement-tables.html#performance-schema-statement-tables-monitoring" title="Statement Monitoring">
Statement Monitoring
</a>
</p>
</li>
</ul>
</div>
<h4>
<a name="performance-schema-statement-tables-configuration">
</a>
Configuring Statement Event Collection
</h4>
<p>
To control whether to collect statement events, set the state of
the relevant instruments and consumers:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
The
<a class="link" href="performance-schema-setup-instruments-table.html" title="29.12.2.3 The setup_instruments Table">
<code class="literal">
setup_instruments
</code>
</a>
table
contains instruments with names that begin with
<code class="literal">
statement
</code>
. Use these instruments to
enable or disable collection of individual statement event
classes.
</p>
</li>
<li class="listitem">
<p>
The
<a class="link" href="performance-schema-setup-consumers-table.html" title="29.12.2.2 The setup_consumers Table">
<code class="literal">
setup_consumers
</code>
</a>
table
contains consumer values with names corresponding to the
current and historical statement event table names, and the
statement digest consumer. Use these consumers to filter
collection of statement events and statement digesting.
</p>
</li>
</ul>
</div>
<p>
The statement instruments are enabled by default, and the
<code class="literal">
events_statements_current
</code>
,
<code class="literal">
events_statements_history
</code>
, and
<code class="literal">
statements_digest
</code>
statement consumers are
enabled by default:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa85406825"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token keyword">NAME</span><span class="token punctuation">,</span> ENABLED<span class="token punctuation">,</span> TIMED
<span class="token keyword">FROM</span> performance_schema<span class="token punctuation">.</span>setup_instruments
<span class="token keyword">WHERE</span> <span class="token keyword">NAME</span> <span class="token operator">LIKE</span> <span class="token string">'statement/%'</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> NAME <span class="token punctuation">|</span> ENABLED <span class="token punctuation">|</span> TIMED <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> statement/sql/select <span class="token punctuation">|</span> YES <span class="token punctuation">|</span> YES <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> statement/sql/create_table <span class="token punctuation">|</span> YES <span class="token punctuation">|</span> YES <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> statement/sql/create_index <span class="token punctuation">|</span> YES <span class="token punctuation">|</span> YES <span class="token punctuation">|</span></span>
<span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span>
<span class="token output"><span class="token punctuation">|</span> statement/sp/stmt <span class="token punctuation">|</span> YES <span class="token punctuation">|</span> YES <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> statement/sp/set <span class="token punctuation">|</span> YES <span class="token punctuation">|</span> YES <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> statement/sp/set_trigger_field <span class="token punctuation">|</span> YES <span class="token punctuation">|</span> YES <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> statement/scheduler/event <span class="token punctuation">|</span> YES <span class="token punctuation">|</span> YES <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> statement/com/Sleep <span class="token punctuation">|</span> YES <span class="token punctuation">|</span> YES <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> statement/com/Quit <span class="token punctuation">|</span> YES <span class="token punctuation">|</span> YES <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> statement/com/Init DB <span class="token punctuation">|</span> YES <span class="token punctuation">|</span> YES <span class="token punctuation">|</span></span>
<span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span>
<span class="token output"><span class="token punctuation">|</span> statement/abstract/Query <span class="token punctuation">|</span> YES <span class="token punctuation">|</span> YES <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> statement/abstract/new_packet <span class="token punctuation">|</span> YES <span class="token punctuation">|</span> YES <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> statement/abstract/relay_log <span class="token punctuation">|</span> YES <span class="token punctuation">|</span> YES <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
</div>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa6597527"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token operator">*</span>
<span class="token keyword">FROM</span> performance_schema<span class="token punctuation">.</span>setup_consumers
<span class="token keyword">WHERE</span> <span class="token keyword">NAME</span> <span class="token operator">LIKE</span> <span class="token string">'%statements%'</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> NAME <span class="token punctuation">|</span> ENABLED <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> events_statements_current <span class="token punctuation">|</span> YES <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> events_statements_history <span class="token punctuation">|</span> YES <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> events_statements_history_long <span class="token punctuation">|</span> NO <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> statements_digest <span class="token punctuation">|</span> YES <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
</div>
<p>
To control statement event collection at server startup, use
lines like these in your
<code class="filename">
my.cnf
</code>
file:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
Enable:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-ini"><div class="docs-select-all right" id="sa15549469"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-ini"><span class="token selector">[mysqld]</span>
<span class="token constant">performance-schema-instrument</span><span class="token attr-value"><span class="token punctuation">=</span>'statement/%=ON'</span>
<span class="token constant">performance-schema-consumer-events-statements-current</span><span class="token attr-value"><span class="token punctuation">=</span>ON</span>
<span class="token constant">performance-schema-consumer-events-statements-history</span><span class="token attr-value"><span class="token punctuation">=</span>ON</span>
<span class="token constant">performance-schema-consumer-events-statements-history-long</span><span class="token attr-value"><span class="token punctuation">=</span>ON</span>
<span class="token constant">performance-schema-consumer-statements-digest</span><span class="token attr-value"><span class="token punctuation">=</span>ON</span></code></pre>
</div>
</li>
<li class="listitem">
<p>
Disable:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-ini"><div class="docs-select-all right" id="sa64807089"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-ini"><span class="token selector">[mysqld]</span>
<span class="token constant">performance-schema-instrument</span><span class="token attr-value"><span class="token punctuation">=</span>'statement/%=OFF'</span>
<span class="token constant">performance-schema-consumer-events-statements-current</span><span class="token attr-value"><span class="token punctuation">=</span>OFF</span>
<span class="token constant">performance-schema-consumer-events-statements-history</span><span class="token attr-value"><span class="token punctuation">=</span>OFF</span>
<span class="token constant">performance-schema-consumer-events-statements-history-long</span><span class="token attr-value"><span class="token punctuation">=</span>OFF</span>
<span class="token constant">performance-schema-consumer-statements-digest</span><span class="token attr-value"><span class="token punctuation">=</span>OFF</span></code></pre>
</div>
</li>
</ul>
</div>
<p>
To control statement event collection at runtime, update the
<a class="link" href="performance-schema-setup-instruments-table.html" title="29.12.2.3 The setup_instruments Table">
<code class="literal">
setup_instruments
</code>
</a>
and
<a class="link" href="performance-schema-setup-consumers-table.html" title="29.12.2.2 The setup_consumers Table">
<code class="literal">
setup_consumers
</code>
</a>
tables:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
Enable:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa91103702"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">UPDATE</span> performance_schema<span class="token punctuation">.</span>setup_instruments
<span class="token keyword">SET</span> ENABLED <span class="token operator">=</span> <span class="token string">'YES'</span><span class="token punctuation">,</span> TIMED <span class="token operator">=</span> <span class="token string">'YES'</span>
<span class="token keyword">WHERE</span> <span class="token keyword">NAME</span> <span class="token operator">LIKE</span> <span class="token string">'statement/%'</span><span class="token punctuation">;</span>
<span class="token keyword">UPDATE</span> performance_schema<span class="token punctuation">.</span>setup_consumers
<span class="token keyword">SET</span> ENABLED <span class="token operator">=</span> <span class="token string">'YES'</span>
<span class="token keyword">WHERE</span> <span class="token keyword">NAME</span> <span class="token operator">LIKE</span> <span class="token string">'%statements%'</span><span class="token punctuation">;</span></code></pre>
</div>
</li>
<li class="listitem">
<p>
Disable:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa41402211"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">UPDATE</span> performance_schema<span class="token punctuation">.</span>setup_instruments
<span class="token keyword">SET</span> ENABLED <span class="token operator">=</span> <span class="token string">'NO'</span><span class="token punctuation">,</span> TIMED <span class="token operator">=</span> <span class="token string">'NO'</span>
<span class="token keyword">WHERE</span> <span class="token keyword">NAME</span> <span class="token operator">LIKE</span> <span class="token string">'statement/%'</span><span class="token punctuation">;</span>
<span class="token keyword">UPDATE</span> performance_schema<span class="token punctuation">.</span>setup_consumers
<span class="token keyword">SET</span> ENABLED <span class="token operator">=</span> <span class="token string">'NO'</span>
<span class="token keyword">WHERE</span> <span class="token keyword">NAME</span> <span class="token operator">LIKE</span> <span class="token string">'%statements%'</span><span class="token punctuation">;</span></code></pre>
</div>
</li>
</ul>
</div>
<p>
To collect only specific statement events, enable only the
corresponding statement instruments. To collect statement events
only for specific statement event tables, enable the statement
instruments but only the statement consumers corresponding to
the desired tables.
</p>
<p>
For additional information about configuring event collection,
see
<a class="xref" href="performance-schema-startup-configuration.html" title="29.3 Performance Schema Startup Configuration">
Section 29.3, “Performance Schema Startup Configuration”
</a>
,
and
<a class="xref" href="performance-schema-runtime-configuration.html" title="29.4 Performance Schema Runtime Configuration">
Section 29.4, “Performance Schema Runtime Configuration”
</a>
.
</p>
<h4>
<a name="performance-schema-statement-tables-monitoring">
</a>
Statement Monitoring
</h4>
<p>
Statement monitoring begins from the moment the server sees that
activity is requested on a thread, to the moment when all
activity has ceased. Typically, this means from the time the
server gets the first packet from the client to the time the
server has finished sending the response. Statements within
stored programs are monitored like other statements.
</p>
<p>
When the Performance Schema instruments a request (server
command or SQL statement), it uses instrument names that proceed
in stages from more general (or
<span class="quote">
“
<span class="quote">
abstract
</span>
”
</span>
) to more
specific until it arrives at a final instrument name.
</p>
<p>
Final instrument names correspond to server commands and SQL
statements:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
Server commands correspond to the
<code class="literal">
COM_
<em class="replaceable">
<code>
xxx
</code>
</em>
codes
</code>
defined in the
<code class="filename">
mysql_com.h
</code>
header file
and processed in
<code class="filename">
sql/sql_parse.cc
</code>
.
Examples are
<code class="literal">
COM_PING
</code>
and
<code class="literal">
COM_QUIT
</code>
. Instruments for commands have
names that begin with
<code class="literal">
statement/com
</code>
, such
as
<code class="literal">
statement/com/Ping
</code>
and
<code class="literal">
statement/com/Quit
</code>
.
</p>
</li>
<li class="listitem">
<p>
SQL statements are expressed as text, such as
<code class="literal">
DELETE FROM t1
</code>
or
<code class="literal">
SELECT * FROM
t2
</code>
. Instruments for SQL statements have names that
begin with
<code class="literal">
statement/sql
</code>
, such as
<code class="literal">
statement/sql/delete
</code>
and
<code class="literal">
statement/sql/select
</code>
.
</p>
</li>
</ul>
</div>
<p>
Some final instrument names are specific to error handling:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<code class="literal">
statement/com/Error
</code>
accounts for messages
received by the server that are out of band. It can be used
to detect commands sent by clients that the server does not
understand. This may be helpful for purposes such as
identifying clients that are misconfigured or using a
version of MySQL more recent than that of the server, or
clients that are attempting to attack the server.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
statement/sql/error
</code>
accounts for SQL
statements that fail to parse. It can be used to detect
malformed queries sent by clients. A query that fails to
parse differs from a query that parses but fails due to an
error during execution. For example,
<code class="literal">
SELECT *
FROM
</code>
is malformed, and the
<code class="literal">
statement/sql/error
</code>
instrument is used.
By contrast,
<code class="literal">
SELECT *
</code>
parses but fails
with a
<code class="literal">
No tables used
</code>
error. In this
case,
<code class="literal">
statement/sql/select
</code>
is used and
the statement event contains information to indicate the
nature of the error.
</p>
</li>
</ul>
</div>
<p>
A request can be obtained from any of these sources:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
As a command or statement request from a client, which sends
the request as packets
</p>
</li>
<li class="listitem">
<p>
As a statement string read from the relay log on a replica
</p>
</li>
<li class="listitem">
<p>
As an event from the Event Scheduler
</p>
</li>
</ul>
</div>
<p>
The details for a request are not initially known and the
Performance Schema proceeds from abstract to specific instrument
names in a sequence that depends on the source of the request.
</p>
<p>
For a request received from a client:
</p>
<div class="orderedlist">
<ol class="orderedlist" type="1">
<li class="listitem">
<p>
When the server detects a new packet at the socket level, a
new statement is started with an abstract instrument name of
<code class="literal">
statement/abstract/new_packet
</code>
.
</p>
</li>
<li class="listitem">
<p>
When the server reads the packet number, it knows more about
the type of request received, and the Performance Schema
refines the instrument name. For example, if the request is
a
<code class="literal">
COM_PING
</code>
packet, the instrument name
becomes
<code class="literal">
statement/com/Ping
</code>
and that is
the final name. If the request is a
<code class="literal">
COM_QUERY
</code>
packet, it is known to
correspond to an SQL statement but not the particular type
of statement. In this case, the instrument changes from one
abstract name to a more specific but still abstract name,
<code class="literal">
statement/abstract/Query
</code>
, and the request
requires further classification.
</p>
</li>
<li class="listitem">
<p>
If the request is a statement, the statement text is read
and given to the parser. After parsing, the exact statement
type is known. If the request is, for example, an
<a class="link" href="insert.html" title="15.2.7 INSERT Statement">
<code class="literal">
INSERT
</code>
</a>
statement, the
Performance Schema refines the instrument name from
<code class="literal">
statement/abstract/Query
</code>
to
<code class="literal">
statement/sql/insert
</code>
, which is the final
name.
</p>
</li>
</ol>
</div>
<p>
For a request read as a statement from the relay log on a
replica:
</p>
<div class="orderedlist">
<ol class="orderedlist" type="1">
<li class="listitem">
<p>
Statements in the relay log are stored as text and are read
as such. There is no network protocol, so the
<code class="literal">
statement/abstract/new_packet
</code>
instrument
is not used. Instead, the initial instrument is
<code class="literal">
statement/abstract/relay_log
</code>
.
</p>
</li>
<li class="listitem">
<p>
When the statement is parsed, the exact statement type is
known. If the request is, for example, an
<a class="link" href="insert.html" title="15.2.7 INSERT Statement">
<code class="literal">
INSERT
</code>
</a>
statement, the
Performance Schema refines the instrument name from
<code class="literal">
statement/abstract/Query
</code>
to
<code class="literal">
statement/sql/insert
</code>
, which is the final
name.
</p>
</li>
</ol>
</div>
<p>
The preceding description applies only for statement-based
replication. For row-based replication, table I/O done on the
replica as it processes row changes can be instrumented, but row
events in the relay log do not appear as discrete statements.
</p>
<p>
For a request received from the Event Scheduler:
</p>
<p>
The event execution is instrumented using the name
<code class="literal">
statement/scheduler/event
</code>
. This is the final
name.
</p>
<p>
Statements executed within the event body are instrumented using
<code class="literal">
statement/sql/*
</code>
names, without use of any
preceding abstract instrument. An event is a stored program, and
stored programs are precompiled in memory before execution.
Consequently, there is no parsing at runtime and the type of
each statement is known by the time it executes.
</p>
<p>
Statements executed within the event body are child statements.
For example, if an event executes an
<a class="link" href="insert.html" title="15.2.7 INSERT Statement">
<code class="literal">
INSERT
</code>
</a>
statement, execution of
the event itself is the parent, instrumented using
<code class="literal">
statement/scheduler/event
</code>
, and the
<a class="link" href="insert.html" title="15.2.7 INSERT Statement">
<code class="literal">
INSERT
</code>
</a>
is the child, instrumented
using
<code class="literal">
statement/sql/insert
</code>
. The parent/child
relationship holds
<span class="emphasis">
<em>
between
</em>
</span>
separate
instrumented operations. This differs from the sequence of
refinement that occurs
<span class="emphasis">
<em>
within
</em>
</span>
a single
instrumented operation, from abstract to final instrument names.
</p>
<p>
For statistics to be collected for statements, it is not
sufficient to enable only the final
<code class="literal">
statement/sql/*
</code>
instruments used for
individual statement types. The abstract
<code class="literal">
statement/abstract/*
</code>
instruments must be
enabled as well. This should not normally be an issue because
all statement instruments are enabled by default. However, an
application that enables or disables statement instruments
selectively must take into account that disabling abstract
instruments also disables statistics collection for the
individual statement instruments. For example, to collect
statistics for
<a class="link" href="insert.html" title="15.2.7 INSERT Statement">
<code class="literal">
INSERT
</code>
</a>
statements,
<code class="literal">
statement/sql/insert
</code>
must be enabled, but
also
<code class="literal">
statement/abstract/new_packet
</code>
and
<code class="literal">
statement/abstract/Query
</code>
. Similarly, for
replicated statements to be instrumented,
<code class="literal">
statement/abstract/relay_log
</code>
must be enabled.
</p>
<p>
No statistics are aggregated for abstract instruments such as
<code class="literal">
statement/abstract/Query
</code>
because no statement
is ever classified with an abstract instrument as the final
statement name.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/string-collating.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="string-collating">
</a>
12.13.2 String Collating Support for Complex Character Sets
</h3>
</div>
</div>
</div>
<a class="indexterm" name="idm46045215314784">
</a>
<a class="indexterm" name="idm46045215313328">
</a>
<p>
For a simple character set named
<em class="replaceable">
<code>
MYSET
</code>
</em>
, sorting rules are specified in
the
<code class="filename">
<em class="replaceable">
<code>
MYSET
</code>
</em>
.xml
</code>
configuration file using
<code class="literal">
<map>
</code>
array
elements within
<code class="literal">
<collation>
</code>
elements.
If the sorting rules for your language are too complex to be
handled with simple arrays, you must define string collating
functions in the
<code class="filename">
ctype-
<em class="replaceable">
<code>
MYSET
</code>
</em>
.c
</code>
source file in the
<code class="filename">
strings
</code>
directory.
</p>
<p>
The existing character sets provide the best documentation and
examples to show how these functions are implemented. Look at
the
<code class="filename">
ctype-*.c
</code>
files in the
<code class="filename">
strings
</code>
directory, such as the files for
the
<code class="literal">
big5
</code>
,
<code class="literal">
czech
</code>
,
<code class="literal">
gbk
</code>
,
<code class="literal">
sjis
</code>
, and
<code class="literal">
tis160
</code>
character sets. Take a look at the
<code class="literal">
MY_COLLATION_HANDLER
</code>
structures to see how
they are used. See also the
<code class="filename">
CHARSET_INFO.txt
</code>
file in the
<code class="filename">
strings
</code>
directory for additional
information.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/sys-extract-schema-from-file-name.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="sys-extract-schema-from-file-name">
</a>
30.4.5.1 The extract_schema_from_file_name() Function
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045061051392">
</a>
<a class="indexterm" name="idm46045061049872">
</a>
<p>
Given a file path name, returns the path component that
represents the schema name. This function assumes that the
file name lies within the schema directory. For this reason,
it does not work with partitions or tables defined using their
own
<code class="literal">
DATA_DIRECTORY
</code>
table option.
</p>
<p>
This function is useful when extracting file I/O information
from the Performance Schema that includes file path names. It
provides a convenient way to display schema names, which can
be more easily understood than full path names, and can be
used in joins against object schema names.
</p>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h5 class="title">
<a name="sys-extract-schema-from-file-name-parameters">
</a>
Parameters
</h5>
</div>
</div>
</div>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<code class="literal">
path VARCHAR(512)
</code>
: The full path to a
data file from which to extract the schema name.
</p>
</li>
</ul>
</div>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h5 class="title">
<a name="sys-extract-schema-from-file-name-return-value">
</a>
Return Value
</h5>
</div>
</div>
</div>
<p>
A
<code class="literal">
VARCHAR(64)
</code>
value.
</p>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h5 class="title">
<a name="sys-extract-schema-from-file-name-example">
</a>
Example
</h5>
</div>
</div>
</div>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa60936147"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> sys<span class="token punctuation">.</span>extract_schema_from_file_name<span class="token punctuation">(</span><span class="token string">'/usr/local/mysql/data/world/City.ibd'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> sys.extract_schema_from_file_name('/usr/local/mysql/data/world/City.ibd') <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> world <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
</div>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/data-dictionary-information-schema.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h2 class="title">
<a name="data-dictionary-information-schema">
</a>
16.5 INFORMATION_SCHEMA and Data Dictionary Integration
</h2>
</div>
</div>
</div>
<a class="indexterm" name="idm46045167705200">
</a>
<p>
With the introduction of the data dictionary, the following
<a class="link" href="information-schema.html" title="Chapter 28 INFORMATION_SCHEMA Tables">
<code class="literal">
INFORMATION_SCHEMA
</code>
</a>
tables are
implemented as views on data dictionary tables:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<a class="link" href="information-schema-character-sets-table.html" title="28.3.4 The INFORMATION_SCHEMA CHARACTER_SETS Table">
<code class="literal">
CHARACTER_SETS
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="information-schema-check-constraints-table.html" title="28.3.5 The INFORMATION_SCHEMA CHECK_CONSTRAINTS Table">
<code class="literal">
CHECK_CONSTRAINTS
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="information-schema-collations-table.html" title="28.3.6 The INFORMATION_SCHEMA COLLATIONS Table">
<code class="literal">
COLLATIONS
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="information-schema-collation-character-set-applicability-table.html" title="28.3.7 The INFORMATION_SCHEMA COLLATION_CHARACTER_SET_APPLICABILITY Table">
<code class="literal">
COLLATION_CHARACTER_SET_APPLICABILITY
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="information-schema-columns-table.html" title="28.3.8 The INFORMATION_SCHEMA COLUMNS Table">
<code class="literal">
COLUMNS
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="information-schema-column-statistics-table.html" title="28.3.11 The INFORMATION_SCHEMA COLUMN_STATISTICS Table">
<code class="literal">
COLUMN_STATISTICS
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="information-schema-events-table.html" title="28.3.14 The INFORMATION_SCHEMA EVENTS Table">
<code class="literal">
EVENTS
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="information-schema-files-table.html" title="28.3.15 The INFORMATION_SCHEMA FILES Table">
<code class="literal">
FILES
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="information-schema-innodb-columns-table.html" title="28.4.9 The INFORMATION_SCHEMA INNODB_COLUMNS Table">
<code class="literal">
INNODB_COLUMNS
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="information-schema-innodb-datafiles-table.html" title="28.4.10 The INFORMATION_SCHEMA INNODB_DATAFILES Table">
<code class="literal">
INNODB_DATAFILES
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="information-schema-innodb-fields-table.html" title="28.4.11 The INFORMATION_SCHEMA INNODB_FIELDS Table">
<code class="literal">
INNODB_FIELDS
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="information-schema-innodb-foreign-table.html" title="28.4.12 The INFORMATION_SCHEMA INNODB_FOREIGN Table">
<code class="literal">
INNODB_FOREIGN
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="information-schema-innodb-foreign-cols-table.html" title="28.4.13 The INFORMATION_SCHEMA INNODB_FOREIGN_COLS Table">
<code class="literal">
INNODB_FOREIGN_COLS
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="information-schema-innodb-indexes-table.html" title="28.4.20 The INFORMATION_SCHEMA INNODB_INDEXES Table">
<code class="literal">
INNODB_INDEXES
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="information-schema-innodb-tables-table.html" title="28.4.23 The INFORMATION_SCHEMA INNODB_TABLES Table">
<code class="literal">
INNODB_TABLES
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="information-schema-innodb-tablespaces-table.html" title="28.4.24 The INFORMATION_SCHEMA INNODB_TABLESPACES Table">
<code class="literal">
INNODB_TABLESPACES
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="information-schema-innodb-tablespaces-brief-table.html" title="28.4.25 The INFORMATION_SCHEMA INNODB_TABLESPACES_BRIEF Table">
<code class="literal">
INNODB_TABLESPACES_BRIEF
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="information-schema-innodb-tablestats-table.html" title="28.4.26 The INFORMATION_SCHEMA INNODB_TABLESTATS View">
<code class="literal">
INNODB_TABLESTATS
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="information-schema-key-column-usage-table.html" title="28.3.16 The INFORMATION_SCHEMA KEY_COLUMN_USAGE Table">
<code class="literal">
KEY_COLUMN_USAGE
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
KEYWORDS
</code>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="information-schema-parameters-table.html" title="28.3.20 The INFORMATION_SCHEMA PARAMETERS Table">
<code class="literal">
PARAMETERS
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="information-schema-partitions-table.html" title="28.3.21 The INFORMATION_SCHEMA PARTITIONS Table">
<code class="literal">
PARTITIONS
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="information-schema-referential-constraints-table.html" title="28.3.25 The INFORMATION_SCHEMA REFERENTIAL_CONSTRAINTS Table">
<code class="literal">
REFERENTIAL_CONSTRAINTS
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="information-schema-resource-groups-table.html" title="28.3.26 The INFORMATION_SCHEMA RESOURCE_GROUPS Table">
<code class="literal">
RESOURCE_GROUPS
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="information-schema-routines-table.html" title="28.3.30 The INFORMATION_SCHEMA ROUTINES Table">
<code class="literal">
ROUTINES
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="information-schema-schemata-table.html" title="28.3.31 The INFORMATION_SCHEMA SCHEMATA Table">
<code class="literal">
SCHEMATA
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="information-schema-statistics-table.html" title="28.3.34 The INFORMATION_SCHEMA STATISTICS Table">
<code class="literal">
STATISTICS
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="information-schema-st-geometry-columns-table.html" title="28.3.35 The INFORMATION_SCHEMA ST_GEOMETRY_COLUMNS Table">
<code class="literal">
ST_GEOMETRY_COLUMNS
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="information-schema-st-spatial-reference-systems-table.html" title="28.3.36 The INFORMATION_SCHEMA ST_SPATIAL_REFERENCE_SYSTEMS Table">
<code class="literal">
ST_SPATIAL_REFERENCE_SYSTEMS
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="information-schema-tables-table.html" title="28.3.38 The INFORMATION_SCHEMA TABLES Table">
<code class="literal">
TABLES
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="information-schema-table-constraints-table.html" title="28.3.41 The INFORMATION_SCHEMA TABLE_CONSTRAINTS Table">
<code class="literal">
TABLE_CONSTRAINTS
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="information-schema-triggers-table.html" title="28.3.44 The INFORMATION_SCHEMA TRIGGERS Table">
<code class="literal">
TRIGGERS
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="information-schema-views-table.html" title="28.3.47 The INFORMATION_SCHEMA VIEWS Table">
<code class="literal">
VIEWS
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="information-schema-view-routine-usage-table.html" title="28.3.48 The INFORMATION_SCHEMA VIEW_ROUTINE_USAGE Table">
<code class="literal">
VIEW_ROUTINE_USAGE
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="information-schema-view-table-usage-table.html" title="28.3.49 The INFORMATION_SCHEMA VIEW_TABLE_USAGE Table">
<code class="literal">
VIEW_TABLE_USAGE
</code>
</a>
</p>
</li>
</ul>
</div>
<p>
Queries on those tables are now more efficient because they obtain
information from data dictionary tables rather than by other,
slower means. In particular, for each
<code class="literal">
INFORMATION_SCHEMA
</code>
table that is a view on data
dictionary tables:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
The server no longer must create a temporary table for each
query of the
<code class="literal">
INFORMATION_SCHEMA
</code>
table.
</p>
</li>
<li class="listitem">
<p>
When the underlying data dictionary tables store values
previously obtained by directory scans (for example, to
enumerate database names or table names within databases) or
file-opening operations (for example, to read information from
<code class="filename">
.frm
</code>
files),
<code class="literal">
INFORMATION_SCHEMA
</code>
queries for those values
now use table lookups instead. (Additionally, even for a
non-view
<code class="literal">
INFORMATION_SCHEMA
</code>
table, values
such as database and table names are retrieved by lookups from
the data dictionary and do not require directory or file
scans.)
</p>
</li>
<li class="listitem">
<p>
Indexes on the underlying data dictionary tables permit the
optimizer to construct efficient query execution plans,
something not true for the previous implementation that
processed the
<code class="literal">
INFORMATION_SCHEMA
</code>
table
using a temporary table per query.
</p>
</li>
</ul>
</div>
<p>
The preceding improvements also apply to
<a class="link" href="show.html" title="15.7.7 SHOW Statements">
<code class="literal">
SHOW
</code>
</a>
statements that display
information corresponding to the
<code class="literal">
INFORMATION_SCHEMA
</code>
tables that are views on
data dictionary tables. For example,
<a class="link" href="show-databases.html" title="15.7.7.15 SHOW DATABASES Statement">
<code class="literal">
SHOW
DATABASES
</code>
</a>
displays the same information as the
<a class="link" href="information-schema-schemata-table.html" title="28.3.31 The INFORMATION_SCHEMA SCHEMATA Table">
<code class="literal">
SCHEMATA
</code>
</a>
table.
</p>
<p>
In addition to the introduction of views on data dictionary
tables, table statistics contained in the
<a class="link" href="information-schema-statistics-table.html" title="28.3.34 The INFORMATION_SCHEMA STATISTICS Table">
<code class="literal">
STATISTICS
</code>
</a>
and
<a class="link" href="information-schema-tables-table.html" title="28.3.38 The INFORMATION_SCHEMA TABLES Table">
<code class="literal">
TABLES
</code>
</a>
tables is now cached to
improve
<a class="link" href="information-schema.html" title="Chapter 28 INFORMATION_SCHEMA Tables">
<code class="literal">
INFORMATION_SCHEMA
</code>
</a>
query
performance. The
<a class="link" href="server-system-variables.html#sysvar_information_schema_stats_expiry">
<code class="literal">
information_schema_stats_expiry
</code>
</a>
system variable defines the period of time before cached table
statistics expire. The default is 86400 seconds (24 hours). If
there are no cached statistics or statistics have expired,
statistics are retrieved from storage engine when querying table
statistics columns. To update cached values at any time for a
given table, use
<a class="link" href="analyze-table.html" title="15.7.3.1 ANALYZE TABLE Statement">
<code class="literal">
ANALYZE TABLE
</code>
</a>
</p>
<p>
<a class="link" href="server-system-variables.html#sysvar_information_schema_stats_expiry">
<code class="literal">
information_schema_stats_expiry
</code>
</a>
can be set to
<code class="literal">
0
</code>
to have
<a class="link" href="information-schema.html" title="Chapter 28 INFORMATION_SCHEMA Tables">
<code class="literal">
INFORMATION_SCHEMA
</code>
</a>
queries retrieve
the latest statistics directly from the storage engine, which is
not as fast as retrieving cached statistics.
</p>
<p>
For more information, see
<a class="xref" href="information-schema-optimization.html" title="10.2.3 Optimizing INFORMATION_SCHEMA Queries">
Section 10.2.3, “Optimizing INFORMATION_SCHEMA Queries”
</a>
.
</p>
<p>
<code class="literal">
INFORMATION_SCHEMA
</code>
tables in MySQL
8.4 are closely tied to the data dictionary,
resulting in several usage differences. See
<a class="xref" href="data-dictionary-usage-differences.html" title="16.7 Data Dictionary Usage Differences">
Section 16.7, “Data Dictionary Usage Differences”
</a>
.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/sys-statement-analysis.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="sys-statement-analysis">
</a>
30.4.3.35 The statement_analysis and x$statement_analysis Views
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045062229072">
</a>
<a class="indexterm" name="idm46045062227616">
</a>
<a class="indexterm" name="idm46045062226128">
</a>
<a class="indexterm" name="idm46045062224624">
</a>
<p>
These views list normalized statements with aggregated
statistics. The content mimics the MySQL Enterprise Monitor
Query Analysis view. By default, rows are sorted by descending
total latency.
</p>
<p>
The
<a class="link" href="sys-statement-analysis.html" title="30.4.3.35 The statement_analysis and x$statement_analysis Views">
<code class="literal">
statement_analysis
</code>
</a>
and
<a class="link" href="sys-statement-analysis.html" title="30.4.3.35 The statement_analysis and x$statement_analysis Views">
<code class="literal">
x$statement_analysis
</code>
</a>
views have
these columns:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<code class="literal">
query
</code>
</p>
<p>
The normalized statement string.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
db
</code>
</p>
<p>
The default database for the statement, or
<code class="literal">
NULL
</code>
if there is none.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
full_scan
</code>
</p>
<p>
The total number of full table scans performed by
occurrences of the statement.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
exec_count
</code>
</p>
<p>
The total number of times the statement has executed.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
err_count
</code>
</p>
<p>
The total number of errors produced by occurrences of the
statement.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
warn_count
</code>
</p>
<p>
The total number of warnings produced by occurrences of
the statement.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
total_latency
</code>
</p>
<p>
The total wait time of timed occurrences of the statement.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
max_latency
</code>
</p>
<p>
The maximum single wait time of timed occurrences of the
statement.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
avg_latency
</code>
</p>
<p>
The average wait time per timed occurrence of the
statement.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
lock_latency
</code>
</p>
<p>
The total time waiting for locks by timed occurrences of
the statement.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
cpu_latency
</code>
</p>
<p>
The time spent on CPU for the current thread.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
rows_sent
</code>
</p>
<p>
The total number of rows returned by occurrences of the
statement.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
rows_sent_avg
</code>
</p>
<p>
The average number of rows returned per occurrence of the
statement.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
rows_examined
</code>
</p>
<p>
The total number of rows read from storage engines by
occurrences of the statement.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
rows_examined_avg
</code>
</p>
<p>
The average number of rows read from storage engines per
occurrence of the statement.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
rows_affected
</code>
</p>
<p>
The total number of rows affected by occurrences of the
statement.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
rows_affected_avg
</code>
</p>
<p>
The average number of rows affected per occurrence of the
statement.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
tmp_tables
</code>
</p>
<p>
The total number of internal in-memory temporary tables
created by occurrences of the statement.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
tmp_disk_tables
</code>
</p>
<p>
The total number of internal on-disk temporary tables
created by occurrences of the statement.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
rows_sorted
</code>
</p>
<p>
The total number of rows sorted by occurrences of the
statement.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
sort_merge_passes
</code>
</p>
<p>
The total number of sort merge passes by occurrences of
the statement.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
max_controlled_memory
</code>
</p>
<p>
The maximum amount of controlled memory (bytes) used by
the statement.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
max_total_memory
</code>
</p>
<p>
The maximum amount of memory (bytes) used by the
statement.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
digest
</code>
</p>
<p>
The statement digest.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
first_seen
</code>
</p>
<p>
The time at which the statement was first seen.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
last_seen
</code>
</p>
<p>
The time at which the statement was most recently seen.
</p>
</li>
</ul>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/performance-schema-events-waits-current-table.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="performance-schema-events-waits-current-table">
</a>
29.12.4.1 The events_waits_current Table
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045073321552">
</a>
<a class="indexterm" name="idm46045073320048">
</a>
<p>
The
<a class="link" href="performance-schema-events-waits-current-table.html" title="29.12.4.1 The events_waits_current Table">
<code class="literal">
events_waits_current
</code>
</a>
table
contains current wait events. The table stores one row per
thread showing the current status of the thread's most recent
monitored wait event, so there is no system variable for
configuring the table size.
</p>
<p>
Of the tables that contain wait event rows,
<a class="link" href="performance-schema-events-waits-current-table.html" title="29.12.4.1 The events_waits_current Table">
<code class="literal">
events_waits_current
</code>
</a>
is the most
fundamental. Other tables that contain wait event rows are
logically derived from the current events. For example, the
<a class="link" href="performance-schema-events-waits-history-table.html" title="29.12.4.2 The events_waits_history Table">
<code class="literal">
events_waits_history
</code>
</a>
and
<a class="link" href="performance-schema-events-waits-history-long-table.html" title="29.12.4.3 The events_waits_history_long Table">
<code class="literal">
events_waits_history_long
</code>
</a>
tables
are collections of the most recent wait events that have
ended, up to a maximum number of rows per thread and globally
across all threads, respectively.
</p>
<p>
For more information about the relationship between the three
wait event tables, see
<a class="xref" href="performance-schema-event-tables.html" title="29.9 Performance Schema Tables for Current and Historical Events">
Section 29.9, “Performance Schema Tables for Current and Historical Events”
</a>
.
</p>
<p>
For information about configuring whether to collect wait
events, see
<a class="xref" href="performance-schema-wait-tables.html" title="29.12.4 Performance Schema Wait Event Tables">
Section 29.12.4, “Performance Schema Wait Event Tables”
</a>
.
</p>
<p>
The
<a class="link" href="performance-schema-events-waits-current-table.html" title="29.12.4.1 The events_waits_current Table">
<code class="literal">
events_waits_current
</code>
</a>
table
has these columns:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<code class="literal">
THREAD_ID
</code>
,
<code class="literal">
EVENT_ID
</code>
</p>
<p>
The thread associated with the event and the thread
current event number when the event starts. The
<code class="literal">
THREAD_ID
</code>
and
<code class="literal">
EVENT_ID
</code>
values taken together uniquely
identify the row. No two rows have the same pair of
values.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
END_EVENT_ID
</code>
</p>
<p>
This column is set to
<code class="literal">
NULL
</code>
when the
event starts and updated to the thread current event
number when the event ends.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
EVENT_NAME
</code>
</p>
<p>
The name of the instrument that produced the event. This
is a
<code class="literal">
NAME
</code>
value from the
<a class="link" href="performance-schema-setup-instruments-table.html" title="29.12.2.3 The setup_instruments Table">
<code class="literal">
setup_instruments
</code>
</a>
table.
Instrument names may have multiple parts and form a
hierarchy, as discussed in
<a class="xref" href="performance-schema-instrument-naming.html" title="29.6 Performance Schema Instrument Naming Conventions">
Section 29.6, “Performance Schema Instrument Naming Conventions”
</a>
.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
SOURCE
</code>
</p>
<p>
The name of the source file containing the instrumented
code that produced the event and the line number in the
file at which the instrumentation occurs. This enables you
to check the source to determine exactly what code is
involved. For example, if a mutex or lock is being
blocked, you can check the context in which this occurs.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
TIMER_START
</code>
,
<code class="literal">
TIMER_END
</code>
,
<code class="literal">
TIMER_WAIT
</code>
</p>
<p>
Timing information for the event. The unit for these
values is picoseconds (trillionths of a second). The
<code class="literal">
TIMER_START
</code>
and
<code class="literal">
TIMER_END
</code>
values indicate when event
timing started and ended.
<code class="literal">
TIMER_WAIT
</code>
is
the event elapsed time (duration).
</p>
<p>
If an event has not finished,
<code class="literal">
TIMER_END
</code>
is the current timer value and
<code class="literal">
TIMER_WAIT
</code>
is the time elapsed so far
(
<code class="literal">
TIMER_END
</code>
−
<code class="literal">
TIMER_START
</code>
).
</p>
<p>
If an event is produced from an instrument that has
<code class="literal">
TIMED = NO
</code>
, timing information is not
collected, and
<code class="literal">
TIMER_START
</code>
,
<code class="literal">
TIMER_END
</code>
, and
<code class="literal">
TIMER_WAIT
</code>
are all
<code class="literal">
NULL
</code>
.
</p>
<p>
For discussion of picoseconds as the unit for event times
and factors that affect time values, see
<a class="xref" href="performance-schema-timing.html" title="29.4.1 Performance Schema Event Timing">
Section 29.4.1, “Performance Schema Event Timing”
</a>
.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
SPINS
</code>
</p>
<p>
For a mutex, the number of spin rounds. If the value is
<code class="literal">
NULL
</code>
, the code does not use spin rounds
or spinning is not instrumented.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
OBJECT_SCHEMA
</code>
,
<code class="literal">
OBJECT_NAME
</code>
,
<code class="literal">
OBJECT_TYPE
</code>
,
<code class="literal">
OBJECT_INSTANCE_BEGIN
</code>
</p>
<p>
These columns identify the object
<span class="quote">
“
<span class="quote">
being acted
on.
</span>
”
</span>
What that means depends on the object type.
</p>
<p>
For a synchronization object (
<code class="literal">
cond
</code>
,
<code class="literal">
mutex
</code>
,
<code class="literal">
rwlock
</code>
):
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
<code class="literal">
OBJECT_SCHEMA
</code>
,
<code class="literal">
OBJECT_NAME
</code>
, and
<code class="literal">
OBJECT_TYPE
</code>
are
<code class="literal">
NULL
</code>
.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
OBJECT_INSTANCE_BEGIN
</code>
is the
address of the synchronization object in memory.
</p>
</li>
</ul>
</div>
<p>
For a file I/O object:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
<code class="literal">
OBJECT_SCHEMA
</code>
is
<code class="literal">
NULL
</code>
.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
OBJECT_NAME
</code>
is the file name.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
OBJECT_TYPE
</code>
is
<code class="literal">
FILE
</code>
.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
OBJECT_INSTANCE_BEGIN
</code>
is an address
in memory.
</p>
</li>
</ul>
</div>
<p>
For a socket object:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
<code class="literal">
OBJECT_NAME
</code>
is the
<code class="literal">
IP:PORT
</code>
value for the socket.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
OBJECT_INSTANCE_BEGIN
</code>
is an address
in memory.
</p>
</li>
</ul>
</div>
<p>
For a table I/O object:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
<code class="literal">
OBJECT_SCHEMA
</code>
is the name of the
schema that contains the table.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
OBJECT_NAME
</code>
is the table name.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
OBJECT_TYPE
</code>
is
<code class="literal">
TABLE
</code>
for a persistent base table
or
<code class="literal">
TEMPORARY TABLE
</code>
for a temporary
table.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
OBJECT_INSTANCE_BEGIN
</code>
is an address
in memory.
</p>
</li>
</ul>
</div>
<p>
An
<code class="literal">
OBJECT_INSTANCE_BEGIN
</code>
value itself
has no meaning, except that different values indicate
different objects.
<code class="literal">
OBJECT_INSTANCE_BEGIN
</code>
can be used for
debugging. For example, it can be used with
<code class="literal">
GROUP
BY OBJECT_INSTANCE_BEGIN
</code>
to see whether the load
on 1,000 mutexes (that protect, say, 1,000 pages or blocks
of data) is spread evenly or just hitting a few
bottlenecks. This can help you correlate with other
sources of information if you see the same object address
in a log file or another debugging or performance tool.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
INDEX_NAME
</code>
</p>
<p>
The name of the index used.
<code class="literal">
PRIMARY
</code>
indicates the table primary index.
<code class="literal">
NULL
</code>
means that no index was used.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
NESTING_EVENT_ID
</code>
</p>
<p>
The
<code class="literal">
EVENT_ID
</code>
value of the event within
which this event is nested.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
NESTING_EVENT_TYPE
</code>
</p>
<p>
The nesting event type. The value is
<code class="literal">
TRANSACTION
</code>
,
<code class="literal">
STATEMENT
</code>
,
<code class="literal">
STAGE
</code>
, or
<code class="literal">
WAIT
</code>
.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
OPERATION
</code>
</p>
<p>
The type of operation performed, such as
<code class="literal">
lock
</code>
,
<code class="literal">
read
</code>
, or
<code class="literal">
write
</code>
.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
NUMBER_OF_BYTES
</code>
</p>
<p>
The number of bytes read or written by the operation. For
table I/O waits (events for the
<code class="literal">
wait/io/table/sql/handler
</code>
instrument),
<code class="literal">
NUMBER_OF_BYTES
</code>
indicates the number of
rows. If the value is greater than 1, the event is for a
batch I/O operation. The following discussion describes
the difference between exclusively single-row reporting
and reporting that reflects batch I/O.
</p>
<p>
MySQL executes joins using a nested-loop implementation.
The job of the Performance Schema instrumentation is to
provide row count and accumulated execution time per table
in the join. Assume a join query of the following form
that is executed using a table join order of
<code class="literal">
t1
</code>
,
<code class="literal">
t2
</code>
,
<code class="literal">
t3
</code>
:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa69207370"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SELECT</span> <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span> <span class="token keyword">FROM</span> t1 <span class="token keyword">JOIN</span> t2 <span class="token keyword">ON</span> <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span> <span class="token keyword">JOIN</span> t3 <span class="token keyword">ON</span> <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span></code></pre>
</div>
<p>
Table
<span class="quote">
“
<span class="quote">
fanout
</span>
”
</span>
is the increase or decrease in
number of rows from adding a table during join processing.
If the fanout for table
<code class="literal">
t3
</code>
is greater
than 1, the majority of row-fetch operations are for that
table. Suppose that the join accesses 10 rows from
<code class="literal">
t1
</code>
, 20 rows from
<code class="literal">
t2
</code>
per row from
<code class="literal">
t1
</code>
, and 30 rows from
<code class="literal">
t3
</code>
per row of table
<code class="literal">
t2
</code>
. With single-row reporting, the
total number of instrumented operations is:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-clike"><div class="docs-select-all right" id="sa48013162"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-clike"><span class="token number">10</span> <span class="token operator">+</span> <span class="token punctuation">(</span><span class="token number">10</span> <span class="token operator">*</span> <span class="token number">20</span><span class="token punctuation">)</span> <span class="token operator">+</span> <span class="token punctuation">(</span><span class="token number">10</span> <span class="token operator">*</span> <span class="token number">20</span> <span class="token operator">*</span> <span class="token number">30</span><span class="token punctuation">)</span> <span class="token operator">=</span> <span class="token number">6210</span></code></pre>
</div>
<p>
A significant reduction in the number of instrumented
operations is achievable by aggregating them per scan
(that is, per unique combination of rows from
<code class="literal">
t1
</code>
and
<code class="literal">
t2
</code>
). With
batch I/O reporting, the Performance Schema produces an
event for each scan of the innermost table
<code class="literal">
t3
</code>
rather than for each row, and the
number of instrumented row operations reduces to:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-clike"><div class="docs-select-all right" id="sa89972022"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-clike"><span class="token number">10</span> <span class="token operator">+</span> <span class="token punctuation">(</span><span class="token number">10</span> <span class="token operator">*</span> <span class="token number">20</span><span class="token punctuation">)</span> <span class="token operator">+</span> <span class="token punctuation">(</span><span class="token number">10</span> <span class="token operator">*</span> <span class="token number">20</span><span class="token punctuation">)</span> <span class="token operator">=</span> <span class="token number">410</span></code></pre>
</div>
<p>
That is a reduction of 93%, illustrating how the
batch-reporting strategy significantly reduces Performance
Schema overhead for table I/O by reducing the number of
reporting calls. The tradeoff is lesser accuracy for event
timing. Rather than time for an individual row operation
as in per-row reporting, timing for batch I/O includes
time spent for operations such as join buffering,
aggregation, and returning rows to the client.
</p>
<p>
For batch I/O reporting to occur, these conditions must be
true:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
Query execution accesses the innermost table of a
query block (for a single-table query, that table
counts as innermost)
</p>
</li>
<li class="listitem">
<p>
Query execution does not request a single row from the
table (so, for example,
<a class="link" href="explain-output.html#jointype_eq_ref">
<code class="literal">
eq_ref
</code>
</a>
access
prevents use of batch reporting)
</p>
</li>
<li class="listitem">
<p>
Query execution does not evaluate a subquery
containing table access for the table
</p>
</li>
</ul>
</div>
</li>
<li class="listitem">
<p>
<code class="literal">
FLAGS
</code>
</p>
<p>
Reserved for future use.
</p>
</li>
</ul>
</div>
<p>
The
<a class="link" href="performance-schema-events-waits-current-table.html" title="29.12.4.1 The events_waits_current Table">
<code class="literal">
events_waits_current
</code>
</a>
table
has these indexes:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
Primary key on (
<code class="literal">
THREAD_ID
</code>
,
<code class="literal">
EVENT_ID
</code>
)
</p>
</li>
</ul>
</div>
<p>
<a class="link" href="truncate-table.html" title="15.1.37 TRUNCATE TABLE Statement">
<code class="literal">
TRUNCATE TABLE
</code>
</a>
is permitted for
the
<a class="link" href="performance-schema-events-waits-current-table.html" title="29.12.4.1 The events_waits_current Table">
<code class="literal">
events_waits_current
</code>
</a>
table.
It removes the rows.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/getting-mysql.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="getting-mysql">
</a>
2.1.3 How to Get MySQL
</h3>
</div>
</div>
</div>
<a class="indexterm" name="idm46045332951456">
</a>
<a class="indexterm" name="idm46045332950384">
</a>
<a class="indexterm" name="idm46045332949312">
</a>
<a class="indexterm" name="idm46045332947824">
</a>
<a class="indexterm" name="idm46045332946752">
</a>
<a class="indexterm" name="idm46045332945680">
</a>
<p>
Check our downloads page at
<a class="ulink" href="https://dev.mysql.com/downloads/" target="_top">
https://dev.mysql.com/downloads/
</a>
for information about the current version of MySQL and for
downloading instructions.
</p>
<p>
For RPM-based Linux platforms that use Yum as their package
management system, MySQL can be installed using the
<a class="ulink" href="https://dev.mysql.com/downloads/repo/yum/" target="_top">
MySQL Yum
Repository
</a>
. See
<a class="xref" href="linux-installation-yum-repo.html" title="2.5.1 Installing MySQL on Linux Using the MySQL Yum Repository">
Section 2.5.1, “Installing MySQL on Linux Using the MySQL Yum Repository”
</a>
for details.
</p>
<p>
For Debian-based Linux platforms, MySQL can be installed using the
<a class="ulink" href="https://dev.mysql.com/downloads/repo/apt/" target="_top">
MySQL APT
Repository
</a>
. See
<a class="xref" href="linux-installation-apt-repo.html" title="2.5.2 Installing MySQL on Linux Using the MySQL APT Repository">
Section 2.5.2, “Installing MySQL on Linux Using the MySQL APT Repository”
</a>
for details.
</p>
<p>
For SUSE Linux Enterprise Server (SLES) platforms, MySQL can be
installed using the
<a class="ulink" href="https://dev.mysql.com/downloads/repo/suse/" target="_top">
MySQL SLES
Repository
</a>
. See
<a class="xref" href="linux-installation-sles-repo.html" title="2.5.3 Using the MySQL SLES Repository">
Section 2.5.3, “Using the MySQL SLES Repository”
</a>
for details.
</p>
<p>
To obtain the latest development source, see
<a class="xref" href="installing-development-tree.html" title="2.8.5 Installing MySQL Using a Development Source Tree">
Section 2.8.5, “Installing MySQL Using a Development Source Tree”
</a>
.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/which-version.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="which-version">
</a>
2.1.2 Which MySQL Version and Distribution to Install
</h3>
</div>
</div>
</div>
<a class="indexterm" name="idm46045332999712">
</a>
<a class="indexterm" name="idm46045332998256">
</a>
<p>
When preparing to install MySQL, decide which version and
distribution format (binary or source) to use.
</p>
<a class="indexterm" name="idm46045332996240">
</a>
<a class="indexterm" name="idm46045332995152">
</a>
<a class="indexterm" name="idm46045332994064">
</a>
<a class="indexterm" name="idm46045332992992">
</a>
<a class="indexterm" name="idm46045332991504">
</a>
<p>
First, decide whether to install from an
<a class="link" href="glossary.html#glos_lts_series" title="LTS Series">
LTS series
</a>
like MySQL
8.4, or install from an
<a class="link" href="glossary.html#glos_innovation_series" title="Innovation Series">
Innovation series
</a>
like MySQL 9.1. Both tracks include bug
fixes while innovation releases includes the latest new features
and changes. For additional details, see
<a class="xref" href="mysql-releases.html" title="1.3 MySQL Releases: Innovation and LTS">
Section 1.3, “MySQL Releases: Innovation and LTS”
</a>
.
</p>
<a class="indexterm" name="idm46045332987040">
</a>
<a class="indexterm" name="idm46045332985552">
</a>
<a class="indexterm" name="idm46045332984064">
</a>
<a class="indexterm" name="idm46045332982560">
</a>
<a class="indexterm" name="idm46045332981104">
</a>
<a class="indexterm" name="idm46045332979616">
</a>
<p>
The naming scheme in MySQL 8.4 uses release names
that consist of three numbers and an optional suffix (for example,
<span class="bold">
<strong>
mysql-8.4.0
</strong>
</span>
). The numbers within
the release name are interpreted as follows:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
The first number (
<span class="bold">
<strong>
8
</strong>
</span>
) is the
major version number.
</p>
</li>
<li class="listitem">
<p>
The second number (
<span class="bold">
<strong>
4
</strong>
</span>
) is the
minor version number. The minor version number does not change
for an
<a class="link" href="glossary.html#glos_lts_series" title="LTS Series">
LTS series
</a>
, but
it does change for an
<a class="link" href="glossary.html#glos_innovation_series" title="Innovation Series">
Innovation
series
</a>
.
</p>
</li>
<li class="listitem">
<p>
The third number (
<span class="bold">
<strong>
0
</strong>
</span>
) is the
version number within an LTS series. This is incremented for
each new LTS release, but is likely always 0 for innovation
releases.
</p>
</li>
</ul>
</div>
<p>
After choosing which MySQL version to install, decide which
distribution format to install for your operating system. For most
use cases, a binary distribution is the right choice. Binary
distributions are available in native format for many platforms,
such as RPM packages for Linux or DMG packages for macOS.
Distributions are also available in more generic formats such as
Zip archives or compressed
<span class="command">
<strong>
tar
</strong>
</span>
files. On
Windows, you might use an MSI to install a binary distribution.
</p>
<p>
Under some circumstances, it may be preferable to install MySQL
from a source distribution:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
You want to install MySQL at some explicit location. The
standard binary distributions are ready to run at any
installation location, but you might require even more
flexibility to place MySQL components where you want.
</p>
</li>
<li class="listitem">
<p>
You want to configure
<a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
<span class="command">
<strong>
mysqld
</strong>
</span>
</a>
with features
that might not be included in the standard binary
distributions. Here is a list of the most common extra options
used to ensure feature availability:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
<a class="link" href="source-configuration-options.html#option_cmake_with_libwrap">
<code class="option">
-DWITH_LIBWRAP=1
</code>
</a>
for TCP
wrappers support.
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="source-configuration-options.html#option_cmake_with_zlib">
<code class="option">
-DWITH_ZLIB={system|bundled}
</code>
</a>
for features that depend on compression
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="source-configuration-options.html#option_cmake_with_debug">
<code class="option">
-DWITH_DEBUG=1
</code>
</a>
for debugging
support
</p>
</li>
</ul>
</div>
<p>
For additional information, see
<a class="xref" href="source-configuration-options.html" title="2.8.7 MySQL Source-Configuration Options">
Section 2.8.7, “MySQL Source-Configuration Options”
</a>
.
</p>
</li>
<li class="listitem">
<p>
You want to configure
<a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
<span class="command">
<strong>
mysqld
</strong>
</span>
</a>
without some
features that are included in the standard binary
distributions.
</p>
</li>
<li class="listitem">
<p>
You want to read or modify the C and C++ code that makes up
MySQL. For this purpose, obtain a source distribution.
</p>
</li>
<li class="listitem">
<p>
Source distributions contain more tests and examples than
binary distributions.
</p>
</li>
</ul>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/thread-pool-tuning.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="thread-pool-tuning">
</a>
7.6.3.4 Thread Pool Tuning
</h4>
</div>
</div>
</div>
<p>
This section provides guidelines on determining the best
configuration for thread pool performance, as measured using a
metric such as transactions per second.
</p>
<p>
Of chief importance is the number of thread groups in the thread
pool, which can be set on server startup using the
<a class="link" href="server-system-variables.html#sysvar_thread_pool_size">
<code class="option">
--thread-pool-size
</code>
</a>
option; this
cannot be changed at runtime. Recommended values for this option
depend on whether the primary storage engine in use is
<a class="link" href="innodb-storage-engine.html" title="Chapter 17 The InnoDB Storage Engine">
<code class="literal">
InnoDB
</code>
</a>
or
<a class="link" href="myisam-storage-engine.html" title="18.2 The MyISAM Storage Engine">
<code class="literal">
MyISAM
</code>
</a>
:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
If the primary storage engine is
<code class="literal">
InnoDB
</code>
,
the recommended value for the thread pool size is the number
of physical cores available on the host machine, up to a
maximum of 512.
</p>
</li>
<li class="listitem">
<p>
If the primary storage engine is
<code class="literal">
MyISAM
</code>
,
the thread pool size should be fairly low. Optimal
performance is often seen with values from 4 to 8. Higher
values tend to have a slightly negative but not dramatic
impact on performance.
</p>
</li>
</ul>
</div>
<p>
The upper limit on the number of concurrent transactions that
can be processed by the thread pool plugin is determined by the
value of
<a class="link" href="server-system-variables.html#sysvar_thread_pool_max_transactions_limit">
<code class="literal">
thread_pool_max_transactions_limit
</code>
</a>
.
The recommendation initial setting for this system variable is
the number of physical cores times 32. You may need to adjust
the value from this starting point to suit a given workload; a
reasonable upper bound for this value is the maximum number of
concurrent connections expected; the value of the
<a class="link" href="server-status-variables.html#statvar_Max_used_connections">
<code class="literal">
Max_used_connections
</code>
</a>
status
variable can serve as a guide to determining this. A good way to
proceed is to start with
<code class="literal">
thread_pool_max_transactions_limit
</code>
set to
this value, then adjust it downwards while observing the effect
on throughput.
</p>
<p>
The maximum number of query threads permitted in a thread group
is determined by the value of
<a class="link" href="server-system-variables.html#sysvar_thread_pool_query_threads_per_group">
<code class="literal">
thread_pool_query_threads_per_group
</code>
</a>
,
which can be adjusted at runtime. The product of this value and
the thread pool size is approximately equal to the total number
of threads available to process queries. Obtaining the best
performance usually means striking the proper balance for your
application between
<code class="literal">
thread_pool_query_threads_per_group
</code>
and the
thread pool size. Greater values for
<code class="literal">
thread_pool_query_threads_per_group
</code>
value
make it less likely that all the threads in the thread group
simultaneously execute long running queries while blocking
shorter ones when the workload includes both long and short
running queries. You should bear in mind that the overhead of
the connection polling operation for each thread group increases
when using smaller values for the thread pool size with larger
values for
<code class="literal">
thread_pool_query_threads_per_group
</code>
. For this
reason, we recommend a starting value of 2 for
<code class="literal">
thread_pool_query_threads_per_group
</code>
; setting
this variable to a lower value usually does not offer any
performance benefit.
</p>
<p>
For best performance under normal conditions, we also recommend
that you set
<a class="link" href="server-system-variables.html#sysvar_thread_pool_algorithm">
<code class="literal">
thread_pool_algorithm
</code>
</a>
to 1 for
high concurrency.
</p>
<p>
In addition, the value of the
<a class="link" href="server-system-variables.html#sysvar_thread_pool_stall_limit">
<code class="literal">
thread_pool_stall_limit
</code>
</a>
system
variable determines the handling of blocked and long-running
statements. If all calls blocking the MySQL Server were reported
to the thread pool, it would always know when execution threads
are blocked, but this may not always be true. For example,
blocks could occur in code that has not been instrumented with
thread pool callbacks. For such cases, the thread pool must be
able to identify threads that appear to be blocked. This is done
by means of a timeout determined by the value of
<code class="literal">
thread_pool_stall_limit
</code>
, which ensures that
the server does not become completely blocked. The value of
<code class="literal">
thread_pool_stall_limit
</code>
represents a number
of 10-millisecond intervals, so that
<code class="literal">
600
</code>
(the
maximum) represents 6 seconds.
</p>
<p>
<a class="link" href="server-system-variables.html#sysvar_thread_pool_stall_limit">
<code class="literal">
thread_pool_stall_limit
</code>
</a>
also
enables the thread pool to handle long-running statements. If a
long-running statement were permitted to block a thread group,
all other connections assigned to the group would be blocked and
unable to start execution until the long-running statement
completed. In the worst case, this could take hours or even
days.
</p>
<p>
The value of
<a class="link" href="server-system-variables.html#sysvar_thread_pool_stall_limit">
<code class="literal">
thread_pool_stall_limit
</code>
</a>
should
be chosen such that statements that execute longer than its
value are considered stalled. Stalled statements generate a lot
of extra overhead since they involve extra context switches and
in some cases even extra thread creations. On the other hand,
setting the
<a class="link" href="server-system-variables.html#sysvar_thread_pool_stall_limit">
<code class="literal">
thread_pool_stall_limit
</code>
</a>
parameter too high means that long-running statements block a
number of short-running statements for longer than necessary.
Short wait values permit threads to start more quickly. Short
values are also better for avoiding deadlock situations. Long
wait values are useful for workloads that include long-running
statements, to avoid starting too many new statements while the
current ones execute.
</p>
<p>
Suppose a server executes a workload where 99.9% of the
statements complete within 100ms even when the server is loaded,
and the remaining statements take between 100ms and 2 hours
fairly evenly spread. In this case, it would make sense to set
<a class="link" href="server-system-variables.html#sysvar_thread_pool_stall_limit">
<code class="literal">
thread_pool_stall_limit
</code>
</a>
to 10
(10 × 10ms = 100ms). The default value of 6 (60ms)
is suitable for servers that primarily execute very simple
statements.
</p>
<p>
The
<a class="link" href="server-system-variables.html#sysvar_thread_pool_stall_limit">
<code class="literal">
thread_pool_stall_limit
</code>
</a>
parameter can be changed at runtime to enable you to strike a
balance appropriate for the server work load. Assuming that the
<a class="link" href="performance-schema-tp-thread-group-stats-table.html" title="29.12.16.3 The tp_thread_group_stats Table">
<code class="literal">
tp_thread_group_stats
</code>
</a>
table is
enabled, you can use the following query to determine the
fraction of executed statements that stalled:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa95901415"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SELECT</span> <span class="token function">SUM</span><span class="token punctuation">(</span>STALLED_QUERIES_EXECUTED<span class="token punctuation">)</span> <span class="token operator">/</span> <span class="token function">SUM</span><span class="token punctuation">(</span>QUERIES_EXECUTED<span class="token punctuation">)</span>
<span class="token keyword">FROM</span> performance_schema<span class="token punctuation">.</span>tp_thread_group_stats<span class="token punctuation">;</span></code></pre>
</div>
<p>
This number should be as low as possible. To decrease the
likelihood of statements stalling, increase the value of
<a class="link" href="server-system-variables.html#sysvar_thread_pool_stall_limit">
<code class="literal">
thread_pool_stall_limit
</code>
</a>
.
</p>
<p>
When a statement arrives, what is the maximum time it can be
delayed before it actually starts executing? Suppose that the
following conditions apply:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
There are 200 statements queued in the low-priority queue.
</p>
</li>
<li class="listitem">
<p>
There are 10 statements queued in the high-priority queue.
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="server-system-variables.html#sysvar_thread_pool_prio_kickup_timer">
<code class="literal">
thread_pool_prio_kickup_timer
</code>
</a>
is set to 10000 (10 seconds).
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="server-system-variables.html#sysvar_thread_pool_stall_limit">
<code class="literal">
thread_pool_stall_limit
</code>
</a>
is
set to 100 (1 second).
</p>
</li>
</ul>
</div>
<p>
In the worst case, the 10 high-priority statements represent 10
transactions that continue executing for a long time. Thus, in
the worst case, no statements can be moved to the high-priority
queue because it always already contains statements awaiting
execution. After 10 seconds, the new statement is eligible to be
moved to the high-priority queue. However, before it can be
moved, all the statements before it must be moved as well. This
could take another 2 seconds because a maximum of 100 statements
per second are moved to the high-priority queue. Now when the
statement reaches the high-priority queue, there could
potentially be many long-running statements ahead of it. In the
worst case, every one of those becomes stalled and 1 second is
required for each statement before the next statement is
retrieved from the high-priority queue. Thus, in this scenario,
it takes 222 seconds before the new statement starts executing.
</p>
<p>
This example shows a worst case for an application. How to
handle it depends on the application. If the application has
high requirements for the response time, it should most likely
throttle users at a higher level itself. Otherwise, it can use
the thread pool configuration parameters to set some kind of a
maximum waiting time.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/mysql-cluster-ndbinfo-config-params.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="mysql-cluster-ndbinfo-config-params">
</a>
25.6.17.11 The ndbinfo config_params Table
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045090192976">
</a>
<p>
The
<code class="literal">
config_params
</code>
table is a static table
which provides the names and internal ID numbers of and other
information about NDB Cluster configuration parameters. This
table can also be used in conjunction with the
<a class="link" href="mysql-cluster-ndbinfo-config-values.html" title="25.6.17.12 The ndbinfo config_values Table">
<code class="literal">
config_values
</code>
</a>
table for
obtaining realtime information about node configuration
parameters.
</p>
<p>
The
<code class="literal">
config_params
</code>
table contains the
following columns:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<code class="literal">
param_number
</code>
</p>
<p>
The parameter's internal ID number
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
param_name
</code>
</p>
<p>
The name of the parameter
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
param_description
</code>
</p>
<p>
A brief description of the parameter
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
param_type
</code>
</p>
<p>
The parameter's data type
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
param_default
</code>
</p>
<p>
The parameter's default value, if any
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
param_min
</code>
</p>
<p>
The parameter's maximum value, if any
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
param_max
</code>
</p>
<p>
The parameter's minimum value, if any
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
param_mandatory
</code>
</p>
<p>
This is 1 if the parameter is required, otherwise 0
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
param_status
</code>
</p>
<p>
Currently unused
</p>
</li>
</ul>
</div>
<h5>
<a name="idm46045090169952">
</a>
Notes
</h5>
<p>
This table is read-only.
</p>
<p>
Although this is a static table, its content can vary between
NDB Cluster installations, since supported parameters can vary
due to differences between software releases, cluster hardware
configurations, and other factors.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/innodb-benefits.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="innodb-benefits">
</a>
17.1.1 Benefits of Using InnoDB Tables
</h3>
</div>
</div>
</div>
<p>
<code class="literal">
InnoDB
</code>
tables have the following benefits:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
If the server unexpectedly exits because of a hardware or
software issue, regardless of what was happening in the
database at the time, you don't need to do anything special
after restarting the database.
<code class="literal">
InnoDB
</code>
crash
recovery automatically finalizes changes that were committed
before the time of the crash, and undoes changes that were in
process but not committed, permitting you to restart and
continue from where you left off. See
<a class="xref" href="innodb-recovery.html" title="17.18.2 InnoDB Recovery">
Section 17.18.2, “InnoDB Recovery”
</a>
.
</p>
</li>
<li class="listitem">
<p>
The
<code class="literal">
InnoDB
</code>
storage engine maintains its own
buffer pool that caches table and index data in main memory as
data is accessed. Frequently used data is processed directly
from memory. This cache applies to many types of information
and speeds up processing. On dedicated database servers, up to
80% of physical memory is often assigned to the buffer pool.
See
<a class="xref" href="innodb-buffer-pool.html" title="17.5.1 Buffer Pool">
Section 17.5.1, “Buffer Pool”
</a>
.
</p>
</li>
<li class="listitem">
<p>
If you split up related data into different tables, you can
set up foreign keys that enforce referential integrity. See
<a class="xref" href="create-table-foreign-keys.html" title="15.1.20.5 FOREIGN KEY Constraints">
Section 15.1.20.5, “FOREIGN KEY Constraints”
</a>
.
</p>
</li>
<li class="listitem">
<p>
If data becomes corrupted on disk or in memory, a checksum
mechanism alerts you to the bogus data before you use it. The
<a class="link" href="innodb-parameters.html#sysvar_innodb_checksum_algorithm">
<code class="literal">
innodb_checksum_algorithm
</code>
</a>
variable defines the checksum algorithm used by
<code class="literal">
InnoDB
</code>
.
</p>
</li>
<li class="listitem">
<p>
When you design a database with appropriate primary key
columns for each table, operations involving those columns are
automatically optimized. It is very fast to reference the
primary key columns in
<a class="link" href="select.html" title="15.2.13 SELECT Statement">
<code class="literal">
WHERE
</code>
</a>
clauses,
<a class="link" href="select.html" title="15.2.13 SELECT Statement">
<code class="literal">
ORDER
BY
</code>
</a>
clauses,
<a class="link" href="select.html" title="15.2.13 SELECT Statement">
<code class="literal">
GROUP BY
</code>
</a>
clauses, and join operations. See
<a class="xref" href="innodb-index-types.html" title="17.6.2.1 Clustered and Secondary Indexes">
Section 17.6.2.1, “Clustered and Secondary Indexes”
</a>
.
</p>
</li>
<li class="listitem">
<p>
Inserts, updates, and deletes are optimized by an automatic
mechanism called change buffering.
<code class="literal">
InnoDB
</code>
not only allows concurrent read and write access to the same
table, it caches changed data to streamline disk I/O. See
<a class="xref" href="innodb-change-buffer.html" title="17.5.2 Change Buffer">
Section 17.5.2, “Change Buffer”
</a>
.
</p>
</li>
<li class="listitem">
<p>
Performance benefits are not limited to large tables with
long-running queries. When the same rows are accessed over and
over from a table, the Adaptive Hash Index takes over to make
these lookups even faster, as if they came out of a hash
table. See
<a class="xref" href="innodb-adaptive-hash.html" title="17.5.3 Adaptive Hash Index">
Section 17.5.3, “Adaptive Hash Index”
</a>
.
</p>
</li>
<li class="listitem">
<p>
You can compress tables and associated indexes. See
<a class="xref" href="innodb-compression.html" title="17.9 InnoDB Table and Page Compression">
Section 17.9, “InnoDB Table and Page Compression”
</a>
.
</p>
</li>
<li class="listitem">
<p>
You can encrypt your data. See
<a class="xref" href="innodb-data-encryption.html" title="17.13 InnoDB Data-at-Rest Encryption">
Section 17.13, “InnoDB Data-at-Rest Encryption”
</a>
.
</p>
</li>
<li class="listitem">
<p>
You can create and drop indexes and perform other DDL
operations with much less impact on performance and
availability. See
<a class="xref" href="innodb-online-ddl-operations.html" title="17.12.1 Online DDL Operations">
Section 17.12.1, “Online DDL Operations”
</a>
.
</p>
</li>
<li class="listitem">
<p>
Truncating a file-per-table tablespace is very fast and can
free up disk space for the operating system to reuse rather
than only
<code class="literal">
InnoDB
</code>
. See
<a class="xref" href="innodb-file-per-table-tablespaces.html" title="17.6.3.2 File-Per-Table Tablespaces">
Section 17.6.3.2, “File-Per-Table Tablespaces”
</a>
.
</p>
</li>
<li class="listitem">
<p>
The storage layout for table data is more efficient for
<a class="link" href="blob.html" title="13.3.4 The BLOB and TEXT Types">
<code class="literal">
BLOB
</code>
</a>
and long text fields, with
the
<code class="literal">
DYNAMIC
</code>
row format. See
<a class="xref" href="innodb-row-format.html" title="17.10 InnoDB Row Formats">
Section 17.10, “InnoDB Row Formats”
</a>
.
</p>
</li>
<li class="listitem">
<p>
You can monitor the internal workings of the storage engine by
querying
<code class="literal">
INFORMATION_SCHEMA
</code>
tables. See
<a class="xref" href="innodb-information-schema.html" title="17.15 InnoDB INFORMATION_SCHEMA Tables">
Section 17.15, “InnoDB INFORMATION_SCHEMA Tables”
</a>
.
</p>
</li>
<li class="listitem">
<p>
You can monitor the performance details of the storage engine
by querying Performance Schema tables. See
<a class="xref" href="innodb-performance-schema.html" title="17.16 InnoDB Integration with MySQL Performance Schema">
Section 17.16, “InnoDB Integration with MySQL Performance Schema”
</a>
.
</p>
</li>
<li class="listitem">
<p>
You can mix
<code class="literal">
InnoDB
</code>
tables with tables from
other MySQL storage engines, even within the same statement.
For example, you can use a join operation to combine data from
<code class="literal">
InnoDB
</code>
and
<a class="link" href="memory-storage-engine.html" title="18.3 The MEMORY Storage Engine">
<code class="literal">
MEMORY
</code>
</a>
tables in a single query.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
InnoDB
</code>
has been designed for CPU efficiency
and maximum performance when processing large data volumes.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
InnoDB
</code>
tables can handle large quantities
of data, even on operating systems where file size is limited
to 2GB.
</p>
</li>
</ul>
</div>
<p>
For
<code class="literal">
InnoDB
</code>
-specific tuning techniques you can
apply to your MySQL server and application code, see
<a class="xref" href="optimizing-innodb.html" title="10.5 Optimizing for InnoDB Tables">
Section 10.5, “Optimizing for InnoDB Tables”
</a>
.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/alter-database.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="alter-database">
</a>
15.1.2 ALTER DATABASE Statement
</h3>
</div>
</div>
</div>
<a class="indexterm" name="idm46045190070192">
</a>
<a class="indexterm" name="idm46045190069152">
</a>
<a class="indexterm" name="idm46045190068080">
</a>
<a class="indexterm" name="idm46045190066592">
</a>
<a class="indexterm" name="idm46045190065104">
</a>
<a class="indexterm" name="idm46045190063616">
</a>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa72909117"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">ALTER</span> {<span class="token keyword">DATABASE</span> <span class="token operator">|</span> <span class="token keyword">SCHEMA</span>} <span class="token punctuation">[</span><em class="replaceable">db_name</em><span class="token punctuation">]</span>
<em class="replaceable">alter_option</em> <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span>
<em class="replaceable">alter_option</em>: {
<span class="token punctuation">[</span><span class="token keyword">DEFAULT</span><span class="token punctuation">]</span> <span class="token keyword">CHARACTER</span> <span class="token keyword">SET</span> <span class="token punctuation">[</span><span class="token operator">=</span><span class="token punctuation">]</span> <em class="replaceable">charset_name</em>
<span class="token operator">|</span> <span class="token punctuation">[</span><span class="token keyword">DEFAULT</span><span class="token punctuation">]</span> <span class="token keyword">COLLATE</span> <span class="token punctuation">[</span><span class="token operator">=</span><span class="token punctuation">]</span> <em class="replaceable">collation_name</em>
<span class="token operator">|</span> <span class="token punctuation">[</span><span class="token keyword">DEFAULT</span><span class="token punctuation">]</span> <span class="token keyword">ENCRYPTION</span> <span class="token punctuation">[</span><span class="token operator">=</span><span class="token punctuation">]</span> {<span class="token string">'Y'</span> <span class="token operator">|</span> <span class="token string">'N'</span>}
<span class="token operator">|</span> <span class="token keyword">READ</span> <span class="token keyword">ONLY</span> <span class="token punctuation">[</span><span class="token operator">=</span><span class="token punctuation">]</span> {<span class="token keyword">DEFAULT</span> <span class="token operator">|</span> <span class="token number">0</span> <span class="token operator">|</span> <span class="token number">1</span>}
}</code></pre>
</div>
<p>
<a class="link" href="alter-database.html" title="15.1.2 ALTER DATABASE Statement">
<code class="literal">
ALTER DATABASE
</code>
</a>
enables you to
change the overall characteristics of a database. These
characteristics are stored in the data dictionary. This statement
requires the
<a class="link" href="privileges-provided.html#priv_alter">
<code class="literal">
ALTER
</code>
</a>
privilege on the
database.
<a class="link" href="alter-database.html" title="15.1.2 ALTER DATABASE Statement">
<code class="literal">
ALTER
SCHEMA
</code>
</a>
is a synonym for
<a class="link" href="alter-database.html" title="15.1.2 ALTER DATABASE Statement">
<code class="literal">
ALTER
DATABASE
</code>
</a>
.
</p>
<p>
If the database name is omitted, the statement applies to the
default database. In that case, an error occurs if there is no
default database.
</p>
<p>
For any
<em class="replaceable">
<code>
alter_option
</code>
</em>
omitted from the
statement, the database retains its current option value, with the
exception that changing the character set may change the collation
and vice versa.
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<a class="xref" href="alter-database.html#alter-database-charset" title="Character Set and Collation Options">
Character Set and Collation Options
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="alter-database.html#alter-database-encryption" title="Encryption Option">
Encryption Option
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="alter-database.html#alter-database-read-only" title="Read Only Option">
Read Only Option
</a>
</p>
</li>
</ul>
</div>
<h4>
<a name="alter-database-charset">
</a>
Character Set and Collation Options
</h4>
<p>
The
<code class="literal">
CHARACTER SET
</code>
option changes the default
database character set. The
<code class="literal">
COLLATE
</code>
option
changes the default database collation. For information about
character set and collation names, see
<a class="xref" href="charset.html" title="Chapter 12 Character Sets, Collations, Unicode">
Chapter 12,
<i>
Character Sets, Collations, Unicode
</i>
</a>
.
</p>
<p>
To see the available character sets and collations, use the
<a class="link" href="show-character-set.html" title="15.7.7.4 SHOW CHARACTER SET Statement">
<code class="literal">
SHOW CHARACTER SET
</code>
</a>
and
<a class="link" href="show-collation.html" title="15.7.7.5 SHOW COLLATION Statement">
<code class="literal">
SHOW COLLATION
</code>
</a>
statements,
respectively. See
<a class="xref" href="show-character-set.html" title="15.7.7.4 SHOW CHARACTER SET Statement">
Section 15.7.7.4, “SHOW CHARACTER SET Statement”
</a>
, and
<a class="xref" href="show-collation.html" title="15.7.7.5 SHOW COLLATION Statement">
Section 15.7.7.5, “SHOW COLLATION Statement”
</a>
.
</p>
<p>
A stored routine that uses the database defaults when the routine
is created includes those defaults as part of its definition. (In
a stored routine, variables with character data types use the
database defaults if the character set or collation are not
specified explicitly. See
<a class="xref" href="create-procedure.html" title="15.1.17 CREATE PROCEDURE and CREATE FUNCTION Statements">
Section 15.1.17, “CREATE PROCEDURE and CREATE FUNCTION Statements”
</a>
.) If
you change the default character set or collation for a database,
any stored routines that are to use the new defaults must be
dropped and recreated.
</p>
<h4>
<a name="alter-database-encryption">
</a>
Encryption Option
</h4>
<p>
The
<code class="literal">
ENCRYPTION
</code>
option, defines the default
database encryption, which is inherited by tables created in the
database. The permitted values are
<code class="literal">
'Y'
</code>
(encryption enabled) and
<code class="literal">
'N'
</code>
(encryption
disabled).
</p>
<p>
The
<code class="literal">
mysql
</code>
system schema cannot be set to
default encryption. The existing tables within it are part of the
general
<code class="literal">
mysql
</code>
tablespace, which may be
encrypted. The
<code class="literal">
information_schema
</code>
contains only
views. It is not possible to create any tables within it. There is
nothing on the disk to encrypt. All tables in the
<code class="literal">
performance_schema
</code>
use the
<a class="link" href="performance-schema.html" title="Chapter 29 MySQL Performance Schema">
<code class="literal">
PERFORMANCE_SCHEMA
</code>
</a>
engine, which is
purely in-memory. It is not possible to create any other tables in
it. There is nothing on the disk to encrypt.
</p>
<p>
Only newly created tables inherit the default database encryption.
For existing tables associated with the database, their encryption
remains unchanged. If the
<a class="link" href="server-system-variables.html#sysvar_table_encryption_privilege_check">
<code class="literal">
table_encryption_privilege_check
</code>
</a>
system variable is enabled, the
<a class="link" href="privileges-provided.html#priv_table-encryption-admin">
<code class="literal">
TABLE_ENCRYPTION_ADMIN
</code>
</a>
privilege is
required to specify a default encryption setting that differs from
the value of the
<a class="link" href="server-system-variables.html#sysvar_default_table_encryption">
<code class="literal">
default_table_encryption
</code>
</a>
system
variable. For more information, see
<a class="xref" href="innodb-data-encryption.html#innodb-schema-tablespace-encryption-default" title="Defining an Encryption Default for Schemas and General Tablespaces">
Defining an Encryption Default for Schemas and General Tablespaces
</a>
.
</p>
<h4>
<a name="alter-database-read-only">
</a>
Read Only Option
</h4>
<a class="indexterm" name="idm46045190019984">
</a>
<p>
The
<code class="literal">
READ ONLY
</code>
option controls whether to permit
modification of the database and objects within it. The permitted
values are
<code class="literal">
DEFAULT
</code>
or
<code class="literal">
0
</code>
(not
read only) and
<code class="literal">
1
</code>
(read only). This option is
useful for database migration because a database for which
<code class="literal">
READ ONLY
</code>
is enabled can be migrated to another
MySQL instance without concern that the database might be changed
during the operation.
</p>
<p>
With NDB Cluster, making a database read only on one
<a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
<span class="command">
<strong>
mysqld
</strong>
</span>
</a>
server is synchronized to other
<a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
<span class="command">
<strong>
mysqld
</strong>
</span>
</a>
servers in the same cluster, so that the
database becomes read only on all
<a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
<span class="command">
<strong>
mysqld
</strong>
</span>
</a>
servers.
</p>
<p>
The
<code class="literal">
READ ONLY
</code>
option, if enabled, is displayed
in the
<code class="literal">
INFORMATION_SCHEMA
</code>
<a class="link" href="information-schema-schemata-extensions-table.html" title="28.3.32 The INFORMATION_SCHEMA SCHEMATA_EXTENSIONS Table">
<code class="literal">
SCHEMATA_EXTENSIONS
</code>
</a>
table. See
<a class="xref" href="information-schema-schemata-extensions-table.html" title="28.3.32 The INFORMATION_SCHEMA SCHEMATA_EXTENSIONS Table">
Section 28.3.32, “The INFORMATION_SCHEMA SCHEMATA_EXTENSIONS Table”
</a>
.
</p>
<a class="indexterm" name="idm46045190005888">
</a>
<p>
The
<code class="literal">
READ ONLY
</code>
option cannot be enabled for
these system schemas:
<code class="literal">
mysql
</code>
,
<code class="literal">
information_schema
</code>
,
<code class="literal">
performance_schema
</code>
.
</p>
<p>
In
<a class="link" href="alter-database.html" title="15.1.2 ALTER DATABASE Statement">
<code class="literal">
ALTER DATABASE
</code>
</a>
statements, the
<code class="literal">
READ ONLY
</code>
option interacts with other instances
of itself and with other options as follows:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
An error occurs if multiple instances of
<code class="literal">
READ
ONLY
</code>
conflict (for example,
<code class="literal">
READ ONLY = 1
READ ONLY = 0
</code>
).
</p>
</li>
<li class="listitem">
<p>
An
<a class="link" href="alter-database.html" title="15.1.2 ALTER DATABASE Statement">
<code class="literal">
ALTER DATABASE
</code>
</a>
statement
that contains only (nonconflicting)
<code class="literal">
READ
ONLY
</code>
options is permitted even for a read-only
database.
</p>
</li>
<li class="listitem">
<p>
A mix of (nonconflicting)
<code class="literal">
READ ONLY
</code>
options
with other options is permitted if the read-only state of the
database either before or after the statement permits
modifications. If the read-only state both before and after
prohibits changes, an error occurs.
</p>
<p>
This statement succeeds whether or not the database is read
only:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa8316771"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">ALTER</span> <span class="token keyword">DATABASE</span> mydb <span class="token keyword">READ</span> <span class="token keyword">ONLY</span> <span class="token operator">=</span> <span class="token number">0</span> <span class="token keyword">DEFAULT</span> <span class="token keyword">COLLATE</span> utf8mb4_bin<span class="token punctuation">;</span></code></pre>
</div>
<p>
This statement succeeds if the database is not read only, but
fails if it is already read only:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa9562597"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">ALTER</span> <span class="token keyword">DATABASE</span> mydb <span class="token keyword">READ</span> <span class="token keyword">ONLY</span> <span class="token operator">=</span> <span class="token number">1</span> <span class="token keyword">DEFAULT</span> <span class="token keyword">COLLATE</span> utf8mb4_bin<span class="token punctuation">;</span></code></pre>
</div>
</li>
</ul>
</div>
<p>
Enabling
<code class="literal">
READ ONLY
</code>
affects all users of the
database, with these exceptions that are not subject to read-only
checks:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
Statements executed by the server as part of server
initialization, restart, upgrade, or replication.
</p>
</li>
<li class="listitem">
<p>
Statements in a file named at server startup by the
<a class="link" href="server-system-variables.html#sysvar_init_file">
<code class="literal">
init_file
</code>
</a>
system variable.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
TEMPORARY
</code>
tables; it is possible to create,
alter, drop, and write to
<code class="literal">
TEMPORARY
</code>
tables
in a read-only database.
</p>
</li>
<li class="listitem">
<p>
NDB Cluster non-SQL inserts and updates.
</p>
</li>
</ul>
</div>
<p>
Other than for the excepted operations just listed, enabling
<code class="literal">
READ ONLY
</code>
prohibits write operations to the
database and its objects, including their definitions, data, and
metadata. The following list details affected SQL statements and
operations:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
The database itself:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
<a class="link" href="create-database.html" title="15.1.12 CREATE DATABASE Statement">
<code class="literal">
CREATE DATABASE
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="alter-database.html" title="15.1.2 ALTER DATABASE Statement">
<code class="literal">
ALTER DATABASE
</code>
</a>
(except to
change the
<code class="literal">
READ ONLY
</code>
option)
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="drop-database.html" title="15.1.24 DROP DATABASE Statement">
<code class="literal">
DROP DATABASE
</code>
</a>
</p>
</li>
</ul>
</div>
</li>
<li class="listitem">
<p>
Views:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
<a class="link" href="create-view.html" title="15.1.23 CREATE VIEW Statement">
<code class="literal">
CREATE VIEW
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="alter-view.html" title="15.1.11 ALTER VIEW Statement">
<code class="literal">
ALTER VIEW
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="drop-view.html" title="15.1.35 DROP VIEW Statement">
<code class="literal">
DROP VIEW
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
Selecting from views that invoke functions with side
effects.
</p>
</li>
<li class="listitem">
<p>
Updating updatable views.
</p>
</li>
<li class="listitem">
<p>
Statements that create or drop objects in a writable
database are rejected if they affect metadata of a view in
a read-only database (for example, by making the view
valid or invalid).
</p>
</li>
</ul>
</div>
</li>
<li class="listitem">
<p>
Stored routines:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
<a class="link" href="create-procedure.html" title="15.1.17 CREATE PROCEDURE and CREATE FUNCTION Statements">
<code class="literal">
CREATE PROCEDURE
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="drop-procedure.html" title="15.1.29 DROP PROCEDURE and DROP FUNCTION Statements">
<code class="literal">
DROP PROCEDURE
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="call.html" title="15.2.1 CALL Statement">
<code class="literal">
CALL
</code>
</a>
(of procedures with
side effects)
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="create-function.html" title="15.1.14 CREATE FUNCTION Statement">
<code class="literal">
CREATE FUNCTION
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="drop-function.html" title="15.1.26 DROP FUNCTION Statement">
<code class="literal">
DROP FUNCTION
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="select.html" title="15.2.13 SELECT Statement">
<code class="literal">
SELECT
</code>
</a>
(of functions with
side effects)
</p>
</li>
<li class="listitem">
<p>
For procedures and functions, read-only checks follow
prelocking behavior. For
<a class="link" href="call.html" title="15.2.1 CALL Statement">
<code class="literal">
CALL
</code>
</a>
statements, read-only
checks are done on a per-statement basis, so if some
conditionally executed statement writing to a read-only
database does not actually execute, the call still
succeeds. On the other hand, for a function called within
a
<a class="link" href="select.html" title="15.2.13 SELECT Statement">
<code class="literal">
SELECT
</code>
</a>
, execution of the
function body happens in prelocked mode. As long as a some
statement within the function writes to a read-only
database, execution of the function fails with an error
regardless of whether the statement actually executes.
</p>
</li>
</ul>
</div>
</li>
<li class="listitem">
<p>
Triggers:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
<a class="link" href="create-trigger.html" title="15.1.22 CREATE TRIGGER Statement">
<code class="literal">
CREATE TRIGGER
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="drop-trigger.html" title="15.1.34 DROP TRIGGER Statement">
<code class="literal">
DROP TRIGGER
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
Trigger invocation.
</p>
</li>
</ul>
</div>
</li>
<li class="listitem">
<p>
Events:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
<a class="link" href="create-event.html" title="15.1.13 CREATE EVENT Statement">
<code class="literal">
CREATE EVENT
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="alter-event.html" title="15.1.3 ALTER EVENT Statement">
<code class="literal">
ALTER EVENT
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="drop-event.html" title="15.1.25 DROP EVENT Statement">
<code class="literal">
DROP EVENT
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
Event execution:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: square; ">
<li class="listitem">
<p>
Executing an event in the database fails because that
would change the last-execution timestamp, which is
event metadata stored in the data dictionary. Failure
of event execution also has the effect of causing the
event scheduler to stop.
</p>
</li>
<li class="listitem">
<p>
If an event writes to an object in a read-only
database, execution of the event fails with an error,
but the event scheduler is not stopped.
</p>
</li>
</ul>
</div>
</li>
</ul>
</div>
</li>
<li class="listitem">
<p>
Tables:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
<a class="link" href="create-table.html" title="15.1.20 CREATE TABLE Statement">
<code class="literal">
CREATE TABLE
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement">
<code class="literal">
ALTER TABLE
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="create-index.html" title="15.1.15 CREATE INDEX Statement">
<code class="literal">
CREATE INDEX
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="drop-index.html" title="15.1.27 DROP INDEX Statement">
<code class="literal">
DROP INDEX
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="rename-table.html" title="15.1.36 RENAME TABLE Statement">
<code class="literal">
RENAME TABLE
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="truncate-table.html" title="15.1.37 TRUNCATE TABLE Statement">
<code class="literal">
TRUNCATE TABLE
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="drop-table.html" title="15.1.32 DROP TABLE Statement">
<code class="literal">
DROP TABLE
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="delete.html" title="15.2.2 DELETE Statement">
<code class="literal">
DELETE
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="insert.html" title="15.2.7 INSERT Statement">
<code class="literal">
INSERT
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="import-table.html" title="15.2.6 IMPORT TABLE Statement">
<code class="literal">
IMPORT TABLE
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="load-data.html" title="15.2.9 LOAD DATA Statement">
<code class="literal">
LOAD DATA
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="load-xml.html" title="15.2.10 LOAD XML Statement">
<code class="literal">
LOAD XML
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="replace.html" title="15.2.12 REPLACE Statement">
<code class="literal">
REPLACE
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="update.html" title="15.2.17 UPDATE Statement">
<code class="literal">
UPDATE
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
For cascading foreign keys where the child table is in a
read-only database, updates and deletes on the parent are
rejected even if the child table is not directly affected.
</p>
</li>
<li class="listitem">
<p>
For a
<code class="literal">
MERGE
</code>
table such as
<code class="literal">
CREATE TABLE s1.t(i int) ENGINE MERGE UNION
(s2.t, s3.t), INSERT_METHOD=...
</code>
, the following
behavior applies:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: square; ">
<li class="listitem">
<p>
Inserting into the
<code class="literal">
MERGE
</code>
table
(
<code class="literal">
INSERT into s1.t
</code>
) fails if at
least one of
<code class="literal">
s1
</code>
,
<code class="literal">
s2
</code>
,
<code class="literal">
s3
</code>
is read
only, regardless of insert method. The insert is
refused even if it would actually end up in a writable
table.
</p>
</li>
<li class="listitem">
<p>
Dropping the
<code class="literal">
MERGE
</code>
table
(
<code class="literal">
DROP TABLE s1.t
</code>
) succeeds as long
as
<code class="literal">
s1
</code>
is not read only. It is
permitted to drop a
<code class="literal">
MERGE
</code>
table
that refers to a read-only database.
</p>
</li>
</ul>
</div>
</li>
</ul>
</div>
</li>
</ul>
</div>
<p>
An
<a class="link" href="alter-database.html" title="15.1.2 ALTER DATABASE Statement">
<code class="literal">
ALTER DATABASE
</code>
</a>
statement blocks
until all concurrent transactions that have already accessed an
object in the database being altered have committed. Conversely, a
write transaction accessing an object in a database being altered
in a concurrent
<a class="link" href="alter-database.html" title="15.1.2 ALTER DATABASE Statement">
<code class="literal">
ALTER DATABASE
</code>
</a>
blocks until the
<a class="link" href="alter-database.html" title="15.1.2 ALTER DATABASE Statement">
<code class="literal">
ALTER DATABASE
</code>
</a>
has
committed.
</p>
<p>
If the Clone plugin is used to clone a local or remote data
directory, the databases in the clone retain the read-only state
they had in the source data directory. The read-only state does
not affect the cloning process itself. If it is not desirable to
have the same database read-only state in the clone, the option
must be changed explicitly for the clone after the cloning process
has finished, using
<a class="link" href="alter-database.html" title="15.1.2 ALTER DATABASE Statement">
<code class="literal">
ALTER DATABASE
</code>
</a>
operations on the clone.
</p>
<p>
When cloning from a donor to a recipient, if the recipient has a
user database that is read only, cloning fails with an error
message. Cloning may be retried after making the database
writable.
</p>
<p>
<code class="literal">
READ ONLY
</code>
is permitted for
<a class="link" href="alter-database.html" title="15.1.2 ALTER DATABASE Statement">
<code class="literal">
ALTER DATABASE
</code>
</a>
, but not for
<a class="link" href="create-database.html" title="15.1.12 CREATE DATABASE Statement">
<code class="literal">
CREATE DATABASE
</code>
</a>
. However, for a
read-only database, the statement produced by
<a class="link" href="show-create-database.html" title="15.7.7.7 SHOW CREATE DATABASE Statement">
<code class="literal">
SHOW CREATE DATABASE
</code>
</a>
does include
<code class="literal">
READ ONLY=1
</code>
within a comment to indicate its
read-only status:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa67267831"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">ALTER</span> <span class="token keyword">DATABASE</span> mydb <span class="token keyword">READ</span> <span class="token keyword">ONLY</span> <span class="token operator">=</span> <span class="token number">1</span><span class="token punctuation">;</span>
<span class="token prompt">mysql></span> <span class="token keyword">SHOW</span> <span class="token keyword">CREATE</span> <span class="token keyword">DATABASE</span> mydb\G
<span class="token output"><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span> 1. row <span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span>
Database<span class="token punctuation">:</span> mydb
Create Database<span class="token punctuation">:</span> CREATE DATABASE `mydb`
/<span class="token punctuation">*</span>!40100 DEFAULT CHARACTER SET utf8mb4
COLLATE utf8mb4_0900_ai_ci <span class="token punctuation">*</span>/
/<span class="token punctuation">*</span>!80016 DEFAULT ENCRYPTION='N' <span class="token punctuation">*</span>/
/<span class="token punctuation">*</span> READ ONLY = 1 <span class="token punctuation">*</span>/</span></code></pre>
</div>
<p>
If the server executes a
<a class="link" href="create-database.html" title="15.1.12 CREATE DATABASE Statement">
<code class="literal">
CREATE
DATABASE
</code>
</a>
statement containing such a comment, the server
ignores the comment and the
<code class="literal">
READ ONLY
</code>
option is
not processed. This has implications for
<a class="link" href="mysqldump.html" title="6.5.4 mysqldump — A Database Backup Program">
<span class="command">
<strong>
mysqldump
</strong>
</span>
</a>
, which uses
<a class="link" href="show-create-database.html" title="15.7.7.7 SHOW CREATE DATABASE Statement">
<code class="literal">
SHOW
CREATE DATABASE
</code>
</a>
to produce
<a class="link" href="create-database.html" title="15.1.12 CREATE DATABASE Statement">
<code class="literal">
CREATE
DATABASE
</code>
</a>
statements in dump output:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
In a dump file, the
<a class="link" href="create-database.html" title="15.1.12 CREATE DATABASE Statement">
<code class="literal">
CREATE
DATABASE
</code>
</a>
statement for a read-only database contains
the commented
<code class="literal">
READ ONLY
</code>
option.
</p>
</li>
<li class="listitem">
<p>
The dump file can be restored as usual, but because the server
ignores the commented
<code class="literal">
READ ONLY
</code>
option, the
restored database is
<span class="emphasis">
<em>
not
</em>
</span>
read only. If
the database is to be read only after being restored, you must
execute
<a class="link" href="alter-database.html" title="15.1.2 ALTER DATABASE Statement">
<code class="literal">
ALTER DATABASE
</code>
</a>
manually
to make it so.
</p>
</li>
</ul>
</div>
<p>
Suppose that
<code class="literal">
mydb
</code>
is read only and you dump it
as follows:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-terminal"><div class="docs-select-all right" id="sa20385081"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-terminal"><span class="token prompt">$> </span><span class="token command">mysqldump</span> <span class="token property">--databases</span> mydb > mydb<span class="token punctuation">.</span>sql</code></pre>
</div>
<p>
A restore operation later must be followed by
<a class="link" href="alter-database.html" title="15.1.2 ALTER DATABASE Statement">
<code class="literal">
ALTER DATABASE
</code>
</a>
if
<code class="literal">
mydb
</code>
should still be read only:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-terminal"><div class="docs-select-all right" id="sa38204086"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-terminal"><span class="token prompt">$> </span><span class="token command">mysql</span>
<span class="token prompt">mysql></span><span class="token command"> SOURCE</span> mydb<span class="token punctuation">.</span>sql<span class="token punctuation">;</span>
<span class="token prompt">mysql></span><span class="token command"> ALTER</span> DATABASE mydb READ ONLY = 1<span class="token punctuation">;</span></code></pre>
</div>
<p>
MySQL Enterprise Backup is not subject to this issue. It backs up and restores a
read-only database like any other, but enables the
<code class="literal">
READ
ONLY
</code>
option at restore time if it was enabled at backup
time.
</p>
<p>
<a class="link" href="alter-database.html" title="15.1.2 ALTER DATABASE Statement">
<code class="literal">
ALTER DATABASE
</code>
</a>
is written to the
binary log, so a change to the
<code class="literal">
READ ONLY
</code>
option
on a replication source server also affects replicas. To prevent
this from happening, binary logging must be disabled prior to
execution of the
<a class="link" href="alter-database.html" title="15.1.2 ALTER DATABASE Statement">
<code class="literal">
ALTER DATABASE
</code>
</a>
statement. For example, to prepare for migrating a database
without affecting replicas, perform these operations:
</p>
<div class="orderedlist">
<ol class="orderedlist" type="1">
<li class="listitem">
<p>
Within a single session, disable binary logging and enable
<code class="literal">
READ ONLY
</code>
for the database:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa50424908"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SET</span> sql_log_bin <span class="token operator">=</span> <span class="token keyword">OFF</span><span class="token punctuation">;</span>
<span class="token prompt">mysql></span> <span class="token keyword">ALTER</span> <span class="token keyword">DATABASE</span> mydb <span class="token keyword">READ</span> <span class="token keyword">ONLY</span> <span class="token operator">=</span> <span class="token number">1</span><span class="token punctuation">;</span></code></pre>
</div>
</li>
<li class="listitem">
<p>
Dump the database, for example, with
<a class="link" href="mysqldump.html" title="6.5.4 mysqldump — A Database Backup Program">
<span class="command">
<strong>
mysqldump
</strong>
</span>
</a>
:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-terminal"><div class="docs-select-all right" id="sa39855320"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-terminal"><span class="token prompt">$> </span><span class="token command">mysqldump</span> <span class="token property">--databases</span> mydb > mydb<span class="token punctuation">.</span>sql</code></pre>
</div>
</li>
<li class="listitem">
<p>
Within a single session, disable binary logging and disable
<code class="literal">
READ ONLY
</code>
for the database:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa85436538"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SET</span> sql_log_bin <span class="token operator">=</span> <span class="token keyword">OFF</span><span class="token punctuation">;</span>
<span class="token prompt">mysql></span> <span class="token keyword">ALTER</span> <span class="token keyword">DATABASE</span> mydb <span class="token keyword">READ</span> <span class="token keyword">ONLY</span> <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span></code></pre>
</div>
</li>
</ol>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/performance-schema-optimization.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="performance-schema-optimization">
</a>
10.2.4 Optimizing Performance Schema Queries
</h3>
</div>
</div>
</div>
<a class="indexterm" name="idm46045227708448">
</a>
<a class="indexterm" name="idm46045227706944">
</a>
<p>
Applications that monitor databases may make frequent use of
Performance Schema tables. To write queries for these tables
most efficiently, take advantage of their indexes. For example,
include a
<code class="literal">
WHERE
</code>
clause that restricts
retrieved rows based on comparison to specific values in an
indexed column.
</p>
<p>
Most Performance Schema tables have indexes. Tables that do not
are those that normally contain few rows or are unlikely to be
queried frequently. Performance Schema indexes give the
optimizer access to execution plans other than full table scans.
These indexes also improve performance for related objects, such
as
<a class="link" href="sys-schema.html" title="Chapter 30 MySQL sys Schema">
<code class="literal">
sys
</code>
</a>
schema views that use those
tables.
</p>
<p>
To see whether a given Performance Schema table has indexes and
what they are, use
<a class="link" href="show-index.html" title="15.7.7.23 SHOW INDEX Statement">
<code class="literal">
SHOW INDEX
</code>
</a>
or
<a class="link" href="show-create-table.html" title="15.7.7.11 SHOW CREATE TABLE Statement">
<code class="literal">
SHOW CREATE TABLE
</code>
</a>
:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa2690056"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SHOW</span> <span class="token keyword">INDEX</span> <span class="token keyword">FROM</span> performance_schema<span class="token punctuation">.</span>accounts\G
<span class="token output"><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span> 1. row <span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span>
Table<span class="token punctuation">:</span> accounts
Non_unique<span class="token punctuation">:</span> 0
Key_name<span class="token punctuation">:</span> ACCOUNT
Seq_in_index<span class="token punctuation">:</span> 1
Column_name<span class="token punctuation">:</span> USER
Collation<span class="token punctuation">:</span> NULL
Cardinality<span class="token punctuation">:</span> NULL
Sub_part<span class="token punctuation">:</span> NULL
Packed<span class="token punctuation">:</span> NULL
Null<span class="token punctuation">:</span> YES
Index_type<span class="token punctuation">:</span> HASH
Comment<span class="token punctuation">:</span>
Index_comment<span class="token punctuation">:</span>
Visible<span class="token punctuation">:</span> YES
<span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span> 2. row <span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span>
Table<span class="token punctuation">:</span> accounts
Non_unique<span class="token punctuation">:</span> 0
Key_name<span class="token punctuation">:</span> ACCOUNT
Seq_in_index<span class="token punctuation">:</span> 2
Column_name<span class="token punctuation">:</span> HOST
Collation<span class="token punctuation">:</span> NULL
Cardinality<span class="token punctuation">:</span> NULL
Sub_part<span class="token punctuation">:</span> NULL
Packed<span class="token punctuation">:</span> NULL
Null<span class="token punctuation">:</span> YES
Index_type<span class="token punctuation">:</span> HASH
Comment<span class="token punctuation">:</span>
Index_comment<span class="token punctuation">:</span>
Visible<span class="token punctuation">:</span> YES
</span>
<span class="token prompt">mysql></span> <span class="token keyword">SHOW</span> <span class="token keyword">CREATE</span> <span class="token keyword">TABLE</span> performance_schema<span class="token punctuation">.</span>rwlock_instances\G
<span class="token output"><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span> 1. row <span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span>
Table<span class="token punctuation">:</span> rwlock_instances
Create Table<span class="token punctuation">:</span> CREATE TABLE `rwlock_instances` (
`NAME` varchar(128) NOT NULL,
`OBJECT_INSTANCE_BEGIN` bigint(20) unsigned NOT NULL,
`WRITE_LOCKED_BY_THREAD_ID` bigint(20) unsigned DEFAULT NULL,
`READ_LOCKED_BY_COUNT` int(10) unsigned NOT NULL,
PRIMARY KEY (`OBJECT_INSTANCE_BEGIN`),
KEY `NAME` (`NAME`),
KEY `WRITE_LOCKED_BY_THREAD_ID` (`WRITE_LOCKED_BY_THREAD_ID`)
) ENGINE=PERFORMANCE_SCHEMA DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci</span></code></pre>
</div>
<p>
To see the execution plan for a Performance Schema query and
whether it uses any indexes, use
<a class="link" href="explain.html" title="15.8.2 EXPLAIN Statement">
<code class="literal">
EXPLAIN
</code>
</a>
:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa2406345"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">EXPLAIN</span> <span class="token keyword">SELECT</span> <span class="token operator">*</span> <span class="token keyword">FROM</span> performance_schema<span class="token punctuation">.</span>accounts
<span class="token keyword">WHERE</span> <span class="token punctuation">(</span><span class="token keyword">USER</span><span class="token punctuation">,</span><span class="token keyword">HOST</span><span class="token punctuation">)</span> <span class="token operator">=</span> <span class="token punctuation">(</span><span class="token string">'root'</span><span class="token punctuation">,</span><span class="token string">'localhost'</span><span class="token punctuation">)</span>\G
<span class="token output"><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span> 1. row <span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span>
id<span class="token punctuation">:</span> 1
select_type<span class="token punctuation">:</span> SIMPLE
table<span class="token punctuation">:</span> accounts
partitions<span class="token punctuation">:</span> NULL
type<span class="token punctuation">:</span> const
possible_keys<span class="token punctuation">:</span> ACCOUNT
key<span class="token punctuation">:</span> ACCOUNT
key_len<span class="token punctuation">:</span> 278
ref<span class="token punctuation">:</span> const,const
rows<span class="token punctuation">:</span> 1
filtered<span class="token punctuation">:</span> 100.00
Extra<span class="token punctuation">:</span> NULL</span></code></pre>
</div>
<p>
The
<a class="link" href="explain.html" title="15.8.2 EXPLAIN Statement">
<code class="literal">
EXPLAIN
</code>
</a>
output indicates that
the optimizer uses the
<a class="link" href="performance-schema-accounts-table.html" title="29.12.8.1 The accounts Table">
<code class="literal">
accounts
</code>
</a>
table
<code class="literal">
ACCOUNT
</code>
index that comprises the
<code class="literal">
USER
</code>
and
<code class="literal">
HOST
</code>
columns.
</p>
<p>
Performance Schema indexes are virtual: They are a construct of
the Performance Schema storage engine and use no memory or disk
storage. The Performance Schema reports index information to the
optimizer so that it can construct efficient execution plans.
The Performance Schema in turn uses optimizer information about
what to look for (for example, a particular key value), so that
it can perform efficient lookups without building actual index
structures. This implementation provides two important benefits:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
It entirely avoids the maintenance cost normally incurred
for tables that undergo frequent updates.
</p>
</li>
<li class="listitem">
<p>
It reduces at an early stage of query execution the amount
of data retrieved. For conditions on the indexed columns,
the Performance Schema efficiently returns only table rows
that satisfy the query conditions. Without an index, the
Performance Schema would return all rows in the table,
requiring that the optimizer later evaluate the conditions
against each row to produce the final result.
</p>
</li>
</ul>
</div>
<p>
Performance Schema indexes are predefined and cannot be dropped,
added, or altered.
</p>
<p>
Performance Schema indexes are similar to hash indexes. For
example:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
They are used only for equality comparisons that use the
<code class="literal">
=
</code>
or
<code class="literal">
<=>
</code>
operators.
</p>
</li>
<li class="listitem">
<p>
They are unordered. If a query result must have specific row
ordering characteristics, include an
<code class="literal">
ORDER
BY
</code>
clause.
</p>
</li>
</ul>
</div>
<p>
For additional information about hash indexes, see
<a class="xref" href="index-btree-hash.html" title="10.3.9 Comparison of B-Tree and Hash Indexes">
Section 10.3.9, “Comparison of B-Tree and Hash Indexes”
</a>
.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/mysql-cluster-online-add-node-remarks.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="mysql-cluster-online-add-node-remarks">
</a>
25.6.7.1 Adding NDB Cluster Data Nodes Online: General Issues
</h4>
</div>
</div>
</div>
<p>
This section provides general information about the behavior of
and current limitations in adding NDB Cluster nodes online.
</p>
<p>
<b>
Redistribution of Data.
</b>
The ability to add new nodes online includes a means to
reorganize
<a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4">
<code class="literal">
NDBCLUSTER
</code>
</a>
table data
and indexes so that they are distributed across all data
nodes, including the new ones, by means of the
<a class="link" href="alter-table-partition-operations.html" title="15.1.9.1 ALTER TABLE Partition Operations">
<code class="literal">
ALTER
TABLE ... REORGANIZE PARTITION
</code>
</a>
statement. Table
reorganization of both in-memory and Disk Data tables is
supported. This redistribution does not currently include
unique indexes (only ordered indexes are redistributed).
</p>
<p>
The redistribution for
<a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4">
<code class="literal">
NDBCLUSTER
</code>
</a>
tables already existing before the new data nodes were added is
not automatic, but can be accomplished using simple SQL
statements in
<a class="link" href="mysql.html" title="6.5.1 mysql — The MySQL Command-Line Client">
<span class="command">
<strong>
mysql
</strong>
</span>
</a>
or another MySQL client
application. However, all data and indexes added to tables
created after a new node group has been added are distributed
automatically among all cluster data nodes, including those
added as part of the new node group.
</p>
<p>
<b>
Partial starts.
</b>
It is possible to add a new node group without all of the new
data nodes being started. It is also possible to add a new
node group to a degraded cluster—that is, a cluster that
is only partially started, or where one or more data nodes are
not running. In the latter case, the cluster must have enough
nodes running to be viable before the new node group can be
added.
</p>
<p>
<b>
Effects on ongoing operations.
</b>
Normal DML operations using NDB Cluster data are not prevented
by the creation or addition of a new node group, or by table
reorganization. However, it is not possible to perform DDL
concurrently with table reorganization—that is, no other
DDL statements can be issued while an
<a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement">
<code class="literal">
ALTER TABLE ...
REORGANIZE PARTITION
</code>
</a>
statement is executing. In
addition, during the execution of
<code class="literal">
ALTER TABLE ...
REORGANIZE PARTITION
</code>
(or the execution of any other
DDL statement), it is not possible to restart cluster data
nodes.
</p>
<p>
<b>
Failure handling.
</b>
Failures of data nodes during node group creation and table
reorganization are handled as shown in the following table:
</p>
<div class="table">
<a name="idm46045092454944">
</a>
<p class="title">
<b>
Table 25.38 Data node failure handling during node group creation and
table reorganization
</b>
</p>
<div class="table-contents">
<table>
<colgroup>
<col style="width: 25%"/>
<col style="width: 25%"/>
<col style="width: 25%"/>
<col style="width: 25%"/>
</colgroup>
<thead>
<tr>
<th scope="col">
Failure during
</th>
<th scope="col">
Failure in
<span class="quote">
“
<span class="quote">
Old
</span>
”
</span>
data node
</th>
<th scope="col">
Failure in
<span class="quote">
“
<span class="quote">
New
</span>
”
</span>
data node
</th>
<th scope="col">
System Failure
</th>
</tr>
</thead>
<tbody>
<tr>
<th scope="row">
Node group creation
</th>
<td>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<b>
If a node other than the master fails:
</b>
The creation of the node group is always rolled
forward.
</p>
</li>
<li class="listitem">
<p>
<b>
If the master fails:
</b>
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
<b>
If the internal commit point has been reached:
</b>
The creation of the node group is rolled
forward.
</p>
</li>
<li class="listitem">
<p>
<b>
If the internal commit point has not yet been reached.
</b>
The creation of the node group is rolled back
</p>
</li>
</ul>
</div>
</li>
</ul>
</div>
</td>
<td>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<b>
If a node other than the master fails:
</b>
The creation of the node group is always rolled
forward.
</p>
</li>
<li class="listitem">
<p>
<b>
If the master fails:
</b>
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
<b>
If the internal commit point has been reached:
</b>
The creation of the node group is rolled
forward.
</p>
</li>
<li class="listitem">
<p>
<b>
If the internal commit point has not yet been reached.
</b>
The creation of the node group is rolled back
</p>
</li>
</ul>
</div>
</li>
</ul>
</div>
</td>
<td>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<b>
If the execution of CREATE NODEGROUP has reached the internal commit
point:
</b>
When restarted, the cluster includes the new node
group. Otherwise it without.
</p>
</li>
<li class="listitem">
<p>
<b>
If the execution of CREATE NODEGROUP has not yet reached the internal
commit point:
</b>
When restarted, the cluster does not include the
new node group.
</p>
</li>
</ul>
</div>
</td>
</tr>
<tr>
<th scope="row">
Table reorganization
</th>
<td>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<b>
If a node other than the master fails:
</b>
The table reorganization is always rolled forward.
</p>
</li>
<li class="listitem">
<p>
<b>
If the master fails:
</b>
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
<b>
If the internal commit point has been reached:
</b>
The table reorganization is rolled forward.
</p>
</li>
<li class="listitem">
<p>
<b>
If the internal commit point has not yet been reached.
</b>
The table reorganization is rolled back.
</p>
</li>
</ul>
</div>
</li>
</ul>
</div>
</td>
<td>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<b>
If a node other than the master fails:
</b>
The table reorganization is always rolled forward.
</p>
</li>
<li class="listitem">
<p>
<b>
If the master fails:
</b>
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
<b>
If the internal commit point has been reached:
</b>
The table reorganization is rolled forward.
</p>
</li>
<li class="listitem">
<p>
<b>
If the internal commit point has not yet been reached.
</b>
The table reorganization is rolled back.
</p>
</li>
</ul>
</div>
</li>
</ul>
</div>
</td>
<td>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<b>
If the execution of an ALTER TABLE ... REORGANIZE PARTITION statement
has reached the internal commit point:
</b>
When the cluster is restarted, the data and
indexes belonging to
<em class="replaceable">
<code>
table
</code>
</em>
are distributed
using the
<span class="quote">
“
<span class="quote">
new
</span>
”
</span>
data nodes.
</p>
</li>
<li class="listitem">
<p>
<b>
If the execution of an ALTER TABLE ... REORGANIZE PARTITION statement
has not yet reached the internal commit point:
</b>
When the cluster is restarted, the data and
indexes belonging to
<em class="replaceable">
<code>
table
</code>
</em>
are distributed
using only the
<span class="quote">
“
<span class="quote">
old
</span>
”
</span>
data nodes.
</p>
</li>
</ul>
</div>
</td>
</tr>
</tbody>
</table>
</div>
</div>
<br class="table-break"/>
<p>
<b>
Dropping node groups.
</b>
The
<a class="link" href="mysql-cluster-programs-ndb-mgm.html" title="25.5.5 ndb_mgm — The NDB Cluster Management Client">
<span class="command">
<strong>
ndb_mgm
</strong>
</span>
</a>
client supports a
<a class="link" href="mysql-cluster-mgm-client-commands.html#ndbclient-drop-nodegroup">
<code class="literal">
DROP NODEGROUP
</code>
</a>
command,
but it is possible to drop a node group only when no data
nodes in the node group contain any data. Since there is
currently no way to
<span class="quote">
“
<span class="quote">
empty
</span>
”
</span>
a specific data node
or node group, this command works only the following two
cases:
</p>
<div class="orderedlist">
<ol class="orderedlist" type="1">
<li class="listitem">
<p>
After issuing
<a class="link" href="mysql-cluster-mgm-client-commands.html#ndbclient-create-nodegroup">
<code class="literal">
CREATE
NODEGROUP
</code>
</a>
in the
<a class="link" href="mysql-cluster-programs-ndb-mgm.html" title="25.5.5 ndb_mgm — The NDB Cluster Management Client">
<span class="command">
<strong>
ndb_mgm
</strong>
</span>
</a>
client, but before issuing any
<a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement">
<code class="literal">
ALTER TABLE ...
REORGANIZE PARTITION
</code>
</a>
statements in the
<a class="link" href="mysql.html" title="6.5.1 mysql — The MySQL Command-Line Client">
<span class="command">
<strong>
mysql
</strong>
</span>
</a>
client.
</p>
</li>
<li class="listitem">
<p>
After dropping all
<a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4">
<code class="literal">
NDBCLUSTER
</code>
</a>
tables using
<a class="link" href="drop-table.html" title="15.1.32 DROP TABLE Statement">
<code class="literal">
DROP TABLE
</code>
</a>
.
</p>
<p>
<a class="link" href="truncate-table.html" title="15.1.37 TRUNCATE TABLE Statement">
<code class="literal">
TRUNCATE TABLE
</code>
</a>
does not work
for this purpose because the data nodes continue to store
the table definitions.
</p>
</li>
</ol>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/performance-schema-instance-tables.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="performance-schema-instance-tables">
</a>
29.12.3 Performance Schema Instance Tables
</h3>
</div>
</div>
</div>
<div class="toc">
<dl class="toc">
<dt>
<span class="section">
<a href="performance-schema-cond-instances-table.html">
29.12.3.1 The cond_instances Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="performance-schema-file-instances-table.html">
29.12.3.2 The file_instances Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="performance-schema-mutex-instances-table.html">
29.12.3.3 The mutex_instances Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="performance-schema-rwlock-instances-table.html">
29.12.3.4 The rwlock_instances Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="performance-schema-socket-instances-table.html">
29.12.3.5 The socket_instances Table
</a>
</span>
</dt>
</dl>
</div>
<p>
Instance tables document what types of objects are instrumented.
They provide event names and explanatory notes or status
information:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<a class="link" href="performance-schema-cond-instances-table.html" title="29.12.3.1 The cond_instances Table">
<code class="literal">
cond_instances
</code>
</a>
: Condition
synchronization object instances
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="performance-schema-file-instances-table.html" title="29.12.3.2 The file_instances Table">
<code class="literal">
file_instances
</code>
</a>
: File instances
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="performance-schema-mutex-instances-table.html" title="29.12.3.3 The mutex_instances Table">
<code class="literal">
mutex_instances
</code>
</a>
: Mutex
synchronization object instances
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="performance-schema-rwlock-instances-table.html" title="29.12.3.4 The rwlock_instances Table">
<code class="literal">
rwlock_instances
</code>
</a>
: Lock
synchronization object instances
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="performance-schema-socket-instances-table.html" title="29.12.3.5 The socket_instances Table">
<code class="literal">
socket_instances
</code>
</a>
: Active
connection instances
</p>
</li>
</ul>
</div>
<p>
These tables list instrumented synchronization objects, files,
and connections. There are three types of synchronization
objects:
<code class="literal">
cond
</code>
,
<code class="literal">
mutex
</code>
, and
<code class="literal">
rwlock
</code>
. Each instance table has an
<code class="literal">
EVENT_NAME
</code>
or
<code class="literal">
NAME
</code>
column
to indicate the instrument associated with each row. Instrument
names may have multiple parts and form a hierarchy, as discussed
in
<a class="xref" href="performance-schema-instrument-naming.html" title="29.6 Performance Schema Instrument Naming Conventions">
Section 29.6, “Performance Schema Instrument Naming Conventions”
</a>
.
</p>
<p>
The
<code class="literal">
mutex_instances.LOCKED_BY_THREAD_ID
</code>
and
<code class="literal">
rwlock_instances.WRITE_LOCKED_BY_THREAD_ID
</code>
columns are extremely important for investigating performance
bottlenecks or deadlocks. For examples of how to use them for
this purpose, see
<a class="xref" href="performance-schema-examples.html" title="29.19 Using the Performance Schema to Diagnose Problems">
Section 29.19, “Using the Performance Schema to Diagnose Problems”
</a>
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/performance-schema-consumer-filtering.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="performance-schema-consumer-filtering">
</a>
29.4.7 Pre-Filtering by Consumer
</h3>
</div>
</div>
</div>
<p>
The
<a class="link" href="performance-schema-setup-consumers-table.html" title="29.12.2.2 The setup_consumers Table">
<code class="literal">
setup_consumers
</code>
</a>
table lists the
available consumer types and which are enabled:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa59654124"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token operator">*</span> <span class="token keyword">FROM</span> performance_schema<span class="token punctuation">.</span>setup_consumers<span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> NAME <span class="token punctuation">|</span> ENABLED <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> events_stages_current <span class="token punctuation">|</span> NO <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> events_stages_history <span class="token punctuation">|</span> NO <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> events_stages_history_long <span class="token punctuation">|</span> NO <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> events_statements_cpu <span class="token punctuation">|</span> NO <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> events_statements_current <span class="token punctuation">|</span> YES <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> events_statements_history <span class="token punctuation">|</span> YES <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> events_statements_history_long <span class="token punctuation">|</span> NO <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> events_transactions_current <span class="token punctuation">|</span> YES <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> events_transactions_history <span class="token punctuation">|</span> YES <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> events_transactions_history_long <span class="token punctuation">|</span> NO <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> events_waits_current <span class="token punctuation">|</span> NO <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> events_waits_history <span class="token punctuation">|</span> NO <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> events_waits_history_long <span class="token punctuation">|</span> NO <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> global_instrumentation <span class="token punctuation">|</span> YES <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> thread_instrumentation <span class="token punctuation">|</span> YES <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> statements_digest <span class="token punctuation">|</span> YES <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
</div>
<p>
Modify the
<a class="link" href="performance-schema-setup-consumers-table.html" title="29.12.2.2 The setup_consumers Table">
<code class="literal">
setup_consumers
</code>
</a>
table to
affect pre-filtering at the consumer stage and determine the
destinations to which events are sent. To enable or disable a
consumer, set its
<code class="literal">
ENABLED
</code>
value to
<code class="literal">
YES
</code>
or
<code class="literal">
NO
</code>
.
</p>
<p>
Modifications to the
<a class="link" href="performance-schema-setup-consumers-table.html" title="29.12.2.2 The setup_consumers Table">
<code class="literal">
setup_consumers
</code>
</a>
table affect
monitoring immediately.
</p>
<p>
If you disable a consumer, the server does not spend time
maintaining destinations for that consumer. For example, if you
do not care about historical event information, disable the
history consumers:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa84309282"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">UPDATE</span> performance_schema<span class="token punctuation">.</span>setup_consumers
<span class="token keyword">SET</span> ENABLED <span class="token operator">=</span> <span class="token string">'NO'</span>
<span class="token keyword">WHERE</span> <span class="token keyword">NAME</span> <span class="token operator">LIKE</span> <span class="token string">'%history%'</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
The consumer settings in the
<a class="link" href="performance-schema-setup-consumers-table.html" title="29.12.2.2 The setup_consumers Table">
<code class="literal">
setup_consumers
</code>
</a>
table form a
hierarchy from higher levels to lower. The following principles
apply:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
Destinations associated with a consumer receive no events
unless the Performance Schema checks the consumer and the
consumer is enabled.
</p>
</li>
<li class="listitem">
<p>
A consumer is checked only if all consumers it depends on
(if any) are enabled.
</p>
</li>
<li class="listitem">
<p>
If a consumer is not checked, or is checked but is disabled,
other consumers that depend on it are not checked.
</p>
</li>
<li class="listitem">
<p>
Dependent consumers may have their own dependent consumers.
</p>
</li>
<li class="listitem">
<p>
If an event would not be sent to any destination, the
Performance Schema does not produce it.
</p>
</li>
</ul>
</div>
<p>
The following lists describe the available consumer values. For
discussion of several representative consumer configurations and
their effect on instrumentation, see
<a class="xref" href="performance-schema-consumer-configurations.html" title="29.4.8 Example Consumer Configurations">
Section 29.4.8, “Example Consumer Configurations”
</a>
.
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<a class="xref" href="performance-schema-consumer-filtering.html#performance-schema-consumer-filtering-global-thread" title="Global and Thread Consumers">
Global and Thread Consumers
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="performance-schema-consumer-filtering.html#performance-schema-consumer-filtering-wait-event" title="Wait Event Consumers">
Wait Event Consumers
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="performance-schema-consumer-filtering.html#performance-schema-consumer-filtering-stage-event" title="Stage Event Consumers">
Stage Event Consumers
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="performance-schema-consumer-filtering.html#performance-schema-consumer-filtering-statement-event" title="Statement Event Consumers">
Statement Event Consumers
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="performance-schema-consumer-filtering.html#performance-schema-consumer-filtering-transaction-event" title="Transaction Event Consumers">
Transaction Event Consumers
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="performance-schema-consumer-filtering.html#performance-schema-consumer-filtering-statement-digest" title="Statement Digest Consumer">
Statement Digest Consumer
</a>
</p>
</li>
</ul>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h4 class="title">
<a name="performance-schema-consumer-filtering-global-thread">
</a>
Global and Thread Consumers
</h4>
</div>
</div>
</div>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<code class="literal">
global_instrumentation
</code>
is the highest
level consumer. If
<code class="literal">
global_instrumentation
</code>
is
<code class="literal">
NO
</code>
, it disables global instrumentation.
All other settings are lower level and are not checked; it
does not matter what they are set to. No global or per
thread information is maintained and no individual events
are collected in the current-events or event-history
tables. If
<code class="literal">
global_instrumentation
</code>
is
<code class="literal">
YES
</code>
, the Performance Schema maintains
information for global states and also checks the
<code class="literal">
thread_instrumentation
</code>
consumer.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
thread_instrumentation
</code>
is checked only
if
<code class="literal">
global_instrumentation
</code>
is
<code class="literal">
YES
</code>
. Otherwise, if
<code class="literal">
thread_instrumentation
</code>
is
<code class="literal">
NO
</code>
, it disables thread-specific
instrumentation and all lower-level settings are ignored.
No information is maintained per thread and no individual
events are collected in the current-events or
event-history tables. If
<code class="literal">
thread_instrumentation
</code>
is
<code class="literal">
YES
</code>
, the Performance Schema maintains
thread-specific information and also checks
<code class="literal">
events_
<em class="replaceable">
<code>
xxx
</code>
</em>
_current
</code>
consumers.
</p>
</li>
</ul>
</div>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h4 class="title">
<a name="performance-schema-consumer-filtering-wait-event">
</a>
Wait Event Consumers
</h4>
</div>
</div>
</div>
<p>
These consumers require both
<code class="literal">
global_instrumentation
</code>
and
<code class="literal">
thread_instrumentation
</code>
to be
<code class="literal">
YES
</code>
or they are not checked. If checked,
they act as follows:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<code class="literal">
events_waits_current
</code>
, if
<code class="literal">
NO
</code>
, disables collection of individual
wait events in the
<a class="link" href="performance-schema-events-waits-current-table.html" title="29.12.4.1 The events_waits_current Table">
<code class="literal">
events_waits_current
</code>
</a>
table.
If
<code class="literal">
YES
</code>
, it enables wait event
collection and the Performance Schema checks the
<code class="literal">
events_waits_history
</code>
and
<code class="literal">
events_waits_history_long
</code>
consumers.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
events_waits_history
</code>
is not checked if
<code class="literal">
event_waits_current
</code>
is
<code class="literal">
NO
</code>
. Otherwise, an
<code class="literal">
events_waits_history
</code>
value of
<code class="literal">
NO
</code>
or
<code class="literal">
YES
</code>
disables
or enables collection of wait events in the
<a class="link" href="performance-schema-events-waits-history-table.html" title="29.12.4.2 The events_waits_history Table">
<code class="literal">
events_waits_history
</code>
</a>
table.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
events_waits_history_long
</code>
is not
checked if
<code class="literal">
event_waits_current
</code>
is
<code class="literal">
NO
</code>
. Otherwise, an
<code class="literal">
events_waits_history_long
</code>
value of
<code class="literal">
NO
</code>
or
<code class="literal">
YES
</code>
disables
or enables collection of wait events in the
<a class="link" href="performance-schema-events-waits-history-long-table.html" title="29.12.4.3 The events_waits_history_long Table">
<code class="literal">
events_waits_history_long
</code>
</a>
table.
</p>
</li>
</ul>
</div>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h4 class="title">
<a name="performance-schema-consumer-filtering-stage-event">
</a>
Stage Event Consumers
</h4>
</div>
</div>
</div>
<p>
These consumers require both
<code class="literal">
global_instrumentation
</code>
and
<code class="literal">
thread_instrumentation
</code>
to be
<code class="literal">
YES
</code>
or they are not checked. If checked,
they act as follows:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<code class="literal">
events_stages_current
</code>
, if
<code class="literal">
NO
</code>
, disables collection of individual
stage events in the
<a class="link" href="performance-schema-events-stages-current-table.html" title="29.12.5.1 The events_stages_current Table">
<code class="literal">
events_stages_current
</code>
</a>
table.
If
<code class="literal">
YES
</code>
, it enables stage event
collection and the Performance Schema checks the
<code class="literal">
events_stages_history
</code>
and
<code class="literal">
events_stages_history_long
</code>
consumers.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
events_stages_history
</code>
is not checked if
<code class="literal">
event_stages_current
</code>
is
<code class="literal">
NO
</code>
. Otherwise, an
<code class="literal">
events_stages_history
</code>
value of
<code class="literal">
NO
</code>
or
<code class="literal">
YES
</code>
disables
or enables collection of stage events in the
<a class="link" href="performance-schema-events-stages-history-table.html" title="29.12.5.2 The events_stages_history Table">
<code class="literal">
events_stages_history
</code>
</a>
table.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
events_stages_history_long
</code>
is not
checked if
<code class="literal">
event_stages_current
</code>
is
<code class="literal">
NO
</code>
. Otherwise, an
<code class="literal">
events_stages_history_long
</code>
value of
<code class="literal">
NO
</code>
or
<code class="literal">
YES
</code>
disables
or enables collection of stage events in the
<a class="link" href="performance-schema-events-stages-history-long-table.html" title="29.12.5.3 The events_stages_history_long Table">
<code class="literal">
events_stages_history_long
</code>
</a>
table.
</p>
</li>
</ul>
</div>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h4 class="title">
<a name="performance-schema-consumer-filtering-statement-event">
</a>
Statement Event Consumers
</h4>
</div>
</div>
</div>
<p>
These consumers require both
<code class="literal">
global_instrumentation
</code>
and
<code class="literal">
thread_instrumentation
</code>
to be
<code class="literal">
YES
</code>
or they are not checked. If checked,
they act as follows:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<code class="literal">
events_statements_cpu
</code>
, if
<code class="literal">
NO
</code>
, disables measurement of
<code class="literal">
CPU_TIME
</code>
. If
<code class="literal">
YES
</code>
,
and the instrumentation is enabled and timed,
<code class="literal">
CPU_TIME
</code>
is measured.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
events_statements_current
</code>
, if
<code class="literal">
NO
</code>
, disables collection of individual
statement events in the
<a class="link" href="performance-schema-events-statements-current-table.html" title="29.12.6.1 The events_statements_current Table">
<code class="literal">
events_statements_current
</code>
</a>
table. If
<code class="literal">
YES
</code>
, it enables statement
event collection and the Performance Schema checks the
<code class="literal">
events_statements_history
</code>
and
<code class="literal">
events_statements_history_long
</code>
consumers.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
events_statements_history
</code>
is not
checked if
<code class="literal">
events_statements_current
</code>
is
<code class="literal">
NO
</code>
. Otherwise, an
<code class="literal">
events_statements_history
</code>
value of
<code class="literal">
NO
</code>
or
<code class="literal">
YES
</code>
disables
or enables collection of statement events in the
<a class="link" href="performance-schema-events-statements-history-table.html" title="29.12.6.2 The events_statements_history Table">
<code class="literal">
events_statements_history
</code>
</a>
table.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
events_statements_history_long
</code>
is not
checked if
<code class="literal">
events_statements_current
</code>
is
<code class="literal">
NO
</code>
. Otherwise, an
<code class="literal">
events_statements_history_long
</code>
value of
<code class="literal">
NO
</code>
or
<code class="literal">
YES
</code>
disables
or enables collection of statement events in the
<a class="link" href="performance-schema-events-statements-history-long-table.html" title="29.12.6.3 The events_statements_history_long Table">
<code class="literal">
events_statements_history_long
</code>
</a>
table.
</p>
</li>
</ul>
</div>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h4 class="title">
<a name="performance-schema-consumer-filtering-transaction-event">
</a>
Transaction Event Consumers
</h4>
</div>
</div>
</div>
<p>
These consumers require both
<code class="literal">
global_instrumentation
</code>
and
<code class="literal">
thread_instrumentation
</code>
to be
<code class="literal">
YES
</code>
or they are not checked. If checked,
they act as follows:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<code class="literal">
events_transactions_current
</code>
, if
<code class="literal">
NO
</code>
, disables collection of individual
transaction events in the
<a class="link" href="performance-schema-events-transactions-current-table.html" title="29.12.7.1 The events_transactions_current Table">
<code class="literal">
events_transactions_current
</code>
</a>
table. If
<code class="literal">
YES
</code>
, it enables transaction
event collection and the Performance Schema checks the
<code class="literal">
events_transactions_history
</code>
and
<code class="literal">
events_transactions_history_long
</code>
consumers.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
events_transactions_history
</code>
is not
checked if
<code class="literal">
events_transactions_current
</code>
is
<code class="literal">
NO
</code>
. Otherwise, an
<code class="literal">
events_transactions_history
</code>
value of
<code class="literal">
NO
</code>
or
<code class="literal">
YES
</code>
disables
or enables collection of transaction events in the
<a class="link" href="performance-schema-events-transactions-history-table.html" title="29.12.7.2 The events_transactions_history Table">
<code class="literal">
events_transactions_history
</code>
</a>
table.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
events_transactions_history_long
</code>
is not
checked if
<code class="literal">
events_transactions_current
</code>
is
<code class="literal">
NO
</code>
. Otherwise, an
<code class="literal">
events_transactions_history_long
</code>
value
of
<code class="literal">
NO
</code>
or
<code class="literal">
YES
</code>
disables or enables collection of transaction events in
the
<a class="link" href="performance-schema-events-transactions-history-long-table.html" title="29.12.7.3 The events_transactions_history_long Table">
<code class="literal">
events_transactions_history_long
</code>
</a>
table.
</p>
</li>
</ul>
</div>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h4 class="title">
<a name="performance-schema-consumer-filtering-statement-digest">
</a>
Statement Digest Consumer
</h4>
</div>
</div>
</div>
<p>
The
<code class="literal">
statements_digest
</code>
consumer requires
<code class="literal">
global_instrumentation
</code>
to be
<code class="literal">
YES
</code>
or it is not checked. There is no
dependency on the statement event consumers, so you can obtain
statistics per digest without having to collect statistics in
<a class="link" href="performance-schema-events-statements-current-table.html" title="29.12.6.1 The events_statements_current Table">
<code class="literal">
events_statements_current
</code>
</a>
, which
is advantageous in terms of overhead. Conversely, you can get
detailed statements in
<a class="link" href="performance-schema-events-statements-current-table.html" title="29.12.6.1 The events_statements_current Table">
<code class="literal">
events_statements_current
</code>
</a>
without
digests (the
<code class="literal">
DIGEST
</code>
and
<code class="literal">
DIGEST_TEXT
</code>
columns are
<code class="literal">
NULL
</code>
in this case).
</p>
<p>
For more information about statement digesting, see
<a class="xref" href="performance-schema-statement-digests.html" title="29.10 Performance Schema Statement Digests and Sampling">
Section 29.10, “Performance Schema Statement Digests and Sampling”
</a>
.
</p>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/mysql-cluster-logs-cluster-log.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="mysql-cluster-logs-cluster-log">
</a>
25.6.2.1 NDB Cluster: Messages in the Cluster Log
</h4>
</div>
</div>
</div>
<p>
The following table lists the most common
<a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4">
<code class="literal">
NDB
</code>
</a>
cluster log messages. For
information about the cluster log, log events, and event types,
see
<a class="xref" href="mysql-cluster-event-reports.html" title="25.6.3 Event Reports Generated in NDB Cluster">
Section 25.6.3, “Event Reports Generated in NDB Cluster”
</a>
. These log
messages also correspond to log event types in the MGM API; see
<a class="ulink" href="/doc/ndbapi/en/mgm-types.html#mgm-ndb-logevent-type" target="_top">
The Ndb_logevent_type Type
</a>
, for related information
of interest to Cluster API developers.
</p>
<div class="table">
<a name="idm46045094348128">
</a>
<p class="title">
<b>
Table 25.25 Common NDB cluster log messages
</b>
</p>
<div class="table-contents">
<table>
<colgroup>
<col style="width: 20%"/>
<col style="width: 20%"/>
<col style="width: 25%"/>
<col style="width: 15%"/>
<col style="width: 10%"/>
<col style="width: 10%"/>
</colgroup>
<thead>
<tr>
<th scope="col">
Log Message
</th>
<th scope="col">
Description
</th>
<th scope="col">
Event Name
</th>
<th scope="col">
Event Type
</th>
<th scope="col">
Priority
</th>
<th scope="col">
Severity
</th>
</tr>
</thead>
<tbody>
<tr>
<th scope="row">
<code class="literal">
Node
<em class="replaceable">
<code>
mgm_node_id
</code>
</em>
: Node
<em class="replaceable">
<code>
data_node_id
</code>
</em>
Connected
</code>
</th>
<td>
The data node having node ID
<em class="replaceable">
<code>
node_id
</code>
</em>
has
connected to the management server (node
<em class="replaceable">
<code>
mgm_node_id
</code>
</em>
).
</td>
<td>
<code class="literal">
Connected
</code>
</td>
<td>
<code class="literal">
Connection
</code>
</td>
<td>
8
</td>
<td>
<code class="literal">
INFO
</code>
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
Node
<em class="replaceable">
<code>
mgm_node_id
</code>
</em>
: Node
<em class="replaceable">
<code>
data_node_id
</code>
</em>
Disconnected
</code>
</th>
<td>
The data node having node ID
<em class="replaceable">
<code>
data_node_id
</code>
</em>
has
disconnected from the management server (node
<em class="replaceable">
<code>
mgm_node_id
</code>
</em>
).
</td>
<td>
<code class="literal">
Disconnected
</code>
</td>
<td>
<code class="literal">
Connection
</code>
</td>
<td>
8
</td>
<td>
<code class="literal">
ALERT
</code>
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
Node
<em class="replaceable">
<code>
data_node_id
</code>
</em>
: Communication to
Node
<em class="replaceable">
<code>
api_node_id
</code>
</em>
closed
</code>
</th>
<td>
The API node or SQL node having node ID
<em class="replaceable">
<code>
api_node_id
</code>
</em>
is no longer
communicating with data node
<em class="replaceable">
<code>
data_node_id
</code>
</em>
.
</td>
<td>
<code class="literal">
CommunicationClosed
</code>
</td>
<td>
<code class="literal">
Connection
</code>
</td>
<td>
8
</td>
<td>
<code class="literal">
INFO
</code>
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
Node
<em class="replaceable">
<code>
data_node_id
</code>
</em>
: Communication to
Node
<em class="replaceable">
<code>
api_node_id
</code>
</em>
opened
</code>
</th>
<td>
The API node or SQL node having node ID
<em class="replaceable">
<code>
api_node_id
</code>
</em>
is now
communicating with data node
<em class="replaceable">
<code>
data_node_id
</code>
</em>
.
</td>
<td>
<code class="literal">
CommunicationOpened
</code>
</td>
<td>
<code class="literal">
Connection
</code>
</td>
<td>
8
</td>
<td>
<code class="literal">
INFO
</code>
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
Node
<em class="replaceable">
<code>
mgm_node_id
</code>
</em>
: Node
<em class="replaceable">
<code>
api_node_id
</code>
</em>
: API
<em class="replaceable">
<code>
version
</code>
</em>
</code>
</th>
<td>
The API node having node ID
<em class="replaceable">
<code>
api_node_id
</code>
</em>
has
connected to management node
<em class="replaceable">
<code>
mgm_node_id
</code>
</em>
using
<a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4">
<code class="literal">
NDB
</code>
</a>
API version
<em class="replaceable">
<code>
version
</code>
</em>
(generally the same as
the MySQL version number).
</td>
<td>
<code class="literal">
ConnectedApiVersion
</code>
</td>
<td>
<code class="literal">
Connection
</code>
</td>
<td>
8
</td>
<td>
<code class="literal">
INFO
</code>
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
Node
<em class="replaceable">
<code>
node_id
</code>
</em>
: Global checkpoint
<em class="replaceable">
<code>
gci
</code>
</em>
started
</code>
</th>
<td>
A global checkpoint with the ID
<em class="replaceable">
<code>
gci
</code>
</em>
has been
started; node
<em class="replaceable">
<code>
node_id
</code>
</em>
is the
master responsible for this global checkpoint.
</td>
<td>
<code class="literal">
GlobalCheckpointStarted
</code>
</td>
<td>
<code class="literal">
Checkpoint
</code>
</td>
<td>
9
</td>
<td>
<code class="literal">
INFO
</code>
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
Node
<em class="replaceable">
<code>
node_id
</code>
</em>
: Global checkpoint
<em class="replaceable">
<code>
gci
</code>
</em>
completed
</code>
</th>
<td>
The global checkpoint having the ID
<em class="replaceable">
<code>
gci
</code>
</em>
has
been completed; node
<em class="replaceable">
<code>
node_id
</code>
</em>
was the master responsible for this global checkpoint.
</td>
<td>
<code class="literal">
GlobalCheckpointCompleted
</code>
</td>
<td>
<code class="literal">
Checkpoint
</code>
</td>
<td>
10
</td>
<td>
<code class="literal">
INFO
</code>
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
Node
<em class="replaceable">
<code>
node_id
</code>
</em>
: Local checkpoint
<em class="replaceable">
<code>
lcp
</code>
</em>
started. Keep GCI =
<em class="replaceable">
<code>
current_gci
</code>
</em>
oldest restorable
GCI =
<em class="replaceable">
<code>
old_gci
</code>
</em>
</code>
</th>
<td>
The local checkpoint having sequence ID
<em class="replaceable">
<code>
lcp
</code>
</em>
has been started on node
<em class="replaceable">
<code>
node_id
</code>
</em>
. The most recent GCI
that can be used has the index
<em class="replaceable">
<code>
current_gci
</code>
</em>
, and the oldest GCI
from which the cluster can be restored has the index
<em class="replaceable">
<code>
old_gci
</code>
</em>
.
</td>
<td>
<code class="literal">
LocalCheckpointStarted
</code>
</td>
<td>
<code class="literal">
Checkpoint
</code>
</td>
<td>
7
</td>
<td>
<code class="literal">
INFO
</code>
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
Node
<em class="replaceable">
<code>
node_id
</code>
</em>
: Local checkpoint
<em class="replaceable">
<code>
lcp
</code>
</em>
completed
</code>
</th>
<td>
The local checkpoint having sequence ID
<em class="replaceable">
<code>
lcp
</code>
</em>
on node
<em class="replaceable">
<code>
node_id
</code>
</em>
has been
completed.
</td>
<td>
<code class="literal">
LocalCheckpointCompleted
</code>
</td>
<td>
<code class="literal">
Checkpoint
</code>
</td>
<td>
8
</td>
<td>
<code class="literal">
INFO
</code>
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
Node
<em class="replaceable">
<code>
node_id
</code>
</em>
: Local Checkpoint
stopped in CALCULATED_KEEP_GCI
</code>
</th>
<td>
The node was unable to determine the most recent usable GCI.
</td>
<td>
<code class="literal">
LCPStoppedInCalcKeepGci
</code>
</td>
<td>
<code class="literal">
Checkpoint
</code>
</td>
<td>
0
</td>
<td>
<code class="literal">
ALERT
</code>
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
Node
<em class="replaceable">
<code>
node_id
</code>
</em>
: Table ID =
<em class="replaceable">
<code>
table_id
</code>
</em>
, fragment
<em class="replaceable">
<code>
ID = fragment_id
</code>
</em>
has completed
LCP on Node
<em class="replaceable">
<code>
node_id
</code>
</em>
maxGciStarted:
<em class="replaceable">
<code>
started_gci
</code>
</em>
maxGciCompleted:
<em class="replaceable">
<code>
completed_gci
</code>
</em>
</code>
</th>
<td>
A table fragment has been checkpointed to disk on node
<em class="replaceable">
<code>
node_id
</code>
</em>
. The GCI in progress
has the index
<em class="replaceable">
<code>
started_gci
</code>
</em>
, and
the most recent GCI to have been completed has the index
<em class="replaceable">
<code>
completed_gci
</code>
</em>
.
</td>
<td>
<code class="literal">
LCPFragmentCompleted
</code>
</td>
<td>
<code class="literal">
Checkpoint
</code>
</td>
<td>
11
</td>
<td>
<code class="literal">
INFO
</code>
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
Node
<em class="replaceable">
<code>
node_id
</code>
</em>
: ACC Blocked
<em class="replaceable">
<code>
num_1
</code>
</em>
and TUP Blocked
<em class="replaceable">
<code>
num_2
</code>
</em>
times last
second
</code>
</th>
<td>
Undo logging is blocked because the log buffer is close to overflowing.
</td>
<td>
<code class="literal">
UndoLogBlocked
</code>
</td>
<td>
<code class="literal">
Checkpoint
</code>
</td>
<td>
7
</td>
<td>
<code class="literal">
INFO
</code>
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
Node
<em class="replaceable">
<code>
node_id
</code>
</em>
: Start initiated
<em class="replaceable">
<code>
version
</code>
</em>
</code>
</th>
<td>
Data node
<em class="replaceable">
<code>
node_id
</code>
</em>
, running
<a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4">
<code class="literal">
NDB
</code>
</a>
version
<em class="replaceable">
<code>
version
</code>
</em>
, is beginning its
startup process.
</td>
<td>
<code class="literal">
NDBStartStarted
</code>
</td>
<td>
<code class="literal">
StartUp
</code>
</td>
<td>
1
</td>
<td>
<code class="literal">
INFO
</code>
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
Node
<em class="replaceable">
<code>
node_id
</code>
</em>
: Started
<em class="replaceable">
<code>
version
</code>
</em>
</code>
</th>
<td>
Data node
<em class="replaceable">
<code>
node_id
</code>
</em>
, running
<a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4">
<code class="literal">
NDB
</code>
</a>
version
<em class="replaceable">
<code>
version
</code>
</em>
, has started
successfully.
</td>
<td>
<code class="literal">
NDBStartCompleted
</code>
</td>
<td>
<code class="literal">
StartUp
</code>
</td>
<td>
1
</td>
<td>
<code class="literal">
INFO
</code>
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
Node
<em class="replaceable">
<code>
node_id
</code>
</em>
: STTORRY received after
restart finished
</code>
</th>
<td>
The node has received a signal indicating that a cluster restart has
completed.
</td>
<td>
<code class="literal">
STTORRYRecieved
</code>
</td>
<td>
<code class="literal">
StartUp
</code>
</td>
<td>
15
</td>
<td>
<code class="literal">
INFO
</code>
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
Node
<em class="replaceable">
<code>
node_id
</code>
</em>
: Start phase
<em class="replaceable">
<code>
phase
</code>
</em>
completed
(
<em class="replaceable">
<code>
type
</code>
</em>
)
</code>
</th>
<td>
The node has completed start phase
<em class="replaceable">
<code>
phase
</code>
</em>
of a
<em class="replaceable">
<code>
type
</code>
</em>
start. For a listing of
start phases, see
<a class="xref" href="mysql-cluster-start-phases.html" title="25.6.4 Summary of NDB Cluster Start Phases">
Section 25.6.4, “Summary of NDB Cluster Start Phases”
</a>
.
(
<em class="replaceable">
<code>
type
</code>
</em>
is one of
<code class="literal">
initial
</code>
,
<code class="literal">
system
</code>
,
<code class="literal">
node
</code>
,
<code class="literal">
initial node
</code>
,
or
<code class="literal">
<Unknown>
</code>
.)
</td>
<td>
<code class="literal">
StartPhaseCompleted
</code>
</td>
<td>
<code class="literal">
StartUp
</code>
</td>
<td>
4
</td>
<td>
<code class="literal">
INFO
</code>
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
Node
<em class="replaceable">
<code>
node_id
</code>
</em>
: CM_REGCONF president =
<em class="replaceable">
<code>
president_id
</code>
</em>
, own Node =
<em class="replaceable">
<code>
own_id
</code>
</em>
, our dynamic id =
<em class="replaceable">
<code>
dynamic_id
</code>
</em>
</code>
</th>
<td>
Node
<em class="replaceable">
<code>
president_id
</code>
</em>
has been selected as
<span class="quote">
“
<span class="quote">
president
</span>
”
</span>
.
<em class="replaceable">
<code>
own_id
</code>
</em>
and
<em class="replaceable">
<code>
dynamic_id
</code>
</em>
should always be the
same as the ID (
<em class="replaceable">
<code>
node_id
</code>
</em>
) of the
reporting node.
</td>
<td>
<code class="literal">
CM_REGCONF
</code>
</td>
<td>
<code class="literal">
StartUp
</code>
</td>
<td>
3
</td>
<td>
<code class="literal">
INFO
</code>
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
Node
<em class="replaceable">
<code>
node_id
</code>
</em>
: CM_REGREF from Node
<em class="replaceable">
<code>
president_id
</code>
</em>
to our Node
<em class="replaceable">
<code>
node_id
</code>
</em>
. Cause =
<em class="replaceable">
<code>
cause
</code>
</em>
</code>
</th>
<td>
The reporting node (ID
<em class="replaceable">
<code>
node_id
</code>
</em>
) was unable to
accept node
<em class="replaceable">
<code>
president_id
</code>
</em>
as
president. The
<em class="replaceable">
<code>
cause
</code>
</em>
of the
problem is given as one of
<code class="literal">
Busy
</code>
,
<code class="literal">
Election with wait = false
</code>
,
<code class="literal">
Not president
</code>
,
<code class="literal">
Election
without selecting new candidate
</code>
, or
<code class="literal">
No
such cause
</code>
.
</td>
<td>
<code class="literal">
CM_REGREF
</code>
</td>
<td>
<code class="literal">
StartUp
</code>
</td>
<td>
8
</td>
<td>
<code class="literal">
INFO
</code>
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
Node
<em class="replaceable">
<code>
node_id
</code>
</em>
: We are Node
<em class="replaceable">
<code>
own_id
</code>
</em>
with dynamic ID
<em class="replaceable">
<code>
dynamic_id
</code>
</em>
, our left neighbor
is Node
<em class="replaceable">
<code>
id_1
</code>
</em>
, our right is Node
<em class="replaceable">
<code>
id_2
</code>
</em>
</code>
</th>
<td>
The node has discovered its neighboring nodes in the cluster (node
<em class="replaceable">
<code>
id_1
</code>
</em>
and node
<em class="replaceable">
<code>
id_2
</code>
</em>
).
<em class="replaceable">
<code>
node_id
</code>
</em>
,
<em class="replaceable">
<code>
own_id
</code>
</em>
, and
<em class="replaceable">
<code>
dynamic_id
</code>
</em>
should always be the
same; if they are not, this indicates a serious
misconfiguration of the cluster nodes.
</td>
<td>
<code class="literal">
FIND_NEIGHBOURS
</code>
</td>
<td>
<code class="literal">
StartUp
</code>
</td>
<td>
8
</td>
<td>
<code class="literal">
INFO
</code>
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
Node
<em class="replaceable">
<code>
node_id
</code>
</em>
:
<em class="replaceable">
<code>
type
</code>
</em>
shutdown
initiated
</code>
</th>
<td>
The node has received a shutdown signal. The
<em class="replaceable">
<code>
type
</code>
</em>
of shutdown is either
<code class="literal">
Cluster
</code>
or
<code class="literal">
Node
</code>
.
</td>
<td>
<code class="literal">
NDBStopStarted
</code>
</td>
<td>
<code class="literal">
StartUp
</code>
</td>
<td>
1
</td>
<td>
<code class="literal">
INFO
</code>
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
Node
<em class="replaceable">
<code>
node_id
</code>
</em>
: Node shutdown
completed
</code>
[
<code class="literal">
,
<em class="replaceable">
<code>
action
</code>
</em>
</code>
]
[
<code class="literal">
Initiated by signal
<em class="replaceable">
<code>
signal
</code>
</em>
.
</code>
]
</th>
<td>
The node has been shut down. This report may include an
<em class="replaceable">
<code>
action
</code>
</em>
, which if present is one
of
<code class="literal">
restarting
</code>
,
<code class="literal">
no
start
</code>
, or
<code class="literal">
initial
</code>
. The report
may also include a reference to an
<a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4">
<code class="literal">
NDB
</code>
</a>
Protocol
<em class="replaceable">
<code>
signal
</code>
</em>
; for possible signals,
refer to
<a class="ulink" href="/doc/ndb-internals/en/ndb-internals-ndb-protocol-operations-signals.html" target="_top">
Operations and Signals
</a>
.
</td>
<td>
<code class="literal">
NDBStopCompleted
</code>
</td>
<td>
<code class="literal">
StartUp
</code>
</td>
<td>
1
</td>
<td>
<code class="literal">
INFO
</code>
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
Node
<em class="replaceable">
<code>
node_id
</code>
</em>
: Forced node shutdown
completed
</code>
[
<code class="literal">
,
action
</code>
]
<code class="literal">
.
</code>
[
<code class="literal">
Occurred
during startphase
<em class="replaceable">
<code>
start_phase
</code>
</em>
.
</code>
]
[
<code class="literal">
Initiated by
<em class="replaceable">
<code>
signal
</code>
</em>
.
</code>
]
[
<code class="literal">
Caused by error
<em class="replaceable">
<code>
error_code
</code>
</em>
:
'
<em class="replaceable">
<code>
error_message
</code>
</em>
(
<em class="replaceable">
<code>
error_classification
</code>
</em>
).
<em class="replaceable">
<code>
error_status
</code>
</em>
'.
</code>
[
<code class="literal">
(extra info
<em class="replaceable">
<code>
extra_code
</code>
</em>
)
</code>
]]
</th>
<td>
The node has been forcibly shut down. The
<em class="replaceable">
<code>
action
</code>
</em>
(one of
<code class="literal">
restarting
</code>
,
<code class="literal">
no
start
</code>
, or
<code class="literal">
initial
</code>
)
subsequently being taken, if any, is also reported. If the
shutdown occurred while the node was starting, the report
includes the
<em class="replaceable">
<code>
start_phase
</code>
</em>
during
which the node failed. If this was a result of a
<em class="replaceable">
<code>
signal
</code>
</em>
sent to the node, this
information is also provided (see
<a class="ulink" href="/doc/ndb-internals/en/ndb-internals-ndb-protocol-operations-signals.html" target="_top">
Operations and Signals
</a>
,
for more information). If the error causing the failure is
known, this is also included; for more information about
<a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4">
<code class="literal">
NDB
</code>
</a>
error messages and
classifications, see
<a class="ulink" href="/doc/ndb-internals/en/ndb-errors.html" target="_top">
NDB Cluster API Errors
</a>
.
</td>
<td>
<code class="literal">
NDBStopForced
</code>
</td>
<td>
<code class="literal">
StartUp
</code>
</td>
<td>
1
</td>
<td>
<code class="literal">
ALERT
</code>
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
Node
<em class="replaceable">
<code>
node_id
</code>
</em>
: Node shutdown
aborted
</code>
</th>
<td>
The node shutdown process was aborted by the user.
</td>
<td>
<code class="literal">
NDBStopAborted
</code>
</td>
<td>
<code class="literal">
StartUp
</code>
</td>
<td>
1
</td>
<td>
<code class="literal">
INFO
</code>
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
Node
<em class="replaceable">
<code>
node_id
</code>
</em>
: StartLog: [GCI Keep:
<em class="replaceable">
<code>
keep_pos
</code>
</em>
LastCompleted:
<em class="replaceable">
<code>
last_pos
</code>
</em>
NewestRestorable:
<em class="replaceable">
<code>
restore_pos
</code>
</em>
]
</code>
</th>
<td>
This reports global checkpoints referenced during a node start. The redo
log prior to
<em class="replaceable">
<code>
keep_pos
</code>
</em>
is
dropped.
<em class="replaceable">
<code>
last_pos
</code>
</em>
is the last
global checkpoint in which data node the participated;
<em class="replaceable">
<code>
restore_pos
</code>
</em>
is the global
checkpoint which is actually used to restore all data
nodes.
</td>
<td>
<code class="literal">
StartREDOLog
</code>
</td>
<td>
<code class="literal">
StartUp
</code>
</td>
<td>
4
</td>
<td>
<code class="literal">
INFO
</code>
</td>
</tr>
<tr>
<th scope="row">
<em class="replaceable">
<code>
startup_message
</code>
</em>
[
<span class="emphasis">
<em>
Listed separately;
see below.
</em>
</span>
]
</th>
<td>
There are a number of possible startup messages that can be logged under
different circumstances. These are listed separately; see
<a class="xref" href="mysql-cluster-log-startup-messages.html" title="25.6.2.2 NDB Cluster Log Startup Messages">
Section 25.6.2.2, “NDB Cluster Log Startup Messages”
</a>
.
</td>
<td>
<code class="literal">
StartReport
</code>
</td>
<td>
<code class="literal">
StartUp
</code>
</td>
<td>
4
</td>
<td>
<code class="literal">
INFO
</code>
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
Node
<em class="replaceable">
<code>
node_id
</code>
</em>
: Node restart completed
copy of dictionary information
</code>
</th>
<td>
Copying of data dictionary information to the restarted node has been
completed.
</td>
<td>
<code class="literal">
NR_CopyDict
</code>
</td>
<td>
<code class="literal">
NodeRestart
</code>
</td>
<td>
8
</td>
<td>
<code class="literal">
INFO
</code>
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
Node
<em class="replaceable">
<code>
node_id
</code>
</em>
: Node restart completed
copy of distribution information
</code>
</th>
<td>
Copying of data distribution information to the restarted node has been
completed.
</td>
<td>
<code class="literal">
NR_CopyDistr
</code>
</td>
<td>
<code class="literal">
NodeRestart
</code>
</td>
<td>
8
</td>
<td>
<code class="literal">
INFO
</code>
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
Node
<em class="replaceable">
<code>
node_id
</code>
</em>
: Node restart starting
to copy the fragments to Node
<em class="replaceable">
<code>
node_id
</code>
</em>
</code>
</th>
<td>
Copy of fragments to starting data node
<em class="replaceable">
<code>
node_id
</code>
</em>
has begun
</td>
<td>
<code class="literal">
NR_CopyFragsStarted
</code>
</td>
<td>
<code class="literal">
NodeRestart
</code>
</td>
<td>
8
</td>
<td>
<code class="literal">
INFO
</code>
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
Node
<em class="replaceable">
<code>
node_id
</code>
</em>
: Table ID =
<em class="replaceable">
<code>
table_id
</code>
</em>
, fragment ID =
<em class="replaceable">
<code>
fragment_id
</code>
</em>
have been copied to
Node
<em class="replaceable">
<code>
node_id
</code>
</em>
</code>
</th>
<td>
Fragment
<em class="replaceable">
<code>
fragment_id
</code>
</em>
from table
<em class="replaceable">
<code>
table_id
</code>
</em>
has been copied to
data node
<em class="replaceable">
<code>
node_id
</code>
</em>
</td>
<td>
<code class="literal">
NR_CopyFragDone
</code>
</td>
<td>
<code class="literal">
NodeRestart
</code>
</td>
<td>
10
</td>
<td>
<code class="literal">
INFO
</code>
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
Node
<em class="replaceable">
<code>
node_id
</code>
</em>
: Node restart completed
copying the fragments to Node
<em class="replaceable">
<code>
node_id
</code>
</em>
</code>
</th>
<td>
Copying of all table fragments to restarting data node
<em class="replaceable">
<code>
node_id
</code>
</em>
has been completed
</td>
<td>
<code class="literal">
NR_CopyFragsCompleted
</code>
</td>
<td>
<code class="literal">
NodeRestart
</code>
</td>
<td>
8
</td>
<td>
<code class="literal">
INFO
</code>
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
Node
<em class="replaceable">
<code>
node_id
</code>
</em>
: Node
<em class="replaceable">
<code>
node1_id
</code>
</em>
completed failure of
Node
<em class="replaceable">
<code>
node2_id
</code>
</em>
</code>
</th>
<td>
Data node
<em class="replaceable">
<code>
node1_id
</code>
</em>
has detected the failure
of data node
<em class="replaceable">
<code>
node2_id
</code>
</em>
</td>
<td>
<code class="literal">
NodeFailCompleted
</code>
</td>
<td>
<code class="literal">
NodeRestart
</code>
</td>
<td>
8
</td>
<td>
<code class="literal">
ALERT
</code>
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
All nodes completed failure of Node
<em class="replaceable">
<code>
node_id
</code>
</em>
</code>
</th>
<td>
All (remaining) data nodes have detected the failure of data node
<em class="replaceable">
<code>
node_id
</code>
</em>
</td>
<td>
<code class="literal">
NodeFailCompleted
</code>
</td>
<td>
<code class="literal">
NodeRestart
</code>
</td>
<td>
8
</td>
<td>
<code class="literal">
ALERT
</code>
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
Node failure of
<em class="replaceable">
<code>
node_id
</code>
</em>
<em class="replaceable">
<code>
block
</code>
</em>
completed
</code>
</th>
<td>
The failure of data node
<em class="replaceable">
<code>
node_id
</code>
</em>
has been
detected in the
<em class="replaceable">
<code>
block
</code>
</em>
<a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4">
<code class="literal">
NDB
</code>
</a>
kernel block, where block is 1 of
<a class="ulink" href="/doc/ndb-internals/en/ndb-internals-kernel-blocks-dbtc.html" target="_top">
<code class="literal">
DBTC
</code>
</a>
,
<a class="ulink" href="/doc/ndb-internals/en/ndb-internals-kernel-blocks-dbdict.html" target="_top">
<code class="literal">
DBDICT
</code>
</a>
,
<a class="ulink" href="/doc/ndb-internals/en/ndb-internals-kernel-blocks-dbdih.html" target="_top">
<code class="literal">
DBDIH
</code>
</a>
, or
<a class="ulink" href="/doc/ndb-internals/en/ndb-internals-kernel-blocks-dblqh.html" target="_top">
<code class="literal">
DBLQH
</code>
</a>
; for more
information, see
<a class="ulink" href="/doc/ndb-internals/en/ndb-internals-kernel-blocks.html" target="_top">
NDB Kernel Blocks
</a>
</td>
<td>
<code class="literal">
NodeFailCompleted
</code>
</td>
<td>
<code class="literal">
NodeRestart
</code>
</td>
<td>
8
</td>
<td>
<code class="literal">
ALERT
</code>
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
Node
<em class="replaceable">
<code>
mgm_node_id
</code>
</em>
: Node
<em class="replaceable">
<code>
data_node_id
</code>
</em>
has failed. The
Node state at failure was
<em class="replaceable">
<code>
state_code
</code>
</em>
</code>
</th>
<td>
A data node has failed. Its state at the time of failure is described by
an arbitration state code
<em class="replaceable">
<code>
state_code
</code>
</em>
: possible state code
values can be found in the file
<code class="filename">
include/kernel/signaldata/ArbitSignalData.hpp
</code>
.
</td>
<td>
<code class="literal">
NODE_FAILREP
</code>
</td>
<td>
<code class="literal">
NodeRestart
</code>
</td>
<td>
8
</td>
<td>
<code class="literal">
ALERT
</code>
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
President restarts arbitration thread
[state=
<em class="replaceable">
<code>
state_code
</code>
</em>
]
</code>
or
<code class="literal">
Prepare arbitrator node
<em class="replaceable">
<code>
node_id
</code>
</em>
[ticket=
<em class="replaceable">
<code>
ticket_id
</code>
</em>
]
</code>
or
<code class="literal">
Receive arbitrator node
<em class="replaceable">
<code>
node_id
</code>
</em>
[ticket=
<em class="replaceable">
<code>
ticket_id
</code>
</em>
]
</code>
or
<code class="literal">
Started arbitrator node
<em class="replaceable">
<code>
node_id
</code>
</em>
[ticket=
<em class="replaceable">
<code>
ticket_id
</code>
</em>
]
</code>
or
<code class="literal">
Lost arbitrator node
<em class="replaceable">
<code>
node_id
</code>
</em>
- process failure
[state=
<em class="replaceable">
<code>
state_code
</code>
</em>
]
</code>
or
<code class="literal">
Lost arbitrator node
<em class="replaceable">
<code>
node_id
</code>
</em>
- process exit
[state=
<em class="replaceable">
<code>
state_code
</code>
</em>
]
</code>
or
<code class="literal">
Lost arbitrator node
<em class="replaceable">
<code>
node_id
</code>
</em>
-
<em class="replaceable">
<code>
error_message
</code>
</em>
[state=
<em class="replaceable">
<code>
state_code
</code>
</em>
]
</code>
</th>
<td>
This is a report on the current state and progress of arbitration in the
cluster.
<em class="replaceable">
<code>
node_id
</code>
</em>
is the node ID
of the management node or SQL node selected as the
arbitrator.
<em class="replaceable">
<code>
state_code
</code>
</em>
is an
arbitration state code, as found in
<code class="filename">
include/kernel/signaldata/ArbitSignalData.hpp
</code>
.
When an error has occurred, an
<em class="replaceable">
<code>
error_message
</code>
</em>
, also defined in
<code class="filename">
ArbitSignalData.hpp
</code>
, is provided.
<em class="replaceable">
<code>
ticket_id
</code>
</em>
is a unique
identifier handed out by the arbitrator when it is
selected to all the nodes that participated in its
selection; this is used to ensure that each node
requesting arbitration was one of the nodes that took part
in the selection process.
</td>
<td>
<code class="literal">
ArbitState
</code>
</td>
<td>
<code class="literal">
NodeRestart
</code>
</td>
<td>
6
</td>
<td>
<code class="literal">
INFO
</code>
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
Arbitration check lost - less than 1/2 nodes left
</code>
or
<code class="literal">
Arbitration check won - all node groups and more
than 1/2 nodes left
</code>
or
<code class="literal">
Arbitration
check won - node group majority
</code>
or
<code class="literal">
Arbitration check lost - missing node
group
</code>
or
<code class="literal">
Network partitioning -
arbitration required
</code>
or
<code class="literal">
Arbitration won
- positive reply from node
<em class="replaceable">
<code>
node_id
</code>
</em>
</code>
or
<code class="literal">
Arbitration lost - negative reply from node
<em class="replaceable">
<code>
node_id
</code>
</em>
</code>
or
<code class="literal">
Network partitioning - no arbitrator
available
</code>
or
<code class="literal">
Network partitioning - no
arbitrator configured
</code>
or
<code class="literal">
Arbitration
failure -
<em class="replaceable">
<code>
error_message
</code>
</em>
[state=
<em class="replaceable">
<code>
state_code
</code>
</em>
]
</code>
</th>
<td>
This message reports on the result of arbitration. In the event of
arbitration failure, an
<em class="replaceable">
<code>
error_message
</code>
</em>
and an
arbitration
<em class="replaceable">
<code>
state_code
</code>
</em>
are
provided; definitions for both of these are found in
<code class="filename">
include/kernel/signaldata/ArbitSignalData.hpp
</code>
.
</td>
<td>
<code class="literal">
ArbitResult
</code>
</td>
<td>
<code class="literal">
NodeRestart
</code>
</td>
<td>
2
</td>
<td>
<code class="literal">
ALERT
</code>
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
Node
<em class="replaceable">
<code>
node_id
</code>
</em>
: GCP Take over
started
</code>
</th>
<td>
This node is attempting to assume responsibility for the next global
checkpoint (that is, it is becoming the master node)
</td>
<td>
<code class="literal">
GCP_TakeoverStarted
</code>
</td>
<td>
<code class="literal">
NodeRestart
</code>
</td>
<td>
7
</td>
<td>
<code class="literal">
INFO
</code>
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
Node
<em class="replaceable">
<code>
node_id
</code>
</em>
: GCP Take over
completed
</code>
</th>
<td>
This node has become the master, and has assumed responsibility for the
next global checkpoint
</td>
<td>
<code class="literal">
GCP_TakeoverCompleted
</code>
</td>
<td>
<code class="literal">
NodeRestart
</code>
</td>
<td>
7
</td>
<td>
<code class="literal">
INFO
</code>
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
Node
<em class="replaceable">
<code>
node_id
</code>
</em>
: LCP Take over
started
</code>
</th>
<td>
This node is attempting to assume responsibility for the next set of
local checkpoints (that is, it is becoming the master
node)
</td>
<td>
<code class="literal">
LCP_TakeoverStarted
</code>
</td>
<td>
<code class="literal">
NodeRestart
</code>
</td>
<td>
7
</td>
<td>
<code class="literal">
INFO
</code>
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
Node
<em class="replaceable">
<code>
node_id
</code>
</em>
: LCP Take over
completed
</code>
</th>
<td>
This node has become the master, and has assumed responsibility for the
next set of local checkpoints
</td>
<td>
<code class="literal">
LCP_TakeoverCompleted
</code>
</td>
<td>
<code class="literal">
NodeRestart
</code>
</td>
<td>
7
</td>
<td>
<code class="literal">
INFO
</code>
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
Node
<em class="replaceable">
<code>
node_id
</code>
</em>
: Trans. Count =
<em class="replaceable">
<code>
transactions
</code>
</em>
, Commit Count =
<em class="replaceable">
<code>
commits
</code>
</em>
, Read Count =
<em class="replaceable">
<code>
reads
</code>
</em>
, Simple Read Count =
<em class="replaceable">
<code>
simple_reads
</code>
</em>
, Write Count =
<em class="replaceable">
<code>
writes
</code>
</em>
, AttrInfo Count =
<em class="replaceable">
<code>
AttrInfo_objects
</code>
</em>
, Concurrent
Operations =
<em class="replaceable">
<code>
concurrent_operations
</code>
</em>
, Abort
Count =
<em class="replaceable">
<code>
aborts
</code>
</em>
, Scans =
<em class="replaceable">
<code>
scans
</code>
</em>
, Range scans =
<em class="replaceable">
<code>
range_scans
</code>
</em>
</code>
</th>
<td>
This report of transaction activity is given approximately once every 10
seconds
</td>
<td>
<code class="literal">
TransReportCounters
</code>
</td>
<td>
<code class="literal">
Statistic
</code>
</td>
<td>
8
</td>
<td>
<code class="literal">
INFO
</code>
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
Node
<em class="replaceable">
<code>
node_id
</code>
</em>
:
Operations=
<em class="replaceable">
<code>
operations
</code>
</em>
</code>
</th>
<td>
Number of operations performed by this node, provided approximately once
every 10 seconds
</td>
<td>
<code class="literal">
OperationReportCounters
</code>
</td>
<td>
<code class="literal">
Statistic
</code>
</td>
<td>
8
</td>
<td>
<code class="literal">
INFO
</code>
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
Node
<em class="replaceable">
<code>
node_id
</code>
</em>
: Table with ID =
<em class="replaceable">
<code>
table_id
</code>
</em>
created
</code>
</th>
<td>
A table having the table ID shown has been created
</td>
<td>
<code class="literal">
TableCreated
</code>
</td>
<td>
<code class="literal">
Statistic
</code>
</td>
<td>
7
</td>
<td>
<code class="literal">
INFO
</code>
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
Node
<em class="replaceable">
<code>
node_id
</code>
</em>
: Mean loop Counter in
doJob last 8192 times =
<em class="replaceable">
<code>
count
</code>
</em>
</code>
</th>
<td>
</td>
<td>
<code class="literal">
JobStatistic
</code>
</td>
<td>
<code class="literal">
Statistic
</code>
</td>
<td>
9
</td>
<td>
<code class="literal">
INFO
</code>
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
Mean send size to Node =
<em class="replaceable">
<code>
node_id
</code>
</em>
last 4096 sends =
<em class="replaceable">
<code>
bytes
</code>
</em>
bytes
</code>
</th>
<td>
This node is sending an average of
<em class="replaceable">
<code>
bytes
</code>
</em>
bytes per send to node
<em class="replaceable">
<code>
node_id
</code>
</em>
</td>
<td>
<code class="literal">
SendBytesStatistic
</code>
</td>
<td>
<code class="literal">
Statistic
</code>
</td>
<td>
9
</td>
<td>
<code class="literal">
INFO
</code>
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
Mean receive size to Node =
<em class="replaceable">
<code>
node_id
</code>
</em>
last 4096 sends =
<em class="replaceable">
<code>
bytes
</code>
</em>
bytes
</code>
</th>
<td>
This node is receiving an average of
<em class="replaceable">
<code>
bytes
</code>
</em>
of
data each time it receives data from node
<em class="replaceable">
<code>
node_id
</code>
</em>
</td>
<td>
<code class="literal">
ReceiveBytesStatistic
</code>
</td>
<td>
<code class="literal">
Statistic
</code>
</td>
<td>
9
</td>
<td>
<code class="literal">
INFO
</code>
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
Node
<em class="replaceable">
<code>
node_id
</code>
</em>
: Data usage is
<em class="replaceable">
<code>
data_memory_percentage
</code>
</em>
%
(
<em class="replaceable">
<code>
data_pages_used
</code>
</em>
32K pages of
total
<em class="replaceable">
<code>
data_pages_total
</code>
</em>
)
</code>
/
<code class="literal">
Node
<em class="replaceable">
<code>
node_id
</code>
</em>
: Index
usage is
<em class="replaceable">
<code>
index_memory_percentage
</code>
</em>
%
(
<em class="replaceable">
<code>
index_pages_used
</code>
</em>
8K pages of
total
<em class="replaceable">
<code>
index_pages_total
</code>
</em>
)
</code>
</th>
<td>
This report is generated when a
<a class="ulink" href="/doc/ndb-internals/en/dump-command-1000.html" target="_top">
<code class="literal">
DUMP
1000
</code>
</a>
command is issued in the cluster management
client
</td>
<td>
<code class="literal">
MemoryUsage
</code>
</td>
<td>
<code class="literal">
Statistic
</code>
</td>
<td>
5
</td>
<td>
<code class="literal">
INFO
</code>
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
Node
<em class="replaceable">
<code>
node1_id
</code>
</em>
: Transporter to node
<em class="replaceable">
<code>
node2_id
</code>
</em>
reported error
<em class="replaceable">
<code>
error_code
</code>
</em>
:
<em class="replaceable">
<code>
error_message
</code>
</em>
</code>
</th>
<td>
A transporter error occurred while communicating with node
<em class="replaceable">
<code>
node2_id
</code>
</em>
; for a listing of
transporter error codes and messages, see
<a class="ulink" href="/doc/ndb-internals/en/ndb-transporter-errors.html" target="_top">
NDB Transporter Errors
</a>
, in
<a class="ulink" href="/doc/ndb-internals/en/" target="_top">
MySQL NDB Cluster Internals Manual
</a>
</td>
<td>
<code class="literal">
TransporterError
</code>
</td>
<td>
<code class="literal">
Error
</code>
</td>
<td>
2
</td>
<td>
<code class="literal">
ERROR
</code>
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
Node
<em class="replaceable">
<code>
node1_id
</code>
</em>
: Transporter to node
<em class="replaceable">
<code>
node2_id
</code>
</em>
reported error
<em class="replaceable">
<code>
error_code
</code>
</em>
:
<em class="replaceable">
<code>
error_message
</code>
</em>
</code>
</th>
<td>
A warning of a potential transporter problem while communicating with
node
<em class="replaceable">
<code>
node2_id
</code>
</em>
; for a listing of
transporter error codes and messages, see
<a class="ulink" href="/doc/ndb-internals/en/ndb-transporter-errors.html" target="_top">
NDB Transporter Errors
</a>
, for more
information
</td>
<td>
<code class="literal">
TransporterWarning
</code>
</td>
<td>
<code class="literal">
Error
</code>
</td>
<td>
8
</td>
<td>
<code class="literal">
WARNING
</code>
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
Node
<em class="replaceable">
<code>
node1_id
</code>
</em>
: Node
<em class="replaceable">
<code>
node2_id
</code>
</em>
missed heartbeat
<em class="replaceable">
<code>
heartbeat_id
</code>
</em>
</code>
</th>
<td>
This node missed a heartbeat from node
<em class="replaceable">
<code>
node2_id
</code>
</em>
</td>
<td>
<code class="literal">
MissedHeartbeat
</code>
</td>
<td>
<code class="literal">
Error
</code>
</td>
<td>
8
</td>
<td>
<code class="literal">
WARNING
</code>
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
Node
<em class="replaceable">
<code>
node1_id
</code>
</em>
: Node
<em class="replaceable">
<code>
node2_id
</code>
</em>
declared dead due to
missed heartbeat
</code>
</th>
<td>
This node has missed at least 3 heartbeats from node
<em class="replaceable">
<code>
node2_id
</code>
</em>
, and so has declared
that node
<span class="quote">
“
<span class="quote">
dead
</span>
”
</span>
</td>
<td>
<code class="literal">
DeadDueToHeartbeat
</code>
</td>
<td>
<code class="literal">
Error
</code>
</td>
<td>
8
</td>
<td>
<code class="literal">
ALERT
</code>
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
Node
<em class="replaceable">
<code>
node1_id
</code>
</em>
: Node Sent Heartbeat
to node =
<em class="replaceable">
<code>
node2_id
</code>
</em>
</code>
</th>
<td>
This node has sent a heartbeat to node
<em class="replaceable">
<code>
node2_id
</code>
</em>
</td>
<td>
<code class="literal">
SentHeartbeat
</code>
</td>
<td>
<code class="literal">
Info
</code>
</td>
<td>
12
</td>
<td>
<code class="literal">
INFO
</code>
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
Node
<em class="replaceable">
<code>
node_id
</code>
</em>
: Event buffer status
(
<em class="replaceable">
<code>
object_id
</code>
</em>
):
used=
<em class="replaceable">
<code>
bytes_used
</code>
</em>
(
<em class="replaceable">
<code>
percent_used
</code>
</em>
% of alloc)
alloc=
<em class="replaceable">
<code>
bytes_allocated
</code>
</em>
max=
<em class="replaceable">
<code>
bytes_available
</code>
</em>
latest_consumed_epoch=
<em class="replaceable">
<code>
latest_consumed_epoch
</code>
</em>
latest_buffered_epoch=
<em class="replaceable">
<code>
latest_buffered_epoch
</code>
</em>
report_reason=
<em class="replaceable">
<code>
report_reason
</code>
</em>
</code>
</th>
<td>
This report is seen during heavy event buffer usage, for example, when
many updates are being applied in a relatively short
period of time; the report shows the number of bytes and
the percentage of event buffer memory used, the bytes
allocated and percentage still available, and the latest
buffered and consumed epochs; for more information, see
<a class="xref" href="mysql-cluster-logs-event-buffer.html" title="25.6.2.3 Event Buffer Reporting in the Cluster Log">
Section 25.6.2.3, “Event Buffer Reporting in the Cluster Log”
</a>
</td>
<td>
<code class="literal">
EventBufferStatus2
</code>
</td>
<td>
<code class="literal">
Info
</code>
</td>
<td>
7
</td>
<td>
<code class="literal">
INFO
</code>
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
Node
<em class="replaceable">
<code>
node_id
</code>
</em>
: Entering single user
mode
</code>
,
<code class="literal">
Node
<em class="replaceable">
<code>
node_id
</code>
</em>
: Entered single user
mode Node
<em class="replaceable">
<code>
API_node_id
</code>
</em>
has
exclusive access
</code>
,
<code class="literal">
Node
<em class="replaceable">
<code>
node_id
</code>
</em>
: Entering single user
mode
</code>
</th>
<td>
These reports are written to the cluster log when entering and exiting
single user mode;
<em class="replaceable">
<code>
API_node_id
</code>
</em>
is the node ID of the API or SQL having exclusive access
to the cluster (for more information, see
<a class="xref" href="mysql-cluster-single-user-mode.html" title="25.6.6 NDB Cluster Single User Mode">
Section 25.6.6, “NDB Cluster Single User Mode”
</a>
); the
message
<code class="literal">
Unknown single user report
<em class="replaceable">
<code>
API_node_id
</code>
</em>
</code>
indicates
an error has taken place and should never be seen in
normal operation
</td>
<td>
<code class="literal">
SingleUser
</code>
</td>
<td>
<code class="literal">
Info
</code>
</td>
<td>
7
</td>
<td>
<code class="literal">
INFO
</code>
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
Node
<em class="replaceable">
<code>
node_id
</code>
</em>
: Backup
<em class="replaceable">
<code>
backup_id
</code>
</em>
started from node
<em class="replaceable">
<code>
mgm_node_id
</code>
</em>
</code>
</th>
<td>
A backup has been started using the management node having
<em class="replaceable">
<code>
mgm_node_id
</code>
</em>
; this message is
also displayed in the cluster management client when the
<a class="link" href="mysql-cluster-backup-using-management-client.html" title="25.6.8.2 Using The NDB Cluster Management Client to Create a Backup">
<code class="literal">
START BACKUP
</code>
</a>
command
is issued; for more information, see
<a class="xref" href="mysql-cluster-backup-using-management-client.html" title="25.6.8.2 Using The NDB Cluster Management Client to Create a Backup">
Section 25.6.8.2, “Using The NDB Cluster Management Client to Create a Backup”
</a>
</td>
<td>
<code class="literal">
BackupStarted
</code>
</td>
<td>
<code class="literal">
Backup
</code>
</td>
<td>
7
</td>
<td>
<code class="literal">
INFO
</code>
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
Node
<em class="replaceable">
<code>
node_id
</code>
</em>
: Backup
<em class="replaceable">
<code>
backup_id
</code>
</em>
started from node
<em class="replaceable">
<code>
mgm_node_id
</code>
</em>
completed.
StartGCP:
<em class="replaceable">
<code>
start_gcp
</code>
</em>
StopGCP:
<em class="replaceable">
<code>
stop_gcp
</code>
</em>
#Records:
<em class="replaceable">
<code>
records
</code>
</em>
#LogRecords:
<em class="replaceable">
<code>
log_records
</code>
</em>
Data:
<em class="replaceable">
<code>
data_bytes
</code>
</em>
bytes Log:
<em class="replaceable">
<code>
log_bytes
</code>
</em>
bytes
</code>
</th>
<td>
The backup having the ID
<em class="replaceable">
<code>
backup_id
</code>
</em>
has been
completed; for more information, see
<a class="xref" href="mysql-cluster-backup-using-management-client.html" title="25.6.8.2 Using The NDB Cluster Management Client to Create a Backup">
Section 25.6.8.2, “Using The NDB Cluster Management Client to Create a Backup”
</a>
</td>
<td>
<code class="literal">
BackupCompleted
</code>
</td>
<td>
<code class="literal">
Backup
</code>
</td>
<td>
7
</td>
<td>
<code class="literal">
INFO
</code>
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
Node
<em class="replaceable">
<code>
node_id
</code>
</em>
: Backup request from
<em class="replaceable">
<code>
mgm_node_id
</code>
</em>
failed to start.
Error:
<em class="replaceable">
<code>
error_code
</code>
</em>
</code>
</th>
<td>
The backup failed to start; for error codes, see
<a class="ulink" href="/doc/ndbapi/en/mgm-errors.html" target="_top">
MGM API Errors
</a>
</td>
<td>
<code class="literal">
BackupFailedToStart
</code>
</td>
<td>
<code class="literal">
Backup
</code>
</td>
<td>
7
</td>
<td>
<code class="literal">
ALERT
</code>
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
Node
<em class="replaceable">
<code>
node_id
</code>
</em>
: Backup
<em class="replaceable">
<code>
backup_id
</code>
</em>
started from
<em class="replaceable">
<code>
mgm_node_id
</code>
</em>
has been aborted.
Error:
<em class="replaceable">
<code>
error_code
</code>
</em>
</code>
</th>
<td>
The backup was terminated after starting, possibly due to user
intervention
</td>
<td>
<code class="literal">
BackupAborted
</code>
</td>
<td>
<code class="literal">
Backup
</code>
</td>
<td>
7
</td>
<td>
<code class="literal">
ALERT
</code>
</td>
</tr>
</tbody>
</table>
</div>
<div class="table-contents">
<table cellpadding="0" cellspacing="0" style="position: fixed; top: 0px; display: none; left: 401px; width: 1141px;">
<thead>
<tr>
<th scope="col" style="width: 349.812px;">
Log Message
</th>
<th scope="col" style="width: 357.891px;">
Description
</th>
<th scope="col" style="width: 210.141px;">
Event Name
</th>
<th scope="col" style="width: 96.3906px;">
Event Type
</th>
<th scope="col" style="width: 60.7031px;">
Priority
</th>
<th scope="col" style="width: 64.625px;">
Severity
</th>
</tr>
</thead>
</table>
</div>
</div>
<br class="table-break"/>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/non-typed-operators.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h2 class="title">
<a name="non-typed-operators">
</a>
14.4 Operators
</h2>
</div>
</div>
</div>
<div class="toc">
<dl class="toc">
<dt>
<span class="section">
<a href="operator-precedence.html">
14.4.1 Operator Precedence
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="comparison-operators.html">
14.4.2 Comparison Functions and Operators
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="logical-operators.html">
14.4.3 Logical Operators
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="assignment-operators.html">
14.4.4 Assignment Operators
</a>
</span>
</dt>
</dl>
</div>
<div class="table">
<a name="idm46045207782080">
</a>
<p class="title">
<b>
Table 14.3 Operators
</b>
</p>
<div class="table-contents">
<table frame="box" rules="all" summary="A reference that lists all operators.">
<colgroup>
<col style="width: 25%"/>
<col style="width: 62%"/>
<col style="width: 12%"/>
</colgroup>
<thead>
<tr>
<th>
Name
</th>
<th>
Description
</th>
<th>
Deprecated
</th>
</tr>
</thead>
<tbody>
<tr>
<th scope="row">
<a class="link" href="bit-functions.html#operator_bitwise-and">
<code class="literal">
&
</code>
</a>
</th>
<td>
Bitwise AND
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="comparison-operators.html#operator_greater-than">
<code class="literal">
>
</code>
</a>
</th>
<td>
Greater than operator
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="bit-functions.html#operator_right-shift">
<code class="literal">
>>
</code>
</a>
</th>
<td>
Right shift
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="comparison-operators.html#operator_greater-than-or-equal">
<code class="literal">
>=
</code>
</a>
</th>
<td>
Greater than or equal operator
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="comparison-operators.html#operator_less-than">
<code class="literal">
<
</code>
</a>
</th>
<td>
Less than operator
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="comparison-operators.html#operator_not-equal">
<code class="literal">
<>
</code>
,
<code class="literal">
!=
</code>
</a>
</th>
<td>
Not equal operator
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="bit-functions.html#operator_left-shift">
<code class="literal">
<<
</code>
</a>
</th>
<td>
Left shift
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="comparison-operators.html#operator_less-than-or-equal">
<code class="literal">
<=
</code>
</a>
</th>
<td>
Less than or equal operator
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="comparison-operators.html#operator_equal-to">
<code class="literal">
<=>
</code>
</a>
</th>
<td>
NULL-safe equal to operator
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="arithmetic-functions.html#operator_mod">
<code class="literal">
%
</code>
,
<code class="literal">
MOD
</code>
</a>
</th>
<td>
Modulo operator
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="arithmetic-functions.html#operator_times">
<code class="literal">
*
</code>
</a>
</th>
<td>
Multiplication operator
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="arithmetic-functions.html#operator_plus">
<code class="literal">
+
</code>
</a>
</th>
<td>
Addition operator
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="arithmetic-functions.html#operator_minus">
<code class="literal">
-
</code>
</a>
</th>
<td>
Minus operator
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="arithmetic-functions.html#operator_unary-minus">
<code class="literal">
-
</code>
</a>
</th>
<td>
Change the sign of the argument
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="json-search-functions.html#operator_json-column-path">
<code class="literal">
->
</code>
</a>
</th>
<td>
Return value from JSON column after evaluating path; equivalent to
JSON_EXTRACT().
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="json-search-functions.html#operator_json-inline-path">
<code class="literal">
->>
</code>
</a>
</th>
<td>
Return value from JSON column after evaluating path and unquoting
the result; equivalent to JSON_UNQUOTE(JSON_EXTRACT()).
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="arithmetic-functions.html#operator_divide">
<code class="literal">
/
</code>
</a>
</th>
<td>
Division operator
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="assignment-operators.html#operator_assign-value">
<code class="literal">
:=
</code>
</a>
</th>
<td>
Assign a value
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="assignment-operators.html#operator_assign-equal">
<code class="literal">
=
</code>
</a>
</th>
<td>
Assign a value (as part of a
<a class="link" href="set-variable.html" title="15.7.6.1 SET Syntax for Variable Assignment">
<code class="literal">
SET
</code>
</a>
statement, or as part of the
<code class="literal">
SET
</code>
clause in an
<a class="link" href="update.html" title="15.2.17 UPDATE Statement">
<code class="literal">
UPDATE
</code>
</a>
statement)
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="comparison-operators.html#operator_equal">
<code class="literal">
=
</code>
</a>
</th>
<td>
Equal operator
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="bit-functions.html#operator_bitwise-xor">
<code class="literal">
^
</code>
</a>
</th>
<td>
Bitwise XOR
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="logical-operators.html#operator_and">
<code class="literal">
AND
</code>
,
<code class="literal">
&&
</code>
</a>
</th>
<td>
Logical AND
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="comparison-operators.html#operator_between">
<code class="literal">
BETWEEN ... AND ...
</code>
</a>
</th>
<td>
Whether a value is within a range of values
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="cast-functions.html#operator_binary">
<code class="literal">
BINARY
</code>
</a>
</th>
<td>
Cast a string to a binary string
</td>
<td>
Yes
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="flow-control-functions.html#operator_case">
<code class="literal">
CASE
</code>
</a>
</th>
<td>
Case operator
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="arithmetic-functions.html#operator_div">
<code class="literal">
DIV
</code>
</a>
</th>
<td>
Integer division
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="comparison-operators.html#operator_exists">
<code class="literal">
EXISTS()
</code>
</a>
</th>
<td>
Whether the result of a query contains any rows
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="comparison-operators.html#operator_in">
<code class="literal">
IN()
</code>
</a>
</th>
<td>
Whether a value is within a set of values
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="comparison-operators.html#operator_is">
<code class="literal">
IS
</code>
</a>
</th>
<td>
Test a value against a boolean
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="comparison-operators.html#operator_is-not">
<code class="literal">
IS NOT
</code>
</a>
</th>
<td>
Test a value against a boolean
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="comparison-operators.html#operator_is-not-null">
<code class="literal">
IS NOT NULL
</code>
</a>
</th>
<td>
NOT NULL value test
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="comparison-operators.html#operator_is-null">
<code class="literal">
IS NULL
</code>
</a>
</th>
<td>
NULL value test
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="string-comparison-functions.html#operator_like">
<code class="literal">
LIKE
</code>
</a>
</th>
<td>
Simple pattern matching
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="json-search-functions.html#operator_member-of">
<code class="literal">
MEMBER OF()
</code>
</a>
</th>
<td>
Returns true (1) if first operand matches any element of JSON
array passed as second operand, otherwise returns false (0)
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="logical-operators.html#operator_not">
<code class="literal">
NOT
</code>
,
<code class="literal">
!
</code>
</a>
</th>
<td>
Negates value
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="comparison-operators.html#operator_not-between">
<code class="literal">
NOT BETWEEN ... AND ...
</code>
</a>
</th>
<td>
Whether a value is not within a range of values
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="comparison-operators.html#operator_not-exists">
<code class="literal">
NOT EXISTS()
</code>
</a>
</th>
<td>
Whether the result of a query contains no rows
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="comparison-operators.html#operator_not-in">
<code class="literal">
NOT IN()
</code>
</a>
</th>
<td>
Whether a value is not within a set of values
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="string-comparison-functions.html#operator_not-like">
<code class="literal">
NOT LIKE
</code>
</a>
</th>
<td>
Negation of simple pattern matching
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="regexp.html#operator_not-regexp">
<code class="literal">
NOT REGEXP
</code>
</a>
</th>
<td>
Negation of REGEXP
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="logical-operators.html#operator_or">
<code class="literal">
OR
</code>
,
<code class="literal">
||
</code>
</a>
</th>
<td>
Logical OR
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="regexp.html#operator_regexp">
<code class="literal">
REGEXP
</code>
</a>
</th>
<td>
Whether string matches regular expression
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="regexp.html#operator_regexp">
<code class="literal">
RLIKE
</code>
</a>
</th>
<td>
Whether string matches regular expression
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="string-functions.html#operator_sounds-like">
<code class="literal">
SOUNDS LIKE
</code>
</a>
</th>
<td>
Compare sounds
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="logical-operators.html#operator_xor">
<code class="literal">
XOR
</code>
</a>
</th>
<td>
Logical XOR
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="bit-functions.html#operator_bitwise-or">
<code class="literal">
|
</code>
</a>
</th>
<td>
Bitwise OR
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="bit-functions.html#operator_bitwise-invert">
<code class="literal">
~
</code>
</a>
</th>
<td>
Bitwise inversion
</td>
<td>
</td>
</tr>
</tbody>
</table>
</div>
<div class="table-contents">
<table cellpadding="0" cellspacing="0" style="position: fixed; top: 0px; display: none; left: 401px; width: 739px;">
<thead>
<tr>
<th style="width: 186.203px;">
Name
</th>
<th style="width: 461.797px;">
Description
</th>
<th style="width: 90px;">
Deprecated
</th>
</tr>
</thead>
</table>
</div>
</div>
<br class="table-break"/>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/obtaining-loadable-function-information.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="obtaining-loadable-function-information">
</a>
7.7.2 Obtaining Information About Loadable Functions
</h3>
</div>
</div>
</div>
<a class="indexterm" name="idm46045254153008">
</a>
<a class="indexterm" name="idm46045254151552">
</a>
<a class="indexterm" name="idm46045254150048">
</a>
<a class="indexterm" name="idm46045254148560">
</a>
<p>
The Performance Schema
<a class="link" href="performance-schema-user-defined-functions-table.html" title="29.12.22.10 The user_defined_functions Table">
<code class="literal">
user_defined_functions
</code>
</a>
table contains
information about the currently installed loadable functions:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa65710569"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SELECT</span> <span class="token operator">*</span> <span class="token keyword">FROM</span> performance_schema<span class="token punctuation">.</span>user_defined_functions<span class="token punctuation">;</span></code></pre>
</div>
<p>
The
<code class="literal">
mysql.func
</code>
system table also lists
installed loadable functions, but only those installed using
<a class="link" href="create-function-loadable.html" title="15.7.4.1 CREATE FUNCTION Statement for Loadable Functions">
<code class="literal">
CREATE
FUNCTION
</code>
</a>
. The
<a class="link" href="performance-schema-user-defined-functions-table.html" title="29.12.22.10 The user_defined_functions Table">
<code class="literal">
user_defined_functions
</code>
</a>
table lists
loadable functions installed using
<a class="link" href="create-function-loadable.html" title="15.7.4.1 CREATE FUNCTION Statement for Loadable Functions">
<code class="literal">
CREATE
FUNCTION
</code>
</a>
as well as loadable functions installed
automatically by components or plugins. This difference makes
<a class="link" href="performance-schema-user-defined-functions-table.html" title="29.12.22.10 The user_defined_functions Table">
<code class="literal">
user_defined_functions
</code>
</a>
preferable to
<code class="literal">
mysql.func
</code>
for checking which loadable
functions are installed. See
<a class="xref" href="performance-schema-user-defined-functions-table.html" title="29.12.22.10 The user_defined_functions Table">
Section 29.12.22.10, “The user_defined_functions Table”
</a>
.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/information-schema-role-column-grants-table.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="information-schema-role-column-grants-table">
</a>
28.3.27 The INFORMATION_SCHEMA ROLE_COLUMN_GRANTS Table
</h3>
</div>
</div>
</div>
<a class="indexterm" name="idm46045078982256">
</a>
<p>
The
<a class="link" href="information-schema-role-column-grants-table.html" title="28.3.27 The INFORMATION_SCHEMA ROLE_COLUMN_GRANTS Table">
<code class="literal">
ROLE_COLUMN_GRANTS
</code>
</a>
table provides
information about the column privileges for roles that are
available to or granted by the currently enabled roles.
</p>
<p>
The
<a class="link" href="information-schema-role-column-grants-table.html" title="28.3.27 The INFORMATION_SCHEMA ROLE_COLUMN_GRANTS Table">
<code class="literal">
ROLE_COLUMN_GRANTS
</code>
</a>
table has
these columns:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<code class="literal">
GRANTOR
</code>
</p>
<p>
The user name part of the account that granted the role.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
GRANTOR_HOST
</code>
</p>
<p>
The host name part of the account that granted the role.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
GRANTEE
</code>
</p>
<p>
The user name part of the account to which the role is
granted.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
GRANTEE_HOST
</code>
</p>
<p>
The host name part of the account to which the role is
granted.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
TABLE_CATALOG
</code>
</p>
<p>
The name of the catalog to which the role applies. This value
is always
<code class="literal">
def
</code>
.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
TABLE_SCHEMA
</code>
</p>
<p>
The name of the schema (database) to which the role applies.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
TABLE_NAME
</code>
</p>
<p>
The name of the table to which the role applies.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
COLUMN_NAME
</code>
</p>
<p>
The name of the column to which the role applies.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
PRIVILEGE_TYPE
</code>
</p>
<p>
The privilege granted. The value can be any privilege that can
be granted at the column level; see
<a class="xref" href="grant.html" title="15.7.1.6 GRANT Statement">
Section 15.7.1.6, “GRANT Statement”
</a>
.
Each row lists a single privilege, so there is one row per
column privilege held by the grantee.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
IS_GRANTABLE
</code>
</p>
<p>
<code class="literal">
YES
</code>
or
<code class="literal">
NO
</code>
, depending on
whether the role is grantable to other accounts.
</p>
</li>
</ul>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/spatial-type-overview.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="spatial-type-overview">
</a>
13.4.1 Spatial Data Types
</h3>
</div>
</div>
</div>
<a class="indexterm" name="idm46045212175648">
</a>
<a class="indexterm" name="idm46045212174576">
</a>
<a class="indexterm" name="idm46045212173504">
</a>
<a class="indexterm" name="idm46045212172432">
</a>
<a class="indexterm" name="idm46045212171360">
</a>
<a class="indexterm" name="idm46045212170288">
</a>
<a class="indexterm" name="idm46045212169200">
</a>
<a class="indexterm" name="idm46045212168128">
</a>
<a class="indexterm" name="idm46045212167040">
</a>
<a class="indexterm" name="idm46045212165552">
</a>
<a class="indexterm" name="idm46045212164064">
</a>
<a class="indexterm" name="idm46045212162576">
</a>
<a class="indexterm" name="idm46045212161088">
</a>
<a class="indexterm" name="idm46045212159600">
</a>
<a class="indexterm" name="idm46045212158112">
</a>
<a class="indexterm" name="idm46045212156624">
</a>
<a class="indexterm" name="idm46045212155136">
</a>
<a class="indexterm" name="idm46045212153648">
</a>
<p>
MySQL has spatial data types that correspond to OpenGIS classes.
The basis for these types is described in
<a class="xref" href="opengis-geometry-model.html" title="13.4.2 The OpenGIS Geometry Model">
Section 13.4.2, “The OpenGIS Geometry Model”
</a>
.
</p>
<p>
Some spatial data types hold single geometry values:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<code class="literal">
GEOMETRY
</code>
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
POINT
</code>
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
LINESTRING
</code>
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
POLYGON
</code>
</p>
</li>
</ul>
</div>
<p>
<code class="literal">
GEOMETRY
</code>
can store geometry values of any
type. The other single-value types (
<code class="literal">
POINT
</code>
,
<code class="literal">
LINESTRING
</code>
, and
<code class="literal">
POLYGON
</code>
)
restrict their values to a particular geometry type.
</p>
<p>
The other spatial data types hold collections of values:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<code class="literal">
MULTIPOINT
</code>
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
MULTILINESTRING
</code>
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
MULTIPOLYGON
</code>
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
GEOMETRYCOLLECTION
</code>
</p>
</li>
</ul>
</div>
<p>
<code class="literal">
GEOMETRYCOLLECTION
</code>
can store a collection of
objects of any type. The other collection types
(
<code class="literal">
MULTIPOINT
</code>
,
<code class="literal">
MULTILINESTRING
</code>
, and
<code class="literal">
MULTIPOLYGON
</code>
) restrict collection members to
those having a particular geometry type.
</p>
<p>
Example: To create a table named
<code class="literal">
geom
</code>
that
has a column named
<code class="literal">
g
</code>
that can store values of
any geometry type, use this statement:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa6408629"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">TABLE</span> geom <span class="token punctuation">(</span>g <span class="token keyword">GEOMETRY</span><span class="token punctuation">)</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
Columns with a spatial data type can have an
<code class="literal">
SRID
</code>
attribute, to explicitly indicate the
spatial reference system (SRS) for values stored in the column.
For example:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa63676419"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">TABLE</span> geom <span class="token punctuation">(</span>
p <span class="token keyword">POINT</span> <span class="token keyword">SRID</span> <span class="token number">0</span><span class="token punctuation">,</span>
g <span class="token keyword">GEOMETRY</span> <span class="token operator">NOT</span> <span class="token boolean">NULL</span> <span class="token keyword">SRID</span> <span class="token number">4326</span>
<span class="token punctuation">)</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
<code class="literal">
SPATIAL
</code>
indexes can be created on spatial
columns if they are
<code class="literal">
NOT NULL
</code>
and have a
specific SRID, so if you plan to index the column, declare it
with the
<code class="literal">
NOT NULL
</code>
and
<code class="literal">
SRID
</code>
attributes:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa1679370"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">TABLE</span> geom <span class="token punctuation">(</span>g <span class="token keyword">GEOMETRY</span> <span class="token operator">NOT</span> <span class="token boolean">NULL</span> <span class="token keyword">SRID</span> <span class="token number">4326</span><span class="token punctuation">)</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
<code class="literal">
InnoDB
</code>
tables permit
<code class="literal">
SRID
</code>
values for Cartesian and geographic SRSs.
<code class="literal">
MyISAM
</code>
tables permit
<code class="literal">
SRID
</code>
values for Cartesian SRSs.
</p>
<p>
The
<code class="literal">
SRID
</code>
attribute makes a spatial column
SRID-restricted, which has these implications:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
The column can contain only values with the given SRID.
Attempts to insert values with a different SRID produce an
error.
</p>
</li>
<li class="listitem">
<p>
The optimizer can use
<code class="literal">
SPATIAL
</code>
indexes on
the column. See
<a class="xref" href="spatial-index-optimization.html" title="10.3.3 SPATIAL Index Optimization">
Section 10.3.3, “SPATIAL Index Optimization”
</a>
.
</p>
</li>
</ul>
</div>
<p>
Spatial columns with no
<code class="literal">
SRID
</code>
attribute are
not SRID-restricted and accept values with any SRID. However,
the optimizer cannot use
<code class="literal">
SPATIAL
</code>
indexes on
them until the column definition is modified to include an
<code class="literal">
SRID
</code>
attribute, which may require that the
column contents first be modified so that all values have the
same SRID.
</p>
<p>
For other examples showing how to use spatial data types in
MySQL, see
<a class="xref" href="creating-spatial-columns.html" title="13.4.6 Creating Spatial Columns">
Section 13.4.6, “Creating Spatial Columns”
</a>
. For
information about spatial reference systems, see
<a class="xref" href="spatial-reference-systems.html" title="13.4.5 Spatial Reference System Support">
Section 13.4.5, “Spatial Reference System Support”
</a>
.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/sys-host-summary-by-file-io.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="sys-host-summary-by-file-io">
</a>
30.4.3.2 The host_summary_by_file_io and x$host_summary_by_file_io Views
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045063330144">
</a>
<a class="indexterm" name="idm46045063328688">
</a>
<a class="indexterm" name="idm46045063327184">
</a>
<a class="indexterm" name="idm46045063325680">
</a>
<p>
These views summarize file I/O, grouped by host. By default,
rows are sorted by descending total file I/O latency.
</p>
<p>
The
<a class="link" href="sys-host-summary-by-file-io.html" title="30.4.3.2 The host_summary_by_file_io and x$host_summary_by_file_io Views">
<code class="literal">
host_summary_by_file_io
</code>
</a>
and
<a class="link" href="sys-host-summary-by-file-io.html" title="30.4.3.2 The host_summary_by_file_io and x$host_summary_by_file_io Views">
<code class="literal">
x$host_summary_by_file_io
</code>
</a>
views
have these columns:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<code class="literal">
host
</code>
</p>
<p>
The host from which the client connected. Rows for which
the
<code class="literal">
HOST
</code>
column in the underlying
Performance Schema table is
<code class="literal">
NULL
</code>
are
assumed to be for background threads and are reported with
a host name of
<code class="literal">
background
</code>
.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
ios
</code>
</p>
<p>
The total number of file I/O events for the host.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
io_latency
</code>
</p>
<p>
The total wait time of timed file I/O events for the host.
</p>
</li>
</ul>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/upgrading.html | <div id="docs-body">
<div class="chapter">
<div class="titlepage">
<div>
<div>
<h1 class="title">
<a name="upgrading">
</a>
Chapter 3 Upgrading MySQL
</h1>
</div>
</div>
</div>
<div class="toc">
<p>
<b>
Table of Contents
</b>
</p>
<dl class="toc">
<dt>
<span class="section">
<a href="upgrade-before-you-begin.html">
3.1 Before You Begin
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="upgrade-paths.html">
3.2 Upgrade Paths
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="upgrade-best-practices.html">
3.3 Upgrade Best Practices
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="upgrading-what-is-upgraded.html">
3.4 What the MySQL Upgrade Process Upgrades
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="upgrading-from-previous-series.html">
3.5 Changes in MySQL 8.4
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="upgrade-prerequisites.html">
3.6 Preparing Your Installation for Upgrade
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="upgrade-binary-package.html">
3.7 Upgrading MySQL Binary or Package-based Installations on Unix/Linux
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="updating-yum-repo.html">
3.8 Upgrading MySQL with the MySQL Yum Repository
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="updating-apt-repo.html">
3.9 Upgrading MySQL with the MySQL APT Repository
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="updating-sles-repo.html">
3.10 Upgrading MySQL with the MySQL SLES Repository
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="windows-upgrading.html">
3.11 Upgrading MySQL on Windows
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="upgrade-docker-mysql.html">
3.12 Upgrading a Docker Installation of MySQL
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="upgrade-troubleshooting.html">
3.13 Upgrade Troubleshooting
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="rebuilding-tables.html">
3.14 Rebuilding or Repairing Tables or Indexes
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="copying-databases.html">
3.15 Copying MySQL Databases to Another Machine
</a>
</span>
</dt>
</dl>
</div>
<a class="indexterm" name="idm46045326421536">
</a>
<p>
This chapter describes the steps to upgrade a MySQL installation.
</p>
<p>
Upgrading is a common procedure, as you pick up bug fixes within the
same MySQL release series or significant features between major
MySQL releases. You perform this procedure first on some test
systems to make sure everything works smoothly, and then on the
production systems.
</p>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
In the following discussion, MySQL commands that must be run using
a MySQL account with administrative privileges include
<code class="option">
-u
<code class="literal">
root
</code>
</code>
on the command line to specify
the MySQL
<code class="literal">
root
</code>
user. Commands that require a
password for
<code class="literal">
root
</code>
also include a
<code class="option">
-p
</code>
option. Because
<code class="option">
-p
</code>
is
followed by no option value, such commands prompt for the
password. Type the password when prompted and press Enter.
</p>
<p>
SQL statements can be executed using the
<a class="link" href="mysql.html" title="6.5.1 mysql — The MySQL Command-Line Client">
<span class="command">
<strong>
mysql
</strong>
</span>
</a>
command-line client (connect as
<code class="literal">
root
</code>
to ensure
that you have the necessary privileges).
</p>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/storage-engines-other.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h2 class="title">
<a name="storage-engines-other">
</a>
18.10 Other Storage Engines
</h2>
</div>
</div>
</div>
<p>
Other storage engines may be available from third parties and
community members that have used the Custom Storage Engine
interface.
</p>
<p>
Third party engines are not supported by MySQL. For further
information, documentation, installation guides, bug reporting or
for any help or assistance with these engines, please contact the
developer of the engine directly.
</p>
<p>
For more information on developing a customer storage engine that
can be used with the Pluggable Storage Engine Architecture, see
<a class="ulink" href="/doc/internals/en/custom-engine.html" target="_top">
MySQL
Internals: Writing a Custom Storage Engine
</a>
.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/upgrade-binary-package.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h2 class="title">
<a name="upgrade-binary-package">
</a>
3.7 Upgrading MySQL Binary or Package-based Installations on Unix/Linux
</h2>
</div>
</div>
</div>
<p>
This section describes how to upgrade MySQL binary and
package-based installations on Unix/Linux. In-place and logical
upgrade methods are described.
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<a class="xref" href="upgrade-binary-package.html#upgrade-procedure-inplace" title="In-Place Upgrade">
In-Place Upgrade
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="upgrade-binary-package.html#upgrade-procedure-logical" title="Logical Upgrade">
Logical Upgrade
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="upgrade-binary-package.html#upgrading-cluster" title="MySQL Cluster Upgrade">
MySQL Cluster Upgrade
</a>
</p>
</li>
</ul>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h3 class="title">
<a name="upgrade-procedure-inplace">
</a>
In-Place Upgrade
</h3>
</div>
</div>
</div>
<p>
An in-place upgrade involves shutting down the old MySQL server,
replacing the old MySQL binaries or packages with the new ones,
restarting MySQL on the existing data directory, and upgrading
any remaining parts of the existing installation that require
upgrading. For details about what may need upgrading, see
<a class="xref" href="upgrading-what-is-upgraded.html" title="3.4 What the MySQL Upgrade Process Upgrades">
Section 3.4, “What the MySQL Upgrade Process Upgrades”
</a>
.
</p>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
If you are upgrading an installation originally produced by
installing multiple RPM packages, upgrade all the packages,
not just some. For example, if you previously installed the
server and client RPMs, do not upgrade just the server RPM.
</p>
<p>
For some Linux platforms, MySQL installation from RPM or
Debian packages includes systemd support for managing MySQL
server startup and shutdown. On these platforms,
<a class="link" href="mysqld-safe.html" title="6.3.2 mysqld_safe — MySQL Server Startup Script">
<span class="command">
<strong>
mysqld_safe
</strong>
</span>
</a>
is not installed. In such
cases, use systemd for server startup and shutdown instead of
the methods used in the following instructions. See
<a class="xref" href="using-systemd.html" title="2.5.9 Managing MySQL Server with systemd">
Section 2.5.9, “Managing MySQL Server with systemd”
</a>
.
</p>
<p>
For upgrades to MySQL Cluster installations, see also
<a class="xref" href="upgrade-binary-package.html#upgrading-cluster" title="MySQL Cluster Upgrade">
MySQL Cluster Upgrade
</a>
.
</p>
</div>
<p>
To perform an in-place upgrade:
</p>
<div class="orderedlist">
<ol class="orderedlist" type="1">
<li class="listitem">
<p>
Review the information in
<a class="xref" href="upgrade-before-you-begin.html" title="3.1 Before You Begin">
Section 3.1, “Before You Begin”
</a>
.
</p>
</li>
<li class="listitem">
<p>
Ensure the upgrade readiness of your installation by
completing the preliminary checks in
<a class="xref" href="upgrade-prerequisites.html" title="3.6 Preparing Your Installation for Upgrade">
Section 3.6, “Preparing Your Installation for Upgrade”
</a>
.
</p>
</li>
<li class="listitem">
<p>
If you use XA transactions with
<code class="literal">
InnoDB
</code>
,
run
<a class="link" href="xa-statements.html" title="15.3.8.1 XA Transaction SQL Statements">
<code class="literal">
XA
RECOVER
</code>
</a>
before upgrading to check for uncommitted
XA transactions. If results are returned, either commit or
rollback the XA transactions by issuing an
<a class="link" href="xa-statements.html" title="15.3.8.1 XA Transaction SQL Statements">
<code class="literal">
XA
COMMIT
</code>
</a>
or
<a class="link" href="xa-statements.html" title="15.3.8.1 XA Transaction SQL Statements">
<code class="literal">
XA
ROLLBACK
</code>
</a>
statement.
</p>
</li>
<li class="listitem">
<p>
If you normally run your MySQL server configured with
<a class="link" href="innodb-parameters.html#sysvar_innodb_fast_shutdown">
<code class="literal">
innodb_fast_shutdown
</code>
</a>
set to
<code class="literal">
2
</code>
(cold shutdown), configure it to
perform a fast or slow shutdown by executing either of these
statements:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa80129774"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SET</span> <span class="token keyword">GLOBAL</span> innodb_fast_shutdown <span class="token operator">=</span> <span class="token number">1</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">-- fast shutdown</span>
<span class="token keyword">SET</span> <span class="token keyword">GLOBAL</span> innodb_fast_shutdown <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">-- slow shutdown</span></code></pre>
</div>
<p>
With a fast or slow shutdown,
<code class="literal">
InnoDB
</code>
leaves its undo logs and data files in a state that can be
dealt with in case of file format differences between
releases.
</p>
</li>
<li class="listitem">
<p>
Shut down the old MySQL server. For example:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-terminal"><div class="docs-select-all right" id="sa41839456"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-terminal">mysqladmin <span class="token property">-u</span> root <span class="token property">-p</span> shutdown</code></pre>
</div>
</li>
<li class="listitem">
<p>
Upgrade the MySQL binaries or packages. If upgrading a
binary installation, unpack the new MySQL binary
distribution package. See
<a class="xref" href="binary-installation.html#binary-installation-unpack" title="Obtain and Unpack the Distribution">
Obtain and Unpack the Distribution
</a>
. For
package-based installations, install the new packages.
</p>
</li>
<li class="listitem">
<p>
Start the MySQL 8.4 server, using the existing
data directory. For example:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-terminal"><div class="docs-select-all right" id="sa60239283"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-terminal">mysqld_safe <span class="token constant">--user</span><span class="token attr-value"><span class="token punctuation">=</span>mysql</span> <span class="token constant">--datadir</span><span class="token attr-value"><span class="token punctuation">=</span><em class="replaceable">/path/to/existing-datadir</em></span> &</code></pre>
</div>
<p>
If there are encrypted
<code class="literal">
InnoDB
</code>
tablespaces, use the
<a class="link" href="server-options.html#option_mysqld_early-plugin-load">
<code class="option">
--early-plugin-load
</code>
</a>
option to
load the keyring plugin.
</p>
<p>
When you start the MySQL 8.4 server, it
automatically detects whether data dictionary tables are
present. If not, the server creates them in the data
directory, populates them with metadata, and then proceeds
with its normal startup sequence. During this process, the
server upgrades metadata for all database objects, including
databases, tablespaces, system and user tables, views, and
stored programs (stored procedures and functions, triggers,
and Event Scheduler events). The server also removes files
that previously were used for metadata storage. For example,
after upgrading from MySQL 8.3 to MySQL
8.4, you may notice that tables no longer have
<code class="filename">
.frm
</code>
files.
</p>
<p>
If this step fails, the server reverts all changes to the
data directory. In this case, you should remove all redo log
files, start your MySQL 8.3 server on the same
data directory, and fix the cause of any errors. Then
perform another slow shutdown of the 8.3
server and start the MySQL 8.4 server to try
again.
</p>
</li>
<li class="listitem">
<p>
In the previous step, the server upgrades the data
dictionary as necessary, making any changes required in the
<code class="literal">
mysql
</code>
system database between MySQL
8.3 and MySQL 8.4, so that you
can take advantage of new privileges or capabilities. It
also brings the Performance Schema,
<code class="literal">
INFORMATION_SCHEMA
</code>
, and
<code class="literal">
sys
</code>
databases up to date for MySQL
8.4, and examines all user databases for
incompatibilities with the current version of MySQL.
</p>
</li>
</ol>
</div>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
The upgrade process does not upgrade the contents of the time
zone tables. For upgrade instructions, see
<a class="xref" href="time-zone-support.html" title="7.1.15 MySQL Server Time Zone Support">
Section 7.1.15, “MySQL Server Time Zone Support”
</a>
.
</p>
</div>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h3 class="title">
<a name="upgrade-procedure-logical">
</a>
Logical Upgrade
</h3>
</div>
</div>
</div>
<p>
A logical upgrade involves exporting SQL from the old MySQL
instance using a backup or export utility such as
<a class="link" href="mysqldump.html" title="6.5.4 mysqldump — A Database Backup Program">
<span class="command">
<strong>
mysqldump
</strong>
</span>
</a>
, installing the new MySQL server,
and applying the SQL to your new MySQL instance. For details
about what may need upgrading, see
<a class="xref" href="upgrading-what-is-upgraded.html" title="3.4 What the MySQL Upgrade Process Upgrades">
Section 3.4, “What the MySQL Upgrade Process Upgrades”
</a>
.
</p>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
For some Linux platforms, MySQL installation from RPM or
Debian packages includes systemd support for managing MySQL
server startup and shutdown. On these platforms,
<a class="link" href="mysqld-safe.html" title="6.3.2 mysqld_safe — MySQL Server Startup Script">
<span class="command">
<strong>
mysqld_safe
</strong>
</span>
</a>
is not installed. In such
cases, use systemd for server startup and shutdown instead of
the methods used in the following instructions. See
<a class="xref" href="using-systemd.html" title="2.5.9 Managing MySQL Server with systemd">
Section 2.5.9, “Managing MySQL Server with systemd”
</a>
.
</p>
</div>
<div class="warning" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Warning
</div>
<p>
Applying SQL extracted from a previous MySQL release to a new
MySQL release may result in errors due to incompatibilities
introduced by new, changed, deprecated, or removed features
and capabilities. Consequently, SQL extracted from a previous
MySQL release may require modification to enable a logical
upgrade.
</p>
<p>
To identify incompatibilities before upgrading to the latest
MySQL 8.4 release, perform the steps described in
<a class="xref" href="upgrade-prerequisites.html" title="3.6 Preparing Your Installation for Upgrade">
Section 3.6, “Preparing Your Installation for Upgrade”
</a>
.
</p>
</div>
<p>
To perform a logical upgrade:
</p>
<div class="orderedlist">
<ol class="orderedlist" type="1">
<li class="listitem">
<p>
Review the information in
<a class="xref" href="upgrade-before-you-begin.html" title="3.1 Before You Begin">
Section 3.1, “Before You Begin”
</a>
.
</p>
</li>
<li class="listitem">
<p>
Export your existing data from the previous MySQL
installation:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-terminal"><div class="docs-select-all right" id="sa6003869"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-terminal">mysqldump <span class="token property">-u</span> root <span class="token property">-p</span>
<span class="token property">--add-drop-table</span> <span class="token property">--routines</span> <span class="token property">--events</span>
<span class="token property">--all-databases</span> <span class="token property">--force</span> > data-for-upgrade<span class="token punctuation">.</span>sql</code></pre>
</div>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
Use the
<a class="link" href="mysqldump.html#option_mysqldump_routines">
<code class="option">
--routines
</code>
</a>
and
<a class="link" href="mysqldump.html#option_mysqldump_events">
<code class="option">
--events
</code>
</a>
options with
<a class="link" href="mysqldump.html" title="6.5.4 mysqldump — A Database Backup Program">
<span class="command">
<strong>
mysqldump
</strong>
</span>
</a>
(as shown above) if your
databases include stored programs. The
<a class="link" href="mysqldump.html#option_mysqldump_all-databases">
<code class="option">
--all-databases
</code>
</a>
option
includes all databases in the dump, including the
<code class="literal">
mysql
</code>
database that holds the system
tables.
</p>
</div>
<div class="important" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Important
</div>
<p>
If you have tables that contain generated columns, use the
<a class="link" href="mysqldump.html" title="6.5.4 mysqldump — A Database Backup Program">
<span class="command">
<strong>
mysqldump
</strong>
</span>
</a>
utility provided with MySQL
5.7.9 or higher to create your dump files. The
<a class="link" href="mysqldump.html" title="6.5.4 mysqldump — A Database Backup Program">
<span class="command">
<strong>
mysqldump
</strong>
</span>
</a>
utility provided in earlier
releases uses incorrect syntax for generated column
definitions (Bug #20769542). You can use the Information
Schema
<a class="link" href="information-schema-columns-table.html" title="28.3.8 The INFORMATION_SCHEMA COLUMNS Table">
<code class="literal">
COLUMNS
</code>
</a>
table to
identify tables with generated columns.
</p>
</div>
</li>
<li class="listitem">
<p>
Shut down the old MySQL server. For example:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-terminal"><div class="docs-select-all right" id="sa79385810"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-terminal">mysqladmin <span class="token property">-u</span> root <span class="token property">-p</span> shutdown</code></pre>
</div>
</li>
<li class="listitem">
<p>
Install MySQL 8.4. For installation
instructions, see
<a class="xref" href="installing.html" title="Chapter 2 Installing MySQL">
Chapter 2,
<i>
Installing MySQL
</i>
</a>
.
</p>
</li>
<li class="listitem">
<p>
Initialize a new data directory, as described in
<a class="xref" href="data-directory-initialization.html" title="2.9.1 Initializing the Data Directory">
Section 2.9.1, “Initializing the Data Directory”
</a>
. For
example:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-terminal"><div class="docs-select-all right" id="sa26439471"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-terminal">mysqld <span class="token property">--initialize</span> <span class="token constant">--datadir</span><span class="token attr-value"><span class="token punctuation">=</span><em class="replaceable">/path/to/8.4-datadir</em></span></code></pre>
</div>
<p>
Copy the temporary
<code class="literal">
'root'@'localhost'
</code>
password displayed to your screen or written to your error
log for later use.
</p>
</li>
<li class="listitem">
<p>
Start the MySQL 8.4 server, using the new data
directory. For example:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-terminal"><div class="docs-select-all right" id="sa26023672"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-terminal">mysqld_safe <span class="token constant">--user</span><span class="token attr-value"><span class="token punctuation">=</span>mysql</span> <span class="token constant">--datadir</span><span class="token attr-value"><span class="token punctuation">=</span><em class="replaceable">/path/to/8.4-datadir</em></span> &</code></pre>
</div>
</li>
<li class="listitem">
<p>
Reset the
<code class="literal">
root
</code>
password:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-terminal"><div class="docs-select-all right" id="sa58006044"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-terminal"><span class="token prompt">$> </span><span class="token command">mysql</span> <span class="token property">-u</span> root <span class="token property">-p</span>
Enter password<span class="token punctuation">:</span> **** <- enter temporary root password</code></pre>
</div>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa52898936"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">ALTER</span> <span class="token keyword">USER</span> <span class="token function">USER</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token keyword">IDENTIFIED</span> <span class="token keyword">BY</span> <span class="token string">'<em class="replaceable">your new password</em>'</span><span class="token punctuation">;</span></code></pre>
</div>
</li>
<li class="listitem">
<p>
Load the previously created dump file into the new MySQL
server. For example:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-terminal"><div class="docs-select-all right" id="sa91673434"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-terminal">mysql <span class="token property">-u</span> root <span class="token property">-p</span> <span class="token property">--force</span> < data-for-upgrade<span class="token punctuation">.</span>sql</code></pre>
</div>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
It is not recommended to load a dump file when GTIDs are
enabled on the server
(
<a class="link" href="replication-options-gtids.html#sysvar_gtid_mode">
<code class="literal">
gtid_mode=ON
</code>
</a>
), if your
dump file includes system tables.
<a class="link" href="mysqldump.html" title="6.5.4 mysqldump — A Database Backup Program">
<span class="command">
<strong>
mysqldump
</strong>
</span>
</a>
issues DML instructions for
the system tables which use the non-transactional MyISAM
storage engine, and this combination is not permitted when
GTIDs are enabled. Also be aware that loading a dump file
from a server with GTIDs enabled, into another server with
GTIDs enabled, causes different transaction identifiers to
be generated.
</p>
</div>
</li>
<li class="listitem">
<p>
Perform any remaining upgrade operations:
</p>
<p>
Shut down the server, then restart it with the
<a class="link" href="server-options.html#option_mysqld_upgrade">
<code class="option">
--upgrade=FORCE
</code>
</a>
option to
perform the remaining upgrade tasks:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-terminal"><div class="docs-select-all right" id="sa42298997"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-terminal">mysqladmin <span class="token property">-u</span> root <span class="token property">-p</span> shutdown
mysqld_safe <span class="token constant">--user</span><span class="token attr-value"><span class="token punctuation">=</span>mysql</span> <span class="token constant">--datadir</span><span class="token attr-value"><span class="token punctuation">=</span><em class="replaceable">/path/to/8.4-datadir</em></span> <span class="token constant">--upgrade</span><span class="token attr-value"><span class="token punctuation">=</span>FORCE</span> &</code></pre>
</div>
<p>
Upon restart with
<a class="link" href="server-options.html#option_mysqld_upgrade">
<code class="option">
--upgrade=FORCE
</code>
</a>
, the server
makes any changes required in the
<code class="literal">
mysql
</code>
system schema between MySQL 8.3 and MySQL
8.4, so that you can take advantage of new
privileges or capabilities. It also brings the Performance
Schema,
<code class="literal">
INFORMATION_SCHEMA
</code>
, and
<code class="literal">
sys
</code>
schema up to date for MySQL
8.4, and examines all user schemas for
incompatibilities with the current version of MySQL.
</p>
</li>
</ol>
</div>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
The upgrade process does not upgrade the contents of the time
zone tables. For upgrade instructions, see
<a class="xref" href="time-zone-support.html" title="7.1.15 MySQL Server Time Zone Support">
Section 7.1.15, “MySQL Server Time Zone Support”
</a>
.
</p>
</div>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h3 class="title">
<a name="upgrading-cluster">
</a>
MySQL Cluster Upgrade
</h3>
</div>
</div>
</div>
<p>
The information in this section is an adjunct to the in-place
upgrade procedure described in
<a class="xref" href="upgrade-binary-package.html#upgrade-procedure-inplace" title="In-Place Upgrade">
In-Place Upgrade
</a>
, for use if you are
upgrading MySQL Cluster.
</p>
<p>
A MySQL Cluster upgrade can be performed as a regular rolling
upgrade, following the usual three ordered steps:
</p>
<div class="orderedlist">
<ol class="orderedlist" type="1">
<li class="listitem">
<p>
Upgrade MGM nodes.
</p>
</li>
<li class="listitem">
<p>
Upgrade data nodes one at a time.
</p>
</li>
<li class="listitem">
<p>
Upgrade API nodes one at a time (including MySQL servers).
</p>
</li>
</ol>
</div>
<p>
There are two steps to upgrading each individual
<code class="literal">
mysqld
</code>
:
</p>
<div class="orderedlist">
<ol class="orderedlist" type="1">
<li class="listitem">
<p>
Import the data dictionary.
</p>
<p>
Start the new server with the
<a class="link" href="server-options.html#option_mysqld_upgrade">
<code class="option">
--upgrade=MINIMAL
</code>
</a>
option to
upgrade the data dictionary but not the system tables.
</p>
<p>
The MySQL server must be connected to
<code class="literal">
NDB
</code>
for this phase to complete. If any
<code class="literal">
NDB
</code>
or
<code class="literal">
NDBINFO
</code>
tables exist, and the server
cannot connect to the cluster, it exits with an error
message:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-none"><div class="docs-select-all right" id="sa79984991"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-none">Failed to Populate DD tables.</code></pre>
</div>
</li>
<li class="listitem">
<p>
Upgrade the system tables by restarting each individual
<a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
<span class="command">
<strong>
mysqld
</strong>
</span>
</a>
without the
<a class="link" href="server-options.html#option_mysqld_upgrade">
<code class="option">
--upgrade=MINIMAL
</code>
</a>
option.
</p>
</li>
</ol>
</div>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/extended-show.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h2 class="title">
<a name="extended-show">
</a>
28.8 Extensions to SHOW Statements
</h2>
</div>
</div>
</div>
<a class="indexterm" name="idm46045075919456">
</a>
<a class="indexterm" name="idm46045075918416">
</a>
<a class="indexterm" name="idm46045075917344">
</a>
<p>
Some extensions to
<a class="link" href="show.html" title="15.7.7 SHOW Statements">
<code class="literal">
SHOW
</code>
</a>
statements
accompany the implementation of
<code class="literal">
INFORMATION_SCHEMA
</code>
:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<a class="link" href="show.html" title="15.7.7 SHOW Statements">
<code class="literal">
SHOW
</code>
</a>
can be used to get
information about the structure of
<code class="literal">
INFORMATION_SCHEMA
</code>
itself.
</p>
</li>
<li class="listitem">
<p>
Several
<a class="link" href="show.html" title="15.7.7 SHOW Statements">
<code class="literal">
SHOW
</code>
</a>
statements accept
a
<code class="literal">
WHERE
</code>
clause that provides more
flexibility in specifying which rows to display.
</p>
</li>
</ul>
</div>
<p>
<code class="literal">
INFORMATION_SCHEMA
</code>
is an information database,
so its name is included in the output from
<a class="link" href="show-databases.html" title="15.7.7.15 SHOW DATABASES Statement">
<code class="literal">
SHOW DATABASES
</code>
</a>
. Similarly,
<a class="link" href="show-tables.html" title="15.7.7.39 SHOW TABLES Statement">
<code class="literal">
SHOW TABLES
</code>
</a>
can be used with
<code class="literal">
INFORMATION_SCHEMA
</code>
to obtain a list of its
tables:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa90213689"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SHOW</span> <span class="token keyword">TABLES</span> <span class="token keyword">FROM</span> INFORMATION_SCHEMA<span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> Tables_in_INFORMATION_SCHEMA <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> CHARACTER_SETS <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> COLLATIONS <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> COLLATION_CHARACTER_SET_APPLICABILITY <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> COLUMNS <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> COLUMN_PRIVILEGES <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> ENGINES <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> EVENTS <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> FILES <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> KEY_COLUMN_USAGE <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> PARTITIONS <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> PLUGINS <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> PROCESSLIST <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> REFERENTIAL_CONSTRAINTS <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> ROUTINES <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> SCHEMATA <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> SCHEMA_PRIVILEGES <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> STATISTICS <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> TABLES <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> TABLE_CONSTRAINTS <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> TABLE_PRIVILEGES <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> TRIGGERS <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> USER_PRIVILEGES <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> VIEWS <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
</div>
<p>
<a class="link" href="show-columns.html" title="15.7.7.6 SHOW COLUMNS Statement">
<code class="literal">
SHOW COLUMNS
</code>
</a>
and
<a class="link" href="describe.html" title="15.8.1 DESCRIBE Statement">
<code class="literal">
DESCRIBE
</code>
</a>
can display information
about the columns in individual
<code class="literal">
INFORMATION_SCHEMA
</code>
tables.
</p>
<p>
<a class="link" href="show.html" title="15.7.7 SHOW Statements">
<code class="literal">
SHOW
</code>
</a>
statements that accept a
<a class="link" href="string-comparison-functions.html#operator_like">
<code class="literal">
LIKE
</code>
</a>
clause to limit the rows
displayed also permit a
<code class="literal">
WHERE
</code>
clause that
specifies more general conditions that selected rows must satisfy:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa30284363"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SHOW</span> <span class="token keyword">CHARACTER</span> <span class="token keyword">SET</span>
<span class="token keyword">SHOW</span> <span class="token keyword">COLLATION</span>
<span class="token keyword">SHOW</span> <span class="token keyword">COLUMNS</span>
<span class="token keyword">SHOW</span> <span class="token keyword">DATABASES</span>
<span class="token keyword">SHOW</span> <span class="token keyword">FUNCTION</span> <span class="token keyword">STATUS</span>
<span class="token keyword">SHOW</span> <span class="token keyword">INDEX</span>
<span class="token keyword">SHOW</span> <span class="token keyword">OPEN</span> <span class="token keyword">TABLES</span>
<span class="token keyword">SHOW</span> <span class="token keyword">PROCEDURE</span> <span class="token keyword">STATUS</span>
<span class="token keyword">SHOW</span> <span class="token keyword">STATUS</span>
<span class="token keyword">SHOW</span> <span class="token keyword">TABLE</span> <span class="token keyword">STATUS</span>
<span class="token keyword">SHOW</span> <span class="token keyword">TABLES</span>
<span class="token keyword">SHOW</span> <span class="token keyword">TRIGGERS</span>
<span class="token keyword">SHOW</span> <span class="token keyword">VARIABLES</span></code></pre>
</div>
<p>
The
<code class="literal">
WHERE
</code>
clause, if present, is evaluated
against the column names displayed by the
<a class="link" href="show.html" title="15.7.7 SHOW Statements">
<code class="literal">
SHOW
</code>
</a>
statement. For example, the
<a class="link" href="show-character-set.html" title="15.7.7.4 SHOW CHARACTER SET Statement">
<code class="literal">
SHOW CHARACTER SET
</code>
</a>
statement
produces these output columns:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa98509662"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SHOW</span> <span class="token keyword">CHARACTER</span> <span class="token keyword">SET</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> Charset <span class="token punctuation">|</span> Description <span class="token punctuation">|</span> Default collation <span class="token punctuation">|</span> Maxlen <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> big5 <span class="token punctuation">|</span> Big5 Traditional Chinese <span class="token punctuation">|</span> big5_chinese_ci <span class="token punctuation">|</span> 2 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> dec8 <span class="token punctuation">|</span> DEC West European <span class="token punctuation">|</span> dec8_swedish_ci <span class="token punctuation">|</span> 1 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> cp850 <span class="token punctuation">|</span> DOS West European <span class="token punctuation">|</span> cp850_general_ci <span class="token punctuation">|</span> 1 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> hp8 <span class="token punctuation">|</span> HP West European <span class="token punctuation">|</span> hp8_english_ci <span class="token punctuation">|</span> 1 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> koi8r <span class="token punctuation">|</span> KOI8<span class="token punctuation">-</span>R Relcom Russian <span class="token punctuation">|</span> koi8r_general_ci <span class="token punctuation">|</span> 1 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> latin1 <span class="token punctuation">|</span> cp1252 West European <span class="token punctuation">|</span> latin1_swedish_ci <span class="token punctuation">|</span> 1 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> latin2 <span class="token punctuation">|</span> ISO 8859<span class="token punctuation">-</span>2 Central European <span class="token punctuation">|</span> latin2_general_ci <span class="token punctuation">|</span> 1 <span class="token punctuation">|</span></span>
<span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span></code></pre>
</div>
<p>
To use a
<code class="literal">
WHERE
</code>
clause with
<a class="link" href="show-character-set.html" title="15.7.7.4 SHOW CHARACTER SET Statement">
<code class="literal">
SHOW CHARACTER SET
</code>
</a>
, you would refer
to those column names. As an example, the following statement
displays information about character sets for which the default
collation contains the string
<code class="literal">
'japanese'
</code>
:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa75482124"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SHOW</span> <span class="token keyword">CHARACTER</span> <span class="token keyword">SET</span> <span class="token keyword">WHERE</span> <span class="token punctuation">`</span><span class="token keyword">Default</span> <span class="token keyword">collation</span><span class="token punctuation">`</span> <span class="token operator">LIKE</span> <span class="token string">'%japanese%'</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> Charset <span class="token punctuation">|</span> Description <span class="token punctuation">|</span> Default collation <span class="token punctuation">|</span> Maxlen <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> ujis <span class="token punctuation">|</span> EUC<span class="token punctuation">-</span>JP Japanese <span class="token punctuation">|</span> ujis_japanese_ci <span class="token punctuation">|</span> 3 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> sjis <span class="token punctuation">|</span> Shift<span class="token punctuation">-</span>JIS Japanese <span class="token punctuation">|</span> sjis_japanese_ci <span class="token punctuation">|</span> 2 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> cp932 <span class="token punctuation">|</span> SJIS for Windows Japanese <span class="token punctuation">|</span> cp932_japanese_ci <span class="token punctuation">|</span> 2 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> eucjpms <span class="token punctuation">|</span> UJIS for Windows Japanese <span class="token punctuation">|</span> eucjpms_japanese_ci <span class="token punctuation">|</span> 3 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
</div>
<p>
This statement displays the multibyte character sets:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa99040863"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SHOW</span> <span class="token keyword">CHARACTER</span> <span class="token keyword">SET</span> <span class="token keyword">WHERE</span> Maxlen <span class="token operator">></span> <span class="token number">1</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> Charset <span class="token punctuation">|</span> Description <span class="token punctuation">|</span> Default collation <span class="token punctuation">|</span> Maxlen <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> big5 <span class="token punctuation">|</span> Big5 Traditional Chinese <span class="token punctuation">|</span> big5_chinese_ci <span class="token punctuation">|</span> 2 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> cp932 <span class="token punctuation">|</span> SJIS for Windows Japanese <span class="token punctuation">|</span> cp932_japanese_ci <span class="token punctuation">|</span> 2 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> eucjpms <span class="token punctuation">|</span> UJIS for Windows Japanese <span class="token punctuation">|</span> eucjpms_japanese_ci <span class="token punctuation">|</span> 3 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> euckr <span class="token punctuation">|</span> EUC<span class="token punctuation">-</span>KR Korean <span class="token punctuation">|</span> euckr_korean_ci <span class="token punctuation">|</span> 2 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> gb18030 <span class="token punctuation">|</span> China National Standard GB18030 <span class="token punctuation">|</span> gb18030_chinese_ci <span class="token punctuation">|</span> 4 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> gb2312 <span class="token punctuation">|</span> GB2312 Simplified Chinese <span class="token punctuation">|</span> gb2312_chinese_ci <span class="token punctuation">|</span> 2 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> gbk <span class="token punctuation">|</span> GBK Simplified Chinese <span class="token punctuation">|</span> gbk_chinese_ci <span class="token punctuation">|</span> 2 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> sjis <span class="token punctuation">|</span> Shift<span class="token punctuation">-</span>JIS Japanese <span class="token punctuation">|</span> sjis_japanese_ci <span class="token punctuation">|</span> 2 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> ucs2 <span class="token punctuation">|</span> UCS<span class="token punctuation">-</span>2 Unicode <span class="token punctuation">|</span> ucs2_general_ci <span class="token punctuation">|</span> 2 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> ujis <span class="token punctuation">|</span> EUC<span class="token punctuation">-</span>JP Japanese <span class="token punctuation">|</span> ujis_japanese_ci <span class="token punctuation">|</span> 3 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> utf16 <span class="token punctuation">|</span> UTF<span class="token punctuation">-</span>16 Unicode <span class="token punctuation">|</span> utf16_general_ci <span class="token punctuation">|</span> 4 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> utf16le <span class="token punctuation">|</span> UTF<span class="token punctuation">-</span>16LE Unicode <span class="token punctuation">|</span> utf16le_general_ci <span class="token punctuation">|</span> 4 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> utf32 <span class="token punctuation">|</span> UTF<span class="token punctuation">-</span>32 Unicode <span class="token punctuation">|</span> utf32_general_ci <span class="token punctuation">|</span> 4 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> utf8mb3 <span class="token punctuation">|</span> UTF<span class="token punctuation">-</span>8 Unicode <span class="token punctuation">|</span> utf8mb3_general_ci <span class="token punctuation">|</span> 3 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> utf8mb4 <span class="token punctuation">|</span> UTF<span class="token punctuation">-</span>8 Unicode <span class="token punctuation">|</span> utf8mb4_0900_ai_ci <span class="token punctuation">|</span> 4 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/performance-schema-filtering-names.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="performance-schema-filtering-names">
</a>
29.4.9 Naming Instruments or Consumers for Filtering Operations
</h3>
</div>
</div>
</div>
<p>
Names given for filtering operations can be as specific or
general as required. To indicate a single instrument or
consumer, specify its name in full:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa68537600"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">UPDATE</span> performance_schema<span class="token punctuation">.</span>setup_instruments
<span class="token keyword">SET</span> ENABLED <span class="token operator">=</span> <span class="token string">'NO'</span>
<span class="token keyword">WHERE</span> <span class="token keyword">NAME</span> <span class="token operator">=</span> <span class="token string">'wait/synch/mutex/myisammrg/MYRG_INFO::mutex'</span><span class="token punctuation">;</span>
<span class="token keyword">UPDATE</span> performance_schema<span class="token punctuation">.</span>setup_consumers
<span class="token keyword">SET</span> ENABLED <span class="token operator">=</span> <span class="token string">'NO'</span>
<span class="token keyword">WHERE</span> <span class="token keyword">NAME</span> <span class="token operator">=</span> <span class="token string">'events_waits_current'</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
To specify a group of instruments or consumers, use a pattern
that matches the group members:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa16168913"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">UPDATE</span> performance_schema<span class="token punctuation">.</span>setup_instruments
<span class="token keyword">SET</span> ENABLED <span class="token operator">=</span> <span class="token string">'NO'</span>
<span class="token keyword">WHERE</span> <span class="token keyword">NAME</span> <span class="token operator">LIKE</span> <span class="token string">'wait/synch/mutex/%'</span><span class="token punctuation">;</span>
<span class="token keyword">UPDATE</span> performance_schema<span class="token punctuation">.</span>setup_consumers
<span class="token keyword">SET</span> ENABLED <span class="token operator">=</span> <span class="token string">'NO'</span>
<span class="token keyword">WHERE</span> <span class="token keyword">NAME</span> <span class="token operator">LIKE</span> <span class="token string">'%history%'</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
If you use a pattern, it should be chosen so that it matches all
the items of interest and no others. For example, to select all
file I/O instruments, it is better to use a pattern that
includes the entire instrument name prefix:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa91031700"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span> <span class="token keyword">WHERE</span> <span class="token keyword">NAME</span> <span class="token operator">LIKE</span> <span class="token string">'wait/io/file/%'</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
A pattern of
<code class="literal">
'%/file/%'
</code>
matches other
instruments that have an element of
<code class="literal">
'/file/'
</code>
anywhere in the name. Even less suitable is the pattern
<code class="literal">
'%file%'
</code>
because it matches instruments with
<code class="literal">
'file'
</code>
anywhere in the name, such as
<code class="literal">
wait/synch/mutex/innodb/file_open_mutex
</code>
.
</p>
<p>
To check which instrument or consumer names a pattern matches,
perform a simple test:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa27683217"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SELECT</span> <span class="token keyword">NAME</span> <span class="token keyword">FROM</span> performance_schema<span class="token punctuation">.</span>setup_instruments
<span class="token keyword">WHERE</span> <span class="token keyword">NAME</span> <span class="token operator">LIKE</span> <span class="token string">'<em class="replaceable">pattern</em>'</span><span class="token punctuation">;</span>
<span class="token keyword">SELECT</span> <span class="token keyword">NAME</span> <span class="token keyword">FROM</span> performance_schema<span class="token punctuation">.</span>setup_consumers
<span class="token keyword">WHERE</span> <span class="token keyword">NAME</span> <span class="token operator">LIKE</span> <span class="token string">'<em class="replaceable">pattern</em>'</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
For information about the types of names that are supported, see
<a class="xref" href="performance-schema-instrument-naming.html" title="29.6 Performance Schema Instrument Naming Conventions">
Section 29.6, “Performance Schema Instrument Naming Conventions”
</a>
.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/example-foreign-keys.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="example-foreign-keys">
</a>
5.6.6 Using Foreign Keys
</h3>
</div>
</div>
</div>
<a class="indexterm" name="idm46045324680736">
</a>
<a class="indexterm" name="idm46045324679664">
</a>
<p>
MySQL supports foreign keys, which permit cross-referencing
related data across tables, and foreign key constraints, which
help keep the related data consistent.
</p>
<p>
A foreign key relationship involves a parent table that holds
the initial column values, and a child table with column values
that reference the parent column values. A foreign key
constraint is defined on the child table.
</p>
<p>
This following example relates
<code class="literal">
parent
</code>
and
<code class="literal">
child
</code>
tables through a single-column foreign
key and shows how a foreign key constraint enforces referential
integrity.
</p>
<p>
Create the parent and child tables using the following SQL
statements:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa90722243"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">TABLE</span> parent <span class="token punctuation">(</span>
id <span class="token datatype">INT</span> <span class="token operator">NOT</span> <span class="token boolean">NULL</span><span class="token punctuation">,</span>
<span class="token keyword">PRIMARY</span> <span class="token keyword">KEY</span> <span class="token punctuation">(</span>id<span class="token punctuation">)</span>
<span class="token punctuation">)</span> <span class="token keyword">ENGINE</span><span class="token operator">=</span>INNODB<span class="token punctuation">;</span>
<span class="token keyword">CREATE</span> <span class="token keyword">TABLE</span> child <span class="token punctuation">(</span>
id <span class="token datatype">INT</span><span class="token punctuation">,</span>
parent_id <span class="token datatype">INT</span><span class="token punctuation">,</span>
<span class="token keyword">INDEX</span> par_ind <span class="token punctuation">(</span>parent_id<span class="token punctuation">)</span><span class="token punctuation">,</span>
<span class="token keyword">FOREIGN</span> <span class="token keyword">KEY</span> <span class="token punctuation">(</span>parent_id<span class="token punctuation">)</span>
<span class="token keyword">REFERENCES</span> parent<span class="token punctuation">(</span>id<span class="token punctuation">)</span>
<span class="token punctuation">)</span> <span class="token keyword">ENGINE</span><span class="token operator">=</span>INNODB<span class="token punctuation">;</span></code></pre>
</div>
<p>
Insert a row into the parent table, like this:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa3335116"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">INSERT</span> <span class="token keyword">INTO</span> parent <span class="token punctuation">(</span>id<span class="token punctuation">)</span> <span class="token keyword">VALUES</span> <span class="token keyword">ROW</span><span class="token punctuation">(</span><span class="token number">1</span><span class="token punctuation">)</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
Verify that the data was inserted. You can do this simply by
selecting all rows from
<code class="literal">
parent
</code>
, as shown
here:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa73073320"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">TABLE</span> parent<span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> id <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 1 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
</div>
<p>
Insert a row into the child table using the following SQL
statement:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa55900470"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">INSERT</span> <span class="token keyword">INTO</span> child <span class="token punctuation">(</span>id<span class="token punctuation">,</span>parent_id<span class="token punctuation">)</span> <span class="token keyword">VALUES</span> <span class="token keyword">ROW</span><span class="token punctuation">(</span><span class="token number">1</span><span class="token punctuation">,</span><span class="token number">1</span><span class="token punctuation">)</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
The insert operation is successful because
<code class="literal">
parent_id
</code>
1 is present in the parent table.
</p>
<p>
Insertion of a row into the child table with a
<code class="literal">
parent_id
</code>
value that is not present in the
parent table is rejected with an error, as you can see here:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa3616301"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">INSERT</span> <span class="token keyword">INTO</span> child <span class="token punctuation">(</span>id<span class="token punctuation">,</span>parent_id<span class="token punctuation">)</span> <span class="token keyword">VALUES</span> <span class="token keyword">ROW</span><span class="token punctuation">(</span><span class="token number">2</span><span class="token punctuation">,</span><span class="token number">2</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output">ERROR 1452 (23000)<span class="token punctuation">:</span> Cannot add or update a child row<span class="token punctuation">:</span> a foreign key constraint fails
(`test`.`child`, CONSTRAINT `child_ibfk_1` FOREIGN KEY (`parent_id`)
REFERENCES `parent` (`id`))</span></code></pre>
</div>
<p>
The operation fails because the specified
<code class="literal">
parent_id
</code>
value does not exist in the parent
table.
</p>
<p>
Trying to delete the previously inserted row from the parent
table also fails, as shown here:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa13175448"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">DELETE</span> <span class="token keyword">FROM</span> parent <span class="token keyword">WHERE</span> id <span class="token keyword">VALUES</span> <span class="token operator">=</span> <span class="token number">1</span><span class="token punctuation">;</span>
<span class="token output">ERROR 1451 (23000)<span class="token punctuation">:</span> Cannot delete or update a parent row<span class="token punctuation">:</span> a foreign key constraint fails
(`test`.`child`, CONSTRAINT `child_ibfk_1` FOREIGN KEY (`parent_id`)
REFERENCES `parent` (`id`))</span></code></pre>
</div>
<p>
This operation fails because the record in the child table
contains the referenced id (
<code class="literal">
parent_id
</code>
) value.
</p>
<p>
When an operation affects a key value in the parent table that
has matching rows in the child table, the result depends on the
referential action specified by
<code class="literal">
ON UPDATE
</code>
and
<code class="literal">
ON DELETE
</code>
subclauses of the
<code class="literal">
FOREIGN
KEY
</code>
clause. Omitting
<code class="literal">
ON DELETE
</code>
and
<code class="literal">
ON UPDATE
</code>
clauses (as in the current child
table definition) is the same as specifying the
<code class="literal">
RESTRICT
</code>
option, which rejects operations
that affect a key value in the parent table that has matching
rows in the parent table.
</p>
<p>
To demonstrate
<code class="literal">
ON DELETE
</code>
and
<code class="literal">
ON
UPDATE
</code>
referential actions, drop the child table and
recreate it to include
<code class="literal">
ON UPDATE
</code>
and
<code class="literal">
ON DELETE
</code>
subclauses with the
<code class="literal">
CASCADE
</code>
option. The
<code class="literal">
CASCADE
</code>
option automatically deletes or
updates matching rows in the child table when deleting or
updating rows in the parent table.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa46756594"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">DROP</span> <span class="token keyword">TABLE</span> child<span class="token punctuation">;</span>
<span class="token keyword">CREATE</span> <span class="token keyword">TABLE</span> child <span class="token punctuation">(</span>
id <span class="token datatype">INT</span><span class="token punctuation">,</span>
parent_id <span class="token datatype">INT</span><span class="token punctuation">,</span>
<span class="token keyword">INDEX</span> par_ind <span class="token punctuation">(</span>parent_id<span class="token punctuation">)</span><span class="token punctuation">,</span>
<span class="token keyword">FOREIGN</span> <span class="token keyword">KEY</span> <span class="token punctuation">(</span>parent_id<span class="token punctuation">)</span>
<span class="token keyword">REFERENCES</span> parent<span class="token punctuation">(</span>id<span class="token punctuation">)</span>
<span class="token keyword">ON</span> <span class="token keyword">UPDATE</span> <span class="token keyword">CASCADE</span>
<span class="token keyword">ON</span> <span class="token keyword">DELETE</span> <span class="token keyword">CASCADE</span>
<span class="token punctuation">)</span> <span class="token keyword">ENGINE</span><span class="token operator">=</span>INNODB<span class="token punctuation">;</span></code></pre>
</div>
<p>
Insert some rows into the child table using the statement shown
here:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa62005697"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">INSERT</span> <span class="token keyword">INTO</span> child <span class="token punctuation">(</span>id<span class="token punctuation">,</span>parent_id<span class="token punctuation">)</span> <span class="token keyword">VALUES</span> <span class="token keyword">ROW</span><span class="token punctuation">(</span><span class="token number">1</span><span class="token punctuation">,</span><span class="token number">1</span><span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token keyword">ROW</span><span class="token punctuation">(</span><span class="token number">2</span><span class="token punctuation">,</span><span class="token number">1</span><span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token keyword">ROW</span><span class="token punctuation">(</span><span class="token number">3</span><span class="token punctuation">,</span><span class="token number">1</span><span class="token punctuation">)</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
Verify that the data was inserted, like this:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa37123045"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">TABLE</span> child<span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> id <span class="token punctuation">|</span> parent_id <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 1 <span class="token punctuation">|</span> 1 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 2 <span class="token punctuation">|</span> 1 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 3 <span class="token punctuation">|</span> 1 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
</div>
<p>
Update the ID in the parent table, changing it from 1 to 2,
using the SQL statement shown here:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa37202509"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">UPDATE</span> parent <span class="token keyword">SET</span> id <span class="token operator">=</span> <span class="token number">2</span> <span class="token keyword">WHERE</span> id <span class="token operator">=</span> <span class="token number">1</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
Verify that the update was successful by selecting all rows from
the parent table, as shown here:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa80993186"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">TABLE</span> parent<span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> id <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 2 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
</div>
<p>
Verify that the
<code class="literal">
ON UPDATE CASCADE
</code>
referential
action updated the child table, like this:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa7791824"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">TABLE</span> child<span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> id <span class="token punctuation">|</span> parent_id <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 1 <span class="token punctuation">|</span> 2 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 2 <span class="token punctuation">|</span> 2 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 3 <span class="token punctuation">|</span> 2 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
</div>
<p>
To demonstrate the
<code class="literal">
ON DELETE CASCADE
</code>
referential action, delete records from the parent table where
<code class="literal">
parent_id = 2
</code>
; this deletes all records in
the parent table.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa25204273"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">DELETE</span> <span class="token keyword">FROM</span> parent <span class="token keyword">WHERE</span> id <span class="token operator">=</span> <span class="token number">2</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
Because all records in the child table are associated with
<code class="literal">
parent_id = 2
</code>
, the
<code class="literal">
ON DELETE
CASCADE
</code>
referential action removes all records from
the child table, as shown here:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa82073087"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">TABLE</span> child<span class="token punctuation">;</span>
<span class="token output">Empty set (0.00 sec)</span></code></pre>
</div>
<p>
For more information about foreign key constraints, see
<a class="xref" href="create-table-foreign-keys.html" title="15.1.20.5 FOREIGN KEY Constraints">
Section 15.1.20.5, “FOREIGN KEY Constraints”
</a>
.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/keyring.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="keyring">
</a>
8.4.4 The MySQL Keyring
</h3>
</div>
</div>
</div>
<div class="toc">
<dl class="toc">
<dt>
<span class="section">
<a href="keyring-component-plugin-comparison.html">
8.4.4.1 Keyring Components Versus Keyring Plugins
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="keyring-component-installation.html">
8.4.4.2 Keyring Component Installation
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="keyring-plugin-installation.html">
8.4.4.3 Keyring Plugin Installation
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="keyring-file-component.html">
8.4.4.4 Using the component_keyring_file File-Based Keyring Component
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="keyring-encrypted-file-component.html">
8.4.4.5 Using the component_keyring_encrypted_file Encrypted File-Based Keyring
Component
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="keyring-okv-plugin.html">
8.4.4.6 Using the keyring_okv KMIP Plugin
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="keyring-aws-plugin.html">
8.4.4.7 Using the keyring_aws Amazon Web Services Keyring Plugin
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="keyring-hashicorp-plugin.html">
8.4.4.8 Using the HashiCorp Vault Keyring Plugin
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="keyring-oci-component.html">
8.4.4.9 Using the Oracle Cloud Infrastructure Vault Keyring Component
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="keyring-key-types.html">
8.4.4.10 Supported Keyring Key Types and Lengths
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="keyring-key-migration.html">
8.4.4.11 Migrating Keys Between Keyring Keystores
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="keyring-functions-general-purpose.html">
8.4.4.12 General-Purpose Keyring Key-Management Functions
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="keyring-functions-plugin-specific.html">
8.4.4.13 Plugin-Specific Keyring Key-Management Functions
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="keyring-metadata.html">
8.4.4.14 Keyring Metadata
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="keyring-options.html">
8.4.4.15 Keyring Command Options
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="keyring-system-variables.html">
8.4.4.16 Keyring System Variables
</a>
</span>
</dt>
</dl>
</div>
<a class="indexterm" name="idm46045241058432">
</a>
<p>
MySQL Server supports a keyring that enables internal server
components and plugins to securely store sensitive information for
later retrieval. The implementation comprises these elements:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
Keyring components and plugins that manage a backing store or
communicate with a storage back end. Keyring use involves
installing one from among the available components and
plugins. Keyring components and plugins both manage keyring
data but are configured differently and may have operational
differences (see
<a class="xref" href="keyring-component-plugin-comparison.html" title="8.4.4.1 Keyring Components Versus Keyring Plugins">
Section 8.4.4.1, “Keyring Components Versus Keyring Plugins”
</a>
).
</p>
<p>
These keyring components are available:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
<code class="literal">
component_keyring_file
</code>
: Stores keyring
data in a file local to the server host. Available in
MySQL Community Edition and MySQL Enterprise Edition distributions. See
<a class="xref" href="keyring-file-component.html" title="8.4.4.4 Using the component_keyring_file File-Based Keyring Component">
Section 8.4.4.4, “Using the component_keyring_file File-Based Keyring Component”
</a>
.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
component_keyring_encrypted_file
</code>
:
Stores keyring data in an encrypted, password-protected
file local to the server host. Available in MySQL Enterprise Edition
distributions. See
<a class="xref" href="keyring-encrypted-file-component.html" title="8.4.4.5 Using the component_keyring_encrypted_file Encrypted File-Based Keyring Component">
Section 8.4.4.5, “Using the component_keyring_encrypted_file Encrypted File-Based Keyring
Component”
</a>
.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
component_keyring_oci
</code>
: Stores keyring
data in the Oracle Cloud Infrastructure Vault. Available in MySQL Enterprise Edition distributions.
See
<a class="xref" href="keyring-oci-component.html" title="8.4.4.9 Using the Oracle Cloud Infrastructure Vault Keyring Component">
Section 8.4.4.9, “Using the Oracle Cloud Infrastructure Vault Keyring Component”
</a>
.
</p>
</li>
</ul>
</div>
<p>
These keyring plugins are available:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
<code class="literal">
keyring_okv
</code>
: A KMIP 1.1 plugin for use
with KMIP-compatible back end keyring storage products
such as Oracle Key Vault and Gemalto SafeNet KeySecure
Appliance. Available in MySQL Enterprise Edition distributions. See
<a class="xref" href="keyring-okv-plugin.html" title="8.4.4.6 Using the keyring_okv KMIP Plugin">
Section 8.4.4.6, “Using the keyring_okv KMIP Plugin”
</a>
.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
keyring_aws
</code>
: Communicates with the
Amazon Web Services Key Management Service for key
generation and uses a local file for key storage.
Available in MySQL Enterprise Edition distributions. See
<a class="xref" href="keyring-aws-plugin.html" title="8.4.4.7 Using the keyring_aws Amazon Web Services Keyring Plugin">
Section 8.4.4.7, “Using the keyring_aws Amazon Web Services Keyring Plugin”
</a>
.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
keyring_hashicorp
</code>
: Communicates with
HashiCorp Vault for back end storage. Available in MySQL Enterprise Edition
distributions. See
<a class="xref" href="keyring-hashicorp-plugin.html" title="8.4.4.8 Using the HashiCorp Vault Keyring Plugin">
Section 8.4.4.8, “Using the HashiCorp Vault Keyring Plugin”
</a>
.
</p>
</li>
</ul>
</div>
</li>
<li class="listitem">
<p>
A keyring service interface for keyring key management. This
service is accessible at two levels:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
SQL interface: In SQL statements, call the functions
described in
<a class="xref" href="keyring-functions-general-purpose.html" title="8.4.4.12 General-Purpose Keyring Key-Management Functions">
Section 8.4.4.12, “General-Purpose Keyring Key-Management Functions”
</a>
.
</p>
</li>
<li class="listitem">
<p>
C interface: In C-language code, call the keyring service
functions described in
<a class="xref" href="keyring-service.html" title="7.6.9.2 The Keyring Service">
Section 7.6.9.2, “The Keyring Service”
</a>
.
</p>
</li>
</ul>
</div>
</li>
<li class="listitem">
<p>
Key metadata access:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
The Performance Schema
<a class="link" href="performance-schema-keyring-keys-table.html" title="29.12.18.2 The keyring_keys table">
<code class="literal">
keyring_keys
</code>
</a>
table exposes
metadata for keys in the keyring. Key metadata includes
key IDs, key owners, and backend key IDs. The
<a class="link" href="performance-schema-keyring-keys-table.html" title="29.12.18.2 The keyring_keys table">
<code class="literal">
keyring_keys
</code>
</a>
table does not
expose any sensitive keyring data such as key contents.
See
<a class="xref" href="performance-schema-keyring-keys-table.html" title="29.12.18.2 The keyring_keys table">
Section 29.12.18.2, “The keyring_keys table”
</a>
.
</p>
<a class="indexterm" name="idm46045241027792">
</a>
<a class="indexterm" name="idm46045241026304">
</a>
</li>
<li class="listitem">
<p>
The Performance Schema
<a class="link" href="performance-schema-keyring-component-status-table.html" title="29.12.18.1 The keyring_component_status Table">
<code class="literal">
keyring_component_status
</code>
</a>
table provides status information about the keyring
component in use, if one is installed. See
<a class="xref" href="performance-schema-keyring-component-status-table.html" title="29.12.18.1 The keyring_component_status Table">
Section 29.12.18.1, “The keyring_component_status Table”
</a>
.
</p>
<a class="indexterm" name="idm46045241021616">
</a>
<a class="indexterm" name="idm46045241020112">
</a>
</li>
</ul>
</div>
</li>
<li class="listitem">
<p>
A key migration capability. MySQL supports migration of keys
between keystores, enabling DBAs to switch a MySQL
installation from one keystore to another. See
<a class="xref" href="keyring-key-migration.html" title="8.4.4.11 Migrating Keys Between Keyring Keystores">
Section 8.4.4.11, “Migrating Keys Between Keyring Keystores”
</a>
.
</p>
</li>
<li class="listitem">
<p>
The implementation of keyring plugins is revised to use the
component infrastructure. This is facilitated using the
built-in plugin named
<code class="literal">
daemon_keyring_proxy_plugin
</code>
that acts as a
bridge between the plugin and component service APIs. See
<a class="xref" href="daemon-keyring-proxy-plugin.html" title="7.6.8 The Keyring Proxy Bridge Plugin">
Section 7.6.8, “The Keyring Proxy Bridge Plugin”
</a>
.
</p>
</li>
</ul>
</div>
<div class="warning" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Warning
</div>
<p>
For encryption key management, the
<code class="literal">
component_keyring_file
</code>
and
<code class="literal">
component_keyring_encrypted_file
</code>
components
are not intended as a regulatory compliance solution. Security
standards such as PCI, FIPS, and others require use of key
management systems to secure, manage, and protect encryption
keys in key vaults or hardware security modules (HSMs).
</p>
</div>
<p>
Within MySQL, keyring service consumers include:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
The
<code class="literal">
InnoDB
</code>
storage engine uses the keyring
to store its key for tablespace encryption. See
<a class="xref" href="innodb-data-encryption.html" title="17.13 InnoDB Data-at-Rest Encryption">
Section 17.13, “InnoDB Data-at-Rest Encryption”
</a>
.
</p>
</li>
<li class="listitem">
<p>
MySQL Enterprise Audit uses the keyring to store the audit log file
encryption password. See
<a class="xref" href="audit-log-logging-configuration.html#audit-log-file-encryption" title="Encrypting Audit Log Files">
Encrypting Audit Log Files
</a>
.
</p>
</li>
<li class="listitem">
<p>
Binary log and relay log management supports keyring-based
encryption of log files. With log file encryption activated,
the keyring stores the keys used to encrypt passwords for the
binary log files and relay log files. See
<a class="xref" href="replication-binlog-encryption.html" title="19.3.2 Encrypting Binary Log Files and Relay Log Files">
Section 19.3.2, “Encrypting Binary Log Files and Relay Log Files”
</a>
.
</p>
</li>
<li class="listitem">
<p>
The master key to decrypt the file key that decrypts the
persisted values of sensitive system variables is stored in
the keyring. A keyring component must be enabled on the MySQL
Server instance to support secure storage for persisted system
variable values, rather than a keyring plugin, which do not
support the function. See
<a class="xref" href="persisted-system-variables.html#persisted-system-variables-sensitive" title="Persisting Sensitive System Variables">
Persisting Sensitive System Variables
</a>
.
</p>
</li>
</ul>
</div>
<p>
For general keyring installation instructions, see
<a class="xref" href="keyring-component-installation.html" title="8.4.4.2 Keyring Component Installation">
Section 8.4.4.2, “Keyring Component Installation”
</a>
, and
<a class="xref" href="keyring-plugin-installation.html" title="8.4.4.3 Keyring Plugin Installation">
Section 8.4.4.3, “Keyring Plugin Installation”
</a>
. For installation
and configuration information specific to a given keyring
component or plugin, see the section describing it.
</p>
<p>
For information about using the keyring functions, see
<a class="xref" href="keyring-functions-general-purpose.html" title="8.4.4.12 General-Purpose Keyring Key-Management Functions">
Section 8.4.4.12, “General-Purpose Keyring Key-Management Functions”
</a>
.
</p>
<p>
Keyring components, plugins, and functions access a keyring
service that provides the interface to the keyring. For
information about accessing this service and writing keyring
plugins, see
<a class="xref" href="keyring-service.html" title="7.6.9.2 The Keyring Service">
Section 7.6.9.2, “The Keyring Service”
</a>
, and
<a class="ulink" href="/doc/extending-mysql/8.4/en/writing-keyring-plugins.html" target="_top">
Writing Keyring Plugins
</a>
.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/option-modifiers.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="option-modifiers">
</a>
6.2.2.4 Program Option Modifiers
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045323718528">
</a>
<a class="indexterm" name="idm46045323717072">
</a>
<a class="indexterm" name="idm46045323715728">
</a>
<a class="indexterm" name="idm46045323714240">
</a>
<a class="indexterm" name="idm46045323712896">
</a>
<a class="indexterm" name="idm46045323711408">
</a>
<a class="indexterm" name="idm46045323710064">
</a>
<a class="indexterm" name="idm46045323708576">
</a>
<a class="indexterm" name="idm46045323707232">
</a>
<a class="indexterm" name="idm46045323705744">
</a>
<a class="indexterm" name="idm46045323704400">
</a>
<a class="indexterm" name="idm46045323702912">
</a>
<p>
Some options are
<span class="quote">
“
<span class="quote">
boolean
</span>
”
</span>
and control behavior
that can be turned on or off. For example, the
<a class="link" href="mysql.html" title="6.5.1 mysql — The MySQL Command-Line Client">
<span class="command">
<strong>
mysql
</strong>
</span>
</a>
client supports a
<a class="link" href="mysql-command-options.html#option_mysql_column-names">
<code class="option">
--column-names
</code>
</a>
option that
determines whether or not to display a row of column names at
the beginning of query results. By default, this option is
enabled. However, you may want to disable it in some instances,
such as when sending the output of
<a class="link" href="mysql.html" title="6.5.1 mysql — The MySQL Command-Line Client">
<span class="command">
<strong>
mysql
</strong>
</span>
</a>
into
another program that expects to see only data and not an initial
header line.
</p>
<p>
To disable column names, you can specify the option using any of
these forms:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-terminal"><div class="docs-select-all right" id="sa16024440"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-terminal"><span class="token property">--disable-column-names</span>
<span class="token property">--skip-column-names</span>
<span class="token constant">--column-names</span><span class="token attr-value"><span class="token punctuation">=</span>0</span></code></pre>
</div>
<p>
The
<code class="option">
--disable
</code>
and
<code class="option">
--skip
</code>
prefixes and the
<code class="literal">
=0
</code>
suffix all have the same
effect: They turn the option off.
</p>
<p>
The
<span class="quote">
“
<span class="quote">
enabled
</span>
”
</span>
form of the option may be specified
in any of these ways:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-terminal"><div class="docs-select-all right" id="sa53023318"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-terminal"><span class="token property">--column-names</span>
<span class="token property">--enable-column-names</span>
<span class="token constant">--column-names</span><span class="token attr-value"><span class="token punctuation">=</span>1</span></code></pre>
</div>
<p>
The values
<code class="literal">
ON
</code>
,
<code class="literal">
TRUE
</code>
,
<code class="literal">
OFF
</code>
, and
<code class="literal">
FALSE
</code>
are also
recognized for boolean options (not case-sensitive).
</p>
<p>
If an option is prefixed by
<code class="option">
--loose
</code>
, a program
does not exit with an error if it does not recognize the option,
but instead issues only a warning:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-terminal"><div class="docs-select-all right" id="sa81748170"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-terminal"><span class="token prompt">$> </span><span class="token command">mysql</span> <span class="token property">--loose-no-such-option</span>
mysql<span class="token punctuation">:</span> WARNING<span class="token punctuation">:</span> unknown option <span class="token atrule">'--loose-no-such-option'</span></code></pre>
</div>
<p>
The
<code class="option">
--loose
</code>
prefix can be useful when you run
programs from multiple installations of MySQL on the same
machine and list options in an option file. An option that may
not be recognized by all versions of a program can be given
using the
<code class="option">
--loose
</code>
prefix (or
<code class="literal">
loose
</code>
in an option file). Versions of the
program that recognize the option process it normally, and
versions that do not recognize it issue a warning and ignore it.
</p>
<p>
The
<code class="option">
--maximum
</code>
prefix is available for
<a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
<span class="command">
<strong>
mysqld
</strong>
</span>
</a>
only and permits a limit to be placed
on how large client programs can set session system variables.
To do this, use a
<code class="option">
--maximum
</code>
prefix with the
variable name. For example,
<code class="option">
--maximum-max_heap_table_size=32M
</code>
prevents any
client from making the heap table size limit larger than 32M.
</p>
<p>
The
<code class="option">
--maximum
</code>
prefix is intended for use with
system variables that have a session value. If applied to a
system variable that has only a global value, an error occurs.
For example, with
<code class="option">
--maximum-back_log=200
</code>
, the
server produces this error:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-none"><div class="docs-select-all right" id="sa42119828"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-none">Maximum value of 'back_log' cannot be set</code></pre>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/table-locking.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="table-locking">
</a>
10.11.2 Table Locking Issues
</h3>
</div>
</div>
</div>
<a class="indexterm" name="idm46045222811344">
</a>
<p>
<code class="literal">
InnoDB
</code>
tables use row-level locking so that
multiple sessions and applications can read from and write to
the same table simultaneously, without making each other wait or
producing inconsistent results. For this storage engine, avoid
using the
<a class="link" href="lock-tables.html" title="15.3.6 LOCK TABLES and UNLOCK TABLES Statements">
<code class="literal">
LOCK TABLES
</code>
</a>
statement,
because it does not offer any extra protection, but instead
reduces concurrency. The automatic row-level locking makes these
tables suitable for your busiest databases with your most
important data, while also simplifying application logic since
you do not need to lock and unlock tables. Consequently, the
<code class="literal">
InnoDB
</code>
storage engine is the default in
MySQL.
</p>
<p>
MySQL uses table locking (instead of page, row, or column
locking) for all storage engines except
<code class="literal">
InnoDB
</code>
. The locking operations themselves do
not have much overhead. But because only one session can write
to a table at any one time, for best performance with these
other storage engines, use them primarily for tables that are
queried often and rarely inserted into or updated.
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<a class="xref" href="table-locking.html#table-locking-innodb" title="Performance Considerations Favoring InnoDB">
Performance Considerations Favoring InnoDB
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="table-locking.html#table-locking-workarounds" title="Workarounds for Locking Performance Issues">
Workarounds for Locking Performance Issues
</a>
</p>
</li>
</ul>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h4 class="title">
<a name="table-locking-innodb">
</a>
Performance Considerations Favoring InnoDB
</h4>
</div>
</div>
</div>
<p>
When choosing whether to create a table using
<code class="literal">
InnoDB
</code>
or a different storage engine, keep
in mind the following disadvantages of table locking:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
Table locking enables many sessions to read from a table
at the same time, but if a session wants to write to a
table, it must first get exclusive access, meaning it
might have to wait for other sessions to finish with the
table first. During the update, all other sessions that
want to access this particular table must wait until the
update is done.
</p>
</li>
<li class="listitem">
<p>
Table locking causes problems when a session is waiting
because the disk is full and free space needs to become
available before the session can proceed. In this case,
all sessions that want to access the problem table are
also put in a waiting state until more disk space is made
available.
</p>
</li>
<li class="listitem">
<p>
A
<a class="link" href="select.html" title="15.2.13 SELECT Statement">
<code class="literal">
SELECT
</code>
</a>
statement that
takes a long time to run prevents other sessions from
updating the table in the meantime, making the other
sessions appear slow or unresponsive. While a session is
waiting to get exclusive access to the table for updates,
other sessions that issue
<a class="link" href="select.html" title="15.2.13 SELECT Statement">
<code class="literal">
SELECT
</code>
</a>
statements queue up
behind it, reducing concurrency even for read-only
sessions.
</p>
</li>
</ul>
</div>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h4 class="title">
<a name="table-locking-workarounds">
</a>
Workarounds for Locking Performance Issues
</h4>
</div>
</div>
</div>
<p>
The following items describe some ways to avoid or reduce
contention caused by table locking:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
Consider switching the table to the
<code class="literal">
InnoDB
</code>
storage engine, either using
<code class="literal">
CREATE TABLE ... ENGINE=INNODB
</code>
during
setup, or using
<code class="literal">
ALTER TABLE ...
ENGINE=INNODB
</code>
for an existing table. See
<a class="xref" href="innodb-storage-engine.html" title="Chapter 17 The InnoDB Storage Engine">
Chapter 17,
<i>
The InnoDB Storage Engine
</i>
</a>
for more details
about this storage engine.
</p>
</li>
<li class="listitem">
<p>
Optimize
<a class="link" href="select.html" title="15.2.13 SELECT Statement">
<code class="literal">
SELECT
</code>
</a>
statements
to run faster so that they lock tables for a shorter time.
You might have to create some summary tables to do this.
</p>
</li>
<li class="listitem">
<p>
Start
<a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
<span class="command">
<strong>
mysqld
</strong>
</span>
</a>
with
<a class="link" href="server-system-variables.html#sysvar_low_priority_updates">
<code class="option">
--low-priority-updates
</code>
</a>
. For
storage engines that use only table-level locking (such as
<code class="literal">
MyISAM
</code>
,
<code class="literal">
MEMORY
</code>
, and
<code class="literal">
MERGE
</code>
), this gives all statements that
update (modify) a table lower priority than
<a class="link" href="select.html" title="15.2.13 SELECT Statement">
<code class="literal">
SELECT
</code>
</a>
statements. In this
case, the second
<a class="link" href="select.html" title="15.2.13 SELECT Statement">
<code class="literal">
SELECT
</code>
</a>
statement in the preceding scenario would execute before
the
<a class="link" href="update.html" title="15.2.17 UPDATE Statement">
<code class="literal">
UPDATE
</code>
</a>
statement, and
would not wait for the first
<a class="link" href="select.html" title="15.2.13 SELECT Statement">
<code class="literal">
SELECT
</code>
</a>
to finish.
</p>
</li>
<li class="listitem">
<p>
To specify that all updates issued in a specific
connection should be done with low priority, set the
<a class="link" href="server-system-variables.html#sysvar_low_priority_updates">
<code class="literal">
low_priority_updates
</code>
</a>
server system variable equal to 1.
</p>
</li>
<li class="listitem">
<p>
To give a specific
<a class="link" href="insert.html" title="15.2.7 INSERT Statement">
<code class="literal">
INSERT
</code>
</a>
,
<a class="link" href="update.html" title="15.2.17 UPDATE Statement">
<code class="literal">
UPDATE
</code>
</a>
, or
<a class="link" href="delete.html" title="15.2.2 DELETE Statement">
<code class="literal">
DELETE
</code>
</a>
statement lower
priority, use the
<code class="literal">
LOW_PRIORITY
</code>
attribute.
</p>
</li>
<li class="listitem">
<p>
To give a specific
<a class="link" href="select.html" title="15.2.13 SELECT Statement">
<code class="literal">
SELECT
</code>
</a>
statement higher priority, use the
<code class="literal">
HIGH_PRIORITY
</code>
attribute. See
<a class="xref" href="select.html" title="15.2.13 SELECT Statement">
Section 15.2.13, “SELECT Statement”
</a>
.
</p>
</li>
<li class="listitem">
<p>
Start
<a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
<span class="command">
<strong>
mysqld
</strong>
</span>
</a>
with a low value for the
<a class="link" href="server-system-variables.html#sysvar_max_write_lock_count">
<code class="literal">
max_write_lock_count
</code>
</a>
system variable to force MySQL to temporarily elevate the
priority of all
<a class="link" href="select.html" title="15.2.13 SELECT Statement">
<code class="literal">
SELECT
</code>
</a>
statements that are waiting for a table after a specific
number of write locks to the table occur (for example, for
insert operations). This permits read locks after a
certain number of write locks.
</p>
</li>
<li class="listitem">
<p>
If you have problems with mixed
<a class="link" href="select.html" title="15.2.13 SELECT Statement">
<code class="literal">
SELECT
</code>
</a>
and
<a class="link" href="delete.html" title="15.2.2 DELETE Statement">
<code class="literal">
DELETE
</code>
</a>
statements, the
<code class="literal">
LIMIT
</code>
option to
<a class="link" href="delete.html" title="15.2.2 DELETE Statement">
<code class="literal">
DELETE
</code>
</a>
may help. See
<a class="xref" href="delete.html" title="15.2.2 DELETE Statement">
Section 15.2.2, “DELETE Statement”
</a>
.
</p>
</li>
<li class="listitem">
<p>
Using
<code class="literal">
SQL_BUFFER_RESULT
</code>
with
<a class="link" href="select.html" title="15.2.13 SELECT Statement">
<code class="literal">
SELECT
</code>
</a>
statements can help
to make the duration of table locks shorter. See
<a class="xref" href="select.html" title="15.2.13 SELECT Statement">
Section 15.2.13, “SELECT Statement”
</a>
.
</p>
</li>
<li class="listitem">
<p>
Splitting table contents into separate tables may help, by
allowing queries to run against columns in one table,
while updates are confined to columns in a different
table.
</p>
</li>
<li class="listitem">
<p>
You could change the locking code in
<code class="filename">
mysys/thr_lock.c
</code>
to use a single
queue. In this case, write locks and read locks would have
the same priority, which might help some applications.
</p>
</li>
</ul>
</div>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/keyring-functions-plugin-specific.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="keyring-functions-plugin-specific">
</a>
8.4.4.13 Plugin-Specific Keyring Key-Management Functions
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045239439232">
</a>
<p>
For each keyring plugin-specific function, this section
describes its purpose, calling sequence, and return value. For
information about general-purpose keyring functions, see
<a class="xref" href="keyring-functions-general-purpose.html" title="8.4.4.12 General-Purpose Keyring Key-Management Functions">
Section 8.4.4.12, “General-Purpose Keyring Key-Management Functions”
</a>
.
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<a name="function_keyring-aws-rotate-cmk">
</a>
<a class="link" href="keyring-functions-plugin-specific.html#function_keyring-aws-rotate-cmk">
<code class="literal">
keyring_aws_rotate_cmk()
</code>
</a>
</p>
<a class="indexterm" name="idm46045239433872">
</a>
<a class="indexterm" name="idm46045239432768">
</a>
<p>
Associated keyring plugin:
<code class="literal">
keyring_aws
</code>
</p>
<p>
<a class="link" href="keyring-functions-plugin-specific.html#function_keyring-aws-rotate-cmk">
<code class="literal">
keyring_aws_rotate_cmk()
</code>
</a>
rotates the AWS KMS key. Rotation changes only the key that
AWS KMS uses for subsequent data key-encryption operations.
AWS KMS maintains previous CMK versions, so keys generated
using previous CMKs remain decryptable after rotation.
</p>
<p>
Rotation changes the CMK value used inside AWS KMS but does
not change the ID used to refer to it, so there is no need
to change the
<a class="link" href="keyring-system-variables.html#sysvar_keyring_aws_cmk_id">
<code class="literal">
keyring_aws_cmk_id
</code>
</a>
system
variable after calling
<a class="link" href="keyring-functions-plugin-specific.html#function_keyring-aws-rotate-cmk">
<code class="literal">
keyring_aws_rotate_cmk()
</code>
</a>
.
</p>
<p>
This function requires the
<a class="link" href="privileges-provided.html#priv_super">
<code class="literal">
SUPER
</code>
</a>
privilege.
</p>
<p>
Arguments:
</p>
<p>
None.
</p>
<p>
Return value:
</p>
<p>
Returns 1 for success, or
<code class="literal">
NULL
</code>
and an
error for failure.
</p>
</li>
<li class="listitem">
<p>
<a name="function_keyring-aws-rotate-keys">
</a>
<a class="link" href="keyring-functions-plugin-specific.html#function_keyring-aws-rotate-keys">
<code class="literal">
keyring_aws_rotate_keys()
</code>
</a>
</p>
<a class="indexterm" name="idm46045239418400">
</a>
<a class="indexterm" name="idm46045239417296">
</a>
<p>
Associated keyring plugin:
<code class="literal">
keyring_aws
</code>
</p>
<p>
<a class="link" href="keyring-functions-plugin-specific.html#function_keyring-aws-rotate-keys">
<code class="literal">
keyring_aws_rotate_keys()
</code>
</a>
rotates keys stored in the
<code class="literal">
keyring_aws
</code>
storage file named by the
<a class="link" href="keyring-system-variables.html#sysvar_keyring_aws_data_file">
<code class="literal">
keyring_aws_data_file
</code>
</a>
system variable. Rotation sends each key stored in the file
to AWS KMS for re-encryption using the value of the
<a class="link" href="keyring-system-variables.html#sysvar_keyring_aws_cmk_id">
<code class="literal">
keyring_aws_cmk_id
</code>
</a>
system
variable as the CMK value, and stores the new encrypted keys
in the file.
</p>
<p>
<a class="link" href="keyring-functions-plugin-specific.html#function_keyring-aws-rotate-keys">
<code class="literal">
keyring_aws_rotate_keys()
</code>
</a>
is
useful for key re-encryption under these circumstances:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
After rotating the CMK; that is, after invoking the
<a class="link" href="keyring-functions-plugin-specific.html#function_keyring-aws-rotate-cmk">
<code class="literal">
keyring_aws_rotate_cmk()
</code>
</a>
function.
</p>
</li>
<li class="listitem">
<p>
After changing the
<a class="link" href="keyring-system-variables.html#sysvar_keyring_aws_cmk_id">
<code class="literal">
keyring_aws_cmk_id
</code>
</a>
system variable to a different key value.
</p>
</li>
</ul>
</div>
<p>
This function requires the
<a class="link" href="privileges-provided.html#priv_super">
<code class="literal">
SUPER
</code>
</a>
privilege.
</p>
<p>
Arguments:
</p>
<p>
None.
</p>
<p>
Return value:
</p>
<p>
Returns 1 for success, or
<code class="literal">
NULL
</code>
and an
error for failure.
</p>
</li>
<li class="listitem">
<p>
<a name="function_keyring-hashicorp-update-config">
</a>
<a class="link" href="keyring-functions-plugin-specific.html#function_keyring-hashicorp-update-config">
<code class="literal">
keyring_hashicorp_update_config()
</code>
</a>
</p>
<a class="indexterm" name="idm46045239396240">
</a>
<a class="indexterm" name="idm46045239395120">
</a>
<p>
Associated keyring plugin:
<code class="literal">
keyring_hashicorp
</code>
</p>
<p>
When invoked, the
<a class="link" href="keyring-functions-plugin-specific.html#function_keyring-hashicorp-update-config">
<code class="literal">
keyring_hashicorp_update_config()
</code>
</a>
function causes
<code class="literal">
keyring_hashicorp
</code>
to
perform a runtime reconfiguration, as described in
<a class="xref" href="keyring-hashicorp-plugin.html#keyring-hashicorp-plugin-configuration" title="keyring_hashicorp Configuration">
keyring_hashicorp Configuration
</a>
.
</p>
<p>
This function requires the
<a class="link" href="privileges-provided.html#priv_system-variables-admin">
<code class="literal">
SYSTEM_VARIABLES_ADMIN
</code>
</a>
privilege because it modifies global system variables.
</p>
<p>
Arguments:
</p>
<p>
None.
</p>
<p>
Return value:
</p>
<p>
Returns the string
<code class="literal">
'Configuration update was
successful.'
</code>
for success, or
<code class="literal">
'Configuration update failed.'
</code>
for
failure.
</p>
</li>
</ul>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/administrative-connection-interface.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="administrative-connection-interface">
</a>
7.1.12.2 Administrative Connection Management
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045260945632">
</a>
<p>
As mentioned in
<a class="xref" href="connection-interfaces.html#connection-interfaces-volume-management" title="Connection Volume Management">
Connection Volume Management
</a>
, to
allow for the need to perform administrative operations even
when
<a class="link" href="server-system-variables.html#sysvar_max_connections">
<code class="literal">
max_connections
</code>
</a>
connections are already established on the interfaces used for
ordinary connections, the MySQL server permits a single
administrative connection to users who have the
<a class="link" href="privileges-provided.html#priv_connection-admin">
<code class="literal">
CONNECTION_ADMIN
</code>
</a>
privilege (or
the deprecated
<a class="link" href="privileges-provided.html#priv_super">
<code class="literal">
SUPER
</code>
</a>
privilege).
</p>
<p>
The server also permits dedicating a TCP/IP port for
administrative connections, as described in the following
sections.
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<a class="xref" href="administrative-connection-interface.html#administrative-interface-characteristics" title="Administrative Interface Characteristics">
Administrative Interface Characteristics
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="administrative-connection-interface.html#administrative-interface-encrypted-connections" title="Administrative Interface Support for Encrypted Connections">
Administrative Interface Support for Encrypted Connections
</a>
</p>
</li>
</ul>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h5 class="title">
<a name="administrative-interface-characteristics">
</a>
Administrative Interface Characteristics
</h5>
</div>
</div>
</div>
<p>
The administrative connection interface has these
characteristics:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
The server enables the interface only if the
<a class="link" href="server-system-variables.html#sysvar_admin_address">
<code class="literal">
admin_address
</code>
</a>
system
variable is set at startup to indicate the IP address for
it. If
<a class="link" href="server-system-variables.html#sysvar_admin_address">
<code class="literal">
admin_address
</code>
</a>
is
not set, the server maintains no administrative interface.
</p>
</li>
<li class="listitem">
<p>
The
<a class="link" href="server-system-variables.html#sysvar_admin_port">
<code class="literal">
admin_port
</code>
</a>
system
variable specifies the interface TCP/IP port number
(default 33062).
</p>
</li>
<li class="listitem">
<p>
There is no limit on the number of administrative
connections, but connections are permitted only for users
who have the
<a class="link" href="privileges-provided.html#priv_service-connection-admin">
<code class="literal">
SERVICE_CONNECTION_ADMIN
</code>
</a>
privilege.
</p>
</li>
<li class="listitem">
<p>
The
<a class="link" href="server-system-variables.html#sysvar_create_admin_listener_thread">
<code class="literal">
create_admin_listener_thread
</code>
</a>
system variable enables DBAs to choose at startup whether
the administrative interface has its own separate thread.
The default is
<code class="literal">
OFF
</code>
; that is, the
manager thread for ordinary connections on the main
interface also handles connections for the administrative
interface.
</p>
</li>
</ul>
</div>
<p>
These lines in the server
<code class="filename">
my.cnf
</code>
file
enable the administrative interface on the loopback interface
and configure it to use port number 33064 (that is, a port
different from the default):
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-ini"><div class="docs-select-all right" id="sa77990822"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-ini"><span class="token selector">[mysqld]</span>
<span class="token constant">admin_address</span><span class="token attr-value"><span class="token punctuation">=</span>127.0.0.1</span>
<span class="token constant">admin_port</span><span class="token attr-value"><span class="token punctuation">=</span>33064</span></code></pre>
</div>
<p>
MySQL client programs connect to either the main or
administrative interface by specifying appropriate connection
parameters. If the server running on the local host is using
the default TCP/IP port numbers of 3306 and 33062 for the main
and administrative interfaces, these commands connect to those
interfaces:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-terminal"><div class="docs-select-all right" id="sa35705331"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-terminal">mysql <span class="token constant">--protocol</span><span class="token attr-value"><span class="token punctuation">=</span>TCP</span> <span class="token constant">--port</span><span class="token attr-value"><span class="token punctuation">=</span>3306</span>
mysql <span class="token constant">--protocol</span><span class="token attr-value"><span class="token punctuation">=</span>TCP</span> <span class="token constant">--port</span><span class="token attr-value"><span class="token punctuation">=</span>33062</span></code></pre>
</div>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h5 class="title">
<a name="administrative-interface-encrypted-connections">
</a>
Administrative Interface Support for Encrypted Connections
</h5>
</div>
</div>
</div>
<p>
The administrative interface has its own configuration
parameters for encrypted connections. These correspond to the
main interface parameters but enable independent configuration
of encrypted connections for the administrative interface:
</p>
<p>
The
<code class="literal">
admin_tls_
<em class="replaceable">
<code>
xxx
</code>
</em>
</code>
and
<code class="literal">
admin_ssl_
<em class="replaceable">
<code>
xxx
</code>
</em>
</code>
system variables are like the
<code class="literal">
tls_
<em class="replaceable">
<code>
xxx
</code>
</em>
</code>
and
<code class="literal">
ssl_
<em class="replaceable">
<code>
xxx
</code>
</em>
</code>
system
variables, but they configure the TLS context for the
administrative interface rather than the main interface.
</p>
<p>
For general information about configuring
connection-encryption support, see
<a class="xref" href="using-encrypted-connections.html" title="8.3.1 Configuring MySQL to Use Encrypted Connections">
Section 8.3.1, “Configuring MySQL to Use Encrypted Connections”
</a>
, and
<a class="xref" href="encrypted-connection-protocols-ciphers.html" title="8.3.2 Encrypted Connection TLS Protocols and Ciphers">
Section 8.3.2, “Encrypted Connection TLS Protocols and Ciphers”
</a>
. That
discussion is written for the main connection interface, but
the parameter names are similar for the administrative
connection interface. Use that discussion together with the
following remarks, which provide information specific to the
administrative interface.
</p>
<p>
TLS configuration for the administrative interface follows
these rules:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
The administrative interface supports encrypted
connections. For connections on the interface, the
applicable TLS context depends on whether any nondefault
administrative TLS parameter is configured:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
If all administrative TLS parameters have their
default values, the administrative interface uses the
same TLS context as the main interface.
</p>
</li>
<li class="listitem">
<p>
If any administrative TLS parameter has a nondefault
value, the administrative interface uses the TLS
context defined by its own parameters. (This is the
case if any
<code class="literal">
admin_tls_
<em class="replaceable">
<code>
xxx
</code>
</em>
</code>
or
<code class="literal">
admin_ssl_
<em class="replaceable">
<code>
xxx
</code>
</em>
</code>
system variable is set to a value different from its
default.) If a valid TLS context cannot be created
from those parameters, the administrative interface
falls back to the main interface TLS context.
</p>
</li>
</ul>
</div>
</li>
<li class="listitem">
<p>
It is possible to disable encrypted connections to the
administrative interface by setting the
<a class="link" href="server-system-variables.html#sysvar_admin_tls_version">
<code class="literal">
admin_tls_version
</code>
</a>
system
variable to the empty value to indicate that no TLS
versions are supported. For example, these lines in the
server
<code class="filename">
my.cnf
</code>
file disable encrypted
connections on the administrative interface:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-ini"><div class="docs-select-all right" id="sa92069572"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-ini"><span class="token selector">[mysqld]</span>
<span class="token constant">admin_tls_version</span><span class="token attr-value"><span class="token punctuation">=</span>''</span></code></pre>
</div>
</li>
</ul>
</div>
<p>
Examples:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
This configuration in the server
<code class="filename">
my.cnf
</code>
file enables the
administrative interface, but does not set any of the TLS
parameters specific to that interface:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-ini"><div class="docs-select-all right" id="sa75092941"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-ini"><span class="token selector">[mysqld]</span>
<span class="token constant">admin_address</span><span class="token attr-value"><span class="token punctuation">=</span>127.0.0.1</span></code></pre>
</div>
<p>
As a result, the administrative interface supports
encrypted connections (because encryption is supported by
default when the administrative interface is enabled), and
uses the main interface TLS context. When clients connect
to the administrative interface, they should use the same
certificate and key files as for ordinary connections on
the main interface. For example (enter the command on a
single line):
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-terminal"><div class="docs-select-all right" id="sa49422114"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-terminal">mysql <span class="token constant">--protocol</span><span class="token attr-value"><span class="token punctuation">=</span>TCP</span> <span class="token constant">--port</span><span class="token attr-value"><span class="token punctuation">=</span>33062</span>
<span class="token constant">--ssl-ca</span><span class="token attr-value"><span class="token punctuation">=</span>ca.pem</span>
<span class="token constant">--ssl-cert</span><span class="token attr-value"><span class="token punctuation">=</span>client-cert.pem</span>
<span class="token constant">--ssl-key</span><span class="token attr-value"><span class="token punctuation">=</span>client-key.pem</span></code></pre>
</div>
</li>
<li class="listitem">
<p>
This server configuration enables the administrative
interface and sets the TLS certificate and key file
parameters specific to that interface:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-ini"><div class="docs-select-all right" id="sa97781042"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-ini"><span class="token selector">[mysqld]</span>
<span class="token constant">admin_address</span><span class="token attr-value"><span class="token punctuation">=</span>127.0.0.1</span>
<span class="token constant">admin_ssl_ca</span><span class="token attr-value"><span class="token punctuation">=</span>admin-ca.pem</span>
<span class="token constant">admin_ssl_cert</span><span class="token attr-value"><span class="token punctuation">=</span>admin-server-cert.pem</span>
<span class="token constant">admin_ssl_key</span><span class="token attr-value"><span class="token punctuation">=</span>admin-server-key.pem</span></code></pre>
</div>
<p>
As a result, the administrative interface supports
encrypted connections using its own TLS context. When
clients connect to the administrative interface, they
should use certificate and key files specific to that
interface. For example (enter the command on a single
line):
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-terminal"><div class="docs-select-all right" id="sa72258547"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-terminal">mysql <span class="token constant">--protocol</span><span class="token attr-value"><span class="token punctuation">=</span>TCP</span> <span class="token constant">--port</span><span class="token attr-value"><span class="token punctuation">=</span>33062</span>
<span class="token constant">--ssl-ca</span><span class="token attr-value"><span class="token punctuation">=</span>admin-ca.pem</span>
<span class="token constant">--ssl-cert</span><span class="token attr-value"><span class="token punctuation">=</span>admin-client-cert.pem</span>
<span class="token constant">--ssl-key</span><span class="token attr-value"><span class="token punctuation">=</span>admin-client-key.pem</span></code></pre>
</div>
</li>
</ul>
</div>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/group-by-optimization.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="group-by-optimization">
</a>
10.2.1.17 GROUP BY Optimization
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045228793344">
</a>
<a class="indexterm" name="idm46045228792272">
</a>
<p>
The most general way to satisfy a
<code class="literal">
GROUP BY
</code>
clause is to scan the whole table and create a new temporary
table where all rows from each group are consecutive, and then
use this temporary table to discover groups and apply
aggregate functions (if any). In some cases, MySQL is able to
do much better than that and avoid creation of temporary
tables by using index access.
</p>
<p>
The most important preconditions for using indexes for
<code class="literal">
GROUP BY
</code>
are that all
<code class="literal">
GROUP
BY
</code>
columns reference attributes from the same index,
and that the index stores its keys in order (as is true, for
example, for a
<code class="literal">
BTREE
</code>
index, but not for a
<code class="literal">
HASH
</code>
index). Whether use of temporary
tables can be replaced by index access also depends on which
parts of an index are used in a query, the conditions
specified for these parts, and the selected aggregate
functions.
</p>
<p>
There are two ways to execute a
<code class="literal">
GROUP BY
</code>
query through index access, as detailed in the following
sections. The first method applies the grouping operation
together with all range predicates (if any). The second method
first performs a range scan, and then groups the resulting
tuples.
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<a class="xref" href="group-by-optimization.html#loose-index-scan" title="Loose Index Scan">
Loose Index Scan
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="group-by-optimization.html#tight-index-scan" title="Tight Index Scan">
Tight Index Scan
</a>
</p>
</li>
</ul>
</div>
<p>
Loose Index Scan can also be used in the absence of
<code class="literal">
GROUP BY
</code>
under some conditions. See
<a class="xref" href="range-optimization.html#range-access-skip-scan" title="Skip Scan Range Access Method">
Skip Scan Range Access Method
</a>
.
</p>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h5 class="title">
<a name="loose-index-scan">
</a>
Loose Index Scan
</h5>
</div>
</div>
</div>
<a class="indexterm" name="idm46045228778704">
</a>
<p>
The most efficient way to process
<code class="literal">
GROUP
BY
</code>
is when an index is used to directly retrieve
the grouping columns. With this access method, MySQL uses
the property of some index types that the keys are ordered
(for example,
<code class="literal">
BTREE
</code>
). This property
enables use of lookup groups in an index without having to
consider all keys in the index that satisfy all
<code class="literal">
WHERE
</code>
conditions. This access method
considers only a fraction of the keys in an index, so it is
called a
<span class="firstterm">
Loose Index
Scan
</span>
. When there is no
<code class="literal">
WHERE
</code>
clause, a Loose Index Scan reads as many keys as the number
of groups, which may be a much smaller number than that of
all keys. If the
<code class="literal">
WHERE
</code>
clause contains
range predicates (see the discussion of the
<a class="link" href="explain-output.html#jointype_range">
<code class="literal">
range
</code>
</a>
join type in
<a class="xref" href="using-explain.html" title="10.8.1 Optimizing Queries with EXPLAIN">
Section 10.8.1, “Optimizing Queries with EXPLAIN”
</a>
), a Loose Index Scan looks
up the first key of each group that satisfies the range
conditions, and again reads the smallest possible number of
keys. This is possible under the following conditions:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
The query is over a single table.
</p>
</li>
<li class="listitem">
<p>
The
<code class="literal">
GROUP BY
</code>
names only columns that
form a leftmost prefix of the index and no other
columns. (If, instead of
<code class="literal">
GROUP BY
</code>
,
the query has a
<code class="literal">
DISTINCT
</code>
clause, all
distinct attributes refer to columns that form a
leftmost prefix of the index.) For example, if a table
<code class="literal">
t1
</code>
has an index on
<code class="literal">
(c1,c2,c3)
</code>
, Loose Index Scan is
applicable if the query has
<code class="literal">
GROUP BY c1,
c2
</code>
. It is not applicable if the query has
<code class="literal">
GROUP BY c2, c3
</code>
(the columns are not
a leftmost prefix) or
<code class="literal">
GROUP BY c1, c2,
c4
</code>
(
<code class="literal">
c4
</code>
is not in the
index).
</p>
</li>
<li class="listitem">
<p>
The only aggregate functions used in the select list (if
any) are
<a class="link" href="aggregate-functions.html#function_min">
<code class="literal">
MIN()
</code>
</a>
and
<a class="link" href="aggregate-functions.html#function_max">
<code class="literal">
MAX()
</code>
</a>
, and all of them
refer to the same column. The column must be in the
index and must immediately follow the columns in the
<code class="literal">
GROUP BY
</code>
.
</p>
</li>
<li class="listitem">
<p>
Any other parts of the index than those from the
<code class="literal">
GROUP BY
</code>
referenced in the query must
be constants (that is, they must be referenced in
equalities with constants), except for the argument of
<a class="link" href="aggregate-functions.html#function_min">
<code class="literal">
MIN()
</code>
</a>
or
<a class="link" href="aggregate-functions.html#function_max">
<code class="literal">
MAX()
</code>
</a>
functions.
</p>
</li>
<li class="listitem">
<p>
For columns in the index, full column values must be
indexed, not just a prefix. For example, with
<code class="literal">
c1 VARCHAR(20), INDEX (c1(10))
</code>
, the
index uses only a prefix of
<code class="literal">
c1
</code>
values
and cannot be used for Loose Index Scan.
</p>
</li>
</ul>
</div>
<p>
If Loose Index Scan is applicable to a query, the
<a class="link" href="explain.html" title="15.8.2 EXPLAIN Statement">
<code class="literal">
EXPLAIN
</code>
</a>
output shows
<code class="literal">
Using index for group-by
</code>
in the
<code class="literal">
Extra
</code>
column.
</p>
<p>
Assume that there is an index
<code class="literal">
idx(c1,c2,c3)
</code>
on table
<code class="literal">
t1(c1,c2,c3,c4)
</code>
. The Loose Index Scan
access method can be used for the following queries:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa78568829"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SELECT</span> c1<span class="token punctuation">,</span> c2 <span class="token keyword">FROM</span> t1 <span class="token keyword">GROUP</span> <span class="token keyword">BY</span> c1<span class="token punctuation">,</span> c2<span class="token punctuation">;</span>
<span class="token keyword">SELECT</span> <span class="token keyword">DISTINCT</span> c1<span class="token punctuation">,</span> c2 <span class="token keyword">FROM</span> t1<span class="token punctuation">;</span>
<span class="token keyword">SELECT</span> c1<span class="token punctuation">,</span> <span class="token function">MIN</span><span class="token punctuation">(</span>c2<span class="token punctuation">)</span> <span class="token keyword">FROM</span> t1 <span class="token keyword">GROUP</span> <span class="token keyword">BY</span> c1<span class="token punctuation">;</span>
<span class="token keyword">SELECT</span> c1<span class="token punctuation">,</span> c2 <span class="token keyword">FROM</span> t1 <span class="token keyword">WHERE</span> c1 <span class="token operator"><</span> <em class="replaceable">const</em> <span class="token keyword">GROUP</span> <span class="token keyword">BY</span> c1<span class="token punctuation">,</span> c2<span class="token punctuation">;</span>
<span class="token keyword">SELECT</span> <span class="token function">MAX</span><span class="token punctuation">(</span>c3<span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token function">MIN</span><span class="token punctuation">(</span>c3<span class="token punctuation">)</span><span class="token punctuation">,</span> c1<span class="token punctuation">,</span> c2 <span class="token keyword">FROM</span> t1 <span class="token keyword">WHERE</span> c2 <span class="token operator">></span> <em class="replaceable">const</em> <span class="token keyword">GROUP</span> <span class="token keyword">BY</span> c1<span class="token punctuation">,</span> c2<span class="token punctuation">;</span>
<span class="token keyword">SELECT</span> c2 <span class="token keyword">FROM</span> t1 <span class="token keyword">WHERE</span> c1 <span class="token operator"><</span> <em class="replaceable">const</em> <span class="token keyword">GROUP</span> <span class="token keyword">BY</span> c1<span class="token punctuation">,</span> c2<span class="token punctuation">;</span>
<span class="token keyword">SELECT</span> c1<span class="token punctuation">,</span> c2 <span class="token keyword">FROM</span> t1 <span class="token keyword">WHERE</span> c3 <span class="token operator">=</span> <em class="replaceable">const</em> <span class="token keyword">GROUP</span> <span class="token keyword">BY</span> c1<span class="token punctuation">,</span> c2<span class="token punctuation">;</span></code></pre>
</div>
<p>
The following queries cannot be executed with this quick
select method, for the reasons given:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
There are aggregate functions other than
<a class="link" href="aggregate-functions.html#function_min">
<code class="literal">
MIN()
</code>
</a>
or
<a class="link" href="aggregate-functions.html#function_max">
<code class="literal">
MAX()
</code>
</a>
:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa55249554"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SELECT</span> c1<span class="token punctuation">,</span> <span class="token function">SUM</span><span class="token punctuation">(</span>c2<span class="token punctuation">)</span> <span class="token keyword">FROM</span> t1 <span class="token keyword">GROUP</span> <span class="token keyword">BY</span> c1<span class="token punctuation">;</span></code></pre>
</div>
</li>
<li class="listitem">
<p>
The columns in the
<code class="literal">
GROUP BY
</code>
clause do
not form a leftmost prefix of the index:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa97897324"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SELECT</span> c1<span class="token punctuation">,</span> c2 <span class="token keyword">FROM</span> t1 <span class="token keyword">GROUP</span> <span class="token keyword">BY</span> c2<span class="token punctuation">,</span> c3<span class="token punctuation">;</span></code></pre>
</div>
</li>
<li class="listitem">
<p>
The query refers to a part of a key that comes after the
<code class="literal">
GROUP BY
</code>
part, and for which there is
no equality with a constant:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa38330306"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SELECT</span> c1<span class="token punctuation">,</span> c3 <span class="token keyword">FROM</span> t1 <span class="token keyword">GROUP</span> <span class="token keyword">BY</span> c1<span class="token punctuation">,</span> c2<span class="token punctuation">;</span></code></pre>
</div>
<p>
Were the query to include
<code class="literal">
WHERE c3 =
<em class="replaceable">
<code>
const
</code>
</em>
</code>
, Loose Index
Scan could be used.
</p>
</li>
</ul>
</div>
<p>
The Loose Index Scan access method can be applied to other
forms of aggregate function references in the select list,
in addition to the
<a class="link" href="aggregate-functions.html#function_min">
<code class="literal">
MIN()
</code>
</a>
and
<a class="link" href="aggregate-functions.html#function_max">
<code class="literal">
MAX()
</code>
</a>
references already
supported:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<a class="link" href="aggregate-functions.html#function_avg">
<code class="literal">
AVG(DISTINCT)
</code>
</a>
,
<a class="link" href="aggregate-functions.html#function_sum">
<code class="literal">
SUM(DISTINCT)
</code>
</a>
, and
<a class="link" href="aggregate-functions.html#function_count">
<code class="literal">
COUNT(DISTINCT)
</code>
</a>
are
supported.
<a class="link" href="aggregate-functions.html#function_avg">
<code class="literal">
AVG(DISTINCT)
</code>
</a>
and
<a class="link" href="aggregate-functions.html#function_sum">
<code class="literal">
SUM(DISTINCT)
</code>
</a>
take a
single argument.
<a class="link" href="aggregate-functions.html#function_count">
<code class="literal">
COUNT(DISTINCT)
</code>
</a>
can have
more than one column argument.
</p>
</li>
<li class="listitem">
<p>
There must be no
<code class="literal">
GROUP BY
</code>
or
<code class="literal">
DISTINCT
</code>
clause in the query.
</p>
</li>
<li class="listitem">
<p>
The Loose Index Scan limitations described previously
still apply.
</p>
</li>
</ul>
</div>
<p>
Assume that there is an index
<code class="literal">
idx(c1,c2,c3)
</code>
on table
<code class="literal">
t1(c1,c2,c3,c4)
</code>
. The Loose Index Scan
access method can be used for the following queries:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa51629962"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SELECT</span> <span class="token function">COUNT</span><span class="token punctuation">(</span><span class="token keyword">DISTINCT</span> c1<span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token function">SUM</span><span class="token punctuation">(</span><span class="token keyword">DISTINCT</span> c1<span class="token punctuation">)</span> <span class="token keyword">FROM</span> t1<span class="token punctuation">;</span>
<span class="token keyword">SELECT</span> <span class="token function">COUNT</span><span class="token punctuation">(</span><span class="token keyword">DISTINCT</span> c1<span class="token punctuation">,</span> c2<span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token function">COUNT</span><span class="token punctuation">(</span><span class="token keyword">DISTINCT</span> c2<span class="token punctuation">,</span> c1<span class="token punctuation">)</span> <span class="token keyword">FROM</span> t1<span class="token punctuation">;</span></code></pre>
</div>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h5 class="title">
<a name="tight-index-scan">
</a>
Tight Index Scan
</h5>
</div>
</div>
</div>
<p>
A Tight Index Scan may be either a full index scan or a
range index scan, depending on the query conditions.
</p>
<p>
When the conditions for a Loose Index Scan are not met, it
still may be possible to avoid creation of temporary tables
for
<code class="literal">
GROUP BY
</code>
queries. If there are range
conditions in the
<code class="literal">
WHERE
</code>
clause, this
method reads only the keys that satisfy these conditions.
Otherwise, it performs an index scan. Because this method
reads all keys in each range defined by the
<code class="literal">
WHERE
</code>
clause, or scans the whole index if
there are no range conditions, it is called a
<span class="firstterm">
Tight Index Scan
</span>
. With
a Tight Index Scan, the grouping operation is performed only
after all keys that satisfy the range conditions have been
found.
</p>
<p>
For this method to work, it is sufficient that there be a
constant equality condition for all columns in a query
referring to parts of the key coming before or in between
parts of the
<code class="literal">
GROUP BY
</code>
key. The constants
from the equality conditions fill in any
<span class="quote">
“
<span class="quote">
gaps
</span>
”
</span>
in the search keys so that it is possible to form complete
prefixes of the index. These index prefixes then can be used
for index lookups. If the
<code class="literal">
GROUP BY
</code>
result
requires sorting, and it is possible to form search keys
that are prefixes of the index, MySQL also avoids extra
sorting operations because searching with prefixes in an
ordered index already retrieves all the keys in order.
</p>
<p>
Assume that there is an index
<code class="literal">
idx(c1,c2,c3)
</code>
on table
<code class="literal">
t1(c1,c2,c3,c4)
</code>
. The following queries do
not work with the Loose Index Scan access method described
previously, but still work with the Tight Index Scan access
method.
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
There is a gap in the
<code class="literal">
GROUP BY
</code>
, but
it is covered by the condition
<code class="literal">
c2 =
'a'
</code>
:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa5784141"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SELECT</span> c1<span class="token punctuation">,</span> c2<span class="token punctuation">,</span> c3 <span class="token keyword">FROM</span> t1 <span class="token keyword">WHERE</span> c2 <span class="token operator">=</span> <span class="token string">'a'</span> <span class="token keyword">GROUP</span> <span class="token keyword">BY</span> c1<span class="token punctuation">,</span> c3<span class="token punctuation">;</span></code></pre>
</div>
</li>
<li class="listitem">
<p>
The
<code class="literal">
GROUP BY
</code>
does not begin with the
first part of the key, but there is a condition that
provides a constant for that part:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa44899380"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SELECT</span> c1<span class="token punctuation">,</span> c2<span class="token punctuation">,</span> c3 <span class="token keyword">FROM</span> t1 <span class="token keyword">WHERE</span> c1 <span class="token operator">=</span> <span class="token string">'a'</span> <span class="token keyword">GROUP</span> <span class="token keyword">BY</span> c2<span class="token punctuation">,</span> c3<span class="token punctuation">;</span></code></pre>
</div>
</li>
</ul>
</div>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/date-and-time-functions.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h2 class="title">
<a name="date-and-time-functions">
</a>
14.7 Date and Time Functions
</h2>
</div>
</div>
</div>
<a class="indexterm" name="idm46045205615744">
</a>
<a class="indexterm" name="idm46045205614672">
</a>
<p>
This section describes the functions that can be used to
manipulate temporal values. See
<a class="xref" href="date-and-time-types.html" title="13.2 Date and Time Data Types">
Section 13.2, “Date and Time Data Types”
</a>
, for a description of the
range of values each date and time type has and the valid formats
in which values may be specified.
</p>
<div class="table">
<a name="idm46045205611840">
</a>
<p class="title">
<b>
Table 14.11 Date and Time Functions
</b>
</p>
<div class="table-contents">
<table frame="box" rules="all" summary="A reference that lists date and time functions.">
<colgroup>
<col style="width: 28%"/>
<col style="width: 71%"/>
</colgroup>
<thead>
<tr>
<th>
Name
</th>
<th>
Description
</th>
</tr>
</thead>
<tbody>
<tr>
<td>
<a class="link" href="date-and-time-functions.html#function_adddate">
<code class="literal">
ADDDATE()
</code>
</a>
</td>
<td>
Add time values (intervals) to a date value
</td>
</tr>
<tr>
<td>
<a class="link" href="date-and-time-functions.html#function_addtime">
<code class="literal">
ADDTIME()
</code>
</a>
</td>
<td>
Add time
</td>
</tr>
<tr>
<td>
<a class="link" href="date-and-time-functions.html#function_convert-tz">
<code class="literal">
CONVERT_TZ()
</code>
</a>
</td>
<td>
Convert from one time zone to another
</td>
</tr>
<tr>
<td>
<a class="link" href="date-and-time-functions.html#function_curdate">
<code class="literal">
CURDATE()
</code>
</a>
</td>
<td>
Return the current date
</td>
</tr>
<tr>
<td>
<a class="link" href="date-and-time-functions.html#function_current-date">
<code class="literal">
CURRENT_DATE()
</code>
,
<code class="literal">
CURRENT_DATE
</code>
</a>
</td>
<td>
Synonyms for CURDATE()
</td>
</tr>
<tr>
<td>
<a class="link" href="date-and-time-functions.html#function_current-time">
<code class="literal">
CURRENT_TIME()
</code>
,
<code class="literal">
CURRENT_TIME
</code>
</a>
</td>
<td>
Synonyms for CURTIME()
</td>
</tr>
<tr>
<td>
<a class="link" href="date-and-time-functions.html#function_current-timestamp">
<code class="literal">
CURRENT_TIMESTAMP()
</code>
,
<code class="literal">
CURRENT_TIMESTAMP
</code>
</a>
</td>
<td>
Synonyms for NOW()
</td>
</tr>
<tr>
<td>
<a class="link" href="date-and-time-functions.html#function_curtime">
<code class="literal">
CURTIME()
</code>
</a>
</td>
<td>
Return the current time
</td>
</tr>
<tr>
<td>
<a class="link" href="date-and-time-functions.html#function_date">
<code class="literal">
DATE()
</code>
</a>
</td>
<td>
Extract the date part of a date or datetime expression
</td>
</tr>
<tr>
<td>
<a class="link" href="date-and-time-functions.html#function_date-add">
<code class="literal">
DATE_ADD()
</code>
</a>
</td>
<td>
Add time values (intervals) to a date value
</td>
</tr>
<tr>
<td>
<a class="link" href="date-and-time-functions.html#function_date-format">
<code class="literal">
DATE_FORMAT()
</code>
</a>
</td>
<td>
Format date as specified
</td>
</tr>
<tr>
<td>
<a class="link" href="date-and-time-functions.html#function_date-sub">
<code class="literal">
DATE_SUB()
</code>
</a>
</td>
<td>
Subtract a time value (interval) from a date
</td>
</tr>
<tr>
<td>
<a class="link" href="date-and-time-functions.html#function_datediff">
<code class="literal">
DATEDIFF()
</code>
</a>
</td>
<td>
Subtract two dates
</td>
</tr>
<tr>
<td>
<a class="link" href="date-and-time-functions.html#function_day">
<code class="literal">
DAY()
</code>
</a>
</td>
<td>
Synonym for DAYOFMONTH()
</td>
</tr>
<tr>
<td>
<a class="link" href="date-and-time-functions.html#function_dayname">
<code class="literal">
DAYNAME()
</code>
</a>
</td>
<td>
Return the name of the weekday
</td>
</tr>
<tr>
<td>
<a class="link" href="date-and-time-functions.html#function_dayofmonth">
<code class="literal">
DAYOFMONTH()
</code>
</a>
</td>
<td>
Return the day of the month (0-31)
</td>
</tr>
<tr>
<td>
<a class="link" href="date-and-time-functions.html#function_dayofweek">
<code class="literal">
DAYOFWEEK()
</code>
</a>
</td>
<td>
Return the weekday index of the argument
</td>
</tr>
<tr>
<td>
<a class="link" href="date-and-time-functions.html#function_dayofyear">
<code class="literal">
DAYOFYEAR()
</code>
</a>
</td>
<td>
Return the day of the year (1-366)
</td>
</tr>
<tr>
<td>
<a class="link" href="date-and-time-functions.html#function_extract">
<code class="literal">
EXTRACT()
</code>
</a>
</td>
<td>
Extract part of a date
</td>
</tr>
<tr>
<td>
<a class="link" href="date-and-time-functions.html#function_from-days">
<code class="literal">
FROM_DAYS()
</code>
</a>
</td>
<td>
Convert a day number to a date
</td>
</tr>
<tr>
<td>
<a class="link" href="date-and-time-functions.html#function_from-unixtime">
<code class="literal">
FROM_UNIXTIME()
</code>
</a>
</td>
<td>
Format Unix timestamp as a date
</td>
</tr>
<tr>
<td>
<a class="link" href="date-and-time-functions.html#function_get-format">
<code class="literal">
GET_FORMAT()
</code>
</a>
</td>
<td>
Return a date format string
</td>
</tr>
<tr>
<td>
<a class="link" href="date-and-time-functions.html#function_hour">
<code class="literal">
HOUR()
</code>
</a>
</td>
<td>
Extract the hour
</td>
</tr>
<tr>
<td>
<a class="link" href="date-and-time-functions.html#function_last-day">
<code class="literal">
LAST_DAY
</code>
</a>
</td>
<td>
Return the last day of the month for the argument
</td>
</tr>
<tr>
<td>
<a class="link" href="date-and-time-functions.html#function_localtime">
<code class="literal">
LOCALTIME()
</code>
,
<code class="literal">
LOCALTIME
</code>
</a>
</td>
<td>
Synonym for NOW()
</td>
</tr>
<tr>
<td>
<a class="link" href="date-and-time-functions.html#function_localtimestamp">
<code class="literal">
LOCALTIMESTAMP
</code>
,
<code class="literal">
LOCALTIMESTAMP()
</code>
</a>
</td>
<td>
Synonym for NOW()
</td>
</tr>
<tr>
<td>
<a class="link" href="date-and-time-functions.html#function_makedate">
<code class="literal">
MAKEDATE()
</code>
</a>
</td>
<td>
Create a date from the year and day of year
</td>
</tr>
<tr>
<td>
<a class="link" href="date-and-time-functions.html#function_maketime">
<code class="literal">
MAKETIME()
</code>
</a>
</td>
<td>
Create time from hour, minute, second
</td>
</tr>
<tr>
<td>
<a class="link" href="date-and-time-functions.html#function_microsecond">
<code class="literal">
MICROSECOND()
</code>
</a>
</td>
<td>
Return the microseconds from argument
</td>
</tr>
<tr>
<td>
<a class="link" href="date-and-time-functions.html#function_minute">
<code class="literal">
MINUTE()
</code>
</a>
</td>
<td>
Return the minute from the argument
</td>
</tr>
<tr>
<td>
<a class="link" href="date-and-time-functions.html#function_month">
<code class="literal">
MONTH()
</code>
</a>
</td>
<td>
Return the month from the date passed
</td>
</tr>
<tr>
<td>
<a class="link" href="date-and-time-functions.html#function_monthname">
<code class="literal">
MONTHNAME()
</code>
</a>
</td>
<td>
Return the name of the month
</td>
</tr>
<tr>
<td>
<a class="link" href="date-and-time-functions.html#function_now">
<code class="literal">
NOW()
</code>
</a>
</td>
<td>
Return the current date and time
</td>
</tr>
<tr>
<td>
<a class="link" href="date-and-time-functions.html#function_period-add">
<code class="literal">
PERIOD_ADD()
</code>
</a>
</td>
<td>
Add a period to a year-month
</td>
</tr>
<tr>
<td>
<a class="link" href="date-and-time-functions.html#function_period-diff">
<code class="literal">
PERIOD_DIFF()
</code>
</a>
</td>
<td>
Return the number of months between periods
</td>
</tr>
<tr>
<td>
<a class="link" href="date-and-time-functions.html#function_quarter">
<code class="literal">
QUARTER()
</code>
</a>
</td>
<td>
Return the quarter from a date argument
</td>
</tr>
<tr>
<td>
<a class="link" href="date-and-time-functions.html#function_sec-to-time">
<code class="literal">
SEC_TO_TIME()
</code>
</a>
</td>
<td>
Converts seconds to 'hh:mm:ss' format
</td>
</tr>
<tr>
<td>
<a class="link" href="date-and-time-functions.html#function_second">
<code class="literal">
SECOND()
</code>
</a>
</td>
<td>
Return the second (0-59)
</td>
</tr>
<tr>
<td>
<a class="link" href="date-and-time-functions.html#function_str-to-date">
<code class="literal">
STR_TO_DATE()
</code>
</a>
</td>
<td>
Convert a string to a date
</td>
</tr>
<tr>
<td>
<a class="link" href="date-and-time-functions.html#function_subdate">
<code class="literal">
SUBDATE()
</code>
</a>
</td>
<td>
Synonym for DATE_SUB() when invoked with three arguments
</td>
</tr>
<tr>
<td>
<a class="link" href="date-and-time-functions.html#function_subtime">
<code class="literal">
SUBTIME()
</code>
</a>
</td>
<td>
Subtract times
</td>
</tr>
<tr>
<td>
<a class="link" href="date-and-time-functions.html#function_sysdate">
<code class="literal">
SYSDATE()
</code>
</a>
</td>
<td>
Return the time at which the function executes
</td>
</tr>
<tr>
<td>
<a class="link" href="date-and-time-functions.html#function_time">
<code class="literal">
TIME()
</code>
</a>
</td>
<td>
Extract the time portion of the expression passed
</td>
</tr>
<tr>
<td>
<a class="link" href="date-and-time-functions.html#function_time-format">
<code class="literal">
TIME_FORMAT()
</code>
</a>
</td>
<td>
Format as time
</td>
</tr>
<tr>
<td>
<a class="link" href="date-and-time-functions.html#function_time-to-sec">
<code class="literal">
TIME_TO_SEC()
</code>
</a>
</td>
<td>
Return the argument converted to seconds
</td>
</tr>
<tr>
<td>
<a class="link" href="date-and-time-functions.html#function_timediff">
<code class="literal">
TIMEDIFF()
</code>
</a>
</td>
<td>
Subtract time
</td>
</tr>
<tr>
<td>
<a class="link" href="date-and-time-functions.html#function_timestamp">
<code class="literal">
TIMESTAMP()
</code>
</a>
</td>
<td>
With a single argument, this function returns the date or datetime
expression; with two arguments, the sum of the arguments
</td>
</tr>
<tr>
<td>
<a class="link" href="date-and-time-functions.html#function_timestampadd">
<code class="literal">
TIMESTAMPADD()
</code>
</a>
</td>
<td>
Add an interval to a datetime expression
</td>
</tr>
<tr>
<td>
<a class="link" href="date-and-time-functions.html#function_timestampdiff">
<code class="literal">
TIMESTAMPDIFF()
</code>
</a>
</td>
<td>
Return the difference of two datetime expressions, using the units
specified
</td>
</tr>
<tr>
<td>
<a class="link" href="date-and-time-functions.html#function_to-days">
<code class="literal">
TO_DAYS()
</code>
</a>
</td>
<td>
Return the date argument converted to days
</td>
</tr>
<tr>
<td>
<a class="link" href="date-and-time-functions.html#function_to-seconds">
<code class="literal">
TO_SECONDS()
</code>
</a>
</td>
<td>
Return the date or datetime argument converted to seconds since
Year 0
</td>
</tr>
<tr>
<td>
<a class="link" href="date-and-time-functions.html#function_unix-timestamp">
<code class="literal">
UNIX_TIMESTAMP()
</code>
</a>
</td>
<td>
Return a Unix timestamp
</td>
</tr>
<tr>
<td>
<a class="link" href="date-and-time-functions.html#function_utc-date">
<code class="literal">
UTC_DATE()
</code>
</a>
</td>
<td>
Return the current UTC date
</td>
</tr>
<tr>
<td>
<a class="link" href="date-and-time-functions.html#function_utc-time">
<code class="literal">
UTC_TIME()
</code>
</a>
</td>
<td>
Return the current UTC time
</td>
</tr>
<tr>
<td>
<a class="link" href="date-and-time-functions.html#function_utc-timestamp">
<code class="literal">
UTC_TIMESTAMP()
</code>
</a>
</td>
<td>
Return the current UTC date and time
</td>
</tr>
<tr>
<td>
<a class="link" href="date-and-time-functions.html#function_week">
<code class="literal">
WEEK()
</code>
</a>
</td>
<td>
Return the week number
</td>
</tr>
<tr>
<td>
<a class="link" href="date-and-time-functions.html#function_weekday">
<code class="literal">
WEEKDAY()
</code>
</a>
</td>
<td>
Return the weekday index
</td>
</tr>
<tr>
<td>
<a class="link" href="date-and-time-functions.html#function_weekofyear">
<code class="literal">
WEEKOFYEAR()
</code>
</a>
</td>
<td>
Return the calendar week of the date (1-53)
</td>
</tr>
<tr>
<td>
<a class="link" href="date-and-time-functions.html#function_year">
<code class="literal">
YEAR()
</code>
</a>
</td>
<td>
Return the year
</td>
</tr>
<tr>
<td>
<a class="link" href="date-and-time-functions.html#function_yearweek">
<code class="literal">
YEARWEEK()
</code>
</a>
</td>
<td>
Return the year and week
</td>
</tr>
</tbody>
</table>
</div>
<div class="table-contents">
<table cellpadding="0" cellspacing="0" style="position: fixed; top: 0px; display: none; left: 401px; width: 739px;">
<thead>
<tr>
<th style="width: 208.719px;">
Name
</th>
<th style="width: 529.281px;">
Description
</th>
</tr>
</thead>
</table>
</div>
</div>
<br class="table-break"/>
<p>
Here is an example that uses date functions. The following query
selects all rows with a
<em class="replaceable">
<code>
date_col
</code>
</em>
value
from within the last 30 days:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa63540858"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <em class="replaceable">something</em> <span class="token keyword">FROM</span> <em class="replaceable">tbl_name</em>
<span class="token prompt"> -></span> <span class="token keyword">WHERE</span> <span class="token function">DATE_SUB</span><span class="token punctuation">(</span><span class="token function">CURDATE</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">,</span><span class="token keyword">INTERVAL</span> <span class="token number">30</span> <span class="token keyword">DAY</span><span class="token punctuation">)</span> <span class="token operator"><=</span> <em class="replaceable">date_col</em><span class="token punctuation">;</span></code></pre>
</div>
<p>
The query also selects rows with dates that lie in the future.
</p>
<p>
Functions that expect date values usually accept datetime values
and ignore the time part. Functions that expect time values
usually accept datetime values and ignore the date part.
</p>
<p>
Functions that return the current date or time each are evaluated
only once per query at the start of query execution. This means
that multiple references to a function such as
<a class="link" href="date-and-time-functions.html#function_now">
<code class="literal">
NOW()
</code>
</a>
within a single query always
produce the same result. (For our purposes, a single query also
includes a call to a stored program (stored routine, trigger, or
event) and all subprograms called by that program.) This principle
also applies to
<a class="link" href="date-and-time-functions.html#function_curdate">
<code class="literal">
CURDATE()
</code>
</a>
,
<a class="link" href="date-and-time-functions.html#function_curtime">
<code class="literal">
CURTIME()
</code>
</a>
,
<a class="link" href="date-and-time-functions.html#function_utc-date">
<code class="literal">
UTC_DATE()
</code>
</a>
,
<a class="link" href="date-and-time-functions.html#function_utc-time">
<code class="literal">
UTC_TIME()
</code>
</a>
,
<a class="link" href="date-and-time-functions.html#function_utc-timestamp">
<code class="literal">
UTC_TIMESTAMP()
</code>
</a>
, and to any of
their synonyms.
</p>
<p>
The
<a class="link" href="date-and-time-functions.html#function_current-timestamp">
<code class="literal">
CURRENT_TIMESTAMP()
</code>
</a>
,
<a class="link" href="date-and-time-functions.html#function_current-time">
<code class="literal">
CURRENT_TIME()
</code>
</a>
,
<a class="link" href="date-and-time-functions.html#function_current-date">
<code class="literal">
CURRENT_DATE()
</code>
</a>
, and
<a class="link" href="date-and-time-functions.html#function_from-unixtime">
<code class="literal">
FROM_UNIXTIME()
</code>
</a>
functions return
values in the current session time zone, which is available as the
session value of the
<a class="link" href="server-system-variables.html#sysvar_time_zone">
<code class="literal">
time_zone
</code>
</a>
system variable. In addition,
<a class="link" href="date-and-time-functions.html#function_unix-timestamp">
<code class="literal">
UNIX_TIMESTAMP()
</code>
</a>
assumes that its
argument is a datetime value in the session time zone. See
<a class="xref" href="time-zone-support.html" title="7.1.15 MySQL Server Time Zone Support">
Section 7.1.15, “MySQL Server Time Zone Support”
</a>
.
</p>
<p>
Some date functions can be used with
<span class="quote">
“
<span class="quote">
zero
</span>
”
</span>
dates or
incomplete dates such as
<code class="literal">
'2001-11-00'
</code>
, whereas
others cannot. Functions that extract parts of dates typically
work with incomplete dates and thus can return 0 when you might
otherwise expect a nonzero value. For example:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa47097457"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">DAYOFMONTH</span><span class="token punctuation">(</span><span class="token string">'2001-11-00'</span><span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token function">MONTH</span><span class="token punctuation">(</span><span class="token string">'2005-00-00'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token number">0</span><span class="token punctuation">,</span> <span class="token number">0</span></code></pre>
</div>
<p>
Other functions expect complete dates and return
<code class="literal">
NULL
</code>
for incomplete dates. These include
functions that perform date arithmetic or that map parts of dates
to names. For example:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa54626338"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">DATE_ADD</span><span class="token punctuation">(</span><span class="token string">'2006-05-00'</span><span class="token punctuation">,</span><span class="token keyword">INTERVAL</span> <span class="token number">1</span> <span class="token keyword">DAY</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token boolean">NULL</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">DAYNAME</span><span class="token punctuation">(</span><span class="token string">'2006-05-00'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token boolean">NULL</span></code></pre>
</div>
<p>
Several functions are strict when passed a
<a class="link" href="date-and-time-functions.html#function_date">
<code class="literal">
DATE()
</code>
</a>
function value as their
argument and reject incomplete dates with a day part of zero:
<a class="link" href="date-and-time-functions.html#function_convert-tz">
<code class="literal">
CONVERT_TZ()
</code>
</a>
,
<a class="link" href="date-and-time-functions.html#function_date-add">
<code class="literal">
DATE_ADD()
</code>
</a>
,
<a class="link" href="date-and-time-functions.html#function_date-sub">
<code class="literal">
DATE_SUB()
</code>
</a>
,
<a class="link" href="date-and-time-functions.html#function_dayofyear">
<code class="literal">
DAYOFYEAR()
</code>
</a>
,
<a class="link" href="date-and-time-functions.html#function_timestampdiff">
<code class="literal">
TIMESTAMPDIFF()
</code>
</a>
,
<a class="link" href="date-and-time-functions.html#function_to-days">
<code class="literal">
TO_DAYS()
</code>
</a>
,
<a class="link" href="date-and-time-functions.html#function_to-seconds">
<code class="literal">
TO_SECONDS()
</code>
</a>
,
<a class="link" href="date-and-time-functions.html#function_week">
<code class="literal">
WEEK()
</code>
</a>
,
<a class="link" href="date-and-time-functions.html#function_weekday">
<code class="literal">
WEEKDAY()
</code>
</a>
,
<a class="link" href="date-and-time-functions.html#function_weekofyear">
<code class="literal">
WEEKOFYEAR()
</code>
</a>
,
<a class="link" href="date-and-time-functions.html#function_yearweek">
<code class="literal">
YEARWEEK()
</code>
</a>
.
</p>
<p>
Fractional seconds for
<code class="literal">
TIME
</code>
,
<code class="literal">
DATETIME
</code>
, and
<code class="literal">
TIMESTAMP
</code>
values are supported, with up to microsecond precision. Functions
that take temporal arguments accept values with fractional
seconds. Return values from temporal functions include fractional
seconds as appropriate.
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<a name="function_adddate">
</a>
<p>
<a class="link" href="date-and-time-functions.html#function_adddate">
<code class="literal">
ADDDATE(
<em class="replaceable">
<code>
date
</code>
</em>
,INTERVAL
<em class="replaceable">
<code>
expr
</code>
</em>
<em class="replaceable">
<code>
unit
</code>
</em>
)
</code>
</a>
,
<a class="link" href="date-and-time-functions.html#function_adddate">
<code class="literal">
ADDDATE(
<em class="replaceable">
<code>
date
</code>
</em>
,
<em class="replaceable">
<code>
days
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045205367136">
</a>
<p>
When invoked with the
<code class="literal">
INTERVAL
</code>
form of the
second argument,
<a class="link" href="date-and-time-functions.html#function_adddate">
<code class="literal">
ADDDATE()
</code>
</a>
is a
synonym for
<a class="link" href="date-and-time-functions.html#function_date-add">
<code class="literal">
DATE_ADD()
</code>
</a>
. The
related function
<a class="link" href="date-and-time-functions.html#function_subdate">
<code class="literal">
SUBDATE()
</code>
</a>
is a
synonym for
<a class="link" href="date-and-time-functions.html#function_date-sub">
<code class="literal">
DATE_SUB()
</code>
</a>
. For
information on the
<code class="literal">
INTERVAL
</code>
<em class="replaceable">
<code>
unit
</code>
</em>
argument, see
<a class="xref" href="expressions.html#temporal-intervals" title="Temporal Intervals">
Temporal Intervals
</a>
.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa16233991"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">DATE_ADD</span><span class="token punctuation">(</span><span class="token string">'2008-01-02'</span><span class="token punctuation">,</span> <span class="token keyword">INTERVAL</span> <span class="token number">31</span> <span class="token keyword">DAY</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token string">'2008-02-02'</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">ADDDATE</span><span class="token punctuation">(</span><span class="token string">'2008-01-02'</span><span class="token punctuation">,</span> <span class="token keyword">INTERVAL</span> <span class="token number">31</span> <span class="token keyword">DAY</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token string">'2008-02-02'</span></code></pre>
</div>
<p>
When invoked with the
<em class="replaceable">
<code>
days
</code>
</em>
form of
the second argument, MySQL treats it as an integer number of
days to be added to
<em class="replaceable">
<code>
expr
</code>
</em>
.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa98363321"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">ADDDATE</span><span class="token punctuation">(</span><span class="token string">'2008-01-02'</span><span class="token punctuation">,</span> <span class="token number">31</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token string">'2008-02-02'</span></code></pre>
</div>
<p>
This function returns
<code class="literal">
NULL
</code>
if
<em class="replaceable">
<code>
date
</code>
</em>
or
<em class="replaceable">
<code>
days
</code>
</em>
is
<code class="literal">
NULL
</code>
.
</p>
</li>
<li class="listitem">
<a name="function_addtime">
</a>
<p>
<a class="link" href="date-and-time-functions.html#function_addtime">
<code class="literal">
ADDTIME(
<em class="replaceable">
<code>
expr1
</code>
</em>
,
<em class="replaceable">
<code>
expr2
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045205342208">
</a>
<p>
<a class="link" href="date-and-time-functions.html#function_addtime">
<code class="literal">
ADDTIME()
</code>
</a>
adds
<em class="replaceable">
<code>
expr2
</code>
</em>
to
<em class="replaceable">
<code>
expr1
</code>
</em>
and returns the result.
<em class="replaceable">
<code>
expr1
</code>
</em>
is a time or datetime
expression, and
<em class="replaceable">
<code>
expr2
</code>
</em>
is a time
expression. Returns
<code class="literal">
NULL
</code>
if
<em class="replaceable">
<code>
expr1
</code>
</em>
or
<em class="replaceable">
<code>
expr2
</code>
</em>
is
<code class="literal">
NULL
</code>
.
</p>
<p>
The return type of this function and of the
<a class="link" href="date-and-time-functions.html#function_subtime">
<code class="literal">
SUBTIME()
</code>
</a>
function is
determined as follows:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
If the first argument is a dynamic parameter (such as in a
prepared statement), the return type is
<code class="literal">
TIME
</code>
.
</p>
</li>
<li class="listitem">
<p>
Otherwise, the resolved type of the function is derived
from the resolved type of the first argument.
</p>
</li>
</ul>
</div>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa98791089"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">ADDTIME</span><span class="token punctuation">(</span><span class="token string">'2007-12-31 23:59:59.999999'</span><span class="token punctuation">,</span> <span class="token string">'1 1:1:1.000002'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token string">'2008-01-02 01:01:01.000001'</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">ADDTIME</span><span class="token punctuation">(</span><span class="token string">'01:00:00.999999'</span><span class="token punctuation">,</span> <span class="token string">'02:00:00.999998'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token string">'03:00:01.999997'</span></code></pre>
</div>
</li>
<li class="listitem">
<a name="function_convert-tz">
</a>
<p>
<a class="link" href="date-and-time-functions.html#function_convert-tz">
<code class="literal">
CONVERT_TZ(
<em class="replaceable">
<code>
dt
</code>
</em>
,
<em class="replaceable">
<code>
from_tz
</code>
</em>
,
<em class="replaceable">
<code>
to_tz
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045205320208">
</a>
<p>
<a class="link" href="date-and-time-functions.html#function_convert-tz">
<code class="literal">
CONVERT_TZ()
</code>
</a>
converts a
datetime value
<em class="replaceable">
<code>
dt
</code>
</em>
from the time
zone given by
<em class="replaceable">
<code>
from_tz
</code>
</em>
to the time
zone given by
<em class="replaceable">
<code>
to_tz
</code>
</em>
and returns the
resulting value. Time zones are specified as described in
<a class="xref" href="time-zone-support.html" title="7.1.15 MySQL Server Time Zone Support">
Section 7.1.15, “MySQL Server Time Zone Support”
</a>
. This function returns
<code class="literal">
NULL
</code>
if any of the arguments are invalid,
or if any of them are
<code class="literal">
NULL
</code>
.
</p>
<p>
On 32-bit platforms, the supported range of values for this
function is the same as for the
<a class="link" href="datetime.html" title="13.2.2 The DATE, DATETIME, and TIMESTAMP Types">
<code class="literal">
TIMESTAMP
</code>
</a>
type (see
<a class="xref" href="date-and-time-type-syntax.html" title="13.2.1 Date and Time Data Type Syntax">
Section 13.2.1, “Date and Time Data Type Syntax”
</a>
, for range
information). On 64-bit platforms, the maximum supported value
is
<code class="literal">
'3001-01-18 23:59:59.999999'
</code>
UTC.
</p>
<p>
Regardless of platform or MySQL version, if the value falls
out of the supported range when converted from
<em class="replaceable">
<code>
from_tz
</code>
</em>
to UTC, no conversion
occurs.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa77285895"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">CONVERT_TZ</span><span class="token punctuation">(</span><span class="token string">'2004-01-01 12:00:00'</span><span class="token punctuation">,</span><span class="token string">'GMT'</span><span class="token punctuation">,</span><span class="token string">'MET'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token string">'2004-01-01 13:00:00'</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">CONVERT_TZ</span><span class="token punctuation">(</span><span class="token string">'2004-01-01 12:00:00'</span><span class="token punctuation">,</span><span class="token string">'+00:00'</span><span class="token punctuation">,</span><span class="token string">'+10:00'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token string">'2004-01-01 22:00:00'</span></code></pre>
</div>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
To use named time zones such as
<code class="literal">
'MET'
</code>
or
<code class="literal">
'Europe/Amsterdam'
</code>
, the time zone tables
must be properly set up. For instructions, see
<a class="xref" href="time-zone-support.html" title="7.1.15 MySQL Server Time Zone Support">
Section 7.1.15, “MySQL Server Time Zone Support”
</a>
.
</p>
</div>
</li>
<li class="listitem">
<a name="function_curdate">
</a>
<p>
<a class="link" href="date-and-time-functions.html#function_curdate">
<code class="literal">
CURDATE()
</code>
</a>
</p>
<a class="indexterm" name="idm46045205297360">
</a>
<p>
Returns the current date as a value in
<code class="literal">
'
<em class="replaceable">
<code>
YYYY-MM-DD
</code>
</em>
'
</code>
or
<em class="replaceable">
<code>
YYYYMMDD
</code>
</em>
format, depending on
whether the function is used in string or numeric context.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa47148947"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">CURDATE</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token string">'2008-06-13'</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">CURDATE</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token operator">+</span> <span class="token number">0</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token number">20080613</span></code></pre>
</div>
</li>
<li class="listitem">
<a name="function_current-date">
</a>
<p>
<a class="link" href="date-and-time-functions.html#function_current-date">
<code class="literal">
CURRENT_DATE
</code>
</a>
,
<a class="link" href="date-and-time-functions.html#function_current-date">
<code class="literal">
CURRENT_DATE()
</code>
</a>
</p>
<a class="indexterm" name="idm46045205283984">
</a>
<p>
<a class="link" href="date-and-time-functions.html#function_current-date">
<code class="literal">
CURRENT_DATE
</code>
</a>
and
<a class="link" href="date-and-time-functions.html#function_current-date">
<code class="literal">
CURRENT_DATE()
</code>
</a>
are synonyms for
<a class="link" href="date-and-time-functions.html#function_curdate">
<code class="literal">
CURDATE()
</code>
</a>
.
</p>
</li>
<li class="listitem">
<a name="function_current-time">
</a>
<p>
<a class="link" href="date-and-time-functions.html#function_current-time">
<code class="literal">
CURRENT_TIME
</code>
</a>
,
<a class="link" href="date-and-time-functions.html#function_current-time">
<code class="literal">
CURRENT_TIME([
<em class="replaceable">
<code>
fsp
</code>
</em>
])
</code>
</a>
</p>
<a class="indexterm" name="idm46045205271184">
</a>
<p>
<a class="link" href="date-and-time-functions.html#function_current-time">
<code class="literal">
CURRENT_TIME
</code>
</a>
and
<a class="link" href="date-and-time-functions.html#function_current-time">
<code class="literal">
CURRENT_TIME()
</code>
</a>
are synonyms for
<a class="link" href="date-and-time-functions.html#function_curtime">
<code class="literal">
CURTIME()
</code>
</a>
.
</p>
</li>
<li class="listitem">
<a name="function_current-timestamp">
</a>
<p>
<a class="link" href="date-and-time-functions.html#function_current-timestamp">
<code class="literal">
CURRENT_TIMESTAMP
</code>
</a>
,
<a class="link" href="date-and-time-functions.html#function_current-timestamp">
<code class="literal">
CURRENT_TIMESTAMP([
<em class="replaceable">
<code>
fsp
</code>
</em>
])
</code>
</a>
</p>
<a class="indexterm" name="idm46045205258304">
</a>
<p>
<a class="link" href="date-and-time-functions.html#function_current-timestamp">
<code class="literal">
CURRENT_TIMESTAMP
</code>
</a>
and
<a class="link" href="date-and-time-functions.html#function_current-timestamp">
<code class="literal">
CURRENT_TIMESTAMP()
</code>
</a>
are
synonyms for
<a class="link" href="date-and-time-functions.html#function_now">
<code class="literal">
NOW()
</code>
</a>
.
</p>
</li>
<li class="listitem">
<a name="function_curtime">
</a>
<p>
<a class="link" href="date-and-time-functions.html#function_curtime">
<code class="literal">
CURTIME([
<em class="replaceable">
<code>
fsp
</code>
</em>
])
</code>
</a>
</p>
<a class="indexterm" name="idm46045205246720">
</a>
<p>
Returns the current time as a value in
<em class="replaceable">
<code>
'hh:mm:ss'
</code>
</em>
or
<em class="replaceable">
<code>
hhmmss
</code>
</em>
format, depending on whether
the function is used in string or numeric context. The value
is expressed in the session time zone.
</p>
<p>
If the
<em class="replaceable">
<code>
fsp
</code>
</em>
argument is given to
specify a fractional seconds precision from 0 to 6, the return
value includes a fractional seconds part of that many digits.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa99899176"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">CURTIME</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> CURTIME() <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 19:25:37 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">CURTIME</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token operator">+</span> <span class="token number">0</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> CURTIME() <span class="token punctuation">+</span> 0 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 192537 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">CURTIME</span><span class="token punctuation">(</span><span class="token number">3</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> CURTIME(3) <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 19:25:37.840 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
</div>
</li>
<li class="listitem">
<a name="function_date">
</a>
<p>
<a class="link" href="date-and-time-functions.html#function_date">
<code class="literal">
DATE(
<em class="replaceable">
<code>
expr
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045205232720">
</a>
<p>
Extracts the date part of the date or datetime expression
<em class="replaceable">
<code>
expr
</code>
</em>
. Returns
<code class="literal">
NULL
</code>
if
<em class="replaceable">
<code>
expr
</code>
</em>
is
<code class="literal">
NULL
</code>
.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa21734437"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">DATE</span><span class="token punctuation">(</span><span class="token string">'2003-12-31 01:02:03'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token string">'2003-12-31'</span></code></pre>
</div>
</li>
<li class="listitem">
<a name="function_datediff">
</a>
<p>
<a class="link" href="date-and-time-functions.html#function_datediff">
<code class="literal">
DATEDIFF(
<em class="replaceable">
<code>
expr1
</code>
</em>
,
<em class="replaceable">
<code>
expr2
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045205219728">
</a>
<p>
<a class="link" href="date-and-time-functions.html#function_datediff">
<code class="literal">
DATEDIFF()
</code>
</a>
returns
<em class="replaceable">
<code>
expr1
</code>
</em>
−
<em class="replaceable">
<code>
expr2
</code>
</em>
expressed as a value in days
from one date to the other.
<em class="replaceable">
<code>
expr1
</code>
</em>
and
<em class="replaceable">
<code>
expr2
</code>
</em>
are date or date-and-time
expressions. Only the date parts of the values are used in the
calculation.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa7667195"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">DATEDIFF</span><span class="token punctuation">(</span><span class="token string">'2007-12-31 23:59:59'</span><span class="token punctuation">,</span><span class="token string">'2007-12-30'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token number">1</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">DATEDIFF</span><span class="token punctuation">(</span><span class="token string">'2010-11-30 23:59:59'</span><span class="token punctuation">,</span><span class="token string">'2010-12-31'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token operator">-</span><span class="token number">31</span></code></pre>
</div>
<p>
This function returns
<code class="literal">
NULL
</code>
if
<em class="replaceable">
<code>
expr1
</code>
</em>
or
<em class="replaceable">
<code>
expr2
</code>
</em>
is
<code class="literal">
NULL
</code>
.
</p>
</li>
<li class="listitem">
<a name="function_date-add">
</a>
<p>
<a class="link" href="date-and-time-functions.html#function_date-add">
<code class="literal">
DATE_ADD(
<em class="replaceable">
<code>
date
</code>
</em>
,INTERVAL
<em class="replaceable">
<code>
expr
</code>
</em>
<em class="replaceable">
<code>
unit
</code>
</em>
)
</code>
</a>
,
<a class="link" href="date-and-time-functions.html#function_date-sub">
<code class="literal">
DATE_SUB(
<em class="replaceable">
<code>
date
</code>
</em>
,INTERVAL
<em class="replaceable">
<code>
expr
</code>
</em>
<em class="replaceable">
<code>
unit
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045205199376">
</a>
<a class="indexterm" name="idm46045205198304">
</a>
<p>
These functions perform date arithmetic. The
<em class="replaceable">
<code>
date
</code>
</em>
argument specifies the
starting date or datetime value.
<em class="replaceable">
<code>
expr
</code>
</em>
is an expression specifying
the interval value to be added or subtracted from the starting
date.
<em class="replaceable">
<code>
expr
</code>
</em>
is evaluated as a
string; it may start with a
<code class="literal">
-
</code>
for negative
intervals.
<em class="replaceable">
<code>
unit
</code>
</em>
is a keyword
indicating the units in which the expression should be
interpreted.
</p>
<p>
For more information about temporal interval syntax, including
a full list of
<em class="replaceable">
<code>
unit
</code>
</em>
specifiers, the
expected form of the
<em class="replaceable">
<code>
expr
</code>
</em>
argument
for each
<em class="replaceable">
<code>
unit
</code>
</em>
value, and rules for
operand interpretation in temporal arithmetic, see
<a class="xref" href="expressions.html#temporal-intervals" title="Temporal Intervals">
Temporal Intervals
</a>
.
</p>
<p>
The return value depends on the arguments:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
If
<em class="replaceable">
<code>
date
</code>
</em>
is
<code class="literal">
NULL
</code>
, the function returns
<code class="literal">
NULL
</code>
.
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="datetime.html" title="13.2.2 The DATE, DATETIME, and TIMESTAMP Types">
<code class="literal">
DATE
</code>
</a>
if the
<em class="replaceable">
<code>
date
</code>
</em>
argument is a
<a class="link" href="datetime.html" title="13.2.2 The DATE, DATETIME, and TIMESTAMP Types">
<code class="literal">
DATE
</code>
</a>
value and your
calculations involve only
<code class="literal">
YEAR
</code>
,
<code class="literal">
MONTH
</code>
, and
<code class="literal">
DAY
</code>
parts
(that is, no time parts).
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="time.html" title="13.2.3 The TIME Type">
<code class="literal">
TIME
</code>
</a>
if the
<em class="replaceable">
<code>
date
</code>
</em>
argument is a
<code class="literal">
TIME
</code>
value and the calculations involve
only
<code class="literal">
HOURS
</code>
,
<code class="literal">
MINUTES
</code>
,
and
<code class="literal">
SECONDS
</code>
parts (that is, no date
parts).
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="datetime.html" title="13.2.2 The DATE, DATETIME, and TIMESTAMP Types">
<code class="literal">
DATETIME
</code>
</a>
if the first
argument is a
<a class="link" href="datetime.html" title="13.2.2 The DATE, DATETIME, and TIMESTAMP Types">
<code class="literal">
DATETIME
</code>
</a>
(or
<a class="link" href="datetime.html" title="13.2.2 The DATE, DATETIME, and TIMESTAMP Types">
<code class="literal">
TIMESTAMP
</code>
</a>
) value, or if the
first argument is a
<a class="link" href="datetime.html" title="13.2.2 The DATE, DATETIME, and TIMESTAMP Types">
<code class="literal">
DATE
</code>
</a>
and the
<em class="replaceable">
<code>
unit
</code>
</em>
value uses
<code class="literal">
HOURS
</code>
,
<code class="literal">
MINUTES
</code>
, or
<code class="literal">
SECONDS
</code>
, or if the first argument is of
type
<a class="link" href="time.html" title="13.2.3 The TIME Type">
<code class="literal">
TIME
</code>
</a>
and the
<em class="replaceable">
<code>
unit
</code>
</em>
value uses
<code class="literal">
YEAR
</code>
,
<code class="literal">
MONTH
</code>
, or
<code class="literal">
DAY
</code>
.
</p>
</li>
<li class="listitem">
<p>
If the first argument is a dynamic parameter (for example,
of a prepared statement), its resolved type is
<code class="literal">
DATE
</code>
if the second argument is an
interval that contains some combination of
<code class="literal">
YEAR
</code>
,
<code class="literal">
MONTH
</code>
, or
<code class="literal">
DAY
</code>
values only; otherwise, its type is
<code class="literal">
DATETIME
</code>
.
</p>
</li>
<li class="listitem">
<p>
String otherwise (type
<a class="link" href="char.html" title="13.3.2 The CHAR and VARCHAR Types">
<code class="literal">
VARCHAR
</code>
</a>
).
</p>
</li>
</ul>
</div>
<p>
To ensure that the result is
<a class="link" href="datetime.html" title="13.2.2 The DATE, DATETIME, and TIMESTAMP Types">
<code class="literal">
DATETIME
</code>
</a>
, you can use
<a class="link" href="cast-functions.html#function_cast">
<code class="literal">
CAST()
</code>
</a>
to convert the first
argument to
<a class="link" href="datetime.html" title="13.2.2 The DATE, DATETIME, and TIMESTAMP Types">
<code class="literal">
DATETIME
</code>
</a>
.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa23168089"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">DATE_ADD</span><span class="token punctuation">(</span><span class="token string">'2018-05-01'</span><span class="token punctuation">,</span><span class="token keyword">INTERVAL</span> <span class="token number">1</span> <span class="token keyword">DAY</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token string">'2018-05-02'</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">DATE_SUB</span><span class="token punctuation">(</span><span class="token string">'2018-05-01'</span><span class="token punctuation">,</span><span class="token keyword">INTERVAL</span> <span class="token number">1</span> <span class="token datatype">YEAR</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token string">'2017-05-01'</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">DATE_ADD</span><span class="token punctuation">(</span><span class="token string">'2020-12-31 23:59:59'</span><span class="token punctuation">,</span>
<span class="token prompt"> -></span> <span class="token keyword">INTERVAL</span> <span class="token number">1</span> <span class="token keyword">SECOND</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token string">'2021-01-01 00:00:00'</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">DATE_ADD</span><span class="token punctuation">(</span><span class="token string">'2018-12-31 23:59:59'</span><span class="token punctuation">,</span>
<span class="token prompt"> -></span> <span class="token keyword">INTERVAL</span> <span class="token number">1</span> <span class="token keyword">DAY</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token string">'2019-01-01 23:59:59'</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">DATE_ADD</span><span class="token punctuation">(</span><span class="token string">'2100-12-31 23:59:59'</span><span class="token punctuation">,</span>
<span class="token prompt"> -></span> <span class="token keyword">INTERVAL</span> <span class="token string">'1:1'</span> <span class="token keyword">MINUTE_SECOND</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token string">'2101-01-01 00:01:00'</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">DATE_SUB</span><span class="token punctuation">(</span><span class="token string">'2025-01-01 00:00:00'</span><span class="token punctuation">,</span>
<span class="token prompt"> -></span> <span class="token keyword">INTERVAL</span> <span class="token string">'1 1:1:1'</span> <span class="token keyword">DAY_SECOND</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token string">'2024-12-30 22:58:59'</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">DATE_ADD</span><span class="token punctuation">(</span><span class="token string">'1900-01-01 00:00:00'</span><span class="token punctuation">,</span>
<span class="token prompt"> -></span> <span class="token keyword">INTERVAL</span> <span class="token string">'-1 10'</span> <span class="token keyword">DAY_HOUR</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token string">'1899-12-30 14:00:00'</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">DATE_SUB</span><span class="token punctuation">(</span><span class="token string">'1998-01-02'</span><span class="token punctuation">,</span> <span class="token keyword">INTERVAL</span> <span class="token number">31</span> <span class="token keyword">DAY</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token string">'1997-12-02'</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">DATE_ADD</span><span class="token punctuation">(</span><span class="token string">'1992-12-31 23:59:59.000002'</span><span class="token punctuation">,</span>
<span class="token prompt"> -></span> <span class="token keyword">INTERVAL</span> <span class="token string">'1.999999'</span> <span class="token keyword">SECOND_MICROSECOND</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token string">'1993-01-01 00:00:01.000001'</span></code></pre>
</div>
<p>
When adding a
<code class="literal">
MONTH
</code>
interval to a
<code class="literal">
DATE
</code>
or
<code class="literal">
DATETIME
</code>
value,
and the resulting date includes a day that does not exist in
the given month, the day is adjusted to the last day of the
month, as shown here:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa56989440"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">DATE_ADD</span><span class="token punctuation">(</span><span class="token string">'2024-03-30'</span><span class="token punctuation">,</span> <span class="token keyword">INTERVAL</span> <span class="token number">1</span> <span class="token keyword">MONTH</span><span class="token punctuation">)</span> <span class="token keyword">AS</span> d1<span class="token punctuation">,</span>
<span class="token operator">></span> <span class="token function">DATE_ADD</span><span class="token punctuation">(</span><span class="token string">'2024-03-31'</span><span class="token punctuation">,</span> <span class="token keyword">INTERVAL</span> <span class="token number">1</span> <span class="token keyword">MONTH</span><span class="token punctuation">)</span> <span class="token keyword">AS</span> d2<span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> d1 <span class="token punctuation">|</span> d2 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 2024<span class="token punctuation">-</span>04<span class="token punctuation">-</span>30 <span class="token punctuation">|</span> 2024<span class="token punctuation">-</span>04<span class="token punctuation">-</span>30 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output">1 row in set (0.00 sec)</span></code></pre>
</div>
</li>
<li class="listitem">
<a name="function_date-format">
</a>
<p>
<a class="link" href="date-and-time-functions.html#function_date-format">
<code class="literal">
DATE_FORMAT(
<em class="replaceable">
<code>
date
</code>
</em>
,
<em class="replaceable">
<code>
format
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045205127808">
</a>
<p>
Formats the
<em class="replaceable">
<code>
date
</code>
</em>
value according to
the
<em class="replaceable">
<code>
format
</code>
</em>
string. If either
argument is
<code class="literal">
NULL
</code>
, the function returns
<code class="literal">
NULL
</code>
.
</p>
<p>
The specifiers shown in the following table may be used in the
<em class="replaceable">
<code>
format
</code>
</em>
string. The
<code class="literal">
%
</code>
character is required before format
specifier characters. The specifiers apply to other functions
as well:
<a class="link" href="date-and-time-functions.html#function_str-to-date">
<code class="literal">
STR_TO_DATE()
</code>
</a>
,
<a class="link" href="date-and-time-functions.html#function_time-format">
<code class="literal">
TIME_FORMAT()
</code>
</a>
,
<a class="link" href="date-and-time-functions.html#function_unix-timestamp">
<code class="literal">
UNIX_TIMESTAMP()
</code>
</a>
.
</p>
<div class="informaltable">
<table summary="Specifier characters for the DATE_FORMAT function that may be used in the format string and provides a description of each specifier character.">
<colgroup>
<col style="width: 20%"/>
<col style="width: 70%"/>
</colgroup>
<thead>
<tr>
<th>
Specifier
</th>
<th>
Description
</th>
</tr>
</thead>
<tbody>
<tr>
<td>
<code class="literal">
%a
</code>
</td>
<td>
Abbreviated weekday name
(
<code class="literal">
Sun
</code>
..
<code class="literal">
Sat
</code>
)
</td>
</tr>
<tr>
<td>
<code class="literal">
%b
</code>
</td>
<td>
Abbreviated month name (
<code class="literal">
Jan
</code>
..
<code class="literal">
Dec
</code>
)
</td>
</tr>
<tr>
<td>
<code class="literal">
%c
</code>
</td>
<td>
Month, numeric (
<code class="literal">
0
</code>
..
<code class="literal">
12
</code>
)
</td>
</tr>
<tr>
<td>
<code class="literal">
%D
</code>
</td>
<td>
Day of the month with English suffix (
<code class="literal">
0th
</code>
,
<code class="literal">
1st
</code>
,
<code class="literal">
2nd
</code>
,
<code class="literal">
3rd
</code>
, …)
</td>
</tr>
<tr>
<td>
<code class="literal">
%d
</code>
</td>
<td>
Day of the month, numeric (
<code class="literal">
00
</code>
..
<code class="literal">
31
</code>
)
</td>
</tr>
<tr>
<td>
<code class="literal">
%e
</code>
</td>
<td>
Day of the month, numeric (
<code class="literal">
0
</code>
..
<code class="literal">
31
</code>
)
</td>
</tr>
<tr>
<td>
<code class="literal">
%f
</code>
</td>
<td>
Microseconds (
<code class="literal">
000000
</code>
..
<code class="literal">
999999
</code>
)
</td>
</tr>
<tr>
<td>
<code class="literal">
%H
</code>
</td>
<td>
Hour (
<code class="literal">
00
</code>
..
<code class="literal">
23
</code>
)
</td>
</tr>
<tr>
<td>
<code class="literal">
%h
</code>
</td>
<td>
Hour (
<code class="literal">
01
</code>
..
<code class="literal">
12
</code>
)
</td>
</tr>
<tr>
<td>
<code class="literal">
%I
</code>
</td>
<td>
Hour (
<code class="literal">
01
</code>
..
<code class="literal">
12
</code>
)
</td>
</tr>
<tr>
<td>
<code class="literal">
%i
</code>
</td>
<td>
Minutes, numeric (
<code class="literal">
00
</code>
..
<code class="literal">
59
</code>
)
</td>
</tr>
<tr>
<td>
<code class="literal">
%j
</code>
</td>
<td>
Day of year (
<code class="literal">
001
</code>
..
<code class="literal">
366
</code>
)
</td>
</tr>
<tr>
<td>
<code class="literal">
%k
</code>
</td>
<td>
Hour (
<code class="literal">
0
</code>
..
<code class="literal">
23
</code>
)
</td>
</tr>
<tr>
<td>
<code class="literal">
%l
</code>
</td>
<td>
Hour (
<code class="literal">
1
</code>
..
<code class="literal">
12
</code>
)
</td>
</tr>
<tr>
<td>
<code class="literal">
%M
</code>
</td>
<td>
Month name (
<code class="literal">
January
</code>
..
<code class="literal">
December
</code>
)
</td>
</tr>
<tr>
<td>
<code class="literal">
%m
</code>
</td>
<td>
Month, numeric (
<code class="literal">
00
</code>
..
<code class="literal">
12
</code>
)
</td>
</tr>
<tr>
<td>
<code class="literal">
%p
</code>
</td>
<td>
<code class="literal">
AM
</code>
or
<code class="literal">
PM
</code>
</td>
</tr>
<tr>
<td>
<code class="literal">
%r
</code>
</td>
<td>
Time, 12-hour (
<em class="replaceable">
<code>
hh:mm:ss
</code>
</em>
followed by
<code class="literal">
AM
</code>
or
<code class="literal">
PM
</code>
)
</td>
</tr>
<tr>
<td>
<code class="literal">
%S
</code>
</td>
<td>
Seconds (
<code class="literal">
00
</code>
..
<code class="literal">
59
</code>
)
</td>
</tr>
<tr>
<td>
<code class="literal">
%s
</code>
</td>
<td>
Seconds (
<code class="literal">
00
</code>
..
<code class="literal">
59
</code>
)
</td>
</tr>
<tr>
<td>
<code class="literal">
%T
</code>
</td>
<td>
Time, 24-hour (
<em class="replaceable">
<code>
hh:mm:ss
</code>
</em>
)
</td>
</tr>
<tr>
<td>
<code class="literal">
%U
</code>
</td>
<td>
Week (
<code class="literal">
00
</code>
..
<code class="literal">
53
</code>
), where Sunday is the
first day of the week;
<a class="link" href="date-and-time-functions.html#function_week">
<code class="literal">
WEEK()
</code>
</a>
mode 0
</td>
</tr>
<tr>
<td>
<code class="literal">
%u
</code>
</td>
<td>
Week (
<code class="literal">
00
</code>
..
<code class="literal">
53
</code>
), where Monday is the
first day of the week;
<a class="link" href="date-and-time-functions.html#function_week">
<code class="literal">
WEEK()
</code>
</a>
mode 1
</td>
</tr>
<tr>
<td>
<code class="literal">
%V
</code>
</td>
<td>
Week (
<code class="literal">
01
</code>
..
<code class="literal">
53
</code>
), where Sunday is the
first day of the week;
<a class="link" href="date-and-time-functions.html#function_week">
<code class="literal">
WEEK()
</code>
</a>
mode 2; used with
<code class="literal">
%X
</code>
</td>
</tr>
<tr>
<td>
<code class="literal">
%v
</code>
</td>
<td>
Week (
<code class="literal">
01
</code>
..
<code class="literal">
53
</code>
), where Monday is the
first day of the week;
<a class="link" href="date-and-time-functions.html#function_week">
<code class="literal">
WEEK()
</code>
</a>
mode 3; used with
<code class="literal">
%x
</code>
</td>
</tr>
<tr>
<td>
<code class="literal">
%W
</code>
</td>
<td>
Weekday name (
<code class="literal">
Sunday
</code>
..
<code class="literal">
Saturday
</code>
)
</td>
</tr>
<tr>
<td>
<code class="literal">
%w
</code>
</td>
<td>
Day of the week
(
<code class="literal">
0
</code>
=Sunday..
<code class="literal">
6
</code>
=Saturday)
</td>
</tr>
<tr>
<td>
<code class="literal">
%X
</code>
</td>
<td>
Year for the week where Sunday is the first day of the week, numeric,
four digits; used with
<code class="literal">
%V
</code>
</td>
</tr>
<tr>
<td>
<code class="literal">
%x
</code>
</td>
<td>
Year for the week, where Monday is the first day of the week, numeric,
four digits; used with
<code class="literal">
%v
</code>
</td>
</tr>
<tr>
<td>
<code class="literal">
%Y
</code>
</td>
<td>
Year, numeric, four digits
</td>
</tr>
<tr>
<td>
<code class="literal">
%y
</code>
</td>
<td>
Year, numeric (two digits)
</td>
</tr>
<tr>
<td>
<code class="literal">
%%
</code>
</td>
<td>
A literal
<code class="literal">
%
</code>
character
</td>
</tr>
<tr>
<td>
<code class="literal">
%
<em class="replaceable">
<code>
x
</code>
</em>
</code>
</td>
<td>
<em class="replaceable">
<code>
x
</code>
</em>
, for any
<span class="quote">
“
<span class="quote">
<em class="replaceable">
<code>
x
</code>
</em>
</span>
”
</span>
not listed
above
</td>
</tr>
</tbody>
</table>
</div>
<div class="informaltable">
<table cellpadding="0" cellspacing="0" style="position: fixed; top: 0px; display: none; left: 431px; width: 709px;">
<thead>
<tr>
<th style="width: 157.328px;">
Specifier
</th>
<th style="width: 550.672px;">
Description
</th>
</tr>
</thead>
</table>
</div>
<p>
Ranges for the month and day specifiers begin with zero due to
the fact that MySQL permits the storing of incomplete dates
such as
<code class="literal">
'2014-00-00'
</code>
.
</p>
<p>
The language used for day and month names and abbreviations is
controlled by the value of the
<a class="link" href="server-system-variables.html#sysvar_lc_time_names">
<code class="literal">
lc_time_names
</code>
</a>
system variable
(
<a class="xref" href="locale-support.html" title="12.16 MySQL Server Locale Support">
Section 12.16, “MySQL Server Locale Support”
</a>
).
</p>
<p>
For the
<code class="literal">
%U
</code>
,
<code class="literal">
%u
</code>
,
<code class="literal">
%V
</code>
, and
<code class="literal">
%v
</code>
specifiers,
see the description of the
<a class="link" href="date-and-time-functions.html#function_week">
<code class="literal">
WEEK()
</code>
</a>
function for information
about the mode values. The mode affects how week numbering
occurs.
</p>
<p>
<a class="link" href="date-and-time-functions.html#function_date-format">
<code class="literal">
DATE_FORMAT()
</code>
</a>
returns a string
with a character set and collation given by
<a class="link" href="server-system-variables.html#sysvar_character_set_connection">
<code class="literal">
character_set_connection
</code>
</a>
and
<a class="link" href="server-system-variables.html#sysvar_collation_connection">
<code class="literal">
collation_connection
</code>
</a>
so that
it can return month and weekday names containing non-ASCII
characters.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa69421949"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">DATE_FORMAT</span><span class="token punctuation">(</span><span class="token string">'2009-10-04 22:23:00'</span><span class="token punctuation">,</span> <span class="token string">'%W %M %Y'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token string">'Sunday October 2009'</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">DATE_FORMAT</span><span class="token punctuation">(</span><span class="token string">'2007-10-04 22:23:00'</span><span class="token punctuation">,</span> <span class="token string">'%H:%i:%s'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token string">'22:23:00'</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">DATE_FORMAT</span><span class="token punctuation">(</span><span class="token string">'1900-10-04 22:23:00'</span><span class="token punctuation">,</span>
<span class="token prompt"> -></span> <span class="token string">'%D %y %a %d %m %b %j'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token string">'4th 00 Thu 04 10 Oct 277'</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">DATE_FORMAT</span><span class="token punctuation">(</span><span class="token string">'1997-10-04 22:23:00'</span><span class="token punctuation">,</span>
<span class="token prompt"> -></span> <span class="token string">'%H %k %I %r %T %S %w'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token string">'22 22 10 10:23:00 PM 22:23:00 00 6'</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">DATE_FORMAT</span><span class="token punctuation">(</span><span class="token string">'1999-01-01'</span><span class="token punctuation">,</span> <span class="token string">'%X %V'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token string">'1998 52'</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">DATE_FORMAT</span><span class="token punctuation">(</span><span class="token string">'2006-06-00'</span><span class="token punctuation">,</span> <span class="token string">'%d'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token string">'00'</span></code></pre>
</div>
</li>
<li class="listitem">
<a name="function_date-sub">
</a>
<p>
<a class="link" href="date-and-time-functions.html#function_date-sub">
<code class="literal">
DATE_SUB(
<em class="replaceable">
<code>
date
</code>
</em>
,INTERVAL
<em class="replaceable">
<code>
expr
</code>
</em>
<em class="replaceable">
<code>
unit
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045204953808">
</a>
<p>
See the description for
<a class="link" href="date-and-time-functions.html#function_date-add">
<code class="literal">
DATE_ADD()
</code>
</a>
.
</p>
</li>
<li class="listitem">
<a name="function_day">
</a>
<p>
<a class="link" href="date-and-time-functions.html#function_day">
<code class="literal">
DAY(
<em class="replaceable">
<code>
date
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045204944736">
</a>
<p>
<a class="link" href="date-and-time-functions.html#function_day">
<code class="literal">
DAY()
</code>
</a>
is a synonym for
<a class="link" href="date-and-time-functions.html#function_dayofmonth">
<code class="literal">
DAYOFMONTH()
</code>
</a>
.
</p>
</li>
<li class="listitem">
<a name="function_dayname">
</a>
<p>
<a class="link" href="date-and-time-functions.html#function_dayname">
<code class="literal">
DAYNAME(
<em class="replaceable">
<code>
date
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045204934368">
</a>
<p>
Returns the name of the weekday for
<em class="replaceable">
<code>
date
</code>
</em>
. The language used for the
name is controlled by the value of the
<a class="link" href="server-system-variables.html#sysvar_lc_time_names">
<code class="literal">
lc_time_names
</code>
</a>
system variable
(see
<a class="xref" href="locale-support.html" title="12.16 MySQL Server Locale Support">
Section 12.16, “MySQL Server Locale Support”
</a>
). Returns
<code class="literal">
NULL
</code>
if
<em class="replaceable">
<code>
date
</code>
</em>
is
<code class="literal">
NULL
</code>
.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa88421390"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">DAYNAME</span><span class="token punctuation">(</span><span class="token string">'2007-02-03'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token string">'Saturday'</span></code></pre>
</div>
</li>
<li class="listitem">
<a name="function_dayofmonth">
</a>
<p>
<a class="link" href="date-and-time-functions.html#function_dayofmonth">
<code class="literal">
DAYOFMONTH(
<em class="replaceable">
<code>
date
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045204919888">
</a>
<p>
Returns the day of the month for
<em class="replaceable">
<code>
date
</code>
</em>
, in the range
<code class="literal">
1
</code>
to
<code class="literal">
31
</code>
, or
<code class="literal">
0
</code>
for dates such as
<code class="literal">
'0000-00-00'
</code>
or
<code class="literal">
'2008-00-00'
</code>
that have a zero day part.
Returns
<code class="literal">
NULL
</code>
if
<em class="replaceable">
<code>
date
</code>
</em>
is
<code class="literal">
NULL
</code>
.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa12279360"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">DAYOFMONTH</span><span class="token punctuation">(</span><span class="token string">'2007-02-03'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token number">3</span></code></pre>
</div>
</li>
<li class="listitem">
<a name="function_dayofweek">
</a>
<p>
<a class="link" href="date-and-time-functions.html#function_dayofweek">
<code class="literal">
DAYOFWEEK(
<em class="replaceable">
<code>
date
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045204903840">
</a>
<p>
Returns the weekday index for
<em class="replaceable">
<code>
date
</code>
</em>
(
<code class="literal">
1
</code>
= Sunday,
<code class="literal">
2
</code>
= Monday,
…,
<code class="literal">
7
</code>
= Saturday). These index values
correspond to the ODBC standard. Returns
<code class="literal">
NULL
</code>
if
<em class="replaceable">
<code>
date
</code>
</em>
is
<code class="literal">
NULL
</code>
.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa31891283"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">DAYOFWEEK</span><span class="token punctuation">(</span><span class="token string">'2007-02-03'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token number">7</span></code></pre>
</div>
</li>
<li class="listitem">
<a name="function_dayofyear">
</a>
<p>
<a class="link" href="date-and-time-functions.html#function_dayofyear">
<code class="literal">
DAYOFYEAR(
<em class="replaceable">
<code>
date
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045204889184">
</a>
<p>
Returns the day of the year for
<em class="replaceable">
<code>
date
</code>
</em>
, in the range
<code class="literal">
1
</code>
to
<code class="literal">
366
</code>
. Returns
<code class="literal">
NULL
</code>
if
<em class="replaceable">
<code>
date
</code>
</em>
is
<code class="literal">
NULL
</code>
.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa39143255"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">DAYOFYEAR</span><span class="token punctuation">(</span><span class="token string">'2007-02-03'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token number">34</span></code></pre>
</div>
</li>
<li class="listitem">
<a name="function_extract">
</a>
<p>
<a class="link" href="date-and-time-functions.html#function_extract">
<code class="literal">
EXTRACT(
<em class="replaceable">
<code>
unit
</code>
</em>
FROM
<em class="replaceable">
<code>
date
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045204874864">
</a>
<p>
The
<a class="link" href="date-and-time-functions.html#function_extract">
<code class="literal">
EXTRACT()
</code>
</a>
function uses the
same kinds of
<em class="replaceable">
<code>
unit
</code>
</em>
specifiers as
<a class="link" href="date-and-time-functions.html#function_date-add">
<code class="literal">
DATE_ADD()
</code>
</a>
or
<a class="link" href="date-and-time-functions.html#function_date-sub">
<code class="literal">
DATE_SUB()
</code>
</a>
, but extracts parts
from the date rather than performing date arithmetic. For
information on the
<em class="replaceable">
<code>
unit
</code>
</em>
argument,
see
<a class="xref" href="expressions.html#temporal-intervals" title="Temporal Intervals">
Temporal Intervals
</a>
. Returns
<code class="literal">
NULL
</code>
if
<em class="replaceable">
<code>
date
</code>
</em>
is
<code class="literal">
NULL
</code>
.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa69377489"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">EXTRACT</span><span class="token punctuation">(</span><span class="token datatype">YEAR</span> <span class="token keyword">FROM</span> <span class="token string">'2019-07-02'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token number">2019</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">EXTRACT</span><span class="token punctuation">(</span><span class="token keyword">YEAR_MONTH</span> <span class="token keyword">FROM</span> <span class="token string">'2019-07-02 01:02:03'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token number">201907</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">EXTRACT</span><span class="token punctuation">(</span><span class="token keyword">DAY_MINUTE</span> <span class="token keyword">FROM</span> <span class="token string">'2019-07-02 01:02:03'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token number">20102</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">EXTRACT</span><span class="token punctuation">(</span><span class="token keyword">MICROSECOND</span>
<span class="token prompt"> -></span> <span class="token keyword">FROM</span> <span class="token string">'2003-01-02 10:30:00.000123'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token number">123</span></code></pre>
</div>
</li>
<li class="listitem">
<a name="function_from-days">
</a>
<p>
<a class="link" href="date-and-time-functions.html#function_from-days">
<code class="literal">
FROM_DAYS(
<em class="replaceable">
<code>
N
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045204854320">
</a>
<p>
Given a day number
<em class="replaceable">
<code>
N
</code>
</em>
, returns a
<a class="link" href="datetime.html" title="13.2.2 The DATE, DATETIME, and TIMESTAMP Types">
<code class="literal">
DATE
</code>
</a>
value. Returns
<code class="literal">
NULL
</code>
if
<em class="replaceable">
<code>
N
</code>
</em>
is
<code class="literal">
NULL
</code>
.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa39363977"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">FROM_DAYS</span><span class="token punctuation">(</span><span class="token number">730669</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token string">'2000-07-03'</span></code></pre>
</div>
<p>
Use
<a class="link" href="date-and-time-functions.html#function_from-days">
<code class="literal">
FROM_DAYS()
</code>
</a>
with caution on
old dates. It is not intended for use with values that precede
the advent of the Gregorian calendar (1582). See
<a class="xref" href="mysql-calendar.html" title="13.2.7 What Calendar Is Used By MySQL?">
Section 13.2.7, “What Calendar Is Used By MySQL?”
</a>
.
</p>
</li>
<li class="listitem">
<a name="function_from-unixtime">
</a>
<p>
<a class="link" href="date-and-time-functions.html#function_from-unixtime">
<code class="literal">
FROM_UNIXTIME(
<em class="replaceable">
<code>
unix_timestamp
</code>
</em>
[,
<em class="replaceable">
<code>
format
</code>
</em>
])
</code>
</a>
</p>
<a class="indexterm" name="idm46045204837600">
</a>
<p>
Returns a representation of
<em class="replaceable">
<code>
unix_timestamp
</code>
</em>
as a datetime or
character string value. The value returned is expressed using
the session time zone. (Clients can set the session time zone
as described in
<a class="xref" href="time-zone-support.html" title="7.1.15 MySQL Server Time Zone Support">
Section 7.1.15, “MySQL Server Time Zone Support”
</a>
.)
<em class="replaceable">
<code>
unix_timestamp
</code>
</em>
is an internal
timestamp value representing seconds since
<code class="literal">
'1970-01-01 00:00:00'
</code>
UTC, such as produced
by the
<a class="link" href="date-and-time-functions.html#function_unix-timestamp">
<code class="literal">
UNIX_TIMESTAMP()
</code>
</a>
function.
</p>
<p>
If
<em class="replaceable">
<code>
format
</code>
</em>
is omitted, this function
returns a
<a class="link" href="datetime.html" title="13.2.2 The DATE, DATETIME, and TIMESTAMP Types">
<code class="literal">
DATETIME
</code>
</a>
value.
</p>
<p>
If
<em class="replaceable">
<code>
unix_timestamp
</code>
</em>
or
<em class="replaceable">
<code>
format
</code>
</em>
is
<code class="literal">
NULL
</code>
,
this function returns
<code class="literal">
NULL
</code>
.
</p>
<p>
If
<em class="replaceable">
<code>
unix_timestamp
</code>
</em>
is an integer,
the fractional seconds precision of the
<code class="literal">
DATETIME
</code>
is zero. When
<em class="replaceable">
<code>
unix_timestamp
</code>
</em>
is a decimal value,
the fractional seconds precision of the
<code class="literal">
DATETIME
</code>
is the same as the precision of
the decimal value, up to a maximum of 6. When
<em class="replaceable">
<code>
unix_timestamp
</code>
</em>
is a floating point
number, the fractional seconds precision of the datetime is 6.
</p>
<p>
On 32-bit platforms, the maximum useful value for
<em class="replaceable">
<code>
unix_timestamp
</code>
</em>
is
2147483647.999999, which returns
<code class="literal">
'2038-01-19
03:14:07.999999'
</code>
UTC. On 64-bit platforms, the
effective maximum is 32536771199.999999, which returns
<code class="literal">
'3001-01-18 23:59:59.999999'
</code>
UTC.
Regardless of platform or version, a greater value for
<em class="replaceable">
<code>
unix_timestamp
</code>
</em>
than the effective
maximum returns
<code class="literal">
0
</code>
.
</p>
<p>
<em class="replaceable">
<code>
format
</code>
</em>
is used to format the result
in the same way as the format string used for the
<a class="link" href="date-and-time-functions.html#function_date-format">
<code class="literal">
DATE_FORMAT()
</code>
</a>
function. If
<em class="replaceable">
<code>
format
</code>
</em>
is supplied, the value
returned is a
<a class="link" href="char.html" title="13.3.2 The CHAR and VARCHAR Types">
<code class="literal">
VARCHAR
</code>
</a>
.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa9323320"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">FROM_UNIXTIME</span><span class="token punctuation">(</span><span class="token number">1447430881</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token string">'2015-11-13 10:08:01'</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">FROM_UNIXTIME</span><span class="token punctuation">(</span><span class="token number">1447430881</span><span class="token punctuation">)</span> <span class="token operator">+</span> <span class="token number">0</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token number">20151113100801</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">FROM_UNIXTIME</span><span class="token punctuation">(</span><span class="token number">1447430881</span><span class="token punctuation">,</span>
<span class="token prompt"> -></span> <span class="token string">'%Y %D %M %h:%i:%s %x'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token string">'2015 13th November 10:08:01 2015'</span></code></pre>
</div>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
If you use
<a class="link" href="date-and-time-functions.html#function_unix-timestamp">
<code class="literal">
UNIX_TIMESTAMP()
</code>
</a>
and
<a class="link" href="date-and-time-functions.html#function_from-unixtime">
<code class="literal">
FROM_UNIXTIME()
</code>
</a>
to
convert between values in a non-UTC time zone and Unix
timestamp values, the conversion is lossy because the
mapping is not one-to-one in both directions. For details,
see the description of the
<a class="link" href="date-and-time-functions.html#function_unix-timestamp">
<code class="literal">
UNIX_TIMESTAMP()
</code>
</a>
function.
</p>
</div>
</li>
<li class="listitem">
<a name="function_get-format">
</a>
<p>
<a class="link" href="date-and-time-functions.html#function_get-format">
<code class="literal">
GET_FORMAT({DATE|TIME|DATETIME},
{'EUR'|'USA'|'JIS'|'ISO'|'INTERNAL'})
</code>
</a>
</p>
<a class="indexterm" name="idm46045204800704">
</a>
<p>
Returns a format string. This function is useful in
combination with the
<a class="link" href="date-and-time-functions.html#function_date-format">
<code class="literal">
DATE_FORMAT()
</code>
</a>
and the
<a class="link" href="date-and-time-functions.html#function_str-to-date">
<code class="literal">
STR_TO_DATE()
</code>
</a>
functions.
</p>
<p>
If
<em class="replaceable">
<code>
format
</code>
</em>
is
<code class="literal">
NULL
</code>
, this function returns
<code class="literal">
NULL
</code>
.
</p>
<p>
The possible values for the first and second arguments result
in several possible format strings (for the specifiers used,
see the table in the
<a class="link" href="date-and-time-functions.html#function_date-format">
<code class="literal">
DATE_FORMAT()
</code>
</a>
function
description). ISO format refers to ISO 9075, not ISO 8601.
</p>
<div class="informaltable">
<table summary="Function calls for the GET_FORMAT function along with results for each function call.">
<colgroup>
<col style="width: 60%"/>
<col style="width: 40%"/>
</colgroup>
<thead>
<tr>
<th>
Function Call
</th>
<th>
Result
</th>
</tr>
</thead>
<tbody>
<tr>
<td>
<a class="link" href="date-and-time-functions.html#function_get-format">
<code class="literal">
GET_FORMAT(DATE,'USA')
</code>
</a>
</td>
<td>
<code class="literal">
'%m.%d.%Y'
</code>
</td>
</tr>
<tr>
<td>
<a class="link" href="date-and-time-functions.html#function_get-format">
<code class="literal">
GET_FORMAT(DATE,'JIS')
</code>
</a>
</td>
<td>
<code class="literal">
'%Y-%m-%d'
</code>
</td>
</tr>
<tr>
<td>
<a class="link" href="date-and-time-functions.html#function_get-format">
<code class="literal">
GET_FORMAT(DATE,'ISO')
</code>
</a>
</td>
<td>
<code class="literal">
'%Y-%m-%d'
</code>
</td>
</tr>
<tr>
<td>
<a class="link" href="date-and-time-functions.html#function_get-format">
<code class="literal">
GET_FORMAT(DATE,'EUR')
</code>
</a>
</td>
<td>
<code class="literal">
'%d.%m.%Y'
</code>
</td>
</tr>
<tr>
<td>
<a class="link" href="date-and-time-functions.html#function_get-format">
<code class="literal">
GET_FORMAT(DATE,'INTERNAL')
</code>
</a>
</td>
<td>
<code class="literal">
'%Y%m%d'
</code>
</td>
</tr>
<tr>
<td>
<a class="link" href="date-and-time-functions.html#function_get-format">
<code class="literal">
GET_FORMAT(DATETIME,'USA')
</code>
</a>
</td>
<td>
<code class="literal">
'%Y-%m-%d %H.%i.%s'
</code>
</td>
</tr>
<tr>
<td>
<a class="link" href="date-and-time-functions.html#function_get-format">
<code class="literal">
GET_FORMAT(DATETIME,'JIS')
</code>
</a>
</td>
<td>
<code class="literal">
'%Y-%m-%d %H:%i:%s'
</code>
</td>
</tr>
<tr>
<td>
<a class="link" href="date-and-time-functions.html#function_get-format">
<code class="literal">
GET_FORMAT(DATETIME,'ISO')
</code>
</a>
</td>
<td>
<code class="literal">
'%Y-%m-%d %H:%i:%s'
</code>
</td>
</tr>
<tr>
<td>
<a class="link" href="date-and-time-functions.html#function_get-format">
<code class="literal">
GET_FORMAT(DATETIME,'EUR')
</code>
</a>
</td>
<td>
<code class="literal">
'%Y-%m-%d %H.%i.%s'
</code>
</td>
</tr>
<tr>
<td>
<a class="link" href="date-and-time-functions.html#function_get-format">
<code class="literal">
GET_FORMAT(DATETIME,'INTERNAL')
</code>
</a>
</td>
<td>
<code class="literal">
'%Y%m%d%H%i%s'
</code>
</td>
</tr>
<tr>
<td>
<a class="link" href="date-and-time-functions.html#function_get-format">
<code class="literal">
GET_FORMAT(TIME,'USA')
</code>
</a>
</td>
<td>
<code class="literal">
'%h:%i:%s %p'
</code>
</td>
</tr>
<tr>
<td>
<a class="link" href="date-and-time-functions.html#function_get-format">
<code class="literal">
GET_FORMAT(TIME,'JIS')
</code>
</a>
</td>
<td>
<code class="literal">
'%H:%i:%s'
</code>
</td>
</tr>
<tr>
<td>
<a class="link" href="date-and-time-functions.html#function_get-format">
<code class="literal">
GET_FORMAT(TIME,'ISO')
</code>
</a>
</td>
<td>
<code class="literal">
'%H:%i:%s'
</code>
</td>
</tr>
<tr>
<td>
<a class="link" href="date-and-time-functions.html#function_get-format">
<code class="literal">
GET_FORMAT(TIME,'EUR')
</code>
</a>
</td>
<td>
<code class="literal">
'%H.%i.%s'
</code>
</td>
</tr>
<tr>
<td>
<a class="link" href="date-and-time-functions.html#function_get-format">
<code class="literal">
GET_FORMAT(TIME,'INTERNAL')
</code>
</a>
</td>
<td>
<code class="literal">
'%H%i%s'
</code>
</td>
</tr>
</tbody>
</table>
</div>
<div class="informaltable">
<table cellpadding="0" cellspacing="0" style="position: fixed; top: 0px; display: none; left: 431px; width: 432px;">
<thead>
<tr>
<th style="width: 258.891px;">
Function Call
</th>
<th style="width: 172.594px;">
Result
</th>
</tr>
</thead>
</table>
</div>
<p>
<a class="link" href="datetime.html" title="13.2.2 The DATE, DATETIME, and TIMESTAMP Types">
<code class="literal">
TIMESTAMP
</code>
</a>
can also be used as
the first argument to
<a class="link" href="date-and-time-functions.html#function_get-format">
<code class="literal">
GET_FORMAT()
</code>
</a>
, in which case the
function returns the same values as for
<a class="link" href="datetime.html" title="13.2.2 The DATE, DATETIME, and TIMESTAMP Types">
<code class="literal">
DATETIME
</code>
</a>
.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa36989675"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">DATE_FORMAT</span><span class="token punctuation">(</span><span class="token string">'2003-10-03'</span><span class="token punctuation">,</span><span class="token function">GET_FORMAT</span><span class="token punctuation">(</span><span class="token datatype">DATE</span><span class="token punctuation">,</span><span class="token string">'EUR'</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token string">'03.10.2003'</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">STR_TO_DATE</span><span class="token punctuation">(</span><span class="token string">'10.31.2003'</span><span class="token punctuation">,</span><span class="token function">GET_FORMAT</span><span class="token punctuation">(</span><span class="token datatype">DATE</span><span class="token punctuation">,</span><span class="token string">'USA'</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token string">'2003-10-31'</span></code></pre>
</div>
</li>
<li class="listitem">
<a name="function_hour">
</a>
<p>
<a class="link" href="date-and-time-functions.html#function_hour">
<code class="literal">
HOUR(
<em class="replaceable">
<code>
time
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045204720416">
</a>
<p>
Returns the hour for
<em class="replaceable">
<code>
time
</code>
</em>
. The
range of the return value is
<code class="literal">
0
</code>
to
<code class="literal">
23
</code>
for time-of-day values. However, the
range of
<a class="link" href="time.html" title="13.2.3 The TIME Type">
<code class="literal">
TIME
</code>
</a>
values actually
is much larger, so
<code class="literal">
HOUR
</code>
can return values
greater than
<code class="literal">
23
</code>
. Returns
<code class="literal">
NULL
</code>
if
<em class="replaceable">
<code>
time
</code>
</em>
is
<code class="literal">
NULL
</code>
.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa79792162"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">HOUR</span><span class="token punctuation">(</span><span class="token string">'10:05:03'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token number">10</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">HOUR</span><span class="token punctuation">(</span><span class="token string">'272:59:59'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token number">272</span></code></pre>
</div>
</li>
<li class="listitem">
<a name="function_last-day">
</a>
<p>
<a class="link" href="date-and-time-functions.html#function_last-day">
<code class="literal">
LAST_DAY(
<em class="replaceable">
<code>
date
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045204703056">
</a>
<p>
Takes a date or datetime value and returns the corresponding
value for the last day of the month. Returns
<code class="literal">
NULL
</code>
if the argument is invalid or
<code class="literal">
NULL
</code>
.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa83855621"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">LAST_DAY</span><span class="token punctuation">(</span><span class="token string">'2003-02-05'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token string">'2003-02-28'</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">LAST_DAY</span><span class="token punctuation">(</span><span class="token string">'2004-02-05'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token string">'2004-02-29'</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">LAST_DAY</span><span class="token punctuation">(</span><span class="token string">'2004-01-01 01:01:01'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token string">'2004-01-31'</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">LAST_DAY</span><span class="token punctuation">(</span><span class="token string">'2003-03-32'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token boolean">NULL</span></code></pre>
</div>
</li>
<li class="listitem">
<a name="function_localtime">
</a>
<p>
<a class="link" href="date-and-time-functions.html#function_localtime">
<code class="literal">
LOCALTIME
</code>
</a>
,
<a class="link" href="date-and-time-functions.html#function_localtime">
<code class="literal">
LOCALTIME([
<em class="replaceable">
<code>
fsp
</code>
</em>
])
</code>
</a>
</p>
<a class="indexterm" name="idm46045204687744">
</a>
<p>
<a class="link" href="date-and-time-functions.html#function_localtime">
<code class="literal">
LOCALTIME
</code>
</a>
and
<a class="link" href="date-and-time-functions.html#function_localtime">
<code class="literal">
LOCALTIME()
</code>
</a>
are synonyms for
<a class="link" href="date-and-time-functions.html#function_now">
<code class="literal">
NOW()
</code>
</a>
.
</p>
</li>
<li class="listitem">
<a name="function_localtimestamp">
</a>
<p>
<a class="link" href="date-and-time-functions.html#function_localtimestamp">
<code class="literal">
LOCALTIMESTAMP
</code>
</a>
,
<a class="link" href="date-and-time-functions.html#function_localtimestamp">
<code class="literal">
LOCALTIMESTAMP([
<em class="replaceable">
<code>
fsp
</code>
</em>
])
</code>
</a>
</p>
<a class="indexterm" name="idm46045204674944">
</a>
<p>
<a class="link" href="date-and-time-functions.html#function_localtimestamp">
<code class="literal">
LOCALTIMESTAMP
</code>
</a>
and
<a class="link" href="date-and-time-functions.html#function_localtimestamp">
<code class="literal">
LOCALTIMESTAMP()
</code>
</a>
are synonyms
for
<a class="link" href="date-and-time-functions.html#function_now">
<code class="literal">
NOW()
</code>
</a>
.
</p>
</li>
<li class="listitem">
<a name="function_makedate">
</a>
<p>
<a class="link" href="date-and-time-functions.html#function_makedate">
<code class="literal">
MAKEDATE(
<em class="replaceable">
<code>
year
</code>
</em>
,
<em class="replaceable">
<code>
dayofyear
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045204662928">
</a>
<p>
Returns a date, given year and day-of-year values.
<em class="replaceable">
<code>
dayofyear
</code>
</em>
must be greater than 0 or
the result is
<code class="literal">
NULL
</code>
. The result is also
<code class="literal">
NULL
</code>
if either argument is
<code class="literal">
NULL
</code>
.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa65075204"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">MAKEDATE</span><span class="token punctuation">(</span><span class="token number">2011</span><span class="token punctuation">,</span><span class="token number">31</span><span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token function">MAKEDATE</span><span class="token punctuation">(</span><span class="token number">2011</span><span class="token punctuation">,</span><span class="token number">32</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token string">'2011-01-31'</span><span class="token punctuation">,</span> <span class="token string">'2011-02-01'</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">MAKEDATE</span><span class="token punctuation">(</span><span class="token number">2011</span><span class="token punctuation">,</span><span class="token number">365</span><span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token function">MAKEDATE</span><span class="token punctuation">(</span><span class="token number">2014</span><span class="token punctuation">,</span><span class="token number">365</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token string">'2011-12-31'</span><span class="token punctuation">,</span> <span class="token string">'2014-12-31'</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">MAKEDATE</span><span class="token punctuation">(</span><span class="token number">2011</span><span class="token punctuation">,</span><span class="token number">0</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token boolean">NULL</span></code></pre>
</div>
</li>
<li class="listitem">
<a name="function_maketime">
</a>
<p>
<a class="link" href="date-and-time-functions.html#function_maketime">
<code class="literal">
MAKETIME(
<em class="replaceable">
<code>
hour
</code>
</em>
,
<em class="replaceable">
<code>
minute
</code>
</em>
,
<em class="replaceable">
<code>
second
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045204647552">
</a>
<p>
Returns a time value calculated from the
<em class="replaceable">
<code>
hour
</code>
</em>
,
<em class="replaceable">
<code>
minute
</code>
</em>
, and
<em class="replaceable">
<code>
second
</code>
</em>
arguments. Returns
<code class="literal">
NULL
</code>
if any of its arguments are
<code class="literal">
NULL
</code>
.
</p>
<p>
The
<em class="replaceable">
<code>
second
</code>
</em>
argument can have a
fractional part.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa90957137"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">MAKETIME</span><span class="token punctuation">(</span><span class="token number">12</span><span class="token punctuation">,</span><span class="token number">15</span><span class="token punctuation">,</span><span class="token number">30</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token string">'12:15:30'</span></code></pre>
</div>
</li>
<li class="listitem">
<a name="function_microsecond">
</a>
<p>
<a class="link" href="date-and-time-functions.html#function_microsecond">
<code class="literal">
MICROSECOND(
<em class="replaceable">
<code>
expr
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045204633664">
</a>
<p>
Returns the microseconds from the time or datetime expression
<em class="replaceable">
<code>
expr
</code>
</em>
as a number in the range from
<code class="literal">
0
</code>
to
<code class="literal">
999999
</code>
. Returns
<code class="literal">
NULL
</code>
if
<em class="replaceable">
<code>
expr
</code>
</em>
is
<code class="literal">
NULL
</code>
.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa37178863"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">MICROSECOND</span><span class="token punctuation">(</span><span class="token string">'12:00:00.123456'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token number">123456</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">MICROSECOND</span><span class="token punctuation">(</span><span class="token string">'2019-12-31 23:59:59.000010'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token number">10</span></code></pre>
</div>
</li>
<li class="listitem">
<a name="function_minute">
</a>
<p>
<a class="link" href="date-and-time-functions.html#function_minute">
<code class="literal">
MINUTE(
<em class="replaceable">
<code>
time
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045204618896">
</a>
<p>
Returns the minute for
<em class="replaceable">
<code>
time
</code>
</em>
, in the
range
<code class="literal">
0
</code>
to
<code class="literal">
59
</code>
, or
<code class="literal">
NULL
</code>
if
<em class="replaceable">
<code>
time
</code>
</em>
is
<code class="literal">
NULL
</code>
.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa45938871"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">MINUTE</span><span class="token punctuation">(</span><span class="token string">'2008-02-03 10:05:03'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token number">5</span></code></pre>
</div>
</li>
<li class="listitem">
<a name="function_month">
</a>
<p>
<a class="link" href="date-and-time-functions.html#function_month">
<code class="literal">
MONTH(
<em class="replaceable">
<code>
date
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045204605040">
</a>
<p>
Returns the month for
<em class="replaceable">
<code>
date
</code>
</em>
, in the
range
<code class="literal">
1
</code>
to
<code class="literal">
12
</code>
for
January to December, or
<code class="literal">
0
</code>
for dates such as
<code class="literal">
'0000-00-00'
</code>
or
<code class="literal">
'2008-00-00'
</code>
that have a zero month part.
Returns
<code class="literal">
NULL
</code>
if
<em class="replaceable">
<code>
date
</code>
</em>
is
<code class="literal">
NULL
</code>
.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa70880862"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">MONTH</span><span class="token punctuation">(</span><span class="token string">'2008-02-03'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token number">2</span></code></pre>
</div>
</li>
<li class="listitem">
<a name="function_monthname">
</a>
<p>
<a class="link" href="date-and-time-functions.html#function_monthname">
<code class="literal">
MONTHNAME(
<em class="replaceable">
<code>
date
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045204588992">
</a>
<p>
Returns the full name of the month for
<em class="replaceable">
<code>
date
</code>
</em>
. The language used for the
name is controlled by the value of the
<a class="link" href="server-system-variables.html#sysvar_lc_time_names">
<code class="literal">
lc_time_names
</code>
</a>
system variable
(
<a class="xref" href="locale-support.html" title="12.16 MySQL Server Locale Support">
Section 12.16, “MySQL Server Locale Support”
</a>
). Returns
<code class="literal">
NULL
</code>
if
<em class="replaceable">
<code>
date
</code>
</em>
is
<code class="literal">
NULL
</code>
.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa46704182"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">MONTHNAME</span><span class="token punctuation">(</span><span class="token string">'2008-02-03'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token string">'February'</span></code></pre>
</div>
</li>
<li class="listitem">
<a name="function_now">
</a>
<p>
<a class="link" href="date-and-time-functions.html#function_now">
<code class="literal">
NOW([
<em class="replaceable">
<code>
fsp
</code>
</em>
])
</code>
</a>
</p>
<a class="indexterm" name="idm46045204574592">
</a>
<p>
Returns the current date and time as a value in
<code class="literal">
'
<em class="replaceable">
<code>
YYYY-MM-DD
hh:mm:ss
</code>
</em>
'
</code>
or
<em class="replaceable">
<code>
YYYYMMDDhhmmss
</code>
</em>
format, depending on
whether the function is used in string or numeric context. The
value is expressed in the session time zone.
</p>
<p>
If the
<em class="replaceable">
<code>
fsp
</code>
</em>
argument is given to
specify a fractional seconds precision from 0 to 6, the return
value includes a fractional seconds part of that many digits.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa44409057"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">NOW</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token string">'2007-12-15 23:50:26'</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">NOW</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token operator">+</span> <span class="token number">0</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token number">20071215235026.000000</span></code></pre>
</div>
<p>
<a class="link" href="date-and-time-functions.html#function_now">
<code class="literal">
NOW()
</code>
</a>
returns a constant time
that indicates the time at which the statement began to
execute. (Within a stored function or trigger,
<a class="link" href="date-and-time-functions.html#function_now">
<code class="literal">
NOW()
</code>
</a>
returns the time at which
the function or triggering statement began to execute.) This
differs from the behavior for
<a class="link" href="date-and-time-functions.html#function_sysdate">
<code class="literal">
SYSDATE()
</code>
</a>
, which returns the
exact time at which it executes.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa62500855"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">NOW</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token function">SLEEP</span><span class="token punctuation">(</span><span class="token number">2</span><span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token function">NOW</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> NOW() <span class="token punctuation">|</span> SLEEP(2) <span class="token punctuation">|</span> NOW() <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 2006<span class="token punctuation">-</span>04<span class="token punctuation">-</span>12 13:47:36 <span class="token punctuation">|</span> 0 <span class="token punctuation">|</span> 2006<span class="token punctuation">-</span>04<span class="token punctuation">-</span>12 13:47:36 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">SYSDATE</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token function">SLEEP</span><span class="token punctuation">(</span><span class="token number">2</span><span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token function">SYSDATE</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> SYSDATE() <span class="token punctuation">|</span> SLEEP(2) <span class="token punctuation">|</span> SYSDATE() <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 2006<span class="token punctuation">-</span>04<span class="token punctuation">-</span>12 13:47:44 <span class="token punctuation">|</span> 0 <span class="token punctuation">|</span> 2006<span class="token punctuation">-</span>04<span class="token punctuation">-</span>12 13:47:46 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
</div>
<p>
In addition, the
<code class="literal">
SET TIMESTAMP
</code>
statement
affects the value returned by
<a class="link" href="date-and-time-functions.html#function_now">
<code class="literal">
NOW()
</code>
</a>
but not by
<a class="link" href="date-and-time-functions.html#function_sysdate">
<code class="literal">
SYSDATE()
</code>
</a>
. This means that
timestamp settings in the binary log have no effect on
invocations of
<a class="link" href="date-and-time-functions.html#function_sysdate">
<code class="literal">
SYSDATE()
</code>
</a>
.
Setting the timestamp to a nonzero value causes each
subsequent invocation of
<a class="link" href="date-and-time-functions.html#function_now">
<code class="literal">
NOW()
</code>
</a>
to return that value. Setting the timestamp to zero cancels
this effect so that
<a class="link" href="date-and-time-functions.html#function_now">
<code class="literal">
NOW()
</code>
</a>
once
again returns the current date and time.
</p>
<p>
See the description for
<a class="link" href="date-and-time-functions.html#function_sysdate">
<code class="literal">
SYSDATE()
</code>
</a>
for additional
information about the differences between the two functions.
</p>
</li>
<li class="listitem">
<a name="function_period-add">
</a>
<p>
<a class="link" href="date-and-time-functions.html#function_period-add">
<code class="literal">
PERIOD_ADD(
<em class="replaceable">
<code>
P
</code>
</em>
,
<em class="replaceable">
<code>
N
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045204543440">
</a>
<p>
Adds
<em class="replaceable">
<code>
N
</code>
</em>
months to period
<em class="replaceable">
<code>
P
</code>
</em>
(in the format
<em class="replaceable">
<code>
YYMM
</code>
</em>
or
<em class="replaceable">
<code>
YYYYMM
</code>
</em>
). Returns a value in the
format
<em class="replaceable">
<code>
YYYYMM
</code>
</em>
.
</p>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
The period argument
<em class="replaceable">
<code>
P
</code>
</em>
is
<span class="emphasis">
<em>
not
</em>
</span>
a date value.
</p>
</div>
<p>
This function returns
<code class="literal">
NULL
</code>
if
<em class="replaceable">
<code>
P
</code>
</em>
or
<em class="replaceable">
<code>
N
</code>
</em>
is
<code class="literal">
NULL
</code>
.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa92951194"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">PERIOD_ADD</span><span class="token punctuation">(</span><span class="token number">200801</span><span class="token punctuation">,</span><span class="token number">2</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token number">200803</span></code></pre>
</div>
</li>
<li class="listitem">
<a name="function_period-diff">
</a>
<p>
<a class="link" href="date-and-time-functions.html#function_period-diff">
<code class="literal">
PERIOD_DIFF(
<em class="replaceable">
<code>
P1
</code>
</em>
,
<em class="replaceable">
<code>
P2
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045204526320">
</a>
<p>
Returns the number of months between periods
<em class="replaceable">
<code>
P1
</code>
</em>
and
<em class="replaceable">
<code>
P2
</code>
</em>
.
<em class="replaceable">
<code>
P1
</code>
</em>
and
<em class="replaceable">
<code>
P2
</code>
</em>
should be in the format
<em class="replaceable">
<code>
YYMM
</code>
</em>
or
<em class="replaceable">
<code>
YYYYMM
</code>
</em>
. Note that the period
arguments
<em class="replaceable">
<code>
P1
</code>
</em>
and
<em class="replaceable">
<code>
P2
</code>
</em>
are
<span class="emphasis">
<em>
not
</em>
</span>
date values.
</p>
<p>
This function returns
<code class="literal">
NULL
</code>
if
<em class="replaceable">
<code>
P1
</code>
</em>
or
<em class="replaceable">
<code>
P2
</code>
</em>
is
<code class="literal">
NULL
</code>
.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa61866747"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">PERIOD_DIFF</span><span class="token punctuation">(</span><span class="token number">200802</span><span class="token punctuation">,</span><span class="token number">200703</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token number">11</span></code></pre>
</div>
</li>
<li class="listitem">
<a name="function_quarter">
</a>
<p>
<a class="link" href="date-and-time-functions.html#function_quarter">
<code class="literal">
QUARTER(
<em class="replaceable">
<code>
date
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045204509680">
</a>
<p>
Returns the quarter of the year for
<em class="replaceable">
<code>
date
</code>
</em>
, in the range
<code class="literal">
1
</code>
to
<code class="literal">
4
</code>
, or
<code class="literal">
NULL
</code>
if
<em class="replaceable">
<code>
date
</code>
</em>
is
<code class="literal">
NULL
</code>
.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa51633752"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">QUARTER</span><span class="token punctuation">(</span><span class="token string">'2008-04-01'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token number">2</span></code></pre>
</div>
</li>
<li class="listitem">
<a name="function_second">
</a>
<p>
<a class="link" href="date-and-time-functions.html#function_second">
<code class="literal">
SECOND(
<em class="replaceable">
<code>
time
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045204495792">
</a>
<p>
Returns the second for
<em class="replaceable">
<code>
time
</code>
</em>
, in the
range
<code class="literal">
0
</code>
to
<code class="literal">
59
</code>
, or
<code class="literal">
NULL
</code>
if
<em class="replaceable">
<code>
time
</code>
</em>
is
<code class="literal">
NULL
</code>
.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa66612467"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">SECOND</span><span class="token punctuation">(</span><span class="token string">'10:05:03'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token number">3</span></code></pre>
</div>
</li>
<li class="listitem">
<a name="function_sec-to-time">
</a>
<p>
<a class="link" href="date-and-time-functions.html#function_sec-to-time">
<code class="literal">
SEC_TO_TIME(
<em class="replaceable">
<code>
seconds
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045204481936">
</a>
<p>
Returns the
<em class="replaceable">
<code>
seconds
</code>
</em>
argument,
converted to hours, minutes, and seconds, as a
<a class="link" href="time.html" title="13.2.3 The TIME Type">
<code class="literal">
TIME
</code>
</a>
value. The range of the
result is constrained to that of the
<a class="link" href="time.html" title="13.2.3 The TIME Type">
<code class="literal">
TIME
</code>
</a>
data type. A warning
occurs if the argument corresponds to a value outside that
range.
</p>
<p>
The function returns
<code class="literal">
NULL
</code>
if
<em class="replaceable">
<code>
seconds
</code>
</em>
is
<code class="literal">
NULL
</code>
.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa41130380"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">SEC_TO_TIME</span><span class="token punctuation">(</span><span class="token number">2378</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token string">'00:39:38'</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">SEC_TO_TIME</span><span class="token punctuation">(</span><span class="token number">2378</span><span class="token punctuation">)</span> <span class="token operator">+</span> <span class="token number">0</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token number">3938</span></code></pre>
</div>
</li>
<li class="listitem">
<a name="function_str-to-date">
</a>
<p>
<a class="link" href="date-and-time-functions.html#function_str-to-date">
<code class="literal">
STR_TO_DATE(
<em class="replaceable">
<code>
str
</code>
</em>
,
<em class="replaceable">
<code>
format
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045204465248">
</a>
<p>
This is the inverse of the
<a class="link" href="date-and-time-functions.html#function_date-format">
<code class="literal">
DATE_FORMAT()
</code>
</a>
function. It
takes a string
<em class="replaceable">
<code>
str
</code>
</em>
and a format
string
<em class="replaceable">
<code>
format
</code>
</em>
.
<code class="literal">
STR_TO_DATE()
</code>
returns a
<a class="link" href="datetime.html" title="13.2.2 The DATE, DATETIME, and TIMESTAMP Types">
<code class="literal">
DATETIME
</code>
</a>
value if the format
string contains both date and time parts, or a
<a class="link" href="datetime.html" title="13.2.2 The DATE, DATETIME, and TIMESTAMP Types">
<code class="literal">
DATE
</code>
</a>
or
<a class="link" href="time.html" title="13.2.3 The TIME Type">
<code class="literal">
TIME
</code>
</a>
value if the string
contains only date or time parts. If
<em class="replaceable">
<code>
str
</code>
</em>
or
<em class="replaceable">
<code>
format
</code>
</em>
is
<code class="literal">
NULL
</code>
,
the function returns
<code class="literal">
NULL
</code>
. If the date,
time, or datetime value extracted from
<em class="replaceable">
<code>
str
</code>
</em>
cannot be parsed according to
the rules followed by the server,
<code class="literal">
STR_TO_DATE()
</code>
returns
<code class="literal">
NULL
</code>
and produces a warning.
</p>
<p>
The server scans
<em class="replaceable">
<code>
str
</code>
</em>
attempting to
match
<em class="replaceable">
<code>
format
</code>
</em>
to it. The format
string can contain literal characters and format specifiers
beginning with
<code class="literal">
%
</code>
. Literal characters in
<em class="replaceable">
<code>
format
</code>
</em>
must match literally in
<em class="replaceable">
<code>
str
</code>
</em>
. Format specifiers in
<em class="replaceable">
<code>
format
</code>
</em>
must match a date or time
part in
<em class="replaceable">
<code>
str
</code>
</em>
. For the specifiers
that can be used in
<em class="replaceable">
<code>
format
</code>
</em>
, see the
<a class="link" href="date-and-time-functions.html#function_date-format">
<code class="literal">
DATE_FORMAT()
</code>
</a>
function
description.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa42898187"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">STR_TO_DATE</span><span class="token punctuation">(</span><span class="token string">'01,5,2013'</span><span class="token punctuation">,</span><span class="token string">'%d,%m,%Y'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token string">'2013-05-01'</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">STR_TO_DATE</span><span class="token punctuation">(</span><span class="token string">'May 1, 2013'</span><span class="token punctuation">,</span><span class="token string">'%M %d,%Y'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token string">'2013-05-01'</span></code></pre>
</div>
<p>
Scanning starts at the beginning of
<em class="replaceable">
<code>
str
</code>
</em>
and fails if
<em class="replaceable">
<code>
format
</code>
</em>
is found not to match. Extra
characters at the end of
<em class="replaceable">
<code>
str
</code>
</em>
are
ignored.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa45783478"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">STR_TO_DATE</span><span class="token punctuation">(</span><span class="token string">'a09:30:17'</span><span class="token punctuation">,</span><span class="token string">'a%h:%i:%s'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token string">'09:30:17'</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">STR_TO_DATE</span><span class="token punctuation">(</span><span class="token string">'a09:30:17'</span><span class="token punctuation">,</span><span class="token string">'%h:%i:%s'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token boolean">NULL</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">STR_TO_DATE</span><span class="token punctuation">(</span><span class="token string">'09:30:17a'</span><span class="token punctuation">,</span><span class="token string">'%h:%i:%s'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token string">'09:30:17'</span></code></pre>
</div>
<p>
Unspecified date or time parts have a value of 0, so
incompletely specified values in
<em class="replaceable">
<code>
str
</code>
</em>
produce a result with some or
all parts set to 0:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa47575252"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">STR_TO_DATE</span><span class="token punctuation">(</span><span class="token string">'abc'</span><span class="token punctuation">,</span><span class="token string">'abc'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token string">'0000-00-00'</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">STR_TO_DATE</span><span class="token punctuation">(</span><span class="token string">'9'</span><span class="token punctuation">,</span><span class="token string">'%m'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token string">'0000-09-00'</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">STR_TO_DATE</span><span class="token punctuation">(</span><span class="token string">'9'</span><span class="token punctuation">,</span><span class="token string">'%s'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token string">'00:00:09'</span></code></pre>
</div>
<p>
Range checking on the parts of date values is as described in
<a class="xref" href="datetime.html" title="13.2.2 The DATE, DATETIME, and TIMESTAMP Types">
Section 13.2.2, “The DATE, DATETIME, and TIMESTAMP Types”
</a>
. This means, for example, that
<span class="quote">
“
<span class="quote">
zero
</span>
”
</span>
dates or dates with part values of 0 are
permitted unless the SQL mode is set to disallow such values.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa68994674"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">STR_TO_DATE</span><span class="token punctuation">(</span><span class="token string">'00/00/0000'</span><span class="token punctuation">,</span> <span class="token string">'%m/%d/%Y'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token string">'0000-00-00'</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">STR_TO_DATE</span><span class="token punctuation">(</span><span class="token string">'04/31/2004'</span><span class="token punctuation">,</span> <span class="token string">'%m/%d/%Y'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token string">'2004-04-31'</span></code></pre>
</div>
<p>
If the
<a class="link" href="sql-mode.html#sqlmode_no_zero_date">
<code class="literal">
NO_ZERO_DATE
</code>
</a>
SQL mode
is enabled, zero dates are disallowed. In that case,
<a class="link" href="date-and-time-functions.html#function_str-to-date">
<code class="literal">
STR_TO_DATE()
</code>
</a>
returns
<code class="literal">
NULL
</code>
and generates a warning:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa68043559"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SET</span> sql_mode <span class="token operator">=</span> <span class="token string">''</span><span class="token punctuation">;</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">STR_TO_DATE</span><span class="token punctuation">(</span><span class="token string">'00/00/0000'</span><span class="token punctuation">,</span> <span class="token string">'%m/%d/%Y'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> STR_TO_DATE('00/00/0000', '%m/%d/%Y') <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 0000<span class="token punctuation">-</span>00<span class="token punctuation">-</span>00 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token prompt">mysql></span> <span class="token keyword">SET</span> sql_mode <span class="token operator">=</span> <span class="token string">'NO_ZERO_DATE'</span><span class="token punctuation">;</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">STR_TO_DATE</span><span class="token punctuation">(</span><span class="token string">'00/00/0000'</span><span class="token punctuation">,</span> <span class="token string">'%m/%d/%Y'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> STR_TO_DATE('00/00/0000', '%m/%d/%Y') <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> NULL <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token prompt">mysql></span> <span class="token keyword">SHOW</span> <span class="token keyword">WARNINGS</span>\G
<span class="token output"><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span> 1. row <span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span>
Level<span class="token punctuation">:</span> Warning
Code<span class="token punctuation">:</span> 1411
Message<span class="token punctuation">:</span> Incorrect datetime value<span class="token punctuation">:</span> '00/00/0000' for function str_to_date</span></code></pre>
</div>
<p>
In some previous versions of MySQL, it was possible to pass an
invalid date string such as
<code class="literal">
'2021-11-31'
</code>
to
this function. In MySQL 8.4,
<code class="literal">
STR_TO_DATE()
</code>
performs complete range
checking and raises an error if the date after conversion
would be invalid.
</p>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
You cannot use format
<code class="literal">
"%X%V"
</code>
to convert a
year-week string to a date because the combination of a year
and week does not uniquely identify a year and month if the
week crosses a month boundary. To convert a year-week to a
date, you should also specify the weekday:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa84337674"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">STR_TO_DATE</span><span class="token punctuation">(</span><span class="token string">'200442 Monday'</span><span class="token punctuation">,</span> <span class="token string">'%X%V %W'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token string">'2004-10-18'</span></code></pre>
</div>
</div>
<p>
You should also be aware that, for dates and the date portions
of datetime values,
<code class="literal">
STR_TO_DATE()
</code>
checks
(only) the individual year, month, and day of month values for
validity. More precisely, this means that the year is checked
to be sure that it is in the range 0-9999 inclusive, the month
is checked to ensure that it is in the range 1-12 inclusive,
and the day of month is checked to make sure that it is in the
range 1-31 inclusive, but the server does not check the values
in combination. For example,
<code class="literal">
SELECT
STR_TO_DATE('23-2-31', '%Y-%m-%d')
</code>
returns
<code class="literal">
2023-02-31
</code>
. Enabling or disabling the
<a class="link" href="sql-mode.html#sqlmode_allow_invalid_dates">
<code class="literal">
ALLOW_INVALID_DATES
</code>
</a>
server
SQL mode has no effect on this behavior. See
<a class="xref" href="datetime.html" title="13.2.2 The DATE, DATETIME, and TIMESTAMP Types">
Section 13.2.2, “The DATE, DATETIME, and TIMESTAMP Types”
</a>
, for more information.
</p>
</li>
<li class="listitem">
<a name="function_subdate">
</a>
<p>
<a class="link" href="date-and-time-functions.html#function_subdate">
<code class="literal">
SUBDATE(
<em class="replaceable">
<code>
date
</code>
</em>
,INTERVAL
<em class="replaceable">
<code>
expr
</code>
</em>
<em class="replaceable">
<code>
unit
</code>
</em>
)
</code>
</a>
,
<a class="link" href="date-and-time-functions.html#function_subdate">
<code class="literal">
SUBDATE(
<em class="replaceable">
<code>
expr
</code>
</em>
,
<em class="replaceable">
<code>
days
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045204401376">
</a>
<p>
When invoked with the
<code class="literal">
INTERVAL
</code>
form of the
second argument,
<a class="link" href="date-and-time-functions.html#function_subdate">
<code class="literal">
SUBDATE()
</code>
</a>
is a
synonym for
<a class="link" href="date-and-time-functions.html#function_date-sub">
<code class="literal">
DATE_SUB()
</code>
</a>
. For
information on the
<code class="literal">
INTERVAL
</code>
<em class="replaceable">
<code>
unit
</code>
</em>
argument, see the discussion
for
<a class="link" href="date-and-time-functions.html#function_date-add">
<code class="literal">
DATE_ADD()
</code>
</a>
.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa17055766"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">DATE_SUB</span><span class="token punctuation">(</span><span class="token string">'2008-01-02'</span><span class="token punctuation">,</span> <span class="token keyword">INTERVAL</span> <span class="token number">31</span> <span class="token keyword">DAY</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token string">'2007-12-02'</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">SUBDATE</span><span class="token punctuation">(</span><span class="token string">'2008-01-02'</span><span class="token punctuation">,</span> <span class="token keyword">INTERVAL</span> <span class="token number">31</span> <span class="token keyword">DAY</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token string">'2007-12-02'</span></code></pre>
</div>
<p>
The second form enables the use of an integer value for
<em class="replaceable">
<code>
days
</code>
</em>
. In such cases, it is
interpreted as the number of days to be subtracted from the
date or datetime expression
<em class="replaceable">
<code>
expr
</code>
</em>
.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa56991475"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">SUBDATE</span><span class="token punctuation">(</span><span class="token string">'2008-01-02 12:00:00'</span><span class="token punctuation">,</span> <span class="token number">31</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token string">'2007-12-02 12:00:00'</span></code></pre>
</div>
<p>
This function returns
<code class="literal">
NULL
</code>
if any of its
arguments are
<code class="literal">
NULL
</code>
.
</p>
</li>
<li class="listitem">
<a name="function_subtime">
</a>
<p>
<a class="link" href="date-and-time-functions.html#function_subtime">
<code class="literal">
SUBTIME(
<em class="replaceable">
<code>
expr1
</code>
</em>
,
<em class="replaceable">
<code>
expr2
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045204379680">
</a>
<p>
<a class="link" href="date-and-time-functions.html#function_subtime">
<code class="literal">
SUBTIME()
</code>
</a>
returns
<em class="replaceable">
<code>
expr1
</code>
</em>
−
<em class="replaceable">
<code>
expr2
</code>
</em>
expressed as a value in the
same format as
<em class="replaceable">
<code>
expr1
</code>
</em>
.
<em class="replaceable">
<code>
expr1
</code>
</em>
is a time or datetime
expression, and
<em class="replaceable">
<code>
expr2
</code>
</em>
is a time
expression.
</p>
<p>
Resolution of this function's return type is performed as
it is for the
<a class="link" href="date-and-time-functions.html#function_addtime">
<code class="literal">
ADDTIME()
</code>
</a>
function; see the description of that function for more
information.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa13194378"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">SUBTIME</span><span class="token punctuation">(</span><span class="token string">'2007-12-31 23:59:59.999999'</span><span class="token punctuation">,</span><span class="token string">'1 1:1:1.000002'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token string">'2007-12-30 22:58:58.999997'</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">SUBTIME</span><span class="token punctuation">(</span><span class="token string">'01:00:00.999999'</span><span class="token punctuation">,</span> <span class="token string">'02:00:00.999998'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token string">'-00:59:59.999999'</span></code></pre>
</div>
<p>
This function returns
<code class="literal">
NULL
</code>
if
<em class="replaceable">
<code>
expr1
</code>
</em>
or
<em class="replaceable">
<code>
expr2
</code>
</em>
is
<code class="literal">
NULL
</code>
.
</p>
</li>
<li class="listitem">
<a name="function_sysdate">
</a>
<p>
<a class="link" href="date-and-time-functions.html#function_sysdate">
<code class="literal">
SYSDATE([
<em class="replaceable">
<code>
fsp
</code>
</em>
])
</code>
</a>
</p>
<a class="indexterm" name="idm46045204360528">
</a>
<p>
Returns the current date and time as a value in
<code class="literal">
'
<em class="replaceable">
<code>
YYYY-MM-DD
hh:mm:ss
</code>
</em>
'
</code>
or
<em class="replaceable">
<code>
YYYYMMDDhhmmss
</code>
</em>
format, depending on
whether the function is used in string or numeric context.
</p>
<p>
If the
<em class="replaceable">
<code>
fsp
</code>
</em>
argument is given to
specify a fractional seconds precision from 0 to 6, the return
value includes a fractional seconds part of that many digits.
</p>
<p>
<a class="link" href="date-and-time-functions.html#function_sysdate">
<code class="literal">
SYSDATE()
</code>
</a>
returns the time at
which it executes. This differs from the behavior for
<a class="link" href="date-and-time-functions.html#function_now">
<code class="literal">
NOW()
</code>
</a>
, which returns a constant
time that indicates the time at which the statement began to
execute. (Within a stored function or trigger,
<a class="link" href="date-and-time-functions.html#function_now">
<code class="literal">
NOW()
</code>
</a>
returns the time at which
the function or triggering statement began to execute.)
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa19015521"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">NOW</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token function">SLEEP</span><span class="token punctuation">(</span><span class="token number">2</span><span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token function">NOW</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> NOW() <span class="token punctuation">|</span> SLEEP(2) <span class="token punctuation">|</span> NOW() <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 2006<span class="token punctuation">-</span>04<span class="token punctuation">-</span>12 13:47:36 <span class="token punctuation">|</span> 0 <span class="token punctuation">|</span> 2006<span class="token punctuation">-</span>04<span class="token punctuation">-</span>12 13:47:36 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">SYSDATE</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token function">SLEEP</span><span class="token punctuation">(</span><span class="token number">2</span><span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token function">SYSDATE</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> SYSDATE() <span class="token punctuation">|</span> SLEEP(2) <span class="token punctuation">|</span> SYSDATE() <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 2006<span class="token punctuation">-</span>04<span class="token punctuation">-</span>12 13:47:44 <span class="token punctuation">|</span> 0 <span class="token punctuation">|</span> 2006<span class="token punctuation">-</span>04<span class="token punctuation">-</span>12 13:47:46 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
</div>
<p>
In addition, the
<code class="literal">
SET TIMESTAMP
</code>
statement
affects the value returned by
<a class="link" href="date-and-time-functions.html#function_now">
<code class="literal">
NOW()
</code>
</a>
but not by
<a class="link" href="date-and-time-functions.html#function_sysdate">
<code class="literal">
SYSDATE()
</code>
</a>
. This means that
timestamp settings in the binary log have no effect on
invocations of
<a class="link" href="date-and-time-functions.html#function_sysdate">
<code class="literal">
SYSDATE()
</code>
</a>
.
</p>
<p>
Because
<a class="link" href="date-and-time-functions.html#function_sysdate">
<code class="literal">
SYSDATE()
</code>
</a>
can return
different values even within the same statement, and is not
affected by
<code class="literal">
SET TIMESTAMP
</code>
, it is
nondeterministic and therefore unsafe for replication if
statement-based binary logging is used. If that is a problem,
you can use row-based logging.
</p>
<p>
Alternatively, you can use the
<a class="link" href="server-options.html#option_mysqld_sysdate-is-now">
<code class="option">
--sysdate-is-now
</code>
</a>
option to
cause
<a class="link" href="date-and-time-functions.html#function_sysdate">
<code class="literal">
SYSDATE()
</code>
</a>
to be an alias
for
<a class="link" href="date-and-time-functions.html#function_now">
<code class="literal">
NOW()
</code>
</a>
. This works if the
option is used on both the replication source server and the
replica.
</p>
<p>
The nondeterministic nature of
<a class="link" href="date-and-time-functions.html#function_sysdate">
<code class="literal">
SYSDATE()
</code>
</a>
also means that
indexes cannot be used for evaluating expressions that refer
to it.
</p>
</li>
<li class="listitem">
<a name="function_time">
</a>
<p>
<a class="link" href="date-and-time-functions.html#function_time">
<code class="literal">
TIME(
<em class="replaceable">
<code>
expr
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045204328848">
</a>
<p>
Extracts the time part of the time or datetime expression
<em class="replaceable">
<code>
expr
</code>
</em>
and returns it as a string.
Returns
<code class="literal">
NULL
</code>
if
<em class="replaceable">
<code>
expr
</code>
</em>
is
<code class="literal">
NULL
</code>
.
</p>
<p>
This function is unsafe for statement-based replication. A
warning is logged if you use this function when
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_format">
<code class="literal">
binlog_format
</code>
</a>
is set to
<code class="literal">
STATEMENT
</code>
.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa92297113"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">TIME</span><span class="token punctuation">(</span><span class="token string">'2003-12-31 01:02:03'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token string">'01:02:03'</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">TIME</span><span class="token punctuation">(</span><span class="token string">'2003-12-31 01:02:03.000123'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token string">'01:02:03.000123'</span></code></pre>
</div>
</li>
<li class="listitem">
<a name="function_timediff">
</a>
<p>
<a class="link" href="date-and-time-functions.html#function_timediff">
<code class="literal">
TIMEDIFF(
<em class="replaceable">
<code>
expr1
</code>
</em>
,
<em class="replaceable">
<code>
expr2
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045204312512">
</a>
<p>
<a class="link" href="date-and-time-functions.html#function_timediff">
<code class="literal">
TIMEDIFF()
</code>
</a>
returns
<em class="replaceable">
<code>
expr1
</code>
</em>
−
<em class="replaceable">
<code>
expr2
</code>
</em>
expressed as a time value.
<em class="replaceable">
<code>
expr1
</code>
</em>
and
<em class="replaceable">
<code>
expr2
</code>
</em>
are strings which are
converted to
<code class="literal">
TIME
</code>
or
<code class="literal">
DATETIME
</code>
expressions; these must be of the
same type following conversion. Returns
<code class="literal">
NULL
</code>
if
<em class="replaceable">
<code>
expr1
</code>
</em>
or
<em class="replaceable">
<code>
expr2
</code>
</em>
is
<code class="literal">
NULL
</code>
.
</p>
<p>
The result returned by
<code class="literal">
TIMEDIFF()
</code>
is
limited to the range allowed for
<a class="link" href="time.html" title="13.2.3 The TIME Type">
<code class="literal">
TIME
</code>
</a>
values. Alternatively, you
can use either of the functions
<a class="link" href="date-and-time-functions.html#function_timestampdiff">
<code class="literal">
TIMESTAMPDIFF()
</code>
</a>
and
<a class="link" href="date-and-time-functions.html#function_unix-timestamp">
<code class="literal">
UNIX_TIMESTAMP()
</code>
</a>
, both of which
return integers.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa53272657"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">TIMEDIFF</span><span class="token punctuation">(</span><span class="token string">'2000-01-01 00:00:00'</span><span class="token punctuation">,</span>
<span class="token prompt"> -></span> <span class="token string">'2000-01-01 00:00:00.000001'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token string">'-00:00:00.000001'</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">TIMEDIFF</span><span class="token punctuation">(</span><span class="token string">'2008-12-31 23:59:59.000001'</span><span class="token punctuation">,</span>
<span class="token prompt"> -></span> <span class="token string">'2008-12-30 01:01:01.000002'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token string">'46:58:57.999999'</span></code></pre>
</div>
</li>
<li class="listitem">
<a name="function_timestamp">
</a>
<p>
<a class="link" href="date-and-time-functions.html#function_timestamp">
<code class="literal">
TIMESTAMP(
<em class="replaceable">
<code>
expr
</code>
</em>
)
</code>
</a>
,
<a class="link" href="date-and-time-functions.html#function_timestamp">
<code class="literal">
TIMESTAMP(
<em class="replaceable">
<code>
expr1
</code>
</em>
,
<em class="replaceable">
<code>
expr2
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045204286000">
</a>
<p>
With a single argument, this function returns the date or
datetime expression
<em class="replaceable">
<code>
expr
</code>
</em>
as a
datetime value. With two arguments, it adds the time
expression
<em class="replaceable">
<code>
expr2
</code>
</em>
to the date or
datetime expression
<em class="replaceable">
<code>
expr1
</code>
</em>
and
returns the result as a datetime value. Returns
<code class="literal">
NULL
</code>
if
<em class="replaceable">
<code>
expr
</code>
</em>
,
<em class="replaceable">
<code>
expr1
</code>
</em>
, or
<em class="replaceable">
<code>
expr2
</code>
</em>
is
<code class="literal">
NULL
</code>
.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa45212270"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">TIMESTAMP</span><span class="token punctuation">(</span><span class="token string">'2003-12-31'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token string">'2003-12-31 00:00:00'</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">TIMESTAMP</span><span class="token punctuation">(</span><span class="token string">'2003-12-31 12:00:00'</span><span class="token punctuation">,</span><span class="token string">'12:00:00'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token string">'2004-01-01 00:00:00'</span></code></pre>
</div>
</li>
<li class="listitem">
<a name="function_timestampadd">
</a>
<p>
<a class="link" href="date-and-time-functions.html#function_timestampadd">
<code class="literal">
TIMESTAMPADD(
<em class="replaceable">
<code>
unit
</code>
</em>
,
<em class="replaceable">
<code>
interval
</code>
</em>
,
<em class="replaceable">
<code>
datetime_expr
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045204269760">
</a>
<p>
Adds the integer expression
<em class="replaceable">
<code>
interval
</code>
</em>
to the date or datetime
expression
<em class="replaceable">
<code>
datetime_expr
</code>
</em>
. The unit
for
<em class="replaceable">
<code>
interval
</code>
</em>
is given by the
<em class="replaceable">
<code>
unit
</code>
</em>
argument, which should be one
of the following values:
<code class="literal">
MICROSECOND
</code>
(microseconds),
<code class="literal">
SECOND
</code>
,
<code class="literal">
MINUTE
</code>
,
<code class="literal">
HOUR
</code>
,
<code class="literal">
DAY
</code>
,
<code class="literal">
WEEK
</code>
,
<code class="literal">
MONTH
</code>
,
<code class="literal">
QUARTER
</code>
, or
<code class="literal">
YEAR
</code>
.
</p>
<p>
The
<em class="replaceable">
<code>
unit
</code>
</em>
value may be specified
using one of keywords as shown, or with a prefix of
<code class="literal">
SQL_TSI_
</code>
. For example,
<code class="literal">
DAY
</code>
and
<code class="literal">
SQL_TSI_DAY
</code>
both
are legal.
</p>
<p>
This function returns
<code class="literal">
NULL
</code>
if
<em class="replaceable">
<code>
interval
</code>
</em>
or
<em class="replaceable">
<code>
datetime_expr
</code>
</em>
is
<code class="literal">
NULL
</code>
.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa36184224"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">TIMESTAMPADD</span><span class="token punctuation">(</span><span class="token keyword">MINUTE</span><span class="token punctuation">,</span> <span class="token number">1</span><span class="token punctuation">,</span> <span class="token string">'2003-01-02'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token string">'2003-01-02 00:01:00'</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">TIMESTAMPADD</span><span class="token punctuation">(</span><span class="token keyword">WEEK</span><span class="token punctuation">,</span><span class="token number">1</span><span class="token punctuation">,</span><span class="token string">'2003-01-02'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token string">'2003-01-09'</span></code></pre>
</div>
<p>
When adding a
<code class="literal">
MONTH
</code>
interval to a
<code class="literal">
DATE
</code>
or
<code class="literal">
DATETIME
</code>
value,
and the resulting date includes a day that does not exist in
the given month, the day is adjusted to the last day of the
month, as shown here:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa87426126"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">TIMESTAMPADD</span><span class="token punctuation">(</span><span class="token keyword">MONTH</span><span class="token punctuation">,</span> <span class="token number">1</span><span class="token punctuation">,</span> <span class="token datatype">DATE</span> <span class="token string">'2024-03-30'</span><span class="token punctuation">)</span> <span class="token keyword">AS</span> t1<span class="token punctuation">,</span>
<span class="token operator">></span> <span class="token function">TIMESTAMPADD</span><span class="token punctuation">(</span><span class="token keyword">MONTH</span><span class="token punctuation">,</span> <span class="token number">1</span><span class="token punctuation">,</span> <span class="token datatype">DATE</span> <span class="token string">'2024-03-31'</span><span class="token punctuation">)</span> <span class="token keyword">AS</span> t2<span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> t1 <span class="token punctuation">|</span> t2 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 2024<span class="token punctuation">-</span>04<span class="token punctuation">-</span>30 <span class="token punctuation">|</span> 2024<span class="token punctuation">-</span>04<span class="token punctuation">-</span>30 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output">1 row in set (0.00 sec)</span></code></pre>
</div>
</li>
<li class="listitem">
<a name="function_timestampdiff">
</a>
<p>
<a class="link" href="date-and-time-functions.html#function_timestampdiff">
<code class="literal">
TIMESTAMPDIFF(
<em class="replaceable">
<code>
unit
</code>
</em>
,
<em class="replaceable">
<code>
datetime_expr1
</code>
</em>
,
<em class="replaceable">
<code>
datetime_expr2
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045204238368">
</a>
<p>
Returns
<em class="replaceable">
<code>
datetime_expr2
</code>
</em>
−
<em class="replaceable">
<code>
datetime_expr1
</code>
</em>
, where
<em class="replaceable">
<code>
datetime_expr1
</code>
</em>
and
<em class="replaceable">
<code>
datetime_expr2
</code>
</em>
are date or datetime
expressions. One expression may be a date and the other a
datetime; a date value is treated as a datetime having the
time part
<code class="literal">
'00:00:00'
</code>
where necessary. The
unit for the result (an integer) is given by the
<em class="replaceable">
<code>
unit
</code>
</em>
argument. The legal values for
<em class="replaceable">
<code>
unit
</code>
</em>
are the same as those listed
in the description of the
<a class="link" href="date-and-time-functions.html#function_timestampadd">
<code class="literal">
TIMESTAMPADD()
</code>
</a>
function.
</p>
<p>
This function returns
<code class="literal">
NULL
</code>
if
<em class="replaceable">
<code>
datetime_expr1
</code>
</em>
or
<em class="replaceable">
<code>
datetime_expr2
</code>
</em>
is
<code class="literal">
NULL
</code>
.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa15878912"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">TIMESTAMPDIFF</span><span class="token punctuation">(</span><span class="token keyword">MONTH</span><span class="token punctuation">,</span><span class="token string">'2003-02-01'</span><span class="token punctuation">,</span><span class="token string">'2003-05-01'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token number">3</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">TIMESTAMPDIFF</span><span class="token punctuation">(</span><span class="token datatype">YEAR</span><span class="token punctuation">,</span><span class="token string">'2002-05-01'</span><span class="token punctuation">,</span><span class="token string">'2001-01-01'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token operator">-</span><span class="token number">1</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">TIMESTAMPDIFF</span><span class="token punctuation">(</span><span class="token keyword">MINUTE</span><span class="token punctuation">,</span><span class="token string">'2003-02-01'</span><span class="token punctuation">,</span><span class="token string">'2003-05-01 12:05:55'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token number">128885</span></code></pre>
</div>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
The order of the date or datetime arguments for this
function is the opposite of that used with the
<a class="link" href="date-and-time-functions.html#function_timestamp">
<code class="literal">
TIMESTAMP()
</code>
</a>
function when
invoked with 2 arguments.
</p>
</div>
</li>
<li class="listitem">
<a name="function_time-format">
</a>
<p>
<a class="link" href="date-and-time-functions.html#function_time-format">
<code class="literal">
TIME_FORMAT(
<em class="replaceable">
<code>
time
</code>
</em>
,
<em class="replaceable">
<code>
format
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045204216336">
</a>
<p>
This is used like the
<a class="link" href="date-and-time-functions.html#function_date-format">
<code class="literal">
DATE_FORMAT()
</code>
</a>
function, but the
<em class="replaceable">
<code>
format
</code>
</em>
string may contain format
specifiers only for hours, minutes, seconds, and microseconds.
Other specifiers produce a
<code class="literal">
NULL
</code>
or
<code class="literal">
0
</code>
.
<code class="literal">
TIME_FORMAT()
</code>
returns
<code class="literal">
NULL
</code>
if
<em class="replaceable">
<code>
time
</code>
</em>
or
<em class="replaceable">
<code>
format
</code>
</em>
is
<code class="literal">
NULL
</code>
.
</p>
<p>
If the
<em class="replaceable">
<code>
time
</code>
</em>
value contains an hour
part that is greater than
<code class="literal">
23
</code>
, the
<code class="literal">
%H
</code>
and
<code class="literal">
%k
</code>
hour format
specifiers produce a value larger than the usual range of
<code class="literal">
0..23
</code>
. The other hour format specifiers
produce the hour value modulo 12.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa67819064"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">TIME_FORMAT</span><span class="token punctuation">(</span><span class="token string">'100:00:00'</span><span class="token punctuation">,</span> <span class="token string">'%H %k %h %I %l'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token string">'100 100 04 04 4'</span></code></pre>
</div>
</li>
<li class="listitem">
<a name="function_time-to-sec">
</a>
<p>
<a class="link" href="date-and-time-functions.html#function_time-to-sec">
<code class="literal">
TIME_TO_SEC(
<em class="replaceable">
<code>
time
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045204196016">
</a>
<p>
Returns the
<em class="replaceable">
<code>
time
</code>
</em>
argument,
converted to seconds. Returns
<code class="literal">
NULL
</code>
if
<em class="replaceable">
<code>
time
</code>
</em>
is
<code class="literal">
NULL
</code>
.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa22372863"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">TIME_TO_SEC</span><span class="token punctuation">(</span><span class="token string">'22:23:00'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token number">80580</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">TIME_TO_SEC</span><span class="token punctuation">(</span><span class="token string">'00:39:38'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token number">2378</span></code></pre>
</div>
</li>
<li class="listitem">
<a name="function_to-days">
</a>
<p>
<a class="link" href="date-and-time-functions.html#function_to-days">
<code class="literal">
TO_DAYS(
<em class="replaceable">
<code>
date
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045204182768">
</a>
<p>
Given a date
<em class="replaceable">
<code>
date
</code>
</em>
, returns a day
number (the number of days since year 0). Returns
<code class="literal">
NULL
</code>
if
<em class="replaceable">
<code>
date
</code>
</em>
is
<code class="literal">
NULL
</code>
.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa16561339"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">TO_DAYS</span><span class="token punctuation">(</span><span class="token number">950501</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token number">728779</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">TO_DAYS</span><span class="token punctuation">(</span><span class="token string">'2007-10-07'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token number">733321</span></code></pre>
</div>
<p>
<a class="link" href="date-and-time-functions.html#function_to-days">
<code class="literal">
TO_DAYS()
</code>
</a>
is not intended for
use with values that precede the advent of the Gregorian
calendar (1582), because it does not take into account the
days that were lost when the calendar was changed. For dates
before 1582 (and possibly a later year in other locales),
results from this function are not reliable. See
<a class="xref" href="mysql-calendar.html" title="13.2.7 What Calendar Is Used By MySQL?">
Section 13.2.7, “What Calendar Is Used By MySQL?”
</a>
, for details.
</p>
<p>
Remember that MySQL converts two-digit year values in dates to
four-digit form using the rules in
<a class="xref" href="date-and-time-types.html" title="13.2 Date and Time Data Types">
Section 13.2, “Date and Time Data Types”
</a>
. For example,
<code class="literal">
'2008-10-07'
</code>
and
<code class="literal">
'08-10-07'
</code>
are seen as identical dates:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa28663557"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">TO_DAYS</span><span class="token punctuation">(</span><span class="token string">'2008-10-07'</span><span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token function">TO_DAYS</span><span class="token punctuation">(</span><span class="token string">'08-10-07'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token number">733687</span><span class="token punctuation">,</span> <span class="token number">733687</span></code></pre>
</div>
<p>
In MySQL, the zero date is defined as
<code class="literal">
'0000-00-00'
</code>
, even though this date is
itself considered invalid. This means that, for
<code class="literal">
'0000-00-00'
</code>
and
<code class="literal">
'0000-01-01'
</code>
,
<a class="link" href="date-and-time-functions.html#function_to-days">
<code class="literal">
TO_DAYS()
</code>
</a>
returns the values
shown here:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa72755812"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">TO_DAYS</span><span class="token punctuation">(</span><span class="token string">'0000-00-00'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> to_days('0000<span class="token punctuation">-</span>00<span class="token punctuation">-</span>00') <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> NULL <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output">1 row in set, 1 warning (0.00 sec)</span>
<span class="token prompt">mysql></span> <span class="token keyword">SHOW</span> <span class="token keyword">WARNINGS</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> Level <span class="token punctuation">|</span> Code <span class="token punctuation">|</span> Message <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> Warning <span class="token punctuation">|</span> 1292 <span class="token punctuation">|</span> Incorrect datetime value: '0000<span class="token punctuation">-</span>00<span class="token punctuation">-</span>00' <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output">1 row in set (0.00 sec)</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">TO_DAYS</span><span class="token punctuation">(</span><span class="token string">'0000-01-01'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> to_days('0000<span class="token punctuation">-</span>01<span class="token punctuation">-</span>01') <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 1 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output">1 row in set (0.00 sec)</span></code></pre>
</div>
<p>
This is true whether or not the
<a class="link" href="sql-mode.html#sqlmode_allow_invalid_dates">
<code class="literal">
ALLOW_INVALID_DATES
</code>
</a>
SQL
server mode is enabled.
</p>
</li>
<li class="listitem">
<a name="function_to-seconds">
</a>
<p>
<a class="link" href="date-and-time-functions.html#function_to-seconds">
<code class="literal">
TO_SECONDS(
<em class="replaceable">
<code>
expr
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045204152432">
</a>
<p>
Given a date or datetime
<em class="replaceable">
<code>
expr
</code>
</em>
,
returns the number of seconds since the year 0. If
<em class="replaceable">
<code>
expr
</code>
</em>
is not a valid date or
datetime value (including
<code class="literal">
NULL
</code>
), it returns
<code class="literal">
NULL
</code>
.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa23540102"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">TO_SECONDS</span><span class="token punctuation">(</span><span class="token number">950501</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token number">62966505600</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">TO_SECONDS</span><span class="token punctuation">(</span><span class="token string">'2009-11-29'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token number">63426672000</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">TO_SECONDS</span><span class="token punctuation">(</span><span class="token string">'2009-11-29 13:43:32'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token number">63426721412</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">TO_SECONDS</span><span class="token punctuation">(</span> <span class="token function">NOW</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token number">63426721458</span></code></pre>
</div>
<p>
Like
<a class="link" href="date-and-time-functions.html#function_to-days">
<code class="literal">
TO_DAYS()
</code>
</a>
,
<code class="literal">
TO_SECONDS()
</code>
is not intended for use with
values that precede the advent of the Gregorian calendar
(1582), because it does not take into account the days that
were lost when the calendar was changed. For dates before 1582
(and possibly a later year in other locales), results from
this function are not reliable. See
<a class="xref" href="mysql-calendar.html" title="13.2.7 What Calendar Is Used By MySQL?">
Section 13.2.7, “What Calendar Is Used By MySQL?”
</a>
, for details.
</p>
<p>
Like
<a class="link" href="date-and-time-functions.html#function_to-days">
<code class="literal">
TO_DAYS()
</code>
</a>
,
<code class="literal">
TO_SECONDS()
</code>
, converts two-digit year
values in dates to four-digit form using the rules in
<a class="xref" href="date-and-time-types.html" title="13.2 Date and Time Data Types">
Section 13.2, “Date and Time Data Types”
</a>
.
</p>
<p>
In MySQL, the zero date is defined as
<code class="literal">
'0000-00-00'
</code>
, even though this date is
itself considered invalid. This means that, for
<code class="literal">
'0000-00-00'
</code>
and
<code class="literal">
'0000-01-01'
</code>
,
<a class="link" href="date-and-time-functions.html#function_to-seconds">
<code class="literal">
TO_SECONDS()
</code>
</a>
returns the values
shown here:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa90581470"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">TO_SECONDS</span><span class="token punctuation">(</span><span class="token string">'0000-00-00'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> TO_SECONDS('0000<span class="token punctuation">-</span>00<span class="token punctuation">-</span>00') <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> NULL <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output">1 row in set, 1 warning (0.00 sec)</span>
<span class="token prompt">mysql></span> <span class="token keyword">SHOW</span> <span class="token keyword">WARNINGS</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> Level <span class="token punctuation">|</span> Code <span class="token punctuation">|</span> Message <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> Warning <span class="token punctuation">|</span> 1292 <span class="token punctuation">|</span> Incorrect datetime value: '0000<span class="token punctuation">-</span>00<span class="token punctuation">-</span>00' <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output">1 row in set (0.00 sec)</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">TO_SECONDS</span><span class="token punctuation">(</span><span class="token string">'0000-01-01'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> TO_SECONDS('0000<span class="token punctuation">-</span>01<span class="token punctuation">-</span>01') <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 86400 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output">1 row in set (0.00 sec)</span></code></pre>
</div>
<p>
This is true whether or not the
<a class="link" href="sql-mode.html#sqlmode_allow_invalid_dates">
<code class="literal">
ALLOW_INVALID_DATES
</code>
</a>
SQL
server mode is enabled.
</p>
</li>
<li class="listitem">
<a name="function_unix-timestamp">
</a>
<p>
<a class="link" href="date-and-time-functions.html#function_unix-timestamp">
<code class="literal">
UNIX_TIMESTAMP([
<em class="replaceable">
<code>
date
</code>
</em>
])
</code>
</a>
</p>
<a class="indexterm" name="idm46045204120832">
</a>
<p>
If
<a class="link" href="date-and-time-functions.html#function_unix-timestamp">
<code class="literal">
UNIX_TIMESTAMP()
</code>
</a>
is called
with no
<em class="replaceable">
<code>
date
</code>
</em>
argument, it returns a
Unix timestamp representing seconds since
<code class="literal">
'1970-01-01
00:00:00'
</code>
UTC.
</p>
<p>
If
<a class="link" href="date-and-time-functions.html#function_unix-timestamp">
<code class="literal">
UNIX_TIMESTAMP()
</code>
</a>
is called
with a
<em class="replaceable">
<code>
date
</code>
</em>
argument, it returns
the value of the argument as seconds since
<code class="literal">
'1970-01-01 00:00:00'
</code>
UTC. The server
interprets
<em class="replaceable">
<code>
date
</code>
</em>
as a value in the
session time zone and converts it to an internal Unix
timestamp value in UTC. (Clients can set the session time zone
as described in
<a class="xref" href="time-zone-support.html" title="7.1.15 MySQL Server Time Zone Support">
Section 7.1.15, “MySQL Server Time Zone Support”
</a>
.) The
<em class="replaceable">
<code>
date
</code>
</em>
argument may be a
<a class="link" href="datetime.html" title="13.2.2 The DATE, DATETIME, and TIMESTAMP Types">
<code class="literal">
DATE
</code>
</a>
,
<a class="link" href="datetime.html" title="13.2.2 The DATE, DATETIME, and TIMESTAMP Types">
<code class="literal">
DATETIME
</code>
</a>
, or
<a class="link" href="datetime.html" title="13.2.2 The DATE, DATETIME, and TIMESTAMP Types">
<code class="literal">
TIMESTAMP
</code>
</a>
string, or a number
in
<em class="replaceable">
<code>
YYMMDD
</code>
</em>
,
<em class="replaceable">
<code>
YYMMDDhhmmss
</code>
</em>
,
<em class="replaceable">
<code>
YYYYMMDD
</code>
</em>
, or
<em class="replaceable">
<code>
YYYYMMDDhhmmss
</code>
</em>
format. If the
argument includes a time part, it may optionally include a
fractional seconds part.
</p>
<p>
The return value is an integer if no argument is given or the
argument does not include a fractional seconds part, or
<a class="link" href="fixed-point-types.html" title="13.1.3 Fixed-Point Types (Exact Value) - DECIMAL, NUMERIC">
<code class="literal">
DECIMAL
</code>
</a>
if an argument is given
that includes a fractional seconds part.
</p>
<p>
When the
<em class="replaceable">
<code>
date
</code>
</em>
argument is a
<a class="link" href="datetime.html" title="13.2.2 The DATE, DATETIME, and TIMESTAMP Types">
<code class="literal">
TIMESTAMP
</code>
</a>
column,
<a class="link" href="date-and-time-functions.html#function_unix-timestamp">
<code class="literal">
UNIX_TIMESTAMP()
</code>
</a>
returns the
internal timestamp value directly, with no implicit
<span class="quote">
“
<span class="quote">
string-to-Unix-timestamp
</span>
”
</span>
conversion.
</p>
<p>
The valid range of argument values is the same as for the
<a class="link" href="datetime.html" title="13.2.2 The DATE, DATETIME, and TIMESTAMP Types">
<code class="literal">
TIMESTAMP
</code>
</a>
data type:
<code class="literal">
'1970-01-01 00:00:01.000000'
</code>
UTC to
<code class="literal">
'2038-01-19 03:14:07.999999'
</code>
UTC for 32-bit
platforms; for MySQL running on 64-bit platforms, the valid
range of argument values for
<code class="literal">
UNIX_TIMESTAMP()
</code>
is
<code class="literal">
'1970-01-01
00:00:01.000000'
</code>
UTC to
<code class="literal">
'3001-01-19
03:14:07.999999'
</code>
UTC (corresponding to
32536771199.999999 seconds).
</p>
<p>
Regardless of MySQL version or platform architecture, if you
pass an out-of-range date to
<a class="link" href="date-and-time-functions.html#function_unix-timestamp">
<code class="literal">
UNIX_TIMESTAMP()
</code>
</a>
, it returns
<code class="literal">
0
</code>
. If
<em class="replaceable">
<code>
date
</code>
</em>
is
<code class="literal">
NULL
</code>
, it returns
<code class="literal">
NULL
</code>
.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa94937673"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">UNIX_TIMESTAMP</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token number">1447431666</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">UNIX_TIMESTAMP</span><span class="token punctuation">(</span><span class="token string">'2015-11-13 10:20:19'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token number">1447431619</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">UNIX_TIMESTAMP</span><span class="token punctuation">(</span><span class="token string">'2015-11-13 10:20:19.012'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token number">1447431619.012</span></code></pre>
</div>
<a class="indexterm" name="idm46045204085520">
</a>
<p>
If you use
<a class="link" href="date-and-time-functions.html#function_unix-timestamp">
<code class="literal">
UNIX_TIMESTAMP()
</code>
</a>
and
<a class="link" href="date-and-time-functions.html#function_from-unixtime">
<code class="literal">
FROM_UNIXTIME()
</code>
</a>
to convert
between values in a non-UTC time zone and Unix timestamp
values, the conversion is lossy because the mapping is not
one-to-one in both directions. For example, due to conventions
for local time zone changes such as Daylight Saving Time
(DST), it is possible for
<a class="link" href="date-and-time-functions.html#function_unix-timestamp">
<code class="literal">
UNIX_TIMESTAMP()
</code>
</a>
to map two
values that are distinct in a non-UTC time zone to the same
Unix timestamp value.
<a class="link" href="date-and-time-functions.html#function_from-unixtime">
<code class="literal">
FROM_UNIXTIME()
</code>
</a>
maps that value
back to only one of the original values. Here is an example,
using values that are distinct in the
<code class="literal">
MET
</code>
time zone:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa2565946"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SET</span> time_zone <span class="token operator">=</span> <span class="token string">'MET'</span><span class="token punctuation">;</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">UNIX_TIMESTAMP</span><span class="token punctuation">(</span><span class="token string">'2005-03-27 03:00:00'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> UNIX_TIMESTAMP('2005<span class="token punctuation">-</span>03<span class="token punctuation">-</span>27 03:00:00') <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 1111885200 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">UNIX_TIMESTAMP</span><span class="token punctuation">(</span><span class="token string">'2005-03-27 02:00:00'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> UNIX_TIMESTAMP('2005<span class="token punctuation">-</span>03<span class="token punctuation">-</span>27 02:00:00') <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 1111885200 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">FROM_UNIXTIME</span><span class="token punctuation">(</span><span class="token number">1111885200</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> FROM_UNIXTIME(1111885200) <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 2005<span class="token punctuation">-</span>03<span class="token punctuation">-</span>27 03:00:00 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
</div>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
To use named time zones such as
<code class="literal">
'MET'
</code>
or
<code class="literal">
'Europe/Amsterdam'
</code>
, the time zone tables
must be properly set up. For instructions, see
<a class="xref" href="time-zone-support.html" title="7.1.15 MySQL Server Time Zone Support">
Section 7.1.15, “MySQL Server Time Zone Support”
</a>
.
</p>
</div>
<p>
If you want to subtract
<a class="link" href="date-and-time-functions.html#function_unix-timestamp">
<code class="literal">
UNIX_TIMESTAMP()
</code>
</a>
columns, you
might want to cast them to signed integers. See
<a class="xref" href="cast-functions.html" title="14.10 Cast Functions and Operators">
Section 14.10, “Cast Functions and Operators”
</a>
.
</p>
</li>
<li class="listitem">
<a name="function_utc-date">
</a>
<p>
<a class="link" href="date-and-time-functions.html#function_utc-date">
<code class="literal">
UTC_DATE
</code>
</a>
,
<a class="link" href="date-and-time-functions.html#function_utc-date">
<code class="literal">
UTC_DATE()
</code>
</a>
</p>
<a class="indexterm" name="idm46045204061840">
</a>
<p>
Returns the current UTC date as a value in
<code class="literal">
'
<em class="replaceable">
<code>
YYYY-MM-DD
</code>
</em>
'
</code>
or
<em class="replaceable">
<code>
YYYYMMDD
</code>
</em>
format, depending on
whether the function is used in string or numeric context.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa48893208"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">UTC_DATE</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token function">UTC_DATE</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token operator">+</span> <span class="token number">0</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token string">'2003-08-14'</span><span class="token punctuation">,</span> <span class="token number">20030814</span></code></pre>
</div>
</li>
<li class="listitem">
<a name="function_utc-time">
</a>
<p>
<a class="link" href="date-and-time-functions.html#function_utc-time">
<code class="literal">
UTC_TIME
</code>
</a>
,
<a class="link" href="date-and-time-functions.html#function_utc-time">
<code class="literal">
UTC_TIME([
<em class="replaceable">
<code>
fsp
</code>
</em>
])
</code>
</a>
</p>
<a class="indexterm" name="idm46045204048768">
</a>
<p>
Returns the current UTC time as a value in
<em class="replaceable">
<code>
'hh:mm:ss'
</code>
</em>
or
<em class="replaceable">
<code>
hhmmss
</code>
</em>
format, depending on whether
the function is used in string or numeric context.
</p>
<p>
If the
<em class="replaceable">
<code>
fsp
</code>
</em>
argument is given to
specify a fractional seconds precision from 0 to 6, the return
value includes a fractional seconds part of that many digits.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa19225327"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">UTC_TIME</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token function">UTC_TIME</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token operator">+</span> <span class="token number">0</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token string">'18:07:53'</span><span class="token punctuation">,</span> <span class="token number">180753.000000</span></code></pre>
</div>
</li>
<li class="listitem">
<a name="function_utc-timestamp">
</a>
<p>
<a class="link" href="date-and-time-functions.html#function_utc-timestamp">
<code class="literal">
UTC_TIMESTAMP
</code>
</a>
,
<a class="link" href="date-and-time-functions.html#function_utc-timestamp">
<code class="literal">
UTC_TIMESTAMP([
<em class="replaceable">
<code>
fsp
</code>
</em>
])
</code>
</a>
</p>
<a class="indexterm" name="idm46045204035360">
</a>
<p>
Returns the current UTC date and time as a value in
<code class="literal">
'
<em class="replaceable">
<code>
YYYY-MM-DD
hh:mm:ss
</code>
</em>
'
</code>
or
<em class="replaceable">
<code>
YYYYMMDDhhmmss
</code>
</em>
format, depending on
whether the function is used in string or numeric context.
</p>
<p>
If the
<em class="replaceable">
<code>
fsp
</code>
</em>
argument is given to
specify a fractional seconds precision from 0 to 6, the return
value includes a fractional seconds part of that many digits.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa58416067"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">UTC_TIMESTAMP</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token function">UTC_TIMESTAMP</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token operator">+</span> <span class="token number">0</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token string">'2003-08-14 18:08:04'</span><span class="token punctuation">,</span> <span class="token number">20030814180804.000000</span></code></pre>
</div>
</li>
<li class="listitem">
<a name="function_week">
</a>
<p>
<a class="link" href="date-and-time-functions.html#function_week">
<code class="literal">
WEEK(
<em class="replaceable">
<code>
date
</code>
</em>
[,
<em class="replaceable">
<code>
mode
</code>
</em>
])
</code>
</a>
</p>
<a class="indexterm" name="idm46045204021984">
</a>
<p>
This function returns the week number for
<em class="replaceable">
<code>
date
</code>
</em>
. The two-argument form of
<a class="link" href="date-and-time-functions.html#function_week">
<code class="literal">
WEEK()
</code>
</a>
enables you to specify
whether the week starts on Sunday or Monday and whether the
return value should be in the range from
<code class="literal">
0
</code>
to
<code class="literal">
53
</code>
or from
<code class="literal">
1
</code>
to
<code class="literal">
53
</code>
. If the
<em class="replaceable">
<code>
mode
</code>
</em>
argument is omitted, the value of the
<a class="link" href="server-system-variables.html#sysvar_default_week_format">
<code class="literal">
default_week_format
</code>
</a>
system
variable is used. See
<a class="xref" href="server-system-variables.html" title="7.1.8 Server System Variables">
Section 7.1.8, “Server System Variables”
</a>
. For a
<code class="literal">
NULL
</code>
date value, the function returns
<code class="literal">
NULL
</code>
.
</p>
<p>
The following table describes how the
<em class="replaceable">
<code>
mode
</code>
</em>
argument works.
</p>
<div class="informaltable">
<table summary="Now the mode argument of the WEEK function works. For each mode value, the table lists the first day of the week, the range, and a description of week 1.">
<colgroup>
<col style="width: 10%"/>
<col style="width: 20%"/>
<col style="width: 20%"/>
<col style="width: 50%"/>
</colgroup>
<thead>
<tr>
<th scope="col">
Mode
</th>
<th scope="col">
First day of week
</th>
<th scope="col">
Range
</th>
<th scope="col">
Week 1 is the first week …
</th>
</tr>
</thead>
<tbody>
<tr>
<th scope="row">
0
</th>
<td>
Sunday
</td>
<td>
0-53
</td>
<td>
with a Sunday in this year
</td>
</tr>
<tr>
<th scope="row">
1
</th>
<td>
Monday
</td>
<td>
0-53
</td>
<td>
with 4 or more days this year
</td>
</tr>
<tr>
<th scope="row">
2
</th>
<td>
Sunday
</td>
<td>
1-53
</td>
<td>
with a Sunday in this year
</td>
</tr>
<tr>
<th scope="row">
3
</th>
<td>
Monday
</td>
<td>
1-53
</td>
<td>
with 4 or more days this year
</td>
</tr>
<tr>
<th scope="row">
4
</th>
<td>
Sunday
</td>
<td>
0-53
</td>
<td>
with 4 or more days this year
</td>
</tr>
<tr>
<th scope="row">
5
</th>
<td>
Monday
</td>
<td>
0-53
</td>
<td>
with a Monday in this year
</td>
</tr>
<tr>
<th scope="row">
6
</th>
<td>
Sunday
</td>
<td>
1-53
</td>
<td>
with 4 or more days this year
</td>
</tr>
<tr>
<th scope="row">
7
</th>
<td>
Monday
</td>
<td>
1-53
</td>
<td>
with a Monday in this year
</td>
</tr>
</tbody>
</table>
</div>
<p>
For
<em class="replaceable">
<code>
mode
</code>
</em>
values with a meaning of
<span class="quote">
“
<span class="quote">
with 4 or more days this year,
</span>
”
</span>
weeks are
numbered according to ISO 8601:1988:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
If the week containing January 1 has 4 or more days in the
new year, it is week 1.
</p>
</li>
<li class="listitem">
<p>
Otherwise, it is the last week of the previous year, and
the next week is week 1.
</p>
</li>
</ul>
</div>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa33528828"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">WEEK</span><span class="token punctuation">(</span><span class="token string">'2008-02-20'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token number">7</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">WEEK</span><span class="token punctuation">(</span><span class="token string">'2008-02-20'</span><span class="token punctuation">,</span><span class="token number">0</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token number">7</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">WEEK</span><span class="token punctuation">(</span><span class="token string">'2008-02-20'</span><span class="token punctuation">,</span><span class="token number">1</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token number">8</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">WEEK</span><span class="token punctuation">(</span><span class="token string">'2008-12-31'</span><span class="token punctuation">,</span><span class="token number">1</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token number">53</span></code></pre>
</div>
<p>
If a date falls in the last week of the previous year, MySQL
returns
<code class="literal">
0
</code>
if you do not use
<code class="literal">
2
</code>
,
<code class="literal">
3
</code>
,
<code class="literal">
6
</code>
, or
<code class="literal">
7
</code>
as the optional
<em class="replaceable">
<code>
mode
</code>
</em>
argument:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa96160951"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">YEAR</span><span class="token punctuation">(</span><span class="token string">'2000-01-01'</span><span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token function">WEEK</span><span class="token punctuation">(</span><span class="token string">'2000-01-01'</span><span class="token punctuation">,</span><span class="token number">0</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token number">2000</span><span class="token punctuation">,</span> <span class="token number">0</span></code></pre>
</div>
<p>
One might argue that
<a class="link" href="date-and-time-functions.html#function_week">
<code class="literal">
WEEK()
</code>
</a>
should return
<code class="literal">
52
</code>
because the given date
actually occurs in the 52nd week of 1999.
<a class="link" href="date-and-time-functions.html#function_week">
<code class="literal">
WEEK()
</code>
</a>
returns
<code class="literal">
0
</code>
instead so that the return value is
<span class="quote">
“
<span class="quote">
the week number in the given year.
</span>
”
</span>
This makes
use of the
<a class="link" href="date-and-time-functions.html#function_week">
<code class="literal">
WEEK()
</code>
</a>
function
reliable when combined with other functions that extract a
date part from a date.
</p>
<p>
If you prefer a result evaluated with respect to the year that
contains the first day of the week for the given date, use
<code class="literal">
0
</code>
,
<code class="literal">
2
</code>
,
<code class="literal">
5
</code>
, or
<code class="literal">
7
</code>
as the optional
<em class="replaceable">
<code>
mode
</code>
</em>
argument.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa60907367"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">WEEK</span><span class="token punctuation">(</span><span class="token string">'2000-01-01'</span><span class="token punctuation">,</span><span class="token number">2</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token number">52</span></code></pre>
</div>
<p>
Alternatively, use the
<a class="link" href="date-and-time-functions.html#function_yearweek">
<code class="literal">
YEARWEEK()
</code>
</a>
function:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa35361472"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">YEARWEEK</span><span class="token punctuation">(</span><span class="token string">'2000-01-01'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token number">199952</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">MID</span><span class="token punctuation">(</span><span class="token function">YEARWEEK</span><span class="token punctuation">(</span><span class="token string">'2000-01-01'</span><span class="token punctuation">)</span><span class="token punctuation">,</span><span class="token number">5</span><span class="token punctuation">,</span><span class="token number">2</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token string">'52'</span></code></pre>
</div>
</li>
<li class="listitem">
<a name="function_weekday">
</a>
<p>
<a class="link" href="date-and-time-functions.html#function_weekday">
<code class="literal">
WEEKDAY(
<em class="replaceable">
<code>
date
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045203931616">
</a>
<p>
Returns the weekday index for
<em class="replaceable">
<code>
date
</code>
</em>
(
<code class="literal">
0
</code>
= Monday,
<code class="literal">
1
</code>
=
Tuesday, …
<code class="literal">
6
</code>
= Sunday). Returns
<code class="literal">
NULL
</code>
if
<em class="replaceable">
<code>
date
</code>
</em>
is
<code class="literal">
NULL
</code>
.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa60092287"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">WEEKDAY</span><span class="token punctuation">(</span><span class="token string">'2008-02-03 22:23:00'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token number">6</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">WEEKDAY</span><span class="token punctuation">(</span><span class="token string">'2007-11-06'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token number">1</span></code></pre>
</div>
</li>
<li class="listitem">
<a name="function_weekofyear">
</a>
<p>
<a class="link" href="date-and-time-functions.html#function_weekofyear">
<code class="literal">
WEEKOFYEAR(
<em class="replaceable">
<code>
date
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045203916288">
</a>
<p>
Returns the calendar week of the date as a number in the range
from
<code class="literal">
1
</code>
to
<code class="literal">
53
</code>
. Returns
<code class="literal">
NULL
</code>
if
<em class="replaceable">
<code>
date
</code>
</em>
is
<code class="literal">
NULL
</code>
.
</p>
<p>
<a class="link" href="date-and-time-functions.html#function_weekofyear">
<code class="literal">
WEEKOFYEAR()
</code>
</a>
is a compatibility
function that is equivalent to
<a class="link" href="date-and-time-functions.html#function_week">
<code class="literal">
WEEK(
<em class="replaceable">
<code>
date
</code>
</em>
,3)
</code>
</a>
.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa29872639"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">WEEKOFYEAR</span><span class="token punctuation">(</span><span class="token string">'2008-02-20'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token number">8</span></code></pre>
</div>
</li>
<li class="listitem">
<a name="function_year">
</a>
<p>
<a class="link" href="date-and-time-functions.html#function_year">
<code class="literal">
YEAR(
<em class="replaceable">
<code>
date
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045203899472">
</a>
<p>
Returns the year for
<em class="replaceable">
<code>
date
</code>
</em>
, in the
range
<code class="literal">
1000
</code>
to
<code class="literal">
9999
</code>
, or
<code class="literal">
0
</code>
for the
<span class="quote">
“
<span class="quote">
zero
</span>
”
</span>
date. Returns
<code class="literal">
NULL
</code>
if
<em class="replaceable">
<code>
date
</code>
</em>
is
<code class="literal">
NULL
</code>
.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa39209840"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">YEAR</span><span class="token punctuation">(</span><span class="token string">'1987-01-01'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token number">1987</span></code></pre>
</div>
</li>
<li class="listitem">
<a name="function_yearweek">
</a>
<p>
<a class="link" href="date-and-time-functions.html#function_yearweek">
<code class="literal">
YEARWEEK(
<em class="replaceable">
<code>
date
</code>
</em>
)
</code>
</a>
,
<a class="link" href="date-and-time-functions.html#function_yearweek">
<code class="literal">
YEARWEEK(
<em class="replaceable">
<code>
date
</code>
</em>
,
<em class="replaceable">
<code>
mode
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045203882336">
</a>
<p>
Returns year and week for a date. The year in the result may
be different from the year in the date argument for the first
and the last week of the year. Returns
<code class="literal">
NULL
</code>
if
<em class="replaceable">
<code>
date
</code>
</em>
is
<code class="literal">
NULL
</code>
.
</p>
<p>
The
<em class="replaceable">
<code>
mode
</code>
</em>
argument works exactly
like the
<em class="replaceable">
<code>
mode
</code>
</em>
argument to
<a class="link" href="date-and-time-functions.html#function_week">
<code class="literal">
WEEK()
</code>
</a>
. For the single-argument
syntax, a
<em class="replaceable">
<code>
mode
</code>
</em>
value of 0 is used.
Unlike
<a class="link" href="date-and-time-functions.html#function_week">
<code class="literal">
WEEK()
</code>
</a>
, the value of
<a class="link" href="server-system-variables.html#sysvar_default_week_format">
<code class="literal">
default_week_format
</code>
</a>
does not
influence
<a class="link" href="date-and-time-functions.html#function_yearweek">
<code class="literal">
YEARWEEK()
</code>
</a>
.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa81081390"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">YEARWEEK</span><span class="token punctuation">(</span><span class="token string">'1987-01-01'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token number">198652</span></code></pre>
</div>
<p>
The week number is different from what the
<a class="link" href="date-and-time-functions.html#function_week">
<code class="literal">
WEEK()
</code>
</a>
function would return
(
<code class="literal">
0
</code>
) for optional arguments
<code class="literal">
0
</code>
or
<code class="literal">
1
</code>
, as
<a class="link" href="date-and-time-functions.html#function_week">
<code class="literal">
WEEK()
</code>
</a>
then returns the week in
the context of the given year.
</p>
</li>
</ul>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/displaying-traces.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="displaying-traces">
</a>
10.15.13 Displaying Traces in Other Applications
</h3>
</div>
</div>
</div>
<p>
Examining a trace in the
<a class="link" href="mysql.html" title="6.5.1 mysql — The MySQL Command-Line Client">
<span class="command">
<strong>
mysql
</strong>
</span>
</a>
command-line
client can be made less difficult using the
<code class="literal">
pager
less
</code>
command (or your operating platform's
equivalent). An alternative can be to send the trace to a file,
similarly to what is shown here:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa71324758"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SELECT</span> TRACE <span class="token keyword">INTO</span> <span class="token keyword">DUMPFILE</span> <span class="token keyword"><em class="replaceable">file</em></span>
<span class="token keyword">FROM</span> INFORMATION_SCHEMA<span class="token punctuation">.</span>OPTIMIZER_TRACE<span class="token punctuation">;</span></code></pre>
</div>
<p>
You can then pass this file to a JSON-aware text editor or other
viewer, such as the
<a class="ulink" href="https://jsonview.com/" target="_blank">
JsonView
add-on for Firefox and Chrome
</a>
, which shows objects in
color and allows objects to be expanded or collapsed.
</p>
<p>
<code class="literal">
INTO DUMPFILE
</code>
is preferable to
<code class="literal">
INTO
OUTFILE
</code>
for this purpose, since the latter escapes
newlines. As noted previously, you should ensure that
<a class="link" href="server-system-variables.html#sysvar_end_markers_in_json">
<code class="literal">
end_markers_in_json
</code>
</a>
is
<code class="literal">
OFF
</code>
when executing the
<code class="literal">
SELECT
INTO
</code>
statement, so that the output is valid JSON.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/table-size-limit.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="table-size-limit">
</a>
10.4.6 Limits on Table Size
</h3>
</div>
</div>
</div>
<a class="indexterm" name="idm46045226460592">
</a>
<a class="indexterm" name="idm46045226459104">
</a>
<a class="indexterm" name="idm46045226457616">
</a>
<a class="indexterm" name="idm46045226456128">
</a>
<a class="indexterm" name="idm46045226455056">
</a>
<a class="indexterm" name="idm46045226453568">
</a>
<a class="indexterm" name="idm46045226452080">
</a>
<p>
The effective maximum table size for MySQL databases is usually
determined by operating system constraints on file sizes, not by
MySQL internal limits. For up-to-date information operating
system file size limits, refer to the documentation specific to
your operating system.
</p>
<p>
Windows users, please note that FAT and VFAT (FAT32) are
<span class="emphasis">
<em>
not
</em>
</span>
considered suitable for production use
with MySQL. Use NTFS instead.
</p>
<p>
If you encounter a full-table error, there are several reasons
why it might have occurred:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
The disk might be full.
</p>
</li>
<li class="listitem">
<p>
You are using
<code class="literal">
InnoDB
</code>
tables and have run
out of room in an
<code class="literal">
InnoDB
</code>
tablespace file.
The maximum tablespace size is also the maximum size for a
table. For tablespace size limits, see
<a class="xref" href="innodb-limits.html" title="17.21 InnoDB Limits">
Section 17.21, “InnoDB Limits”
</a>
.
</p>
<p>
Generally, partitioning of tables into multiple tablespace
files is recommended for tables larger than 1TB in size.
</p>
</li>
<li class="listitem">
<p>
You have hit an operating system file size limit. For
example, you are using
<code class="literal">
MyISAM
</code>
tables on
an operating system that supports files only up to 2GB in
size and you have hit this limit for the data file or index
file.
</p>
</li>
<li class="listitem">
<p>
You are using a
<code class="literal">
MyISAM
</code>
table and the
space required for the table exceeds what is permitted by
the internal pointer size.
<code class="literal">
MyISAM
</code>
permits
data and index files to grow up to 256TB by default, but
this limit can be changed up to the maximum permissible size
of 65,536TB (256
<sup>
7
</sup>
− 1
bytes).
</p>
<p>
If you need a
<code class="literal">
MyISAM
</code>
table that is larger
than the default limit and your operating system supports
large files, the
<a class="link" href="create-table.html" title="15.1.20 CREATE TABLE Statement">
<code class="literal">
CREATE TABLE
</code>
</a>
statement supports
<code class="literal">
AVG_ROW_LENGTH
</code>
and
<code class="literal">
MAX_ROWS
</code>
options. See
<a class="xref" href="create-table.html" title="15.1.20 CREATE TABLE Statement">
Section 15.1.20, “CREATE TABLE Statement”
</a>
. The server uses these
options to determine how large a table to permit.
</p>
<p>
If the pointer size is too small for an existing table, you
can change the options with
<a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement">
<code class="literal">
ALTER
TABLE
</code>
</a>
to increase a table's maximum
permissible size. See
<a class="xref" href="alter-table.html" title="15.1.9 ALTER TABLE Statement">
Section 15.1.9, “ALTER TABLE Statement”
</a>
.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa75659519"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">ALTER</span> <span class="token keyword">TABLE</span> <em class="replaceable">tbl_name</em> <span class="token keyword">MAX_ROWS</span><span class="token operator">=</span><span class="token number">1000000000</span> <span class="token keyword">AVG_ROW_LENGTH</span><span class="token operator">=</span><em class="replaceable">nnn</em><span class="token punctuation">;</span></code></pre>
</div>
<p>
You have to specify
<code class="literal">
AVG_ROW_LENGTH
</code>
only
for tables with
<a class="link" href="blob.html" title="13.3.4 The BLOB and TEXT Types">
<code class="literal">
BLOB
</code>
</a>
or
<a class="link" href="blob.html" title="13.3.4 The BLOB and TEXT Types">
<code class="literal">
TEXT
</code>
</a>
columns; in this case,
MySQL cannot optimize the space required based only on the
number of rows.
</p>
<p>
To change the default size limit for
<code class="literal">
MyISAM
</code>
tables, set the
<a class="link" href="server-system-variables.html#sysvar_myisam_data_pointer_size">
<code class="literal">
myisam_data_pointer_size
</code>
</a>
,
which sets the number of bytes used for internal row
pointers. The value is used to set the pointer size for new
tables if you do not specify the
<code class="literal">
MAX_ROWS
</code>
option. The value of
<a class="link" href="server-system-variables.html#sysvar_myisam_data_pointer_size">
<code class="literal">
myisam_data_pointer_size
</code>
</a>
can be from 2 to 7. For example, for tables that use the
dynamic storage format, a value of 4 permits tables up to
4GB; a value of 6 permits tables up to 256TB. Tables that
use the fixed storage format have a larger maximum data
length. For storage format characteristics, see
<a class="xref" href="myisam-table-formats.html" title="18.2.3 MyISAM Table Storage Formats">
Section 18.2.3, “MyISAM Table Storage Formats”
</a>
.
</p>
<p>
You can check the maximum data and index sizes by using this
statement:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa22105252"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SHOW</span> <span class="token keyword">TABLE</span> <span class="token keyword">STATUS</span> <span class="token keyword">FROM</span> <em class="replaceable">db_name</em> <span class="token operator">LIKE</span> <span class="token string">'<em class="replaceable">tbl_name</em>'</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
You also can use
<a class="link" href="myisamchk.html" title="6.6.4 myisamchk — MyISAM Table-Maintenance Utility">
<span class="command">
<strong>
myisamchk -dv
/path/to/table-index-file
</strong>
</span>
</a>
. See
<a class="xref" href="show.html" title="15.7.7 SHOW Statements">
Section 15.7.7, “SHOW Statements”
</a>
, or
<a class="xref" href="myisamchk.html" title="6.6.4 myisamchk — MyISAM Table-Maintenance Utility">
Section 6.6.4, “myisamchk — MyISAM Table-Maintenance Utility”
</a>
.
</p>
<p>
Other ways to work around file-size limits for
<code class="literal">
MyISAM
</code>
tables are as follows:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
If your large table is read only, you can use
<a class="link" href="myisampack.html" title="6.6.6 myisampack — Generate Compressed, Read-Only MyISAM Tables">
<span class="command">
<strong>
myisampack
</strong>
</span>
</a>
to compress it.
<a class="link" href="myisampack.html" title="6.6.6 myisampack — Generate Compressed, Read-Only MyISAM Tables">
<span class="command">
<strong>
myisampack
</strong>
</span>
</a>
usually compresses a table
by at least 50%, so you can have, in effect, much bigger
tables.
<a class="link" href="myisampack.html" title="6.6.6 myisampack — Generate Compressed, Read-Only MyISAM Tables">
<span class="command">
<strong>
myisampack
</strong>
</span>
</a>
also can merge
multiple tables into a single table. See
<a class="xref" href="myisampack.html" title="6.6.6 myisampack — Generate Compressed, Read-Only MyISAM Tables">
Section 6.6.6, “myisampack — Generate Compressed, Read-Only MyISAM Tables”
</a>
.
</p>
</li>
<li class="listitem">
<p>
MySQL includes a
<code class="literal">
MERGE
</code>
library that
enables you to handle a collection of
<code class="literal">
MyISAM
</code>
tables that have identical
structure as a single
<code class="literal">
MERGE
</code>
table.
See
<a class="xref" href="merge-storage-engine.html" title="18.7 The MERGE Storage Engine">
Section 18.7, “The MERGE Storage Engine”
</a>
.
</p>
</li>
</ul>
</div>
</li>
<li class="listitem">
<p>
You are using the
<code class="literal">
MEMORY
</code>
(
<code class="literal">
HEAP
</code>
) storage engine; in this case you
need to increase the value of the
<a class="link" href="server-system-variables.html#sysvar_max_heap_table_size">
<code class="literal">
max_heap_table_size
</code>
</a>
system
variable. See
<a class="xref" href="server-system-variables.html" title="7.1.8 Server System Variables">
Section 7.1.8, “Server System Variables”
</a>
.
</p>
</li>
</ul>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/spatial-relation-functions-object-shapes.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="spatial-relation-functions-object-shapes">
</a>
14.16.9.1 Spatial Relation Functions That Use Object Shapes
</h4>
</div>
</div>
</div>
<p>
The OpenGIS specification defines the following functions to
test the relationship between two geometry values
<em class="replaceable">
<code>
g1
</code>
</em>
and
<em class="replaceable">
<code>
g2
</code>
</em>
,
using precise object shapes. The return values 1 and 0 indicate
true and false, respectively, except that distance functions
return distance values.
</p>
<p>
Functions in this section detect arguments in either Cartesian
or geographic spatial reference systems (SRSs), and return
results appropriate to the SRS.
</p>
<p>
Unless otherwise specified, functions in this section handle
their geometry arguments as follows:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
If any argument is
<code class="literal">
NULL
</code>
or any geometry
argument is an empty geometry, the return value is
<code class="literal">
NULL
</code>
.
</p>
</li>
<li class="listitem">
<p>
If any geometry argument is not a syntactically well-formed
geometry, an
<a class="ulink" href="/doc/mysql-errors/8.4/en/server-error-reference.html#error_er_gis_invalid_data" target="_top">
<code class="literal">
ER_GIS_INVALID_DATA
</code>
</a>
error
occurs.
</p>
</li>
<li class="listitem">
<p>
If any geometry argument is a syntactically well-formed
geometry in an undefined spatial reference system (SRS), an
<a class="ulink" href="/doc/mysql-errors/8.4/en/server-error-reference.html#error_er_srs_not_found" target="_top">
<code class="literal">
ER_SRS_NOT_FOUND
</code>
</a>
error
occurs.
</p>
</li>
<li class="listitem">
<p>
For functions that take multiple geometry arguments, if
those arguments are not in the same SRS, an
<a class="ulink" href="/doc/mysql-errors/8.4/en/server-error-reference.html#error_er_gis_different_srids" target="_top">
<code class="literal">
ER_GIS_DIFFERENT_SRIDS
</code>
</a>
error
occurs.
</p>
</li>
<li class="listitem">
<p>
If any geometry argument is geometrically invalid, either
the result is true or false (it is undefined which), or an
error occurs.
</p>
</li>
<li class="listitem">
<p>
For geographic SRS geometry arguments, if any argument has a
longitude or latitude that is out of range, an error occurs:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
If a longitude value is not in the range (−180,
180], an
<a class="ulink" href="/doc/mysql-errors/8.4/en/server-error-reference.html#error_er_geometry_param_longitude_out_of_range" target="_top">
<code class="literal">
ER_GEOMETRY_PARAM_LONGITUDE_OUT_OF_RANGE
</code>
</a>
error occurs.
</p>
</li>
<li class="listitem">
<p>
If a latitude value is not in the range [−90, 90],
an
<a class="ulink" href="/doc/mysql-errors/8.4/en/server-error-reference.html#error_er_geometry_param_latitude_out_of_range" target="_top">
<code class="literal">
ER_GEOMETRY_PARAM_LATITUDE_OUT_OF_RANGE
</code>
</a>
error occurs.
</p>
</li>
</ul>
</div>
<p>
Ranges shown are in degrees. If an SRS uses another unit,
the range uses the corresponding values in its unit. The
exact range limits deviate slightly due to floating-point
arithmetic.
</p>
</li>
<li class="listitem">
<p>
Otherwise, the return value is non-
<code class="literal">
NULL
</code>
.
</p>
</li>
</ul>
</div>
<p>
Some functions in this section permit a unit argument that
specifies the length unit for the return value. Unless otherwise
specified, functions handle their unit argument as follows:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
A unit is supported if it is found in the
<code class="literal">
INFORMATION_SCHEMA
</code>
<a class="link" href="information-schema-st-units-of-measure-table.html" title="28.3.37 The INFORMATION_SCHEMA ST_UNITS_OF_MEASURE Table">
<code class="literal">
ST_UNITS_OF_MEASURE
</code>
</a>
table. See
<a class="xref" href="information-schema-st-units-of-measure-table.html" title="28.3.37 The INFORMATION_SCHEMA ST_UNITS_OF_MEASURE Table">
Section 28.3.37, “The INFORMATION_SCHEMA ST_UNITS_OF_MEASURE Table”
</a>
.
</p>
</li>
<li class="listitem">
<p>
If a unit is specified but not supported by MySQL, an
<a class="ulink" href="/doc/mysql-errors/8.4/en/server-error-reference.html#error_er_unit_not_found" target="_top">
<code class="literal">
ER_UNIT_NOT_FOUND
</code>
</a>
error
occurs.
</p>
</li>
<li class="listitem">
<p>
If a supported linear unit is specified and the SRID is 0,
an
<a class="ulink" href="/doc/mysql-errors/8.4/en/server-error-reference.html#error_er_geometry_in_unknown_length_unit" target="_top">
<code class="literal">
ER_GEOMETRY_IN_UNKNOWN_LENGTH_UNIT
</code>
</a>
error occurs.
</p>
</li>
<li class="listitem">
<p>
If a supported linear unit is specified and the SRID is not
0, the result is in that unit.
</p>
</li>
<li class="listitem">
<p>
If a unit is not specified, the result is in the unit of the
SRS of the geometries, whether Cartesian or geographic.
Currently, all MySQL SRSs are expressed in meters.
</p>
</li>
</ul>
</div>
<p>
These object-shape functions are available for testing geometry
relationships:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<a name="function_st-contains">
</a>
<p>
<a class="link" href="spatial-relation-functions-object-shapes.html#function_st-contains">
<code class="literal">
ST_Contains(
<em class="replaceable">
<code>
g1
</code>
</em>
,
<em class="replaceable">
<code>
g2
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045196594192">
</a>
<p>
Returns 1 or 0 to indicate whether
<em class="replaceable">
<code>
g1
</code>
</em>
completely contains
<em class="replaceable">
<code>
g2
</code>
</em>
. This tests the opposite
relationship as
<a class="link" href="spatial-relation-functions-object-shapes.html#function_st-within">
<code class="literal">
ST_Within()
</code>
</a>
.
</p>
<p>
<a class="link" href="spatial-relation-functions-object-shapes.html#function_st-contains">
<code class="literal">
ST_Contains()
</code>
</a>
handles its
arguments as described in the introduction to this section.
</p>
</li>
<li class="listitem">
<a name="function_st-crosses">
</a>
<p>
<a class="link" href="spatial-relation-functions-object-shapes.html#function_st-crosses">
<code class="literal">
ST_Crosses(
<em class="replaceable">
<code>
g1
</code>
</em>
,
<em class="replaceable">
<code>
g2
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045196583088">
</a>
<p>
Two geometries
<span class="emphasis">
<em>
spatially cross
</em>
</span>
if their
spatial relation has the following properties:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
Unless
<em class="replaceable">
<code>
g1
</code>
</em>
and
<em class="replaceable">
<code>
g2
</code>
</em>
are both of dimension 1:
<em class="replaceable">
<code>
g1
</code>
</em>
crosses
<em class="replaceable">
<code>
g2
</code>
</em>
if the interior of
<em class="replaceable">
<code>
g2
</code>
</em>
has points in common with
the interior of
<em class="replaceable">
<code>
g1
</code>
</em>
, but
<em class="replaceable">
<code>
g2
</code>
</em>
does not cover the entire
interior of
<em class="replaceable">
<code>
g1
</code>
</em>
.
</p>
</li>
<li class="listitem">
<p>
If both
<em class="replaceable">
<code>
g1
</code>
</em>
and
<em class="replaceable">
<code>
g2
</code>
</em>
are of dimension 1: If the
lines cross each other in a finite number of points
(that is, no common line segments, only single points in
common).
</p>
</li>
</ul>
</div>
<p>
This function returns 1 or 0 to indicate whether
<em class="replaceable">
<code>
g1
</code>
</em>
spatially crosses
<em class="replaceable">
<code>
g2
</code>
</em>
.
</p>
<p>
<a class="link" href="spatial-relation-functions-object-shapes.html#function_st-crosses">
<code class="literal">
ST_Crosses()
</code>
</a>
handles its
arguments as described in the introduction to this section
except that the return value is
<code class="literal">
NULL
</code>
for
these additional conditions:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
<em class="replaceable">
<code>
g1
</code>
</em>
is of dimension 2
(
<code class="literal">
Polygon
</code>
or
<code class="literal">
MultiPolygon
</code>
).
</p>
</li>
<li class="listitem">
<p>
<em class="replaceable">
<code>
g2
</code>
</em>
is of dimension 1
(
<code class="literal">
Point
</code>
or
<code class="literal">
MultiPoint
</code>
).
</p>
</li>
</ul>
</div>
</li>
<li class="listitem">
<a name="function_st-disjoint">
</a>
<p>
<a class="link" href="spatial-relation-functions-object-shapes.html#function_st-disjoint">
<code class="literal">
ST_Disjoint(
<em class="replaceable">
<code>
g1
</code>
</em>
,
<em class="replaceable">
<code>
g2
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045196559312">
</a>
<p>
Returns 1 or 0 to indicate whether
<em class="replaceable">
<code>
g1
</code>
</em>
is spatially disjoint from
(does not intersect)
<em class="replaceable">
<code>
g2
</code>
</em>
.
</p>
<p>
<a class="link" href="spatial-relation-functions-object-shapes.html#function_st-disjoint">
<code class="literal">
ST_Disjoint()
</code>
</a>
handles its
arguments as described in the introduction to this section.
</p>
</li>
<li class="listitem">
<a name="function_st-distance">
</a>
<p>
<a class="link" href="spatial-relation-functions-object-shapes.html#function_st-distance">
<code class="literal">
ST_Distance(
<em class="replaceable">
<code>
g1
</code>
</em>
,
<em class="replaceable">
<code>
g2
</code>
</em>
[,
<em class="replaceable">
<code>
unit
</code>
</em>
])
</code>
</a>
</p>
<a class="indexterm" name="idm46045196549056">
</a>
<p>
Returns the distance between
<em class="replaceable">
<code>
g1
</code>
</em>
and
<em class="replaceable">
<code>
g2
</code>
</em>
, measured in the length
unit of the spatial reference system (SRS) of the geometry
arguments, or in the unit of the optional
<em class="replaceable">
<code>
unit
</code>
</em>
argument if that is
specified.
</p>
<p>
This function processes geometry collections by returning
the shortest distance among all combinations of the
components of the two geometry arguments.
</p>
<p>
<a class="link" href="spatial-relation-functions-object-shapes.html#function_st-distance">
<code class="literal">
ST_Distance()
</code>
</a>
handles its
geometry arguments as described in the introduction to this
section, with these exceptions:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
<a class="link" href="spatial-relation-functions-object-shapes.html#function_st-distance">
<code class="literal">
ST_Distance()
</code>
</a>
detects
arguments in a geographic (ellipsoidal) spatial
reference system and returns the geodetic distance on
the ellipsoid.
<a class="link" href="spatial-relation-functions-object-shapes.html#function_st-distance">
<code class="literal">
ST_Distance()
</code>
</a>
supports
distance calculations for geographic SRS arguments of
all geometry types.
</p>
</li>
<li class="listitem">
<p>
If any argument is geometrically invalid, either the
result is an undefined distance (that is, it can be any
number), or an error occurs.
</p>
</li>
<li class="listitem">
<p>
If an intermediate or final result produces
<code class="literal">
NaN
</code>
or a negative number, an
<a class="ulink" href="/doc/mysql-errors/8.4/en/server-error-reference.html#error_er_gis_invalid_data" target="_top">
<code class="literal">
ER_GIS_INVALID_DATA
</code>
</a>
error occurs.
</p>
</li>
</ul>
</div>
<p>
<a class="link" href="spatial-relation-functions-object-shapes.html#function_st-distance">
<code class="literal">
ST_Distance()
</code>
</a>
permits
specifying the linear unit for the returned distance value
with an optional
<em class="replaceable">
<code>
unit
</code>
</em>
argument
which
<a class="link" href="spatial-relation-functions-object-shapes.html#function_st-distance">
<code class="literal">
ST_Distance()
</code>
</a>
handles
as described in the introduction to this section.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa58944072"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SET</span> <span class="token variable">@g1</span> <span class="token operator">=</span> <span class="token function">ST_GeomFromText</span><span class="token punctuation">(</span><span class="token string">'POINT(1 1)'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt">mysql></span> <span class="token keyword">SET</span> <span class="token variable">@g2</span> <span class="token operator">=</span> <span class="token function">ST_GeomFromText</span><span class="token punctuation">(</span><span class="token string">'POINT(2 2)'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">ST_Distance</span><span class="token punctuation">(</span><span class="token variable">@g1</span><span class="token punctuation">,</span> <span class="token variable">@g2</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> ST_Distance(@g1, @g2) <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 1.4142135623730951 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token prompt">mysql></span> <span class="token keyword">SET</span> <span class="token variable">@g1</span> <span class="token operator">=</span> <span class="token function">ST_GeomFromText</span><span class="token punctuation">(</span><span class="token string">'POINT(1 1)'</span><span class="token punctuation">,</span> <span class="token number">4326</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt">mysql></span> <span class="token keyword">SET</span> <span class="token variable">@g2</span> <span class="token operator">=</span> <span class="token function">ST_GeomFromText</span><span class="token punctuation">(</span><span class="token string">'POINT(2 2)'</span><span class="token punctuation">,</span> <span class="token number">4326</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">ST_Distance</span><span class="token punctuation">(</span><span class="token variable">@g1</span><span class="token punctuation">,</span> <span class="token variable">@g2</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> ST_Distance(@g1, @g2) <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 156874.3859490455 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">ST_Distance</span><span class="token punctuation">(</span><span class="token variable">@g1</span><span class="token punctuation">,</span> <span class="token variable">@g2</span><span class="token punctuation">,</span> <span class="token string">'metre'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> ST_Distance(@g1, @g2, 'metre') <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 156874.3859490455 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">ST_Distance</span><span class="token punctuation">(</span><span class="token variable">@g1</span><span class="token punctuation">,</span> <span class="token variable">@g2</span><span class="token punctuation">,</span> <span class="token string">'foot'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> ST_Distance(@g1, @g2, 'foot') <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 514679.7439273146 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
</div>
<p>
For the special case of distance calculations on a sphere,
see the
<a class="link" href="spatial-convenience-functions.html#function_st-distance-sphere">
<code class="literal">
ST_Distance_Sphere()
</code>
</a>
function.
</p>
</li>
<li class="listitem">
<a name="function_st-equals">
</a>
<p>
<a class="link" href="spatial-relation-functions-object-shapes.html#function_st-equals">
<code class="literal">
ST_Equals(
<em class="replaceable">
<code>
g1
</code>
</em>
,
<em class="replaceable">
<code>
g2
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045196516064">
</a>
<p>
Returns 1 or 0 to indicate whether
<em class="replaceable">
<code>
g1
</code>
</em>
is spatially equal to
<em class="replaceable">
<code>
g2
</code>
</em>
.
</p>
<p>
<a class="link" href="spatial-relation-functions-object-shapes.html#function_st-equals">
<code class="literal">
ST_Equals()
</code>
</a>
handles its
arguments as described in the introduction to this section,
except that it does not return
<code class="literal">
NULL
</code>
for
empty geometry arguments.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa14875369"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SET</span> <span class="token variable">@g1</span> <span class="token operator">=</span> <span class="token function">Point</span><span class="token punctuation">(</span><span class="token number">1</span><span class="token punctuation">,</span><span class="token number">1</span><span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token variable">@g2</span> <span class="token operator">=</span> <span class="token function">Point</span><span class="token punctuation">(</span><span class="token number">2</span><span class="token punctuation">,</span><span class="token number">2</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">ST_Equals</span><span class="token punctuation">(</span><span class="token variable">@g1</span><span class="token punctuation">,</span> <span class="token variable">@g1</span><span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token function">ST_Equals</span><span class="token punctuation">(</span><span class="token variable">@g1</span><span class="token punctuation">,</span> <span class="token variable">@g2</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> ST_Equals(@g1, @g1) <span class="token punctuation">|</span> ST_Equals(@g1, @g2) <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 1 <span class="token punctuation">|</span> 0 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
</div>
</li>
<li class="listitem">
<a name="function_st-frechetdistance">
</a>
<p>
<a class="link" href="spatial-relation-functions-object-shapes.html#function_st-frechetdistance">
<code class="literal">
ST_FrechetDistance(
<em class="replaceable">
<code>
g1
</code>
</em>
,
<em class="replaceable">
<code>
g2
</code>
</em>
[,
<em class="replaceable">
<code>
unit
</code>
</em>
])
</code>
</a>
</p>
<a class="indexterm" name="idm46045196501184">
</a>
<p>
Returns the discrete Fréchet distance between two
geometries, reflecting how similar the geometries are. The
result is a double-precision number measured in the length
unit of the spatial reference system (SRS) of the geometry
arguments, or in the length unit of the
<em class="replaceable">
<code>
unit
</code>
</em>
argument if that argument is
given.
</p>
<p>
This function implements the discrete Fréchet distance,
which means it is restricted to distances between the points
of the geometries. For example, given two
<code class="literal">
LineString
</code>
arguments, only the points
explicitly mentioned in the geometries are considered.
Points on the line segments between these points are not
considered.
</p>
<p>
<a class="link" href="spatial-relation-functions-object-shapes.html#function_st-frechetdistance">
<code class="literal">
ST_FrechetDistance()
</code>
</a>
handles
its geometry arguments as described in the introduction to
this section, with these exceptions:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
The geometries may have a Cartesian or geographic SRS,
but only
<code class="literal">
LineString
</code>
values are
supported. If the arguments are in the same Cartesian or
geographic SRS, but either is not a
<code class="literal">
LineString
</code>
, an
<a class="ulink" href="/doc/mysql-errors/8.4/en/server-error-reference.html#error_er_not_implemented_for_cartesian_srs" target="_top">
<code class="literal">
ER_NOT_IMPLEMENTED_FOR_CARTESIAN_SRS
</code>
</a>
or
<a class="ulink" href="/doc/mysql-errors/8.4/en/server-error-reference.html#error_er_not_implemented_for_geographic_srs" target="_top">
<code class="literal">
ER_NOT_IMPLEMENTED_FOR_GEOGRAPHIC_SRS
</code>
</a>
error occurs, depending on the SRS type.
</p>
</li>
</ul>
</div>
<p>
<a class="link" href="spatial-relation-functions-object-shapes.html#function_st-frechetdistance">
<code class="literal">
ST_FrechetDistance()
</code>
</a>
handles
its optional
<em class="replaceable">
<code>
unit
</code>
</em>
argument as
described in the introduction to this section.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa92131178"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SET</span> <span class="token variable">@ls1</span> <span class="token operator">=</span> <span class="token function">ST_GeomFromText</span><span class="token punctuation">(</span><span class="token string">'LINESTRING(0 0,0 5,5 5)'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt">mysql></span> <span class="token keyword">SET</span> <span class="token variable">@ls2</span> <span class="token operator">=</span> <span class="token function">ST_GeomFromText</span><span class="token punctuation">(</span><span class="token string">'LINESTRING(0 1,0 6,3 3,5 6)'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> ST_FrechetDistance<span class="token punctuation">(</span><span class="token variable">@ls1</span><span class="token punctuation">,</span> <span class="token variable">@ls2</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> ST_FrechetDistance(@ls1, @ls2) <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 2.8284271247461903 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token prompt">mysql></span> <span class="token keyword">SET</span> <span class="token variable">@ls1</span> <span class="token operator">=</span> <span class="token function">ST_GeomFromText</span><span class="token punctuation">(</span><span class="token string">'LINESTRING(0 0,0 5,5 5)'</span><span class="token punctuation">,</span> <span class="token number">4326</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt">mysql></span> <span class="token keyword">SET</span> <span class="token variable">@ls2</span> <span class="token operator">=</span> <span class="token function">ST_GeomFromText</span><span class="token punctuation">(</span><span class="token string">'LINESTRING(0 1,0 6,3 3,5 6)'</span><span class="token punctuation">,</span> <span class="token number">4326</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> ST_FrechetDistance<span class="token punctuation">(</span><span class="token variable">@ls1</span><span class="token punctuation">,</span> <span class="token variable">@ls2</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> ST_FrechetDistance(@ls1, @ls2) <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 313421.1999416798 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> ST_FrechetDistance<span class="token punctuation">(</span><span class="token variable">@ls1</span><span class="token punctuation">,</span> <span class="token variable">@ls2</span><span class="token punctuation">,</span> <span class="token string">'foot'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> ST_FrechetDistance(@ls1, @ls2, 'foot') <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 1028284.7767115477 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
</div>
</li>
<li class="listitem">
<a name="function_st-hausdorffdistance">
</a>
<p>
<a class="link" href="spatial-relation-functions-object-shapes.html#function_st-hausdorffdistance">
<code class="literal">
ST_HausdorffDistance(
<em class="replaceable">
<code>
g1
</code>
</em>
,
<em class="replaceable">
<code>
g2
</code>
</em>
[,
<em class="replaceable">
<code>
unit
</code>
</em>
])
</code>
</a>
</p>
<a class="indexterm" name="idm46045196473024">
</a>
<p>
Returns the discrete Hausdorff distance between two
geometries, reflecting how similar the geometries are. The
result is a double-precision number measured in the length
unit of the spatial reference system (SRS) of the geometry
arguments, or in the length unit of the
<em class="replaceable">
<code>
unit
</code>
</em>
argument if that argument is
given.
</p>
<p>
This function implements the discrete Hausdorff distance,
which means it is restricted to distances between the points
of the geometries. For example, given two
<code class="literal">
LineString
</code>
arguments, only the points
explicitly mentioned in the geometries are considered.
Points on the line segments between these points are not
considered.
</p>
<p>
<a class="link" href="spatial-relation-functions-object-shapes.html#function_st-hausdorffdistance">
<code class="literal">
ST_HausdorffDistance()
</code>
</a>
handles its geometry arguments as described in the
introduction to this section, with these exceptions:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
If the geometry arguments are in the same Cartesian or
geographic SRS, but are not in a supported combination,
an
<a class="ulink" href="/doc/mysql-errors/8.4/en/server-error-reference.html#error_er_not_implemented_for_cartesian_srs" target="_top">
<code class="literal">
ER_NOT_IMPLEMENTED_FOR_CARTESIAN_SRS
</code>
</a>
or
<a class="ulink" href="/doc/mysql-errors/8.4/en/server-error-reference.html#error_er_not_implemented_for_geographic_srs" target="_top">
<code class="literal">
ER_NOT_IMPLEMENTED_FOR_GEOGRAPHIC_SRS
</code>
</a>
error occurs, depending on the SRS type. These
combinations are supported:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: square; ">
<li class="listitem">
<p>
<code class="literal">
LineString
</code>
and
<code class="literal">
LineString
</code>
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
Point
</code>
and
<code class="literal">
MultiPoint
</code>
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
LineString
</code>
and
<code class="literal">
MultiLineString
</code>
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
MultiPoint
</code>
and
<code class="literal">
MultiPoint
</code>
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
MultiLineString
</code>
and
<code class="literal">
MultiLineString
</code>
</p>
</li>
</ul>
</div>
</li>
</ul>
</div>
<p>
<a class="link" href="spatial-relation-functions-object-shapes.html#function_st-hausdorffdistance">
<code class="literal">
ST_HausdorffDistance()
</code>
</a>
handles its optional
<em class="replaceable">
<code>
unit
</code>
</em>
argument as described in the introduction to this section.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa26894135"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SET</span> <span class="token variable">@ls1</span> <span class="token operator">=</span> <span class="token function">ST_GeomFromText</span><span class="token punctuation">(</span><span class="token string">'LINESTRING(0 0,0 5,5 5)'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt">mysql></span> <span class="token keyword">SET</span> <span class="token variable">@ls2</span> <span class="token operator">=</span> <span class="token function">ST_GeomFromText</span><span class="token punctuation">(</span><span class="token string">'LINESTRING(0 1,0 6,3 3,5 6)'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> ST_HausdorffDistance<span class="token punctuation">(</span><span class="token variable">@ls1</span><span class="token punctuation">,</span> <span class="token variable">@ls2</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> ST_HausdorffDistance(@ls1, @ls2) <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 1 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token prompt">mysql></span> <span class="token keyword">SET</span> <span class="token variable">@ls1</span> <span class="token operator">=</span> <span class="token function">ST_GeomFromText</span><span class="token punctuation">(</span><span class="token string">'LINESTRING(0 0,0 5,5 5)'</span><span class="token punctuation">,</span> <span class="token number">4326</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt">mysql></span> <span class="token keyword">SET</span> <span class="token variable">@ls2</span> <span class="token operator">=</span> <span class="token function">ST_GeomFromText</span><span class="token punctuation">(</span><span class="token string">'LINESTRING(0 1,0 6,3 3,5 6)'</span><span class="token punctuation">,</span> <span class="token number">4326</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> ST_HausdorffDistance<span class="token punctuation">(</span><span class="token variable">@ls1</span><span class="token punctuation">,</span> <span class="token variable">@ls2</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> ST_HausdorffDistance(@ls1, @ls2) <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 111319.49079326246 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> ST_HausdorffDistance<span class="token punctuation">(</span><span class="token variable">@ls1</span><span class="token punctuation">,</span> <span class="token variable">@ls2</span><span class="token punctuation">,</span> <span class="token string">'foot'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> ST_HausdorffDistance(@ls1, @ls2, 'foot') <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 365221.4264870815 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
</div>
</li>
<li class="listitem">
<a name="function_st-intersects">
</a>
<p>
<a class="link" href="spatial-relation-functions-object-shapes.html#function_st-intersects">
<code class="literal">
ST_Intersects(
<em class="replaceable">
<code>
g1
</code>
</em>
,
<em class="replaceable">
<code>
g2
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045196436032">
</a>
<p>
Returns 1 or 0 to indicate whether
<em class="replaceable">
<code>
g1
</code>
</em>
spatially intersects
<em class="replaceable">
<code>
g2
</code>
</em>
.
</p>
<p>
<a class="link" href="spatial-relation-functions-object-shapes.html#function_st-intersects">
<code class="literal">
ST_Intersects()
</code>
</a>
handles its
arguments as described in the introduction to this section.
</p>
</li>
<li class="listitem">
<a name="function_st-overlaps">
</a>
<p>
<a class="link" href="spatial-relation-functions-object-shapes.html#function_st-overlaps">
<code class="literal">
ST_Overlaps(
<em class="replaceable">
<code>
g1
</code>
</em>
,
<em class="replaceable">
<code>
g2
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045196426192">
</a>
<p>
Two geometries
<span class="emphasis">
<em>
spatially overlap
</em>
</span>
if
they intersect and their intersection results in a geometry
of the same dimension but not equal to either of the given
geometries.
</p>
<p>
This function returns 1 or 0 to indicate whether
<em class="replaceable">
<code>
g1
</code>
</em>
spatially overlaps
<em class="replaceable">
<code>
g2
</code>
</em>
.
</p>
<p>
<a class="link" href="spatial-relation-functions-object-shapes.html#function_st-overlaps">
<code class="literal">
ST_Overlaps()
</code>
</a>
handles its
arguments as described in the introduction to this section
except that the return value is
<code class="literal">
NULL
</code>
for
the additional condition that the dimensions of the two
geometries are not equal.
</p>
</li>
<li class="listitem">
<a name="function_st-touches">
</a>
<p>
<a class="link" href="spatial-relation-functions-object-shapes.html#function_st-touches">
<code class="literal">
ST_Touches(
<em class="replaceable">
<code>
g1
</code>
</em>
,
<em class="replaceable">
<code>
g2
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045196414432">
</a>
<p>
Two geometries
<span class="emphasis">
<em>
spatially touch
</em>
</span>
if their
interiors do not intersect, but the boundary of one of the
geometries intersects either the boundary or the interior of
the other.
</p>
<p>
This function returns 1 or 0 to indicate whether
<em class="replaceable">
<code>
g1
</code>
</em>
spatially touches
<em class="replaceable">
<code>
g2
</code>
</em>
.
</p>
<p>
<a class="link" href="spatial-relation-functions-object-shapes.html#function_st-touches">
<code class="literal">
ST_Touches()
</code>
</a>
handles its
arguments as described in the introduction to this section
except that the return value is
<code class="literal">
NULL
</code>
for
the additional condition that both geometries are of
dimension 0 (
<code class="literal">
Point
</code>
or
<code class="literal">
MultiPoint
</code>
).
</p>
</li>
<li class="listitem">
<a name="function_st-within">
</a>
<p>
<a class="link" href="spatial-relation-functions-object-shapes.html#function_st-within">
<code class="literal">
ST_Within(
<em class="replaceable">
<code>
g1
</code>
</em>
,
<em class="replaceable">
<code>
g2
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045196401248">
</a>
<p>
Returns 1 or 0 to indicate whether
<em class="replaceable">
<code>
g1
</code>
</em>
is spatially within
<em class="replaceable">
<code>
g2
</code>
</em>
. This tests the opposite
relationship as
<a class="link" href="spatial-relation-functions-object-shapes.html#function_st-contains">
<code class="literal">
ST_Contains()
</code>
</a>
.
</p>
<p>
<a class="link" href="spatial-relation-functions-object-shapes.html#function_st-within">
<code class="literal">
ST_Within()
</code>
</a>
handles its
arguments as described in the introduction to this section.
</p>
</li>
</ul>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/mysql-cluster-log-events.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="mysql-cluster-log-events">
</a>
25.6.3.2 NDB Cluster Log Events
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045093364752">
</a>
<a class="indexterm" name="idm46045093363264">
</a>
<p>
An event report reported in the event logs has the following
format:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-simple"><div class="docs-select-all right" id="sa9014183"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-simple"><em class="replaceable">datetime</em> <span class="token punctuation">[</span><em class="replaceable">string</em><span class="token punctuation">]</span> <em class="replaceable">severity</em> <span class="token operator">--</span> <em class="replaceable">message</em></code></pre>
</div>
<p>
For example:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-simple"><div class="docs-select-all right" id="sa80427459"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-simple">09<span class="token operator">:</span>19<span class="token operator">:</span>30 2005<span class="token operator">-</span>07<span class="token operator">-</span>24 <span class="token punctuation">[</span>NDB<span class="token punctuation">]</span> INFO <span class="token operator">--</span> Node 4 Start phase 4 completed</code></pre>
</div>
<p>
This section discusses all reportable events, ordered by
category and severity level within each category.
</p>
<p>
In the event descriptions, GCP and LCP mean
<span class="quote">
“
<span class="quote">
Global
Checkpoint
</span>
”
</span>
and
<span class="quote">
“
<span class="quote">
Local Checkpoint
</span>
”
</span>
,
respectively.
</p>
<a class="indexterm" name="idm46045093355888">
</a>
<a class="indexterm" name="idm46045093354400">
</a>
<a class="indexterm" name="idm46045093352400">
</a>
<a class="indexterm" name="idm46045093350912">
</a>
<h5>
<a name="idm46045093349824">
</a>
CONNECTION Events
</h5>
<p>
These events are associated with connections between Cluster
nodes.
</p>
<div class="table">
<a name="idm46045093348640">
</a>
<p class="title">
<b>
Table 25.28 Events associated with connections between
cluster nodes
</b>
</p>
<div class="table-contents">
<table>
<colgroup>
<col style="width: 35%"/>
<col style="width: 10%"/>
<col style="width: 10%"/>
<col style="width: 45%"/>
</colgroup>
<thead>
<tr>
<th scope="col">
Event
</th>
<th scope="col">
Priority
</th>
<th scope="col">
Severity Level
</th>
<th scope="col">
Description
</th>
</tr>
</thead>
<tbody>
<tr>
<th scope="row">
<code class="literal">
Connected
</code>
</th>
<td>
8
</td>
<td>
<code class="literal">
INFO
</code>
</td>
<td>
Data nodes connected
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
Disconnected
</code>
</th>
<td>
8
</td>
<td>
<code class="literal">
ALERT
</code>
</td>
<td>
Data nodes disconnected
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
CommunicationClosed
</code>
</th>
<td>
8
</td>
<td>
<code class="literal">
INFO
</code>
</td>
<td>
SQL node or data node connection closed
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
CommunicationOpened
</code>
</th>
<td>
8
</td>
<td>
<code class="literal">
INFO
</code>
</td>
<td>
SQL node or data node connection open
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
ConnectedApiVersion
</code>
</th>
<td>
8
</td>
<td>
<code class="literal">
INFO
</code>
</td>
<td>
Connection using API version
</td>
</tr>
</tbody>
</table>
</div>
</div>
<br class="table-break"/>
<h5>
<a name="idm46045093314096">
</a>
CHECKPOINT Events
</h5>
<a class="indexterm" name="idm46045093313408">
</a>
<a class="indexterm" name="idm46045093311920">
</a>
<p>
The logging messages shown here are associated with checkpoints.
</p>
<div class="table">
<a name="idm46045093310352">
</a>
<p class="title">
<b>
Table 25.29 Events associated with checkpoints
</b>
</p>
<div class="table-contents">
<table>
<colgroup>
<col style="width: 35%"/>
<col style="width: 10%"/>
<col style="width: 10%"/>
<col style="width: 45%"/>
</colgroup>
<thead>
<tr>
<th scope="col">
Event
</th>
<th scope="col">
Priority
</th>
<th scope="col">
Severity Level
</th>
<th scope="col">
Description
</th>
</tr>
</thead>
<tbody>
<tr>
<th scope="row">
<code class="literal">
GlobalCheckpointStarted
</code>
</th>
<td>
9
</td>
<td>
<code class="literal">
INFO
</code>
</td>
<td>
Start of GCP: REDO log is written to disk
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
GlobalCheckpointCompleted
</code>
</th>
<td>
10
</td>
<td>
<code class="literal">
INFO
</code>
</td>
<td>
GCP finished
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
LocalCheckpointStarted
</code>
</th>
<td>
7
</td>
<td>
<code class="literal">
INFO
</code>
</td>
<td>
Start of LCP: data written to disk
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
LocalCheckpointCompleted
</code>
</th>
<td>
7
</td>
<td>
<code class="literal">
INFO
</code>
</td>
<td>
LCP completed normally
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
LCPStoppedInCalcKeepGci
</code>
</th>
<td>
0
</td>
<td>
<code class="literal">
ALERT
</code>
</td>
<td>
LCP stopped
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
LCPFragmentCompleted
</code>
</th>
<td>
11
</td>
<td>
<code class="literal">
INFO
</code>
</td>
<td>
LCP on a fragment has been completed
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
UndoLogBlocked
</code>
</th>
<td>
7
</td>
<td>
<code class="literal">
INFO
</code>
</td>
<td>
UNDO logging blocked; buffer near overflow
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
RedoStatus
</code>
</th>
<td>
7
</td>
<td>
<code class="literal">
INFO
</code>
</td>
<td>
Redo status
</td>
</tr>
</tbody>
</table>
</div>
</div>
<br class="table-break"/>
<h5>
<a name="idm46045093260832">
</a>
STARTUP Events
</h5>
<a class="indexterm" name="idm46045093260144">
</a>
<a class="indexterm" name="idm46045093258656">
</a>
<p>
The following events are generated in response to the startup of
a node or of the cluster and of its success or failure. They
also provide information relating to the progress of the startup
process, including information concerning logging activities.
</p>
<div class="table">
<a name="idm46045093256880">
</a>
<p class="title">
<b>
Table 25.30 Events relating to the startup of a node or cluster
</b>
</p>
<div class="table-contents">
<table>
<colgroup>
<col style="width: 35%"/>
<col style="width: 10%"/>
<col style="width: 10%"/>
<col style="width: 45%"/>
</colgroup>
<thead>
<tr>
<th scope="col">
Event
</th>
<th scope="col">
Priority
</th>
<th scope="col">
Severity Level
</th>
<th scope="col">
Description
</th>
</tr>
</thead>
<tbody>
<tr>
<th scope="row">
<code class="literal">
NDBStartStarted
</code>
</th>
<td>
1
</td>
<td>
<code class="literal">
INFO
</code>
</td>
<td>
Data node start phases initiated (all nodes starting)
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
NDBStartCompleted
</code>
</th>
<td>
1
</td>
<td>
<code class="literal">
INFO
</code>
</td>
<td>
Start phases completed, all data nodes
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
STTORRYRecieved
</code>
</th>
<td>
15
</td>
<td>
<code class="literal">
INFO
</code>
</td>
<td>
Blocks received after completion of restart
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
StartPhaseCompleted
</code>
</th>
<td>
4
</td>
<td>
<code class="literal">
INFO
</code>
</td>
<td>
Data node start phase
<em class="replaceable">
<code>
X
</code>
</em>
completed
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
CM_REGCONF
</code>
</th>
<td>
3
</td>
<td>
<code class="literal">
INFO
</code>
</td>
<td>
Node has been successfully included into the cluster; shows the node,
managing node, and dynamic ID
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
CM_REGREF
</code>
</th>
<td>
8
</td>
<td>
<code class="literal">
INFO
</code>
</td>
<td>
Node has been refused for inclusion in the cluster; cannot be included
in cluster due to misconfiguration, inability to establish
communication, or other problem
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
FIND_NEIGHBOURS
</code>
</th>
<td>
8
</td>
<td>
<code class="literal">
INFO
</code>
</td>
<td>
Shows neighboring data nodes
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
NDBStopStarted
</code>
</th>
<td>
1
</td>
<td>
<code class="literal">
INFO
</code>
</td>
<td>
Data node shutdown initiated
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
NDBStopCompleted
</code>
</th>
<td>
1
</td>
<td>
<code class="literal">
INFO
</code>
</td>
<td>
Data node shutdown complete
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
NDBStopForced
</code>
</th>
<td>
1
</td>
<td>
<code class="literal">
ALERT
</code>
</td>
<td>
Forced shutdown of data node
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
NDBStopAborted
</code>
</th>
<td>
1
</td>
<td>
<code class="literal">
INFO
</code>
</td>
<td>
Unable to shut down data node normally
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
StartREDOLog
</code>
</th>
<td>
4
</td>
<td>
<code class="literal">
INFO
</code>
</td>
<td>
New redo log started; GCI keep
<em class="replaceable">
<code>
X
</code>
</em>
, newest
restorable GCI
<em class="replaceable">
<code>
Y
</code>
</em>
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
StartLog
</code>
</th>
<td>
10
</td>
<td>
<code class="literal">
INFO
</code>
</td>
<td>
New log started; log part
<em class="replaceable">
<code>
X
</code>
</em>
, start MB
<em class="replaceable">
<code>
Y
</code>
</em>
, stop MB
<em class="replaceable">
<code>
Z
</code>
</em>
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
UNDORecordsExecuted
</code>
</th>
<td>
15
</td>
<td>
<code class="literal">
INFO
</code>
</td>
<td>
Undo records executed
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
StartReport
</code>
</th>
<td>
4
</td>
<td>
<code class="literal">
INFO
</code>
</td>
<td>
Report started
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
LogFileInitStatus
</code>
</th>
<td>
7
</td>
<td>
<code class="literal">
INFO
</code>
</td>
<td>
Log file initialization status
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
LogFileInitCompStatus
</code>
</th>
<td>
7
</td>
<td>
<code class="literal">
INFO
</code>
</td>
<td>
Log file completion status
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
StartReadLCP
</code>
</th>
<td>
10
</td>
<td>
<code class="literal">
INFO
</code>
</td>
<td>
Start read for local checkpoint
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
ReadLCPComplete
</code>
</th>
<td>
10
</td>
<td>
<code class="literal">
INFO
</code>
</td>
<td>
Read for local checkpoint completed
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
RunRedo
</code>
</th>
<td>
8
</td>
<td>
<code class="literal">
INFO
</code>
</td>
<td>
Running the redo log
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
RebuildIndex
</code>
</th>
<td>
10
</td>
<td>
<code class="literal">
INFO
</code>
</td>
<td>
Rebuilding indexes
</td>
</tr>
</tbody>
</table>
</div>
<div class="table-contents">
<table cellpadding="0" cellspacing="0" style="position: fixed; top: 0px; display: none; left: 401px; width: 739px;">
<thead>
<tr>
<th scope="col" style="width: 258.297px;">
Event
</th>
<th scope="col" style="width: 73.7969px;">
Priority
</th>
<th scope="col" style="width: 73.7969px;">
Severity Level
</th>
<th scope="col" style="width: 332.109px;">
Description
</th>
</tr>
</thead>
</table>
</div>
</div>
<br class="table-break"/>
<h5>
<a name="idm46045093140032">
</a>
NODERESTART Events
</h5>
<a class="indexterm" name="idm46045093139344">
</a>
<a class="indexterm" name="idm46045093137856">
</a>
<p>
The following events are generated when restarting a node and
relate to the success or failure of the node restart process.
</p>
<div class="table">
<a name="idm46045093136224">
</a>
<p class="title">
<b>
Table 25.31 Events relating to restarting a node
</b>
</p>
<div class="table-contents">
<table>
<colgroup>
<col style="width: 35%"/>
<col style="width: 10%"/>
<col style="width: 10%"/>
<col style="width: 45%"/>
</colgroup>
<thead>
<tr>
<th scope="col">
Event
</th>
<th scope="col">
Priority
</th>
<th scope="col">
Severity Level
</th>
<th scope="col">
Description
</th>
</tr>
</thead>
<tbody>
<tr>
<th scope="row">
<code class="literal">
NR_CopyDict
</code>
</th>
<td>
7
</td>
<td>
<code class="literal">
INFO
</code>
</td>
<td>
Completed copying of dictionary information
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
NR_CopyDistr
</code>
</th>
<td>
7
</td>
<td>
<code class="literal">
INFO
</code>
</td>
<td>
Completed copying distribution information
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
NR_CopyFragsStarted
</code>
</th>
<td>
7
</td>
<td>
<code class="literal">
INFO
</code>
</td>
<td>
Starting to copy fragments
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
NR_CopyFragDone
</code>
</th>
<td>
10
</td>
<td>
<code class="literal">
INFO
</code>
</td>
<td>
Completed copying a fragment
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
NR_CopyFragsCompleted
</code>
</th>
<td>
7
</td>
<td>
<code class="literal">
INFO
</code>
</td>
<td>
Completed copying all fragments
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
NodeFailCompleted
</code>
</th>
<td>
8
</td>
<td>
<code class="literal">
ALERT
</code>
</td>
<td>
Node failure phase completed
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
NODE_FAILREP
</code>
</th>
<td>
8
</td>
<td>
<code class="literal">
ALERT
</code>
</td>
<td>
Reports that a node has failed
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
ArbitState
</code>
</th>
<td>
6
</td>
<td>
<code class="literal">
INFO
</code>
</td>
<td>
Report whether an arbitrator is found or not; there are seven different
possible outcomes when seeking an arbitrator, listed here:
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
Management server restarts arbitration thread
[state=
<em class="replaceable">
<code>
X
</code>
</em>
]
</p>
</li>
<li class="listitem">
<p>
Prepare arbitrator node
<em class="replaceable">
<code>
X
</code>
</em>
[ticket=
<em class="replaceable">
<code>
Y
</code>
</em>
]
</p>
</li>
<li class="listitem">
<p>
Receive arbitrator node
<em class="replaceable">
<code>
X
</code>
</em>
[ticket=
<em class="replaceable">
<code>
Y
</code>
</em>
]
</p>
</li>
<li class="listitem">
<p>
Started arbitrator node
<em class="replaceable">
<code>
X
</code>
</em>
[ticket=
<em class="replaceable">
<code>
Y
</code>
</em>
]
</p>
</li>
<li class="listitem">
<p>
Lost arbitrator node
<em class="replaceable">
<code>
X
</code>
</em>
-
process failure [state=
<em class="replaceable">
<code>
Y
</code>
</em>
]
</p>
</li>
<li class="listitem">
<p>
Lost arbitrator node
<em class="replaceable">
<code>
X
</code>
</em>
-
process exit [state=
<em class="replaceable">
<code>
Y
</code>
</em>
]
</p>
</li>
<li class="listitem">
<p>
Lost arbitrator node
<em class="replaceable">
<code>
X
</code>
</em>
<error msg>
[state=
<em class="replaceable">
<code>
Y
</code>
</em>
]
</p>
</li>
</ul>
</div>
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
ArbitResult
</code>
</th>
<td>
2
</td>
<td>
<code class="literal">
ALERT
</code>
</td>
<td>
Report arbitrator results; there are eight different possible results
for arbitration attempts, listed here:
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
Arbitration check failed: less than 1/2 nodes left
</p>
</li>
<li class="listitem">
<p>
Arbitration check succeeded: node group majority
</p>
</li>
<li class="listitem">
<p>
Arbitration check failed: missing node group
</p>
</li>
<li class="listitem">
<p>
Network partitioning: arbitration required
</p>
</li>
<li class="listitem">
<p>
Arbitration succeeded: affirmative response from
node
<em class="replaceable">
<code>
X
</code>
</em>
</p>
</li>
<li class="listitem">
<p>
Arbitration failed: negative response from node
<em class="replaceable">
<code>
X
</code>
</em>
</p>
</li>
<li class="listitem">
<p>
Network partitioning: no arbitrator available
</p>
</li>
<li class="listitem">
<p>
Network partitioning: no arbitrator configured
</p>
</li>
</ul>
</div>
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
GCP_TakeoverStarted
</code>
</th>
<td>
7
</td>
<td>
<code class="literal">
INFO
</code>
</td>
<td>
GCP takeover started
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
GCP_TakeoverCompleted
</code>
</th>
<td>
7
</td>
<td>
<code class="literal">
INFO
</code>
</td>
<td>
GCP takeover complete
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
LCP_TakeoverStarted
</code>
</th>
<td>
7
</td>
<td>
<code class="literal">
INFO
</code>
</td>
<td>
LCP takeover started
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
LCP_TakeoverCompleted
</code>
</th>
<td>
7
</td>
<td>
<code class="literal">
INFO
</code>
</td>
<td>
LCP takeover complete (state =
<em class="replaceable">
<code>
X
</code>
</em>
)
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
ConnectCheckStarted
</code>
</th>
<td>
6
</td>
<td>
<code class="literal">
INFO
</code>
</td>
<td>
Connection check started
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
ConnectCheckCompleted
</code>
</th>
<td>
6
</td>
<td>
<code class="literal">
INFO
</code>
</td>
<td>
Connection check completed
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
NodeFailRejected
</code>
</th>
<td>
6
</td>
<td>
<code class="literal">
ALERT
</code>
</td>
<td>
Node failure phase failed
</td>
</tr>
</tbody>
</table>
</div>
<div class="table-contents">
<table cellpadding="0" cellspacing="0" style="position: fixed; top: 0px; display: none; left: 401px; width: 739px;">
<thead>
<tr>
<th scope="col" style="width: 258.297px;">
Event
</th>
<th scope="col" style="width: 73.7969px;">
Priority
</th>
<th scope="col" style="width: 73.7969px;">
Severity Level
</th>
<th scope="col" style="width: 332.109px;">
Description
</th>
</tr>
</thead>
</table>
</div>
</div>
<br class="table-break"/>
<h5>
<a name="idm46045093026416">
</a>
STATISTICS Events
</h5>
<a class="indexterm" name="idm46045093025728">
</a>
<a class="indexterm" name="idm46045093024240">
</a>
<p>
The following events are of a statistical nature. They provide
information such as numbers of transactions and other
operations, amount of data sent or received by individual nodes,
and memory usage.
</p>
<div class="table">
<a name="idm46045093022512">
</a>
<p class="title">
<b>
Table 25.32 Events of a statistical nature
</b>
</p>
<div class="table-contents">
<table>
<colgroup>
<col style="width: 35%"/>
<col style="width: 10%"/>
<col style="width: 10%"/>
<col style="width: 45%"/>
</colgroup>
<thead>
<tr>
<th scope="col">
Event
</th>
<th scope="col">
Priority
</th>
<th scope="col">
Severity Level
</th>
<th scope="col">
Description
</th>
</tr>
</thead>
<tbody>
<tr>
<th scope="row">
<code class="literal">
TransReportCounters
</code>
</th>
<td>
8
</td>
<td>
<code class="literal">
INFO
</code>
</td>
<td>
Report transaction statistics, including numbers of transactions,
commits, reads, simple reads, writes, concurrent
operations, attribute information, and aborts
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
OperationReportCounters
</code>
</th>
<td>
8
</td>
<td>
<code class="literal">
INFO
</code>
</td>
<td>
Number of operations
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
TableCreated
</code>
</th>
<td>
7
</td>
<td>
<code class="literal">
INFO
</code>
</td>
<td>
Report number of tables created
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
JobStatistic
</code>
</th>
<td>
9
</td>
<td>
<code class="literal">
INFO
</code>
</td>
<td>
Mean internal job scheduling statistics
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
ThreadConfigLoop
</code>
</th>
<td>
9
</td>
<td>
<code class="literal">
INFO
</code>
</td>
<td>
Number of thread configuration loops
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
SendBytesStatistic
</code>
</th>
<td>
9
</td>
<td>
<code class="literal">
INFO
</code>
</td>
<td>
Mean number of bytes sent to node
<em class="replaceable">
<code>
X
</code>
</em>
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
ReceiveBytesStatistic
</code>
</th>
<td>
9
</td>
<td>
<code class="literal">
INFO
</code>
</td>
<td>
Mean number of bytes received from node
<em class="replaceable">
<code>
X
</code>
</em>
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
MemoryUsage
</code>
</th>
<td>
5
</td>
<td>
<code class="literal">
INFO
</code>
</td>
<td>
Data and index memory usage (80%, 90%, and 100%)
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
MTSignalStatistics
</code>
</th>
<td>
9
</td>
<td>
<code class="literal">
INFO
</code>
</td>
<td>
Multithreaded signals
</td>
</tr>
</tbody>
</table>
</div>
</div>
<br class="table-break"/>
<h5>
<a name="idm46045092967328">
</a>
SCHEMA Events
</h5>
<a class="indexterm" name="idm46045092966640">
</a>
<a class="indexterm" name="idm46045092965152">
</a>
<p>
These events relate to NDB Cluster schema operations.
</p>
<div class="table">
<a name="idm46045092963600">
</a>
<p class="title">
<b>
Table 25.33 Events relating to NDB Cluster schema operations
</b>
</p>
<div class="table-contents">
<table>
<colgroup>
<col style="width: 35%"/>
<col style="width: 10%"/>
<col style="width: 10%"/>
<col style="width: 45%"/>
</colgroup>
<thead>
<tr>
<th scope="col">
Event
</th>
<th scope="col">
Priority
</th>
<th scope="col">
Severity Level
</th>
<th scope="col">
Description
</th>
</tr>
</thead>
<tbody>
<tr>
<th scope="row">
<code class="literal">
CreateSchemaObject
</code>
</th>
<td>
8
</td>
<td>
<code class="literal">
INFO
</code>
</td>
<td>
Schema objected created
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
AlterSchemaObject
</code>
</th>
<td>
8
</td>
<td>
<code class="literal">
INFO
</code>
</td>
<td>
Schema object updated
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
DropSchemaObject
</code>
</th>
<td>
8
</td>
<td>
<code class="literal">
INFO
</code>
</td>
<td>
Schema object dropped
</td>
</tr>
</tbody>
</table>
</div>
</div>
<br class="table-break"/>
<h5>
<a name="idm46045092939072">
</a>
ERROR Events
</h5>
<a class="indexterm" name="idm46045092938384">
</a>
<a class="indexterm" name="idm46045092936896">
</a>
<p>
These events relate to Cluster errors and warnings. The presence
of one or more of these generally indicates that a major
malfunction or failure has occurred.
</p>
<div class="table">
<a name="idm46045092935216">
</a>
<p class="title">
<b>
Table 25.34 Events relating to cluster errors and warnings
</b>
</p>
<div class="table-contents">
<table>
<colgroup>
<col style="width: 35%"/>
<col style="width: 10%"/>
<col style="width: 10%"/>
<col style="width: 45%"/>
</colgroup>
<thead>
<tr>
<th scope="col">
Event
</th>
<th scope="col">
Priority
</th>
<th scope="col">
Severity Level
</th>
<th scope="col">
Description
</th>
</tr>
</thead>
<tbody>
<tr>
<th scope="row">
<code class="literal">
TransporterError
</code>
</th>
<td>
2
</td>
<td>
<code class="literal">
ERROR
</code>
</td>
<td>
Transporter error
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
TransporterWarning
</code>
</th>
<td>
8
</td>
<td>
<code class="literal">
WARNING
</code>
</td>
<td>
Transporter warning
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
MissedHeartbeat
</code>
</th>
<td>
8
</td>
<td>
<code class="literal">
WARNING
</code>
</td>
<td>
Node
<em class="replaceable">
<code>
X
</code>
</em>
missed heartbeat number
<em class="replaceable">
<code>
Y
</code>
</em>
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
DeadDueToHeartbeat
</code>
</th>
<td>
8
</td>
<td>
<code class="literal">
ALERT
</code>
</td>
<td>
Node
<em class="replaceable">
<code>
X
</code>
</em>
declared
<span class="quote">
“
<span class="quote">
dead
</span>
”
</span>
due to
missed heartbeat
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
WarningEvent
</code>
</th>
<td>
2
</td>
<td>
<code class="literal">
WARNING
</code>
</td>
<td>
General warning event
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
SubscriptionStatus
</code>
</th>
<td>
4
</td>
<td>
<code class="literal">
WARNING
</code>
</td>
<td>
Change in subscription status
</td>
</tr>
</tbody>
</table>
</div>
</div>
<br class="table-break"/>
<h5>
<a name="idm46045092894176">
</a>
INFO Events
</h5>
<a class="indexterm" name="idm46045092893488">
</a>
<a class="indexterm" name="idm46045092892000">
</a>
<p>
These events provide general information about the state of the
cluster and activities associated with Cluster maintenance, such
as logging and heartbeat transmission.
</p>
<div class="table">
<a name="idm46045092890320">
</a>
<p class="title">
<b>
Table 25.35 Information events
</b>
</p>
<div class="table-contents">
<table>
<colgroup>
<col style="width: 35%"/>
<col style="width: 10%"/>
<col style="width: 10%"/>
<col style="width: 45%"/>
</colgroup>
<thead>
<tr>
<th scope="col">
Event
</th>
<th scope="col">
Priority
</th>
<th scope="col">
Severity Level
</th>
<th scope="col">
Description
</th>
</tr>
</thead>
<tbody>
<tr>
<th scope="row">
<code class="literal">
SentHeartbeat
</code>
</th>
<td>
12
</td>
<td>
<code class="literal">
INFO
</code>
</td>
<td>
Sent heartbeat
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
CreateLogBytes
</code>
</th>
<td>
11
</td>
<td>
<code class="literal">
INFO
</code>
</td>
<td>
Create log: Log part, log file, size in MB
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
InfoEvent
</code>
</th>
<td>
2
</td>
<td>
<code class="literal">
INFO
</code>
</td>
<td>
General informational event
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
EventBufferStatus
</code>
</th>
<td>
7
</td>
<td>
<code class="literal">
INFO
</code>
</td>
<td>
Event buffer status
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
EventBufferStatus2
</code>
</th>
<td>
7
</td>
<td>
<code class="literal">
INFO
</code>
</td>
<td>
Improved event buffer status information
</td>
</tr>
</tbody>
</table>
</div>
</div>
<br class="table-break"/>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
<code class="literal">
SentHeartbeat
</code>
events are available only if
NDB Cluster was compiled with
<code class="literal">
VM_TRACE
</code>
enabled.
</p>
</div>
<h5>
<a name="idm46045092853520">
</a>
SINGLEUSER Events
</h5>
<a class="indexterm" name="idm46045092852832">
</a>
<a class="indexterm" name="idm46045092851344">
</a>
<p>
These events are associated with entering and exiting single
user mode.
</p>
<div class="table">
<a name="idm46045092849760">
</a>
<p class="title">
<b>
Table 25.36 Events relating to single user mode
</b>
</p>
<div class="table-contents">
<table>
<colgroup>
<col style="width: 35%"/>
<col style="width: 10%"/>
<col style="width: 10%"/>
<col style="width: 45%"/>
</colgroup>
<thead>
<tr>
<th scope="col">
Event
</th>
<th scope="col">
Priority
</th>
<th scope="col">
Severity Level
</th>
<th scope="col">
Description
</th>
</tr>
</thead>
<tbody>
<tr>
<th scope="row">
<code class="literal">
SingleUser
</code>
</th>
<td>
7
</td>
<td>
<code class="literal">
INFO
</code>
</td>
<td>
Entering or exiting single user mode
</td>
</tr>
</tbody>
</table>
</div>
</div>
<br class="table-break"/>
<h5>
<a name="idm46045092835184">
</a>
BACKUP Events
</h5>
<a class="indexterm" name="idm46045092834496">
</a>
<a class="indexterm" name="idm46045092833008">
</a>
<p>
These events provide information about backups being created or
restored.
</p>
<div class="table">
<a name="idm46045092831424">
</a>
<p class="title">
<b>
Table 25.37 Backup events
</b>
</p>
<div class="table-contents">
<table>
<colgroup>
<col style="width: 35%"/>
<col style="width: 10%"/>
<col style="width: 10%"/>
<col style="width: 45%"/>
</colgroup>
<thead>
<tr>
<th scope="col">
Event
</th>
<th scope="col">
Priority
</th>
<th scope="col">
Severity Level
</th>
<th scope="col">
Description
</th>
</tr>
</thead>
<tbody>
<tr>
<th scope="row">
<code class="literal">
BackupStarted
</code>
</th>
<td>
7
</td>
<td>
<code class="literal">
INFO
</code>
</td>
<td>
Backup started
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
BackupStatus
</code>
</th>
<td>
7
</td>
<td>
<code class="literal">
INFO
</code>
</td>
<td>
Backup status
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
BackupCompleted
</code>
</th>
<td>
7
</td>
<td>
<code class="literal">
INFO
</code>
</td>
<td>
Backup completed
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
BackupFailedToStart
</code>
</th>
<td>
7
</td>
<td>
<code class="literal">
ALERT
</code>
</td>
<td>
Backup failed to start
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
BackupAborted
</code>
</th>
<td>
7
</td>
<td>
<code class="literal">
ALERT
</code>
</td>
<td>
Backup aborted by user
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
RestoreStarted
</code>
</th>
<td>
7
</td>
<td>
<code class="literal">
INFO
</code>
</td>
<td>
Started restoring from backup
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
RestoreMetaData
</code>
</th>
<td>
7
</td>
<td>
<code class="literal">
INFO
</code>
</td>
<td>
Restoring metadata
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
RestoreData
</code>
</th>
<td>
7
</td>
<td>
<code class="literal">
INFO
</code>
</td>
<td>
Restoring data
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
RestoreLog
</code>
</th>
<td>
7
</td>
<td>
<code class="literal">
INFO
</code>
</td>
<td>
Restoring log files
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
RestoreCompleted
</code>
</th>
<td>
7
</td>
<td>
<code class="literal">
INFO
</code>
</td>
<td>
Completed restoring from backup
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
SavedEvent
</code>
</th>
<td>
7
</td>
<td>
<code class="literal">
INFO
</code>
</td>
<td>
Event saved
</td>
</tr>
</tbody>
</table>
</div>
<div class="table-contents">
<table cellpadding="0" cellspacing="0" style="position: fixed; top: 0px; display: none; left: 401px; width: 739px;">
<thead>
<tr>
<th scope="col" style="width: 258.297px;">
Event
</th>
<th scope="col" style="width: 73.7969px;">
Priority
</th>
<th scope="col" style="width: 73.7969px;">
Severity Level
</th>
<th scope="col" style="width: 332.109px;">
Description
</th>
</tr>
</thead>
</table>
</div>
</div>
<br class="table-break"/>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/replication-implementation.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h2 class="title">
<a name="replication-implementation">
</a>
19.2 Replication Implementation
</h2>
</div>
</div>
</div>
<div class="toc">
<dl class="toc">
<dt>
<span class="section">
<a href="replication-formats.html">
19.2.1 Replication Formats
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="replication-channels.html">
19.2.2 Replication Channels
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="replication-threads.html">
19.2.3 Replication Threads
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="replica-logs.html">
19.2.4 Relay Log and Replication Metadata Repositories
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="replication-rules.html">
19.2.5 How Servers Evaluate Replication Filtering Rules
</a>
</span>
</dt>
</dl>
</div>
<a class="indexterm" name="idm46045138569168">
</a>
<p>
Replication is based on the source server keeping track of all
changes to its databases (updates, deletes, and so on) in its binary
log. The binary log serves as a written record of all events that
modify database structure or content (data) from the moment the
server was started. Typically,
<a class="link" href="select.html" title="15.2.13 SELECT Statement">
<code class="literal">
SELECT
</code>
</a>
statements are not recorded because they modify neither database
structure nor content.
</p>
<p>
Each replica that connects to the source requests a copy of the
binary log. That is, it pulls the data from the source, rather than
the source pushing the data to the replica. The replica also
executes the events from the binary log that it receives. This has
the effect of repeating the original changes just as they were made
on the source. Tables are created or their structure modified, and
data is inserted, deleted, and updated according to the changes that
were originally made on the source.
</p>
<p>
Because each replica is independent, the replaying of the changes
from the source's binary log occurs independently on each replica
that is connected to the source. In addition, because each replica
receives a copy of the binary log only by requesting it from the
source, the replica is able to read and update the copy of the
database at its own pace and can start and stop the replication
process at will without affecting the ability to update to the
latest database status on either the source or replica side.
</p>
<p>
For more information on the specifics of the replication
implementation, see
<a class="xref" href="replication-threads.html" title="19.2.3 Replication Threads">
Section 19.2.3, “Replication Threads”
</a>
.
</p>
<p>
Source servers and replicas report their status in respect of the
replication process regularly so that you can monitor them. See
<a class="xref" href="thread-information.html" title="10.14 Examining Server Thread (Process) Information">
Section 10.14, “Examining Server Thread (Process) Information”
</a>
, for descriptions of all
replicated-related states.
</p>
<p>
The source's binary log is written to a local relay log on the
replica before it is processed. The replica also records information
about the current position with the source's binary log and the
local relay log. See
<a class="xref" href="replica-logs.html" title="19.2.4 Relay Log and Replication Metadata Repositories">
Section 19.2.4, “Relay Log and Replication Metadata Repositories”
</a>
.
</p>
<p>
Database changes are filtered on the replica according to a set of
rules that are applied according to the various configuration
options and variables that control event evaluation. For details on
how these rules are applied, see
<a class="xref" href="replication-rules.html" title="19.2.5 How Servers Evaluate Replication Filtering Rules">
Section 19.2.5, “How Servers Evaluate Replication Filtering Rules”
</a>
.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/adding-character-set.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h2 class="title">
<a name="adding-character-set">
</a>
12.13 Adding a Character Set
</h2>
</div>
</div>
</div>
<div class="toc">
<dl class="toc">
<dt>
<span class="section">
<a href="character-arrays.html">
12.13.1 Character Definition Arrays
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="string-collating.html">
12.13.2 String Collating Support for Complex Character Sets
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="multibyte-characters.html">
12.13.3 Multi-Byte Character Support for Complex Character Sets
</a>
</span>
</dt>
</dl>
</div>
<a class="indexterm" name="idm46045215437088">
</a>
<a class="indexterm" name="idm46045215435600">
</a>
<p>
This section discusses the procedure for adding a character set to
MySQL. The proper procedure depends on whether the character set
is simple or complex:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
If the character set does not need special string collating
routines for sorting and does not need multibyte character
support, it is simple.
</p>
</li>
<li class="listitem">
<p>
If the character set needs either of those features, it is
complex.
</p>
</li>
</ul>
</div>
<p>
For example,
<code class="literal">
greek
</code>
and
<code class="literal">
swe7
</code>
are simple character sets, whereas
<code class="literal">
big5
</code>
and
<code class="literal">
czech
</code>
are complex character sets.
</p>
<p>
To use the following instructions, you must have a MySQL source
distribution. In the instructions,
<em class="replaceable">
<code>
MYSET
</code>
</em>
represents the name of the
character set that you want to add.
</p>
<div class="orderedlist">
<ol class="orderedlist" type="1">
<li class="listitem">
<p>
Add a
<code class="literal">
<charset>
</code>
element for
<em class="replaceable">
<code>
MYSET
</code>
</em>
to the
<code class="filename">
sql/share/charsets/Index.xml
</code>
file. Use
the existing contents in the file as a guide to adding new
contents. A partial listing for the
<code class="literal">
latin1
</code>
<code class="literal">
<charset>
</code>
element follows:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-xml"><div class="docs-select-all right" id="sa56234711"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-xml"><span class="token tag"><span class="token tag"><span class="token punctuation"><</span>charset</span> <span class="token attr-name">name</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>latin1<span class="token punctuation">"</span></span><span class="token punctuation">></span></span>
<span class="token tag"><span class="token tag"><span class="token punctuation"><</span>family</span><span class="token punctuation">></span></span>Western<span class="token tag"><span class="token tag"><span class="token punctuation"></</span>family</span><span class="token punctuation">></span></span>
<span class="token tag"><span class="token tag"><span class="token punctuation"><</span>description</span><span class="token punctuation">></span></span>cp1252 West European<span class="token tag"><span class="token tag"><span class="token punctuation"></</span>description</span><span class="token punctuation">></span></span>
...
<span class="token tag"><span class="token tag"><span class="token punctuation"><</span>collation</span> <span class="token attr-name">name</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>latin1_swedish_ci<span class="token punctuation">"</span></span> <span class="token attr-name">id</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>8<span class="token punctuation">"</span></span> <span class="token attr-name">order</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>Finnish, Swedish<span class="token punctuation">"</span></span><span class="token punctuation">></span></span>
<span class="token tag"><span class="token tag"><span class="token punctuation"><</span>flag</span><span class="token punctuation">></span></span>primary<span class="token tag"><span class="token tag"><span class="token punctuation"></</span>flag</span><span class="token punctuation">></span></span>
<span class="token tag"><span class="token tag"><span class="token punctuation"><</span>flag</span><span class="token punctuation">></span></span>compiled<span class="token tag"><span class="token tag"><span class="token punctuation"></</span>flag</span><span class="token punctuation">></span></span>
<span class="token tag"><span class="token tag"><span class="token punctuation"></</span>collation</span><span class="token punctuation">></span></span>
<span class="token tag"><span class="token tag"><span class="token punctuation"><</span>collation</span> <span class="token attr-name">name</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>latin1_danish_ci<span class="token punctuation">"</span></span> <span class="token attr-name">id</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>15<span class="token punctuation">"</span></span> <span class="token attr-name">order</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>Danish<span class="token punctuation">"</span></span><span class="token punctuation">/></span></span>
...
<span class="token tag"><span class="token tag"><span class="token punctuation"><</span>collation</span> <span class="token attr-name">name</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>latin1_bin<span class="token punctuation">"</span></span> <span class="token attr-name">id</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>47<span class="token punctuation">"</span></span> <span class="token attr-name">order</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>Binary<span class="token punctuation">"</span></span><span class="token punctuation">></span></span>
<span class="token tag"><span class="token tag"><span class="token punctuation"><</span>flag</span><span class="token punctuation">></span></span>binary<span class="token tag"><span class="token tag"><span class="token punctuation"></</span>flag</span><span class="token punctuation">></span></span>
<span class="token tag"><span class="token tag"><span class="token punctuation"><</span>flag</span><span class="token punctuation">></span></span>compiled<span class="token tag"><span class="token tag"><span class="token punctuation"></</span>flag</span><span class="token punctuation">></span></span>
<span class="token tag"><span class="token tag"><span class="token punctuation"></</span>collation</span><span class="token punctuation">></span></span>
...
<span class="token tag"><span class="token tag"><span class="token punctuation"></</span>charset</span><span class="token punctuation">></span></span></code></pre>
</div>
<p>
The
<code class="literal">
<charset>
</code>
element must list all
the collations for the character set. These must include at
least a binary collation and a default (primary) collation.
The default collation is often named using a suffix of
<code class="literal">
general_ci
</code>
(general, case-insensitive). It
is possible for the binary collation to be the default
collation, but usually they are different. The default
collation should have a
<code class="literal">
primary
</code>
flag. The
binary collation should have a
<code class="literal">
binary
</code>
flag.
</p>
<p>
You must assign a unique ID number to each collation. The
range of IDs from 1024 to 2047 is reserved for user-defined
collations. To find the maximum of the currently used
collation IDs, use this query:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa95566446"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SELECT</span> <span class="token function">MAX</span><span class="token punctuation">(</span>ID<span class="token punctuation">)</span> <span class="token keyword">FROM</span> INFORMATION_SCHEMA<span class="token punctuation">.</span>COLLATIONS<span class="token punctuation">;</span></code></pre>
</div>
</li>
<li class="listitem">
<p>
This step depends on whether you are adding a simple or
complex character set. A simple character set requires only a
configuration file, whereas a complex character set requires C
source file that defines collation functions, multibyte
functions, or both.
</p>
<p>
For a simple character set, create a configuration file,
<code class="filename">
<em class="replaceable">
<code>
MYSET
</code>
</em>
.xml
</code>
,
that describes the character set properties. Create this file
in the
<code class="filename">
sql/share/charsets
</code>
directory. You
can use a copy of
<code class="filename">
latin1.xml
</code>
as the basis
for this file. The syntax for the file is very simple:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
Comments are written as ordinary XML comments
(
<code class="literal">
<!--
<em class="replaceable">
<code>
text
</code>
</em>
-->
</code>
).
</p>
</li>
<li class="listitem">
<p>
Words within
<code class="literal">
<map>
</code>
array elements
are separated by arbitrary amounts of whitespace.
</p>
</li>
<li class="listitem">
<p>
Each word within
<code class="literal">
<map>
</code>
array
elements must be a number in hexadecimal format.
</p>
</li>
<li class="listitem">
<p>
The
<code class="literal">
<map>
</code>
array element for the
<code class="literal">
<ctype>
</code>
element has 257 words.
The other
<code class="literal">
<map>
</code>
array elements
after that have 256 words. See
<a class="xref" href="character-arrays.html" title="12.13.1 Character Definition Arrays">
Section 12.13.1, “Character Definition Arrays”
</a>
.
</p>
</li>
<li class="listitem">
<p>
For each collation listed in the
<code class="literal">
<charset>
</code>
element for the
character set in
<code class="filename">
Index.xml
</code>
,
<code class="filename">
<em class="replaceable">
<code>
MYSET
</code>
</em>
.xml
</code>
must contain a
<code class="literal">
<collation>
</code>
element that defines the character ordering.
</p>
</li>
</ul>
</div>
<p>
For a complex character set, create a C source file that
describes the character set properties and defines the support
routines necessary to properly perform operations on the
character set:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
Create the file
<code class="filename">
ctype-
<em class="replaceable">
<code>
MYSET
</code>
</em>
.c
</code>
in the
<code class="filename">
strings
</code>
directory. Look at one
of the existing
<code class="filename">
ctype-*.c
</code>
files (such
as
<code class="filename">
ctype-big5.c
</code>
) to see what needs to
be defined. The arrays in your file must have names like
<code class="literal">
ctype_
<em class="replaceable">
<code>
MYSET
</code>
</em>
</code>
,
<code class="literal">
to_lower_
<em class="replaceable">
<code>
MYSET
</code>
</em>
</code>
,
and so on. These correspond to the arrays for a simple
character set. See
<a class="xref" href="character-arrays.html" title="12.13.1 Character Definition Arrays">
Section 12.13.1, “Character Definition Arrays”
</a>
.
</p>
</li>
<li class="listitem">
<p>
For each
<code class="literal">
<collation>
</code>
element
listed in the
<code class="literal">
<charset>
</code>
element
for the character set in
<code class="filename">
Index.xml
</code>
,
the
<code class="filename">
ctype-
<em class="replaceable">
<code>
MYSET
</code>
</em>
.c
</code>
file must provide an implementation of the collation.
</p>
</li>
<li class="listitem">
<p>
If the character set requires string collating functions,
see
<a class="xref" href="string-collating.html" title="12.13.2 String Collating Support for Complex Character Sets">
Section 12.13.2, “String Collating Support for Complex Character Sets”
</a>
.
</p>
</li>
<li class="listitem">
<p>
If the character set requires multibyte character support,
see
<a class="xref" href="multibyte-characters.html" title="12.13.3 Multi-Byte Character Support for Complex Character Sets">
Section 12.13.3, “Multi-Byte Character Support for Complex Character Sets”
</a>
.
</p>
</li>
</ul>
</div>
</li>
<li class="listitem">
<p>
Modify the configuration information. Use the existing
configuration information as a guide to adding information for
<em class="replaceable">
<code>
MYSYS
</code>
</em>
. The example here assumes
that the character set has default and binary collations, but
more lines are needed if
<em class="replaceable">
<code>
MYSET
</code>
</em>
has
additional collations.
</p>
<div class="orderedlist">
<ol class="orderedlist" type="a">
<li class="listitem">
<p>
Edit
<code class="filename">
mysys/charset-def.c
</code>
, and
<span class="quote">
“
<span class="quote">
register
</span>
”
</span>
the collations for the new
character set.
</p>
<p>
Add these lines to the
<span class="quote">
“
<span class="quote">
declaration
</span>
”
</span>
section:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-c"><div class="docs-select-all right" id="sa4645318"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-c"><span class="token macro property">#<span class="token directive keyword">ifdef</span> HAVE_CHARSET_<em class="replaceable">MYSET</em></span>
<span class="token keyword">extern</span> CHARSET_INFO my_charset_<em class="replaceable">MYSET</em>_general_ci<span class="token punctuation">;</span>
<span class="token keyword">extern</span> CHARSET_INFO my_charset_<em class="replaceable">MYSET</em>_bin<span class="token punctuation">;</span>
<span class="token macro property">#<span class="token directive keyword">endif</span></span></code></pre>
</div>
<p>
Add these lines to the
<span class="quote">
“
<span class="quote">
registration
</span>
”
</span>
section:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-c"><div class="docs-select-all right" id="sa15107332"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-c"><span class="token macro property">#<span class="token directive keyword">ifdef</span> HAVE_CHARSET_<em class="replaceable">MYSET</em></span>
<span class="token function">add_compiled_collation</span><span class="token punctuation">(</span><span class="token operator">&</span>my_charset_<em class="replaceable">MYSET</em>_general_ci<span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token function">add_compiled_collation</span><span class="token punctuation">(</span><span class="token operator">&</span>my_charset_<em class="replaceable">MYSET</em>_bin<span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token macro property">#<span class="token directive keyword">endif</span></span></code></pre>
</div>
</li>
<li class="listitem">
<p>
If the character set uses
<code class="filename">
ctype-
<em class="replaceable">
<code>
MYSET
</code>
</em>
.c
</code>
,
edit
<code class="filename">
strings/CMakeLists.txt
</code>
and add
<code class="filename">
ctype-
<em class="replaceable">
<code>
MYSET
</code>
</em>
.c
</code>
to the definition of the
<code class="literal">
STRINGS_SOURCES
</code>
variable.
</p>
</li>
<li class="listitem">
<p>
Edit
<code class="filename">
cmake/character_sets.cmake
</code>
:
</p>
<div class="orderedlist">
<ol class="orderedlist" type="i">
<li class="listitem">
<p>
Add
<em class="replaceable">
<code>
MYSET
</code>
</em>
to the value of
with
<code class="literal">
CHARSETS_AVAILABLE
</code>
in
alphabetic order.
</p>
</li>
<li class="listitem">
<p>
Add
<em class="replaceable">
<code>
MYSET
</code>
</em>
to the value of
<code class="literal">
CHARSETS_COMPLEX
</code>
in alphabetic
order. This is needed even for simple character sets,
so that
<span class="command">
<strong>
CMake
</strong>
</span>
can recognize
<a class="link" href="source-configuration-options.html#option_cmake_default_charset">
<code class="option">
-DDEFAULT_CHARSET=
<em class="replaceable">
<code>
MYSET
</code>
</em>
</code>
</a>
.
</p>
</li>
</ol>
</div>
</li>
</ol>
</div>
</li>
<li class="listitem">
<p>
Reconfigure, recompile, and test.
</p>
</li>
</ol>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/temporary-files.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="temporary-files">
</a>
B.3.3.5 Where MySQL Stores Temporary Files
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045053828176">
</a>
<a class="indexterm" name="idm46045053827136">
</a>
<a class="indexterm" name="idm46045053826048">
</a>
<p>
On Unix, MySQL uses the value of the
<code class="literal">
TMPDIR
</code>
environment variable as the path name of the directory in
which to store temporary files. If
<code class="literal">
TMPDIR
</code>
is not set, MySQL uses the system default, which is usually
<code class="filename">
/tmp
</code>
,
<code class="filename">
/var/tmp
</code>
, or
<code class="filename">
/usr/tmp
</code>
.
</p>
<p>
On Windows, MySQL checks in order the values of the
<code class="literal">
TMPDIR
</code>
,
<code class="literal">
TEMP
</code>
, and
<code class="literal">
TMP
</code>
environment variables. For the first
one found to be set, MySQL uses it and does not check those
remaining. If none of
<code class="literal">
TMPDIR
</code>
,
<code class="literal">
TEMP
</code>
, or
<code class="literal">
TMP
</code>
are set,
MySQL uses the Windows system default, which is usually
<code class="filename">
C:\windows\temp\
</code>
.
</p>
<p>
If the file system containing your temporary file directory is
too small, you can use the
<a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
<span class="command">
<strong>
mysqld
</strong>
</span>
</a>
<a class="link" href="server-options.html#option_mysqld_tmpdir">
<code class="option">
--tmpdir
</code>
</a>
option to specify a
directory in a file system where you have enough space.
</p>
<p>
The
<a class="link" href="server-options.html#option_mysqld_tmpdir">
<code class="option">
--tmpdir
</code>
</a>
option can be set
to a list of several paths that are used in round-robin
fashion. Paths should be separated by colon characters
(
<code class="literal">
:
</code>
) on Unix and semicolon characters
(
<code class="literal">
;
</code>
) on Windows.
</p>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
To spread the load effectively, these paths should be
located on different
<span class="emphasis">
<em>
physical
</em>
</span>
disks,
not different partitions of the same disk.
</p>
</div>
<p>
If the MySQL server is acting as a replica, you can set the
system variable
<a class="link" href="replication-options-replica.html#sysvar_replica_load_tmpdir">
<code class="literal">
replica_load_tmpdir
</code>
</a>
to
specify a separate directory for holding temporary files when
replicating
<a class="link" href="load-data.html" title="15.2.9 LOAD DATA Statement">
<code class="literal">
LOAD DATA
</code>
</a>
statements. This directory should be in a disk-based file
system (not a memory-based file system) so that the temporary
files used to replicate LOAD DATA can survive machine
restarts. The directory also should not be one that is cleared
by the operating system during the system startup process.
However, replication can now continue after a restart if the
temporary files have been removed.
</p>
<p>
MySQL arranges that temporary files are removed if
<a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
<span class="command">
<strong>
mysqld
</strong>
</span>
</a>
is terminated. On platforms that
support it (such as Unix), this is done by unlinking the file
after opening it. The disadvantage of this is that the name
does not appear in directory listings and you do not see a big
temporary file that fills up the file system in which the
temporary file directory is located. (In such cases,
<span class="command">
<strong>
lsof +L1
</strong>
</span>
may be helpful in identifying
large files associated with
<a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
<span class="command">
<strong>
mysqld
</strong>
</span>
</a>
.)
</p>
<p>
When sorting (
<code class="literal">
ORDER BY
</code>
or
<code class="literal">
GROUP
BY
</code>
), MySQL normally uses one or two temporary files.
The maximum disk space required is determined by the following
expression:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-clike"><div class="docs-select-all right" id="sa92844125"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-clike"><span class="token punctuation">(</span>length of what is sorted <span class="token operator">+</span> <span class="token function">sizeof</span><span class="token punctuation">(</span>row pointer<span class="token punctuation">)</span><span class="token punctuation">)</span>
<span class="token operator">*</span> number of matched rows
<span class="token operator">*</span> <span class="token number">2</span></code></pre>
</div>
<p>
The row pointer size is usually four bytes, but may grow in
the future for really big tables.
</p>
<p>
For some statements, MySQL creates temporary SQL tables that
are not hidden and have names that begin with
<code class="filename">
#sql
</code>
.
</p>
<p>
Some
<a class="link" href="select.html" title="15.2.13 SELECT Statement">
<code class="literal">
SELECT
</code>
</a>
queries creates
temporary SQL tables to hold intermediate results.
</p>
<p>
DDL operations that rebuild the table and are not performed
online using the
<code class="literal">
ALGORITHM=INPLACE
</code>
technique create a temporary copy of the original table in the
same directory as the original table.
</p>
<p>
Online DDL operations may use temporary log files for
recording concurrent DML, temporary sort files when creating
an index, and temporary intermediate tables files when
rebuilding the table. For more information, see
<a class="xref" href="innodb-online-ddl-space-requirements.html" title="17.12.3 Online DDL Space Requirements">
Section 17.12.3, “Online DDL Space Requirements”
</a>
.
</p>
<p>
<code class="literal">
InnoDB
</code>
user-created temporary tables and
on-disk internal temporary tables are created in a temporary
tablespace file named
<code class="filename">
ibtmp1
</code>
in the MySQL
data directory. For more information, see
<a class="xref" href="innodb-temporary-tablespace.html" title="17.6.3.5 Temporary Tablespaces">
Section 17.6.3.5, “Temporary Tablespaces”
</a>
.
</p>
<p>
See also
<a class="xref" href="innodb-information-schema-temp-table-info.html" title="17.15.7 InnoDB INFORMATION_SCHEMA Temporary Table Info Table">
Section 17.15.7, “InnoDB INFORMATION_SCHEMA Temporary Table Info Table”
</a>
.
</p>
<p>
The optional
<code class="literal">
EXTENDED
</code>
modifier causes
<a class="link" href="show-tables.html" title="15.7.7.39 SHOW TABLES Statement">
<code class="literal">
SHOW TABLES
</code>
</a>
to list hidden
tables created by failed
<a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement">
<code class="literal">
ALTER
TABLE
</code>
</a>
statements. See
<a class="xref" href="show-tables.html" title="15.7.7.39 SHOW TABLES Statement">
Section 15.7.7.39, “SHOW TABLES Statement”
</a>
.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/sys-ps-trace-thread.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="sys-ps-trace-thread">
</a>
30.4.4.23 The ps_trace_thread() Procedure
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045061257456">
</a>
<a class="indexterm" name="idm46045061255984">
</a>
<p>
Dumps all Performance Schema data for an instrumented thread
to a
<code class="filename">
.dot
</code>
formatted graph file (for the
DOT graph description language). Each result set returned from
the procedure should be used for a complete graph.
</p>
<p>
This procedure disables binary logging during its execution by
manipulating the session value of the
<a class="link" href="replication-options-binary-log.html#sysvar_sql_log_bin">
<code class="literal">
sql_log_bin
</code>
</a>
system variable.
That is a restricted operation, so the procedure requires
privileges sufficient to set restricted session variables. See
<a class="xref" href="system-variable-privileges.html" title="7.1.9.1 System Variable Privileges">
Section 7.1.9.1, “System Variable Privileges”
</a>
.
</p>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h5 class="title">
<a name="sys-ps-trace-thread-parameters">
</a>
Parameters
</h5>
</div>
</div>
</div>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<code class="literal">
in_thread_id INT
</code>
: The thread to
trace.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
in_outfile VARCHAR(255)
</code>
: The name to
use for the
<code class="filename">
.dot
</code>
output file.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
in_max_runtime DECIMAL(20,2)
</code>
: The
maximum number of seconds (which can be fractional) to
collect data. Use
<code class="literal">
NULL
</code>
to collect
data for the default of 60 seconds.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
in_interval DECIMAL(20,2)
</code>
: The number
of seconds (which can be fractional) to sleep between
data collections. Use
<code class="literal">
NULL
</code>
to sleep
for the default of 1 second.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
in_start_fresh BOOLEAN
</code>
: Whether to
reset all Performance Schema data before tracing.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
in_auto_setup BOOLEAN
</code>
: Whether to
disable all other threads and enable all instruments and
consumers. This also resets the settings at the end of
the run.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
in_debug BOOLEAN
</code>
: Whether to include
<code class="literal">
file:lineno
</code>
information in the graph.
</p>
</li>
</ul>
</div>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h5 class="title">
<a name="sys-ps-trace-thread-example">
</a>
Example
</h5>
</div>
</div>
</div>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa9427587"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">CALL</span> sys<span class="token punctuation">.</span>ps_trace_thread<span class="token punctuation">(</span><span class="token number">25</span><span class="token punctuation">,</span> <span class="token function">CONCAT</span><span class="token punctuation">(</span><span class="token string">'/tmp/stack-'</span><span class="token punctuation">,</span> <span class="token function">REPLACE</span><span class="token punctuation">(</span><span class="token function">NOW</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token string">' '</span><span class="token punctuation">,</span> <span class="token string">'-'</span><span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token string">'.dot'</span><span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token boolean">NULL</span><span class="token punctuation">,</span> <span class="token boolean">NULL</span><span class="token punctuation">,</span> <span class="token boolean">TRUE</span><span class="token punctuation">,</span> <span class="token boolean">TRUE</span><span class="token punctuation">,</span> <span class="token boolean">TRUE</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> summary <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> Disabled 1 thread <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output">1 row in set (0.00 sec)</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> Info <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> Data collection starting for THREAD_ID = 25 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output">1 row in set (0.03 sec)</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> Info <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> Stack trace written to /tmp/stack<span class="token punctuation">-</span>2014<span class="token punctuation">-</span>02<span class="token punctuation">-</span>16<span class="token punctuation">-</span>21:18:41.dot <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output">1 row in set (60.07 sec)</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> Convert to PDF <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> dot <span class="token punctuation">-</span>Tpdf <span class="token punctuation">-</span>o /tmp/stack_25.pdf /tmp/stack<span class="token punctuation">-</span>2014<span class="token punctuation">-</span>02<span class="token punctuation">-</span>16<span class="token punctuation">-</span>21:18:41.dot <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output">1 row in set (60.07 sec)</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> Convert to PNG <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> dot <span class="token punctuation">-</span>Tpng <span class="token punctuation">-</span>o /tmp/stack_25.png /tmp/stack<span class="token punctuation">-</span>2014<span class="token punctuation">-</span>02<span class="token punctuation">-</span>16<span class="token punctuation">-</span>21:18:41.dot <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output">1 row in set (60.07 sec)</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> summary <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> Enabled 1 thread <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output">1 row in set (60.32 sec)</span></code></pre>
</div>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/innodb-compression-internals.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="innodb-compression-internals">
</a>
17.9.1.5 How Compression Works for InnoDB Tables
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045161484112">
</a>
<p>
This section describes some internal implementation details
about
<a class="link" href="glossary.html#glos_compression" title="compression">
compression
</a>
for
InnoDB tables. The information presented here may be helpful in
tuning for performance, but is not necessary to know for basic
use of compression.
</p>
<h5>
<a name="innodb-compression-internals-algorithms">
</a>
Compression Algorithms
</h5>
<a class="indexterm" name="idm46045161479904">
</a>
<p>
Some operating systems implement compression at the file system
level. Files are typically divided into fixed-size blocks that
are compressed into variable-size blocks, which easily leads
into fragmentation. Every time something inside a block is
modified, the whole block is recompressed before it is written
to disk. These properties make this compression technique
unsuitable for use in an update-intensive database system.
</p>
<p>
MySQL implements compression with the help of the well-known
<a class="ulink" href="http://www.zlib.net/" target="_blank">
zlib library
</a>
, which
implements the LZ77 compression algorithm. This compression
algorithm is mature, robust, and efficient in both CPU
utilization and in reduction of data size. The algorithm is
<span class="quote">
“
<span class="quote">
lossless
</span>
”
</span>
, so that the original uncompressed data
can always be reconstructed from the compressed form. LZ77
compression works by finding sequences of data that are repeated
within the data to be compressed. The patterns of values in your
data determine how well it compresses, but typical user data
often compresses by 50% or more.
</p>
<p>
Unlike compression performed by an application, or compression
features of some other database management systems, InnoDB
compression applies both to user data and to indexes. In many
cases, indexes can constitute 40-50% or more of the total
database size, so this difference is significant. When
compression is working well for a data set, the size of the
InnoDB data files (the
<a class="link" href="glossary.html#glos_file_per_table" title="file-per-table">
file-per-table
</a>
tablespace or
<a class="link" href="glossary.html#glos_general_tablespace" title="general tablespace">
general
tablespace
</a>
<code class="literal">
.ibd
</code>
files) is 25% to 50%
of the uncompressed size or possibly smaller. Depending on the
<a class="link" href="glossary.html#glos_workload" title="workload">
workload
</a>
, this smaller
database can in turn lead to a reduction in I/O, and an increase
in throughput, at a modest cost in terms of increased CPU
utilization. You can adjust the balance between compression
level and CPU overhead by modifying the
<a class="link" href="innodb-parameters.html#sysvar_innodb_compression_level">
<code class="literal">
innodb_compression_level
</code>
</a>
configuration option.
</p>
<h5>
<a name="innodb-compression-internals-storage">
</a>
InnoDB Data Storage and Compression
</h5>
<a class="indexterm" name="idm46045161468512">
</a>
<p>
All user data in InnoDB tables is stored in pages comprising a
<a class="link" href="glossary.html#glos_b_tree" title="B-tree">
B-tree
</a>
index (the
<a class="link" href="glossary.html#glos_clustered_index" title="clustered index">
clustered index
</a>
). In
some other database systems, this type of index is called an
<span class="quote">
“
<span class="quote">
index-organized table
</span>
”
</span>
. Each row in the index node
contains the values of the (user-specified or system-generated)
<a class="link" href="glossary.html#glos_primary_key" title="primary key">
primary key
</a>
and all the
other columns of the table.
</p>
<p>
<a class="link" href="glossary.html#glos_secondary_index" title="secondary index">
Secondary indexes
</a>
in
InnoDB tables are also B-trees, containing pairs of values: the
index key and a pointer to a row in the clustered index. The
pointer is in fact the value of the primary key of the table,
which is used to access the clustered index if columns other
than the index key and primary key are required. Secondary index
records must always fit on a single B-tree page.
</p>
<p>
The compression of B-tree nodes (of both clustered and secondary
indexes) is handled differently from compression of
<a class="link" href="glossary.html#glos_overflow_page" title="overflow page">
overflow pages
</a>
used to
store long
<code class="literal">
VARCHAR
</code>
,
<code class="literal">
BLOB
</code>
,
or
<code class="literal">
TEXT
</code>
columns, as explained in the
following sections.
</p>
<h5>
<a name="innodb-compression-internals-storage-btree">
</a>
Compression of B-Tree Pages
</h5>
<a class="indexterm" name="idm46045161457008">
</a>
<p>
Because they are frequently updated, B-tree pages require
special treatment. It is important to minimize the number of
times B-tree nodes are split, as well as to minimize the need to
uncompress and recompress their content.
</p>
<p>
One technique MySQL uses is to maintain some system information
in the B-tree node in uncompressed form, thus facilitating
certain in-place updates. For example, this allows rows to be
delete-marked and deleted without any compression operation.
</p>
<p>
In addition, MySQL attempts to avoid unnecessary uncompression
and recompression of index pages when they are changed. Within
each B-tree page, the system keeps an uncompressed
<span class="quote">
“
<span class="quote">
modification log
</span>
”
</span>
to record changes made to the
page. Updates and inserts of small records may be written to
this modification log without requiring the entire page to be
completely reconstructed.
</p>
<p>
When the space for the modification log runs out, InnoDB
uncompresses the page, applies the changes and recompresses the
page. If recompression fails (a situation known as a
<a class="link" href="glossary.html#glos_compression_failure" title="compression failure">
compression
failure
</a>
), the B-tree nodes are split and the process is
repeated until the update or insert succeeds.
</p>
<p>
To avoid frequent compression failures in write-intensive
workloads, such as for
<a class="link" href="glossary.html#glos_oltp" title="OLTP">
OLTP
</a>
applications, MySQL sometimes reserves some empty space
(padding) in the page, so that the modification log fills up
sooner and the page is recompressed while there is still enough
room to avoid splitting it. The amount of padding space left in
each page varies as the system keeps track of the frequency of
page splits. On a busy server doing frequent writes to
compressed tables, you can adjust the
<a class="link" href="innodb-parameters.html#sysvar_innodb_compression_failure_threshold_pct">
<code class="literal">
innodb_compression_failure_threshold_pct
</code>
</a>
,
and
<a class="link" href="innodb-parameters.html#sysvar_innodb_compression_pad_pct_max">
<code class="literal">
innodb_compression_pad_pct_max
</code>
</a>
configuration options to fine-tune this mechanism.
</p>
<p>
Generally, MySQL requires that each B-tree page in an InnoDB
table can accommodate at least two records. For compressed
tables, this requirement has been relaxed. Leaf pages of B-tree
nodes (whether of the primary key or secondary indexes) only
need to accommodate one record, but that record must fit, in
uncompressed form, in the per-page modification log. If
<a class="link" href="innodb-parameters.html#sysvar_innodb_strict_mode">
<code class="literal">
innodb_strict_mode
</code>
</a>
is
<code class="literal">
ON
</code>
, MySQL checks the maximum row size during
<a class="link" href="create-table.html" title="15.1.20 CREATE TABLE Statement">
<code class="literal">
CREATE TABLE
</code>
</a>
or
<a class="link" href="create-index.html" title="15.1.15 CREATE INDEX Statement">
<code class="literal">
CREATE INDEX
</code>
</a>
. If the row does not
fit, the following error message is issued:
<code class="literal">
ERROR
HY000: Too big row
</code>
.
</p>
<p>
If you create a table when
<a class="link" href="innodb-parameters.html#sysvar_innodb_strict_mode">
<code class="literal">
innodb_strict_mode
</code>
</a>
is OFF, and
a subsequent
<code class="literal">
INSERT
</code>
or
<code class="literal">
UPDATE
</code>
statement attempts to create an index
entry that does not fit in the size of the compressed page, the
operation fails with
<code class="literal">
ERROR 42000: Row size too
large
</code>
. (This error message does not name the index for
which the record is too large, or mention the length of the
index record or the maximum record size on that particular index
page.) To solve this problem, rebuild the table with
<a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement">
<code class="literal">
ALTER TABLE
</code>
</a>
and select a larger
compressed page size (
<code class="literal">
KEY_BLOCK_SIZE
</code>
),
shorten any column prefix indexes, or disable compression
entirely with
<code class="literal">
ROW_FORMAT=DYNAMIC
</code>
or
<code class="literal">
ROW_FORMAT=COMPACT
</code>
.
</p>
<p>
<a class="link" href="innodb-parameters.html#sysvar_innodb_strict_mode">
<code class="literal">
innodb_strict_mode
</code>
</a>
is not
applicable to general tablespaces, which also support compressed
tables. Tablespace management rules for general tablespaces are
strictly enforced independently of
<a class="link" href="innodb-parameters.html#sysvar_innodb_strict_mode">
<code class="literal">
innodb_strict_mode
</code>
</a>
. For more
information, see
<a class="xref" href="create-tablespace.html" title="15.1.21 CREATE TABLESPACE Statement">
Section 15.1.21, “CREATE TABLESPACE Statement”
</a>
.
</p>
<h5>
<a name="innodb-compression-internals-storage-blobs">
</a>
Compressing BLOB, VARCHAR, and TEXT Columns
</h5>
<a class="indexterm" name="idm46045161428032">
</a>
<a class="indexterm" name="idm46045161426544">
</a>
<p>
In an InnoDB table,
<a class="link" href="blob.html" title="13.3.4 The BLOB and TEXT Types">
<code class="literal">
BLOB
</code>
</a>
,
<a class="link" href="char.html" title="13.3.2 The CHAR and VARCHAR Types">
<code class="literal">
VARCHAR
</code>
</a>
, and
<a class="link" href="blob.html" title="13.3.4 The BLOB and TEXT Types">
<code class="literal">
TEXT
</code>
</a>
columns that are not part of
the primary key may be stored on separately allocated
<a class="link" href="glossary.html#glos_overflow_page" title="overflow page">
overflow pages
</a>
. We
refer to these columns as
<a class="link" href="glossary.html#glos_off_page_column" title="off-page column">
off-page columns
</a>
.
Their values are stored on singly-linked lists of overflow
pages.
</p>
<p>
For tables created in
<code class="literal">
ROW_FORMAT=DYNAMIC
</code>
or
<code class="literal">
ROW_FORMAT=COMPRESSED
</code>
, the values of
<a class="link" href="blob.html" title="13.3.4 The BLOB and TEXT Types">
<code class="literal">
BLOB
</code>
</a>
,
<a class="link" href="blob.html" title="13.3.4 The BLOB and TEXT Types">
<code class="literal">
TEXT
</code>
</a>
, or
<a class="link" href="char.html" title="13.3.2 The CHAR and VARCHAR Types">
<code class="literal">
VARCHAR
</code>
</a>
columns may be stored
fully off-page, depending on their length and the length of the
entire row. For columns that are stored off-page, the clustered
index record only contains 20-byte pointers to the overflow
pages, one per column. Whether any columns are stored off-page
depends on the page size and the total size of the row. When the
row is too long to fit entirely within the page of the clustered
index, MySQL chooses the longest columns for off-page storage
until the row fits on the clustered index page. As noted above,
if a row does not fit by itself on a compressed page, an error
occurs.
</p>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
For tables created in
<code class="literal">
ROW_FORMAT=DYNAMIC
</code>
or
<code class="literal">
ROW_FORMAT=COMPRESSED
</code>
,
<a class="link" href="blob.html" title="13.3.4 The BLOB and TEXT Types">
<code class="literal">
TEXT
</code>
</a>
and
<a class="link" href="blob.html" title="13.3.4 The BLOB and TEXT Types">
<code class="literal">
BLOB
</code>
</a>
columns that are less than
or equal to 40 bytes are always stored in-line.
</p>
</div>
<p>
Tables that use
<code class="literal">
ROW_FORMAT=REDUNDANT
</code>
and
<code class="literal">
ROW_FORMAT=COMPACT
</code>
store the first 768 bytes
of
<a class="link" href="blob.html" title="13.3.4 The BLOB and TEXT Types">
<code class="literal">
BLOB
</code>
</a>
,
<a class="link" href="char.html" title="13.3.2 The CHAR and VARCHAR Types">
<code class="literal">
VARCHAR
</code>
</a>
, and
<a class="link" href="blob.html" title="13.3.4 The BLOB and TEXT Types">
<code class="literal">
TEXT
</code>
</a>
columns in the clustered
index record along with the primary key. The 768-byte prefix is
followed by a 20-byte pointer to the overflow pages that contain
the rest of the column value.
</p>
<p>
When a table is in
<code class="literal">
COMPRESSED
</code>
format, all
data written to overflow pages is compressed
<span class="quote">
“
<span class="quote">
as
is
</span>
”
</span>
; that is, MySQL applies the zlib compression
algorithm to the entire data item. Other than the data,
compressed overflow pages contain an uncompressed header and
trailer comprising a page checksum and a link to the next
overflow page, among other things. Therefore, very significant
storage savings can be obtained for longer
<code class="literal">
BLOB
</code>
,
<code class="literal">
TEXT
</code>
, or
<code class="literal">
VARCHAR
</code>
columns if the data is highly
compressible, as is often the case with text data. Image data,
such as
<code class="literal">
JPEG
</code>
, is typically already compressed
and so does not benefit much from being stored in a compressed
table; the double compression can waste CPU cycles for little or
no space savings.
</p>
<p>
The overflow pages are of the same size as other pages. A row
containing ten columns stored off-page occupies ten overflow
pages, even if the total length of the columns is only 8K bytes.
In an uncompressed table, ten uncompressed overflow pages occupy
160K bytes. In a compressed table with an 8K page size, they
occupy only 80K bytes. Thus, it is often more efficient to use
compressed table format for tables with long column values.
</p>
<p>
For
<a class="link" href="glossary.html#glos_file_per_table" title="file-per-table">
file-per-table
</a>
tablespaces, using a 16K compressed page size can reduce storage
and I/O costs for
<a class="link" href="blob.html" title="13.3.4 The BLOB and TEXT Types">
<code class="literal">
BLOB
</code>
</a>
,
<a class="link" href="char.html" title="13.3.2 The CHAR and VARCHAR Types">
<code class="literal">
VARCHAR
</code>
</a>
, or
<a class="link" href="blob.html" title="13.3.4 The BLOB and TEXT Types">
<code class="literal">
TEXT
</code>
</a>
columns, because such data
often compress well, and might therefore require fewer overflow
pages, even though the B-tree nodes themselves take as many
pages as in the uncompressed form. General tablespaces do not
support a 16K compressed page size
(
<code class="literal">
KEY_BLOCK_SIZE
</code>
). For more information, see
<a class="xref" href="general-tablespaces.html" title="17.6.3.3 General Tablespaces">
Section 17.6.3.3, “General Tablespaces”
</a>
.
</p>
<h5>
<a name="innodb-compression-internals-pool">
</a>
Compression and the InnoDB Buffer Pool
</h5>
<a class="indexterm" name="idm46045161388160">
</a>
<a class="indexterm" name="idm46045161386656">
</a>
<p>
In a compressed
<code class="literal">
InnoDB
</code>
table, every
compressed page (whether 1K, 2K, 4K or 8K) corresponds to an
uncompressed page of 16K bytes (or a smaller size if
<a class="link" href="innodb-parameters.html#sysvar_innodb_page_size">
<code class="literal">
innodb_page_size
</code>
</a>
is set). To
access the data in a page, MySQL reads the compressed page from
disk if it is not already in the
<a class="link" href="glossary.html#glos_buffer_pool" title="buffer pool">
buffer pool
</a>
, then
uncompresses the page to its original form. This section
describes how
<code class="literal">
InnoDB
</code>
manages the buffer pool
with respect to pages of compressed tables.
</p>
<p>
To minimize I/O and to reduce the need to uncompress a page, at
times the buffer pool contains both the compressed and
uncompressed form of a database page. To make room for other
required database pages, MySQL can
<a class="link" href="glossary.html#glos_eviction" title="eviction">
evict
</a>
from the buffer pool
an uncompressed page, while leaving the compressed page in
memory. Or, if a page has not been accessed in a while, the
compressed form of the page might be written to disk, to free
space for other data. Thus, at any given time, the buffer pool
might contain both the compressed and uncompressed forms of the
page, or only the compressed form of the page, or neither.
</p>
<p>
MySQL keeps track of which pages to keep in memory and which to
evict using a least-recently-used
(
<a class="link" href="glossary.html#glos_lru" title="LRU">
LRU
</a>
) list, so that
<a class="link" href="glossary.html#glos_hot" title="hot">
hot
</a>
(frequently accessed) data
tends to stay in memory. When compressed tables are accessed,
MySQL uses an adaptive LRU algorithm to achieve an appropriate
balance of compressed and uncompressed pages in memory. This
adaptive algorithm is sensitive to whether the system is running
in an
<a class="link" href="glossary.html#glos_io_bound" title="I/O-bound">
I/O-bound
</a>
or
<a class="link" href="glossary.html#glos_cpu_bound" title="CPU-bound">
CPU-bound
</a>
manner. The goal
is to avoid spending too much processing time uncompressing
pages when the CPU is busy, and to avoid doing excess I/O when
the CPU has spare cycles that can be used for uncompressing
compressed pages (that may already be in memory). When the
system is I/O-bound, the algorithm prefers to evict the
uncompressed copy of a page rather than both copies, to make
more room for other disk pages to become memory resident. When
the system is CPU-bound, MySQL prefers to evict both the
compressed and uncompressed page, so that more memory can be
used for
<span class="quote">
“
<span class="quote">
hot
</span>
”
</span>
pages and reducing the need to
uncompress data in memory only in compressed form.
</p>
<h5>
<a name="innodb-compression-internals-log">
</a>
Compression and the InnoDB Redo Log Files
</h5>
<a class="indexterm" name="idm46045161372080">
</a>
<p>
Before a compressed page is written to a
<a class="link" href="glossary.html#glos_data_files" title="data files">
data file
</a>
, MySQL writes a
copy of the page to the redo log (if it has been recompressed
since the last time it was written to the database). This is
done to ensure that redo logs are usable for
<a class="link" href="glossary.html#glos_crash_recovery" title="crash recovery">
crash recovery
</a>
, even
in the unlikely case that the
<code class="literal">
zlib
</code>
library is
upgraded and that change introduces a compatibility problem with
the compressed data. Therefore, some increase in the size of
<a class="link" href="glossary.html#glos_log_file" title="log file">
log files
</a>
, or a need for
more frequent
<a class="link" href="glossary.html#glos_checkpoint" title="checkpoint">
checkpoints
</a>
, can be
expected when using compression. The amount of increase in the
log file size or checkpoint frequency depends on the number of
times compressed pages are modified in a way that requires
reorganization and recompression.
</p>
<p>
To create a compressed table in a file-per-table tablespace,
<a class="link" href="innodb-parameters.html#sysvar_innodb_file_per_table">
<code class="literal">
innodb_file_per_table
</code>
</a>
must be
enabled. There is no dependence on the
<a class="link" href="innodb-parameters.html#sysvar_innodb_file_per_table">
<code class="literal">
innodb_file_per_table
</code>
</a>
setting
when creating a compressed table in a general tablespace. For
more information, see
<a class="xref" href="general-tablespaces.html" title="17.6.3.3 General Tablespaces">
Section 17.6.3.3, “General Tablespaces”
</a>
.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/c-api-info.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h2 class="title">
<a name="c-api-info">
</a>
31.7 MySQL C API
</h2>
</div>
</div>
</div>
<a class="indexterm" name="idm46045060349904">
</a>
<a class="indexterm" name="idm46045060348864">
</a>
<p>
The MySQL C API Developer Guide is published in standalone form, not
as part of the MySQL Reference Manual. See
<a class="ulink" href="/doc/c-api/8.4/en/" target="_top">
MySQL 8.4 C API Developer Guide
</a>
.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/sys-ps-trace-statement-digest.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="sys-ps-trace-statement-digest">
</a>
30.4.4.22 The ps_trace_statement_digest() Procedure
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045061293392">
</a>
<a class="indexterm" name="idm46045061291936">
</a>
<p>
Traces all Performance Schema instrumentation for a specific
statement digest.
</p>
<p>
If you find a statement of interest within the Performance
Schema
<a class="link" href="performance-schema-statement-summary-tables.html" title="29.12.20.3 Statement Summary Tables">
<code class="literal">
events_statements_summary_by_digest
</code>
</a>
table, specify its
<code class="literal">
DIGEST
</code>
column MD5 value
to this procedure and indicate the polling duration and
interval. The result is a report of all statistics tracked
within Performance Schema for that digest for the interval.
</p>
<p>
The procedure also attempts to execute
<a class="link" href="explain.html" title="15.8.2 EXPLAIN Statement">
<code class="literal">
EXPLAIN
</code>
</a>
for the longest running
example of the digest during the interval. This attempt might
fail because the Performance Schema truncates long
<code class="literal">
SQL_TEXT
</code>
values. Consequently,
<a class="link" href="explain.html" title="15.8.2 EXPLAIN Statement">
<code class="literal">
EXPLAIN
</code>
</a>
fails, due to parse
errors.
</p>
<p>
This procedure disables binary logging during its execution by
manipulating the session value of the
<a class="link" href="replication-options-binary-log.html#sysvar_sql_log_bin">
<code class="literal">
sql_log_bin
</code>
</a>
system variable.
That is a restricted operation, so the procedure requires
privileges sufficient to set restricted session variables. See
<a class="xref" href="system-variable-privileges.html" title="7.1.9.1 System Variable Privileges">
Section 7.1.9.1, “System Variable Privileges”
</a>
.
</p>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h5 class="title">
<a name="sys-ps-trace-statement-digest-parameters">
</a>
Parameters
</h5>
</div>
</div>
</div>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<code class="literal">
in_digest VARCHAR(32)
</code>
: The statement
digest identifier to analyze.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
in_runtime INT
</code>
: How long to run the
analysis in seconds.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
in_interval DECIMAL(2,2)
</code>
: The
analysis interval in seconds (which can be fractional)
at which to try to take snapshots.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
in_start_fresh BOOLEAN
</code>
: Whether to
truncate the Performance Schema
<a class="link" href="performance-schema-events-statements-history-long-table.html" title="29.12.6.3 The events_statements_history_long Table">
<code class="literal">
events_statements_history_long
</code>
</a>
and
<a class="link" href="performance-schema-events-stages-history-long-table.html" title="29.12.5.3 The events_stages_history_long Table">
<code class="literal">
events_stages_history_long
</code>
</a>
tables before starting.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
in_auto_enable BOOLEAN
</code>
: Whether to
automatically enable required consumers.
</p>
</li>
</ul>
</div>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h5 class="title">
<a name="sys-ps-trace-statement-digest-example">
</a>
Example
</h5>
</div>
</div>
</div>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa45426047"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">CALL</span> sys<span class="token punctuation">.</span>ps_trace_statement_digest<span class="token punctuation">(</span><span class="token string">'891ec6860f98ba46d89dd20b0c03652c'</span><span class="token punctuation">,</span> <span class="token number">10</span><span class="token punctuation">,</span> <span class="token number">0.1</span><span class="token punctuation">,</span> <span class="token boolean">TRUE</span><span class="token punctuation">,</span> <span class="token boolean">TRUE</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> SUMMARY STATISTICS <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> SUMMARY STATISTICS <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output">1 row in set (9.11 sec)</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> executions <span class="token punctuation">|</span> exec_time <span class="token punctuation">|</span> lock_time <span class="token punctuation">|</span> rows_sent <span class="token punctuation">|</span> rows_examined <span class="token punctuation">|</span> tmp_tables <span class="token punctuation">|</span> full_scans <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 21 <span class="token punctuation">|</span> 4.11 ms <span class="token punctuation">|</span> 2.00 ms <span class="token punctuation">|</span> 0 <span class="token punctuation">|</span> 21 <span class="token punctuation">|</span> 0 <span class="token punctuation">|</span> 0 <span class="token punctuation">|</span></span>
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<span class="token output">1 row in set (9.11 sec)</span>
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<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
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<span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span>
<span class="token output"><span class="token punctuation">|</span> stage/sql/cleaning up <span class="token punctuation">|</span> 18 <span class="token punctuation">|</span> 11.92 us <span class="token punctuation">|</span></span>
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<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output">17 rows in set (9.12 sec)</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> LONGEST RUNNING STATEMENT <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> LONGEST RUNNING STATEMENT <span class="token punctuation">|</span></span>
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<span class="token output">1 row in set (9.16 sec)</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> thread_id <span class="token punctuation">|</span> exec_time <span class="token punctuation">|</span> lock_time <span class="token punctuation">|</span> rows_sent <span class="token punctuation">|</span> rows_examined <span class="token punctuation">|</span> tmp_tables <span class="token punctuation">|</span> full_scan <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
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<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output">1 row in set (9.16 sec)</span>
<span class="token comment" spellcheck="true"># Truncated for clarity...</span>
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<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
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<span class="token output">1 row in set (9.17 sec)</span>
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<span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span>
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<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output">18 rows in set (9.23 sec)</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> id <span class="token punctuation">|</span> select_type <span class="token punctuation">|</span> table <span class="token punctuation">|</span> type <span class="token punctuation">|</span> possible_keys <span class="token punctuation">|</span> key <span class="token punctuation">|</span> key_len <span class="token punctuation">|</span> ref <span class="token punctuation">|</span> rows <span class="token punctuation">|</span> Extra <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 1 <span class="token punctuation">|</span> SIMPLE <span class="token punctuation">|</span> hibeventhe0_ <span class="token punctuation">|</span> const <span class="token punctuation">|</span> fixedTime <span class="token punctuation">|</span> fixedTime <span class="token punctuation">|</span> 775 <span class="token punctuation">|</span> const,const <span class="token punctuation">|</span> 1 <span class="token punctuation">|</span> NULL <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output">1 row in set (9.27 sec)</span>
<span class="token output">Query OK, 0 rows affected (9.28 sec)</span></code></pre>
</div>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/performance-schema-summary-tables.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="performance-schema-summary-tables">
</a>
29.12.20 Performance Schema Summary Tables
</h3>
</div>
</div>
</div>
<div class="toc">
<dl class="toc">
<dt>
<span class="section">
<a href="performance-schema-wait-summary-tables.html">
29.12.20.1 Wait Event Summary Tables
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="performance-schema-stage-summary-tables.html">
29.12.20.2 Stage Summary Tables
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="performance-schema-statement-summary-tables.html">
29.12.20.3 Statement Summary Tables
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="performance-schema-statement-histogram-summary-tables.html">
29.12.20.4 Statement Histogram Summary Tables
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="performance-schema-transaction-summary-tables.html">
29.12.20.5 Transaction Summary Tables
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="performance-schema-objects-summary-global-by-type-table.html">
29.12.20.6 Object Wait Summary Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="performance-schema-file-summary-tables.html">
29.12.20.7 File I/O Summary Tables
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="performance-schema-table-wait-summary-tables.html">
29.12.20.8 Table I/O and Lock Wait Summary Tables
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="performance-schema-socket-summary-tables.html">
29.12.20.9 Socket Summary Tables
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="performance-schema-memory-summary-tables.html">
29.12.20.10 Memory Summary Tables
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="performance-schema-error-summary-tables.html">
29.12.20.11 Error Summary Tables
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="performance-schema-status-variable-summary-tables.html">
29.12.20.12 Status Variable Summary Tables
</a>
</span>
</dt>
</dl>
</div>
<p>
Summary tables provide aggregated information for terminated
events over time. The tables in this group summarize event data
in different ways.
</p>
<p>
Each summary table has grouping columns that determine how to
group the data to be aggregated, and summary columns that
contain the aggregated values. Tables that summarize events in
similar ways often have similar sets of summary columns and
differ only in the grouping columns used to determine how events
are aggregated.
</p>
<p>
Summary tables can be truncated with
<a class="link" href="truncate-table.html" title="15.1.37 TRUNCATE TABLE Statement">
<code class="literal">
TRUNCATE TABLE
</code>
</a>
. Generally, the
effect is to reset the summary columns to 0 or
<code class="literal">
NULL
</code>
, not to remove rows. This enables you to
clear collected values and restart aggregation. That might be
useful, for example, after you have made a runtime configuration
change. Exceptions to this truncation behavior are noted in
individual summary table sections.
</p>
<h4>
<a name="idm46045069365072">
</a>
Wait Event Summaries
</h4>
<div class="table">
<a name="idm46045069364384">
</a>
<p class="title">
<b>
Table 29.5 Performance Schema Wait Event Summary
Tables
</b>
</p>
<div class="table-contents">
<table frame="box" rules="all" summary="A reference that lists all Performance Schema wait event summary tables.">
<colgroup>
<col style="width: 28%"/>
<col style="width: 71%"/>
</colgroup>
<thead>
<tr>
<th>
Table Name
</th>
<th>
Description
</th>
</tr>
</thead>
<tbody>
<tr>
<td>
<a class="link" href="performance-schema-wait-summary-tables.html" title="29.12.20.1 Wait Event Summary Tables">
<code class="literal">
events_waits_summary_by_account_by_event_name
</code>
</a>
</td>
<td>
Wait events per account and event name
</td>
</tr>
<tr>
<td>
<a class="link" href="performance-schema-wait-summary-tables.html" title="29.12.20.1 Wait Event Summary Tables">
<code class="literal">
events_waits_summary_by_host_by_event_name
</code>
</a>
</td>
<td>
Wait events per host name and event name
</td>
</tr>
<tr>
<td>
<a class="link" href="performance-schema-wait-summary-tables.html" title="29.12.20.1 Wait Event Summary Tables">
<code class="literal">
events_waits_summary_by_instance
</code>
</a>
</td>
<td>
Wait events per instance
</td>
</tr>
<tr>
<td>
<a class="link" href="performance-schema-wait-summary-tables.html" title="29.12.20.1 Wait Event Summary Tables">
<code class="literal">
events_waits_summary_by_thread_by_event_name
</code>
</a>
</td>
<td>
Wait events per thread and event name
</td>
</tr>
<tr>
<td>
<a class="link" href="performance-schema-wait-summary-tables.html" title="29.12.20.1 Wait Event Summary Tables">
<code class="literal">
events_waits_summary_by_user_by_event_name
</code>
</a>
</td>
<td>
Wait events per user name and event name
</td>
</tr>
<tr>
<td>
<a class="link" href="performance-schema-wait-summary-tables.html" title="29.12.20.1 Wait Event Summary Tables">
<code class="literal">
events_waits_summary_global_by_event_name
</code>
</a>
</td>
<td>
Wait events per event name
</td>
</tr>
</tbody>
</table>
</div>
</div>
<br class="table-break"/>
<h4>
<a name="idm46045069340128">
</a>
Stage Summaries
</h4>
<div class="table">
<a name="idm46045069339440">
</a>
<p class="title">
<b>
Table 29.6 Performance Schema Stage Event Summary
Tables
</b>
</p>
<div class="table-contents">
<table frame="box" rules="all" summary="A reference that lists all Performance Schema stage event summary tables.">
<colgroup>
<col style="width: 28%"/>
<col style="width: 71%"/>
</colgroup>
<thead>
<tr>
<th>
Table Name
</th>
<th>
Description
</th>
</tr>
</thead>
<tbody>
<tr>
<td>
<a class="link" href="performance-schema-stage-summary-tables.html" title="29.12.20.2 Stage Summary Tables">
<code class="literal">
events_stages_summary_by_account_by_event_name
</code>
</a>
</td>
<td>
Stage events per account and event name
</td>
</tr>
<tr>
<td>
<a class="link" href="performance-schema-stage-summary-tables.html" title="29.12.20.2 Stage Summary Tables">
<code class="literal">
events_stages_summary_by_host_by_event_name
</code>
</a>
</td>
<td>
Stage events per host name and event name
</td>
</tr>
<tr>
<td>
<a class="link" href="performance-schema-stage-summary-tables.html" title="29.12.20.2 Stage Summary Tables">
<code class="literal">
events_stages_summary_by_thread_by_event_name
</code>
</a>
</td>
<td>
Stage waits per thread and event name
</td>
</tr>
<tr>
<td>
<a class="link" href="performance-schema-stage-summary-tables.html" title="29.12.20.2 Stage Summary Tables">
<code class="literal">
events_stages_summary_by_user_by_event_name
</code>
</a>
</td>
<td>
Stage events per user name and event name
</td>
</tr>
<tr>
<td>
<a class="link" href="performance-schema-stage-summary-tables.html" title="29.12.20.2 Stage Summary Tables">
<code class="literal">
events_stages_summary_global_by_event_name
</code>
</a>
</td>
<td>
Stage waits per event name
</td>
</tr>
</tbody>
</table>
</div>
</div>
<br class="table-break"/>
<h4>
<a name="idm46045069318208">
</a>
Statement Summaries
</h4>
<div class="table">
<a name="idm46045069317520">
</a>
<p class="title">
<b>
Table 29.7 Performance Schema Statement Event Summary
Tables
</b>
</p>
<div class="table-contents">
<table frame="box" rules="all" summary="A reference that lists all Performance Schema statement event summary tables.">
<colgroup>
<col style="width: 28%"/>
<col style="width: 71%"/>
</colgroup>
<thead>
<tr>
<th>
Table Name
</th>
<th>
Description
</th>
</tr>
</thead>
<tbody>
<tr>
<td>
<a class="link" href="performance-schema-statement-histogram-summary-tables.html" title="29.12.20.4 Statement Histogram Summary Tables">
<code class="literal">
events_statements_histogram_by_digest
</code>
</a>
</td>
<td>
Statement histograms per schema and digest value
</td>
</tr>
<tr>
<td>
<a class="link" href="performance-schema-statement-histogram-summary-tables.html" title="29.12.20.4 Statement Histogram Summary Tables">
<code class="literal">
events_statements_histogram_global
</code>
</a>
</td>
<td>
Statement histogram summarized globally
</td>
</tr>
<tr>
<td>
<a class="link" href="performance-schema-statement-summary-tables.html" title="29.12.20.3 Statement Summary Tables">
<code class="literal">
events_statements_summary_by_account_by_event_name
</code>
</a>
</td>
<td>
Statement events per account and event name
</td>
</tr>
<tr>
<td>
<a class="link" href="performance-schema-statement-summary-tables.html" title="29.12.20.3 Statement Summary Tables">
<code class="literal">
events_statements_summary_by_digest
</code>
</a>
</td>
<td>
Statement events per schema and digest value
</td>
</tr>
<tr>
<td>
<a class="link" href="performance-schema-statement-summary-tables.html" title="29.12.20.3 Statement Summary Tables">
<code class="literal">
events_statements_summary_by_host_by_event_name
</code>
</a>
</td>
<td>
Statement events per host name and event name
</td>
</tr>
<tr>
<td>
<a class="link" href="performance-schema-statement-summary-tables.html" title="29.12.20.3 Statement Summary Tables">
<code class="literal">
events_statements_summary_by_program
</code>
</a>
</td>
<td>
Statement events per stored program
</td>
</tr>
<tr>
<td>
<a class="link" href="performance-schema-statement-summary-tables.html" title="29.12.20.3 Statement Summary Tables">
<code class="literal">
events_statements_summary_by_thread_by_event_name
</code>
</a>
</td>
<td>
Statement events per thread and event name
</td>
</tr>
<tr>
<td>
<a class="link" href="performance-schema-statement-summary-tables.html" title="29.12.20.3 Statement Summary Tables">
<code class="literal">
events_statements_summary_by_user_by_event_name
</code>
</a>
</td>
<td>
Statement events per user name and event name
</td>
</tr>
<tr>
<td>
<a class="link" href="performance-schema-statement-summary-tables.html" title="29.12.20.3 Statement Summary Tables">
<code class="literal">
events_statements_summary_global_by_event_name
</code>
</a>
</td>
<td>
Statement events per event name
</td>
</tr>
<tr>
<td>
<a class="link" href="performance-schema-prepared-statements-instances-table.html" title="29.12.6.4 The prepared_statements_instances Table">
<code class="literal">
prepared_statements_instances
</code>
</a>
</td>
<td>
Prepared statement instances and statistics
</td>
</tr>
</tbody>
</table>
</div>
<div class="table-contents">
<table cellpadding="0" cellspacing="0" style="position: fixed; top: 0px; display: none; left: 401px; width: 739px;">
<thead>
<tr>
<th style="width: 413.281px;">
Table Name
</th>
<th style="width: 324.719px;">
Description
</th>
</tr>
</thead>
</table>
</div>
</div>
<br class="table-break"/>
<h4>
<a name="idm46045069280752">
</a>
Transaction Summaries
</h4>
<div class="table">
<a name="idm46045069280064">
</a>
<p class="title">
<b>
Table 29.8 Performance Schema Transaction Event Summary
Tables
</b>
</p>
<div class="table-contents">
<table frame="box" rules="all" summary="A reference that lists all Performance Schema transaction event summary tables.">
<colgroup>
<col style="width: 28%"/>
<col style="width: 71%"/>
</colgroup>
<thead>
<tr>
<th>
Table Name
</th>
<th>
Description
</th>
</tr>
</thead>
<tbody>
<tr>
<td>
<a class="link" href="performance-schema-transaction-summary-tables.html" title="29.12.20.5 Transaction Summary Tables">
<code class="literal">
events_transactions_summary_by_account_by_event_name
</code>
</a>
</td>
<td>
Transaction events per account and event name
</td>
</tr>
<tr>
<td>
<a class="link" href="performance-schema-transaction-summary-tables.html" title="29.12.20.5 Transaction Summary Tables">
<code class="literal">
events_transactions_summary_by_host_by_event_name
</code>
</a>
</td>
<td>
Transaction events per host name and event name
</td>
</tr>
<tr>
<td>
<a class="link" href="performance-schema-transaction-summary-tables.html" title="29.12.20.5 Transaction Summary Tables">
<code class="literal">
events_transactions_summary_by_thread_by_event_name
</code>
</a>
</td>
<td>
Transaction events per thread and event name
</td>
</tr>
<tr>
<td>
<a class="link" href="performance-schema-transaction-summary-tables.html" title="29.12.20.5 Transaction Summary Tables">
<code class="literal">
events_transactions_summary_by_user_by_event_name
</code>
</a>
</td>
<td>
Transaction events per user name and event name
</td>
</tr>
<tr>
<td>
<a class="link" href="performance-schema-transaction-summary-tables.html" title="29.12.20.5 Transaction Summary Tables">
<code class="literal">
events_transactions_summary_global_by_event_name
</code>
</a>
</td>
<td>
Transaction events per event name
</td>
</tr>
</tbody>
</table>
</div>
</div>
<br class="table-break"/>
<h4>
<a name="idm46045069258624">
</a>
Object Wait Summaries
</h4>
<div class="table">
<a name="idm46045069257936">
</a>
<p class="title">
<b>
Table 29.9 Performance Schema Object Event Summary
Tables
</b>
</p>
<div class="table-contents">
<table frame="box" rules="all" summary="A reference that lists all Performance Schema object event summary tables.">
<colgroup>
<col style="width: 28%"/>
<col style="width: 71%"/>
</colgroup>
<thead>
<tr>
<th>
Table Name
</th>
<th>
Description
</th>
</tr>
</thead>
<tbody>
<tr>
<td>
<a class="link" href="performance-schema-objects-summary-global-by-type-table.html" title="29.12.20.6 Object Wait Summary Table">
<code class="literal">
objects_summary_global_by_type
</code>
</a>
</td>
<td>
Object summaries
</td>
</tr>
</tbody>
</table>
</div>
</div>
<br class="table-break"/>
<h4>
<a name="idm46045069248832">
</a>
File I/O Summaries
</h4>
<div class="table">
<a name="idm46045069248144">
</a>
<p class="title">
<b>
Table 29.10 Performance Schema File I/O Event Summary
Tables
</b>
</p>
<div class="table-contents">
<table frame="box" rules="all" summary="A reference that lists all Performance Schema file I/O event summary tables.">
<colgroup>
<col style="width: 28%"/>
<col style="width: 71%"/>
</colgroup>
<thead>
<tr>
<th>
Table Name
</th>
<th>
Description
</th>
</tr>
</thead>
<tbody>
<tr>
<td>
<a class="link" href="performance-schema-file-summary-tables.html" title="29.12.20.7 File I/O Summary Tables">
<code class="literal">
file_summary_by_event_name
</code>
</a>
</td>
<td>
File events per event name
</td>
</tr>
<tr>
<td>
<a class="link" href="performance-schema-file-summary-tables.html" title="29.12.20.7 File I/O Summary Tables">
<code class="literal">
file_summary_by_instance
</code>
</a>
</td>
<td>
File events per file instance
</td>
</tr>
</tbody>
</table>
</div>
</div>
<br class="table-break"/>
<h4>
<a name="idm46045069236080">
</a>
Table I/O and Lock Wait Summaries
</h4>
<div class="table">
<a name="idm46045069235360">
</a>
<p class="title">
<b>
Table 29.11 Performance Schema Table I/O and Lock Wait Event
Summary Tables
</b>
</p>
<div class="table-contents">
<table frame="box" rules="all" summary="A reference that lists all Performance Schema table I/O and lock event summary tables.">
<colgroup>
<col style="width: 28%"/>
<col style="width: 71%"/>
</colgroup>
<thead>
<tr>
<th>
Table Name
</th>
<th>
Description
</th>
</tr>
</thead>
<tbody>
<tr>
<td>
<a class="link" href="performance-schema-table-wait-summary-tables.html#performance-schema-table-io-waits-summary-by-index-usage-table" title="29.12.20.8.2 The table_io_waits_summary_by_index_usage Table">
<code class="literal">
table_io_waits_summary_by_index_usage
</code>
</a>
</td>
<td>
Table I/O waits per index
</td>
</tr>
<tr>
<td>
<a class="link" href="performance-schema-table-wait-summary-tables.html#performance-schema-table-io-waits-summary-by-table-table" title="29.12.20.8.1 The table_io_waits_summary_by_table Table">
<code class="literal">
table_io_waits_summary_by_table
</code>
</a>
</td>
<td>
Table I/O waits per table
</td>
</tr>
<tr>
<td>
<a class="link" href="performance-schema-table-wait-summary-tables.html#performance-schema-table-lock-waits-summary-by-table-table" title="29.12.20.8.3 The table_lock_waits_summary_by_table Table">
<code class="literal">
table_lock_waits_summary_by_table
</code>
</a>
</td>
<td>
Table lock waits per table
</td>
</tr>
</tbody>
</table>
</div>
</div>
<br class="table-break"/>
<h4>
<a name="idm46045069220000">
</a>
Socket Summaries
</h4>
<div class="table">
<a name="idm46045069219312">
</a>
<p class="title">
<b>
Table 29.12 Performance Schema Socket Event Summary
Tables
</b>
</p>
<div class="table-contents">
<table frame="box" rules="all" summary="A reference that lists all Performance Schema socket event summary tables.">
<colgroup>
<col style="width: 28%"/>
<col style="width: 71%"/>
</colgroup>
<thead>
<tr>
<th>
Table Name
</th>
<th>
Description
</th>
</tr>
</thead>
<tbody>
<tr>
<td>
<a class="link" href="performance-schema-socket-summary-tables.html" title="29.12.20.9 Socket Summary Tables">
<code class="literal">
socket_summary_by_event_name
</code>
</a>
</td>
<td>
Socket waits and I/O per event name
</td>
</tr>
<tr>
<td>
<a class="link" href="performance-schema-socket-summary-tables.html" title="29.12.20.9 Socket Summary Tables">
<code class="literal">
socket_summary_by_instance
</code>
</a>
</td>
<td>
Socket waits and I/O per instance
</td>
</tr>
</tbody>
</table>
</div>
</div>
<br class="table-break"/>
<h4>
<a name="idm46045069207200">
</a>
Memory Summaries
</h4>
<div class="table">
<a name="idm46045069206512">
</a>
<p class="title">
<b>
Table 29.13 Performance Schema Memory Operation Summary
Tables
</b>
</p>
<div class="table-contents">
<table frame="box" rules="all" summary="A reference that lists all Performance Schema memory operation summary tables.">
<colgroup>
<col style="width: 28%"/>
<col style="width: 71%"/>
</colgroup>
<thead>
<tr>
<th>
Table Name
</th>
<th>
Description
</th>
</tr>
</thead>
<tbody>
<tr>
<td>
<a class="link" href="performance-schema-memory-summary-tables.html" title="29.12.20.10 Memory Summary Tables">
<code class="literal">
memory_summary_by_account_by_event_name
</code>
</a>
</td>
<td>
Memory operations per account and event name
</td>
</tr>
<tr>
<td>
<a class="link" href="performance-schema-memory-summary-tables.html" title="29.12.20.10 Memory Summary Tables">
<code class="literal">
memory_summary_by_host_by_event_name
</code>
</a>
</td>
<td>
Memory operations per host and event name
</td>
</tr>
<tr>
<td>
<a class="link" href="performance-schema-memory-summary-tables.html" title="29.12.20.10 Memory Summary Tables">
<code class="literal">
memory_summary_by_thread_by_event_name
</code>
</a>
</td>
<td>
Memory operations per thread and event name
</td>
</tr>
<tr>
<td>
<a class="link" href="performance-schema-memory-summary-tables.html" title="29.12.20.10 Memory Summary Tables">
<code class="literal">
memory_summary_by_user_by_event_name
</code>
</a>
</td>
<td>
Memory operations per user and event name
</td>
</tr>
<tr>
<td>
<a class="link" href="performance-schema-memory-summary-tables.html" title="29.12.20.10 Memory Summary Tables">
<code class="literal">
memory_summary_global_by_event_name
</code>
</a>
</td>
<td>
Memory operations globally per event name
</td>
</tr>
</tbody>
</table>
</div>
</div>
<br class="table-break"/>
<h4>
<a name="idm46045069185280">
</a>
Error Summaries
</h4>
<div class="table">
<a name="idm46045069184592">
</a>
<p class="title">
<b>
Table 29.14 Performance Schema Error Summary Tables
</b>
</p>
<div class="table-contents">
<table frame="box" rules="all" summary="A reference that lists all Performance Schema error summary tables.">
<colgroup>
<col style="width: 28%"/>
<col style="width: 71%"/>
</colgroup>
<thead>
<tr>
<th>
Table Name
</th>
<th>
Description
</th>
</tr>
</thead>
<tbody>
<tr>
<td>
<a class="link" href="performance-schema-error-summary-tables.html" title="29.12.20.11 Error Summary Tables">
<code class="literal">
events_errors_summary_by_account_by_error
</code>
</a>
</td>
<td>
Errors per account and error code
</td>
</tr>
<tr>
<td>
<a class="link" href="performance-schema-error-summary-tables.html" title="29.12.20.11 Error Summary Tables">
<code class="literal">
events_errors_summary_by_host_by_error
</code>
</a>
</td>
<td>
Errors per host and error code
</td>
</tr>
<tr>
<td>
<a class="link" href="performance-schema-error-summary-tables.html" title="29.12.20.11 Error Summary Tables">
<code class="literal">
events_errors_summary_by_thread_by_error
</code>
</a>
</td>
<td>
Errors per thread and error code
</td>
</tr>
<tr>
<td>
<a class="link" href="performance-schema-error-summary-tables.html" title="29.12.20.11 Error Summary Tables">
<code class="literal">
events_errors_summary_by_user_by_error
</code>
</a>
</td>
<td>
Errors per user and error code
</td>
</tr>
<tr>
<td>
<a class="link" href="performance-schema-error-summary-tables.html" title="29.12.20.11 Error Summary Tables">
<code class="literal">
events_errors_summary_global_by_error
</code>
</a>
</td>
<td>
Errors per error code
</td>
</tr>
</tbody>
</table>
</div>
</div>
<br class="table-break"/>
<h4>
<a name="idm46045069163488">
</a>
Status Variable Summaries
</h4>
<div class="table">
<a name="idm46045069162768">
</a>
<p class="title">
<b>
Table 29.15 Performance Schema Error Status Variable Summary
Tables
</b>
</p>
<div class="table-contents">
<table frame="box" rules="all" summary="A reference that lists all Performance Schema status variable summary tables.">
<colgroup>
<col style="width: 28%"/>
<col style="width: 71%"/>
</colgroup>
<thead>
<tr>
<th>
Table Name
</th>
<th>
Description
</th>
</tr>
</thead>
<tbody>
<tr>
<td>
<a class="link" href="performance-schema-status-variable-summary-tables.html" title="29.12.20.12 Status Variable Summary Tables">
<code class="literal">
status_by_account
</code>
</a>
</td>
<td>
Session status variables per account
</td>
</tr>
<tr>
<td>
<a class="link" href="performance-schema-status-variable-summary-tables.html" title="29.12.20.12 Status Variable Summary Tables">
<code class="literal">
status_by_host
</code>
</a>
</td>
<td>
Session status variables per host name
</td>
</tr>
<tr>
<td>
<a class="link" href="performance-schema-status-variable-summary-tables.html" title="29.12.20.12 Status Variable Summary Tables">
<code class="literal">
status_by_user
</code>
</a>
</td>
<td>
Session status variables per user name
</td>
</tr>
</tbody>
</table>
</div>
</div>
<br class="table-break"/>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/server-side-help-support.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="server-side-help-support">
</a>
7.1.17 Server-Side Help Support
</h3>
</div>
</div>
</div>
<a class="indexterm" name="idm46045260107456">
</a>
<p>
MySQL Server supports a
<a class="link" href="help.html" title="15.8.3 HELP Statement">
<code class="literal">
HELP
</code>
</a>
statement that returns information from the MySQL Reference Manual
(see
<a class="xref" href="help.html" title="15.8.3 HELP Statement">
Section 15.8.3, “HELP Statement”
</a>
). This information is stored in
several tables in the
<code class="literal">
mysql
</code>
schema (see
<a class="xref" href="system-schema.html" title="7.3 The mysql System Schema">
Section 7.3, “The mysql System Schema”
</a>
). Proper operation of the
<a class="link" href="help.html" title="15.8.3 HELP Statement">
<code class="literal">
HELP
</code>
</a>
statement requires that these
help tables be initialized.
</p>
<p>
For a new installation of MySQL using a binary or source
distribution on Unix, help-table content initialization occurs
when you initialize the data directory (see
<a class="xref" href="data-directory-initialization.html" title="2.9.1 Initializing the Data Directory">
Section 2.9.1, “Initializing the Data Directory”
</a>
). For an RPM
distribution on Linux or binary distribution on Windows, content
initialization occurs as part of the MySQL installation process.
</p>
<p>
For a MySQL upgrade using a binary distribution, help-table
content is upgraded automatically by the server. To upgrade it
manually, locate the
<code class="filename">
fill_help_tables.sql
</code>
file in the
<code class="filename">
share
</code>
or
<code class="filename">
share/mysql
</code>
directory. Change location into
that directory and process the file with the
<a class="link" href="mysql.html" title="6.5.1 mysql — The MySQL Command-Line Client">
<span class="command">
<strong>
mysql
</strong>
</span>
</a>
client as follows:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-terminal"><div class="docs-select-all right" id="sa45558849"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-terminal">mysql <span class="token property">-u</span> root <span class="token property">-p</span> mysql < fill_help_tables<span class="token punctuation">.</span>sql</code></pre>
</div>
<p>
The command shown here assumes that you connect to the server
using an account such as
<code class="literal">
root
</code>
that has
privileges for modifying tables in the
<code class="literal">
mysql
</code>
schema. Adjust the connection parameters as required.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/mysql-cluster-replication-conflict-resolution.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="mysql-cluster-replication-conflict-resolution">
</a>
25.7.12 NDB Cluster Replication Conflict Resolution
</h3>
</div>
</div>
</div>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<a class="xref" href="mysql-cluster-replication-conflict-resolution.html#conflict-resolution-requirements" title="Requirements">
Requirements
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="mysql-cluster-replication-conflict-resolution.html#conflict-resolution-source-column" title="Source Column Control">
Source Column Control
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="mysql-cluster-replication-conflict-resolution.html#conflict-resolution-control" title="Conflict Resolution Control">
Conflict Resolution Control
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="mysql-cluster-replication-conflict-resolution.html#conflict-resolution-functions" title="Conflict Resolution Functions">
Conflict Resolution Functions
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="mysql-cluster-replication-conflict-resolution.html#conflict-resolution-exceptions-table" title="Conflict Resolution Exceptions Table">
Conflict Resolution Exceptions Table
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="mysql-cluster-replication-conflict-resolution.html#conflict-detection-statvars" title="Conflict Detection Status Variables">
Conflict Detection Status Variables
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="mysql-cluster-replication-conflict-resolution.html#conflict-detection-examples" title="Examples">
Examples
</a>
</p>
</li>
</ul>
</div>
<a class="indexterm" name="idm46045085576016">
</a>
<a class="indexterm" name="idm46045085574528">
</a>
<a class="indexterm" name="idm46045085573040">
</a>
<a class="indexterm" name="idm46045085571584">
</a>
<a class="indexterm" name="idm46045085570080">
</a>
<p>
When using a replication setup involving multiple sources
(including circular replication), it is possible that different
sources may try to update the same row on the replica with
different data. Conflict resolution in NDB Cluster Replication
provides a means of resolving such conflicts by permitting a
user-defined resolution column to be used to determine whether or
not an update on a given source should be applied on the replica.
</p>
<p>
Some types of conflict resolution supported by NDB Cluster
(
<code class="literal">
NDB$OLD()
</code>
,
<code class="literal">
NDB$MAX()
</code>
, and
<code class="literal">
NDB$MAX_DELETE_WIN()
</code>
;
<code class="literal">
NDB$MAX_INS()
</code>
and
<code class="literal">
NDB$MAX_DEL_WIN_INS()
</code>
) implement this
user-defined column as a
<span class="quote">
“
<span class="quote">
timestamp
</span>
”
</span>
column (although
its type cannot be
<a class="link" href="datetime.html" title="13.2.2 The DATE, DATETIME, and TIMESTAMP Types">
<code class="literal">
TIMESTAMP
</code>
</a>
, as
explained later in this section). These types of conflict
resolution are always applied a row-by-row basis rather than a
transactional basis. The epoch-based conflict resolution functions
<code class="literal">
NDB$EPOCH()
</code>
and
<code class="literal">
NDB$EPOCH_TRANS()
</code>
compare the order in which
epochs are replicated (and thus these functions are
transactional). Different methods can be used to compare
resolution column values on the replica when conflicts occur, as
explained later in this section; the method used can be set to act
on a single table, database, or server, or on a set of one or more
tables using pattern matching. See
<a class="xref" href="mysql-cluster-replication-schema.html#ndb-replication-wildcards" title="Matching with wildcards">
Matching with wildcards
</a>
, for information about
using pattern matches in the
<code class="literal">
db
</code>
,
<code class="literal">
table_name
</code>
, and
<code class="literal">
server_id
</code>
columns of the
<code class="literal">
mysql.ndb_replication
</code>
table.
</p>
<p>
You should also keep in mind that it is the application's
responsibility to ensure that the resolution column is correctly
populated with relevant values, so that the resolution function
can make the appropriate choice when determining whether to apply
an update.
</p>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h4 class="title">
<a name="conflict-resolution-requirements">
</a>
Requirements
</h4>
</div>
</div>
</div>
<p>
Preparations for conflict resolution must be made on both the
source and the replica. These tasks are described in the
following list:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
On the source writing the binary logs, you must determine
which columns are sent (all columns or only those that have
been updated). This is done for the MySQL Server as a whole
by applying the
<a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
<span class="command">
<strong>
mysqld
</strong>
</span>
</a>
startup option
<a class="link" href="mysql-cluster-options-variables.html#option_mysqld_ndb-log-updated-only">
<code class="option">
--ndb-log-updated-only
</code>
</a>
(described later in this section), or on one or more
specific tables by placing the proper entries in the
<code class="literal">
mysql.ndb_replication
</code>
table (see
<a class="xref" href="mysql-cluster-replication-schema.html#ndb-replication-ndb-replication" title="ndb_replication Table">
ndb_replication Table
</a>
).
</p>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
If you are replicating tables with very large columns
(such as
<a class="link" href="blob.html" title="13.3.4 The BLOB and TEXT Types">
<code class="literal">
TEXT
</code>
</a>
or
<a class="link" href="blob.html" title="13.3.4 The BLOB and TEXT Types">
<code class="literal">
BLOB
</code>
</a>
columns),
<a class="link" href="mysql-cluster-options-variables.html#option_mysqld_ndb-log-updated-only">
<code class="option">
--ndb-log-updated-only
</code>
</a>
can
also be useful for reducing the size of the binary logs
and avoiding possible replication failures due to
exceeding
<a class="link" href="server-system-variables.html#sysvar_max_allowed_packet">
<code class="literal">
max_allowed_packet
</code>
</a>
.
</p>
<p>
See
<a class="xref" href="replication-features-max-allowed-packet.html" title="19.5.1.20 Replication and max_allowed_packet">
Section 19.5.1.20, “Replication and max_allowed_packet”
</a>
,
for more information about this issue.
</p>
</div>
</li>
<li class="listitem">
<p>
On the replica, you must determine which type of conflict
resolution to apply (
<span class="quote">
“
<span class="quote">
latest timestamp wins
</span>
”
</span>
,
<span class="quote">
“
<span class="quote">
same timestamp wins
</span>
”
</span>
,
<span class="quote">
“
<span class="quote">
primary
wins
</span>
”
</span>
,
<span class="quote">
“
<span class="quote">
primary wins, complete
transaction
</span>
”
</span>
, or none). This is done using the
<code class="literal">
mysql.ndb_replication
</code>
system table, and
applies to one or more specific tables (see
<a class="xref" href="mysql-cluster-replication-schema.html#ndb-replication-ndb-replication" title="ndb_replication Table">
ndb_replication Table
</a>
).
</p>
</li>
<li class="listitem">
<p>
NDB Cluster also supports read conflict detection, that is,
detecting conflicts between reads of a given row in one
cluster and updates or deletes of the same row in another
cluster. This requires exclusive read locks obtained by
setting
<a class="link" href="mysql-cluster-options-variables.html#sysvar_ndb_log_exclusive_reads">
<code class="literal">
ndb_log_exclusive_reads
</code>
</a>
equal to 1 on the replica. All rows read by a conflicting
read are logged in the exceptions table. For more
information, see
<a class="xref" href="mysql-cluster-replication-conflict-resolution.html#conflict-resolution-read-conflicts" title="Read conflict detection and resolution">
Read conflict detection and resolution
</a>
.
</p>
</li>
<li class="listitem">
<p>
When using
<code class="literal">
NDB$MAX_INS()
</code>
or
<code class="literal">
NDB$MAX_DEL_WIN_INS()
</code>
,
<code class="literal">
NDB
</code>
can apply
<code class="literal">
WRITE_ROW
</code>
events idempotently, mapping
such an event to an insert when the incoming row does not
already exist, or to an update if it does.
</p>
<p>
When using any conflict resolution function other than
<code class="literal">
NDB$MAX_INS()
</code>
or
<code class="literal">
NDB$MAX_DEL_WIN_INS()
</code>
, an incoming write
is always rejected if the row already exists.
</p>
</li>
</ul>
</div>
<p>
When using the functions
<code class="literal">
NDB$OLD()
</code>
,
<code class="literal">
NDB$MAX()
</code>
,
<code class="literal">
NDB$MAX_DELETE_WIN()
</code>
,
<code class="literal">
NDB$MAX_INS()
</code>
, and
<code class="literal">
NDB$MAX_DEL_WIN_INS()
</code>
for timestamp-based
conflict resolution, we often refer to the column used for
determining updates as a
<span class="quote">
“
<span class="quote">
timestamp
</span>
”
</span>
column.
However, the data type of this column is never
<a class="link" href="datetime.html" title="13.2.2 The DATE, DATETIME, and TIMESTAMP Types">
<code class="literal">
TIMESTAMP
</code>
</a>
; instead, its data type
should be
<a class="link" href="integer-types.html" title="13.1.2 Integer Types (Exact Value) - INTEGER, INT, SMALLINT, TINYINT, MEDIUMINT, BIGINT">
<code class="literal">
INT
</code>
</a>
(
<a class="link" href="integer-types.html" title="13.1.2 Integer Types (Exact Value) - INTEGER, INT, SMALLINT, TINYINT, MEDIUMINT, BIGINT">
<code class="literal">
INTEGER
</code>
</a>
) or
<a class="link" href="integer-types.html" title="13.1.2 Integer Types (Exact Value) - INTEGER, INT, SMALLINT, TINYINT, MEDIUMINT, BIGINT">
<code class="literal">
BIGINT
</code>
</a>
. The
<span class="quote">
“
<span class="quote">
timestamp
</span>
”
</span>
column should also be
<code class="literal">
UNSIGNED
</code>
and
<code class="literal">
NOT NULL
</code>
.
</p>
<p>
The
<code class="literal">
NDB$EPOCH()
</code>
and
<code class="literal">
NDB$EPOCH_TRANS()
</code>
functions discussed later
in this section work by comparing the relative order of
replication epochs applied on a primary and secondary NDB
Cluster, and do not make use of timestamps.
</p>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h4 class="title">
<a name="conflict-resolution-source-column">
</a>
Source Column Control
</h4>
</div>
</div>
</div>
<p>
<a class="indexterm" name="idm46045085512560">
</a>
We can see update operations in terms of
<span class="quote">
“
<span class="quote">
before
</span>
”
</span>
and
<span class="quote">
“
<span class="quote">
after
</span>
”
</span>
images—that is, the states of the
table before and after the update is applied. Normally, when
updating a table with a primary key, the
<span class="quote">
“
<span class="quote">
before
</span>
”
</span>
image is not of great interest; however, when we need to
determine on a per-update basis whether or not to use the
updated values on a replica, we need to make sure that both
images are written to the source's binary log. This is done
with the
<a class="link" href="mysql-cluster-options-variables.html#option_mysqld_ndb-log-update-as-write">
<code class="option">
--ndb-log-update-as-write
</code>
</a>
option
for
<a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
<span class="command">
<strong>
mysqld
</strong>
</span>
</a>
, as described later in this
section.
</p>
<div class="important" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Important
</div>
<p>
Whether logging of complete rows or of updated columns only is
done is decided when the MySQL server is started, and cannot
be changed online; you must either restart
<a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
<span class="command">
<strong>
mysqld
</strong>
</span>
</a>
, or start a new
<a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
<span class="command">
<strong>
mysqld
</strong>
</span>
</a>
instance with different logging
options.
</p>
</div>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h4 class="title">
<a name="conflict-resolution-control">
</a>
Conflict Resolution Control
</h4>
</div>
</div>
</div>
<p>
<a class="indexterm" name="idm46045085501696">
</a>
Conflict resolution is usually enabled on the server where
conflicts can occur. Like logging method selection, it is
enabled by entries in the
<code class="literal">
mysql.ndb_replication
</code>
table.
</p>
<p>
<code class="literal">
NBT_UPDATED_ONLY_MINIMAL
</code>
and
<code class="literal">
NBT_UPDATED_FULL_MINIMAL
</code>
can be used with
<code class="literal">
NDB$EPOCH()
</code>
,
<code class="literal">
NDB$EPOCH2()
</code>
,
and
<code class="literal">
NDB$EPOCH_TRANS()
</code>
, because these do not
require
<span class="quote">
“
<span class="quote">
before
</span>
”
</span>
values of columns which are not
primary keys. Conflict resolution algorithms requiring the old
values, such as
<code class="literal">
NDB$MAX()
</code>
and
<code class="literal">
NDB$OLD()
</code>
, do not work correctly with these
<code class="literal">
binlog_type
</code>
values.
</p>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h4 class="title">
<a name="conflict-resolution-functions">
</a>
Conflict Resolution Functions
</h4>
</div>
</div>
</div>
<p>
This section provides detailed information about the functions
which can be used for conflict detection and resolution with NDB
Replication.
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<a class="xref" href="mysql-cluster-replication-conflict-resolution.html#mysql-cluster-replication-ndb-old" title="NDB$OLD()">
NDB$OLD()
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="mysql-cluster-replication-conflict-resolution.html#mysql-cluster-replication-ndb-max" title="NDB$MAX()">
NDB$MAX()
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="mysql-cluster-replication-conflict-resolution.html#mysql-cluster-replication-ndb-max-delete-win" title="NDB$MAX_DELETE_WIN()">
NDB$MAX_DELETE_WIN()
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="mysql-cluster-replication-conflict-resolution.html#mysql-cluster-replication-ndb-max-ins" title="NDB$MAX_INS()">
NDB$MAX_INS()
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="mysql-cluster-replication-conflict-resolution.html#mysql-cluster-replication-ndb-max-del-win-ins" title="NDB$MAX_DEL_WIN_INS()">
NDB$MAX_DEL_WIN_INS()
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="mysql-cluster-replication-conflict-resolution.html#mysql-cluster-replication-ndb-epoch" title="NDB$EPOCH()">
NDB$EPOCH()
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="mysql-cluster-replication-conflict-resolution.html#mysql-cluster-replication-ndb-epoch-trans" title="NDB$EPOCH_TRANS()">
NDB$EPOCH_TRANS()
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="mysql-cluster-replication-conflict-resolution.html#mysql-cluster-replication-ndb-epoch2" title="NDB$EPOCH2()">
NDB$EPOCH2()
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="mysql-cluster-replication-conflict-resolution.html#mysql-cluster-replication-ndb-epoch2-trans" title="NDB$EPOCH2_TRANS()">
NDB$EPOCH2_TRANS()
</a>
</p>
</li>
</ul>
</div>
<h5>
<a name="mysql-cluster-replication-ndb-old">
</a>
NDB$OLD()
</h5>
<p>
<a class="indexterm" name="idm46045085480480">
</a>
If the value of
<em class="replaceable">
<code>
column_name
</code>
</em>
is the
same on both the source and the replica, then the update is
applied; otherwise, the update is not applied on the replica and
an exception is written to the log. This is illustrated by the
following pseudocode:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-clike"><div class="docs-select-all right" id="sa68449250"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-clike"><span class="token keyword">if</span> <span class="token punctuation">(</span><em class="replaceable">source_old_column_value</em> <span class="token operator">==</span> <em class="replaceable">replica_current_column_value</em><span class="token punctuation">)</span>
<span class="token function">apply_update</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token keyword">else</span>
<span class="token function">log_exception</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
<a class="indexterm" name="idm46045085476432">
</a>
This function can be used for
<span class="quote">
“
<span class="quote">
same value wins
</span>
”
</span>
conflict resolution. This type of conflict resolution ensures
that updates are not applied on the replica from the wrong
source.
</p>
<div class="important" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Important
</div>
<p>
The column value from the source's
<span class="quote">
“
<span class="quote">
before
</span>
”
</span>
image is used by this function.
</p>
</div>
<h5>
<a name="mysql-cluster-replication-ndb-max">
</a>
NDB$MAX()
</h5>
<p>
<a class="indexterm" name="idm46045085471792">
</a>
For an update or delete operation, if the
<span class="quote">
“
<span class="quote">
timestamp
</span>
”
</span>
column value for a given row coming
from the source is higher than that on the replica, it is
applied; otherwise it is not applied on the replica. This is
illustrated by the following pseudocode:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-clike"><div class="docs-select-all right" id="sa99049355"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-clike"><span class="token keyword">if</span> <span class="token punctuation">(</span><em class="replaceable">source_new_column_value</em> <span class="token operator">></span> <em class="replaceable">replica_current_column_value</em><span class="token punctuation">)</span>
<span class="token function">apply_update</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
<a class="indexterm" name="idm46045085467776">
</a>
This function can be used for
<span class="quote">
“
<span class="quote">
greatest timestamp
wins
</span>
”
</span>
conflict resolution. This type of conflict
resolution ensures that, in the event of a conflict, the version
of the row that was most recently updated is the version that
persists.
</p>
<p>
This function has no effects on conflicts between write
operations, other than that a write operation with the same
primary key as a previous write is always rejected; it is
accepted and applied only if no write operation using the same
primary key already exists. You can use
<code class="literal">
<a class="link" href="mysql-cluster-replication-conflict-resolution.html#mysql-cluster-replication-ndb-max-ins" title="NDB$MAX_INS()">
NDB$MAX_INS()
</a>
</code>
to handle conflict resolution between writes.
</p>
<div class="important" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Important
</div>
<p>
The column value from the sources's
<span class="quote">
“
<span class="quote">
after
</span>
”
</span>
image is used by this function.
</p>
</div>
<h5>
<a name="mysql-cluster-replication-ndb-max-delete-win">
</a>
NDB$MAX_DELETE_WIN()
</h5>
<p>
<a class="indexterm" name="idm46045085460992">
</a>
This is a variation on
<code class="literal">
NDB$MAX()
</code>
. Due to the
fact that no timestamp is available for a delete operation, a
delete using
<code class="literal">
NDB$MAX()
</code>
is in fact processed
as
<code class="literal">
NDB$OLD
</code>
, but for some use cases, this is
not optimal. For
<code class="literal">
NDB$MAX_DELETE_WIN()
</code>
, if the
<span class="quote">
“
<span class="quote">
timestamp
</span>
”
</span>
column value for a given row adding or
updating an existing row coming from the source is higher than
that on the replica, it is applied. However, delete operations
are treated as always having the higher value. This is
illustrated by the following pseudocode:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-clike"><div class="docs-select-all right" id="sa43223813"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-clike"><span class="token keyword">if</span> <span class="token punctuation">(</span> <span class="token punctuation">(</span><em class="replaceable">source_new_column_value</em> <span class="token operator">></span> <em class="replaceable">replica_current_column_value</em><span class="token punctuation">)</span>
<span class="token operator">||</span>
<em class="replaceable">operation<span class="token punctuation">.</span>type</em> <span class="token operator">==</span> <span class="token string">"delete"</span><span class="token punctuation">)</span>
<span class="token function">apply_update</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
<a class="indexterm" name="idm46045085453424">
</a>
This function can be used for
<span class="quote">
“
<span class="quote">
greatest timestamp, delete
wins
</span>
”
</span>
conflict resolution. This type of conflict
resolution ensures that, in the event of a conflict, the version
of the row that was deleted or (otherwise) most recently updated
is the version that persists.
</p>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
As with
<code class="literal">
NDB$MAX()
</code>
, the column value from
the source's
<span class="quote">
“
<span class="quote">
after
</span>
”
</span>
image is the value used
by this function.
</p>
</div>
<h5>
<a name="mysql-cluster-replication-ndb-max-ins">
</a>
NDB$MAX_INS()
</h5>
<p>
<a class="indexterm" name="idm46045085448064">
</a>
This function provides support for resolution of conflicting
write operations. Such conflicts are handled by
<span class="quote">
“
<span class="quote">
NDB$MAX_INS()
</span>
”
</span>
as follows:
</p>
<div class="orderedlist">
<ol class="orderedlist" type="1">
<li class="listitem">
<p>
If there is no conflicting write, apply this one (this is
the same as
<code class="literal">
NDB$MAX()
</code>
).
</p>
</li>
<li class="listitem">
<p>
Otherwise, apply
<span class="quote">
“
<span class="quote">
greatest timestamp wins
</span>
”
</span>
conflict resolution, as follows:
</p>
<div class="orderedlist">
<ol class="orderedlist" type="a">
<li class="listitem">
<p>
If the timestamp for the incoming write is greater than
that of the conflicting write, apply the incoming
operation.
</p>
</li>
<li class="listitem">
<p>
If the timestamp for the incoming write is
<span class="emphasis">
<em>
not
</em>
</span>
greater, reject the incoming
write operation.
</p>
</li>
</ol>
</div>
</li>
</ol>
</div>
<p>
When handling an insert operation,
<code class="literal">
NDB$MAX_INS()
</code>
compares timestamps from the
source and replica as illustrated by the following pseudocode:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-clike"><div class="docs-select-all right" id="sa83442239"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-clike"><span class="token keyword">if</span> <span class="token punctuation">(</span>source_new_column_value <span class="token operator">></span> replica_current_column_value<span class="token punctuation">)</span>
<span class="token function">apply_insert</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token keyword">else</span>
<span class="token function">log_exception</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
For an update operation, the updated timestamp column value from
the source is compared with the replica's timestamp column
value, as shown here:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-clike"><div class="docs-select-all right" id="sa91279523"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-clike"><span class="token keyword">if</span> <span class="token punctuation">(</span>source_new_column_value <span class="token operator">></span> replica_current_column_value<span class="token punctuation">)</span>
<span class="token function">apply_update</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token keyword">else</span>
<span class="token function">log_exception</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
This is the same as performed by
<code class="literal">
<a class="link" href="mysql-cluster-replication-conflict-resolution.html#mysql-cluster-replication-ndb-max" title="NDB$MAX()">
NDB$MAX()
</a>
</code>
.
</p>
<p>
For delete operations, the handling is also the same as that
performed by
<code class="literal">
NDB$MAX()
</code>
(and thus the same as
<code class="literal">
NDB$OLD()
</code>
), and is done like this:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-clike"><div class="docs-select-all right" id="sa11653318"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-clike"><span class="token keyword">if</span> <span class="token punctuation">(</span>source_new_column_value <span class="token operator">==</span> replica_current_column_value<span class="token punctuation">)</span>
<span class="token function">apply_delete</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token keyword">else</span>
<span class="token function">log_exception</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span></code></pre>
</div>
<h5>
<a name="mysql-cluster-replication-ndb-max-del-win-ins">
</a>
NDB$MAX_DEL_WIN_INS()
</h5>
<p>
<a class="indexterm" name="idm46045085428480">
</a>
This function provides support for resolution of conflicting
write operations, along with
<span class="quote">
“
<span class="quote">
delete wins
</span>
”
</span>
resolution like that of
<code class="literal">
<a class="link" href="mysql-cluster-replication-conflict-resolution.html#mysql-cluster-replication-ndb-max-delete-win" title="NDB$MAX_DELETE_WIN()">
NDB$MAX_DELETE_WIN()
</a>
</code>
.
Write conflicts are handled by
<code class="literal">
NDB$MAX_DEL_WIN_INS()
</code>
as shown here:
</p>
<div class="orderedlist">
<ol class="orderedlist" type="1">
<li class="listitem">
<p>
If there is no conflicting write, apply this one (this is
the same as
<code class="literal">
NDB$MAX_DELETE_WIN()
</code>
).
</p>
</li>
<li class="listitem">
<p>
Otherwise, apply
<span class="quote">
“
<span class="quote">
greatest timestamp wins
</span>
”
</span>
conflict resolution, as follows:
</p>
<div class="orderedlist">
<ol class="orderedlist" type="a">
<li class="listitem">
<p>
If the timestamp for the incoming write is greater than
that of the conflicting write, apply the incoming
operation.
</p>
</li>
<li class="listitem">
<p>
If the timestamp for the incoming write is
<span class="emphasis">
<em>
not
</em>
</span>
greater, reject the incoming
write operation.
</p>
</li>
</ol>
</div>
</li>
</ol>
</div>
<p>
Handling of insert operations as performed by
<code class="literal">
NDB$MAX_DEL_WIN_INS()
</code>
can be represented in
pseudocode as shown here:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-clike"><div class="docs-select-all right" id="sa5163908"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-clike"><span class="token keyword">if</span> <span class="token punctuation">(</span>source_new_column_value <span class="token operator">></span> replica_current_column_value<span class="token punctuation">)</span>
<span class="token function">apply_insert</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token keyword">else</span>
<span class="token function">log_exception</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
For update operations, the source's updated timestamp
column value is compared with replica's timestamp column
value, like this (again using pseudocode):
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-clike"><div class="docs-select-all right" id="sa67377767"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-clike"><span class="token keyword">if</span> <span class="token punctuation">(</span>source_new_column_value <span class="token operator">></span> replica_current_column_value<span class="token punctuation">)</span>
<span class="token function">apply_update</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token keyword">else</span>
<span class="token function">log_exception</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
Deletes are handled using a
<span class="quote">
“
<span class="quote">
delete always wins
</span>
”
</span>
strategy (the same as
<code class="literal">
NDB$MAX_DELETE_WIN()
</code>
);
a
<code class="literal">
DELETE
</code>
is always applied without any regard
to any timestamp values, as illustrated by this pseudocode:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-clike"><div class="docs-select-all right" id="sa14068515"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-clike"><span class="token keyword">if</span> <span class="token punctuation">(</span>operation<span class="token punctuation">.</span>type <span class="token operator">==</span> <span class="token string">"delete"</span><span class="token punctuation">)</span>
<span class="token function">apply_delete</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
For conflicts between update and delete operations, this
function behaves identically to
<code class="literal">
NDB$MAX_DELETE_WIN()
</code>
.
</p>
<h5>
<a name="mysql-cluster-replication-ndb-epoch">
</a>
NDB$EPOCH()
</h5>
<p>
<a class="indexterm" name="idm46045085407040">
</a>
<a class="indexterm" name="idm46045085405968">
</a>
The
<code class="literal">
NDB$EPOCH()
</code>
function tracks the order in
which replicated epochs are applied on a replica cluster
relative to changes originating on the replica. This relative
ordering is used to determine whether changes originating on the
replica are concurrent with any changes that originate locally,
and are therefore potentially in conflict.
</p>
<p>
Most of what follows in the description of
<code class="literal">
NDB$EPOCH()
</code>
also applies to
<code class="literal">
NDB$EPOCH_TRANS()
</code>
. Any exceptions are noted
in the text.
</p>
<p>
<code class="literal">
NDB$EPOCH()
</code>
is asymmetric, operating on one
NDB Cluster in a bidirectional replication configuration
(sometimes referred to as
<span class="quote">
“
<span class="quote">
active-active
</span>
”
</span>
replication). We refer here to cluster on which it operates as
the primary, and the other as the secondary. The replica on the
primary is responsible for detecting and handling conflicts,
while the replica on the secondary is not involved in any
conflict detection or handling.
</p>
<p>
When the replica on the primary detects conflicts, it injects
events into its own binary log to compensate for these; this
ensures that the secondary NDB Cluster eventually realigns
itself with the primary and so keeps the primary and secondary
from diverging. This compensation and realignment mechanism
requires that the primary NDB Cluster always wins any conflicts
with the secondary—that is, that the primary's
changes are always used rather than those from the secondary in
event of a conflict. This
<span class="quote">
“
<span class="quote">
primary always wins
</span>
”
</span>
rule has the following implications:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
Operations that change data, once committed on the primary,
are fully persistent and are not undone or rolled back by
conflict detection and resolution.
</p>
</li>
<li class="listitem">
<p>
Data read from the primary is fully consistent. Any changes
committed on the Primary (locally or from the replica) are
not reverted later.
</p>
</li>
<li class="listitem">
<p>
Operations that change data on the secondary may later be
reverted if the primary determines that they are in
conflict.
</p>
</li>
<li class="listitem">
<p>
Individual rows read on the secondary are self-consistent at
all times, each row always reflecting either a state
committed by the secondary, or one committed by the primary.
</p>
</li>
<li class="listitem">
<p>
Sets of rows read on the secondary may not necessarily be
consistent at a given single point in time. For
<code class="literal">
NDB$EPOCH_TRANS()
</code>
, this is a transient
state; for
<code class="literal">
NDB$EPOCH()
</code>
, it can be a
persistent state.
</p>
</li>
<li class="listitem">
<p>
Assuming a period of sufficient length without any
conflicts, all data on the secondary NDB Cluster
(eventually) becomes consistent with the primary's
data.
</p>
</li>
</ul>
</div>
<p>
<code class="literal">
NDB$EPOCH()
</code>
and
<code class="literal">
NDB$EPOCH_TRANS()
</code>
do not require any user
schema modifications, or application changes to provide conflict
detection. However, careful thought must be given to the schema
used, and the access patterns used, to verify that the complete
system behaves within specified limits.
</p>
<p>
Each of the
<code class="literal">
NDB$EPOCH()
</code>
and
<code class="literal">
NDB$EPOCH_TRANS()
</code>
functions can take an
optional parameter; this is the number of bits to use to
represent the lower 32 bits of the epoch, and should be set to
no less than the value calculated as shown here:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa77052478"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token function">CEIL</span><span class="token punctuation">(</span> <span class="token function">LOG2</span><span class="token punctuation">(</span> TimeBetweenGlobalCheckpoints <span class="token operator">/</span> TimeBetweenEpochs <span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token number">1</span><span class="token punctuation">)</span></code></pre>
</div>
<p>
For the default values of these configuration parameters (2000
and 100 milliseconds, respectively), this gives a value of 5
bits, so the default value (6) should be sufficient, unless
other values are used for
<a class="link" href="mysql-cluster-ndbd-definition.html#ndbparam-ndbd-timebetweenglobalcheckpoints">
<code class="literal">
TimeBetweenGlobalCheckpoints
</code>
</a>
,
<a class="link" href="mysql-cluster-ndbd-definition.html#ndbparam-ndbd-timebetweenepochs">
<code class="literal">
TimeBetweenEpochs
</code>
</a>
, or
both. A value that is too small can result in false positives,
while one that is too large could lead to excessive wasted space
in the database.
</p>
<p>
Both
<code class="literal">
NDB$EPOCH()
</code>
and
<code class="literal">
NDB$EPOCH_TRANS()
</code>
insert entries for
conflicting rows into the relevant exceptions tables, provided
that these tables have been defined according to the same
exceptions table schema rules as described elsewhere in this
section (see
<a class="xref" href="mysql-cluster-replication-conflict-resolution.html#mysql-cluster-replication-ndb-old" title="NDB$OLD()">
NDB$OLD()
</a>
). You must
create any exceptions table before creating the data table with
which it is to be used.
</p>
<p>
As with the other conflict detection functions discussed in this
section,
<code class="literal">
NDB$EPOCH()
</code>
and
<code class="literal">
NDB$EPOCH_TRANS()
</code>
are activated by including
relevant entries in the
<code class="literal">
mysql.ndb_replication
</code>
table (see
<a class="xref" href="mysql-cluster-replication-schema.html#ndb-replication-ndb-replication" title="ndb_replication Table">
ndb_replication Table
</a>
).
The roles of the primary and secondary NDB Clusters in this
scenario are fully determined by
<code class="literal">
mysql.ndb_replication
</code>
table entries.
</p>
<p>
Because the conflict detection algorithms employed by
<code class="literal">
NDB$EPOCH()
</code>
and
<code class="literal">
NDB$EPOCH_TRANS()
</code>
are asymmetric, you must
use different values for the
<code class="literal">
server_id
</code>
entries of the primary and secondary replicas.
</p>
<p>
A conflict between
<code class="literal">
DELETE
</code>
operations alone is
not sufficient to trigger a conflict using
<code class="literal">
NDB$EPOCH()
</code>
or
<code class="literal">
NDB$EPOCH_TRANS()
</code>
, and the relative placement
within epochs does not matter.
</p>
<p>
<a name="mysql-cluster-replication-ndb-epoch-limitations">
</a>
<span class="bold">
<strong>
Limitations on NDB$EPOCH()
</strong>
</span>
</p>
<p>
<a class="indexterm" name="idm46045085364416">
</a>
The following limitations currently apply when using
<code class="literal">
NDB$EPOCH()
</code>
to perform conflict detection:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
Conflicts are detected using NDB Cluster epoch boundaries,
with granularity proportional to
<a class="link" href="mysql-cluster-ndbd-definition.html#ndbparam-ndbd-timebetweenepochs">
<code class="literal">
TimeBetweenEpochs
</code>
</a>
(default: 100 milliseconds). The minimum conflict window is
the minimum time during which concurrent updates to the same
data on both clusters always report a conflict. This is
always a nonzero length of time, and is roughly proportional
to
<code class="literal">
2 * (latency + queueing +
TimeBetweenEpochs)
</code>
. This implies
that—assuming the default for
<a class="link" href="mysql-cluster-ndbd-definition.html#ndbparam-ndbd-timebetweenepochs">
<code class="literal">
TimeBetweenEpochs
</code>
</a>
and ignoring any latency between clusters (as well as any
queuing delays)—the minimum conflict window size is
approximately 200 milliseconds. This minimum window should
be considered when looking at expected application
<span class="quote">
“
<span class="quote">
race
</span>
”
</span>
patterns.
</p>
</li>
<li class="listitem">
<p>
Additional storage is required for tables using the
<code class="literal">
NDB$EPOCH()
</code>
and
<code class="literal">
NDB$EPOCH_TRANS()
</code>
functions; from 1 to 32
bits extra space per row is required, depending on the value
passed to the function.
</p>
</li>
<li class="listitem">
<p>
Conflicts between delete operations may result in divergence
between the primary and secondary. When a row is deleted on
both clusters concurrently, the conflict can be detected,
but is not recorded, since the row is deleted. This means
that further conflicts during the propagation of any
subsequent realignment operations are not detected, which
can lead to divergence.
</p>
<p>
Deletes should be externally serialized, or routed to one
cluster only. Alternatively, a separate row should be
updated transactionally with such deletes and any inserts
that follow them, so that conflicts can be tracked across
row deletes. This may require changes in applications.
</p>
</li>
<li class="listitem">
<p>
Only two NDB Clusters in a bidirectional
<span class="quote">
“
<span class="quote">
active-active
</span>
”
</span>
configuration are currently
supported when using
<code class="literal">
NDB$EPOCH()
</code>
or
<code class="literal">
NDB$EPOCH_TRANS()
</code>
for conflict detection.
</p>
</li>
<li class="listitem">
<p>
Tables having
<a class="link" href="blob.html" title="13.3.4 The BLOB and TEXT Types">
<code class="literal">
BLOB
</code>
</a>
or
<a class="link" href="blob.html" title="13.3.4 The BLOB and TEXT Types">
<code class="literal">
TEXT
</code>
</a>
columns are not
currently supported with
<code class="literal">
NDB$EPOCH()
</code>
or
<code class="literal">
NDB$EPOCH_TRANS()
</code>
.
</p>
</li>
</ul>
</div>
<h5>
<a name="mysql-cluster-replication-ndb-epoch-trans">
</a>
NDB$EPOCH_TRANS()
</h5>
<p>
<a class="indexterm" name="idm46045085342624">
</a>
<code class="literal">
NDB$EPOCH_TRANS()
</code>
extends the
<code class="literal">
NDB$EPOCH()
</code>
function. Conflicts are detected
and handled in the same way using the
<span class="quote">
“
<span class="quote">
primary wins
all
</span>
”
</span>
rule (see
<a class="xref" href="mysql-cluster-replication-conflict-resolution.html#mysql-cluster-replication-ndb-epoch" title="NDB$EPOCH()">
NDB$EPOCH()
</a>
) but with
the extra condition that any other rows updated in the same
transaction in which the conflict occurred are also regarded as
being in conflict. In other words, where
<code class="literal">
NDB$EPOCH()
</code>
realigns individual conflicting
rows on the secondary,
<code class="literal">
NDB$EPOCH_TRANS()
</code>
realigns conflicting transactions.
</p>
<p>
In addition, any transactions which are detectably dependent on
a conflicting transaction are also regarded as being in
conflict, these dependencies being determined by the contents of
the secondary cluster's binary log. Since the binary log
contains only data modification operations (inserts, updates,
and deletes), only overlapping data modifications are used to
determine dependencies between transactions.
</p>
<p>
<code class="literal">
NDB$EPOCH_TRANS()
</code>
is subject to the same
conditions and limitations as
<code class="literal">
NDB$EPOCH()
</code>
,
and in addition requires that all transaction IDs are recorded
in the secondary's binary log, using
<a class="link" href="mysql-cluster-options-variables.html#option_mysqld_ndb-log-transaction-id">
<code class="option">
--ndb-log-transaction-id
</code>
</a>
set to
<code class="literal">
ON
</code>
. This adds a variable amount of overhead
(up to 13 bytes per row).
</p>
<p>
See
<a class="xref" href="mysql-cluster-replication-conflict-resolution.html#mysql-cluster-replication-ndb-epoch" title="NDB$EPOCH()">
NDB$EPOCH()
</a>
.
</p>
<h5>
<a name="mysql-cluster-replication-ndb-epoch2">
</a>
NDB$EPOCH2()
</h5>
<p>
<a class="indexterm" name="idm46045085329904">
</a>
The
<code class="literal">
NDB$EPOCH2()
</code>
function is similar to
<code class="literal">
NDB$EPOCH()
</code>
, except that
<code class="literal">
NDB$EPOCH2()
</code>
provides for delete-delete
handling with a bidirectional replication topology. In this
scenario, primary and secondary roles are assigned to the two
sources by setting the
<a class="link" href="mysql-cluster-options-variables.html#sysvar_ndb_conflict_role">
<code class="literal">
ndb_conflict_role
</code>
</a>
system
variable to the appropriate value on each source (usually one
each of
<code class="literal">
PRIMARY
</code>
,
<code class="literal">
SECONDARY
</code>
). When this is done, modifications
made by the secondary are reflected by the primary back to the
secondary which then conditionally applies them.
</p>
<h5>
<a name="mysql-cluster-replication-ndb-epoch2-trans">
</a>
NDB$EPOCH2_TRANS()
</h5>
<p>
<a class="indexterm" name="idm46045085321920">
</a>
<code class="literal">
NDB$EPOCH2_TRANS()
</code>
extends the
<code class="literal">
NDB$EPOCH2()
</code>
function. Conflicts are detected
and handled in the same way, and assigning primary and secondary
roles to the replicating clusters, but with the extra condition
that any other rows updated in the same transaction in which the
conflict occurred are also regarded as being in conflict. That
is,
<code class="literal">
NDB$EPOCH2()
</code>
realigns individual
conflicting rows on the secondary, while
<code class="literal">
NDB$EPOCH_TRANS()
</code>
realigns conflicting
transactions.
</p>
<p>
Where
<code class="literal">
NDB$EPOCH()
</code>
and
<code class="literal">
NDB$EPOCH_TRANS()
</code>
use metadata that is
specified per row, per last modified epoch, to determine on the
primary whether an incoming replicated row change from the
secondary is concurrent with a locally committed change;
concurrent changes are regarded as conflicting, with subsequent
exceptions table updates and realignment of the secondary. A
problem arises when a row is deleted on the primary so there is
no longer any last-modified epoch available to determine whether
any replicated operations conflict, which means that conflicting
delete operations are not detected. This can result in
divergence, an example being a delete on one cluster which is
concurrent with a delete and insert on the other; this why
delete operations can be routed to only one cluster when using
<code class="literal">
NDB$EPOCH()
</code>
and
<code class="literal">
NDB$EPOCH_TRANS()
</code>
.
</p>
<p>
<code class="literal">
NDB$EPOCH2()
</code>
bypasses the issue just
described—storing information about deleted rows on the
PRIMARY—by ignoring any delete-delete conflict, and by
avoiding any potential resultant divergence as well. This is
accomplished by reflecting any operation successfully applied on
and replicated from the secondary back to the secondary. On its
return to the secondary, it can be used to reapply an operation
on the secondary which was deleted by an operation originating
from the primary.
</p>
<p>
When using
<code class="literal">
NDB$EPOCH2()
</code>
, you should keep in
mind that the secondary applies the delete from the primary,
removing the new row until it is restored by a reflected
operation. In theory, the subsequent insert or update on the
secondary conflicts with the delete from the primary, but in
this case, we choose to ignore this and allow the secondary to
<span class="quote">
“
<span class="quote">
win
</span>
”
</span>
, in the interest of preventing divergence
between the clusters. In other words, after a delete, the
primary does not detect conflicts, and instead adopts the
secondary's following changes immediately. Because of this,
the secondary's state can revisit multiple previous
committed states as it progresses to a final (stable) state, and
some of these may be visible.
</p>
<p>
You should also be aware that reflecting all operations from the
secondary back to the primary increases the size of the
primary's logbinary log, as well as demands on bandwidth, CPU
usage, and disk I/O.
</p>
<p>
Application of reflected operations on the secondary depends on
the state of the target row on the secondary. Whether or not
reflected changes are applied on the secondary can be tracked by
checking the
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_conflict_reflected_op_prepare_count">
<code class="literal">
Ndb_conflict_reflected_op_prepare_count
</code>
</a>
and
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_conflict_reflected_op_discard_count">
<code class="literal">
Ndb_conflict_reflected_op_discard_count
</code>
</a>
status variables. The number of changes applied is simply the
difference between these two values (note that
<code class="literal">
Ndb_conflict_reflected_op_prepare_count
</code>
is
always greater than or equal to
<code class="literal">
Ndb_conflict_reflected_op_discard_count
</code>
).
</p>
<p>
Events are applied if and only if both of the following
conditions are true:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
The existence of the row—that is, whether or not it
exists—is in accordance with the type of event. For
delete and update operations, the row must already exist.
For insert operations, the row must
<span class="emphasis">
<em>
not
</em>
</span>
exist.
</p>
</li>
<li class="listitem">
<p>
The row was last modified by the primary. It is possible
that the modification was accomplished through the execution
of a reflected operation.
</p>
</li>
</ul>
</div>
<p>
If both of these conditions are not met, the reflected operation
is discarded by the secondary.
</p>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h4 class="title">
<a name="conflict-resolution-exceptions-table">
</a>
Conflict Resolution Exceptions Table
</h4>
</div>
</div>
</div>
<p>
<a class="indexterm" name="idm46045085297616">
</a>
<a class="indexterm" name="idm46045085296096">
</a>
To use the
<code class="literal">
NDB$OLD()
</code>
conflict resolution
function, it is also necessary to create an exceptions table
corresponding to each
<a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4">
<code class="literal">
NDB
</code>
</a>
table for
which this type of conflict resolution is to be employed. This
is also true when using
<code class="literal">
NDB$EPOCH()
</code>
or
<code class="literal">
NDB$EPOCH_TRANS()
</code>
. The name of this table is
that of the table for which conflict resolution is to be
applied, with the string
<code class="literal">
$EX
</code>
appended. (For
example, if the name of the original table is
<code class="literal">
mytable
</code>
, the name of the corresponding
exceptions table name should be
<code class="literal">
mytable$EX
</code>
.)
The syntax for creating the exceptions table is as shown here:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa36915216"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">TABLE</span> <em class="replaceable">original_table</em>$EX <span class="token punctuation">(</span>
<span class="token punctuation">[</span><span class="token keyword">NDB</span>$<span class="token punctuation">]</span>server_id <span class="token datatype">INT</span> <span class="token keyword">UNSIGNED</span><span class="token punctuation">,</span>
<span class="token punctuation">[</span><span class="token keyword">NDB</span>$<span class="token punctuation">]</span>source_server_id <span class="token datatype">INT</span> <span class="token keyword">UNSIGNED</span><span class="token punctuation">,</span>
<span class="token punctuation">[</span><span class="token keyword">NDB</span>$<span class="token punctuation">]</span>source_epoch <span class="token datatype">BIGINT</span> <span class="token keyword">UNSIGNED</span><span class="token punctuation">,</span>
<span class="token punctuation">[</span><span class="token keyword">NDB</span>$<span class="token punctuation">]</span>count <span class="token datatype">INT</span> <span class="token keyword">UNSIGNED</span><span class="token punctuation">,</span>
<span class="token punctuation">[</span><span class="token keyword">NDB</span>$OP_TYPE <span class="token datatype">ENUM</span><span class="token punctuation">(</span><span class="token string">'WRITE_ROW'</span><span class="token punctuation">,</span><span class="token string">'UPDATE_ROW'</span><span class="token punctuation">,</span> <span class="token string">'DELETE_ROW'</span><span class="token punctuation">,</span>
<span class="token string">'REFRESH_ROW'</span><span class="token punctuation">,</span> <span class="token string">'READ_ROW'</span><span class="token punctuation">)</span> <span class="token operator">NOT</span> <span class="token boolean">NULL</span><span class="token punctuation">,</span><span class="token punctuation">]</span>
<span class="token punctuation">[</span><span class="token keyword">NDB</span>$CFT_CAUSE <span class="token datatype">ENUM</span><span class="token punctuation">(</span><span class="token string">'ROW_DOES_NOT_EXIST'</span><span class="token punctuation">,</span> <span class="token string">'ROW_ALREADY_EXISTS'</span><span class="token punctuation">,</span>
<span class="token string">'DATA_IN_CONFLICT'</span><span class="token punctuation">,</span> <span class="token string">'TRANS_IN_CONFLICT'</span><span class="token punctuation">)</span> <span class="token operator">NOT</span> <span class="token boolean">NULL</span><span class="token punctuation">,</span><span class="token punctuation">]</span>
<span class="token punctuation">[</span><span class="token keyword">NDB</span>$ORIG_TRANSID <span class="token datatype">BIGINT</span> <span class="token keyword">UNSIGNED</span> <span class="token operator">NOT</span> <span class="token boolean">NULL</span><span class="token punctuation">,</span><span class="token punctuation">]</span>
<em class="replaceable">original_table_pk_columns</em><span class="token punctuation">,</span>
<span class="token punctuation">[</span><em class="replaceable">orig_table_column</em><span class="token operator">|</span><em class="replaceable">orig_table_column</em>$<span class="token keyword">OLD</span><span class="token operator">|</span><em class="replaceable">orig_table_column</em>$<span class="token keyword">NEW</span><span class="token punctuation">,</span><span class="token punctuation">]</span>
<span class="token punctuation">[</span><em class="replaceable">additional_columns</em><span class="token punctuation">,</span><span class="token punctuation">]</span>
<span class="token keyword">PRIMARY</span> <span class="token keyword">KEY</span><span class="token punctuation">(</span><span class="token punctuation">[</span><span class="token keyword">NDB</span>$<span class="token punctuation">]</span>server_id<span class="token punctuation">,</span> <span class="token punctuation">[</span><span class="token keyword">NDB</span>$<span class="token punctuation">]</span>source_server_id<span class="token punctuation">,</span> <span class="token punctuation">[</span><span class="token keyword">NDB</span>$<span class="token punctuation">]</span>source_epoch<span class="token punctuation">,</span> <span class="token punctuation">[</span><span class="token keyword">NDB</span>$<span class="token punctuation">]</span>count<span class="token punctuation">)</span>
<span class="token punctuation">)</span> <span class="token keyword">ENGINE</span><span class="token operator">=</span><span class="token keyword">NDB</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
The first four columns are required. The names of the first four
columns and the columns matching the original table's
primary key columns are not critical; however, we suggest for
reasons of clarity and consistency, that you use the names shown
here for the
<code class="literal">
server_id
</code>
,
<code class="literal">
source_server_id
</code>
,
<code class="literal">
source_epoch
</code>
, and
<code class="literal">
count
</code>
columns, and that you use the same names as in the original
table for the columns matching those in the original
table's primary key.
</p>
<p>
If the exceptions table uses one or more of the optional columns
<code class="literal">
NDB$OP_TYPE
</code>
,
<code class="literal">
NDB$CFT_CAUSE
</code>
, or
<code class="literal">
NDB$ORIG_TRANSID
</code>
discussed later in this
section, then each of the required columns must also be named
using the prefix
<code class="literal">
NDB$
</code>
. If desired, you can
use the
<code class="literal">
NDB$
</code>
prefix to name the required
columns even if you do not define any optional columns, but in
this case, all four of the required columns must be named using
the prefix.
</p>
<p>
Following these columns, the columns making up the original
table's primary key should be copied in the order in which
they are used to define the primary key of the original table.
The data types for the columns duplicating the primary key
columns of the original table should be the same as (or larger
than) those of the original columns. A subset of the primary key
columns may be used.
</p>
<p>
The exceptions table must use the
<a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4">
<code class="literal">
NDB
</code>
</a>
storage engine. (An example
that uses
<code class="literal">
NDB$OLD()
</code>
with an exceptions table
is shown later in this section.)
</p>
<p>
Additional columns may optionally be defined following the
copied primary key columns, but not before any of them; any such
extra columns cannot be
<code class="literal">
NOT NULL
</code>
. NDB Cluster
supports three additional, predefined optional columns
<code class="literal">
NDB$OP_TYPE
</code>
,
<code class="literal">
NDB$CFT_CAUSE
</code>
, and
<code class="literal">
NDB$ORIG_TRANSID
</code>
, which are described in the
next few paragraphs.
</p>
<p>
<a class="indexterm" name="idm46045085269040">
</a>
<code class="literal">
NDB$OP_TYPE
</code>
: This column can be used to
obtain the type of operation causing the conflict. If you use
this column, define it as shown here:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa52920963"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">NDB</span>$OP_TYPE <span class="token datatype">ENUM</span><span class="token punctuation">(</span><span class="token string">'WRITE_ROW'</span><span class="token punctuation">,</span> <span class="token string">'UPDATE_ROW'</span><span class="token punctuation">,</span> <span class="token string">'DELETE_ROW'</span><span class="token punctuation">,</span>
<span class="token string">'REFRESH_ROW'</span><span class="token punctuation">,</span> <span class="token string">'READ_ROW'</span><span class="token punctuation">)</span> <span class="token operator">NOT</span> <span class="token boolean">NULL</span></code></pre>
</div>
<p>
The
<code class="literal">
WRITE_ROW
</code>
,
<code class="literal">
UPDATE_ROW
</code>
,
and
<code class="literal">
DELETE_ROW
</code>
operation types represent
user-initiated operations.
<code class="literal">
REFRESH_ROW
</code>
operations are operations generated by conflict resolution in
compensating transactions sent back to the originating cluster
from the cluster that detected the conflict.
<code class="literal">
READ_ROW
</code>
operations are user-initiated read
tracking operations defined with exclusive row locks.
</p>
<p>
<a class="indexterm" name="idm46045085261408">
</a>
<code class="literal">
NDB$CFT_CAUSE
</code>
: You can define an optional
column
<code class="literal">
NDB$CFT_CAUSE
</code>
which provides the cause
of the registered conflict. This column, if used, is defined as
shown here:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa96458903"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">NDB</span>$CFT_CAUSE <span class="token datatype">ENUM</span><span class="token punctuation">(</span><span class="token string">'ROW_DOES_NOT_EXIST'</span><span class="token punctuation">,</span> <span class="token string">'ROW_ALREADY_EXISTS'</span><span class="token punctuation">,</span>
<span class="token string">'DATA_IN_CONFLICT'</span><span class="token punctuation">,</span> <span class="token string">'TRANS_IN_CONFLICT'</span><span class="token punctuation">)</span> <span class="token operator">NOT</span> <span class="token boolean">NULL</span></code></pre>
</div>
<p>
<code class="literal">
ROW_DOES_NOT_EXIST
</code>
can be reported as the
cause for
<code class="literal">
UPDATE_ROW
</code>
and
<code class="literal">
WRITE_ROW
</code>
operations;
<code class="literal">
ROW_ALREADY_EXISTS
</code>
can be reported for
<code class="literal">
WRITE_ROW
</code>
events.
<code class="literal">
DATA_IN_CONFLICT
</code>
is reported when a row-based
conflict function detects a conflict;
<code class="literal">
TRANS_IN_CONFLICT
</code>
is reported when a
transactional conflict function rejects all of the operations
belonging to a complete transaction.
</p>
<p>
<a class="indexterm" name="idm46045085251680">
</a>
<code class="literal">
NDB$ORIG_TRANSID
</code>
: The
<code class="literal">
NDB$ORIG_TRANSID
</code>
column, if used, contains
the ID of the originating transaction. This column should be
defined as follows:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa14278416"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">NDB</span>$ORIG_TRANSID <span class="token datatype">BIGINT</span> <span class="token keyword">UNSIGNED</span> <span class="token operator">NOT</span> <span class="token boolean">NULL</span></code></pre>
</div>
<p>
<code class="literal">
NDB$ORIG_TRANSID
</code>
is a 64-bit value generated
by
<code class="literal">
NDB
</code>
. This value can be used to correlate
multiple exceptions table entries belonging to the same
conflicting transaction from the same or different exceptions
tables.
</p>
<p>
Additional reference columns which are not part of the original
table's primary key can be named
<code class="literal">
<em class="replaceable">
<code>
colname
</code>
</em>
$OLD
</code>
or
<code class="literal">
<em class="replaceable">
<code>
colname
</code>
</em>
$NEW
</code>
.
<code class="literal">
<em class="replaceable">
<code>
colname
</code>
</em>
$OLD
</code>
references old values in update and delete operations—that
is, operations containing
<code class="literal">
DELETE_ROW
</code>
events.
<code class="literal">
<em class="replaceable">
<code>
colname
</code>
</em>
$NEW
</code>
can be
used to reference new values in insert and update
operations—in other words, operations using
<code class="literal">
WRITE_ROW
</code>
events,
<code class="literal">
UPDATE_ROW
</code>
events, or both types of events.
Where a conflicting operation does not supply a value for a
given reference column that is not a primary key, the exceptions
table row contains either
<code class="literal">
NULL
</code>
, or a defined
default value for that column.
</p>
<div class="important" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Important
</div>
<p>
The
<code class="literal">
mysql.ndb_replication
</code>
table is read
when a data table is set up for replication, so the row
corresponding to a table to be replicated must be inserted
into
<code class="literal">
mysql.ndb_replication
</code>
<span class="emphasis">
<em>
before
</em>
</span>
the table to be replicated is
created.
</p>
</div>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h4 class="title">
<a name="conflict-detection-statvars">
</a>
Conflict Detection Status Variables
</h4>
</div>
</div>
</div>
<p>
<a class="indexterm" name="idm46045085232656">
</a>
<a class="indexterm" name="idm46045085231136">
</a>
Several status variables can be used to monitor conflict
detection. You can see how many rows have been found in conflict
by
<code class="literal">
NDB$EPOCH()
</code>
since this replica was last
restarted from the current value of the
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_conflict_fn_epoch">
<code class="literal">
Ndb_conflict_fn_epoch
</code>
</a>
system
status variable.
</p>
<p>
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_conflict_fn_epoch_trans">
<code class="literal">
Ndb_conflict_fn_epoch_trans
</code>
</a>
provides the number of rows that have been found directly in
conflict by
<code class="literal">
NDB$EPOCH_TRANS()
</code>
.
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_conflict_fn_epoch2">
<code class="literal">
Ndb_conflict_fn_epoch2
</code>
</a>
and
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_conflict_fn_epoch2_trans">
<code class="literal">
Ndb_conflict_fn_epoch2_trans
</code>
</a>
show the number of rows found in conflict by
<code class="literal">
NDB$EPOCH2()
</code>
and
<code class="literal">
NDB$EPOCH2_TRANS()
</code>
, respectively. The number
of rows actually realigned, including those affected due to
their membership in or dependency on the same transactions as
other conflicting rows, is given by
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_conflict_trans_row_reject_count">
<code class="literal">
Ndb_conflict_trans_row_reject_count
</code>
</a>
.
</p>
<p>
Another server status variable
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_conflict_fn_max">
<code class="literal">
Ndb_conflict_fn_max
</code>
</a>
provides a
count of the number of times that a row was not applied on the
current SQL node due to
<span class="quote">
“
<span class="quote">
greatest timestamp wins
</span>
”
</span>
conflict resolution since the last time that
<a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
<span class="command">
<strong>
mysqld
</strong>
</span>
</a>
was started.
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_conflict_fn_max_del_win">
<code class="literal">
Ndb_conflict_fn_max_del_win
</code>
</a>
provides a count of the number of times that conflict resolution
based on the outcome of
<code class="literal">
NDB$MAX_DELETE_WIN()
</code>
has been applied.
</p>
<p>
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_conflict_fn_max_ins">
<code class="literal">
Ndb_conflict_fn_max_ins
</code>
</a>
tracks
the number of times that
<span class="quote">
“
<span class="quote">
greater timestamp wins
</span>
”
</span>
handling has been applied to write operations (using
<code class="literal">
NDB$MAX_INS()
</code>
); a count of the number of
times that
<span class="quote">
“
<span class="quote">
same timestamp wins
</span>
”
</span>
handling of writes
has been applied (as implemented by
<code class="literal">
NDB$MAX_DEL_WIN_INS()
</code>
), is provided by the
status variable
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_conflict_fn_max_del_win_ins">
<code class="literal">
Ndb_conflict_fn_max_del_win_ins
</code>
</a>
.
</p>
<p>
The number of times that a row was not applied as the result of
<span class="quote">
“
<span class="quote">
same timestamp wins
</span>
”
</span>
conflict resolution on a
given
<a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
<span class="command">
<strong>
mysqld
</strong>
</span>
</a>
since the last time it was
restarted is given by the global status variable
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_conflict_fn_old">
<code class="literal">
Ndb_conflict_fn_old
</code>
</a>
. In
addition to incrementing
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_conflict_fn_old">
<code class="literal">
Ndb_conflict_fn_old
</code>
</a>
, the
primary key of the row that was not used is inserted into an
<span class="firstterm">
exceptions table
</span>
, as
explained elsewhere in this section.
</p>
<p>
See also
<a class="xref" href="mysql-cluster-options-variables.html#mysql-cluster-status-variables" title="25.4.3.9.3 NDB Cluster Status Variables">
Section 25.4.3.9.3, “NDB Cluster Status Variables”
</a>
.
</p>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h4 class="title">
<a name="conflict-detection-examples">
</a>
Examples
</h4>
</div>
</div>
</div>
<p>
The following examples assume that you have already a working
NDB Cluster replication setup, as described in
<a class="xref" href="mysql-cluster-replication-preparation.html" title="25.7.5 Preparing the NDB Cluster for Replication">
Section 25.7.5, “Preparing the NDB Cluster for Replication”
</a>
, and
<a class="xref" href="mysql-cluster-replication-starting.html" title="25.7.6 Starting NDB Cluster Replication (Single Replication Channel)">
Section 25.7.6, “Starting NDB Cluster Replication (Single Replication Channel)”
</a>
.
</p>
<p>
<a name="conflict-detection-ndbmax-example">
</a>
<b>
NDB$MAX() example.
</b>
Suppose you wish to enable
<span class="quote">
“
<span class="quote">
greatest timestamp
wins
</span>
”
</span>
conflict resolution on table
<code class="literal">
test.t1
</code>
, using column
<code class="literal">
mycol
</code>
as the
<span class="quote">
“
<span class="quote">
timestamp
</span>
”
</span>
. This
can be done using the following steps:
</p>
<div class="orderedlist">
<ol class="orderedlist" type="1">
<li class="listitem">
<p>
Make sure that you have started the source
<a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
<span class="command">
<strong>
mysqld
</strong>
</span>
</a>
with
<a class="link" href="mysql-cluster-options-variables.html#option_mysqld_ndb-log-update-as-write">
<code class="option">
--ndb-log-update-as-write=OFF
</code>
</a>
.
</p>
</li>
<li class="listitem">
<p>
On the source, perform this
<a class="link" href="insert.html" title="15.2.7 INSERT Statement">
<code class="literal">
INSERT
</code>
</a>
statement:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa29980381"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">INSERT</span> <span class="token keyword">INTO</span> mysql<span class="token punctuation">.</span>ndb_replication
<span class="token keyword">VALUES</span> <span class="token punctuation">(</span><span class="token string">'test'</span><span class="token punctuation">,</span> <span class="token string">'t1'</span><span class="token punctuation">,</span> <span class="token number">0</span><span class="token punctuation">,</span> <span class="token boolean">NULL</span><span class="token punctuation">,</span> <span class="token string">'NDB$MAX(mycol)'</span><span class="token punctuation">)</span><span class="token punctuation">;</span></code></pre>
</div>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
If the
<code class="literal">
ndb_replication
</code>
table does not
already exist, you must create it. See
<a class="xref" href="mysql-cluster-replication-schema.html#ndb-replication-ndb-replication" title="ndb_replication Table">
ndb_replication Table
</a>
.
</p>
</div>
<p>
Inserting a 0 into the
<code class="literal">
server_id
</code>
column
indicates that all SQL nodes accessing this table should use
conflict resolution. If you want to use conflict resolution
on a specific
<a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
<span class="command">
<strong>
mysqld
</strong>
</span>
</a>
only, use the actual
server ID.
</p>
<p>
Inserting
<code class="literal">
NULL
</code>
into the
<code class="literal">
binlog_type
</code>
column has the same effect as
inserting 0 (
<code class="literal">
NBT_DEFAULT
</code>
); the server
default is used.
</p>
</li>
<li class="listitem">
<p>
Create the
<code class="literal">
test.t1
</code>
table:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa37589193"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">TABLE</span> test<span class="token punctuation">.</span>t1 <span class="token punctuation">(</span>
<span class="token keyword"><em class="replaceable">columns</em></span>
mycol <span class="token datatype">INT</span> <span class="token keyword">UNSIGNED</span><span class="token punctuation">,</span>
<span class="token keyword"><em class="replaceable">columns</em></span>
<span class="token punctuation">)</span> <span class="token keyword">ENGINE</span><span class="token operator">=</span><span class="token keyword">NDB</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
Now, when updates are performed on this table, conflict
resolution is applied, and the version of the row having the
greatest value for
<code class="literal">
mycol
</code>
is written to
the replica.
</p>
</li>
</ol>
</div>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
Other
<code class="literal">
binlog_type
</code>
options such as
<code class="literal">
NBT_UPDATED_ONLY_USE_UPDATE
</code>
(
<code class="literal">
6
</code>
) should be used to control logging on
the source using the
<code class="literal">
ndb_replication
</code>
table
rather than by using command-line options.
</p>
</div>
<p>
<a name="conflict-detection-ndbold-example">
</a>
<b>
NDB$OLD() example.
</b>
Suppose an
<a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4">
<code class="literal">
NDB
</code>
</a>
table such as the
one defined here is being replicated, and you wish to enable
<span class="quote">
“
<span class="quote">
same timestamp wins
</span>
”
</span>
conflict resolution for
updates to this table:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa52215811"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">TABLE</span> test<span class="token punctuation">.</span>t2 <span class="token punctuation">(</span>
a <span class="token datatype">INT</span> <span class="token keyword">UNSIGNED</span> <span class="token operator">NOT</span> <span class="token boolean">NULL</span><span class="token punctuation">,</span>
b <span class="token datatype">CHAR</span><span class="token punctuation">(</span><span class="token number">25</span><span class="token punctuation">)</span> <span class="token operator">NOT</span> <span class="token boolean">NULL</span><span class="token punctuation">,</span>
<span class="token keyword"><em class="replaceable">columns</em></span><span class="token punctuation">,</span>
mycol <span class="token datatype">INT</span> <span class="token keyword">UNSIGNED</span> <span class="token operator">NOT</span> <span class="token boolean">NULL</span><span class="token punctuation">,</span>
<span class="token keyword"><em class="replaceable">columns</em></span><span class="token punctuation">,</span>
<span class="token keyword">PRIMARY</span> <span class="token keyword">KEY</span> pk <span class="token punctuation">(</span>a<span class="token punctuation">,</span> b<span class="token punctuation">)</span>
<span class="token punctuation">)</span> <span class="token keyword">ENGINE</span><span class="token operator">=</span><span class="token keyword">NDB</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
The following steps are required, in the order shown:
</p>
<div class="orderedlist">
<ol class="orderedlist" type="1">
<li class="listitem">
<p>
First—and
<span class="emphasis">
<em>
prior
</em>
</span>
to creating
<code class="literal">
test.t2
</code>
—you must insert a row into
the
<a class="link" href="mysql-cluster-replication-schema.html#ndb-replication-ndb-replication" title="ndb_replication Table">
<code class="literal">
mysql.ndb_replication
</code>
</a>
table, as shown here:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa59328526"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">INSERT</span> <span class="token keyword">INTO</span> mysql<span class="token punctuation">.</span>ndb_replication
<span class="token keyword">VALUES</span> <span class="token punctuation">(</span><span class="token string">'test'</span><span class="token punctuation">,</span> <span class="token string">'t2'</span><span class="token punctuation">,</span> <span class="token number">0</span><span class="token punctuation">,</span> <span class="token number">0</span><span class="token punctuation">,</span> <span class="token string">'NDB$OLD(mycol)'</span><span class="token punctuation">)</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
Possible values for the
<code class="literal">
binlog_type
</code>
column are shown earlier in this section; in this case, we
use
<code class="literal">
0
</code>
to specify that the server default
logging behavior be used. The value
<code class="literal">
'NDB$OLD(mycol)'
</code>
should be inserted into
the
<code class="literal">
conflict_fn
</code>
column.
</p>
</li>
<li class="listitem">
<p>
Create an appropriate exceptions table for
<code class="literal">
test.t2
</code>
. The table creation statement
shown here includes all required columns; any additional
columns must be declared following these columns, and before
the definition of the table's primary key.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa87884760"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">TABLE</span> test<span class="token punctuation">.</span>t2$EX <span class="token punctuation">(</span>
server_id <span class="token datatype">INT</span> <span class="token keyword">UNSIGNED</span><span class="token punctuation">,</span>
source_server_id <span class="token datatype">INT</span> <span class="token keyword">UNSIGNED</span><span class="token punctuation">,</span>
source_epoch <span class="token datatype">BIGINT</span> <span class="token keyword">UNSIGNED</span><span class="token punctuation">,</span>
count <span class="token datatype">INT</span> <span class="token keyword">UNSIGNED</span><span class="token punctuation">,</span>
a <span class="token datatype">INT</span> <span class="token keyword">UNSIGNED</span> <span class="token operator">NOT</span> <span class="token boolean">NULL</span><span class="token punctuation">,</span>
b <span class="token datatype">CHAR</span><span class="token punctuation">(</span><span class="token number">25</span><span class="token punctuation">)</span> <span class="token operator">NOT</span> <span class="token boolean">NULL</span><span class="token punctuation">,</span>
<span class="token punctuation">[</span><em class="replaceable">additional_columns</em><span class="token punctuation">,</span><span class="token punctuation">]</span>
<span class="token keyword">PRIMARY</span> <span class="token keyword">KEY</span><span class="token punctuation">(</span>server_id<span class="token punctuation">,</span> source_server_id<span class="token punctuation">,</span> source_epoch<span class="token punctuation">,</span> count<span class="token punctuation">)</span>
<span class="token punctuation">)</span> <span class="token keyword">ENGINE</span><span class="token operator">=</span><span class="token keyword">NDB</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
We can include additional columns for information about the
type, cause, and originating transaction ID for a given
conflict. We are also not required to supply matching
columns for all primary key columns in the original table.
This means you can create the exceptions table like this:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa70273731"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">TABLE</span> test<span class="token punctuation">.</span>t2$EX <span class="token punctuation">(</span>
<span class="token keyword">NDB</span>$server_id <span class="token datatype">INT</span> <span class="token keyword">UNSIGNED</span><span class="token punctuation">,</span>
<span class="token keyword">NDB</span>$source_server_id <span class="token datatype">INT</span> <span class="token keyword">UNSIGNED</span><span class="token punctuation">,</span>
<span class="token keyword">NDB</span>$source_epoch <span class="token datatype">BIGINT</span> <span class="token keyword">UNSIGNED</span><span class="token punctuation">,</span>
<span class="token keyword">NDB</span>$count <span class="token datatype">INT</span> <span class="token keyword">UNSIGNED</span><span class="token punctuation">,</span>
a <span class="token datatype">INT</span> <span class="token keyword">UNSIGNED</span> <span class="token operator">NOT</span> <span class="token boolean">NULL</span><span class="token punctuation">,</span>
<span class="token keyword">NDB</span>$OP_TYPE <span class="token datatype">ENUM</span><span class="token punctuation">(</span><span class="token string">'WRITE_ROW'</span><span class="token punctuation">,</span><span class="token string">'UPDATE_ROW'</span><span class="token punctuation">,</span> <span class="token string">'DELETE_ROW'</span><span class="token punctuation">,</span>
<span class="token string">'REFRESH_ROW'</span><span class="token punctuation">,</span> <span class="token string">'READ_ROW'</span><span class="token punctuation">)</span> <span class="token operator">NOT</span> <span class="token boolean">NULL</span><span class="token punctuation">,</span>
<span class="token keyword">NDB</span>$CFT_CAUSE <span class="token datatype">ENUM</span><span class="token punctuation">(</span><span class="token string">'ROW_DOES_NOT_EXIST'</span><span class="token punctuation">,</span> <span class="token string">'ROW_ALREADY_EXISTS'</span><span class="token punctuation">,</span>
<span class="token string">'DATA_IN_CONFLICT'</span><span class="token punctuation">,</span> <span class="token string">'TRANS_IN_CONFLICT'</span><span class="token punctuation">)</span> <span class="token operator">NOT</span> <span class="token boolean">NULL</span><span class="token punctuation">,</span>
<span class="token keyword">NDB</span>$ORIG_TRANSID <span class="token datatype">BIGINT</span> <span class="token keyword">UNSIGNED</span> <span class="token operator">NOT</span> <span class="token boolean">NULL</span><span class="token punctuation">,</span>
<span class="token punctuation">[</span><em class="replaceable">additional_columns</em><span class="token punctuation">,</span><span class="token punctuation">]</span>
<span class="token keyword">PRIMARY</span> <span class="token keyword">KEY</span><span class="token punctuation">(</span><span class="token keyword">NDB</span>$server_id<span class="token punctuation">,</span> <span class="token keyword">NDB</span>$source_server_id<span class="token punctuation">,</span> <span class="token keyword">NDB</span>$source_epoch<span class="token punctuation">,</span> <span class="token keyword">NDB</span>$count<span class="token punctuation">)</span>
<span class="token punctuation">)</span> <span class="token keyword">ENGINE</span><span class="token operator">=</span><span class="token keyword">NDB</span><span class="token punctuation">;</span></code></pre>
</div>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
The
<code class="literal">
NDB$
</code>
prefix is required for the
four required columns since we included at least one of
the columns
<code class="literal">
NDB$OP_TYPE
</code>
,
<code class="literal">
NDB$CFT_CAUSE
</code>
, or
<code class="literal">
NDB$ORIG_TRANSID
</code>
in the table
definition.
</p>
</div>
</li>
<li class="listitem">
<p>
Create the table
<code class="literal">
test.t2
</code>
as shown
previously.
</p>
</li>
</ol>
</div>
<p>
These steps must be followed for every table for which you wish
to perform conflict resolution using
<code class="literal">
NDB$OLD()
</code>
. For each such table, there must be
a corresponding row in
<code class="literal">
mysql.ndb_replication
</code>
,
and there must be an exceptions table in the same database as
the table being replicated.
</p>
<p>
<a name="conflict-resolution-read-conflicts">
</a>
<b>
Read conflict detection and resolution.
</b>
<a class="indexterm" name="idm46045085141456">
</a>
<a class="indexterm" name="idm46045085139936">
</a>
NDB Cluster also supports tracking of read operations, which
makes it possible in circular replication setups to manage
conflicts between reads of a given row in one cluster and
updates or deletes of the same row in another. This example
uses
<code class="literal">
employee
</code>
and
<code class="literal">
department
</code>
tables to model a scenario in
which an employee is moved from one department to another on
the source cluster (which we refer to hereafter as cluster
<span class="emphasis">
<em>
A
</em>
</span>
) while the replica cluster (hereafter
<span class="emphasis">
<em>
B
</em>
</span>
) updates the employee count of the
employee's former department in an interleaved
transaction.
</p>
<p>
The data tables have been created using the following SQL
statements:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa36768688"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token comment" spellcheck="true"># Employee table</span>
<span class="token keyword">CREATE</span> <span class="token keyword">TABLE</span> employee <span class="token punctuation">(</span>
id <span class="token datatype">INT</span> <span class="token keyword">PRIMARY</span> <span class="token keyword">KEY</span><span class="token punctuation">,</span>
<span class="token keyword">name</span> <span class="token datatype">VARCHAR</span><span class="token punctuation">(</span><span class="token number">2000</span><span class="token punctuation">)</span><span class="token punctuation">,</span>
dept <span class="token datatype">INT</span> <span class="token operator">NOT</span> <span class="token boolean">NULL</span>
<span class="token punctuation">)</span> <span class="token keyword">ENGINE</span><span class="token operator">=</span><span class="token keyword">NDB</span><span class="token punctuation">;</span>
<span class="token comment" spellcheck="true"># Department table</span>
<span class="token keyword">CREATE</span> <span class="token keyword">TABLE</span> department <span class="token punctuation">(</span>
id <span class="token datatype">INT</span> <span class="token keyword">PRIMARY</span> <span class="token keyword">KEY</span><span class="token punctuation">,</span>
<span class="token keyword">name</span> <span class="token datatype">VARCHAR</span><span class="token punctuation">(</span><span class="token number">2000</span><span class="token punctuation">)</span><span class="token punctuation">,</span>
members <span class="token datatype">INT</span>
<span class="token punctuation">)</span> <span class="token keyword">ENGINE</span><span class="token operator">=</span><span class="token keyword">NDB</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
The contents of the two tables include the rows shown in the
(partial) output of the following
<a class="link" href="select.html" title="15.2.13 SELECT Statement">
<code class="literal">
SELECT
</code>
</a>
statements:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa73224750"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> id<span class="token punctuation">,</span> <span class="token keyword">name</span><span class="token punctuation">,</span> dept <span class="token keyword">FROM</span> employee<span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> id <span class="token punctuation">|</span> name <span class="token punctuation">|</span> dept <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span>
<span class="token output"><span class="token punctuation">|</span> 998 <span class="token punctuation">|</span> Mike <span class="token punctuation">|</span> 3 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 999 <span class="token punctuation">|</span> Joe <span class="token punctuation">|</span> 3 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 1000 <span class="token punctuation">|</span> Mary <span class="token punctuation">|</span> 3 <span class="token punctuation">|</span></span>
<span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> id<span class="token punctuation">,</span> <span class="token keyword">name</span><span class="token punctuation">,</span> members <span class="token keyword">FROM</span> department<span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> id <span class="token punctuation">|</span> name <span class="token punctuation">|</span> members <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span>
<span class="token output"><span class="token punctuation">|</span> 3 <span class="token punctuation">|</span> Old project <span class="token punctuation">|</span> 24 <span class="token punctuation">|</span></span>
<span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
</div>
<p>
We assume that we are already using an exceptions table that
includes the four required columns (and these are used for this
table's primary key), the optional columns for operation
type and cause, and the original table's primary key
column, created using the SQL statement shown here:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa52127753"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">TABLE</span> employee$EX <span class="token punctuation">(</span>
<span class="token keyword">NDB</span>$server_id <span class="token datatype">INT</span> <span class="token keyword">UNSIGNED</span><span class="token punctuation">,</span>
<span class="token keyword">NDB</span>$source_server_id <span class="token datatype">INT</span> <span class="token keyword">UNSIGNED</span><span class="token punctuation">,</span>
<span class="token keyword">NDB</span>$source_epoch <span class="token datatype">BIGINT</span> <span class="token keyword">UNSIGNED</span><span class="token punctuation">,</span>
<span class="token keyword">NDB</span>$count <span class="token datatype">INT</span> <span class="token keyword">UNSIGNED</span><span class="token punctuation">,</span>
<span class="token keyword">NDB</span>$OP_TYPE <span class="token datatype">ENUM</span><span class="token punctuation">(</span> <span class="token string">'WRITE_ROW'</span><span class="token punctuation">,</span><span class="token string">'UPDATE_ROW'</span><span class="token punctuation">,</span> <span class="token string">'DELETE_ROW'</span><span class="token punctuation">,</span>
<span class="token string">'REFRESH_ROW'</span><span class="token punctuation">,</span><span class="token string">'READ_ROW'</span><span class="token punctuation">)</span> <span class="token operator">NOT</span> <span class="token boolean">NULL</span><span class="token punctuation">,</span>
<span class="token keyword">NDB</span>$CFT_CAUSE <span class="token datatype">ENUM</span><span class="token punctuation">(</span> <span class="token string">'ROW_DOES_NOT_EXIST'</span><span class="token punctuation">,</span>
<span class="token string">'ROW_ALREADY_EXISTS'</span><span class="token punctuation">,</span>
<span class="token string">'DATA_IN_CONFLICT'</span><span class="token punctuation">,</span>
<span class="token string">'TRANS_IN_CONFLICT'</span><span class="token punctuation">)</span> <span class="token operator">NOT</span> <span class="token boolean">NULL</span><span class="token punctuation">,</span>
id <span class="token datatype">INT</span> <span class="token operator">NOT</span> <span class="token boolean">NULL</span><span class="token punctuation">,</span>
<span class="token keyword">PRIMARY</span> <span class="token keyword">KEY</span><span class="token punctuation">(</span><span class="token keyword">NDB</span>$server_id<span class="token punctuation">,</span> <span class="token keyword">NDB</span>$source_server_id<span class="token punctuation">,</span> <span class="token keyword">NDB</span>$source_epoch<span class="token punctuation">,</span> <span class="token keyword">NDB</span>$count<span class="token punctuation">)</span>
<span class="token punctuation">)</span> <span class="token keyword">ENGINE</span><span class="token operator">=</span><span class="token keyword">NDB</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
Suppose there occur the two simultaneous transactions on the two
clusters. On cluster
<span class="emphasis">
<em>
A
</em>
</span>
, we create a new
department, then move employee number 999 into that department,
using the following SQL statements:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa26697415"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">BEGIN</span><span class="token punctuation">;</span>
<span class="token keyword">INSERT</span> <span class="token keyword">INTO</span> department <span class="token keyword">VALUES</span> <span class="token punctuation">(</span><span class="token number">4</span><span class="token punctuation">,</span> <span class="token string">"New project"</span><span class="token punctuation">,</span> <span class="token number">1</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token keyword"></span><em><span class="token keyword">UPDATE</span> employee <span class="token keyword">SET</span> dept <span class="token operator">=</span> <span class="token number">4</span> <span class="token keyword">WHERE</span> id <span class="token operator">=</span> <span class="token number">999</span><span class="token punctuation">;</span></em><span class="token punctuation"></span>
<span class="token keyword">COMMIT</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
At the same time, on cluster
<span class="emphasis">
<em>
B
</em>
</span>
, another
transaction reads from
<code class="literal">
employee
</code>
, as shown
here:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa66938835"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">BEGIN</span><span class="token punctuation">;</span>
<span class="token keyword"></span><em><span class="token keyword">SELECT</span> <span class="token keyword">name</span> <span class="token keyword">FROM</span> employee <span class="token keyword">WHERE</span> id <span class="token operator">=</span> <span class="token number">999</span><span class="token punctuation">;</span></em><span class="token punctuation"></span>
<span class="token keyword">UPDATE</span> department <span class="token keyword">SET</span> members <span class="token operator">=</span> members <span class="token operator">-</span> <span class="token number">1</span> <span class="token keyword">WHERE</span> id <span class="token operator">=</span> <span class="token number">3</span><span class="token punctuation">;</span>
<span class="token keyword">commit</span><span class="token punctuation">;</span></code></pre>
</div>
<a class="indexterm" name="idm46045085117776">
</a>
<p>
The conflicting transactions are not normally detected by the
conflict resolution mechanism, since the conflict is between a
read (
<code class="literal">
SELECT
</code>
) and an update operation. You
can circumvent this issue by executing
<a class="link" href="set-variable.html" title="15.7.6.1 SET Syntax for Variable Assignment">
<code class="literal">
SET
</code>
</a>
<a class="link" href="mysql-cluster-options-variables.html#sysvar_ndb_log_exclusive_reads">
<code class="literal">
ndb_log_exclusive_reads
</code>
</a>
<code class="literal">
= 1
</code>
on the replica cluster. Acquiring
exclusive read locks in this way causes any rows read on the
source to be flagged as needing conflict resolution on the
replica cluster. If we enable exclusive reads in this way prior
to the logging of these transactions, the read on cluster
<span class="emphasis">
<em>
B
</em>
</span>
is tracked and sent to cluster
<span class="emphasis">
<em>
A
</em>
</span>
for resolution; the conflict on the
employee row is subsequently detected and the transaction on
cluster
<span class="emphasis">
<em>
B
</em>
</span>
is aborted.
</p>
<p>
The conflict is registered in the exceptions table (on cluster
<span class="emphasis">
<em>
A
</em>
</span>
) as a
<code class="literal">
READ_ROW
</code>
operation (see
<a class="xref" href="mysql-cluster-replication-conflict-resolution.html#conflict-resolution-exceptions-table" title="Conflict Resolution Exceptions Table">
Conflict Resolution Exceptions Table
</a>
, for a
description of operation types), as shown here:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa20445179"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> id<span class="token punctuation">,</span> <span class="token keyword">NDB</span>$OP_TYPE<span class="token punctuation">,</span> <span class="token keyword">NDB</span>$CFT_CAUSE <span class="token keyword">FROM</span> employee$EX<span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> id <span class="token punctuation">|</span> NDB$OP_TYPE <span class="token punctuation">|</span> NDB$CFT_CAUSE <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span>
<span class="token output"><span class="token punctuation">|</span> 999 <span class="token punctuation">|</span> READ_ROW <span class="token punctuation">|</span> TRANS_IN_CONFLICT <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
</div>
<p>
Any existing rows found in the read operation are flagged. This
means that multiple rows resulting from the same conflict may be
logged in the exception table, as shown by examining the effects
a conflict between an update on cluster
<span class="emphasis">
<em>
A
</em>
</span>
and a read of multiple rows on cluster
<span class="emphasis">
<em>
B
</em>
</span>
from the same table in simultaneous transactions. The
transaction executed on cluster
<span class="emphasis">
<em>
A
</em>
</span>
is shown
here:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa1812013"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">BEGIN</span><span class="token punctuation">;</span>
<span class="token keyword">INSERT</span> <span class="token keyword">INTO</span> department <span class="token keyword">VALUES</span> <span class="token punctuation">(</span><span class="token number">4</span><span class="token punctuation">,</span> <span class="token string">"New project"</span><span class="token punctuation">,</span> <span class="token number">0</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token keyword"></span><em><span class="token keyword">UPDATE</span> employee <span class="token keyword">SET</span> dept <span class="token operator">=</span> <span class="token number">4</span> <span class="token keyword">WHERE</span> dept <span class="token operator">=</span> <span class="token number">3</span><span class="token punctuation">;</span></em><span class="token punctuation"></span>
<span class="token keyword">SELECT</span> <span class="token function">COUNT</span><span class="token punctuation">(</span><span class="token operator">*</span><span class="token punctuation">)</span> <span class="token keyword">INTO</span> <span class="token variable">@count</span> <span class="token keyword">FROM</span> employee <span class="token keyword">WHERE</span> dept <span class="token operator">=</span> <span class="token number">4</span><span class="token punctuation">;</span>
<span class="token keyword">UPDATE</span> department <span class="token keyword">SET</span> members <span class="token operator">=</span> <span class="token variable">@count</span> <span class="token keyword">WHERE</span> id <span class="token operator">=</span> <span class="token number">4</span><span class="token punctuation">;</span>
<span class="token keyword">COMMIT</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
Concurrently a transaction containing the statements shown here
runs on cluster
<span class="emphasis">
<em>
B
</em>
</span>
:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa63302179"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SET</span> ndb_log_exclusive_reads <span class="token operator">=</span> <span class="token number">1</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true"># Must be set if not already enabled</span>
<span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span>
<span class="token keyword">BEGIN</span><span class="token punctuation">;</span>
<span class="token keyword"></span><em><span class="token keyword">SELECT</span> <span class="token function">COUNT</span><span class="token punctuation">(</span><span class="token operator">*</span><span class="token punctuation">)</span> <span class="token keyword">INTO</span> <span class="token variable">@count</span> <span class="token keyword">FROM</span> employee <span class="token keyword">WHERE</span> dept <span class="token operator">=</span> <span class="token number">3</span> <span class="token keyword">FOR</span> <span class="token keyword">UPDATE</span><span class="token punctuation">;</span></em><span class="token punctuation"></span>
<span class="token keyword">UPDATE</span> department <span class="token keyword">SET</span> members <span class="token operator">=</span> <span class="token variable">@count</span> <span class="token keyword">WHERE</span> id <span class="token operator">=</span> <span class="token number">3</span><span class="token punctuation">;</span>
<span class="token keyword">COMMIT</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
In this case, all three rows matching the
<code class="literal">
WHERE
</code>
condition in the second
transaction's
<code class="literal">
SELECT
</code>
are read, and are
thus flagged in the exceptions table, as shown here:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa75437384"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> id<span class="token punctuation">,</span> <span class="token keyword">NDB</span>$OP_TYPE<span class="token punctuation">,</span> <span class="token keyword">NDB</span>$CFT_CAUSE <span class="token keyword">FROM</span> employee$EX<span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> id <span class="token punctuation">|</span> NDB$OP_TYPE <span class="token punctuation">|</span> NDB$CFT_CAUSE <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span>
<span class="token output"><span class="token punctuation">|</span> 998 <span class="token punctuation">|</span> READ_ROW <span class="token punctuation">|</span> TRANS_IN_CONFLICT <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 999 <span class="token punctuation">|</span> READ_ROW <span class="token punctuation">|</span> TRANS_IN_CONFLICT <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 1000 <span class="token punctuation">|</span> READ_ROW <span class="token punctuation">|</span> TRANS_IN_CONFLICT <span class="token punctuation">|</span></span>
<span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
</div>
<p>
Read tracking is performed on the basis of existing rows only. A
read based on a given condition track conflicts only of any rows
that are
<span class="emphasis">
<em>
found
</em>
</span>
and not of any rows that are
inserted in an interleaved transaction. This is similar to how
exclusive row locking is performed in a single instance of NDB
Cluster.
</p>
<p>
<a name="conflict-detection-insert-conflict-example">
</a>
<b>
Insert conflict detection and resolution example.
</b>
The following example illustrates the use of insert conflict
detection functions. We assume that we are replicating two
tables
<code class="literal">
t1
</code>
and
<code class="literal">
t2
</code>
in
database
<code class="literal">
test
</code>
, and that we wish to use
insert conflict detection with
<code class="literal">
NDB$MAX_INS()
</code>
for
<code class="literal">
t1
</code>
and
<code class="literal">
NDB$MAX_DEL_WIN_INS()
</code>
for
<code class="literal">
t2
</code>
. The two data tables are not created
until later in the setup process.
</p>
<p>
Setting up insert conflict resolution is similar to setting up
other conflict detection and resolution algorithms as shown in
the previous examples. If the
<code class="literal">
mysql.ndb_replication
</code>
table used to configure
binary logging and conflict resolution, does not already exist,
it is first necessary to create it, as shown here:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa31403342"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">TABLE</span> mysql<span class="token punctuation">.</span>ndb_replication <span class="token punctuation">(</span>
db <span class="token datatype">VARBINARY</span><span class="token punctuation">(</span><span class="token number">63</span><span class="token punctuation">)</span><span class="token punctuation">,</span>
<span class="token keyword">table_name</span> <span class="token datatype">VARBINARY</span><span class="token punctuation">(</span><span class="token number">63</span><span class="token punctuation">)</span><span class="token punctuation">,</span>
server_id <span class="token datatype">INT</span> <span class="token keyword">UNSIGNED</span><span class="token punctuation">,</span>
binlog_type <span class="token datatype">INT</span> <span class="token keyword">UNSIGNED</span><span class="token punctuation">,</span>
conflict_fn <span class="token datatype">VARBINARY</span><span class="token punctuation">(</span><span class="token number">128</span><span class="token punctuation">)</span><span class="token punctuation">,</span>
<span class="token keyword">PRIMARY</span> <span class="token keyword">KEY</span> <span class="token keyword">USING</span> <span class="token keyword">HASH</span> <span class="token punctuation">(</span>db<span class="token punctuation">,</span> <span class="token keyword">table_name</span><span class="token punctuation">,</span> server_id<span class="token punctuation">)</span>
<span class="token punctuation">)</span> <span class="token keyword">ENGINE</span><span class="token operator">=</span><span class="token keyword">NDB</span>
<span class="token keyword">PARTITION</span> <span class="token keyword">BY</span> <span class="token keyword">KEY</span><span class="token punctuation">(</span>db<span class="token punctuation">,</span><span class="token keyword">table_name</span><span class="token punctuation">)</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
The
<code class="literal">
ndb_replication
</code>
table acts on a per-table
basis; that is, we need to insert a row containing table
information, a
<code class="literal">
binlog_type
</code>
value, the
conflict resolution function to be employed, and the name of the
timestamp column (
<code class="literal">
X
</code>
) for each table to be set
up, like this:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa65410641"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">INSERT</span> <span class="token keyword">INTO</span> mysql<span class="token punctuation">.</span>ndb_replication <span class="token keyword">VALUES</span> <span class="token punctuation">(</span><span class="token string">"test"</span><span class="token punctuation">,</span> <span class="token string">"t1"</span><span class="token punctuation">,</span> <span class="token number">0</span><span class="token punctuation">,</span> <span class="token number">7</span><span class="token punctuation">,</span> <span class="token string">"NDB$MAX_INS(X)"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token keyword">INSERT</span> <span class="token keyword">INTO</span> mysql<span class="token punctuation">.</span>ndb_replication <span class="token keyword">VALUES</span> <span class="token punctuation">(</span><span class="token string">"test"</span><span class="token punctuation">,</span> <span class="token string">"t2"</span><span class="token punctuation">,</span> <span class="token number">0</span><span class="token punctuation">,</span> <span class="token number">7</span><span class="token punctuation">,</span> <span class="token string">"NDB$MAX_DEL_WIN_INS(X)"</span><span class="token punctuation">)</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
Here we have set the binlog_type as
<code class="literal">
NBT_FULL_USE_UPDATE
</code>
(
<code class="literal">
7
</code>
)
which means that full rows are always logged. See
<a class="xref" href="mysql-cluster-replication-schema.html#ndb-replication-ndb-replication" title="ndb_replication Table">
ndb_replication Table
</a>
, for other
possible values.
</p>
<p>
You can also create an exceptions table corresponding to each
<code class="literal">
NDB
</code>
table for which conflict resolution is to
be employed. An exceptions table records all rows rejected by
the conflict resolution function for a given table. Exceptions
tables for replication conflict detection for tables
<code class="literal">
t1
</code>
and
<code class="literal">
t2
</code>
can be created
using the following two SQL statements:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa33203610"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">TABLE</span> <span class="token punctuation">`</span>t1$EX<span class="token punctuation">`</span> <span class="token punctuation">(</span>
<span class="token keyword">NDB</span>$server_id <span class="token datatype">INT</span> <span class="token keyword">UNSIGNED</span><span class="token punctuation">,</span>
<span class="token keyword">NDB</span>$source_server_id <span class="token datatype">INT</span> <span class="token keyword">UNSIGNED</span><span class="token punctuation">,</span>
<span class="token keyword">NDB</span>$source_epoch <span class="token datatype">BIGINT</span> <span class="token keyword">UNSIGNED</span><span class="token punctuation">,</span>
<span class="token keyword">NDB</span>$count <span class="token datatype">INT</span> <span class="token keyword">UNSIGNED</span><span class="token punctuation">,</span>
<span class="token keyword">NDB</span>$OP_TYPE <span class="token datatype">ENUM</span><span class="token punctuation">(</span><span class="token string">'WRITE_ROW'</span><span class="token punctuation">,</span> <span class="token string">'UPDATE_ROW'</span><span class="token punctuation">,</span> <span class="token string">'DELETE_ROW'</span><span class="token punctuation">,</span>
<span class="token string">'REFRESH_ROW'</span><span class="token punctuation">,</span> <span class="token string">'READ_ROW'</span><span class="token punctuation">)</span> <span class="token operator">NOT</span> <span class="token boolean">NULL</span><span class="token punctuation">,</span>
<span class="token keyword">NDB</span>$CFT_CAUSE <span class="token datatype">ENUM</span><span class="token punctuation">(</span><span class="token string">'ROW_DOES_NOT_EXIST'</span><span class="token punctuation">,</span> <span class="token string">'ROW_ALREADY_EXISTS'</span><span class="token punctuation">,</span>
<span class="token string">'DATA_IN_CONFLICT'</span><span class="token punctuation">,</span> <span class="token string">'TRANS_IN_CONFLICT'</span><span class="token punctuation">)</span> <span class="token operator">NOT</span> <span class="token boolean">NULL</span><span class="token punctuation">,</span>
a <span class="token datatype">INT</span> <span class="token operator">NOT</span> <span class="token boolean">NULL</span><span class="token punctuation">,</span>
<span class="token keyword">PRIMARY</span> <span class="token keyword">KEY</span><span class="token punctuation">(</span><span class="token keyword">NDB</span>$server_id<span class="token punctuation">,</span> <span class="token keyword">NDB</span>$source_server_id<span class="token punctuation">,</span>
<span class="token keyword">NDB</span>$source_epoch<span class="token punctuation">,</span> <span class="token keyword">NDB</span>$count<span class="token punctuation">)</span>
<span class="token punctuation">)</span> <span class="token keyword">ENGINE</span><span class="token operator">=</span><span class="token keyword">NDB</span><span class="token punctuation">;</span>
<span class="token keyword">CREATE</span> <span class="token keyword">TABLE</span> <span class="token punctuation">`</span>t2$EX<span class="token punctuation">`</span> <span class="token punctuation">(</span>
<span class="token keyword">NDB</span>$server_id <span class="token datatype">INT</span> <span class="token keyword">UNSIGNED</span><span class="token punctuation">,</span>
<span class="token keyword">NDB</span>$source_server_id <span class="token datatype">INT</span> <span class="token keyword">UNSIGNED</span><span class="token punctuation">,</span>
<span class="token keyword">NDB</span>$source_epoch <span class="token datatype">BIGINT</span> <span class="token keyword">UNSIGNED</span><span class="token punctuation">,</span>
<span class="token keyword">NDB</span>$count <span class="token datatype">INT</span> <span class="token keyword">UNSIGNED</span><span class="token punctuation">,</span>
<span class="token keyword">NDB</span>$OP_TYPE <span class="token datatype">ENUM</span><span class="token punctuation">(</span><span class="token string">'WRITE_ROW'</span><span class="token punctuation">,</span> <span class="token string">'UPDATE_ROW'</span><span class="token punctuation">,</span> <span class="token string">'DELETE_ROW'</span><span class="token punctuation">,</span>
<span class="token string">'REFRESH_ROW'</span><span class="token punctuation">,</span> <span class="token string">'READ_ROW'</span><span class="token punctuation">)</span> <span class="token operator">NOT</span> <span class="token boolean">NULL</span><span class="token punctuation">,</span>
<span class="token keyword">NDB</span>$CFT_CAUSE <span class="token datatype">ENUM</span><span class="token punctuation">(</span> <span class="token string">'ROW_DOES_NOT_EXIST'</span><span class="token punctuation">,</span> <span class="token string">'ROW_ALREADY_EXISTS'</span><span class="token punctuation">,</span>
<span class="token string">'DATA_IN_CONFLICT'</span><span class="token punctuation">,</span> <span class="token string">'TRANS_IN_CONFLICT'</span><span class="token punctuation">)</span> <span class="token operator">NOT</span> <span class="token boolean">NULL</span><span class="token punctuation">,</span>
a <span class="token datatype">INT</span> <span class="token operator">NOT</span> <span class="token boolean">NULL</span><span class="token punctuation">,</span>
<span class="token keyword">PRIMARY</span> <span class="token keyword">KEY</span><span class="token punctuation">(</span><span class="token keyword">NDB</span>$server_id<span class="token punctuation">,</span> <span class="token keyword">NDB</span>$source_server_id<span class="token punctuation">,</span>
<span class="token keyword">NDB</span>$source_epoch<span class="token punctuation">,</span> <span class="token keyword">NDB</span>$count<span class="token punctuation">)</span>
<span class="token punctuation">)</span> <span class="token keyword">ENGINE</span><span class="token operator">=</span><span class="token keyword">NDB</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
Finally, after creating the exception tables just shown, you can
create the data tables to be replicated and subject to conflict
resolution control, using the following two SQL statements:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa19175539"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">TABLE</span> t1 <span class="token punctuation">(</span>
a <span class="token datatype">INT</span> <span class="token keyword">PRIMARY</span> <span class="token keyword">KEY</span><span class="token punctuation">,</span>
b <span class="token datatype">VARCHAR</span><span class="token punctuation">(</span><span class="token number">32</span><span class="token punctuation">)</span><span class="token punctuation">,</span>
X <span class="token datatype">INT</span> <span class="token keyword">UNSIGNED</span>
<span class="token punctuation">)</span> <span class="token keyword">ENGINE</span><span class="token operator">=</span><span class="token keyword">NDB</span><span class="token punctuation">;</span>
<span class="token keyword">CREATE</span> <span class="token keyword">TABLE</span> t2 <span class="token punctuation">(</span>
a <span class="token datatype">INT</span> <span class="token keyword">PRIMARY</span> <span class="token keyword">KEY</span><span class="token punctuation">,</span>
b <span class="token datatype">VARCHAR</span><span class="token punctuation">(</span><span class="token number">32</span><span class="token punctuation">)</span><span class="token punctuation">,</span>
X <span class="token datatype">INT</span> <span class="token keyword">UNSIGNED</span>
<span class="token punctuation">)</span> <span class="token keyword">ENGINE</span><span class="token operator">=</span><span class="token keyword">NDB</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
For each table, the
<code class="literal">
X
</code>
column is used as the
timestamp column.
</p>
<p>
Once created on the source,
<code class="literal">
t1
</code>
and
<code class="literal">
t2
</code>
are replicated and can be assumed to exist
on both the source and the replica. In the remainder of this
example, we use
<code class="literal">
mysqlS>
</code>
to indicate a
<a class="link" href="mysql.html" title="6.5.1 mysql — The MySQL Command-Line Client">
<span class="command">
<strong>
mysql
</strong>
</span>
</a>
client connected to the source, and
<code class="literal">
mysqlR>
</code>
to indicate a
<a class="link" href="mysql.html" title="6.5.1 mysql — The MySQL Command-Line Client">
<span class="command">
<strong>
mysql
</strong>
</span>
</a>
client running on the replica.
</p>
<p>
First we insert one row each into the tables on the source, like
this:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa8547896"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysqlS></span> <span class="token keyword">INSERT</span> <span class="token keyword">INTO</span> t1 <span class="token keyword">VALUES</span> <span class="token punctuation">(</span><span class="token number">1</span><span class="token punctuation">,</span> <span class="token string">'Initial X=1'</span><span class="token punctuation">,</span> <span class="token number">1</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output">Query OK, 1 row affected (0.01 sec)</span>
<span class="token prompt">mysqlS></span> <span class="token keyword">INSERT</span> <span class="token keyword">INTO</span> t2 <span class="token keyword">VALUES</span> <span class="token punctuation">(</span><span class="token number">1</span><span class="token punctuation">,</span> <span class="token string">'Initial X=1'</span><span class="token punctuation">,</span> <span class="token number">1</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output">Query OK, 1 row affected (0.01 sec)</span></code></pre>
</div>
<p>
We can be certain that these two rows are replicated without
causing any conflicts, since the tables on the replica did not
contain any rows prior to issuing the
<a class="link" href="insert.html" title="15.2.7 INSERT Statement">
<code class="literal">
INSERT
</code>
</a>
statements on the source.
We can verify this by selecting from the tables on the replica
as shown here:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa18166758"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql">mysqlR<span class="token operator">></span> <span class="token keyword">TABLE</span> t1 <span class="token keyword">ORDER</span> <span class="token keyword">BY</span> a<span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> a <span class="token punctuation">|</span> b <span class="token punctuation">|</span> X <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 1 <span class="token punctuation">|</span> Initial X=1 <span class="token punctuation">|</span> 1 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output">1 row in set (0.00 sec)</span>
mysqlR<span class="token operator">></span> <span class="token keyword">TABLE</span> t2 <span class="token keyword">ORDER</span> <span class="token keyword">BY</span> a<span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> a <span class="token punctuation">|</span> b <span class="token punctuation">|</span> X <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 1 <span class="token punctuation">|</span> Initial X=1 <span class="token punctuation">|</span> 1 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output">1 row in set (0.00 sec)</span></code></pre>
</div>
<p>
Next, we insert new rows into the tables on the replica, like
this:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa86812150"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql">mysqlR<span class="token operator">></span> <span class="token keyword">INSERT</span> <span class="token keyword">INTO</span> t1 <span class="token keyword">VALUES</span> <span class="token punctuation">(</span><span class="token number">2</span><span class="token punctuation">,</span> <span class="token string">'Replica X=2'</span><span class="token punctuation">,</span> <span class="token number">2</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output">Query OK, 1 row affected (0.01 sec)</span>
mysqlR<span class="token operator">></span> <span class="token keyword">INSERT</span> <span class="token keyword">INTO</span> t2 <span class="token keyword">VALUES</span> <span class="token punctuation">(</span><span class="token number">2</span><span class="token punctuation">,</span> <span class="token string">'Replica X=2'</span><span class="token punctuation">,</span> <span class="token number">2</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output">Query OK, 1 row affected (0.01 sec)</span></code></pre>
</div>
<p>
Now we insert conflicting rows into the tables on the source
having greater timestamp (
<code class="literal">
X
</code>
) column values,
using the statements shown here:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa25298843"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysqlS></span> <span class="token keyword">INSERT</span> <span class="token keyword">INTO</span> t1 <span class="token keyword">VALUES</span> <span class="token punctuation">(</span><span class="token number">2</span><span class="token punctuation">,</span> <span class="token string">'Replica X=20'</span><span class="token punctuation">,</span> <span class="token number">20</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output">Query OK, 1 row affected (0.01 sec)</span>
<span class="token prompt">mysqlS></span> <span class="token keyword">INSERT</span> <span class="token keyword">INTO</span> t2 <span class="token keyword">VALUES</span> <span class="token punctuation">(</span><span class="token number">2</span><span class="token punctuation">,</span> <span class="token string">'Replica X=20'</span><span class="token punctuation">,</span> <span class="token number">20</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output">Query OK, 1 row affected (0.01 sec)</span></code></pre>
</div>
<p>
Now we observe the results by selecting (again) from both tables
on the replica, as shown here:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa39998865"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql">mysqlR<span class="token operator">></span> <span class="token keyword">TABLE</span> t1 <span class="token keyword">ORDER</span> <span class="token keyword">BY</span> a<span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> a <span class="token punctuation">|</span> b <span class="token punctuation">|</span> X <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 1 <span class="token punctuation">|</span> Initial X=1 <span class="token punctuation">|</span> 1 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 2 <span class="token punctuation">|</span> Source X=20 <span class="token punctuation">|</span> 20 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output">2 rows in set (0.00 sec)</span>
mysqlR<span class="token operator">></span> <span class="token keyword">TABLE</span> t2 <span class="token keyword">ORDER</span> <span class="token keyword">BY</span> a<span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> a <span class="token punctuation">|</span> b <span class="token punctuation">|</span> X <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 1 <span class="token punctuation">|</span> Initial X=1 <span class="token punctuation">|</span> 1 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 1 <span class="token punctuation">|</span> Source X=20 <span class="token punctuation">|</span> 20 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output">2 rows in set (0.00 sec)</span></code></pre>
</div>
<p>
The rows inserted on the source, having greater timestamps than
those in the conflicting rows on the replica, have replaced
those rows. On the replica, we next insert two new rows which do
not conflict with any existing rows in
<code class="literal">
t1
</code>
or
<code class="literal">
t2
</code>
, like this:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-simple"><div class="docs-select-all right" id="sa66155596"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-simple">mysqlR<span class="token operator">></span> INSERT INTO t1 VALUES <span class="token punctuation">(</span>3<span class="token punctuation">,</span> 'Replica X<span class="token operator">=</span>30'<span class="token punctuation">,</span> 30<span class="token punctuation">)</span><span class="token punctuation">;</span>
Query OK<span class="token punctuation">,</span> 1 row affected <span class="token punctuation">(</span>0<span class="token punctuation">.</span>01 sec<span class="token punctuation">)</span>
mysqlR<span class="token operator">></span> INSERT INTO t2 VALUES <span class="token punctuation">(</span>3<span class="token punctuation">,</span> 'Replica X<span class="token operator">=</span>30'<span class="token punctuation">,</span> 30<span class="token punctuation">)</span><span class="token punctuation">;</span>
Query OK<span class="token punctuation">,</span> 1 row affected <span class="token punctuation">(</span>0<span class="token punctuation">.</span>01 sec<span class="token punctuation">)</span></code></pre>
</div>
<p>
Inserting more rows on the source with the same primary key
value (
<code class="literal">
3
</code>
) brings about conflicts as before,
but this time we use a value for the timestamp column less than
that in same column in the conflicting rows on the replica.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa87319614"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysqlS></span> <span class="token keyword">INSERT</span> <span class="token keyword">INTO</span> t1 <span class="token keyword">VALUES</span> <span class="token punctuation">(</span><span class="token number">3</span><span class="token punctuation">,</span> <span class="token string">'Source X=3'</span><span class="token punctuation">,</span> <span class="token number">3</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output">Query OK, 1 row affected (0.01 sec)</span>
<span class="token prompt">mysqlS></span> <span class="token keyword">INSERT</span> <span class="token keyword">INTO</span> t2 <span class="token keyword">VALUES</span> <span class="token punctuation">(</span><span class="token number">3</span><span class="token punctuation">,</span> <span class="token string">'Source X=3'</span><span class="token punctuation">,</span> <span class="token number">3</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output">Query OK, 1 row affected (0.01 sec)</span></code></pre>
</div>
<p>
We can see by querying the tables that both inserts from the
source were rejected by the replica, and the rows inserted on
the replica previously have not been overwritten, as shown here
in the
<a class="link" href="mysql.html" title="6.5.1 mysql — The MySQL Command-Line Client">
<span class="command">
<strong>
mysql
</strong>
</span>
</a>
client on the replica:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa6869965"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql">mysqlR<span class="token operator">></span> <span class="token keyword">TABLE</span> t1 <span class="token keyword">ORDER</span> <span class="token keyword">BY</span> a<span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> a <span class="token punctuation">|</span> b <span class="token punctuation">|</span> X <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 1 <span class="token punctuation">|</span> Initial X=1 <span class="token punctuation">|</span> 1 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 2 <span class="token punctuation">|</span> Source X=20 <span class="token punctuation">|</span> 20 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 3 <span class="token punctuation">|</span> Replica X=30 <span class="token punctuation">|</span> 30 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output">3 rows in set (0.00 sec)</span>
mysqlR<span class="token operator">></span> <span class="token keyword">TABLE</span> t2 <span class="token keyword">ORDER</span> <span class="token keyword">BY</span> a<span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> a <span class="token punctuation">|</span> b <span class="token punctuation">|</span> X <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 1 <span class="token punctuation">|</span> Initial X=1 <span class="token punctuation">|</span> 1 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 2 <span class="token punctuation">|</span> Source X=20 <span class="token punctuation">|</span> 20 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 3 <span class="token punctuation">|</span> Replica X=30 <span class="token punctuation">|</span> 30 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output">3 rows in set (0.00 sec)</span></code></pre>
</div>
<p>
You can see information about the rows that were rejected in the
exception tables, as shown here:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa58066778"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql">mysqlR<span class="token operator">></span> <span class="token keyword">SELECT</span> <span class="token keyword">NDB</span>$server_id<span class="token punctuation">,</span> <span class="token keyword">NDB</span>$source_server_id<span class="token punctuation">,</span> <span class="token keyword">NDB</span>$count<span class="token punctuation">,</span>
<span class="token operator">></span> <span class="token keyword">NDB</span>$OP_TYPE<span class="token punctuation">,</span> <span class="token keyword">NDB</span>$CFT_CAUSE<span class="token punctuation">,</span> a
<span class="token operator">></span> <span class="token keyword">FROM</span> t1$EX
<span class="token operator">></span> <span class="token keyword">ORDER</span> <span class="token keyword">BY</span> <span class="token keyword">NDB</span>$count\G
<span class="token output"><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span> 1. row <span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span>
NDB$server_id <span class="token punctuation">:</span> 2
NDB$source_server_id<span class="token punctuation">:</span> 1
NDB$count <span class="token punctuation">:</span> 1
NDB$OP_TYPE <span class="token punctuation">:</span> WRITE_ROW
NDB$CFT_CAUSE <span class="token punctuation">:</span> DATA_IN_CONFLICT
a <span class="token punctuation">:</span> 3
</span><span class="token output">1 row in set (0.00 sec)</span>
mysqlR<span class="token operator">></span> <span class="token keyword">SELECT</span> <span class="token keyword">NDB</span>$server_id<span class="token punctuation">,</span> <span class="token keyword">NDB</span>$source_server_id<span class="token punctuation">,</span> <span class="token keyword">NDB</span>$count<span class="token punctuation">,</span>
<span class="token operator">></span> <span class="token keyword">NDB</span>$OP_TYPE<span class="token punctuation">,</span> <span class="token keyword">NDB</span>$CFT_CAUSE<span class="token punctuation">,</span> a
<span class="token operator">></span> <span class="token keyword">FROM</span> t2$EX
<span class="token operator">></span> <span class="token keyword">ORDER</span> <span class="token keyword">BY</span> <span class="token keyword">NDB</span>$count\G
<span class="token output"><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span> 1. row <span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span>
NDB$server_id <span class="token punctuation">:</span> 2
NDB$source_server_id<span class="token punctuation">:</span> 1
NDB$count <span class="token punctuation">:</span> 1
NDB$OP_TYPE <span class="token punctuation">:</span> WRITE_ROW
NDB$CFT_CAUSE <span class="token punctuation">:</span> DATA_IN_CONFLICT
a <span class="token punctuation">:</span> 3
</span><span class="token output">1 row in set (0.00 sec)</span></code></pre>
</div>
<p>
As we saw earlier, no other rows inserted on the source were
rejected by the replica, only those rows having a lesser
timestamp value than the rows in conflict on the replica.
</p>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/user-variables.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h2 class="title">
<a name="user-variables">
</a>
11.4 User-Defined Variables
</h2>
</div>
</div>
</div>
<a class="indexterm" name="idm46045218692656">
</a>
<a class="indexterm" name="idm46045218691168">
</a>
<a class="indexterm" name="idm46045218690096">
</a>
<a class="indexterm" name="idm46045218688608">
</a>
<a class="indexterm" name="idm46045218687536">
</a>
<a class="indexterm" name="idm46045218686464">
</a>
<p>
You can store a value in a user-defined variable in one statement
and refer to it later in another statement. This enables you to
pass values from one statement to another.
</p>
<p>
User variables are written as
<code class="literal">
@
<em class="replaceable">
<code>
var_name
</code>
</em>
</code>
, where the
variable name
<em class="replaceable">
<code>
var_name
</code>
</em>
consists of
alphanumeric characters,
<code class="literal">
.
</code>
,
<code class="literal">
_
</code>
, and
<code class="literal">
$
</code>
. A user variable
name can contain other characters if you quote it as a string or
identifier (for example,
<code class="literal">
@'my-var'
</code>
,
<code class="literal">
@"my-var"
</code>
, or
<code class="literal">
@`my-var`
</code>
).
</p>
<p>
User-defined variables are session specific. A user variable
defined by one client cannot be seen or used by other clients.
(Exception: A user with access to the Performance Schema
<a class="link" href="performance-schema-user-variable-tables.html" title="29.12.10 Performance Schema User-Defined Variable Tables">
<code class="literal">
user_variables_by_thread
</code>
</a>
table can
see all user variables for all sessions.) All variables for a
given client session are automatically freed when that client
exits.
</p>
<p>
User variable names are not case-sensitive. Names have a maximum
length of 64 characters.
</p>
<p>
One way to set a user-defined variable is by issuing a
<a class="link" href="set-variable.html" title="15.7.6.1 SET Syntax for Variable Assignment">
<code class="literal">
SET
</code>
</a>
statement:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa47432904"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SET</span> <span class="token variable">@<em class="replaceable">var_name</em></span> <span class="token operator">=</span> <em class="replaceable">expr</em> <span class="token punctuation">[</span><span class="token punctuation">,</span> <span class="token variable">@<em class="replaceable">var_name</em></span> <span class="token operator">=</span> <em class="replaceable">expr</em><span class="token punctuation">]</span> <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span></code></pre>
</div>
<p>
For
<a class="link" href="set-variable.html" title="15.7.6.1 SET Syntax for Variable Assignment">
<code class="literal">
SET
</code>
</a>
,
either
<a class="link" href="assignment-operators.html#operator_assign-equal">
<code class="literal">
=
</code>
</a>
or
<a class="link" href="assignment-operators.html#operator_assign-value">
<code class="literal">
:=
</code>
</a>
can be
used as the assignment operator.
</p>
<p>
User variables can be assigned a value from a limited set of data
types: integer, decimal, floating-point, binary or nonbinary
string, or
<code class="literal">
NULL
</code>
value. Assignment of decimal
and real values does not preserve the precision or scale of the
value. A value of a type other than one of the permissible types
is converted to a permissible type. For example, a value having a
temporal or spatial data type is converted to a binary string. A
value having the
<a class="link" href="json.html" title="13.5 The JSON Data Type">
<code class="literal">
JSON
</code>
</a>
data type is
converted to a string with a character set of
<code class="literal">
utf8mb4
</code>
and a collation of
<code class="literal">
utf8mb4_bin
</code>
.
</p>
<p>
If a user variable is assigned a nonbinary (character) string
value, it has the same character set and collation as the string.
The coercibility of user variables is implicit. (This is the same
coercibility as for table column values.)
</p>
<p>
Hexadecimal or bit values assigned to user variables are treated
as binary strings. To assign a hexadecimal or bit value as a
number to a user variable, use it in numeric context. For example,
add 0 or use
<a class="link" href="cast-functions.html#function_cast">
<code class="literal">
CAST(... AS UNSIGNED)
</code>
</a>
:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa68395829"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SET</span> <span class="token variable">@v1</span> <span class="token operator">=</span> X<span class="token string">'41'</span><span class="token punctuation">;</span>
<span class="token prompt">mysql></span> <span class="token keyword">SET</span> <span class="token variable">@v2</span> <span class="token operator">=</span> X<span class="token string">'41'</span><span class="token operator">+</span><span class="token number">0</span><span class="token punctuation">;</span>
<span class="token prompt">mysql></span> <span class="token keyword">SET</span> <span class="token variable">@v3</span> <span class="token operator">=</span> <span class="token function">CAST</span><span class="token punctuation">(</span>X<span class="token string">'41'</span> <span class="token keyword">AS</span> <span class="token keyword">UNSIGNED</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token variable">@v1</span><span class="token punctuation">,</span> <span class="token variable">@v2</span><span class="token punctuation">,</span> <span class="token variable">@v3</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> @v1 <span class="token punctuation">|</span> @v2 <span class="token punctuation">|</span> @v3 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> A <span class="token punctuation">|</span> 65 <span class="token punctuation">|</span> 65 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token prompt">mysql></span> <span class="token keyword">SET</span> <span class="token variable">@v1</span> <span class="token operator">=</span> b<span class="token string">'1000001'</span><span class="token punctuation">;</span>
<span class="token prompt">mysql></span> <span class="token keyword">SET</span> <span class="token variable">@v2</span> <span class="token operator">=</span> b<span class="token string">'1000001'</span><span class="token operator">+</span><span class="token number">0</span><span class="token punctuation">;</span>
<span class="token prompt">mysql></span> <span class="token keyword">SET</span> <span class="token variable">@v3</span> <span class="token operator">=</span> <span class="token function">CAST</span><span class="token punctuation">(</span>b<span class="token string">'1000001'</span> <span class="token keyword">AS</span> <span class="token keyword">UNSIGNED</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token variable">@v1</span><span class="token punctuation">,</span> <span class="token variable">@v2</span><span class="token punctuation">,</span> <span class="token variable">@v3</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> @v1 <span class="token punctuation">|</span> @v2 <span class="token punctuation">|</span> @v3 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> A <span class="token punctuation">|</span> 65 <span class="token punctuation">|</span> 65 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
</div>
<p>
If the value of a user variable is selected in a result set, it is
returned to the client as a string.
</p>
<p>
If you refer to a variable that has not been initialized, it has a
value of
<code class="literal">
NULL
</code>
and a type of string.
</p>
<p>
A reference to a user variable in a prepared statement has its
type determined when the statement is first prepared, and retains
this type each time the statement is executed thereafter.
Similarly, the type of a user variable employed in a statement
within a stored procedure is determined the first time the stored
procedure is invoked, and retains this type with each subsequent
invocation.
</p>
<p>
User variables may be used in most contexts where expressions are
permitted. This does not currently include contexts that
explicitly require a literal value, such as in the
<code class="literal">
LIMIT
</code>
clause of a
<a class="link" href="select.html" title="15.2.13 SELECT Statement">
<code class="literal">
SELECT
</code>
</a>
statement, or the
<code class="literal">
IGNORE
<em class="replaceable">
<code>
N
</code>
</em>
LINES
</code>
clause of a
<a class="link" href="load-data.html" title="15.2.9 LOAD DATA Statement">
<code class="literal">
LOAD DATA
</code>
</a>
statement.
</p>
<p>
Previous releases of MySQL made it possible to assign a value to a
user variable in statements other than
<a class="link" href="set-variable.html" title="15.7.6.1 SET Syntax for Variable Assignment">
<code class="literal">
SET
</code>
</a>
. This
functionality is supported in MySQL 8.4 for backward
compatibility but is subject to removal in a future release of
MySQL.
</p>
<p>
When making an assignment in this way, you must use
<a class="link" href="assignment-operators.html#operator_assign-value">
<code class="literal">
:=
</code>
</a>
as the
assignment operator;
<code class="literal">
=
</code>
is treated as the
comparison operator in statements other than
<a class="link" href="set-variable.html" title="15.7.6.1 SET Syntax for Variable Assignment">
<code class="literal">
SET
</code>
</a>
.
</p>
<p>
The order of evaluation for expressions involving user variables
is undefined. For example, there is no guarantee that
<code class="literal">
SELECT @a, @a:=@a+1
</code>
evaluates
<code class="literal">
@a
</code>
first and then performs the assignment.
</p>
<p>
In addition, the default result type of a variable is based on its
type at the beginning of the statement. This may have unintended
effects if a variable holds a value of one type at the beginning
of a statement in which it is also assigned a new value of a
different type.
</p>
<p>
To avoid problems with this behavior, either do not assign a value
to and read the value of the same variable within a single
statement, or else set the variable to
<code class="literal">
0
</code>
,
<code class="literal">
0.0
</code>
, or
<code class="literal">
''
</code>
to define its
type before you use it.
</p>
<p>
<code class="literal">
HAVING
</code>
,
<code class="literal">
GROUP BY
</code>
, and
<code class="literal">
ORDER BY
</code>
, when referring to a variable that is
assigned a value in the select expression list do not work as
expected because the expression is evaluated on the client and
thus can use stale column values from a previous row.
</p>
<p>
User variables are intended to provide data values. They cannot be
used directly in an SQL statement as an identifier or as part of
an identifier, such as in contexts where a table or database name
is expected, or as a reserved word such as
<a class="link" href="select.html" title="15.2.13 SELECT Statement">
<code class="literal">
SELECT
</code>
</a>
. This is true even if the
variable is quoted, as shown in the following example:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa52236240"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> c1 <span class="token keyword">FROM</span> t<span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> c1 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 0 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 1 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output">2 rows in set (0.00 sec)</span>
<span class="token prompt">mysql></span> <span class="token keyword">SET</span> <span class="token variable">@col</span> <span class="token operator">=</span> <span class="token string">"c1"</span><span class="token punctuation">;</span>
<span class="token output">Query OK, 0 rows affected (0.00 sec)</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token variable">@col</span> <span class="token keyword">FROM</span> t<span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> @col <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> c1 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output">1 row in set (0.00 sec)</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token punctuation">`</span><span class="token variable">@col</span><span class="token punctuation">`</span> <span class="token keyword">FROM</span> t<span class="token punctuation">;</span>
<span class="token output">ERROR 1054 (42S22)<span class="token punctuation">:</span> Unknown column '@col' in 'field list'
</span>
<span class="token prompt">mysql></span> <span class="token keyword">SET</span> <span class="token variable">@col</span> <span class="token operator">=</span> <span class="token string">"`c1`"</span><span class="token punctuation">;</span>
<span class="token output">Query OK, 0 rows affected (0.00 sec)</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token variable">@col</span> <span class="token keyword">FROM</span> t<span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> @col <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> `c1` <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output">1 row in set (0.00 sec)</span></code></pre>
</div>
<p>
An exception to this principle that user variables cannot be used
to provide identifiers, is when you are constructing a string for
use as a prepared statement to execute later. In this case, user
variables can be used to provide any part of the statement. The
following example illustrates how this can be done:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa46072929"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SET</span> <span class="token variable">@c</span> <span class="token operator">=</span> <span class="token string">"c1"</span><span class="token punctuation">;</span>
<span class="token output">Query OK, 0 rows affected (0.00 sec)</span>
<span class="token prompt">mysql></span> <span class="token keyword">SET</span> <span class="token variable">@s</span> <span class="token operator">=</span> <span class="token function">CONCAT</span><span class="token punctuation">(</span><span class="token string">"SELECT "</span><span class="token punctuation">,</span> <span class="token variable">@c</span><span class="token punctuation">,</span> <span class="token string">" FROM t"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output">Query OK, 0 rows affected (0.00 sec)</span>
<span class="token prompt">mysql></span> <span class="token keyword">PREPARE</span> stmt <span class="token keyword">FROM</span> <span class="token variable">@s</span><span class="token punctuation">;</span>
<span class="token output">Query OK, 0 rows affected (0.04 sec)</span>
Statement prepared
<span class="token prompt">mysql></span> <span class="token keyword">EXECUTE</span> stmt<span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> c1 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 0 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 1 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output">2 rows in set (0.00 sec)</span>
<span class="token prompt">mysql></span> <span class="token keyword">DEALLOCATE</span> <span class="token keyword">PREPARE</span> stmt<span class="token punctuation">;</span>
<span class="token output">Query OK, 0 rows affected (0.00 sec)</span></code></pre>
</div>
<p>
See
<a class="xref" href="sql-prepared-statements.html" title="15.5 Prepared Statements">
Section 15.5, “Prepared Statements”
</a>
, for more
information.
</p>
<p>
A similar technique can be used in application programs to
construct SQL statements using program variables, as shown here
using PHP 5:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-php"><div class="docs-select-all right" id="sa27766320"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-php"><span class="token php language-php"><span class="token delimiter important"><?php</span>
<span class="token variable">$mysqli</span> <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">mysqli</span><span class="token punctuation">(</span><span class="token string">"localhost"</span><span class="token punctuation">,</span> <span class="token string">"user"</span><span class="token punctuation">,</span> <span class="token string">"pass"</span><span class="token punctuation">,</span> <span class="token string">"test"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token keyword">if</span><span class="token punctuation">(</span> <span class="token function">mysqli_connect_errno</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">)</span>
<span class="token keyword">die</span><span class="token punctuation">(</span><span class="token string">"Connection failed: %s\n"</span><span class="token punctuation">,</span> <span class="token function">mysqli_connect_error</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token variable">$col</span> <span class="token operator">=</span> <span class="token string">"c1"</span><span class="token punctuation">;</span>
<span class="token variable">$query</span> <span class="token operator">=</span> <span class="token string">"SELECT $col FROM t"</span><span class="token punctuation">;</span>
<span class="token variable">$result</span> <span class="token operator">=</span> <span class="token variable">$mysqli</span><span class="token operator">-</span><span class="token operator">></span><span class="token function">query</span><span class="token punctuation">(</span><span class="token variable">$query</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token keyword">while</span><span class="token punctuation">(</span><span class="token variable">$row</span> <span class="token operator">=</span> <span class="token variable">$result</span><span class="token operator">-</span><span class="token operator">></span><span class="token function">fetch_assoc</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span>
<span class="token punctuation">{</span>
<span class="token keyword">echo</span> <span class="token string">"<p>"</span> <span class="token punctuation">.</span> <span class="token variable">$row</span><span class="token punctuation">[</span><span class="token string">"$col"</span><span class="token punctuation">]</span> <span class="token punctuation">.</span> <span class="token string">"</p>\n"</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>
<span class="token variable">$result</span><span class="token operator">-</span><span class="token operator">></span><span class="token function">close</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token variable">$mysqli</span><span class="token operator">-</span><span class="token operator">></span><span class="token function">close</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token delimiter important">?></span></span></code></pre>
</div>
<p>
Assembling an SQL statement in this fashion is sometimes known as
<span class="quote">
“
<span class="quote">
Dynamic SQL
</span>
”
</span>
.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/example-maximum-column.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="example-maximum-column">
</a>
5.6.1 The Maximum Value for a Column
</h3>
</div>
</div>
</div>
<p>
<span class="quote">
“
<span class="quote">
What is the highest item number?
</span>
”
</span>
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa66959070"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SELECT</span> <span class="token function">MAX</span><span class="token punctuation">(</span>article<span class="token punctuation">)</span> <span class="token keyword">AS</span> article <span class="token keyword">FROM</span> shop<span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> article <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 4 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/resetting-permissions.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="resetting-permissions">
</a>
B.3.3.2 How to Reset the Root Password
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045054083840">
</a>
<a class="indexterm" name="idm46045054082384">
</a>
<a class="indexterm" name="idm46045054080896">
</a>
<a class="indexterm" name="idm46045054079408">
</a>
<p>
If you have never assigned a
<code class="literal">
root
</code>
password
for MySQL, the server does not require a password at all for
connecting as
<code class="literal">
root
</code>
. However, this is
insecure. For instructions on assigning a password, see
<a class="xref" href="default-privileges.html" title="2.9.4 Securing the Initial MySQL Account">
Section 2.9.4, “Securing the Initial MySQL Account”
</a>
.
</p>
<p>
If you know the
<code class="literal">
root
</code>
password and want to
change it, see
<a class="xref" href="alter-user.html" title="15.7.1.1 ALTER USER Statement">
Section 15.7.1.1, “ALTER USER Statement”
</a>
, and
<a class="xref" href="set-password.html" title="15.7.1.10 SET PASSWORD Statement">
Section 15.7.1.10, “SET PASSWORD Statement”
</a>
.
</p>
<p>
If you assigned a
<code class="literal">
root
</code>
password previously
but have forgotten it, you can assign a new password. The
following sections provide instructions for Windows and Unix
and Unix-like systems, as well as generic instructions that
apply to any system.
</p>
<div class="section">
<div class="titlepage">
<div>
<div>
<h5 class="title">
<a name="resetting-permissions-windows">
</a>
B.3.3.2.1 Resetting the Root Password: Windows Systems
</h5>
</div>
</div>
</div>
<p>
On Windows, use the following procedure to reset the
password for the MySQL
<code class="literal">
'root'@'localhost'
</code>
account. To change the password for a
<code class="literal">
root
</code>
account with a different host name
part, modify the instructions to use that host name.
</p>
<div class="orderedlist">
<ol class="orderedlist" type="1">
<li class="listitem">
<p>
Log on to your system as Administrator.
</p>
</li>
<li class="listitem">
<p>
Stop the MySQL server if it is running. For a server
that is running as a Windows service, go to the Services
manager: From the
<span class="guimenu">
Start
</span>
menu, select
<span class="guisubmenu">
Control Panel
</span>
, then
<span class="guisubmenu">
Administrative Tools
</span>
, then
<span class="guimenuitem">
Services
</span>
. Find the MySQL
service in the list and stop it.
</p>
<p>
If your server is not running as a service, you may need
to use the Task Manager to force it to stop.
</p>
</li>
<li class="listitem">
<p>
Create a text file containing the password-assignment
statement on a single line. Replace the password with
the password that you want to use.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa93732034"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">ALTER</span> <span class="token keyword">USER</span> <span class="token string">'root'</span>@<span class="token string">'localhost'</span> <span class="token keyword">IDENTIFIED</span> <span class="token keyword">BY</span> <span class="token string">'MyNewPass'</span><span class="token punctuation">;</span></code></pre>
</div>
</li>
<li class="listitem">
<p>
Save the file. This example assumes that you name the
file
<code class="filename">
C:\mysql-init.txt
</code>
.
</p>
</li>
<li class="listitem">
<p>
Open a console window to get to the command prompt: From
the
<span class="guimenu">
Start
</span>
menu, select
<span class="guisubmenu">
Run
</span>
, then enter
<span class="command">
<strong>
cmd
</strong>
</span>
as the command to be run.
</p>
</li>
<li class="listitem">
<p>
Start the MySQL server with the
<a class="link" href="server-system-variables.html#sysvar_init_file">
<code class="literal">
init_file
</code>
</a>
system
variable set to name the file (notice that the backslash
in the option value is doubled):
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-terminal"><div class="docs-select-all right" id="sa8963680"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-terminal"><span class="token prompt">C:\></span><span class="token command"> cd</span> <span class="token atrule">"C:\Program Files\MySQL\MySQL Server 8.4\bin"</span>
<span class="token prompt">C:\></span><span class="token command"> mysqld</span> <span class="token constant">--init-file</span><span class="token attr-value"><span class="token punctuation">=</span>C:\\mysql-init.txt</span></code></pre>
</div>
<p>
If you installed MySQL to a different location, adjust
the
<span class="command">
<strong>
cd
</strong>
</span>
command accordingly.
</p>
<p>
The server executes the contents of the file named by
the
<a class="link" href="server-system-variables.html#sysvar_init_file">
<code class="literal">
init_file
</code>
</a>
system
variable at startup, changing the
<code class="literal">
'root'@'localhost'
</code>
account password.
</p>
<p>
To have server output to appear in the console window
rather than in a log file, add the
<a class="link" href="server-options.html#option_mysqld_console">
<code class="option">
--console
</code>
</a>
option to the
<a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
<span class="command">
<strong>
mysqld
</strong>
</span>
</a>
command.
</p>
<p>
If you installed MySQL using the MySQL Installation
Wizard, you may need to specify a
<a class="link" href="option-file-options.html#option_general_defaults-file">
<code class="option">
--defaults-file
</code>
</a>
option.
For example:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-terminal"><div class="docs-select-all right" id="sa28467223"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-terminal"><span class="token prompt">C:\></span><span class="token command"> mysqld</span>
<span class="token constant">--defaults-file</span>=<span class="token atrule">"C:\\ProgramData\\MySQL\\MySQL Server 8.4\\my.ini"</span>
<span class="token constant">--init-file</span><span class="token attr-value"><span class="token punctuation">=</span>C:\\mysql-init.txt</span></code></pre>
</div>
<p>
The appropriate
<a class="link" href="option-file-options.html#option_general_defaults-file">
<code class="option">
--defaults-file
</code>
</a>
setting
can be found using the Services Manager: From the
<span class="guimenu">
Start
</span>
menu, select
<span class="guisubmenu">
Control Panel
</span>
, then
<span class="guisubmenu">
Administrative Tools
</span>
, then
<span class="guimenuitem">
Services
</span>
. Find the MySQL
service in the list, right-click it, and choose the
<code class="literal">
Properties
</code>
option. The
<code class="literal">
Path
to executable
</code>
field contains the
<a class="link" href="option-file-options.html#option_general_defaults-file">
<code class="option">
--defaults-file
</code>
</a>
setting.
</p>
</li>
<li class="listitem">
<p>
After the server has started successfully, delete
<code class="filename">
C:\mysql-init.txt
</code>
.
</p>
</li>
</ol>
</div>
<p>
You should now be able to connect to the MySQL server as
<code class="literal">
root
</code>
using the new password. Stop the
MySQL server and restart it normally. If you run the server
as a service, start it from the Windows Services window. If
you start the server manually, use whatever command you
normally use.
</p>
</div>
<div class="section">
<div class="titlepage">
<div>
<div>
<h5 class="title">
<a name="resetting-permissions-unix">
</a>
B.3.3.2.2 Resetting the Root Password: Unix and Unix-Like Systems
</h5>
</div>
</div>
</div>
<p>
On Unix, use the following procedure to reset the password
for the MySQL
<code class="literal">
'root'@'localhost'
</code>
account.
To change the password for a
<code class="literal">
root
</code>
account
with a different host name part, modify the instructions to
use that host name.
</p>
<p>
The instructions assume that you start the MySQL server from
the Unix login account that you normally use for running it.
For example, if you run the server using the
<code class="literal">
mysql
</code>
login account, you should log in as
<code class="literal">
mysql
</code>
before using the instructions.
Alternatively, you can log in as
<code class="literal">
root
</code>
,
but in this case you
<span class="emphasis">
<em>
must
</em>
</span>
start
<a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
<span class="command">
<strong>
mysqld
</strong>
</span>
</a>
with the
<a class="link" href="server-options.html#option_mysqld_user">
<code class="option">
--user=mysql
</code>
</a>
option. If you
start the server as
<code class="literal">
root
</code>
without using
<a class="link" href="server-options.html#option_mysqld_user">
<code class="option">
--user=mysql
</code>
</a>
, the server may
create
<code class="literal">
root
</code>
-owned files in the data
directory, such as log files, and these may cause
permission-related problems for future server startups. If
that happens, you must either change the ownership of the
files to
<code class="literal">
mysql
</code>
or remove them.
</p>
<div class="orderedlist">
<ol class="orderedlist" type="1">
<li class="listitem">
<p>
Log on to your system as the Unix user that the MySQL
server runs as (for example,
<code class="literal">
mysql
</code>
).
</p>
</li>
<li class="listitem">
<p>
Stop the MySQL server if it is running. Locate the
<code class="filename">
.pid
</code>
file that contains the
server's process ID. The exact location and name of this
file depend on your distribution, host name, and
configuration. Common locations are
<code class="filename">
/var/lib/mysql/
</code>
,
<code class="filename">
/var/run/mysqld/
</code>
, and
<code class="filename">
/usr/local/mysql/data/
</code>
. Generally,
the file name has an extension of
<code class="filename">
.pid
</code>
and begins with either
<code class="filename">
mysqld
</code>
or your system's host name.
</p>
<p>
Stop the MySQL server by sending a normal
<code class="literal">
kill
</code>
(not
<code class="literal">
kill -9
</code>
)
to the
<a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
<span class="command">
<strong>
mysqld
</strong>
</span>
</a>
process. Use the actual
path name of the
<code class="filename">
.pid
</code>
file in the
following command:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-terminal"><div class="docs-select-all right" id="sa34649528"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-terminal"><span class="token prompt">$> </span><span class="token command">kill</span> `cat /mysql-data-directory/host_name<span class="token punctuation">.</span>pid`</code></pre>
</div>
<p>
Use backticks (not forward quotation marks) with the
<code class="literal">
cat
</code>
command. These cause the output
of
<code class="literal">
cat
</code>
to be substituted into the
<code class="literal">
kill
</code>
command.
</p>
</li>
<li class="listitem">
<p>
Create a text file containing the password-assignment
statement on a single line. Replace the password with
the password that you want to use.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa15969542"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">ALTER</span> <span class="token keyword">USER</span> <span class="token string">'root'</span>@<span class="token string">'localhost'</span> <span class="token keyword">IDENTIFIED</span> <span class="token keyword">BY</span> <span class="token string">'MyNewPass'</span><span class="token punctuation">;</span></code></pre>
</div>
</li>
<li class="listitem">
<p>
Save the file. This example assumes that you name the
file
<code class="filename">
/home/me/mysql-init
</code>
. The file
contains the password, so do not save it where it can be
read by other users. If you are not logged in as
<code class="literal">
mysql
</code>
(the user the server runs as),
make sure that the file has permissions that permit
<code class="literal">
mysql
</code>
to read it.
</p>
</li>
<li class="listitem">
<p>
Start the MySQL server with the
<a class="link" href="server-system-variables.html#sysvar_init_file">
<code class="literal">
init_file
</code>
</a>
system
variable set to name the file:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-terminal"><div class="docs-select-all right" id="sa15834741"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-terminal"><span class="token prompt">$> </span><span class="token command">mysqld</span> <span class="token constant">--init-file</span><span class="token attr-value"><span class="token punctuation">=</span>/home/me/mysql-init</span> &</code></pre>
</div>
<p>
The server executes the contents of the file named by
the
<a class="link" href="server-system-variables.html#sysvar_init_file">
<code class="literal">
init_file
</code>
</a>
system
variable at startup, changing the
<code class="literal">
'root'@'localhost'
</code>
account password.
</p>
<p>
Other options may be necessary as well, depending on how
you normally start your server. For example,
<a class="link" href="option-file-options.html#option_general_defaults-file">
<code class="option">
--defaults-file
</code>
</a>
may be
needed before the
<a class="link" href="server-system-variables.html#sysvar_init_file">
<code class="literal">
init_file
</code>
</a>
argument.
</p>
</li>
<li class="listitem">
<p>
After the server has started successfully, delete
<code class="filename">
/home/me/mysql-init
</code>
.
</p>
</li>
</ol>
</div>
<p>
You should now be able to connect to the MySQL server as
<code class="literal">
root
</code>
using the new password. Stop the
server and restart it normally.
</p>
</div>
<div class="section">
<div class="titlepage">
<div>
<div>
<h5 class="title">
<a name="resetting-permissions-generic">
</a>
B.3.3.2.3 Resetting the Root Password: Generic Instructions
</h5>
</div>
</div>
</div>
<p>
The preceding sections provide password-resetting
instructions specifically for Windows and Unix and Unix-like
systems. Alternatively, on any platform, you can reset the
password using the
<a class="link" href="mysql.html" title="6.5.1 mysql — The MySQL Command-Line Client">
<span class="command">
<strong>
mysql
</strong>
</span>
</a>
client (but this
approach is less secure):
</p>
<div class="orderedlist">
<ol class="orderedlist" type="1">
<li class="listitem">
<p>
Stop the MySQL server if necessary, then restart it with
the
<a class="link" href="server-options.html#option_mysqld_skip-grant-tables">
<code class="option">
--skip-grant-tables
</code>
</a>
option. This enables anyone to connect without a
password and with all privileges, and disables
account-management statements such as
<a class="link" href="alter-user.html" title="15.7.1.1 ALTER USER Statement">
<code class="literal">
ALTER USER
</code>
</a>
and
<a class="link" href="set-password.html" title="15.7.1.10 SET PASSWORD Statement">
<code class="literal">
SET PASSWORD
</code>
</a>
. Because
this is insecure, if the server is started with the
<a class="link" href="server-options.html#option_mysqld_skip-grant-tables">
<code class="option">
--skip-grant-tables
</code>
</a>
option, it also disables remote connections by enabling
<a class="link" href="server-system-variables.html#sysvar_skip_networking">
<code class="literal">
skip_networking
</code>
</a>
. On
Windows platforms, this means you must also enable
<a class="link" href="server-system-variables.html#sysvar_shared_memory">
<code class="literal">
shared_memory
</code>
</a>
or
<a class="link" href="server-system-variables.html#sysvar_named_pipe">
<code class="literal">
named_pipe
</code>
</a>
; otherwise
the server cannot start.
</p>
</li>
<li class="listitem">
<p>
Connect to the MySQL server using the
<a class="link" href="mysql.html" title="6.5.1 mysql — The MySQL Command-Line Client">
<span class="command">
<strong>
mysql
</strong>
</span>
</a>
client; no password is
necessary because the server was started with
<a class="link" href="server-options.html#option_mysqld_skip-grant-tables">
<code class="option">
--skip-grant-tables
</code>
</a>
:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-terminal"><div class="docs-select-all right" id="sa2723564"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-terminal"><span class="token prompt">$> </span><span class="token command">mysql</span></code></pre>
</div>
</li>
<li class="listitem">
<p>
In the
<code class="literal">
mysql
</code>
client, tell the server
to reload the grant tables so that account-management
statements work:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa99734197"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">FLUSH</span> <span class="token keyword">PRIVILEGES</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
Then change the
<code class="literal">
'root'@'localhost'
</code>
account password. Replace the password with the password
that you want to use. To change the password for a
<code class="literal">
root
</code>
account with a different host
name part, modify the instructions to use that host
name.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa40891106"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">ALTER</span> <span class="token keyword">USER</span> <span class="token string">'root'</span>@<span class="token string">'localhost'</span> <span class="token keyword">IDENTIFIED</span> <span class="token keyword">BY</span> <span class="token string">'MyNewPass'</span><span class="token punctuation">;</span></code></pre>
</div>
</li>
</ol>
</div>
<p>
You should now be able to connect to the MySQL server as
<code class="literal">
root
</code>
using the new password. Stop the
server and restart it normally (without the
<a class="link" href="server-options.html#option_mysqld_skip-grant-tables">
<code class="option">
--skip-grant-tables
</code>
</a>
option
and without enabling the
<a class="link" href="server-system-variables.html#sysvar_skip_networking">
<code class="literal">
skip_networking
</code>
</a>
system
variable).
</p>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/lock-order-tool.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="lock-order-tool">
</a>
7.9.3 The LOCK_ORDER Tool
</h3>
</div>
</div>
</div>
<a class="indexterm" name="idm46045253561008">
</a>
<p>
The MySQL server is a multithreaded application that uses numerous
internal locking and lock-related primitives, such as mutexes,
rwlocks (including prlocks and sxlocks), conditions, and files.
Within the server, the set of lock-related objects changes with
implementation of new features and code refactoring for
performance improvements. As with any multithreaded application
that uses locking primitives, there is always a risk of
encountering a deadlock during execution when multiple locks are
held at once. For MySQL, the effect of a deadlock is catastrophic,
causing a complete loss of service.
</p>
<p>
To enable detection of lock-acquisition deadlocks and enforcement
that runtime execution is free of them, MySQL supports
<code class="literal">
LOCK_ORDER
</code>
tooling. This enables a lock-order
dependency graph to be defined as part of server design, and
server runtime checking to ensure that lock acquisition is acyclic
and that execution paths comply with the graph.
</p>
<p>
This section provides information about using the
<code class="literal">
LOCK_ORDER
</code>
tool, but only at a basic level. For
complete details, see the Lock Order section of the MySQL Server
Doxygen documentation, available at
<a class="ulink" href="/doc/index-other.html" target="_top">
https://dev.mysql.com/doc/index-other.html
</a>
.
</p>
<p>
The
<code class="literal">
LOCK_ORDER
</code>
tool is intended for debugging
the server, not for production use.
</p>
<p>
To use the
<code class="literal">
LOCK_ORDER
</code>
tool, follow this
procedure:
</p>
<div class="orderedlist">
<ol class="orderedlist" type="1">
<li class="listitem">
<p>
Build MySQL from source, configuring it with the
<a class="link" href="source-configuration-options.html#option_cmake_with_lock_order">
<code class="option">
-DWITH_LOCK_ORDER=ON
</code>
</a>
<span class="command">
<strong>
CMake
</strong>
</span>
option so that the build includes
<code class="literal">
LOCK_ORDER
</code>
tooling.
</p>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
With the
<a class="link" href="source-configuration-options.html#option_cmake_with_lock_order">
<code class="option">
WITH_LOCK_ORDER
</code>
</a>
option enabled, MySQL builds require the
<span class="command">
<strong>
flex
</strong>
</span>
program.
</p>
</div>
</li>
<li class="listitem">
<p>
To run the server with the
<code class="literal">
LOCK_ORDER
</code>
tool
enabled, enable the
<a class="link" href="lock-order-tool.html#sysvar_lock_order">
<code class="literal">
lock_order
</code>
</a>
system variable at
server startup. Several other system variables for
<code class="literal">
LOCK_ORDER
</code>
configuration are available as
well.
</p>
</li>
<li class="listitem">
<p>
For MySQL test suite operation,
<span class="command">
<strong>
mysql-test-run.pl
</strong>
</span>
has a
<code class="option">
--lock-order
</code>
option that controls whether to
enable the
<code class="literal">
LOCK_ORDER
</code>
tool during test case
execution.
</p>
</li>
</ol>
</div>
<p>
The system variables described following configure operation of
the
<code class="literal">
LOCK_ORDER
</code>
tool, assuming that MySQL has
been built to include
<code class="literal">
LOCK_ORDER
</code>
tooling. The
primary variable is
<a class="link" href="lock-order-tool.html#sysvar_lock_order">
<code class="literal">
lock_order
</code>
</a>
,
which indicates whether to enable the
<code class="literal">
LOCK_ORDER
</code>
tool at runtime:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
If
<a class="link" href="lock-order-tool.html#sysvar_lock_order">
<code class="literal">
lock_order
</code>
</a>
is disabled
(the default), no other
<code class="literal">
LOCK_ORDER
</code>
system
variables have any effect.
</p>
</li>
<li class="listitem">
<p>
If
<a class="link" href="lock-order-tool.html#sysvar_lock_order">
<code class="literal">
lock_order
</code>
</a>
is enabled, the
other system variables configure which
<code class="literal">
LOCK_ORDER
</code>
features to enable.
</p>
</li>
</ul>
</div>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
In general, it is intended that the
<code class="literal">
LOCK_ORDER
</code>
tool be configured by executing
<span class="command">
<strong>
mysql-test-run.pl
</strong>
</span>
with the
<code class="option">
--lock-order
</code>
option, and for
<span class="command">
<strong>
mysql-test-run.pl
</strong>
</span>
to set
<code class="literal">
LOCK_ORDER
</code>
system variables to appropriate
values.
</p>
</div>
<p>
All
<code class="literal">
LOCK_ORDER
</code>
system variables must be set at
server startup. At runtime, their values are visible but cannot be
changed.
</p>
<p>
Some system variables exist in pairs, such as
<a class="link" href="lock-order-tool.html#sysvar_lock_order_debug_loop">
<code class="literal">
lock_order_debug_loop
</code>
</a>
and
<a class="link" href="lock-order-tool.html#sysvar_lock_order_trace_loop">
<code class="literal">
lock_order_trace_loop
</code>
</a>
. For such
pairs, the variables are distinguished as follows when the
condition occurs with which they are associated:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
If the
<code class="literal">
_debug_
</code>
variable is enabled, a debug
assertion is raised.
</p>
</li>
<li class="listitem">
<p>
If the
<code class="literal">
_trace_
</code>
variable is enabled, an
error is printed to the logs.
</p>
</li>
</ul>
</div>
<div class="table">
<a name="idm46045253517696">
</a>
<p class="title">
<b>
Table 7.8 LOCK_ORDER System Variable Summary
</b>
</p>
<div class="table-contents">
<table frame="box" rules="all" summary="Reference for LOCK_ORDER system variables.">
<colgroup>
<col style="width: 40%"/>
<col style="width: 20%"/>
<col align="center" style="width: 20%"/>
</colgroup>
<thead>
<tr>
<th scope="col">
Variable Name
</th>
<th scope="col">
Variable Type
</th>
<th scope="col">
Variable Scope
</th>
</tr>
</thead>
<tbody>
<tr>
<th scope="row">
<a class="link" href="lock-order-tool.html#sysvar_lock_order">
lock_order
</a>
</th>
<td>
Boolean
</td>
<td>
Global
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="lock-order-tool.html#sysvar_lock_order_debug_loop">
lock_order_debug_loop
</a>
</th>
<td>
Boolean
</td>
<td>
Global
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="lock-order-tool.html#sysvar_lock_order_debug_missing_arc">
lock_order_debug_missing_arc
</a>
</th>
<td>
Boolean
</td>
<td>
Global
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="lock-order-tool.html#sysvar_lock_order_debug_missing_key">
lock_order_debug_missing_key
</a>
</th>
<td>
Boolean
</td>
<td>
Global
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="lock-order-tool.html#sysvar_lock_order_debug_missing_unlock">
lock_order_debug_missing_unlock
</a>
</th>
<td>
Boolean
</td>
<td>
Global
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="lock-order-tool.html#sysvar_lock_order_dependencies">
lock_order_dependencies
</a>
</th>
<td>
File name
</td>
<td>
Global
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="lock-order-tool.html#sysvar_lock_order_extra_dependencies">
lock_order_extra_dependencies
</a>
</th>
<td>
File name
</td>
<td>
Global
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="lock-order-tool.html#sysvar_lock_order_output_directory">
lock_order_output_directory
</a>
</th>
<td>
Directory name
</td>
<td>
Global
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="lock-order-tool.html#sysvar_lock_order_print_txt">
lock_order_print_txt
</a>
</th>
<td>
Boolean
</td>
<td>
Global
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="lock-order-tool.html#sysvar_lock_order_trace_loop">
lock_order_trace_loop
</a>
</th>
<td>
Boolean
</td>
<td>
Global
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="lock-order-tool.html#sysvar_lock_order_trace_missing_arc">
lock_order_trace_missing_arc
</a>
</th>
<td>
Boolean
</td>
<td>
Global
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="lock-order-tool.html#sysvar_lock_order_trace_missing_key">
lock_order_trace_missing_key
</a>
</th>
<td>
Boolean
</td>
<td>
Global
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="lock-order-tool.html#sysvar_lock_order_trace_missing_unlock">
lock_order_trace_missing_unlock
</a>
</th>
<td>
Boolean
</td>
<td>
Global
</td>
</tr>
</tbody>
</table>
</div>
<div class="table-contents">
<table cellpadding="0" cellspacing="0" style="position: fixed; top: 0px; display: none; left: 401px; width: 613px;">
<thead>
<tr>
<th scope="col" style="width: 306.125px;">
Variable Name
</th>
<th scope="col" style="width: 153.062px;">
Variable Type
</th>
<th scope="col" style="width: 153.078px;">
Variable Scope
</th>
</tr>
</thead>
</table>
</div>
</div>
<br class="table-break"/>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<a name="sysvar_lock_order">
</a>
<a class="link" href="lock-order-tool.html#sysvar_lock_order">
<code class="literal">
lock_order
</code>
</a>
</p>
<a class="indexterm" name="idm46045253458048">
</a>
<a class="indexterm" name="idm46045253456960">
</a>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for lock_order">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--lock-order[={OFF|ON}]
</code>
</td>
</tr>
<tr>
<th>
System Variable
</th>
<td>
<code class="literal">
<a class="link" href="lock-order-tool.html#sysvar_lock_order">
lock_order
</a>
</code>
</td>
</tr>
<tr>
<th>
Scope
</th>
<td>
Global
</td>
</tr>
<tr>
<th>
Dynamic
</th>
<td>
No
</td>
</tr>
<tr>
<th>
<a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
<code class="literal">
SET_VAR
</code>
</a>
Hint Applies
</th>
<td>
No
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
Boolean
</td>
</tr>
<tr>
<th>
Default Value
</th>
<td>
<code class="literal">
OFF
</code>
</td>
</tr>
</tbody>
</table>
</div>
<p>
Whether to enable the
<code class="literal">
LOCK_ORDER
</code>
tool at
runtime. If
<a class="link" href="lock-order-tool.html#sysvar_lock_order">
<code class="literal">
lock_order
</code>
</a>
is
disabled (the default), no other
<code class="literal">
LOCK_ORDER
</code>
system variables have any effect. If
<a class="link" href="lock-order-tool.html#sysvar_lock_order">
<code class="literal">
lock_order
</code>
</a>
is enabled, the
other system variables configure which
<code class="literal">
LOCK_ORDER
</code>
features to enable.
</p>
<p>
If
<a class="link" href="lock-order-tool.html#sysvar_lock_order">
<code class="literal">
lock_order
</code>
</a>
is enabled, an
error is raised if the server encounters a lock-acquisition
sequence that is not declared in the lock-order graph.
</p>
</li>
<li class="listitem">
<p>
<a name="sysvar_lock_order_debug_loop">
</a>
<a class="link" href="lock-order-tool.html#sysvar_lock_order_debug_loop">
<code class="literal">
lock_order_debug_loop
</code>
</a>
</p>
<a class="indexterm" name="idm46045253425840">
</a>
<a class="indexterm" name="idm46045253424800">
</a>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for lock_order_debug_loop">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--lock-order-debug-loop[={OFF|ON}]
</code>
</td>
</tr>
<tr>
<th>
System Variable
</th>
<td>
<code class="literal">
<a class="link" href="lock-order-tool.html#sysvar_lock_order_debug_loop">
lock_order_debug_loop
</a>
</code>
</td>
</tr>
<tr>
<th>
Scope
</th>
<td>
Global
</td>
</tr>
<tr>
<th>
Dynamic
</th>
<td>
No
</td>
</tr>
<tr>
<th>
<a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
<code class="literal">
SET_VAR
</code>
</a>
Hint Applies
</th>
<td>
No
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
Boolean
</td>
</tr>
<tr>
<th>
Default Value
</th>
<td>
<code class="literal">
OFF
</code>
</td>
</tr>
</tbody>
</table>
</div>
<p>
Whether the
<code class="literal">
LOCK_ORDER
</code>
tool causes a debug
assertion failure when it encounters a dependency that is
flagged as a loop in the lock-order graph.
</p>
</li>
<li class="listitem">
<p>
<a name="sysvar_lock_order_debug_missing_arc">
</a>
<a class="link" href="lock-order-tool.html#sysvar_lock_order_debug_missing_arc">
<code class="literal">
lock_order_debug_missing_arc
</code>
</a>
</p>
<a class="indexterm" name="idm46045253399424">
</a>
<a class="indexterm" name="idm46045253398320">
</a>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for lock_order_debug_missing_arc">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--lock-order-debug-missing-arc[={OFF|ON}]
</code>
</td>
</tr>
<tr>
<th>
System Variable
</th>
<td>
<code class="literal">
<a class="link" href="lock-order-tool.html#sysvar_lock_order_debug_missing_arc">
lock_order_debug_missing_arc
</a>
</code>
</td>
</tr>
<tr>
<th>
Scope
</th>
<td>
Global
</td>
</tr>
<tr>
<th>
Dynamic
</th>
<td>
No
</td>
</tr>
<tr>
<th>
<a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
<code class="literal">
SET_VAR
</code>
</a>
Hint Applies
</th>
<td>
No
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
Boolean
</td>
</tr>
<tr>
<th>
Default Value
</th>
<td>
<code class="literal">
OFF
</code>
</td>
</tr>
</tbody>
</table>
</div>
<p>
Whether the LOCK_ORDER tool causes a debug assertion failure
when it encounters a dependency that is not declared in the
lock-order graph.
</p>
</li>
<li class="listitem">
<p>
<a name="sysvar_lock_order_debug_missing_key">
</a>
<a class="link" href="lock-order-tool.html#sysvar_lock_order_debug_missing_key">
<code class="literal">
lock_order_debug_missing_key
</code>
</a>
</p>
<a class="indexterm" name="idm46045253373568">
</a>
<a class="indexterm" name="idm46045253372464">
</a>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for lock_order_debug_missing_key">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--lock-order-debug-missing-key[={OFF|ON}]
</code>
</td>
</tr>
<tr>
<th>
System Variable
</th>
<td>
<code class="literal">
<a class="link" href="lock-order-tool.html#sysvar_lock_order_debug_missing_key">
lock_order_debug_missing_key
</a>
</code>
</td>
</tr>
<tr>
<th>
Scope
</th>
<td>
Global
</td>
</tr>
<tr>
<th>
Dynamic
</th>
<td>
No
</td>
</tr>
<tr>
<th>
<a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
<code class="literal">
SET_VAR
</code>
</a>
Hint Applies
</th>
<td>
No
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
Boolean
</td>
</tr>
<tr>
<th>
Default Value
</th>
<td>
<code class="literal">
OFF
</code>
</td>
</tr>
</tbody>
</table>
</div>
<p>
Whether the
<code class="literal">
LOCK_ORDER
</code>
tool causes a debug
assertion failure when it encounters an object that is not
properly instrumented with the Performance Schema.
</p>
</li>
<li class="listitem">
<p>
<a name="sysvar_lock_order_debug_missing_unlock">
</a>
<a class="link" href="lock-order-tool.html#sysvar_lock_order_debug_missing_unlock">
<code class="literal">
lock_order_debug_missing_unlock
</code>
</a>
</p>
<a class="indexterm" name="idm46045253347008">
</a>
<a class="indexterm" name="idm46045253345904">
</a>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for lock_order_debug_missing_unlock">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--lock-order-debug-missing-unlock[={OFF|ON}]
</code>
</td>
</tr>
<tr>
<th>
System Variable
</th>
<td>
<code class="literal">
<a class="link" href="lock-order-tool.html#sysvar_lock_order_debug_missing_unlock">
lock_order_debug_missing_unlock
</a>
</code>
</td>
</tr>
<tr>
<th>
Scope
</th>
<td>
Global
</td>
</tr>
<tr>
<th>
Dynamic
</th>
<td>
No
</td>
</tr>
<tr>
<th>
<a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
<code class="literal">
SET_VAR
</code>
</a>
Hint Applies
</th>
<td>
No
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
Boolean
</td>
</tr>
<tr>
<th>
Default Value
</th>
<td>
<code class="literal">
OFF
</code>
</td>
</tr>
</tbody>
</table>
</div>
<p>
Whether the
<code class="literal">
LOCK_ORDER
</code>
tool causes a debug
assertion failure when it encounters a lock that is destroyed
while still held.
</p>
</li>
<li class="listitem">
<p>
<a name="sysvar_lock_order_dependencies">
</a>
<a class="link" href="lock-order-tool.html#sysvar_lock_order_dependencies">
<code class="literal">
lock_order_dependencies
</code>
</a>
</p>
<a class="indexterm" name="idm46045253320448">
</a>
<a class="indexterm" name="idm46045253319408">
</a>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for lock_order_dependencies">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--lock-order-dependencies=file_name
</code>
</td>
</tr>
<tr>
<th>
System Variable
</th>
<td>
<code class="literal">
<a class="link" href="lock-order-tool.html#sysvar_lock_order_dependencies">
lock_order_dependencies
</a>
</code>
</td>
</tr>
<tr>
<th>
Scope
</th>
<td>
Global
</td>
</tr>
<tr>
<th>
Dynamic
</th>
<td>
No
</td>
</tr>
<tr>
<th>
<a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
<code class="literal">
SET_VAR
</code>
</a>
Hint Applies
</th>
<td>
No
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
File name
</td>
</tr>
<tr>
<th>
Default Value
</th>
<td>
<code class="literal">
empty string
</code>
</td>
</tr>
</tbody>
</table>
</div>
<p>
The path to the
<code class="filename">
lock_order_dependencies.txt
</code>
file that
defines the server lock-order dependency graph.
</p>
<p>
It is permitted to specify no dependencies. An empty
dependency graph is used in this case.
</p>
</li>
<li class="listitem">
<p>
<a name="sysvar_lock_order_extra_dependencies">
</a>
<a class="link" href="lock-order-tool.html#sysvar_lock_order_extra_dependencies">
<code class="literal">
lock_order_extra_dependencies
</code>
</a>
</p>
<a class="indexterm" name="idm46045253293504">
</a>
<a class="indexterm" name="idm46045253292400">
</a>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for lock_order_extra_dependencies">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--lock-order-extra-dependencies=file_name
</code>
</td>
</tr>
<tr>
<th>
System Variable
</th>
<td>
<code class="literal">
<a class="link" href="lock-order-tool.html#sysvar_lock_order_extra_dependencies">
lock_order_extra_dependencies
</a>
</code>
</td>
</tr>
<tr>
<th>
Scope
</th>
<td>
Global
</td>
</tr>
<tr>
<th>
Dynamic
</th>
<td>
No
</td>
</tr>
<tr>
<th>
<a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
<code class="literal">
SET_VAR
</code>
</a>
Hint Applies
</th>
<td>
No
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
File name
</td>
</tr>
<tr>
<th>
Default Value
</th>
<td>
<code class="literal">
empty string
</code>
</td>
</tr>
</tbody>
</table>
</div>
<p>
The path to a file containing additional dependencies for the
lock-order dependency graph. This is useful to amend the
primary server dependency graph, defined in the
<code class="filename">
lock_order_dependencies.txt
</code>
file, with
additional dependencies describing the behavior of third party
code. (The alternative is to modify
<code class="filename">
lock_order_dependencies.txt
</code>
itself, which
is not encouraged.)
</p>
<p>
If this variable is not set, no secondary file is used.
</p>
</li>
<li class="listitem">
<p>
<a name="sysvar_lock_order_output_directory">
</a>
<a class="link" href="lock-order-tool.html#sysvar_lock_order_output_directory">
<code class="literal">
lock_order_output_directory
</code>
</a>
</p>
<a class="indexterm" name="idm46045253265472">
</a>
<a class="indexterm" name="idm46045253264368">
</a>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for lock_order_output_directory">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--lock-order-output-directory=dir_name
</code>
</td>
</tr>
<tr>
<th>
System Variable
</th>
<td>
<code class="literal">
<a class="link" href="lock-order-tool.html#sysvar_lock_order_output_directory">
lock_order_output_directory
</a>
</code>
</td>
</tr>
<tr>
<th>
Scope
</th>
<td>
Global
</td>
</tr>
<tr>
<th>
Dynamic
</th>
<td>
No
</td>
</tr>
<tr>
<th>
<a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
<code class="literal">
SET_VAR
</code>
</a>
Hint Applies
</th>
<td>
No
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
Directory name
</td>
</tr>
<tr>
<th>
Default Value
</th>
<td>
<code class="literal">
empty string
</code>
</td>
</tr>
</tbody>
</table>
</div>
<p>
The directory where the
<code class="literal">
LOCK_ORDER
</code>
tool
writes its logs. If this variable is not set, the default is
the current directory.
</p>
</li>
<li class="listitem">
<p>
<a name="sysvar_lock_order_print_txt">
</a>
<a class="link" href="lock-order-tool.html#sysvar_lock_order_print_txt">
<code class="literal">
lock_order_print_txt
</code>
</a>
</p>
<a class="indexterm" name="idm46045253238960">
</a>
<a class="indexterm" name="idm46045253237920">
</a>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for lock_order_print_txt">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--lock-order-print-txt[={OFF|ON}]
</code>
</td>
</tr>
<tr>
<th>
System Variable
</th>
<td>
<code class="literal">
<a class="link" href="lock-order-tool.html#sysvar_lock_order_print_txt">
lock_order_print_txt
</a>
</code>
</td>
</tr>
<tr>
<th>
Scope
</th>
<td>
Global
</td>
</tr>
<tr>
<th>
Dynamic
</th>
<td>
No
</td>
</tr>
<tr>
<th>
<a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
<code class="literal">
SET_VAR
</code>
</a>
Hint Applies
</th>
<td>
No
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
Boolean
</td>
</tr>
<tr>
<th>
Default Value
</th>
<td>
<code class="literal">
OFF
</code>
</td>
</tr>
</tbody>
</table>
</div>
<p>
Whether the
<code class="literal">
LOCK_ORDER
</code>
tool performs a
lock-order graph analysis and prints a textual report. The
report includes any lock-acquisition cycles detected.
</p>
</li>
<li class="listitem">
<p>
<a name="sysvar_lock_order_trace_loop">
</a>
<a class="link" href="lock-order-tool.html#sysvar_lock_order_trace_loop">
<code class="literal">
lock_order_trace_loop
</code>
</a>
</p>
<a class="indexterm" name="idm46045253212496">
</a>
<a class="indexterm" name="idm46045253211456">
</a>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for lock_order_trace_loop">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--lock-order-trace-loop[={OFF|ON}]
</code>
</td>
</tr>
<tr>
<th>
System Variable
</th>
<td>
<code class="literal">
<a class="link" href="lock-order-tool.html#sysvar_lock_order_trace_loop">
lock_order_trace_loop
</a>
</code>
</td>
</tr>
<tr>
<th>
Scope
</th>
<td>
Global
</td>
</tr>
<tr>
<th>
Dynamic
</th>
<td>
No
</td>
</tr>
<tr>
<th>
<a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
<code class="literal">
SET_VAR
</code>
</a>
Hint Applies
</th>
<td>
No
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
Boolean
</td>
</tr>
<tr>
<th>
Default Value
</th>
<td>
<code class="literal">
OFF
</code>
</td>
</tr>
</tbody>
</table>
</div>
<p>
Whether the
<code class="literal">
LOCK_ORDER
</code>
tool prints a trace
in the log file when it encounters a dependency that is
flagged as a loop in the lock-order graph.
</p>
</li>
<li class="listitem">
<p>
<a name="sysvar_lock_order_trace_missing_arc">
</a>
<a class="link" href="lock-order-tool.html#sysvar_lock_order_trace_missing_arc">
<code class="literal">
lock_order_trace_missing_arc
</code>
</a>
</p>
<a class="indexterm" name="idm46045253186144">
</a>
<a class="indexterm" name="idm46045253185040">
</a>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for lock_order_trace_missing_arc">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--lock-order-trace-missing-arc[={OFF|ON}]
</code>
</td>
</tr>
<tr>
<th>
System Variable
</th>
<td>
<code class="literal">
<a class="link" href="lock-order-tool.html#sysvar_lock_order_trace_missing_arc">
lock_order_trace_missing_arc
</a>
</code>
</td>
</tr>
<tr>
<th>
Scope
</th>
<td>
Global
</td>
</tr>
<tr>
<th>
Dynamic
</th>
<td>
No
</td>
</tr>
<tr>
<th>
<a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
<code class="literal">
SET_VAR
</code>
</a>
Hint Applies
</th>
<td>
No
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
Boolean
</td>
</tr>
<tr>
<th>
Default Value
</th>
<td>
<code class="literal">
ON
</code>
</td>
</tr>
</tbody>
</table>
</div>
<p>
Whether the
<code class="literal">
LOCK_ORDER
</code>
tool prints a trace
in the log file when it encounters a dependency that is not
declared in the lock-order graph.
</p>
</li>
<li class="listitem">
<p>
<a name="sysvar_lock_order_trace_missing_key">
</a>
<a class="link" href="lock-order-tool.html#sysvar_lock_order_trace_missing_key">
<code class="literal">
lock_order_trace_missing_key
</code>
</a>
</p>
<a class="indexterm" name="idm46045253159664">
</a>
<a class="indexterm" name="idm46045253158560">
</a>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for lock_order_trace_missing_key">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--lock-order-trace-missing-key[={OFF|ON}]
</code>
</td>
</tr>
<tr>
<th>
System Variable
</th>
<td>
<code class="literal">
<a class="link" href="lock-order-tool.html#sysvar_lock_order_trace_missing_key">
lock_order_trace_missing_key
</a>
</code>
</td>
</tr>
<tr>
<th>
Scope
</th>
<td>
Global
</td>
</tr>
<tr>
<th>
Dynamic
</th>
<td>
No
</td>
</tr>
<tr>
<th>
<a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
<code class="literal">
SET_VAR
</code>
</a>
Hint Applies
</th>
<td>
No
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
Boolean
</td>
</tr>
<tr>
<th>
Default Value
</th>
<td>
<code class="literal">
OFF
</code>
</td>
</tr>
</tbody>
</table>
</div>
<p>
Whether the
<code class="literal">
LOCK_ORDER
</code>
tool prints a trace
in the log file when it encounters an object that is not
properly instrumented with the Performance Schema.
</p>
</li>
<li class="listitem">
<p>
<a name="sysvar_lock_order_trace_missing_unlock">
</a>
<a class="link" href="lock-order-tool.html#sysvar_lock_order_trace_missing_unlock">
<code class="literal">
lock_order_trace_missing_unlock
</code>
</a>
</p>
<a class="indexterm" name="idm46045253133104">
</a>
<a class="indexterm" name="idm46045253132000">
</a>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for lock_order_trace_missing_unlock">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--lock-order-trace-missing-unlock[={OFF|ON}]
</code>
</td>
</tr>
<tr>
<th>
System Variable
</th>
<td>
<code class="literal">
<a class="link" href="lock-order-tool.html#sysvar_lock_order_trace_missing_unlock">
lock_order_trace_missing_unlock
</a>
</code>
</td>
</tr>
<tr>
<th>
Scope
</th>
<td>
Global
</td>
</tr>
<tr>
<th>
Dynamic
</th>
<td>
No
</td>
</tr>
<tr>
<th>
<a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
<code class="literal">
SET_VAR
</code>
</a>
Hint Applies
</th>
<td>
No
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
Boolean
</td>
</tr>
<tr>
<th>
Default Value
</th>
<td>
<code class="literal">
ON
</code>
</td>
</tr>
</tbody>
</table>
</div>
<p>
Whether the
<code class="literal">
LOCK_ORDER
</code>
tool prints a trace
in the log file when it encounters a lock that is destroyed
while still held.
</p>
</li>
</ul>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/replication-solutions-switch.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="replication-solutions-switch">
</a>
19.4.8 Switching Sources During Failover
</h3>
</div>
</div>
</div>
<p>
You can tell a replica to change to a new source using the
<a class="link" href="change-replication-source-to.html" title="15.4.2.2 CHANGE REPLICATION SOURCE TO Statement">
<code class="literal">
CHANGE REPLICATION SOURCE TO
</code>
</a>
statement. The replica does not check whether the databases on the
source are compatible with those on the replica; it simply begins
reading and executing events from the specified coordinates in the
new source's binary log. In a failover situation, all the
servers in the group are typically executing the same events from
the same binary log file, so changing the source of the events
should not affect the structure or integrity of the database,
provided that you exercise care in making the change.
</p>
<p>
Replicas should be run with binary logging enabled (the
<a class="link" href="replication-options-binary-log.html#option_mysqld_log-bin">
<code class="option">
--log-bin
</code>
</a>
option), which is the
default. If you are not using GTIDs for replication, then the
replicas should also be run with
<a class="link" href="replication-options-binary-log.html#sysvar_log_replica_updates">
<code class="option">
--log-replica-updates=OFF
</code>
</a>
(logging
replica updates is the default). In this way, the replica is ready
to become a source without restarting the replica
<a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
<span class="command">
<strong>
mysqld
</strong>
</span>
</a>
. Assume that you have the structure
shown in
<a class="xref" href="replication-solutions-switch.html#figure_replication-redundancy-before" title="Figure 19.4 Redundancy Using Replication, Initial Structure">
Figure 19.4, “Redundancy Using Replication, Initial Structure”
</a>
.
</p>
<div class="figure">
<a name="figure_replication-redundancy-before">
</a>
<p class="title">
<b>
Figure 19.4 Redundancy Using Replication, Initial Structure
</b>
</p>
<div class="figure-contents">
<div class="mediaobject">
<img alt="Two web clients direct both database reads and database writes to a single MySQL source server. The MySQL source server replicates to Replica 1, Replica 2, and Replica 3." src="images/redundancy-before.png" style="width: 100%; max-width: 374px;"/>
</div>
</div>
</div>
<br class="figure-break"/>
<p>
In this diagram, the
<code class="literal">
Source
</code>
holds the source
database, the
<code class="literal">
Replica*
</code>
hosts are replicas, and
the
<code class="literal">
Web Client
</code>
machines are issuing database
reads and writes. Web clients that issue only reads (and would
normally be connected to the replicas) are not shown, as they do
not need to switch to a new server in the event of failure. For a
more detailed example of a read/write scale-out replication
structure, see
<a class="xref" href="replication-solutions-scaleout.html" title="19.4.5 Using Replication for Scale-Out">
Section 19.4.5, “Using Replication for Scale-Out”
</a>
.
</p>
<p>
Each MySQL replica (
<code class="literal">
Replica 1
</code>
,
<code class="literal">
Replica
2
</code>
, and
<code class="literal">
Replica 3
</code>
) is a replica
running with binary logging enabled, and with
<a class="link" href="replication-options-binary-log.html#sysvar_log_replica_updates">
<code class="option">
--log-replica-updates=OFF
</code>
</a>
. Because
updates received by a replica from the source are not written to
the binary log when
<code class="option">
--log-replica-updates=OFF
</code>
is
specified, the binary log on each replica is initially empty. If
for some reason
<code class="literal">
Source
</code>
becomes unavailable, you
can pick one of the replicas to become the new source. For
example, if you pick
<code class="literal">
Replica 1
</code>
, all
<code class="literal">
Web Clients
</code>
should be redirected to
<code class="literal">
Replica 1
</code>
, which writes the updates to its
binary log.
<code class="literal">
Replica 2
</code>
and
<code class="literal">
Replica
3
</code>
should then replicate from
<code class="literal">
Replica
1
</code>
.
</p>
<p>
The reason for running the replica with
<a class="link" href="replication-options-binary-log.html#sysvar_log_replica_updates">
<code class="option">
--log-replica-updates=OFF
</code>
</a>
is to
prevent replicas from receiving updates twice in case you cause
one of the replicas to become the new source. If
<code class="literal">
Replica
1
</code>
has
<code class="option">
--log-replica-updates
</code>
enabled,
which is the default, it writes any updates that it receives from
<code class="literal">
Source
</code>
in its own binary log. This means that,
when
<code class="literal">
Replica 2
</code>
changes from
<code class="literal">
Source
</code>
to
<code class="literal">
Replica 1
</code>
as its
source, it may receive updates from
<code class="literal">
Replica 1
</code>
that it has already received from
<code class="literal">
Source
</code>
.
</p>
<p>
Make sure that all replicas have processed any statements in their
relay log. On each replica, issue
<code class="literal">
STOP REPLICA
IO_THREAD
</code>
, then check the output of
<a class="link" href="show-processlist.html" title="15.7.7.31 SHOW PROCESSLIST Statement">
<code class="literal">
SHOW PROCESSLIST
</code>
</a>
until you see
<code class="literal">
Has read all relay log
</code>
. When this is true for
all replicas, they can be reconfigured to the new setup. On the
replica
<code class="literal">
Replica 1
</code>
being promoted to become the
source, issue
<a class="link" href="stop-replica.html" title="15.4.2.5 STOP REPLICA Statement">
<code class="literal">
STOP REPLICA
</code>
</a>
and
<a class="link" href="reset-binary-logs-and-gtids.html" title="15.4.1.2 RESET BINARY LOGS AND GTIDS Statement">
<code class="literal">
RESET BINARY LOGS AND GTIDS
</code>
</a>
.
</p>
<p>
On the other replicas
<code class="literal">
Replica 2
</code>
and
<code class="literal">
Replica 3
</code>
, use
<a class="link" href="stop-replica.html" title="15.4.2.5 STOP REPLICA Statement">
<code class="literal">
STOP
REPLICA
</code>
</a>
and
<code class="literal">
CHANGE REPLICATION SOURCE TO
SOURCE_HOST='Replica1'
</code>
(where
<code class="literal">
'Replica1'
</code>
represents the real host name of
<code class="literal">
Replica 1
</code>
). To use
<a class="link" href="change-replication-source-to.html" title="15.4.2.2 CHANGE REPLICATION SOURCE TO Statement">
<code class="literal">
CHANGE
REPLICATION SOURCE TO
</code>
</a>
, add all information about how to
connect to
<code class="literal">
Replica 1
</code>
from
<code class="literal">
Replica
2
</code>
or
<code class="literal">
Replica 3
</code>
(
<em class="replaceable">
<code>
user
</code>
</em>
,
<em class="replaceable">
<code>
password
</code>
</em>
,
<em class="replaceable">
<code>
port
</code>
</em>
). When issuing the statement in
this scenario, there is no need to specify the name of the
<code class="literal">
Replica 1
</code>
binary log file or log position to
read from, since the first binary log file and position 4 are the
defaults. Finally, execute
<a class="link" href="start-replica.html" title="15.4.2.4 START REPLICA Statement">
<code class="literal">
START
REPLICA
</code>
</a>
on
<code class="literal">
Replica 2
</code>
and
<code class="literal">
Replica 3
</code>
.
</p>
<p>
Once the new replication setup is in place, you need to tell each
<code class="literal">
Web Client
</code>
to direct its statements to
<code class="literal">
Replica 1
</code>
. From that point on, all updates sent
by
<code class="literal">
Web Client
</code>
to
<code class="literal">
Replica 1
</code>
are written to the binary log of
<code class="literal">
Replica 1
</code>
,
which then contains every update sent to
<code class="literal">
Replica
1
</code>
since
<code class="literal">
Source
</code>
became unavailable.
</p>
<p>
The resulting server structure is shown in
<a class="xref" href="replication-solutions-switch.html#figure_replication-redundancy-after" title="Figure 19.5 Redundancy Using Replication, After Source Failure">
Figure 19.5, “Redundancy Using Replication, After Source Failure”
</a>
.
</p>
<div class="figure">
<a name="figure_replication-redundancy-after">
</a>
<p class="title">
<b>
Figure 19.5 Redundancy Using Replication, After Source Failure
</b>
</p>
<div class="figure-contents">
<div class="mediaobject">
<img alt="The MySQL source server has failed, and is no longer connected into the replication topology. The two web clients now direct both database reads and database writes to Replica 1, which is the new source. Replica 1 replicates to Replica 2 and Replica 3." src="images/redundancy-after.png" style="width: 100%; max-width: 429px;"/>
</div>
</div>
</div>
<br class="figure-break"/>
<p>
When
<code class="literal">
Source
</code>
becomes available again, you should
make it a replica of
<code class="literal">
Replica 1
</code>
. To do this,
issue on
<code class="literal">
Source
</code>
the same
<a class="link" href="change-replication-source-to.html" title="15.4.2.2 CHANGE REPLICATION SOURCE TO Statement">
<code class="literal">
CHANGE REPLICATION SOURCE TO
</code>
</a>
statement as that issued on
<code class="literal">
Replica 2
</code>
and
<code class="literal">
Replica 3
</code>
previously.
<code class="literal">
Source
</code>
then becomes a replica of
<code class="literal">
Replica 1
</code>
and picks
up the
<code class="literal">
Web Client
</code>
writes that it missed while
it was offline.
</p>
<p>
To make
<code class="literal">
Source
</code>
a source again, use the
preceding procedure as if
<code class="literal">
Replica 1
</code>
were
unavailable and
<code class="literal">
Source
</code>
were to be the new
source. During this procedure, do not forget to run
<a class="link" href="reset-binary-logs-and-gtids.html" title="15.4.1.2 RESET BINARY LOGS AND GTIDS Statement">
<code class="literal">
RESET BINARY LOGS AND GTIDS
</code>
</a>
on
<code class="literal">
Source
</code>
before making
<code class="literal">
Replica
1
</code>
,
<code class="literal">
Replica 2
</code>
, and
<code class="literal">
Replica
3
</code>
replicas of
<code class="literal">
Source
</code>
. If you fail to
do this, the replicas may pick up stale writes from the
<code class="literal">
Web Client
</code>
applications dating from before the
point at which
<code class="literal">
Source
</code>
became unavailable.
</p>
<p>
You should be aware that there is no synchronization between
replicas, even when they share the same source, and thus some
replicas might be considerably ahead of others. This means that in
some cases the procedure outlined in the previous example might
not work as expected. In practice, however, relay logs on all
replicas should be relatively close together.
</p>
<p>
One way to keep applications informed about the location of the
source is to have a dynamic DNS entry for the source host. With
<code class="literal">
BIND
</code>
, you can use
<span class="command">
<strong>
nsupdate
</strong>
</span>
to update the DNS
dynamically.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/performance-schema-events-stages-history-long-table.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="performance-schema-events-stages-history-long-table">
</a>
29.12.5.3 The events_stages_history_long Table
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045072973616">
</a>
<a class="indexterm" name="idm46045072972112">
</a>
<p>
The
<a class="link" href="performance-schema-events-stages-history-long-table.html" title="29.12.5.3 The events_stages_history_long Table">
<code class="literal">
events_stages_history_long
</code>
</a>
table contains the
<em class="replaceable">
<code>
N
</code>
</em>
most recent
stage events that have ended globally, across all threads.
Stage events are not added to the table until they have ended.
When the table becomes full, the oldest row is discarded when
a new row is added, regardless of which thread generated
either row.
</p>
<p>
The Performance Schema autosizes the value of
<em class="replaceable">
<code>
N
</code>
</em>
during server startup. To set the
table size explicitly, set the
<a class="link" href="performance-schema-system-variables.html#sysvar_performance_schema_events_stages_history_long_size">
<code class="literal">
performance_schema_events_stages_history_long_size
</code>
</a>
system variable at server startup.
</p>
<p>
The
<a class="link" href="performance-schema-events-stages-history-long-table.html" title="29.12.5.3 The events_stages_history_long Table">
<code class="literal">
events_stages_history_long
</code>
</a>
table has the same columns as
<a class="link" href="performance-schema-events-stages-current-table.html" title="29.12.5.1 The events_stages_current Table">
<code class="literal">
events_stages_current
</code>
</a>
. See
<a class="xref" href="performance-schema-events-stages-current-table.html" title="29.12.5.1 The events_stages_current Table">
Section 29.12.5.1, “The events_stages_current Table”
</a>
.
Unlike
<a class="link" href="performance-schema-events-stages-current-table.html" title="29.12.5.1 The events_stages_current Table">
<code class="literal">
events_stages_current
</code>
</a>
,
<a class="link" href="performance-schema-events-stages-history-long-table.html" title="29.12.5.3 The events_stages_history_long Table">
<code class="literal">
events_stages_history_long
</code>
</a>
has no
indexing.
</p>
<p>
<a class="link" href="truncate-table.html" title="15.1.37 TRUNCATE TABLE Statement">
<code class="literal">
TRUNCATE TABLE
</code>
</a>
is permitted for
the
<a class="link" href="performance-schema-events-stages-history-long-table.html" title="29.12.5.3 The events_stages_history_long Table">
<code class="literal">
events_stages_history_long
</code>
</a>
table. It removes the rows.
</p>
<p>
For more information about the relationship between the three
stage event tables, see
<a class="xref" href="performance-schema-event-tables.html" title="29.9 Performance Schema Tables for Current and Historical Events">
Section 29.9, “Performance Schema Tables for Current and Historical Events”
</a>
.
</p>
<p>
For information about configuring whether to collect stage
events, see
<a class="xref" href="performance-schema-stage-tables.html" title="29.12.5 Performance Schema Stage Event Tables">
Section 29.12.5, “Performance Schema Stage Event Tables”
</a>
.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/group-replication-tuning-recovery.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="group-replication-tuning-recovery">
</a>
20.5.4.3 Configuring Distributed Recovery
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045132979536">
</a>
<p>
Several aspects of Group Replication's distributed recovery
process can be configured to suit your system.
</p>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h5 class="title">
<a name="idm46045132977504">
</a>
Number of Connection Attempts
</h5>
</div>
</div>
</div>
<p>
For state transfer from the binary log, Group Replication
limits the number of attempts a joining member makes when
trying to connect to a donor from the pool of donors. If the
connection retry limit is reached without a successful
connection, the distributed recovery procedure terminates with
an error. Note that this limit specifies the total number of
attempts that the joining member makes to connect to a donor.
For example, if 2 group members are suitable donors, and the
connection retry limit is set to 4, the joining member makes 2
attempts to connect to each of the donors before reaching the
limit.
</p>
<p>
The default connection retry limit is 10. You can configure
this setting using the
<a class="link" href="group-replication-system-variables.html#sysvar_group_replication_recovery_retry_count">
<code class="literal">
group_replication_recovery_retry_count
</code>
</a>
system variable. The following statement sets the maximum
number of attempts to connect to a donor to 5:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa98773774"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SET</span> <span class="token keyword">GLOBAL</span> group_replication_recovery_retry_count<span class="token operator">=</span> <span class="token number">5</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
For remote cloning operations, this limit does not apply.
Group Replication makes only one connection attempt to each
suitable donor for cloning, before starting to attempt state
transfer from the binary log.
</p>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h5 class="title">
<a name="idm46045132971312">
</a>
Sleep Interval for Connection Attempts
</h5>
</div>
</div>
</div>
<p>
For state transfer from the binary log, the
<a class="link" href="group-replication-system-variables.html#sysvar_group_replication_recovery_reconnect_interval">
<code class="literal">
group_replication_recovery_reconnect_interval
</code>
</a>
system variable defines how much time the distributed recovery
process should sleep between donor connection attempts. Note
that distributed recovery does not sleep after every donor
connection attempt. As the joining member is connecting to
different servers and not to the same one repeatedly, it can
assume that the problem that affects server A does not affect
server B. Distributed recovery therefore suspends only when it
has gone through all the possible donors. Once the server
joining the group has made one attempt to connect to each of
the suitable donors in the group, the distributed recovery
process sleeps for the number of seconds configured by the
<a class="link" href="group-replication-system-variables.html#sysvar_group_replication_recovery_reconnect_interval">
<code class="literal">
group_replication_recovery_reconnect_interval
</code>
</a>
system variable. For example, if 2 group members are suitable
donors, and the connection retry limit is set to 4, the
joining member makes one attempt to connect to each of the
donors, then sleeps for the connection retry interval, then
makes one further attempt to connect to each of the donors
before reaching the limit.
</p>
<p>
The default connection retry interval is 60 seconds, and you
can change this value dynamically. The following statement
sets the distributed recovery donor connection retry interval
to 120 seconds:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa52545286"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SET</span> <span class="token keyword">GLOBAL</span> group_replication_recovery_reconnect_interval<span class="token operator">=</span> <span class="token number">120</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
For remote cloning operations, this interval does not apply.
Group Replication makes only one connection attempt to each
suitable donor for cloning, before starting to attempt state
transfer from the binary log.
</p>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h5 class="title">
<a name="idm46045132962880">
</a>
Marking the Joining Member Online
</h5>
</div>
</div>
</div>
<p>
When distributed recovery has successfully completed state
transfer from the donor to the joining member, the joining
member can be marked as online in the group and ready to
participate. This is done after the new member has received
and applied all the transactions that it missed prior to
joining the group.
</p>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/replication-gtids-functions.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="replication-gtids-functions">
</a>
19.1.3.8 Stored Function Examples to Manipulate GTIDs
</h4>
</div>
</div>
</div>
<p>
This section provides examples of stored functions (see
<a class="xref" href="stored-objects.html" title="Chapter 27 Stored Objects">
Chapter 27,
<i>
Stored Objects
</i>
</a>
) which you can create using some
of the built-in functions provided by MySQL for use with
GTID-based replication, listed here:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<a class="link" href="gtid-functions.html#function_gtid-subset">
<code class="literal">
GTID_SUBSET()
</code>
</a>
: Shows whether
one GTID set is a subset of another.
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="gtid-functions.html#function_gtid-subtract">
<code class="literal">
GTID_SUBTRACT()
</code>
</a>
: Returns the
GTIDs from one GTID set that are not in another.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
WAIT_FOR_EXECUTED_GTID_SET()
</code>
: Waits until
all transactions in a given GTID set have been executed.
</p>
</li>
</ul>
</div>
<p>
See
<a class="xref" href="gtid-functions.html" title="14.18.2 Functions Used with Global Transaction Identifiers (GTIDs)">
Section 14.18.2, “Functions Used with Global Transaction Identifiers (GTIDs)”
</a>
, more more information about
the functions just listed.
</p>
<p>
Note that in these stored functions, the delimiter command has
been used to change the MySQL statement delimiter to a vertical
bar, like this:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa54666559"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">delimiter</span> <span class="token operator">|</span></code></pre>
</div>
<p>
All of the stored functions shown in this section take string
representations of GTID sets as arguments, so GTID sets must
always be quoted when used with them.
</p>
<p>
This function returns nonzero (true) if two GTID sets are the same
set, even if they are not formatted in the same way:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa80898794"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">FUNCTION</span> GTID_IS_EQUAL<span class="token punctuation">(</span>gs1 <span class="token datatype">LONGTEXT</span><span class="token punctuation">,</span> gs2 <span class="token datatype">LONGTEXT</span><span class="token punctuation">)</span>
<span class="token keyword">RETURNS</span> <span class="token datatype">INT</span>
<span class="token keyword">RETURN</span> <span class="token function">GTID_SUBSET</span><span class="token punctuation">(</span>gs1<span class="token punctuation">,</span> gs2<span class="token punctuation">)</span> <span class="token operator">AND</span> <span class="token function">GTID_SUBSET</span><span class="token punctuation">(</span>gs2<span class="token punctuation">,</span> gs1<span class="token punctuation">)</span>
<span class="token operator">|</span></code></pre>
</div>
<p>
This function returns nonzero (true) if two GTID sets are
disjoint:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa75093956"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">FUNCTION</span> GTID_IS_DISJOINT<span class="token punctuation">(</span>gs1 <span class="token datatype">LONGTEXT</span><span class="token punctuation">,</span> gs2 <span class="token datatype">LONGTEXT</span><span class="token punctuation">)</span>
<span class="token keyword">RETURNS</span> <span class="token datatype">INT</span>
<span class="token keyword">RETURN</span> <span class="token function">GTID_SUBSET</span><span class="token punctuation">(</span>gs1<span class="token punctuation">,</span> <span class="token function">GTID_SUBTRACT</span><span class="token punctuation">(</span>gs1<span class="token punctuation">,</span> gs2<span class="token punctuation">)</span><span class="token punctuation">)</span>
<span class="token operator">|</span></code></pre>
</div>
<p>
This function returns nonzero (true) if two GTID sets are disjoint
and
<code class="literal">
sum
</code>
is their union:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa7938482"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">FUNCTION</span> GTID_IS_DISJOINT_UNION<span class="token punctuation">(</span>gs1 <span class="token datatype">LONGTEXT</span><span class="token punctuation">,</span> gs2 <span class="token datatype">LONGTEXT</span><span class="token punctuation">,</span> sum <span class="token datatype">LONGTEXT</span><span class="token punctuation">)</span>
<span class="token keyword">RETURNS</span> <span class="token datatype">INT</span>
<span class="token keyword">RETURN</span> GTID_IS_EQUAL<span class="token punctuation">(</span><span class="token function">GTID_SUBTRACT</span><span class="token punctuation">(</span>sum<span class="token punctuation">,</span> gs1<span class="token punctuation">)</span><span class="token punctuation">,</span> gs2<span class="token punctuation">)</span> <span class="token operator">AND</span>
GTID_IS_EQUAL<span class="token punctuation">(</span><span class="token function">GTID_SUBTRACT</span><span class="token punctuation">(</span>sum<span class="token punctuation">,</span> gs2<span class="token punctuation">)</span><span class="token punctuation">,</span> gs1<span class="token punctuation">)</span>
<span class="token operator">|</span></code></pre>
</div>
<p>
This function returns a normalized form of the GTID set, in all
uppercase, with no whitespace and no duplicates, with UUIDs in
alphabetic order and intervals in numeric order:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa30288001"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">FUNCTION</span> GTID_NORMALIZE<span class="token punctuation">(</span>gs <span class="token datatype">LONGTEXT</span><span class="token punctuation">)</span>
<span class="token keyword">RETURNS</span> <span class="token datatype">LONGTEXT</span>
<span class="token keyword">RETURN</span> <span class="token function">GTID_SUBTRACT</span><span class="token punctuation">(</span>gs<span class="token punctuation">,</span> <span class="token string">''</span><span class="token punctuation">)</span>
<span class="token operator">|</span></code></pre>
</div>
<p>
</p>
<p>
This function returns the union of two GTID sets:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa58935235"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">FUNCTION</span> GTID_UNION<span class="token punctuation">(</span>gs1 <span class="token datatype">LONGTEXT</span><span class="token punctuation">,</span> gs2 <span class="token datatype">LONGTEXT</span><span class="token punctuation">)</span>
<span class="token keyword">RETURNS</span> <span class="token datatype">LONGTEXT</span>
<span class="token keyword">RETURN</span> GTID_NORMALIZE<span class="token punctuation">(</span><span class="token function">CONCAT</span><span class="token punctuation">(</span>gs1<span class="token punctuation">,</span> <span class="token string">','</span><span class="token punctuation">,</span> gs2<span class="token punctuation">)</span><span class="token punctuation">)</span>
<span class="token operator">|</span></code></pre>
</div>
<p>
This function returns the intersection of two GTID sets.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa69656008"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">FUNCTION</span> GTID_INTERSECTION<span class="token punctuation">(</span>gs1 <span class="token datatype">LONGTEXT</span><span class="token punctuation">,</span> gs2 <span class="token datatype">LONGTEXT</span><span class="token punctuation">)</span>
<span class="token keyword">RETURNS</span> <span class="token datatype">LONGTEXT</span>
<span class="token keyword">RETURN</span> <span class="token function">GTID_SUBTRACT</span><span class="token punctuation">(</span>gs1<span class="token punctuation">,</span> <span class="token function">GTID_SUBTRACT</span><span class="token punctuation">(</span>gs1<span class="token punctuation">,</span> gs2<span class="token punctuation">)</span><span class="token punctuation">)</span>
<span class="token operator">|</span></code></pre>
</div>
<p>
This function returns the symmetric difference between two GTID
sets, that is, the GTIDs that exist in
<code class="literal">
gs1
</code>
but
not in
<code class="literal">
gs2
</code>
, as well as the GTIDs that exist in
<code class="literal">
gs2
</code>
but not in
<code class="literal">
gs1
</code>
.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa63972432"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">FUNCTION</span> GTID_SYMMETRIC_DIFFERENCE<span class="token punctuation">(</span>gs1 <span class="token datatype">LONGTEXT</span><span class="token punctuation">,</span> gs2 <span class="token datatype">LONGTEXT</span><span class="token punctuation">)</span>
<span class="token keyword">RETURNS</span> <span class="token datatype">LONGTEXT</span>
<span class="token keyword">RETURN</span> <span class="token function">GTID_SUBTRACT</span><span class="token punctuation">(</span><span class="token function">CONCAT</span><span class="token punctuation">(</span>gs1<span class="token punctuation">,</span> <span class="token string">','</span><span class="token punctuation">,</span> gs2<span class="token punctuation">)</span><span class="token punctuation">,</span> GTID_INTERSECTION<span class="token punctuation">(</span>gs1<span class="token punctuation">,</span> gs2<span class="token punctuation">)</span><span class="token punctuation">)</span>
<span class="token operator">|</span></code></pre>
</div>
<p>
This function removes from a GTID set all the GTIDs with the
specified origin, and returns the remaining GTIDs, if any. The
UUID is the identifier used by the server where the transaction
originated, which is normally the value of
<a class="link" href="replication-options.html#sysvar_server_uuid">
<code class="literal">
server_uuid
</code>
</a>
.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa17337314"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">FUNCTION</span> GTID_SUBTRACT_UUID<span class="token punctuation">(</span>gs <span class="token datatype">LONGTEXT</span><span class="token punctuation">,</span> uuid <span class="token datatype">TEXT</span><span class="token punctuation">)</span>
<span class="token keyword">RETURNS</span> <span class="token datatype">LONGTEXT</span>
<span class="token keyword">RETURN</span> <span class="token function">GTID_SUBTRACT</span><span class="token punctuation">(</span>gs<span class="token punctuation">,</span> <span class="token function">CONCAT</span><span class="token punctuation">(</span>UUID<span class="token punctuation">,</span> <span class="token string">':1-'</span><span class="token punctuation">,</span> <span class="token punctuation">(</span><span class="token number">1</span> <span class="token operator"><<</span> <span class="token number">63</span><span class="token punctuation">)</span> <span class="token operator">-</span> <span class="token number">2</span><span class="token punctuation">)</span><span class="token punctuation">)</span>
<span class="token operator">|</span></code></pre>
</div>
<p>
This function acts as the reverse of the previous one; it returns
only those GTIDs from the GTID set that originate from the server
with the specified identifier (UUID).
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa17924126"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">FUNCTION</span> GTID_INTERSECTION_WITH_UUID<span class="token punctuation">(</span>gs <span class="token datatype">LONGTEXT</span><span class="token punctuation">,</span> uuid <span class="token datatype">TEXT</span><span class="token punctuation">)</span>
<span class="token keyword">RETURNS</span> <span class="token datatype">LONGTEXT</span>
<span class="token keyword">RETURN</span> <span class="token function">GTID_SUBTRACT</span><span class="token punctuation">(</span>gs<span class="token punctuation">,</span> GTID_SUBTRACT_UUID<span class="token punctuation">(</span>gs<span class="token punctuation">,</span> uuid<span class="token punctuation">)</span><span class="token punctuation">)</span>
<span class="token operator">|</span></code></pre>
</div>
<div class="example">
<a name="idm46045145737376">
</a>
<p class="title">
<b>
Example 19.1 Verifying that a replica is up to date
</b>
</p>
<div class="example-contents">
<p>
The built-in functions
<a class="link" href="gtid-functions.html#function_gtid-subset">
<code class="literal">
GTID_SUBSET()
</code>
</a>
and
<a class="link" href="gtid-functions.html#function_gtid-subtract">
<code class="literal">
GTID_SUBTRACT()
</code>
</a>
can be used to
check that a replica has applied at least every transaction that
a source has applied.
</p>
<p>
To perform this check with
<code class="literal">
GTID_SUBSET()
</code>
,
execute the following statement on the replica:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa20546380"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SELECT</span> <span class="token function">GTID_SUBSET</span><span class="token punctuation">(</span><em class="replaceable">source_gtid_executed</em><span class="token punctuation">,</span> <em class="replaceable">replica_gtid_executed</em><span class="token punctuation">)</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
If the returns value is
<code class="literal">
0
</code>
(false), this means
that some GTIDs in
<em class="replaceable">
<code>
source_gtid_executed
</code>
</em>
are not present
in
<em class="replaceable">
<code>
replica_gtid_executed
</code>
</em>
, and that
the replica has not yet applied transactions that were applied
on the source, which means that the replica is not up to date.
</p>
<p>
To perform the same check with
<code class="literal">
GTID_SUBTRACT()
</code>
, execute the following
statement on the replica:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa25009136"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SELECT</span> <span class="token function">GTID_SUBTRACT</span><span class="token punctuation">(</span><em class="replaceable">source_gtid_executed</em><span class="token punctuation">,</span> <em class="replaceable">replica_gtid_executed</em><span class="token punctuation">)</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
This statement returns any GTIDs that are in
<em class="replaceable">
<code>
source_gtid_executed
</code>
</em>
but not in
<em class="replaceable">
<code>
replica_gtid_executed
</code>
</em>
. If any GTIDs
are returned, the source has applied some transactions that the
replica has not applied, and the replica is therefore not up to
date.
</p>
</div>
</div>
<br class="example-break"/>
<div class="example">
<a name="idm46045145723856">
</a>
<p class="title">
<b>
Example 19.2 Backup and restore scenario
</b>
</p>
<div class="example-contents">
<p>
The stored functions
<code class="literal">
GTID_IS_EQUAL()
</code>
,
<code class="literal">
GTID_IS_DISJOINT()
</code>
, and
<code class="literal">
GTID_IS_DISJOINT_UNION()
</code>
can be used to
verify backup and restore operations involving multiple
databases and servers. In this example scenario,
<code class="literal">
server1
</code>
contains database
<code class="literal">
db1
</code>
, and
<code class="literal">
server2
</code>
contains
database
<code class="literal">
db2
</code>
. The goal is to copy database
<code class="literal">
db2
</code>
to
<code class="literal">
server1
</code>
, and the
result on
<code class="literal">
server1
</code>
should be the union of the
two databases. The procedure used is to back up
<code class="literal">
server2
</code>
using
<a class="link" href="mysqldump.html" title="6.5.4 mysqldump — A Database Backup Program">
<span class="command">
<strong>
mysqldump
</strong>
</span>
</a>
,
then to restore this backup on
<code class="literal">
server1
</code>
.
</p>
<p>
Provided that
<a class="link" href="mysqldump.html" title="6.5.4 mysqldump — A Database Backup Program">
<span class="command">
<strong>
mysqldump
</strong>
</span>
</a>
was run with
<a class="link" href="mysqldump.html#option_mysqldump_set-gtid-purged">
<code class="option">
--set-gtid-purged
</code>
</a>
set to
<code class="literal">
ON
</code>
or
<code class="literal">
AUTO
</code>
(the default),
the output contains a
<code class="literal">
SET
@@GLOBAL.gtid_purged
</code>
statement which adds the
<a class="link" href="replication-options-gtids.html#sysvar_gtid_executed">
<code class="literal">
gtid_executed
</code>
</a>
set from
<code class="literal">
server2
</code>
to the
<a class="link" href="replication-options-gtids.html#sysvar_gtid_purged">
<code class="literal">
gtid_purged
</code>
</a>
set on
<code class="literal">
server1
</code>
.
<code class="literal">
gtid_purged
</code>
contains the GTIDs of all the transactions that have been
committed on a given server but which do not exist in any binary
log file on the server. When database
<code class="literal">
db2
</code>
is
copied to
<code class="literal">
server1
</code>
, the GTIDs of the
transactions committed on
<code class="literal">
server2
</code>
, which are
not in the binary log files on
<code class="literal">
server1
</code>
, must
be added to
<code class="literal">
gtid_purged
</code>
for
<code class="literal">
server1
</code>
to make the set complete.
</p>
<p>
The stored functions can be used to assist with the following
steps in this scenario:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
Use
<code class="literal">
GTID_IS_EQUAL()
</code>
to verify that the
backup operation computed the correct GTID set for the
<code class="literal">
SET @@GLOBAL.gtid_purged
</code>
statement. On
<code class="literal">
server2
</code>
, extract that statement from the
<a class="link" href="mysqldump.html" title="6.5.4 mysqldump — A Database Backup Program">
<span class="command">
<strong>
mysqldump
</strong>
</span>
</a>
output, and store the GTID set
into a local variable, such as
<code class="literal">
$gtid_purged_set
</code>
. Then execute the
following statement:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa45451356"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql">server2<span class="token operator">></span> <span class="token keyword">SELECT</span> GTID_IS_EQUAL<span class="token punctuation">(</span>$gtid_purged_set<span class="token punctuation">,</span> <span class="token variable">@@GLOBAL.gtid_executed</span><span class="token punctuation">)</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
If the result is 1, the two GTID sets are equal, and the set
has been computed correctly.
</p>
</li>
<li class="listitem">
<p>
Use
<code class="literal">
GTID_IS_DISJOINT()
</code>
to verify that the
GTID set in the
<a class="link" href="mysqldump.html" title="6.5.4 mysqldump — A Database Backup Program">
<span class="command">
<strong>
mysqldump
</strong>
</span>
</a>
output does not
overlap with the
<code class="literal">
gtid_executed
</code>
set on
<code class="literal">
server1
</code>
. Having identical GTIDs present
on both servers causes errors when copying database
<code class="literal">
db2
</code>
to
<code class="literal">
server1
</code>
. To
check, on
<code class="literal">
server1
</code>
, extract and store
<code class="literal">
gtid_purged
</code>
from the output into a local
variable as done previously, then execute the following
statement:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa51492795"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql">server1<span class="token operator">></span> <span class="token keyword">SELECT</span> GTID_IS_DISJOINT<span class="token punctuation">(</span>$gtid_purged_set<span class="token punctuation">,</span> <span class="token variable">@@GLOBAL.gtid_executed</span><span class="token punctuation">)</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
If the result is 1, there is no overlap between the two GTID
sets, so no duplicate GTIDs are present.
</p>
</li>
<li class="listitem">
<p>
Use
<code class="literal">
GTID_IS_DISJOINT_UNION()
</code>
to verify
that the restore operation resulted in the correct GTID
state on
<code class="literal">
server1
</code>
. Before restoring the
backup, on
<code class="literal">
server1
</code>
, obtain the existing
<code class="literal">
gtid_executed
</code>
set by executing the
following statement:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa30645690"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql">server1<span class="token operator">></span> <span class="token keyword">SELECT</span> <span class="token variable">@@GLOBAL.gtid_executed</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
Store the result in a local variable
<code class="literal">
$original_gtid_executed
</code>
, as well as the
set from
<code class="literal">
gtid_purged
</code>
in another local
variable as described previously. When the backup from
<code class="literal">
server2
</code>
has been restored onto
<code class="literal">
server1
</code>
, execute the following statement
to verify the GTID state:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa5067275"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql">server1<span class="token operator">></span> <span class="token keyword">SELECT</span>
<span class="token prompt"> -></span> GTID_IS_DISJOINT_UNION<span class="token punctuation">(</span>$original_gtid_executed<span class="token punctuation">,</span>
<span class="token prompt"> -></span> $gtid_purged_set<span class="token punctuation">,</span>
<span class="token prompt"> -></span> <span class="token variable">@@GLOBAL.gtid_executed</span><span class="token punctuation">)</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
If the result is
<code class="literal">
1
</code>
, the stored function
has verified that the original
<code class="literal">
gtid_executed
</code>
set from
<code class="literal">
server1
</code>
(
<code class="literal">
$original_gtid_executed
</code>
) and the
<code class="literal">
gtid_purged
</code>
set that was added from
<code class="literal">
server2
</code>
(
<code class="literal">
$gtid_purged_set
</code>
) have no overlap, and
that the updated
<code class="literal">
gtid_executed
</code>
set on
<code class="literal">
server1
</code>
now consists of the previous
<code class="literal">
gtid_executed
</code>
set from
<code class="literal">
server1
</code>
plus the
<code class="literal">
gtid_purged
</code>
set from
<code class="literal">
server2
</code>
, which is the desired result.
Ensure that this check is carried out before any further
transactions take place on
<code class="literal">
server1
</code>
,
otherwise the new transactions in
<code class="literal">
gtid_executed
</code>
cause it to fail.
</p>
</li>
</ul>
</div>
</div>
</div>
<br class="example-break"/>
<div class="example">
<a name="idm46045145656048">
</a>
<p class="title">
<b>
Example 19.3 Selecting the most up-to-date replica for manual failover
</b>
</p>
<div class="example-contents">
<p>
The stored function
<code class="literal">
GTID_UNION()
</code>
can be used
to identify the most up-to-date replica from a set of replicas,
in order to perform a manual failover operation after a source
server has stopped unexpectedly. If some of the replicas are
experiencing replication lag, this stored function can be used
to compute the most up-to-date replica without waiting for all
the replicas to apply their existing relay logs, and therefore
to minimize the failover time. The function can return the union
of
<a class="link" href="replication-options-gtids.html#sysvar_gtid_executed">
<code class="literal">
gtid_executed
</code>
</a>
on each
replica with the set of transactions received by the replica,
which is recorded in the Performance Schema
<a class="link" href="performance-schema-replication-connection-status-table.html" title="29.12.11.13 The replication_connection_status Table">
<code class="literal">
replication_connection_status
</code>
</a>
table. You can compare these results to find which
replica's record of transactions is the most up to date,
even if not all of the transactions have been committed yet.
</p>
<p>
On each replica, compute the complete record of transactions by
issuing the following statement:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa5863146"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SELECT</span> GTID_UNION<span class="token punctuation">(</span>RECEIVED_TRANSACTION_SET<span class="token punctuation">,</span> <span class="token variable">@@GLOBAL.gtid_executed</span><span class="token punctuation">)</span>
<span class="token keyword">FROM</span> performance_schema<span class="token punctuation">.</span>replication_connection_status
<span class="token keyword">WHERE</span> channel_name <span class="token operator">=</span> <span class="token string">'name'</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
You can then compare the results from each replica to see which
one has the most up-to-date record of transactions, and use this
replica as the new source.
</p>
</div>
</div>
<br class="example-break"/>
<div class="example">
<a name="idm46045145648256">
</a>
<p class="title">
<b>
Example 19.4 Checking for extraneous transactions on a replica
</b>
</p>
<div class="example-contents">
<p>
The stored function
<code class="literal">
GTID_SUBTRACT_UUID()
</code>
can
be used to check whether a replica has received transactions
that did not originate from its designated source or sources. If
it has, there might be an issue with your replication setup, or
with a proxy, router, or load balancer. This function works by
removing from a GTID set all the GTIDs from a specified
originating server, and returning the remaining GTIDs, if any.
</p>
<p>
For a replica with a single source, issue the following
statement, giving the identifier of the originating source,
which is normally the same as
<a class="link" href="replication-options.html#sysvar_server_uuid">
<code class="literal">
server_uuid
</code>
</a>
:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa14286437"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SELECT</span> GTID_SUBTRACT_UUID<span class="token punctuation">(</span><span class="token variable">@@GLOBAL.gtid_executed</span><span class="token punctuation">,</span> server_uuid_of_source<span class="token punctuation">)</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
If the result is not empty, the transactions returned are extra
transactions that did not originate from the designated source.
</p>
<p>
For a replica in a multisource topology, include the server UUID
of each source in the function call, like this:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa81837690"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SELECT</span>
GTID_SUBTRACT_UUID<span class="token punctuation">(</span>GTID_SUBTRACT_UUID<span class="token punctuation">(</span><span class="token variable">@@GLOBAL.gtid_executed</span><span class="token punctuation">,</span>
server_uuid_of_source_1<span class="token punctuation">)</span><span class="token punctuation">,</span>
server_uuid_of_source_2<span class="token punctuation">)</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
If the result is not empty, the transactions returned are extra
transactions that did not originate from any of the designated
sources.
</p>
</div>
</div>
<br class="example-break"/>
<div class="example">
<a name="idm46045145640064">
</a>
<p class="title">
<b>
Example 19.5 Verifying that a server in a replication topology is read-only
</b>
</p>
<div class="example-contents">
<p>
The stored function
<code class="literal">
GTID_INTERSECTION_WITH_UUID()
</code>
can be used to
verify that a server has not originated any GTIDs and is in a
read-only state. The function returns only those GTIDs from the
GTID set that originate from the server with the specified
identifier. If any of the transactions listed in
<a class="link" href="replication-options-gtids.html#sysvar_gtid_executed">
<code class="literal">
gtid_executed
</code>
</a>
from this server
use the server's own identifier, the server itself
originated those transactions. You can issue the following
statement on the server to check:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa90193428"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SELECT</span> GTID_INTERSECTION_WITH_UUID<span class="token punctuation">(</span><span class="token variable">@@GLOBAL.gtid_executed</span><span class="token punctuation">,</span> my_server_uuid<span class="token punctuation">)</span><span class="token punctuation">;</span></code></pre>
</div>
</div>
</div>
<br class="example-break"/>
<div class="example">
<a name="idm46045145635376">
</a>
<p class="title">
<b>
Example 19.6 Validating an additional replica in multisource replication
</b>
</p>
<div class="example-contents">
<p>
The stored function
<code class="literal">
GTID_INTERSECTION_WITH_UUID()
</code>
can be used to
find out if a replica attached to a multisource replication
setup has applied all the transactions originating from one
particular source. In this scenario,
<code class="literal">
source1
</code>
and
<code class="literal">
source2
</code>
are both sources and replicas and
replicate to each other.
<code class="literal">
source2
</code>
also has its
own replica. The replica also receives and applies transactions
from
<code class="literal">
source1
</code>
if
<code class="literal">
source2
</code>
is
configured with
<a class="link" href="replication-options-binary-log.html#sysvar_log_replica_updates">
<code class="literal">
log_replica_updates=ON
</code>
</a>
, but it
does not do so if
<code class="literal">
source2
</code>
uses
<code class="literal">
log_replica_updates=OFF
</code>
. Whichever the case,
we currently want only to find out if the replica is up to date
with
<code class="literal">
source2
</code>
. In this situation,
<code class="literal">
GTID_INTERSECTION_WITH_UUID()
</code>
can be used to
identify the transactions that
<code class="literal">
source2
</code>
originated, discarding the transactions that
<code class="literal">
source2
</code>
has replicated from
<code class="literal">
source1
</code>
. The built-in function
<a class="link" href="gtid-functions.html#function_gtid-subset">
<code class="literal">
GTID_SUBSET()
</code>
</a>
can then be used to
compare the result with the
<a class="link" href="replication-options-gtids.html#sysvar_gtid_executed">
<code class="literal">
gtid_executed
</code>
</a>
set on the
replica. If the replica is up to date with
<code class="literal">
source2
</code>
, the
<code class="literal">
gtid_executed
</code>
set on the replica contains all the transactions in the
intersection set (the transactions that originated from
<code class="literal">
source2
</code>
).
</p>
<p>
To carry out this check, store the values of
<code class="literal">
gtid_executed
</code>
and the server UUID from
<code class="literal">
source2
</code>
and the value of
<a class="link" href="replication-options-gtids.html#sysvar_gtid_executed">
<code class="literal">
gtid_executed
</code>
</a>
from the replica
into user variables as follows:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa9376049"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql">source2<span class="token operator">></span> <span class="token keyword">SELECT</span> <span class="token variable">@@GLOBAL.gtid_executed</span> <span class="token keyword">INTO</span> <span class="token variable">@source2_gtid_executed</span><span class="token punctuation">;</span>
source2<span class="token operator">></span> <span class="token keyword">SELECT</span> <span class="token variable">@@GLOBAL.server_uuid</span> <span class="token keyword">INTO</span> <span class="token variable">@source2_server_uuid</span><span class="token punctuation">;</span>
<span class="token prompt">replica></span> <span class="token keyword">SELECT</span> <span class="token variable">@@GLOBAL.gtid_executed</span> <span class="token keyword">INTO</span> <span class="token variable">@replica_gtid_executed</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
Then use
<code class="literal">
GTID_INTERSECTION_WITH_UUID()
</code>
and
<code class="literal">
GTID_SUBSET()
</code>
with these variables as input,
as follows:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa41565623"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SELECT</span>
<span class="token function">GTID_SUBSET</span><span class="token punctuation">(</span>
GTID_INTERSECTION_WITH_UUID<span class="token punctuation">(</span><span class="token variable">@source2_gtid_executed</span><span class="token punctuation">,</span>
<span class="token variable">@source2_server_uuid</span><span class="token punctuation">)</span><span class="token punctuation">,</span>
<span class="token variable">@replica_gtid_executed</span><span class="token punctuation">)</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
The server identifier from
<code class="literal">
source2
</code>
(
<code class="literal">
@source2_server_uuid
</code>
) is used with
<code class="literal">
GTID_INTERSECTION_WITH_UUID()
</code>
to identify and
return only those GTIDs from the set of GTIDs that originated on
<code class="literal">
source2
</code>
, omitting those that originated on
<code class="literal">
source1
</code>
. The resulting GTID set is then
compared with the set of all executed GTIDs on the replica,
using
<code class="literal">
GTID_SUBSET()
</code>
. If this statement
returns nonzero (true), all the identified GTIDs from
<code class="literal">
source2
</code>
(the first set input) are also found
in
<a class="link" href="replication-options-gtids.html#sysvar_gtid_executed">
<code class="literal">
gtid_executed
</code>
</a>
from the
replica, meaning that the replica has received and executed all
the transactions that originated from
<code class="literal">
source2
</code>
.
</p>
</div>
</div>
<br class="example-break"/>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/estimating-performance.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="estimating-performance">
</a>
10.8.5 Estimating Query Performance
</h3>
</div>
</div>
</div>
<a class="indexterm" name="idm46045224564912">
</a>
<a class="indexterm" name="idm46045224563456">
</a>
<a class="indexterm" name="idm46045224561968">
</a>
<p>
In most cases, you can estimate query performance by counting
disk seeks. For small tables, you can usually find a row in one
disk seek (because the index is probably cached). For bigger
tables, you can estimate that, using B-tree indexes, you need
this many seeks to find a row:
<code class="literal">
log(
<em class="replaceable">
<code>
row_count
</code>
</em>
) /
log(
<em class="replaceable">
<code>
index_block_length
</code>
</em>
/ 3 * 2 /
(
<em class="replaceable">
<code>
index_length
</code>
</em>
+
<em class="replaceable">
<code>
data_pointer_length
</code>
</em>
)) + 1
</code>
.
</p>
<p>
In MySQL, an index block is usually 1,024 bytes and the data
pointer is usually four bytes. For a 500,000-row table with a
key value length of three bytes (the size of
<a class="link" href="integer-types.html" title="13.1.2 Integer Types (Exact Value) - INTEGER, INT, SMALLINT, TINYINT, MEDIUMINT, BIGINT">
<code class="literal">
MEDIUMINT
</code>
</a>
), the formula indicates
<code class="literal">
log(500,000)/log(1024/3*2/(3+4)) + 1
</code>
=
<code class="literal">
4
</code>
seeks.
</p>
<p>
This index would require storage of about 500,000 * 7 * 3/2 =
5.2MB (assuming a typical index buffer fill ratio of 2/3), so
you probably have much of the index in memory and so need only
one or two calls to read data to find the row.
</p>
<p>
For writes, however, you need four seek requests to find where
to place a new index value and normally two seeks to update the
index and write the row.
</p>
<p>
The preceding discussion does not mean that your application
performance slowly degenerates by log
<em class="replaceable">
<code>
N
</code>
</em>
. As long as everything is cached by
the OS or the MySQL server, things become only marginally slower
as the table gets bigger. After the data gets too big to be
cached, things start to go much slower until your applications
are bound only by disk seeks (which increase by log
<em class="replaceable">
<code>
N
</code>
</em>
). To avoid this, increase the key
cache size as the data grows. For
<code class="literal">
MyISAM
</code>
tables, the key cache size is controlled by the
<a class="link" href="server-system-variables.html#sysvar_key_buffer_size">
<code class="literal">
key_buffer_size
</code>
</a>
system
variable. See
<a class="xref" href="server-configuration.html" title="7.1.1 Configuring the Server">
Section 7.1.1, “Configuring the Server”
</a>
.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/internal-functions.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h2 class="title">
<a name="internal-functions">
</a>
14.22 Internal Functions
</h2>
</div>
</div>
</div>
<a class="indexterm" name="idm46045191489392">
</a>
<a class="indexterm" name="idm46045191488320">
</a>
<div class="table">
<a name="idm46045191486832">
</a>
<p class="title">
<b>
Table 14.32 Internal Functions
</b>
</p>
<div class="table-contents">
<table frame="box" rules="all" summary="A reference that lists functions intended only for internal use by the server.">
<colgroup>
<col style="width: 28%"/>
<col style="width: 71%"/>
</colgroup>
<thead>
<tr>
<th>
Name
</th>
<th>
Description
</th>
</tr>
</thead>
<tbody>
<tr>
<td>
<a class="link" href="internal-functions.html#function_can-access-column">
<code class="literal">
CAN_ACCESS_COLUMN()
</code>
</a>
</td>
<td>
Internal use only
</td>
</tr>
<tr>
<td>
<a class="link" href="internal-functions.html#function_can-access-database">
<code class="literal">
CAN_ACCESS_DATABASE()
</code>
</a>
</td>
<td>
Internal use only
</td>
</tr>
<tr>
<td>
<a class="link" href="internal-functions.html#function_can-access-table">
<code class="literal">
CAN_ACCESS_TABLE()
</code>
</a>
</td>
<td>
Internal use only
</td>
</tr>
<tr>
<td>
<a class="link" href="internal-functions.html#function_can-access-user">
<code class="literal">
CAN_ACCESS_USER()
</code>
</a>
</td>
<td>
Internal use only
</td>
</tr>
<tr>
<td>
<a class="link" href="internal-functions.html#function_can-access-view">
<code class="literal">
CAN_ACCESS_VIEW()
</code>
</a>
</td>
<td>
Internal use only
</td>
</tr>
<tr>
<td>
<a class="link" href="internal-functions.html#function_get-dd-column-privileges">
<code class="literal">
GET_DD_COLUMN_PRIVILEGES()
</code>
</a>
</td>
<td>
Internal use only
</td>
</tr>
<tr>
<td>
<a class="link" href="internal-functions.html#function_get-dd-create-options">
<code class="literal">
GET_DD_CREATE_OPTIONS()
</code>
</a>
</td>
<td>
Internal use only
</td>
</tr>
<tr>
<td>
<a class="link" href="internal-functions.html#function_get-dd-index-sub-part-length">
<code class="literal">
GET_DD_INDEX_SUB_PART_LENGTH()
</code>
</a>
</td>
<td>
Internal use only
</td>
</tr>
<tr>
<td>
<a class="link" href="internal-functions.html#function_internal-auto-increment">
<code class="literal">
INTERNAL_AUTO_INCREMENT()
</code>
</a>
</td>
<td>
Internal use only
</td>
</tr>
<tr>
<td>
<a class="link" href="internal-functions.html#function_internal-avg-row-length">
<code class="literal">
INTERNAL_AVG_ROW_LENGTH()
</code>
</a>
</td>
<td>
Internal use only
</td>
</tr>
<tr>
<td>
<a class="link" href="internal-functions.html#function_internal-check-time">
<code class="literal">
INTERNAL_CHECK_TIME()
</code>
</a>
</td>
<td>
Internal use only
</td>
</tr>
<tr>
<td>
<a class="link" href="internal-functions.html#function_internal-checksum">
<code class="literal">
INTERNAL_CHECKSUM()
</code>
</a>
</td>
<td>
Internal use only
</td>
</tr>
<tr>
<td>
<a class="link" href="internal-functions.html#function_internal-data-free">
<code class="literal">
INTERNAL_DATA_FREE()
</code>
</a>
</td>
<td>
Internal use only
</td>
</tr>
<tr>
<td>
<a class="link" href="internal-functions.html#function_internal-data-length">
<code class="literal">
INTERNAL_DATA_LENGTH()
</code>
</a>
</td>
<td>
Internal use only
</td>
</tr>
<tr>
<td>
<a class="link" href="internal-functions.html#function_internal-dd-char-length">
<code class="literal">
INTERNAL_DD_CHAR_LENGTH()
</code>
</a>
</td>
<td>
Internal use only
</td>
</tr>
<tr>
<td>
<a class="link" href="internal-functions.html#function_internal-get-comment-or-error">
<code class="literal">
INTERNAL_GET_COMMENT_OR_ERROR()
</code>
</a>
</td>
<td>
Internal use only
</td>
</tr>
<tr>
<td>
<a class="link" href="internal-functions.html#function_internal-get-enabled-role-json">
<code class="literal">
INTERNAL_GET_ENABLED_ROLE_JSON()
</code>
</a>
</td>
<td>
Internal use only
</td>
</tr>
<tr>
<td>
<a class="link" href="internal-functions.html#function_internal-get-hostname">
<code class="literal">
INTERNAL_GET_HOSTNAME()
</code>
</a>
</td>
<td>
Internal use only
</td>
</tr>
<tr>
<td>
<a class="link" href="internal-functions.html#function_internal-get-username">
<code class="literal">
INTERNAL_GET_USERNAME()
</code>
</a>
</td>
<td>
Internal use only
</td>
</tr>
<tr>
<td>
<a class="link" href="internal-functions.html#function_internal-get-view-warning-or-error">
<code class="literal">
INTERNAL_GET_VIEW_WARNING_OR_ERROR()
</code>
</a>
</td>
<td>
Internal use only
</td>
</tr>
<tr>
<td>
<a class="link" href="internal-functions.html#function_internal-index-column-cardinality">
<code class="literal">
INTERNAL_INDEX_COLUMN_CARDINALITY()
</code>
</a>
</td>
<td>
Internal use only
</td>
</tr>
<tr>
<td>
<a class="link" href="internal-functions.html#function_internal-index-length">
<code class="literal">
INTERNAL_INDEX_LENGTH()
</code>
</a>
</td>
<td>
Internal use only
</td>
</tr>
<tr>
<td>
<a class="link" href="internal-functions.html#function_internal-is-enabled-role">
<code class="literal">
INTERNAL_IS_ENABLED_ROLE()
</code>
</a>
</td>
<td>
Internal use only
</td>
</tr>
<tr>
<td>
<a class="link" href="internal-functions.html#function_internal-is-mandatory-role">
<code class="literal">
INTERNAL_IS_MANDATORY_ROLE()
</code>
</a>
</td>
<td>
Internal use only
</td>
</tr>
<tr>
<td>
<a class="link" href="internal-functions.html#function_internal-keys-disabled">
<code class="literal">
INTERNAL_KEYS_DISABLED()
</code>
</a>
</td>
<td>
Internal use only
</td>
</tr>
<tr>
<td>
<a class="link" href="internal-functions.html#function_internal-max-data-length">
<code class="literal">
INTERNAL_MAX_DATA_LENGTH()
</code>
</a>
</td>
<td>
Internal use only
</td>
</tr>
<tr>
<td>
<a class="link" href="internal-functions.html#function_internal-table-rows">
<code class="literal">
INTERNAL_TABLE_ROWS()
</code>
</a>
</td>
<td>
Internal use only
</td>
</tr>
<tr>
<td>
<a class="link" href="internal-functions.html#function_internal-update-time">
<code class="literal">
INTERNAL_UPDATE_TIME()
</code>
</a>
</td>
<td>
Internal use only
</td>
</tr>
</tbody>
</table>
</div>
<div class="table-contents">
<table cellpadding="0" cellspacing="0" style="position: fixed; top: 0px; display: none; left: 401px; width: 739px;">
<thead>
<tr>
<th style="width: 299.516px;">
Name
</th>
<th style="width: 438.484px;">
Description
</th>
</tr>
</thead>
</table>
</div>
</div>
<br class="table-break"/>
<p>
The functions listed in this section are intended only for
internal use by the server. Attempts by users to invoke them
result in an error.
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<a name="function_can-access-column">
</a>
<p>
<a class="link" href="internal-functions.html#function_can-access-column">
<code class="literal">
CAN_ACCESS_COLUMN(
<em class="replaceable">
<code>
ARGS
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045191389968">
</a>
</li>
<li class="listitem">
<a name="function_can-access-database">
</a>
<p>
<a class="link" href="internal-functions.html#function_can-access-database">
<code class="literal">
CAN_ACCESS_DATABASE(
<em class="replaceable">
<code>
ARGS
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045191383456">
</a>
</li>
<li class="listitem">
<a name="function_can-access-table">
</a>
<p>
<a class="link" href="internal-functions.html#function_can-access-table">
<code class="literal">
CAN_ACCESS_TABLE(
<em class="replaceable">
<code>
ARGS
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045191377008">
</a>
</li>
<li class="listitem">
<a name="function_can-access-user">
</a>
<p>
<a class="link" href="internal-functions.html#function_can-access-user">
<code class="literal">
CAN_ACCESS_USER(
<em class="replaceable">
<code>
ARGS
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045191370496">
</a>
</li>
<li class="listitem">
<a name="function_can-access-view">
</a>
<p>
<a class="link" href="internal-functions.html#function_can-access-view">
<code class="literal">
CAN_ACCESS_VIEW(
<em class="replaceable">
<code>
ARGS
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045191363984">
</a>
</li>
<li class="listitem">
<a name="function_get-dd-column-privileges">
</a>
<p>
<a class="link" href="internal-functions.html#function_get-dd-column-privileges">
<code class="literal">
GET_DD_COLUMN_PRIVILEGES(
<em class="replaceable">
<code>
ARGS
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045191357472">
</a>
</li>
<li class="listitem">
<a name="function_get-dd-create-options">
</a>
<p>
<a class="link" href="internal-functions.html#function_get-dd-create-options">
<code class="literal">
GET_DD_CREATE_OPTIONS(
<em class="replaceable">
<code>
ARGS
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045191350880">
</a>
</li>
<li class="listitem">
<a name="function_get-dd-index-sub-part-length">
</a>
<p>
<a class="link" href="internal-functions.html#function_get-dd-index-sub-part-length">
<code class="literal">
GET_DD_INDEX_SUB_PART_LENGTH(
<em class="replaceable">
<code>
ARGS
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045191344368">
</a>
</li>
<li class="listitem">
<a name="function_internal-auto-increment">
</a>
<p>
<a class="link" href="internal-functions.html#function_internal-auto-increment">
<code class="literal">
INTERNAL_AUTO_INCREMENT(
<em class="replaceable">
<code>
ARGS
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045191337808">
</a>
</li>
<li class="listitem">
<a name="function_internal-avg-row-length">
</a>
<p>
<a class="link" href="internal-functions.html#function_internal-avg-row-length">
<code class="literal">
INTERNAL_AVG_ROW_LENGTH(
<em class="replaceable">
<code>
ARGS
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045191331248">
</a>
</li>
<li class="listitem">
<a name="function_internal-check-time">
</a>
<p>
<a class="link" href="internal-functions.html#function_internal-check-time">
<code class="literal">
INTERNAL_CHECK_TIME(
<em class="replaceable">
<code>
ARGS
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045191324672">
</a>
</li>
<li class="listitem">
<a name="function_internal-checksum">
</a>
<p>
<a class="link" href="internal-functions.html#function_internal-checksum">
<code class="literal">
INTERNAL_CHECKSUM(
<em class="replaceable">
<code>
ARGS
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045191318160">
</a>
</li>
<li class="listitem">
<a name="function_internal-data-free">
</a>
<p>
<a class="link" href="internal-functions.html#function_internal-data-free">
<code class="literal">
INTERNAL_DATA_FREE(
<em class="replaceable">
<code>
ARGS
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045191311648">
</a>
</li>
<li class="listitem">
<a name="function_internal-data-length">
</a>
<p>
<a class="link" href="internal-functions.html#function_internal-data-length">
<code class="literal">
INTERNAL_DATA_LENGTH(
<em class="replaceable">
<code>
ARGS
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045191305120">
</a>
</li>
<li class="listitem">
<a name="function_internal-dd-char-length">
</a>
<p>
<a class="link" href="internal-functions.html#function_internal-dd-char-length">
<code class="literal">
INTERNAL_DD_CHAR_LENGTH(
<em class="replaceable">
<code>
ARGS
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045191298688">
</a>
</li>
<li class="listitem">
<a name="function_internal-get-comment-or-error">
</a>
<p>
<a class="link" href="internal-functions.html#function_internal-get-comment-or-error">
<code class="literal">
INTERNAL_GET_COMMENT_OR_ERROR(
<em class="replaceable">
<code>
ARGS
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045191292112">
</a>
</li>
<li class="listitem">
<a name="function_internal-get-enabled-role-json">
</a>
<p>
<a class="link" href="internal-functions.html#function_internal-get-enabled-role-json">
<code class="literal">
INTERNAL_GET_ENABLED_ROLE_JSON(
<em class="replaceable">
<code>
ARGS
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045191285536">
</a>
</li>
<li class="listitem">
<a name="function_internal-get-hostname">
</a>
<p>
<a class="link" href="internal-functions.html#function_internal-get-hostname">
<code class="literal">
INTERNAL_GET_HOSTNAME(
<em class="replaceable">
<code>
ARGS
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045191278928">
</a>
</li>
<li class="listitem">
<a name="function_internal-get-username">
</a>
<p>
<a class="link" href="internal-functions.html#function_internal-get-username">
<code class="literal">
INTERNAL_GET_USERNAME(
<em class="replaceable">
<code>
ARGS
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045191272384">
</a>
</li>
<li class="listitem">
<a name="function_internal-get-view-warning-or-error">
</a>
<p>
<a class="link" href="internal-functions.html#function_internal-get-view-warning-or-error">
<code class="literal">
INTERNAL_GET_VIEW_WARNING_OR_ERROR(
<em class="replaceable">
<code>
ARGS
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045191265728">
</a>
</li>
<li class="listitem">
<a name="function_internal-index-column-cardinality">
</a>
<p>
<a class="link" href="internal-functions.html#function_internal-index-column-cardinality">
<code class="literal">
INTERNAL_INDEX_COLUMN_CARDINALITY(
<em class="replaceable">
<code>
ARGS
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045191259088">
</a>
</li>
<li class="listitem">
<a name="function_internal-index-length">
</a>
<p>
<a class="link" href="internal-functions.html#function_internal-index-length">
<code class="literal">
INTERNAL_INDEX_LENGTH(
<em class="replaceable">
<code>
ARGS
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045191252560">
</a>
</li>
<li class="listitem">
<a name="function_internal-is-enabled-role">
</a>
<p>
<a class="link" href="internal-functions.html#function_internal-is-enabled-role">
<code class="literal">
INTERNAL_IS_ENABLED_ROLE(
<em class="replaceable">
<code>
ARGS
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045191246048">
</a>
</li>
<li class="listitem">
<a name="function_internal-is-mandatory-role">
</a>
<p>
<a class="link" href="internal-functions.html#function_internal-is-mandatory-role">
<code class="literal">
INTERNAL_IS_MANDATORY_ROLE(
<em class="replaceable">
<code>
ARGS
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045191239472">
</a>
</li>
<li class="listitem">
<a name="function_internal-keys-disabled">
</a>
<p>
<a class="link" href="internal-functions.html#function_internal-keys-disabled">
<code class="literal">
INTERNAL_KEYS_DISABLED(
<em class="replaceable">
<code>
ARGS
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045191232880">
</a>
</li>
<li class="listitem">
<a name="function_internal-max-data-length">
</a>
<p>
<a class="link" href="internal-functions.html#function_internal-max-data-length">
<code class="literal">
INTERNAL_MAX_DATA_LENGTH(
<em class="replaceable">
<code>
ARGS
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045191226352">
</a>
</li>
<li class="listitem">
<a name="function_internal-table-rows">
</a>
<p>
<a class="link" href="internal-functions.html#function_internal-table-rows">
<code class="literal">
INTERNAL_TABLE_ROWS(
<em class="replaceable">
<code>
ARGS
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045191219776">
</a>
</li>
<li class="listitem">
<a name="function_internal-update-time">
</a>
<p>
<a class="link" href="internal-functions.html#function_internal-update-time">
<code class="literal">
INTERNAL_UPDATE_TIME(
<em class="replaceable">
<code>
ARGS
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045191213248">
</a>
</li>
<li class="listitem">
<a name="function_is-visible-dd-object">
</a>
<p>
<a class="link" href="internal-functions.html#function_is-visible-dd-object">
<code class="literal">
IS_VISIBLE_DD_OBJECT(
<em class="replaceable">
<code>
ARGS
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045191206544">
</a>
</li>
</ul>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/gis-class-surface.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="gis-class-surface">
</a>
13.4.2.6 Surface Class
</h4>
</div>
</div>
</div>
<p>
A
<code class="literal">
Surface
</code>
is a two-dimensional geometry. It
is a noninstantiable class. Its only instantiable subclass is
<code class="literal">
Polygon
</code>
.
</p>
<p>
<span class="bold">
<strong>
<code class="literal">
Surface
</code>
Properties
</strong>
</span>
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
A
<code class="literal">
Surface
</code>
is defined as a
two-dimensional geometry.
</p>
</li>
<li class="listitem">
<p>
The OpenGIS specification defines a simple
<code class="literal">
Surface
</code>
as a geometry that consists of
a single
<span class="quote">
“
<span class="quote">
patch
</span>
”
</span>
that is associated with a
single exterior boundary and zero or more interior
boundaries.
</p>
</li>
<li class="listitem">
<p>
The boundary of a simple
<code class="literal">
Surface
</code>
is the
set of closed curves corresponding to its exterior and
interior boundaries.
</p>
</li>
</ul>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/set-variable.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="set-variable">
</a>
15.7.6.1 SET Syntax for Variable Assignment
</h4>
</div>
</div>
</div>
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<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa78442177"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SET</span> <em class="replaceable">variable</em> <span class="token operator">=</span> <em class="replaceable">expr</em> <span class="token punctuation">[</span><span class="token punctuation">,</span> <em class="replaceable">variable</em> <span class="token operator">=</span> <em class="replaceable">expr</em><span class="token punctuation">]</span> <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span>
<em class="replaceable">variable</em>: {
<em class="replaceable">user_var_name</em>
<span class="token operator">|</span> <em class="replaceable">param_name</em>
<span class="token operator">|</span> <em class="replaceable">local_var_name</em>
<span class="token operator">|</span> {<span class="token keyword">GLOBAL</span> <span class="token operator">|</span> <span class="token variable">@@GLOBAL.</span>} <em class="replaceable">system_var_name</em>
<span class="token operator">|</span> {<span class="token keyword">PERSIST</span> <span class="token operator">|</span> <span class="token variable">@@PERSIST.</span>} <em class="replaceable">system_var_name</em>
<span class="token operator">|</span> {<span class="token keyword">PERSIST_ONLY</span> <span class="token operator">|</span> <span class="token variable">@@PERSIST_ONLY.</span>} <em class="replaceable">system_var_name</em>
<span class="token operator">|</span> <span class="token punctuation">[</span><span class="token keyword">SESSION</span> <span class="token operator">|</span> <span class="token variable">@@SESSION.</span> <span class="token operator">|</span> @@<span class="token punctuation">]</span> <em class="replaceable">system_var_name</em>
}</code></pre>
</div>
<p>
<a class="link" href="set-variable.html" title="15.7.6.1 SET Syntax for Variable Assignment">
<code class="literal">
SET
</code>
</a>
syntax for variable assignment enables you to assign values to
different types of variables that affect the operation of the
server or clients:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
User-defined variables. See
<a class="xref" href="user-variables.html" title="11.4 User-Defined Variables">
Section 11.4, “User-Defined Variables”
</a>
.
</p>
</li>
<li class="listitem">
<p>
Stored procedure and function parameters, and stored program
local variables. See
<a class="xref" href="stored-program-variables.html" title="15.6.4 Variables in Stored Programs">
Section 15.6.4, “Variables in Stored Programs”
</a>
.
</p>
</li>
<li class="listitem">
<p>
System variables. See
<a class="xref" href="server-system-variables.html" title="7.1.8 Server System Variables">
Section 7.1.8, “Server System Variables”
</a>
. System variables
also can be set at server startup, as described in
<a class="xref" href="using-system-variables.html" title="7.1.9 Using System Variables">
Section 7.1.9, “Using System Variables”
</a>
.
</p>
</li>
</ul>
</div>
<p>
A
<a class="link" href="set-variable.html" title="15.7.6.1 SET Syntax for Variable Assignment">
<code class="literal">
SET
</code>
</a>
statement that assigns variable values is not written to the
binary log, so in replication scenarios it affects only the host
on which you execute it. To affect all replication hosts,
execute the statement on each host.
</p>
<p>
The following sections describe
<a class="link" href="set-variable.html" title="15.7.6.1 SET Syntax for Variable Assignment">
<code class="literal">
SET
</code>
</a>
syntax for setting variables. They use the
<a class="link" href="assignment-operators.html#operator_assign-equal">
<code class="literal">
=
</code>
</a>
assignment operator, but the
<a class="link" href="assignment-operators.html#operator_assign-value">
<code class="literal">
:=
</code>
</a>
assignment operator is also permitted for this purpose.
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<a class="xref" href="set-variable.html#set-variable-user-variables" title="User-Defined Variable Assignment">
User-Defined Variable Assignment
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="set-variable.html#set-variable-parameters-local-variables" title="Parameter and Local Variable Assignment">
Parameter and Local Variable Assignment
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="set-variable.html#set-variable-system-variables" title="System Variable Assignment">
System Variable Assignment
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="set-variable.html#set-variable-error-handling" title="SET Error Handling">
SET Error Handling
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="set-variable.html#set-variable-multiple-assignments" title="Multiple Variable Assignment">
Multiple Variable Assignment
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="set-variable.html#variable-references-in-expressions" title="System Variable References in Expressions">
System Variable References in Expressions
</a>
</p>
</li>
</ul>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h5 class="title">
<a name="set-variable-user-variables">
</a>
User-Defined Variable Assignment
</h5>
</div>
</div>
</div>
<p>
User-defined variables are created locally within a session
and exist only within the context of that session; see
<a class="xref" href="user-variables.html" title="11.4 User-Defined Variables">
Section 11.4, “User-Defined Variables”
</a>
.
</p>
<p>
A user-defined variable is written as
<code class="literal">
@
<em class="replaceable">
<code>
var_name
</code>
</em>
</code>
and is
assigned an expression value as follows:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa52038967"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SET</span> <span class="token variable">@<em class="replaceable">var_name</em></span> <span class="token operator">=</span> <em class="replaceable">expr</em><span class="token punctuation">;</span></code></pre>
</div>
<p>
Examples:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa61134265"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SET</span> <span class="token variable">@name</span> <span class="token operator">=</span> <span class="token number">43</span><span class="token punctuation">;</span>
<span class="token keyword">SET</span> <span class="token variable">@total_tax</span> <span class="token operator">=</span> <span class="token punctuation">(</span><span class="token keyword">SELECT</span> <span class="token function">SUM</span><span class="token punctuation">(</span>tax<span class="token punctuation">)</span> <span class="token keyword">FROM</span> taxable_transactions<span class="token punctuation">)</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
As demonstrated by those statements,
<em class="replaceable">
<code>
expr
</code>
</em>
can range from simple (a
literal value) to more complex (the value returned by a scalar
subquery).
</p>
<p>
The Performance Schema
<a class="link" href="performance-schema-user-variable-tables.html" title="29.12.10 Performance Schema User-Defined Variable Tables">
<code class="literal">
user_variables_by_thread
</code>
</a>
table
contains information about user-defined variables. See
<a class="xref" href="performance-schema-user-variable-tables.html" title="29.12.10 Performance Schema User-Defined Variable Tables">
Section 29.12.10, “Performance Schema User-Defined Variable Tables”
</a>
.
</p>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h5 class="title">
<a name="set-variable-parameters-local-variables">
</a>
Parameter and Local Variable Assignment
</h5>
</div>
</div>
</div>
<p>
<a class="link" href="set-variable.html" title="15.7.6.1 SET Syntax for Variable Assignment">
<code class="literal">
SET
</code>
</a>
applies to parameters and local variables in the context of
the stored object within which they are defined. The following
procedure uses the
<code class="literal">
increment
</code>
procedure
parameter and
<code class="literal">
counter
</code>
local variable:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa1950027"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">PROCEDURE</span> p<span class="token punctuation">(</span>increment <span class="token datatype">INT</span><span class="token punctuation">)</span>
<span class="token keyword">BEGIN</span>
<span class="token keyword">DECLARE</span> counter <span class="token datatype">INT</span> <span class="token keyword">DEFAULT</span> <span class="token number">0</span><span class="token punctuation">;</span>
<span class="token keyword">WHILE</span> counter <span class="token operator"><</span> <span class="token number">10</span> <span class="token keyword">DO</span>
<span class="token comment" spellcheck="true">-- ... do work ...</span>
<span class="token keyword">SET</span> counter <span class="token operator">=</span> counter <span class="token operator">+</span> increment<span class="token punctuation">;</span>
<span class="token keyword">END</span> <span class="token keyword">WHILE</span><span class="token punctuation">;</span>
<span class="token keyword">END</span><span class="token punctuation">;</span></code></pre>
</div>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h5 class="title">
<a name="set-variable-system-variables">
</a>
System Variable Assignment
</h5>
</div>
</div>
</div>
<p>
The MySQL server maintains system variables that configure its
operation. A system variable can have a global value that
affects server operation as a whole, a session value that
affects the current session, or both. Many system variables
are dynamic and can be changed at runtime using the
<a class="link" href="set-variable.html" title="15.7.6.1 SET Syntax for Variable Assignment">
<code class="literal">
SET
</code>
</a>
statement to affect operation of the current server instance.
<a class="link" href="set-variable.html" title="15.7.6.1 SET Syntax for Variable Assignment">
<code class="literal">
SET
</code>
</a>
can also be used to persist certain system variables to the
<code class="filename">
mysqld-auto.cnf
</code>
file in the data
directory, to affect server operation for subsequent startups.
</p>
<p>
If a
<code class="literal">
SET
</code>
statement is issued for a
sensitive system variable, the query is rewritten to replace
the value with
<span class="quote">
“
<span class="quote">
<code class="literal">
<redacted>
</code>
</span>
”
</span>
before it is logged to the general log and audit log. This
takes place even if secure storage through a keyring component
is not available on the server instance.
</p>
<p>
If you change a session system variable, the value remains in
effect within your session until you change the variable to a
different value or the session ends. The change has no effect
on other sessions.
</p>
<p>
If you change a global system variable, the value is
remembered and used to initialize the session value for new
sessions until you change the variable to a different value or
the server exits. The change is visible to any client that
accesses the global value. However, the change affects the
corresponding session value only for clients that connect
after the change. The global variable change does not affect
the session value for any current client sessions (not even
the session within which the global value change occurs).
</p>
<p>
To make a global system variable setting permanent so that it
applies across server restarts, you can persist it to the
<code class="filename">
mysqld-auto.cnf
</code>
file in the data
directory. It is also possible to make persistent
configuration changes by manually modifying a
<code class="filename">
my.cnf
</code>
option file, but that is more
cumbersome, and an error in a manually entered setting might
not be discovered until much later.
<a class="link" href="set-variable.html" title="15.7.6.1 SET Syntax for Variable Assignment">
<code class="literal">
SET
</code>
</a>
statements that persist system variables are more convenient
and avoid the possibility of malformed settings because
settings with syntax errors do not succeed and do not change
server configuration. For more information about persisting
system variables and the
<code class="filename">
mysqld-auto.cnf
</code>
file, see
<a class="xref" href="persisted-system-variables.html" title="7.1.9.3 Persisted System Variables">
Section 7.1.9.3, “Persisted System Variables”
</a>
.
</p>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
Setting or persisting a global system variable value always
requires special privileges. Setting a session system
variable value normally requires no special privileges and
can be done by any user, although there are exceptions. For
more information, see
<a class="xref" href="system-variable-privileges.html" title="7.1.9.1 System Variable Privileges">
Section 7.1.9.1, “System Variable Privileges”
</a>
.
</p>
</div>
<p>
The following discussion describes the syntax options for
setting and persisting system variables:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
To assign a value to a global system variable, precede the
variable name by the
<code class="literal">
GLOBAL
</code>
keyword or
the
<code class="literal">
@@GLOBAL.
</code>
qualifier:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa54863156"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SET</span> <span class="token keyword">GLOBAL</span> max_connections <span class="token operator">=</span> <span class="token number">1000</span><span class="token punctuation">;</span>
<span class="token keyword">SET</span> <span class="token variable">@@GLOBAL.max_connections</span> <span class="token operator">=</span> <span class="token number">1000</span><span class="token punctuation">;</span></code></pre>
</div>
</li>
<li class="listitem">
<p>
To assign a value to a session system variable, precede
the variable name by the
<code class="literal">
SESSION
</code>
or
<code class="literal">
LOCAL
</code>
keyword, by the
<code class="literal">
@@SESSION.
</code>
,
<code class="literal">
@@LOCAL.
</code>
, or
<code class="literal">
@@
</code>
qualifier, or by no keyword or no modifier at all:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa7530995"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SET</span> <span class="token keyword">SESSION</span> sql_mode <span class="token operator">=</span> <span class="token string">'TRADITIONAL'</span><span class="token punctuation">;</span>
<span class="token keyword">SET</span> <span class="token keyword">LOCAL</span> sql_mode <span class="token operator">=</span> <span class="token string">'TRADITIONAL'</span><span class="token punctuation">;</span>
<span class="token keyword">SET</span> <span class="token variable">@@SESSION.sql_mode</span> <span class="token operator">=</span> <span class="token string">'TRADITIONAL'</span><span class="token punctuation">;</span>
<span class="token keyword">SET</span> <span class="token variable">@@LOCAL.sql_mode</span> <span class="token operator">=</span> <span class="token string">'TRADITIONAL'</span><span class="token punctuation">;</span>
<span class="token keyword">SET</span> <span class="token variable">@@sql_mode</span> <span class="token operator">=</span> <span class="token string">'TRADITIONAL'</span><span class="token punctuation">;</span>
<span class="token keyword">SET</span> sql_mode <span class="token operator">=</span> <span class="token string">'TRADITIONAL'</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
A client can change its own session variables, but not
those of any other client.
</p>
</li>
<li class="listitem">
<p>
To persist a global system variable to the
<code class="filename">
mysqld-auto.cnf
</code>
option file in the
data directory, precede the variable name by the
<code class="literal">
PERSIST
</code>
keyword or the
<code class="literal">
@@PERSIST.
</code>
qualifier:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa67691389"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SET</span> <span class="token keyword">PERSIST</span> max_connections <span class="token operator">=</span> <span class="token number">1000</span><span class="token punctuation">;</span>
<span class="token keyword">SET</span> <span class="token variable">@@PERSIST.max_connections</span> <span class="token operator">=</span> <span class="token number">1000</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
This
<a class="link" href="set-variable.html" title="15.7.6.1 SET Syntax for Variable Assignment">
<code class="literal">
SET
</code>
</a>
syntax enables you to make configuration changes at
runtime that also persist across server restarts. Like
<a class="link" href="set-variable.html" title="15.7.6.1 SET Syntax for Variable Assignment">
<code class="literal">
SET
GLOBAL
</code>
</a>
,
<a class="link" href="set-variable.html" title="15.7.6.1 SET Syntax for Variable Assignment">
<code class="literal">
SET
PERSIST
</code>
</a>
sets the global variable runtime value,
but also writes the variable setting to the
<code class="filename">
mysqld-auto.cnf
</code>
file (replacing any
existing variable setting if there is one).
</p>
</li>
<li class="listitem">
<p>
To persist a global system variable to the
<code class="filename">
mysqld-auto.cnf
</code>
file without setting
the global variable runtime value, precede the variable
name by the
<code class="literal">
PERSIST_ONLY
</code>
keyword or the
<code class="literal">
@@PERSIST_ONLY.
</code>
qualifier:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa17432351"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SET</span> <span class="token keyword">PERSIST_ONLY</span> back_log <span class="token operator">=</span> <span class="token number">100</span><span class="token punctuation">;</span>
<span class="token keyword">SET</span> <span class="token variable">@@PERSIST_ONLY.back_log</span> <span class="token operator">=</span> <span class="token number">100</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
Like
<code class="literal">
PERSIST
</code>
,
<code class="literal">
PERSIST_ONLY
</code>
writes the variable
setting to
<code class="filename">
mysqld-auto.cnf
</code>
. However,
unlike
<code class="literal">
PERSIST
</code>
,
<code class="literal">
PERSIST_ONLY
</code>
does not modify the global
variable runtime value. This makes
<code class="literal">
PERSIST_ONLY
</code>
suitable for configuring
read-only system variables that can be set only at server
startup.
</p>
</li>
</ul>
</div>
<p>
To set a global system variable value to the compiled-in MySQL
default value or a session system variable to the current
corresponding global value, set the variable to the value
<code class="literal">
DEFAULT
</code>
. For example, the following two
statements are identical in setting the session value of
<a class="link" href="server-system-variables.html#sysvar_max_join_size">
<code class="literal">
max_join_size
</code>
</a>
to the current
global value:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa907642"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SET</span> <span class="token variable">@@SESSION.max_join_size</span> <span class="token operator">=</span> <span class="token keyword">DEFAULT</span><span class="token punctuation">;</span>
<span class="token keyword">SET</span> <span class="token variable">@@SESSION.max_join_size</span> <span class="token operator">=</span> <span class="token variable">@@GLOBAL.max_join_size</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
Using
<a class="link" href="set-variable.html" title="15.7.6.1 SET Syntax for Variable Assignment">
<code class="literal">
SET
</code>
</a>
to
persist a global system variable to a value of
<code class="literal">
DEFAULT
</code>
or to its literal default value
assigns the variable its default value and adds a setting for
the variable to
<code class="filename">
mysqld-auto.cnf
</code>
. To
remove the variable from the file, use
<a class="link" href="reset-persist.html" title="15.7.8.7 RESET PERSIST Statement">
<code class="literal">
RESET PERSIST
</code>
</a>
.
</p>
<p>
Some system variables cannot be persisted or are
persist-restricted. See
<a class="xref" href="nonpersistible-system-variables.html" title="7.1.9.4 Nonpersistible and Persist-Restricted System Variables">
Section 7.1.9.4, “Nonpersistible and Persist-Restricted System Variables”
</a>
.
</p>
<p>
A system variable implemented by a plugin can be persisted if
the plugin is installed when the
<a class="link" href="set-variable.html" title="15.7.6.1 SET Syntax for Variable Assignment">
<code class="literal">
SET
</code>
</a>
statement is executed. Assignment of the persisted plugin
variable takes effect for subsequent server restarts if the
plugin is still installed. If the plugin is no longer
installed, the plugin variable no longer exists when the
server reads the
<code class="filename">
mysqld-auto.cnf
</code>
file. In
this case, the server writes a warning to the error log and
continues:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-simple"><div class="docs-select-all right" id="sa36842257"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-simple">currently unknown variable '<em class="replaceable">var_name</em>'
was read from the persisted config file</code></pre>
</div>
<p>
To display system variable names and values:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
Use the
<a class="link" href="show-variables.html" title="15.7.7.41 SHOW VARIABLES Statement">
<code class="literal">
SHOW VARIABLES
</code>
</a>
statement; see
<a class="xref" href="show-variables.html" title="15.7.7.41 SHOW VARIABLES Statement">
Section 15.7.7.41, “SHOW VARIABLES Statement”
</a>
.
</p>
</li>
<li class="listitem">
<p>
Several Performance Schema tables provide system variable
information. See
<a class="xref" href="performance-schema-system-variable-tables.html" title="29.12.14 Performance Schema System Variable Tables">
Section 29.12.14, “Performance Schema System Variable Tables”
</a>
.
</p>
</li>
<li class="listitem">
<p>
The Performance Schema
<a class="link" href="performance-schema-variables-info-table.html" title="29.12.14.2 Performance Schema variables_info Table">
<code class="literal">
variables_info
</code>
</a>
table contains
information showing when and by which user each system
variable was most recently set. See
<a class="xref" href="performance-schema-variables-info-table.html" title="29.12.14.2 Performance Schema variables_info Table">
Section 29.12.14.2, “Performance Schema variables_info Table”
</a>
.
</p>
</li>
<li class="listitem">
<p>
The Performance Schema
<a class="link" href="performance-schema-persisted-variables-table.html" title="29.12.14.1 Performance Schema persisted_variables Table">
<code class="literal">
persisted_variables
</code>
</a>
table
provides an SQL interface to the
<code class="filename">
mysqld-auto.cnf
</code>
file, enabling its
contents to be inspected at runtime using
<a class="link" href="select.html" title="15.2.13 SELECT Statement">
<code class="literal">
SELECT
</code>
</a>
statements. See
<a class="xref" href="performance-schema-persisted-variables-table.html" title="29.12.14.1 Performance Schema persisted_variables Table">
Section 29.12.14.1, “Performance Schema persisted_variables Table”
</a>
.
</p>
</li>
</ul>
</div>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h5 class="title">
<a name="set-variable-error-handling">
</a>
SET Error Handling
</h5>
</div>
</div>
</div>
<p>
If any variable assignment in a
<a class="link" href="set-variable.html" title="15.7.6.1 SET Syntax for Variable Assignment">
<code class="literal">
SET
</code>
</a>
statement fails, the entire statement fails and no variables
are changed, nor is the
<code class="filename">
mysqld-auto.cnf
</code>
file changed.
</p>
<p>
<a class="link" href="set-variable.html" title="15.7.6.1 SET Syntax for Variable Assignment">
<code class="literal">
SET
</code>
</a>
produces an error under the circumstances described here. Most
of the examples show
<a class="link" href="set-variable.html" title="15.7.6.1 SET Syntax for Variable Assignment">
<code class="literal">
SET
</code>
</a>
statements that use keyword syntax (for example,
<code class="literal">
GLOBAL
</code>
or
<code class="literal">
SESSION
</code>
), but
the principles are also true for statements that use the
corresponding modifiers (for example,
<code class="literal">
@@GLOBAL.
</code>
or
<code class="literal">
@@SESSION.
</code>
).
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
Use of
<a class="link" href="set-variable.html" title="15.7.6.1 SET Syntax for Variable Assignment">
<code class="literal">
SET
</code>
</a>
(any variant) to set a read-only variable:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa24986582"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SET</span> <span class="token keyword">GLOBAL</span> version <span class="token operator">=</span> <span class="token string">'abc'</span><span class="token punctuation">;</span>
<span class="token output">ERROR 1238 (HY000)<span class="token punctuation">:</span> Variable 'version' is a read only variable</span></code></pre>
</div>
</li>
<li class="listitem">
<p>
Use of
<code class="literal">
GLOBAL
</code>
,
<code class="literal">
PERSIST
</code>
, or
<code class="literal">
PERSIST_ONLY
</code>
to set a variable that has
only a session value:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa26297130"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SET</span> <span class="token keyword">GLOBAL</span> sql_log_bin <span class="token operator">=</span> <span class="token keyword">ON</span><span class="token punctuation">;</span>
<span class="token output">ERROR 1228 (HY000)<span class="token punctuation">:</span> Variable 'sql_log_bin' is a SESSION
variable and can't be used with SET GLOBAL</span></code></pre>
</div>
</li>
<li class="listitem">
<p>
Use of
<code class="literal">
SESSION
</code>
to set a variable that
has only a global value:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa71771167"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SET</span> <span class="token keyword">SESSION</span> max_connections <span class="token operator">=</span> <span class="token number">1000</span><span class="token punctuation">;</span>
<span class="token output">ERROR 1229 (HY000)<span class="token punctuation">:</span> Variable 'max_connections' is a
GLOBAL variable and should be set with SET GLOBAL</span></code></pre>
</div>
</li>
<li class="listitem">
<p>
Omission of
<code class="literal">
GLOBAL
</code>
,
<code class="literal">
PERSIST
</code>
, or
<code class="literal">
PERSIST_ONLY
</code>
to set a variable that has
only a global value:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa63488095"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SET</span> max_connections <span class="token operator">=</span> <span class="token number">1000</span><span class="token punctuation">;</span>
<span class="token output">ERROR 1229 (HY000)<span class="token punctuation">:</span> Variable 'max_connections' is a
GLOBAL variable and should be set with SET GLOBAL</span></code></pre>
</div>
</li>
<li class="listitem">
<p>
Use of
<code class="literal">
PERSIST
</code>
or
<code class="literal">
PERSIST_ONLY
</code>
to set a variable that
cannot be persisted:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa55690928"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SET</span> <span class="token keyword">PERSIST</span> <span class="token keyword">port</span> <span class="token operator">=</span> <span class="token number">3307</span><span class="token punctuation">;</span>
<span class="token output">ERROR 1238 (HY000)<span class="token punctuation">:</span> Variable 'port' is a read only variable</span>
<span class="token prompt">mysql></span> <span class="token keyword">SET</span> <span class="token keyword">PERSIST_ONLY</span> <span class="token keyword">port</span> <span class="token operator">=</span> <span class="token number">3307</span><span class="token punctuation">;</span>
<span class="token output">ERROR 1238 (HY000)<span class="token punctuation">:</span> Variable 'port' is a non persistent read only variable</span></code></pre>
</div>
</li>
<li class="listitem">
<p>
The
<code class="literal">
@@GLOBAL.
</code>
,
<code class="literal">
@@PERSIST.
</code>
,
<code class="literal">
@@PERSIST_ONLY.
</code>
,
<code class="literal">
@@SESSION.
</code>
, and
<code class="literal">
@@
</code>
modifiers apply only to system variables. An error occurs
for attempts to apply them to user-defined variables,
stored procedure or function parameters, or stored program
local variables.
</p>
</li>
<li class="listitem">
<p>
Not all system variables can be set to
<code class="literal">
DEFAULT
</code>
. In such cases, assigning
<code class="literal">
DEFAULT
</code>
results in an error.
</p>
</li>
<li class="listitem">
<p>
An error occurs for attempts to assign
<code class="literal">
DEFAULT
</code>
to user-defined variables,
stored procedure or function parameters, or stored program
local variables.
</p>
</li>
</ul>
</div>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h5 class="title">
<a name="set-variable-multiple-assignments">
</a>
Multiple Variable Assignment
</h5>
</div>
</div>
</div>
<p>
A
<a class="link" href="set-variable.html" title="15.7.6.1 SET Syntax for Variable Assignment">
<code class="literal">
SET
</code>
</a>
statement can contain multiple variable assignments, separated
by commas. This statement assigns values to a user-defined
variable and a system variable:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa92284593"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SET</span> <span class="token variable">@x</span> <span class="token operator">=</span> <span class="token number">1</span><span class="token punctuation">,</span> <span class="token keyword">SESSION</span> sql_mode <span class="token operator">=</span> <span class="token string">''</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
If you set multiple system variables in a single statement,
the most recent
<code class="literal">
GLOBAL
</code>
,
<code class="literal">
PERSIST
</code>
,
<code class="literal">
PERSIST_ONLY
</code>
,
or
<code class="literal">
SESSION
</code>
keyword in the statement is used
for following assignments that have no keyword specified.
</p>
<p>
Examples of multiple-variable assignment:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa70046662"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SET</span> <span class="token keyword">GLOBAL</span> sort_buffer_size <span class="token operator">=</span> <span class="token number">1000000</span><span class="token punctuation">,</span> <span class="token keyword">SESSION</span> sort_buffer_size <span class="token operator">=</span> <span class="token number">1000000</span><span class="token punctuation">;</span>
<span class="token keyword">SET</span> <span class="token variable">@@GLOBAL.sort_buffer_size</span> <span class="token operator">=</span> <span class="token number">1000000</span><span class="token punctuation">,</span> <span class="token variable">@@LOCAL.sort_buffer_size</span> <span class="token operator">=</span> <span class="token number">1000000</span><span class="token punctuation">;</span>
<span class="token keyword">SET</span> <span class="token keyword">GLOBAL</span> max_connections <span class="token operator">=</span> <span class="token number">1000</span><span class="token punctuation">,</span> sort_buffer_size <span class="token operator">=</span> <span class="token number">1000000</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
The
<code class="literal">
@@GLOBAL.
</code>
,
<code class="literal">
@@PERSIST.
</code>
,
<code class="literal">
@@PERSIST_ONLY.
</code>
,
<code class="literal">
@@SESSION.
</code>
, and
<code class="literal">
@@
</code>
modifiers apply only to the immediately following system
variable, not any remaining system variables. This statement
sets the
<a class="link" href="server-system-variables.html#sysvar_sort_buffer_size">
<code class="literal">
sort_buffer_size
</code>
</a>
global value to 50000 and the session value to 1000000:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa84069354"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SET</span> <span class="token variable">@@GLOBAL.sort_buffer_size</span> <span class="token operator">=</span> <span class="token number">50000</span><span class="token punctuation">,</span> sort_buffer_size <span class="token operator">=</span> <span class="token number">1000000</span><span class="token punctuation">;</span></code></pre>
</div>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h5 class="title">
<a name="variable-references-in-expressions">
</a>
System Variable References in Expressions
</h5>
</div>
</div>
</div>
<p>
To refer to the value of a system variable in expressions, use
one of the
<code class="literal">
@@
</code>
-modifiers (except
<code class="literal">
@@PERSIST.
</code>
and
<code class="literal">
@@PERSIST_ONLY.
</code>
, which are not permitted in
expressions). For example, you can retrieve system variable
values in a
<a class="link" href="select.html" title="15.2.13 SELECT Statement">
<code class="literal">
SELECT
</code>
</a>
statement
like this:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa95236464"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SELECT</span> <span class="token variable">@@GLOBAL.sql_mode</span><span class="token punctuation">,</span> <span class="token variable">@@SESSION.sql_mode</span><span class="token punctuation">,</span> <span class="token variable">@@sql_mode</span><span class="token punctuation">;</span></code></pre>
</div>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
A reference to a system variable in an expression as
<code class="literal">
@@
<em class="replaceable">
<code>
var_name
</code>
</em>
</code>
(with
<code class="literal">
@@
</code>
rather than
<code class="literal">
@@GLOBAL.
</code>
or
<code class="literal">
@@SESSION.
</code>
) returns the session value if
it exists and the global value otherwise. This differs from
<code class="literal">
SET @@
<em class="replaceable">
<code>
var_name
</code>
</em>
=
<em class="replaceable">
<code>
expr
</code>
</em>
</code>
, which always
refers to the session value.
</p>
</div>
</div>
</div>
<br/>
</div>
|
Subsets and Splits