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https://dev.mysql.com/doc/refman/8.4/en/log-file-maintenance.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="log-file-maintenance">
</a>
7.4.6 Server Log Maintenance
</h3>
</div>
</div>
</div>
<a class="indexterm" name="idm46045257425344">
</a>
<a class="indexterm" name="idm46045257423888">
</a>
<a class="indexterm" name="idm46045257422400">
</a>
<p>
As described in
<a class="xref" href="server-logs.html" title="7.4 MySQL Server Logs">
Section 7.4, “MySQL Server Logs”
</a>
, MySQL Server can
create several different log files to help you see what activity
is taking place. However, you must clean up these files regularly
to ensure that the logs do not take up too much disk space.
</p>
<p>
When using MySQL with logging enabled, you may want to back up and
remove old log files from time to time and tell MySQL to start
logging to new files. See
<a class="xref" href="backup-methods.html" title="9.2 Database Backup Methods">
Section 9.2, “Database Backup Methods”
</a>
.
</p>
<p>
On a Linux (Red Hat) installation, you can use the
<code class="literal">
mysql-log-rotate
</code>
script for log maintenance. If
you installed MySQL from an RPM distribution, this script should
have been installed automatically. Be careful with this script if
you are using the binary log for replication. You should not
remove binary logs until you are certain that their contents have
been processed by all replicas.
</p>
<p>
On other systems, you must install a short script yourself that
you start from
<span class="command">
<strong>
cron
</strong>
</span>
(or its equivalent) for
handling log files.
</p>
<p>
Binary log files are automatically removed after the server's
binary log expiration period. Removal of the files can take place
at startup and when the binary log is flushed. The default binary
log expiration period is 30 days. To specify an alternative
expiration period, use the
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_expire_logs_seconds">
<code class="literal">
binlog_expire_logs_seconds
</code>
</a>
system
variable. If you are using replication, you should specify an
expiration period that is no lower than the maximum amount of time
your replicas might lag behind the source. To remove binary logs
on demand, use the
<a class="link" href="purge-binary-logs.html" title="15.4.1.1 PURGE BINARY LOGS Statement">
<code class="literal">
PURGE BINARY
LOGS
</code>
</a>
statement (see
<a class="xref" href="purge-binary-logs.html" title="15.4.1.1 PURGE BINARY LOGS Statement">
Section 15.4.1.1, “PURGE BINARY LOGS Statement”
</a>
).
</p>
<p>
To force MySQL to start using new log files, flush the logs. Log
flushing occurs when you execute a
<a class="link" href="flush.html#flush-logs">
<code class="literal">
FLUSH
LOGS
</code>
</a>
statement or a
<a class="link" href="mysqladmin.html" title="6.5.2 mysqladmin — A MySQL Server Administration Program">
<span class="command">
<strong>
mysqladmin
flush-logs
</strong>
</span>
</a>
,
<a class="link" href="mysqladmin.html" title="6.5.2 mysqladmin — A MySQL Server Administration Program">
<span class="command">
<strong>
mysqladmin refresh
</strong>
</span>
</a>
,
<a class="link" href="mysqldump.html" title="6.5.4 mysqldump — A Database Backup Program">
<span class="command">
<strong>
mysqldump
</strong>
</span>
</a>
<a class="link" href="mysqldump.html#option_mysqldump_flush-logs">
<code class="option">
--flush-logs
</code>
</a>
, or
<a class="link" href="mysqldump.html" title="6.5.4 mysqldump — A Database Backup Program">
<span class="command">
<strong>
mysqldump
</strong>
</span>
</a>
<a class="link" href="mysqldump.html#option_mysqldump_source-data">
<code class="option">
--source-data
</code>
</a>
command. See
<a class="xref" href="flush.html" title="15.7.8.3 FLUSH Statement">
Section 15.7.8.3, “FLUSH Statement”
</a>
,
<a class="xref" href="mysqladmin.html" title="6.5.2 mysqladmin — A MySQL Server Administration Program">
Section 6.5.2, “mysqladmin — A MySQL Server Administration Program”
</a>
, and
<a class="xref" href="mysqldump.html" title="6.5.4 mysqldump — A Database Backup Program">
Section 6.5.4, “mysqldump — A Database Backup Program”
</a>
. In addition, the server flushes the
binary log automatically when current binary log file size reaches
the value of the
<a class="link" href="replication-options-binary-log.html#sysvar_max_binlog_size">
<code class="literal">
max_binlog_size
</code>
</a>
system variable.
</p>
<p>
<a class="link" href="flush.html#flush-logs">
<code class="literal">
FLUSH LOGS
</code>
</a>
supports optional
modifiers to enable selective flushing of individual logs (for
example,
<a class="link" href="flush.html#flush-binary-logs">
<code class="literal">
FLUSH BINARY LOGS
</code>
</a>
). See
<a class="xref" href="flush.html" title="15.7.8.3 FLUSH Statement">
Section 15.7.8.3, “FLUSH Statement”
</a>
.
</p>
<p>
A log-flushing operation has the following effects:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
If binary logging is enabled, the server closes the current
binary log file and opens a new log file with the next
sequence number.
</p>
</li>
<li class="listitem">
<p>
If general query logging or slow query logging to a log file
is enabled, the server closes and reopens the log file.
</p>
</li>
<li class="listitem">
<p>
If the server was started with the
<a class="link" href="server-options.html#option_mysqld_log-error">
<code class="option">
--log-error
</code>
</a>
option to cause the
error log to be written to a file, the server closes and
reopens the log file.
</p>
</li>
</ul>
</div>
<a class="indexterm" name="idm46045257391104">
</a>
<a class="indexterm" name="idm46045257389616">
</a>
<p>
Execution of log-flushing statements or commands requires
connecting to the server using an account that has the
<a class="link" href="privileges-provided.html#priv_reload">
<code class="literal">
RELOAD
</code>
</a>
privilege. On Unix and
Unix-like systems, another way to flush the logs is to send a
signal to the server, which can be done by
<code class="literal">
root
</code>
or the account that owns the server process. (See
<a class="xref" href="unix-signal-response.html" title="6.10 Unix Signal Handling in MySQL">
Section 6.10, “Unix Signal Handling in MySQL”
</a>
.) Signals enable log
flushing to be performed without having to connect to the server:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
A
<code class="literal">
SIGHUP
</code>
signal flushes all the logs.
However,
<code class="literal">
SIGHUP
</code>
has additional effects
other than log flushing that might be undesirable.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
SIGUSR1
</code>
causes the server to flush the
error log, general query log, and slow query log. If you are
interested in flushing only those logs,
<code class="literal">
SIGUSR1
</code>
can be used as a more
<span class="quote">
“
<span class="quote">
lightweight
</span>
”
</span>
signal that does not have the
<code class="literal">
SIGHUP
</code>
effects that are unrelated to logs.
</p>
</li>
</ul>
</div>
<p>
As mentioned previously, flushing the binary log creates a new
binary log file, whereas flushing the general query log, slow
query log, or error log just closes and reopens the log file. For
the latter logs, to cause a new log file to be created on Unix,
rename the current log file first before flushing it. At flush
time, the server opens the new log file with the original name.
For example, if the general query log, slow query log, and error
log files are named
<code class="filename">
mysql.log
</code>
,
<code class="filename">
mysql-slow.log
</code>
, and
<code class="filename">
err.log
</code>
, you can use a series of commands
like this from the command line:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-terminal"><div class="docs-select-all right" id="sa71930736"><div class="copy-help left">Press ⌘+C to 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">cd <em class="replaceable">mysql-data-directory</em>
mv mysql<span class="token punctuation">.</span>log mysql<span class="token punctuation">.</span>log<span class="token punctuation">.</span>old
mv mysql-slow<span class="token punctuation">.</span>log mysql-slow<span class="token punctuation">.</span>log<span class="token punctuation">.</span>old
mv err<span class="token punctuation">.</span>log err<span class="token punctuation">.</span>log<span class="token punctuation">.</span>old
mysqladmin flush-logs</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>
At this point, you can make a backup of
<code class="filename">
mysql.log.old
</code>
,
<code class="filename">
mysql-slow.log.old
</code>
, and
<code class="filename">
err.log.old
</code>
, then remove them from disk.
</p>
<p>
To rename the general query log or slow query log at runtime,
first connect to the server and disable the log:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa3560754"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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>
<span class="token keyword">SET</span> <span class="token keyword">GLOBAL</span> slow_query_log <span class="token operator">=</span> <span class="token string">'OFF'</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
With the logs disabled, rename the log files externally (for
example, from the command line). Then enable the logs again:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa15971180"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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>
<span class="token keyword">SET</span> <span class="token keyword">GLOBAL</span> slow_query_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>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
For the server to recreate a given log file after you have
renamed the file externally, the file location must be writable
by the server. This may not always be the case. For example, on
Linux, the server might write the error log as
<code class="filename">
/var/log/mysqld.log
</code>
, where
<code class="filename">
/var/log
</code>
is owned by
<code class="literal">
root
</code>
and not writable by
<a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
<span class="command">
<strong>
mysqld
</strong>
</span>
</a>
. In this case, log-flushing operations
fail to create a new log file.
</p>
<p>
To handle this situation, you must manually create the new log
file with the proper ownership after renaming the original log
file. For example, execute these commands as
<code class="literal">
root
</code>
:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-terminal"><div class="docs-select-all right" id="sa74908276"><div class="copy-help left">Press ⌘+C to 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">mv /var/log/mysqld<span class="token punctuation">.</span>log /var/log/mysqld<span class="token punctuation">.</span>log<span class="token punctuation">.</span>old
install <span class="token property">-omysql</span> <span class="token property">-gmysql</span> <span class="token property">-m0644</span> /dev/null /var/log/mysqld<span class="token punctuation">.</span>log</code></pre>
</div>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/innodb-undo-tablespaces.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="innodb-undo-tablespaces">
</a>
17.6.3.4 Undo Tablespaces
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045165289840">
</a>
<a class="indexterm" name="idm46045165288832">
</a>
<a class="indexterm" name="idm46045165287824">
</a>
<p>
Undo tablespaces contain undo logs, which are collections of
records containing information about how to undo the latest change
by a transaction to a clustered index record.
</p>
<p>
Undo tablespaces are described under the following topics in this
section:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<a class="xref" href="innodb-undo-tablespaces.html#innodb-default-undo-tablespaces" title="Default Undo Tablespaces">
Default Undo Tablespaces
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="innodb-undo-tablespaces.html#innodb--undo-tablespace-size" title="Undo Tablespace Size">
Undo Tablespace Size
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="innodb-undo-tablespaces.html#innodb-add-undo-tablespaces" title="Adding Undo Tablespaces">
Adding Undo Tablespaces
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="innodb-undo-tablespaces.html#innodb-drop-undo-tablespaces" title="Dropping Undo Tablespaces">
Dropping Undo Tablespaces
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="innodb-undo-tablespaces.html#innodb-move-undo-tablespaces" title="Moving Undo Tablespaces">
Moving Undo Tablespaces
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="innodb-undo-tablespaces.html#innodb-undo-tablespace-rollback-segments" title="Configuring the Number of Rollback Segments">
Configuring the Number of Rollback Segments
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="innodb-undo-tablespaces.html#truncate-undo-tablespace" title="Truncating Undo Tablespaces">
Truncating Undo Tablespaces
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="innodb-undo-tablespaces.html#innodb-undo-tablespace-status-variables" title="Undo Tablespace Status Variables">
Undo Tablespace Status Variables
</a>
</p>
</li>
</ul>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h5 class="title">
<a name="innodb-default-undo-tablespaces">
</a>
Default Undo Tablespaces
</h5>
</div>
</div>
</div>
<p>
Two default undo tablespaces are created when the MySQL instance
is initialized. Default undo tablespaces are created at
initialization time to provide a location for rollback segments
that must exist before SQL statements can be accepted. A minimum
of two undo tablespaces is required to support automated
truncation of undo tablespaces. See
<a class="xref" href="innodb-undo-tablespaces.html#truncate-undo-tablespace" title="Truncating Undo Tablespaces">
Truncating Undo Tablespaces
</a>
.
</p>
<p>
Default undo tablespaces are created in the location defined by
the
<a class="link" href="innodb-parameters.html#sysvar_innodb_undo_directory">
<code class="literal">
innodb_undo_directory
</code>
</a>
variable. If the
<a class="link" href="innodb-parameters.html#sysvar_innodb_undo_directory">
<code class="literal">
innodb_undo_directory
</code>
</a>
variable
is undefined, default undo tablespaces are created in the data
directory. Default undo tablespace data files are named
<code class="filename">
undo_001
</code>
and
<code class="filename">
undo_002
</code>
.
The corresponding undo tablespace names defined in the data
dictionary are
<code class="literal">
innodb_undo_001
</code>
and
<code class="literal">
innodb_undo_002
</code>
.
</p>
<p>
Additional undo tablespaces can be created at runtime using SQL
statements. See
<a class="xref" href="innodb-undo-tablespaces.html#innodb-add-undo-tablespaces" title="Adding Undo Tablespaces">
Adding Undo Tablespaces
</a>
.
</p>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h5 class="title">
<a name="innodb--undo-tablespace-size">
</a>
Undo Tablespace Size
</h5>
</div>
</div>
</div>
<p>
The initial undo tablespace size is normally 16MiB. The initial
size may differ when a new undo tablespace is created by a
truncate operation. In this case, if the file extension size is
larger than 16MB, and the previous file extension occurred
within the last second, the new undo tablespace is created at a
quarter of the size defined by the
<a class="link" href="innodb-parameters.html#sysvar_innodb_max_undo_log_size">
<code class="literal">
innodb_max_undo_log_size
</code>
</a>
variable.
</p>
<p>
An undo tablespace is extended by a minimum of 16MB. To handle
aggressive growth, the file extension size is doubled if the
previous file extension happened less than 0.1 seconds earlier.
Doubling of the extension size can occur multiple times to a
maximum of 256MB. If the previous file extension occurred more
than 0.1 seconds earlier, the extension size is reduced by half,
which can also occur multiple times, to a minimum of 16MB. If
the
<code class="literal">
AUTOEXTEND_SIZE
</code>
option is defined for an
undo tablespace, it is extended by the greater of the
<code class="literal">
AUTOEXTEND_SIZE
</code>
setting and the extension
size determined by the logic described above. For information
about the
<code class="literal">
AUTOEXTEND_SIZE
</code>
option, see
<a class="xref" href="innodb-tablespace-autoextend-size.html" title="17.6.3.9 Tablespace AUTOEXTEND_SIZE Configuration">
Section 17.6.3.9, “Tablespace AUTOEXTEND_SIZE Configuration”
</a>
.
</p>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h5 class="title">
<a name="innodb-add-undo-tablespaces">
</a>
Adding Undo Tablespaces
</h5>
</div>
</div>
</div>
<p>
Because undo logs can become large during long-running
transactions, creating additional undo tablespaces can help
prevent individual undo tablespaces from becoming too large.
Additional undo tablespaces can be created at runtime using
<a class="link" href="create-tablespace.html" title="15.1.21 CREATE TABLESPACE Statement">
<code class="literal">
CREATE UNDO
TABLESPACE
</code>
</a>
syntax.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa77258177"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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">UNDO</span> <span class="token keyword">TABLESPACE</span> <em class="replaceable">tablespace_name</em> <span class="token keyword">ADD</span> <span class="token keyword">DATAFILE</span> <span class="token string">'<em class="replaceable">file_name</em>.ibu'</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
The undo tablespace file name must have an
<code class="filename">
.ibu
</code>
extension. It is not permitted to
specify a relative path when defining the undo tablespace file
name. A fully qualified path is permitted, but the path must be
known to
<code class="literal">
InnoDB
</code>
. Known paths are those
defined by the
<a class="link" href="innodb-parameters.html#sysvar_innodb_directories">
<code class="literal">
innodb_directories
</code>
</a>
variable.
Unique undo tablespace file names are recommended to avoid
potential file name conflicts when moving or cloning data.
</p>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
In a replication environment, the source and each replica must
have its own undo tablespace file directory. Replicating the
creation of an undo tablespace file to a common directory
would cause a file name conflict.
</p>
</div>
<p>
At startup, directories defined by the
<a class="link" href="innodb-parameters.html#sysvar_innodb_directories">
<code class="literal">
innodb_directories
</code>
</a>
variable are
scanned for undo tablespace files. (The scan also traverses
subdirectories.) Directories defined by the
<a class="link" href="innodb-parameters.html#sysvar_innodb_data_home_dir">
<code class="literal">
innodb_data_home_dir
</code>
</a>
,
<a class="link" href="innodb-parameters.html#sysvar_innodb_undo_directory">
<code class="literal">
innodb_undo_directory
</code>
</a>
, and
<a class="link" href="server-system-variables.html#sysvar_datadir">
<code class="literal">
datadir
</code>
</a>
variables are
automatically appended to the
<a class="link" href="innodb-parameters.html#sysvar_innodb_directories">
<code class="literal">
innodb_directories
</code>
</a>
value
regardless of whether the
<a class="link" href="innodb-parameters.html#sysvar_innodb_directories">
<code class="literal">
innodb_directories
</code>
</a>
variable is
defined explicitly. An undo tablespace can therefore reside in
paths defined by any of those variables.
</p>
<p>
If the undo tablespace file name does not include a path, the
undo tablespace is created in the directory defined by the
<a class="link" href="innodb-parameters.html#sysvar_innodb_undo_directory">
<code class="literal">
innodb_undo_directory
</code>
</a>
variable.
If that variable is undefined, the undo tablespace is created in
the data directory.
</p>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
The
<code class="literal">
InnoDB
</code>
recovery process requires that
undo tablespace files reside in known directories. Undo
tablespace files must be discovered and opened before redo
recovery and before other data files are opened to permit
uncommitted transactions and data dictionary changes to be
rolled back. An undo tablespace not found before recovery
cannot be used, which can lead to database inconsistencies. An
error message is reported at startup if an undo tablespace
known to the data dictionary is not found. The known directory
requirement also supports undo tablespace portability. See
<a class="xref" href="innodb-undo-tablespaces.html#innodb-move-undo-tablespaces" title="Moving Undo Tablespaces">
Moving Undo Tablespaces
</a>
.
</p>
</div>
<p>
To create undo tablespaces in a path relative to the data
directory, set the
<a class="link" href="innodb-parameters.html#sysvar_innodb_undo_directory">
<code class="literal">
innodb_undo_directory
</code>
</a>
variable
to the relative path, and specify the file name only when
creating an undo tablespace.
</p>
<p>
To view undo tablespace names and paths, query
<a class="link" href="information-schema-files-table.html" title="28.3.15 The INFORMATION_SCHEMA FILES Table">
<code class="literal">
INFORMATION_SCHEMA.FILES
</code>
</a>
:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa23043024"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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> TABLESPACE_NAME<span class="token punctuation">,</span> FILE_NAME <span class="token keyword">FROM</span> INFORMATION_SCHEMA<span class="token punctuation">.</span>FILES
<span class="token keyword">WHERE</span> FILE_TYPE <span class="token operator">LIKE</span> <span class="token string">'UNDO LOG'</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
A MySQL instance supports up to 127 undo tablespaces including
the two default undo tablespaces created when the MySQL instance
is initialized.
</p>
<p>
Undo tablespaces can be dropped using
<a class="link" href="alter-tablespace.html" title="15.1.10 ALTER TABLESPACE Statement">
<code class="literal">
DROP UNDO
TABALESPACE
</code>
</a>
syntax. See
<a class="xref" href="innodb-undo-tablespaces.html#innodb-drop-undo-tablespaces" title="Dropping Undo Tablespaces">
Dropping Undo Tablespaces
</a>
.
</p>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h5 class="title">
<a name="innodb-drop-undo-tablespaces">
</a>
Dropping Undo Tablespaces
</h5>
</div>
</div>
</div>
<p>
Undo tablespaces created using
<a class="link" href="create-tablespace.html" title="15.1.21 CREATE TABLESPACE Statement">
<code class="literal">
CREATE UNDO
TABLESPACE
</code>
</a>
syntax can be dropped at runtime using
<a class="link" href="alter-tablespace.html" title="15.1.10 ALTER TABLESPACE Statement">
<code class="literal">
DROP UNDO
TABALESPACE
</code>
</a>
syntax.
</p>
<p>
An undo tablespace must be empty before it can be dropped. To
empty an undo tablespace, the undo tablespace must first be
marked as inactive using
<a class="link" href="alter-tablespace.html" title="15.1.10 ALTER TABLESPACE Statement">
<code class="literal">
ALTER UNDO
TABLESPACE
</code>
</a>
syntax so that the tablespace is no longer
used for assigning rollback segments to new transactions.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa82601252"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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">UNDO</span> <span class="token keyword">TABLESPACE</span> <em class="replaceable">tablespace_name</em> <span class="token keyword">SET</span> <span class="token keyword">INACTIVE</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
After an undo tablespace is marked as inactive, transactions
currently using rollback segments in the undo tablespace are
permitted to finish, as are any transactions started before
those transactions are completed. After transactions are
completed, the purge system frees the rollback segments in the
undo tablespace, and the undo tablespace is truncated to its
initial size. (The same process is used when truncating undo
tablespaces. See
<a class="xref" href="innodb-undo-tablespaces.html#truncate-undo-tablespace" title="Truncating Undo Tablespaces">
Truncating Undo Tablespaces
</a>
.)
Once the undo tablespace is empty, it can be dropped.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa19260691"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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">UNDO</span> <span class="token keyword">TABLESPACE</span> <em class="replaceable">tablespace_name</em><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>
Alternatively, the undo tablespace can be left in an empty
state and reactivated later, if needed, by issuing an
<a class="link" href="alter-tablespace.html" title="15.1.10 ALTER TABLESPACE Statement">
<code class="literal">
ALTER UNDO
TABLESPACE
<em class="replaceable">
<code>
tablespace_name
</code>
</em>
SET
ACTIVE
</code>
</a>
statement.
</p>
</div>
<p>
The state of an undo tablespace can be monitored by querying the
Information Schema
<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>
table.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa50053721"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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 punctuation">,</span> STATE <span class="token keyword">FROM</span> INFORMATION_SCHEMA<span class="token punctuation">.</span>INNODB_TABLESPACES
<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">tablespace_name</em>'</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
An
<code class="literal">
inactive
</code>
state indicates that rollback
segments in an undo tablespace are no longer used by new
transactions. An
<code class="literal">
empty
</code>
state indicates that
an undo tablespace is empty and ready to be dropped, or ready to
be made active again using an
<a class="link" href="alter-tablespace.html" title="15.1.10 ALTER TABLESPACE Statement">
<code class="literal">
ALTER UNDO
TABLESPACE
<em class="replaceable">
<code>
tablespace_name
</code>
</em>
SET
ACTIVE
</code>
</a>
statement. Attempting to drop an undo
tablespace that is not empty returns an error.
</p>
<p>
The default undo tablespaces (
<code class="literal">
innodb_undo_001
</code>
and
<code class="literal">
innodb_undo_002
</code>
) created when the MySQL
instance is initialized cannot be dropped. They can, however, be
made inactive using an
<a class="link" href="alter-tablespace.html" title="15.1.10 ALTER TABLESPACE Statement">
<code class="literal">
ALTER UNDO
TABLESPACE
<em class="replaceable">
<code>
tablespace_name
</code>
</em>
SET
INACTIVE
</code>
</a>
statement. Before a default undo tablespace
can be made inactive, there must be an undo tablespace to take
its place. A minimum of two active undo tablespaces are required
at all times to support automated truncation of undo
tablespaces.
</p>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h5 class="title">
<a name="innodb-move-undo-tablespaces">
</a>
Moving Undo Tablespaces
</h5>
</div>
</div>
</div>
<p>
Undo tablespaces created with
<a class="link" href="create-tablespace.html" title="15.1.21 CREATE TABLESPACE Statement">
<code class="literal">
CREATE UNDO
TABLESPACE
</code>
</a>
syntax can be moved while the server is
offline to any known directory. Known directories are those
defined by the
<a class="link" href="innodb-parameters.html#sysvar_innodb_directories">
<code class="literal">
innodb_directories
</code>
</a>
variable.
Directories defined by
<a class="link" href="innodb-parameters.html#sysvar_innodb_data_home_dir">
<code class="literal">
innodb_data_home_dir
</code>
</a>
,
<a class="link" href="innodb-parameters.html#sysvar_innodb_undo_directory">
<code class="literal">
innodb_undo_directory
</code>
</a>
, and
<a class="link" href="server-system-variables.html#sysvar_datadir">
<code class="literal">
datadir
</code>
</a>
are automatically
appended to the
<a class="link" href="innodb-parameters.html#sysvar_innodb_directories">
<code class="literal">
innodb_directories
</code>
</a>
value
regardless of whether the
<a class="link" href="innodb-parameters.html#sysvar_innodb_directories">
<code class="literal">
innodb_directories
</code>
</a>
variable is
defined explicitly. Those directories and their subdirectories
are scanned at startup for undo tablespaces files. An undo
tablespace file moved to any of those directories is discovered
at startup and assumed to be the undo tablespace that was moved.
</p>
<p>
The default undo tablespaces (
<code class="literal">
innodb_undo_001
</code>
and
<code class="literal">
innodb_undo_002
</code>
) created when the MySQL
instance is initialized must reside in the directory defined by
the
<a class="link" href="innodb-parameters.html#sysvar_innodb_undo_directory">
<code class="literal">
innodb_undo_directory
</code>
</a>
variable. If the
<a class="link" href="innodb-parameters.html#sysvar_innodb_undo_directory">
<code class="literal">
innodb_undo_directory
</code>
</a>
variable
is undefined, default undo tablespaces reside in the data
directory. If default undo tablespaces are moved while the
server is offline, the server must be started with the
<a class="link" href="innodb-parameters.html#sysvar_innodb_undo_directory">
<code class="literal">
innodb_undo_directory
</code>
</a>
variable
configured to the new directory.
</p>
<p>
The I/O patterns for undo logs make undo tablespaces good
candidates for
<a class="link" href="glossary.html#glos_ssd" title="SSD">
SSD
</a>
storage.
</p>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h5 class="title">
<a name="innodb-undo-tablespace-rollback-segments">
</a>
Configuring the Number of Rollback Segments
</h5>
</div>
</div>
</div>
<p>
The
<a class="link" href="innodb-parameters.html#sysvar_innodb_rollback_segments">
<code class="literal">
innodb_rollback_segments
</code>
</a>
variable defines the number of
<a class="link" href="glossary.html#glos_rollback_segment" title="rollback segment">
rollback segments
</a>
allocated to each undo tablespace and to the global temporary
tablespace. The
<a class="link" href="innodb-parameters.html#sysvar_innodb_rollback_segments">
<code class="literal">
innodb_rollback_segments
</code>
</a>
variable can be configured at startup or while the server is
running.
</p>
<p>
The default setting for
<a class="link" href="innodb-parameters.html#sysvar_innodb_rollback_segments">
<code class="literal">
innodb_rollback_segments
</code>
</a>
is
128, which is also the maximum value. For information about the
number of transactions that a rollback segment supports, see
<a class="xref" href="innodb-undo-logs.html" title="17.6.6 Undo Logs">
Section 17.6.6, “Undo Logs”
</a>
.
</p>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h5 class="title">
<a name="truncate-undo-tablespace">
</a>
Truncating Undo Tablespaces
</h5>
</div>
</div>
</div>
<a class="indexterm" name="idm46045165195392">
</a>
<a class="indexterm" name="idm46045165194384">
</a>
<a class="indexterm" name="idm46045165193376">
</a>
<p>
There are two methods of truncating undo tablespaces, which can
be used individually or in combination to manage undo tablespace
size. One method is automated, enabled using configuration
variables. The other method is manual, performed using SQL
statements.
</p>
<p>
The automated method does not require monitoring undo tablespace
size and, once enabled, it performs deactivation, truncation,
and reactivation of undo tablespaces without manual
intervention. The manual truncation method may be preferable if
you want to control when undo tablespaces are taken offline for
truncation. For example, you may want to avoid truncating undo
tablespaces during peak workload times.
</p>
<h6>
<a name="idm46045165190784">
</a>
Automated Truncation
</h6>
<p>
Automated truncation of undo tablespaces requires a minimum of
two active undo tablespaces, which ensures that one undo
tablespace remains active while the other is taken offline to be
truncated. By default, two undo tablespaces are created when the
MySQL instance is initialized.
</p>
<p>
To have undo tablespaces automatically truncated, enable the
<a class="link" href="innodb-parameters.html#sysvar_innodb_undo_log_truncate">
<code class="literal">
innodb_undo_log_truncate
</code>
</a>
variable. For example:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa6565221"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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> innodb_undo_log_truncate<span class="token operator">=</span><span class="token keyword">ON</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
When the
<a class="link" href="innodb-parameters.html#sysvar_innodb_undo_log_truncate">
<code class="literal">
innodb_undo_log_truncate
</code>
</a>
variable is enabled, undo tablespaces that exceed the size limit
defined by the
<a class="link" href="innodb-parameters.html#sysvar_innodb_max_undo_log_size">
<code class="literal">
innodb_max_undo_log_size
</code>
</a>
variable are subject to truncation. The
<a class="link" href="innodb-parameters.html#sysvar_innodb_max_undo_log_size">
<code class="literal">
innodb_max_undo_log_size
</code>
</a>
variable is dynamic and has a default value of 1073741824 bytes
(1024 MiB).
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa77446298"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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">@@innodb_max_undo_log_size</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>
<span class="token output"><span class="token punctuation">|</span> @@innodb_max_undo_log_size <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>
<span class="token output"><span class="token punctuation">|</span> 1073741824 <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></code></pre>
</div>
<p>
When the
<a class="link" href="innodb-parameters.html#sysvar_innodb_undo_log_truncate">
<code class="literal">
innodb_undo_log_truncate
</code>
</a>
variable is enabled:
</p>
<div class="orderedlist">
<ol class="orderedlist" type="1">
<li class="listitem">
<p>
Default and user-defined undo tablespaces that exceed the
<a class="link" href="innodb-parameters.html#sysvar_innodb_max_undo_log_size">
<code class="literal">
innodb_max_undo_log_size
</code>
</a>
setting are marked for truncation. Selection of an undo
tablespace for truncation is performed in a circular fashion
to avoid truncating the same undo tablespace each time.
</p>
</li>
<li class="listitem">
<p>
Rollback segments residing in the selected undo tablespace
are made inactive so that they are not assigned to new
transactions. Existing transactions that are currently using
rollback segments are permitted to finish.
</p>
</li>
<li class="listitem">
<p>
The
<a class="link" href="glossary.html#glos_purge" title="purge">
purge
</a>
system empties
rollback segments by freeing undo logs that are no longer in
use.
</p>
</li>
<li class="listitem">
<p>
After all rollback segments in the undo tablespace are
freed, the truncate operation runs and truncates the undo
tablespace to its initial size.
</p>
<p>
The size of an undo tablespace after a truncate operation
may be larger than the initial size due to immediate use
following the completion of the operation.
</p>
<p>
The
<a class="link" href="innodb-parameters.html#sysvar_innodb_undo_directory">
<code class="literal">
innodb_undo_directory
</code>
</a>
variable defines the location of default undo tablespace
files. If the
<a class="link" href="innodb-parameters.html#sysvar_innodb_undo_directory">
<code class="literal">
innodb_undo_directory
</code>
</a>
variable is undefined, default undo tablespaces reside in
the data directory. The location of all undo tablespace
files including user-defined undo tablespaces created using
<a class="link" href="create-tablespace.html" title="15.1.21 CREATE TABLESPACE Statement">
<code class="literal">
CREATE
UNDO TABLESPACE
</code>
</a>
syntax can be determined by
querying the Information Schema
<a class="link" href="information-schema-files-table.html" title="28.3.15 The INFORMATION_SCHEMA FILES Table">
<code class="literal">
FILES
</code>
</a>
table:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa491725"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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> TABLESPACE_NAME<span class="token punctuation">,</span> FILE_NAME <span class="token keyword">FROM</span> INFORMATION_SCHEMA<span class="token punctuation">.</span>FILES <span class="token keyword">WHERE</span> FILE_TYPE <span class="token operator">LIKE</span> <span class="token string">'UNDO LOG'</span><span class="token punctuation">;</span></code></pre>
</div>
</li>
<li class="listitem">
<p>
Rollback segments are reactivated so that they can be
assigned to new transactions.
</p>
</li>
</ol>
</div>
<h6>
<a name="idm46045165165936">
</a>
Manual Truncation
</h6>
<p>
Manual truncation of undo tablespaces requires a minimum of
three active undo tablespaces. Two active undo tablespaces are
required at all times to support the possibility that automated
truncation is enabled. A minimum of three undo tablespaces
satisfies this requirement while permitting an undo tablespace
to be taken offline manually.
</p>
<p>
To manually initiate truncation of an undo tablespace,
deactivate the undo tablespace by issuing the following
statement:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa90950635"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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">UNDO</span> <span class="token keyword">TABLESPACE</span> <em class="replaceable">tablespace_name</em> <span class="token keyword">SET</span> <span class="token keyword">INACTIVE</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
After the undo tablespace is marked as inactive, transactions
currently using rollback segments in the undo tablespace are
permitted to finish, as are any transactions started before
those transactions are completed. After transactions are
completed, the purge system frees the rollback segments in the
undo tablespace, the undo tablespace is truncated to its initial
size, and the undo tablespace state changes from
<code class="literal">
inactive
</code>
to
<code class="literal">
empty
</code>
.
</p>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
When an
<code class="literal">
ALTER UNDO TABLESPACE
<em class="replaceable">
<code>
tablespace_name
</code>
</em>
SET
INACTIVE
</code>
statement deactivates an undo tablespace,
the purge thread looks for that undo tablespace at the next
opportunity. Once the undo tablespace is found and marked for
truncation, the purge thread returns with increased frequency
to quickly empty and truncate the undo tablespace.
</p>
</div>
<p>
To check the state of an undo tablespace, query the Information
Schema
<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>
table.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa17428241"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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 punctuation">,</span> STATE <span class="token keyword">FROM</span> INFORMATION_SCHEMA<span class="token punctuation">.</span>INNODB_TABLESPACES
<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">tablespace_name</em>'</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
Once the undo tablespace is in an
<code class="literal">
empty
</code>
state, it can be reactivated by issuing the following statement:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa8293818"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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">UNDO</span> <span class="token keyword">TABLESPACE</span> <em class="replaceable">tablespace_name</em> <span class="token keyword">SET</span> <span class="token keyword">ACTIVE</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
An undo tablespace in an
<code class="literal">
empty
</code>
state can also
be dropped. See
<a class="xref" href="innodb-undo-tablespaces.html#innodb-drop-undo-tablespaces" title="Dropping Undo Tablespaces">
Dropping Undo Tablespaces
</a>
.
</p>
<h6>
<a name="idm46045165151776">
</a>
Expediting Automated Truncation of Undo Tablespaces
</h6>
<p>
The purge thread is responsible for emptying and truncating undo
tablespaces. By default, the purge thread looks for undo
tablespaces to truncate once every 128 times that purge is
invoked. The frequency with which the purge thread looks for
undo tablespaces to truncate is controlled by the
<a class="link" href="innodb-parameters.html#sysvar_innodb_purge_rseg_truncate_frequency">
<code class="literal">
innodb_purge_rseg_truncate_frequency
</code>
</a>
variable, which has a default setting of 128.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa3833177"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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">@@innodb_purge_rseg_truncate_frequency</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> @@innodb_purge_rseg_truncate_frequency <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> 128 <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>
<p>
To increase the frequency, decrease the
<a class="link" href="innodb-parameters.html#sysvar_innodb_purge_rseg_truncate_frequency">
<code class="literal">
innodb_purge_rseg_truncate_frequency
</code>
</a>
setting. For example, to have the purge thread look for undo
tablespaces once every 32 times that purge is invoked, set
<a class="link" href="innodb-parameters.html#sysvar_innodb_purge_rseg_truncate_frequency">
<code class="literal">
innodb_purge_rseg_truncate_frequency
</code>
</a>
to 32.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa85578308"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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> innodb_purge_rseg_truncate_frequency<span class="token operator">=</span><span class="token number">32</span><span class="token punctuation">;</span></code></pre>
</div>
<h6>
<a name="idm46045165143520">
</a>
Performance Impact of Truncating Undo Tablespace Files
</h6>
<p>
When an undo tablespace is truncated, the rollback segments in
the undo tablespace are deactivated. The active rollback
segments in other undo tablespaces assume responsibility for the
entire system load, which may result in a slight performance
degradation. The extent to which performance is affected depends
on a number of factors:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
Number of undo tablespaces
</p>
</li>
<li class="listitem">
<p>
Number of undo logs
</p>
</li>
<li class="listitem">
<p>
Undo tablespace size
</p>
</li>
<li class="listitem">
<p>
Speed of the I/O subsystem
</p>
</li>
<li class="listitem">
<p>
Existing long running transactions
</p>
</li>
<li class="listitem">
<p>
System load
</p>
</li>
</ul>
</div>
<p>
The easiest way to avoid the potential performance impact is to
increase the number of undo tablespaces.
</p>
<h6>
<a name="idm46045165136512">
</a>
Monitoring Undo Tablespace Truncation
</h6>
<p>
<code class="literal">
undo
</code>
and
<code class="literal">
purge
</code>
subsystem
counters are provided for monitoring background activities
associated with undo log truncation. For counter names and
descriptions, query the Information Schema
<a class="link" href="information-schema-innodb-metrics-table.html" title="28.4.21 The INFORMATION_SCHEMA INNODB_METRICS Table">
<code class="literal">
INNODB_METRICS
</code>
</a>
table.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa19454764"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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 punctuation">,</span> SUBSYSTEM<span class="token punctuation">,</span> <span class="token keyword">COMMENT</span> <span class="token keyword">FROM</span> INFORMATION_SCHEMA<span class="token punctuation">.</span>INNODB_METRICS <span class="token keyword">WHERE</span> <span class="token keyword">NAME</span> <span class="token operator">LIKE</span> <span class="token string">'%truncate%'</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
For information about enabling counters and querying counter
data, see
<a class="xref" href="innodb-information-schema-metrics-table.html" title="17.15.6 InnoDB INFORMATION_SCHEMA Metrics Table">
Section 17.15.6, “InnoDB INFORMATION_SCHEMA Metrics Table”
</a>
.
</p>
<h6>
<a name="idm46045165131072">
</a>
Undo Tablespace Truncation Limit
</h6>
<p>
The number of truncate operations on the same undo tablespace
between checkpoints is limited to 64. The limit prevents
potential issues caused by an excessive number of undo
tablespace truncate operations, which can occur if
<a class="link" href="innodb-parameters.html#sysvar_innodb_max_undo_log_size">
<code class="literal">
innodb_max_undo_log_size
</code>
</a>
is set
too low on a busy system, for example. If the limit is exceeded,
an undo tablespace can still be made inactive, but it is not
truncated until after the next checkpoint. In MySQL
8.4 the limit is 50000.
</p>
<h6>
<a name="idm46045165128512">
</a>
Undo Tablespace Truncation Recovery
</h6>
<p>
An undo tablespace truncate operation creates a temporary
<code class="filename">
undo_
<em class="replaceable">
<code>
space_number
</code>
</em>
_trunc.log
</code>
file in the server log directory. That log directory is defined
by
<a class="link" href="innodb-parameters.html#sysvar_innodb_log_group_home_dir">
<code class="literal">
innodb_log_group_home_dir
</code>
</a>
.
If a system failure occurs during the truncate operation, the
temporary log file permits the startup process to identify undo
tablespaces that were being truncated and to continue the
operation.
</p>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h5 class="title">
<a name="innodb-undo-tablespace-status-variables">
</a>
Undo Tablespace Status Variables
</h5>
</div>
</div>
</div>
<p>
The following status variables permit tracking the total number
of undo tablespaces, implicit
(
<code class="literal">
InnoDB
</code>
-created) undo tablespaces, explicit
(user-created) undo tablespaces, and the number of active undo
tablespaces:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa421655"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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">STATUS</span> <span class="token operator">LIKE</span> <span class="token string">'Innodb_undo_tablespaces%'</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> 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 class="token punctuation">-</span><span class="token punctuation">-</span><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> Innodb_undo_tablespaces_total <span class="token punctuation">|</span> 2 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> Innodb_undo_tablespaces_implicit <span class="token punctuation">|</span> 2 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> Innodb_undo_tablespaces_explicit <span class="token punctuation">|</span> 0 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> Innodb_undo_tablespaces_active <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 class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="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 status variable descriptions, see
<a class="xref" href="server-status-variables.html" title="7.1.10 Server Status Variables">
Section 7.1.10, “Server Status Variables”
</a>
.
</p>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/index-condition-pushdown-optimization.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="index-condition-pushdown-optimization">
</a>
10.2.1.6 Index Condition Pushdown Optimization
</h4>
</div>
</div>
</div>
<p>
Index Condition Pushdown (ICP) is an optimization for the case
where MySQL retrieves rows from a table using an index.
Without ICP, the storage engine traverses the index to locate
rows in the base table and returns them to the MySQL server
which evaluates the
<code class="literal">
WHERE
</code>
condition for the
rows. With ICP enabled, and if parts of the
<code class="literal">
WHERE
</code>
condition can be evaluated by using
only columns from the index, the MySQL server pushes this part
of the
<code class="literal">
WHERE
</code>
condition down to the storage
engine. The storage engine then evaluates the pushed index
condition by using the index entry and only if this is
satisfied is the row read from the table. ICP can reduce the
number of times the storage engine must access the base table
and the number of times the MySQL server must access the
storage engine.
</p>
<p>
Applicability of the Index Condition Pushdown optimization is
subject to these conditions:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
ICP is used for the
<a class="link" href="explain-output.html#jointype_range">
<code class="literal">
range
</code>
</a>
,
<a class="link" href="explain-output.html#jointype_ref">
<code class="literal">
ref
</code>
</a>
,
<a class="link" href="explain-output.html#jointype_eq_ref">
<code class="literal">
eq_ref
</code>
</a>
, and
<a class="link" href="explain-output.html#jointype_ref_or_null">
<code class="literal">
ref_or_null
</code>
</a>
access
methods when there is a need to access full table rows.
</p>
</li>
<li class="listitem">
<p>
ICP can be used for
<a class="link" href="innodb-storage-engine.html" title="Chapter 17 The InnoDB Storage Engine">
<code class="literal">
InnoDB
</code>
</a>
and
<a class="link" href="myisam-storage-engine.html" title="18.2 The MyISAM Storage Engine">
<code class="literal">
MyISAM
</code>
</a>
tables, including
partitioned
<code class="literal">
InnoDB
</code>
and
<code class="literal">
MyISAM
</code>
tables.
</p>
</li>
<li class="listitem">
<p>
For
<code class="literal">
InnoDB
</code>
tables, ICP is used only for
secondary indexes. The goal of ICP is to reduce the number
of full-row reads and thereby reduce I/O operations. For
<code class="literal">
InnoDB
</code>
clustered indexes, the complete
record is already read into the
<code class="literal">
InnoDB
</code>
buffer. Using ICP in this case does not reduce I/O.
</p>
</li>
<li class="listitem">
<p>
ICP is not supported with secondary indexes created on
virtual generated columns.
<code class="literal">
InnoDB
</code>
supports secondary indexes on virtual generated columns.
</p>
</li>
<li class="listitem">
<p>
Conditions that refer to subqueries cannot be pushed down.
</p>
</li>
<li class="listitem">
<p>
Conditions that refer to stored functions cannot be pushed
down. Storage engines cannot invoke stored functions.
</p>
</li>
<li class="listitem">
<p>
Triggered conditions cannot be pushed down. (For
information about triggered conditions, see
<a class="xref" href="subquery-optimization-with-exists.html" title="10.2.2.3 Optimizing Subqueries with the EXISTS Strategy">
Section 10.2.2.3, “Optimizing Subqueries with the EXISTS Strategy”
</a>
.)
</p>
</li>
<li class="listitem">
<p>
Conditions cannot be pushed down to derived tables
containing references to system variables.
</p>
</li>
</ul>
</div>
<p>
To understand how this optimization works, first consider how
an index scan proceeds when Index Condition Pushdown is not
used:
</p>
<div class="orderedlist">
<ol class="orderedlist" type="1">
<li class="listitem">
<p>
Get the next row, first by reading the index tuple, and
then by using the index tuple to locate and read the full
table row.
</p>
</li>
<li class="listitem">
<p>
Test the part of the
<code class="literal">
WHERE
</code>
condition
that applies to this table. Accept or reject the row based
on the test result.
</p>
</li>
</ol>
</div>
<p>
Using Index Condition Pushdown, the scan proceeds like this
instead:
</p>
<div class="orderedlist">
<ol class="orderedlist" type="1">
<li class="listitem">
<p>
Get the next row's index tuple (but not the full
table row).
</p>
</li>
<li class="listitem">
<p>
Test the part of the
<code class="literal">
WHERE
</code>
condition
that applies to this table and can be checked using only
index columns. If the condition is not satisfied, proceed
to the index tuple for the next row.
</p>
</li>
<li class="listitem">
<p>
If the condition is satisfied, use the index tuple to
locate and read the full table row.
</p>
</li>
<li class="listitem">
<p>
Test the remaining part of the
<code class="literal">
WHERE
</code>
condition that applies to this table. Accept or reject the
row based on the test result.
</p>
</li>
</ol>
</div>
<p>
<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 condition
</code>
in the
<code class="literal">
Extra
</code>
column when Index Condition Pushdown
is used. It does not show
<code class="literal">
Using index
</code>
because that does not apply when full table rows must be read.
</p>
<p>
Suppose that a table contains information about people and
their addresses and that the table has an index defined as
<code class="literal">
INDEX (zipcode, lastname, firstname)
</code>
. If we
know a person's
<code class="literal">
zipcode
</code>
value but are
not sure about the last name, we can search like this:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa69054830"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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> people
<span class="token keyword">WHERE</span> zipcode<span class="token operator">=</span><span class="token string">'95054'</span>
<span class="token operator">AND</span> lastname <span class="token operator">LIKE</span> <span class="token string">'%etrunia%'</span>
<span class="token operator">AND</span> address <span class="token operator">LIKE</span> <span class="token string">'%Main Street%'</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
MySQL can use the index to scan through people with
<code class="literal">
zipcode='95054'
</code>
. The second part
(
<code class="literal">
lastname LIKE '%etrunia%'
</code>
) cannot be used
to limit the number of rows that must be scanned, so without
Index Condition Pushdown, this query must retrieve full table
rows for all people who have
<code class="literal">
zipcode='95054'
</code>
.
</p>
<p>
With Index Condition Pushdown, MySQL checks the
<code class="literal">
lastname LIKE '%etrunia%'
</code>
part before
reading the full table row. This avoids reading full rows
corresponding to index tuples that match the
<code class="literal">
zipcode
</code>
condition but not the
<code class="literal">
lastname
</code>
condition.
</p>
<p>
Index Condition Pushdown is enabled by default. It can be
controlled with the
<a class="link" href="server-system-variables.html#sysvar_optimizer_switch">
<code class="literal">
optimizer_switch
</code>
</a>
system
variable by setting the
<a class="link" href="switchable-optimizations.html#optflag_index-condition-pushdown">
<code class="literal">
index_condition_pushdown
</code>
</a>
flag:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa44274381"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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> optimizer_switch <span class="token operator">=</span> <span class="token string">'index_condition_pushdown=off'</span><span class="token punctuation">;</span>
<span class="token keyword">SET</span> optimizer_switch <span class="token operator">=</span> <span class="token string">'index_condition_pushdown=on'</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
See
<a class="xref" href="switchable-optimizations.html" title="10.9.2 Switchable Optimizations">
Section 10.9.2, “Switchable Optimizations”
</a>
.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/sys-diagnostics.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="sys-diagnostics">
</a>
30.4.4.2 The diagnostics() Procedure
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045061655312">
</a>
<a class="indexterm" name="idm46045061653856">
</a>
<p>
Creates a report of the current server status for diagnostic
purposes.
</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>
<p>
Data collected for
<a class="link" href="sys-diagnostics.html" title="30.4.4.2 The diagnostics() Procedure">
<code class="literal">
diagnostics()
</code>
</a>
includes this information:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
Information from the
<a class="link" href="sys-metrics.html" title="30.4.3.21 The metrics View">
<code class="literal">
metrics
</code>
</a>
view (see
<a class="xref" href="sys-metrics.html" title="30.4.3.21 The metrics View">
Section 30.4.3.21, “The metrics View”
</a>
)
</p>
</li>
<li class="listitem">
<p>
Information from other relevant
<code class="literal">
sys
</code>
schema views, such as the one that determines queries in
the 95th percentile
</p>
</li>
<li class="listitem">
<p>
Information from the
<a class="link" href="mysql-cluster-ndbinfo.html" title="25.6.17 ndbinfo: The NDB Cluster Information Database">
<code class="literal">
ndbinfo
</code>
</a>
schema, if the
MySQL server is part of NDB Cluster
</p>
</li>
<li class="listitem">
<p>
Replication status (both source and replica)
</p>
</li>
</ul>
</div>
<p>
Some of the sys schema views are calculated as initial
(optional), overall, and delta values:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
The initial view is the content of the view at the start
of the
<a class="link" href="sys-diagnostics.html" title="30.4.4.2 The diagnostics() Procedure">
<code class="literal">
diagnostics()
</code>
</a>
procedure. This output is the same as the start values
used for the delta view. The initial view is included if
the
<code class="literal">
diagnostics.include_raw
</code>
configuration option is
<code class="literal">
ON
</code>
.
</p>
</li>
<li class="listitem">
<p>
The overall view is the content of the view at the end of
the
<a class="link" href="sys-diagnostics.html" title="30.4.4.2 The diagnostics() Procedure">
<code class="literal">
diagnostics()
</code>
</a>
procedure.
This output is the same as the end values used for the
delta view. The overall view is always included.
</p>
</li>
<li class="listitem">
<p>
The delta view is the difference from the beginning to the
end of procedure execution. The minimum and maximum values
are the minimum and maximum values from the end view,
respectively. They do not necessarily reflect the minimum
and maximum values in the monitored period. Except for the
<a class="link" href="sys-metrics.html" title="30.4.3.21 The metrics View">
<code class="literal">
metrics
</code>
</a>
view, the delta is
calculated only between the first and last outputs.
</p>
</li>
</ul>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h5 class="title">
<a name="sys-diagnostics-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_max_runtime INT UNSIGNED
</code>
: The
maximum data collection time in seconds. Use
<code class="literal">
NULL
</code>
to collect data for the default
of 60 seconds. Otherwise, use a value greater than 0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
in_interval INT UNSIGNED
</code>
: The sleep
time between data collections in seconds. Use
<code class="literal">
NULL
</code>
to sleep for the default of 30
seconds. Otherwise, use a value greater than 0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
in_auto_config ENUM('current', 'medium',
'full')
</code>
: The Performance Schema configuration
to use. Permitted values are:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
<code class="literal">
current
</code>
: Use the current
instrument and consumer settings.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
medium
</code>
: Enable some instruments
and consumers.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
full
</code>
: Enable all instruments and
consumers.
</p>
</li>
</ul>
</div>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
The more instruments and consumers enabled, the more
impact on MySQL server performance. Be careful with
the
<code class="literal">
medium
</code>
setting and especially
the
<code class="literal">
full
</code>
setting, which has a large
performance impact.
</p>
</div>
<p>
Use of the
<code class="literal">
medium
</code>
or
<code class="literal">
full
</code>
setting requires the
<a class="link" href="privileges-provided.html#priv_super">
<code class="literal">
SUPER
</code>
</a>
privilege.
</p>
<p>
If a setting other than
<code class="literal">
current
</code>
is
chosen, the current settings are restored at the end of
the procedure.
</p>
</li>
</ul>
</div>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h5 class="title">
<a name="sys-diagnostics-configuration-options">
</a>
Configuration Options
</h5>
</div>
</div>
</div>
<p>
<a class="link" href="sys-diagnostics.html" title="30.4.4.2 The diagnostics() Procedure">
<code class="literal">
diagnostics()
</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">
debug
</code>
,
<code class="literal">
@sys.debug
</code>
</p>
<p>
If this option is
<code class="literal">
ON
</code>
, produce
debugging output. The default is
<code class="literal">
OFF
</code>
.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
diagnostics.allow_i_s_tables
</code>
,
<code class="literal">
@sys.diagnostics.allow_i_s_tables
</code>
</p>
<p>
If this option is
<code class="literal">
ON
</code>
, the
<a class="link" href="sys-diagnostics.html" title="30.4.4.2 The diagnostics() Procedure">
<code class="literal">
diagnostics()
</code>
</a>
procedure is
permitted to perform table scans on the Information
Schema
<a class="link" href="information-schema-tables-table.html" title="28.3.38 The INFORMATION_SCHEMA TABLES Table">
<code class="literal">
TABLES
</code>
</a>
table. This
can be expensive if there are many tables. The default
is
<code class="literal">
OFF
</code>
.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
diagnostics.include_raw
</code>
,
<code class="literal">
@sys.diagnostics.include_raw
</code>
</p>
<p>
If this option is
<code class="literal">
ON
</code>
, the
<a class="link" href="sys-diagnostics.html" title="30.4.4.2 The diagnostics() Procedure">
<code class="literal">
diagnostics()
</code>
</a>
procedure
output includes the raw output from querying the
<a class="link" href="sys-metrics.html" title="30.4.3.21 The metrics View">
<code class="literal">
metrics
</code>
</a>
view. The default
is
<code class="literal">
OFF
</code>
.
</p>
</li>
<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-diagnostics-example">
</a>
Example
</h5>
</div>
</div>
</div>
<p>
Create a diagnostics report that starts an iteration every
30 seconds and runs for at most 120 seconds using the
current Performance Schema settings:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa41640703"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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><span class="token keyword">diagnostics</span><span class="token punctuation">(</span><span class="token number">120</span><span class="token punctuation">,</span> <span class="token number">30</span><span class="token punctuation">,</span> <span class="token string">'current'</span><span class="token punctuation">)</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
To capture the output from the
<code class="literal">
diagnostics()
</code>
procedure in a file as it
runs, use 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
<code class="literal">
tee
<code class="filename">
filename
</code>
</code>
and
<code class="literal">
notee
</code>
commands (see
<a class="xref" href="mysql-commands.html" title="6.5.1.2 mysql Client Commands">
Section 6.5.1.2, “mysql Client Commands”
</a>
):
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa20667383"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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> tee diag<span class="token punctuation">.</span><span class="token keyword">out</span><span class="token punctuation">;</span>
<span class="token prompt">mysql></span> <span class="token keyword">CALL</span> sys<span class="token punctuation">.</span><span class="token keyword">diagnostics</span><span class="token punctuation">(</span><span class="token number">120</span><span class="token punctuation">,</span> <span class="token number">30</span><span class="token punctuation">,</span> <span class="token string">'current'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt">mysql></span> notee<span class="token punctuation">;</span></code></pre>
</div>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/keyring-component-installation.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="keyring-component-installation">
</a>
8.4.4.2 Keyring Component Installation
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045240984880">
</a>
<a class="indexterm" name="idm46045240983376">
</a>
<a class="indexterm" name="idm46045240981888">
</a>
<a class="indexterm" name="idm46045240980368">
</a>
<p>
Keyring service consumers require that a keyring component or
plugin be installed:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
To use a keyring component, begin with the instructions
here.
</p>
</li>
<li class="listitem">
<p>
To use a keyring plugin instead, begin with
<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>
.
</p>
</li>
<li class="listitem">
<p>
If you intend to use keyring functions in conjunction with
the chosen keyring component or plugin, install the
functions after installing that component or plugin, using
the instructions 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>
</ul>
</div>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
Only one keyring component or plugin should be enabled at a
time. Enabling multiple keyring components or plugins is
unsupported and results may not be as anticipated.
</p>
</div>
<p>
MySQL provides these keyring component choices:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<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.
</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.
</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.
</p>
</li>
</ul>
</div>
<p>
To be usable by the server, the component library file must be
located in the MySQL plugin directory (the directory named by
the
<a class="link" href="server-system-variables.html#sysvar_plugin_dir">
<code class="literal">
plugin_dir
</code>
</a>
system
variable). If necessary, configure the plugin directory location
by setting the value of
<a class="link" href="server-system-variables.html#sysvar_plugin_dir">
<code class="literal">
plugin_dir
</code>
</a>
at server startup.
</p>
<p>
A keyring component or plugin must be loaded early during the
server startup sequence so that other components can access it
as necessary during their own initialization. For example, the
<code class="literal">
InnoDB
</code>
storage engine uses the keyring for
tablespace encryption, so a keyring component or plugin must be
loaded and available prior to
<code class="literal">
InnoDB
</code>
initialization.
</p>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
A keyring component must be enabled on the MySQL server
instance if you need to support secure storage for persisted
system variable values. The keyring plugin does 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>
</div>
<p>
Unlike keyring plugins, keyring components are not loaded using
the
<a class="link" href="server-options.html#option_mysqld_early-plugin-load">
<code class="option">
--early-plugin-load
</code>
</a>
server
option or configured using system variables. Instead, the server
determines which keyring component to load during startup using
a manifest, and the loaded component consults its own
configuration file when it initializes. Therefore, to install a
keyring component, you must:
</p>
<div class="orderedlist">
<ol class="orderedlist" type="1">
<li class="listitem">
<p>
Write a manifest that tells the server which keyring
component to load.
</p>
</li>
<li class="listitem">
<p>
Write a configuration file for that keyring component.
</p>
</li>
</ol>
</div>
<p>
The first step in installing a keyring component is writing a
manifest that indicates which component to load. During startup,
the server reads either a global manifest file, or a global
manifest file paired with a local manifest file:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
The server attempts to read its global manifest file from
the directory where the server is installed.
</p>
</li>
<li class="listitem">
<p>
If the global manifest file indicates use of a local
manifest file, the server attempts to read its local
manifest file from the data directory.
</p>
</li>
<li class="listitem">
<p>
Although global and local manifest files are located in
different directories, the file name is
<code class="filename">
mysqld.my
</code>
in both locations.
</p>
</li>
<li class="listitem">
<p>
It is not an error for a manifest file not to exist. In this
case, the server attempts no component loading associated
with the file.
</p>
</li>
</ul>
</div>
<p>
Local manifest files permit setting up component loading for
multiple instances of the server, such that loading instructions
for each server instance are specific to a given data directory
instance. This enables different MySQL instances to use
different keyring components.
</p>
<p>
Server manifest files have these properties:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
A manifest file must be in valid JSON format.
</p>
</li>
<li class="listitem">
<p>
A manifest file permits these items:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
<code class="literal">
"read_local_manifest"
</code>
: This item is
permitted only in the global manifest file. If the item
is not present, the server uses only the global manifest
file. If the item is present, its value is
<code class="literal">
true
</code>
or
<code class="literal">
false
</code>
,
indicating whether the server should read
component-loading information from the local manifest
file.
</p>
<p>
If the
<code class="literal">
"read_local_manifest"
</code>
item is
present in the global manifest file along with other
items, the server checks the
<code class="literal">
"read_local_manifest"
</code>
item value
first:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: square; ">
<li class="listitem">
<p>
If the value is
<code class="literal">
false
</code>
, the server
processes the other items in the global manifest
file and ignores the local manifest file.
</p>
</li>
<li class="listitem">
<p>
If the value is
<code class="literal">
true
</code>
, the server
ignores the other items in the global manifest file
and attempts to read the local manifest file.
</p>
</li>
</ul>
</div>
</li>
<li class="listitem">
<p>
<code class="literal">
"components"
</code>
: This item indicates
which component to load. The item value is a string that
specifies a valid component URN, such as
<code class="literal">
"file://component_keyring_file"
</code>
. A
component URN begins with
<code class="literal">
file://
</code>
and
indicates the base name of the library file located in
the MySQL plugin directory that implements the
component.
</p>
</li>
</ul>
</div>
</li>
<li class="listitem">
<p>
Server access to a manifest file should be read only. For
example, a
<code class="filename">
mysqld.my
</code>
server manifest
file may be owned by
<code class="literal">
root
</code>
and be
read/write to
<code class="literal">
root
</code>
, but should be read
only to the account used to run the MySQL server. If the
manifest file is found during startup to be read/write to
that account, the server writes a warning to the error log
suggesting that the file be made read only.
</p>
</li>
<li class="listitem">
<p>
The database administrator has the responsibility for
creating any manifest files to be used, and for ensuring
that their access mode and contents are correct. If an error
occurs, server startup fails and the administrator must
correct any issues indicated by diagnostics in the server
error log.
</p>
</li>
</ul>
</div>
<p>
Given the preceding manifest file properties, to configure the
server to load
<code class="literal">
component_keyring_file
</code>
, create
a global manifest file named
<code class="filename">
mysqld.my
</code>
in
the
<a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
<span class="command">
<strong>
mysqld
</strong>
</span>
</a>
installation directory, and
optionally create a local manifest file, also named
<code class="filename">
mysqld.my
</code>
, in the data directory. The
following instructions describe how to load
<code class="literal">
component_keyring_file
</code>
. To load a different
keyring component, substitute its name for
<code class="literal">
component_keyring_file
</code>
.
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
To use a global manifest file only, the file contents look
like this:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-json"><div class="docs-select-all right" id="sa63425400"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-json"><span class="token punctuation">{</span>
<span class="token property">"components"</span><span class="token operator">:</span> <span class="token string">"file://component_keyring_file"</span>
<span class="token punctuation">}</span></code></pre>
</div>
<p>
Create this file in the directory where
<a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
<span class="command">
<strong>
mysqld
</strong>
</span>
</a>
is installed.
</p>
</li>
<li class="listitem">
<p>
Alternatively, to use a global and local manifest file pair,
the global file looks like this:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-json"><div class="docs-select-all right" id="sa38902866"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-json"><span class="token punctuation">{</span>
<span class="token property">"read_local_manifest"</span><span class="token operator">:</span> <span class="token boolean">true</span>
<span class="token punctuation">}</span></code></pre>
</div>
<p>
Create this file in the directory where
<a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
<span class="command">
<strong>
mysqld
</strong>
</span>
</a>
is installed.
</p>
<p>
The local file looks like this:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-json"><div class="docs-select-all right" id="sa59672038"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-json"><span class="token punctuation">{</span>
<span class="token property">"components"</span><span class="token operator">:</span> <span class="token string">"file://component_keyring_file"</span>
<span class="token punctuation">}</span></code></pre>
</div>
<p>
Create this file in the data directory.
</p>
</li>
</ul>
</div>
<p>
With the manifest in place, proceed to configuring the keyring
component. To do this, check the notes for your chosen keyring
component for configuration instructions specific to that
component:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<code class="literal">
component_keyring_file
</code>
:
<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>
:
<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>
:
<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>
After performing any component-specific configuration, start the
server. Verify component installation by examining 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:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa98768605"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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>keyring_component_status<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> STATUS_KEY <span class="token punctuation">|</span> STATUS_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 class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><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> Component_name <span class="token punctuation">|</span> component_keyring_file <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> Author <span class="token punctuation">|</span> Oracle Corporation <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> License <span class="token punctuation">|</span> GPL <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> Implementation_name <span class="token punctuation">|</span> component_keyring_file <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> Version <span class="token punctuation">|</span> 1.0 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> Component_status <span class="token punctuation">|</span> Active <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> Data_file <span class="token punctuation">|</span> /usr/local/mysql/keyring/component_keyring_file <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> Read_only <span class="token punctuation">|</span> No <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></code></pre>
</div>
<p>
A
<code class="literal">
Component_status
</code>
value of
<code class="literal">
Active
</code>
indicates that the component
initialized successfully.
</p>
<p>
If the component cannot be loaded, server startup fails. Check
the server error log for diagnostic messages. If the component
loads but fails to initialize due to configuration problems, the
server starts but the
<code class="literal">
Component_status
</code>
value
is
<code class="literal">
Disabled
</code>
. Check the server error log,
correct the configuration issues, and use the
<a class="link" href="alter-instance.html#alter-instance-reload-keyring">
<code class="literal">
ALTER INSTANCE RELOAD KEYRING
</code>
</a>
statement to reload the configuration.
</p>
<p>
Keyring components should be loaded only by using a manifest
file, not by using the
<a class="link" href="install-component.html" title="15.7.4.3 INSTALL COMPONENT Statement">
<code class="literal">
INSTALL
COMPONENT
</code>
</a>
statement. Keyring components loaded using
that statement may be available too late in the server startup
sequence for certain components that use the keyring, such as
<code class="literal">
InnoDB
</code>
, because they are registered in the
<code class="literal">
mysql.component
</code>
system table and loaded
automatically for subsequent server restarts. But
<code class="literal">
mysql.component
</code>
is an
<code class="literal">
InnoDB
</code>
table, so any components named in it
can be loaded during startup only after
<code class="literal">
InnoDB
</code>
initialization.
</p>
<p>
If no keyring component or plugin is available when a component
tries to access the keyring service, the service cannot be used
by that component. As a result, the component may fail to
initialize or may initialize with limited functionality. For
example, if
<code class="literal">
InnoDB
</code>
finds that there are
encrypted tablespaces when it initializes, it attempts to access
the keyring. If the keyring is unavailable,
<code class="literal">
InnoDB
</code>
can access only unencrypted
tablespaces.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/group-replication-bootstrap.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="group-replication-bootstrap">
</a>
20.2.1.5 Bootstrapping the Group
</h4>
</div>
</div>
</div>
<p>
The process of starting a group for the first time is called
bootstrapping. You use the
<a class="link" href="group-replication-system-variables.html#sysvar_group_replication_bootstrap_group">
<code class="literal">
group_replication_bootstrap_group
</code>
</a>
system variable to bootstrap a group. The bootstrap should only
be done by a single server, the one that starts the group and
only once. This is why the value of the
<a class="link" href="group-replication-system-variables.html#sysvar_group_replication_bootstrap_group">
<code class="literal">
group_replication_bootstrap_group
</code>
</a>
option was not stored in the instance's option file. If it is
saved in the option file, upon restart the server automatically
bootstraps a second group with the same name. This would result
in two distinct groups with the same name. The same reasoning
applies to stopping and restarting the plugin with this option
set to
<code class="literal">
ON
</code>
. Therefore to safely bootstrap the
group, connect to s1 and issue the following statements:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa73580501"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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_bootstrap_group<span class="token operator">=</span><span class="token keyword">ON</span><span class="token punctuation">;</span>
<span class="token prompt">mysql></span> <span class="token keyword">START</span> <span class="token keyword">GROUP_REPLICATION</span><span class="token punctuation">;</span>
<span class="token prompt">mysql></span> <span class="token keyword">SET</span> <span class="token keyword">GLOBAL</span> group_replication_bootstrap_group<span class="token operator">=</span><span class="token keyword">OFF</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
Or if you are providing user credentials for distributed
recovery in the
<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, issue the following
statements:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa95378368"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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_bootstrap_group<span class="token operator">=</span><span class="token keyword">ON</span><span class="token punctuation">;</span>
<span class="token prompt">mysql></span> <span class="token keyword">START</span> <span class="token keyword">GROUP_REPLICATION</span> <span class="token keyword">USER</span><span class="token operator">=</span><span class="token string">'<em class="replaceable">rpl_user</em>'</span><span class="token punctuation">,</span> <span class="token keyword">PASSWORD</span><span class="token operator">=</span><span class="token string">'<em class="replaceable">password</em>'</span><span class="token punctuation">;</span>
<span class="token prompt">mysql></span> <span class="token keyword">SET</span> <span class="token keyword">GLOBAL</span> group_replication_bootstrap_group<span class="token operator">=</span><span class="token keyword">OFF</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
Once the
<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 returns, the group has been started. You can check
that the group is now created and that there is one member in
it:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa55838869"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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 class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><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> CHANNEL_NAME <span class="token punctuation">|</span> MEMBER_ID <span class="token punctuation">|</span> MEMBER_HOST <span class="token punctuation">|</span> MEMBER_PORT <span class="token punctuation">|</span> MEMBER_STATE <span class="token punctuation">|</span> MEMBER_ROLE <span class="token punctuation">|</span> MEMBER_VERSION <span class="token punctuation">|</span> MEMBER_COMMUNICATION_STACK <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 class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><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> group_replication_applier <span class="token punctuation">|</span> ce9be252<span class="token punctuation">-</span>2b71<span class="token punctuation">-</span>11e6<span class="token punctuation">-</span>b8f4<span class="token punctuation">-</span>00212844f856 <span class="token punctuation">|</span> s1 <span class="token punctuation">|</span> 3306 <span class="token punctuation">|</span> ONLINE <span class="token punctuation">|</span> <span class="token punctuation">|</span> <span class="token punctuation">|</span> XCom <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 class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><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 (0.0108 sec)</span></code></pre>
</div>
<p>
The information in this table confirms that there is a member in
the group with the unique identifier
<code class="literal">
ce9be252-2b71-11e6-b8f4-00212844f856
</code>
, that it
is
<code class="literal">
ONLINE
</code>
and is at
<code class="literal">
s1
</code>
listening for client connections on port
<code class="literal">
3306
</code>
.
</p>
<p>
For the purpose of demonstrating that the server is indeed in a
group and that it is able to handle load, create a table and add
some content to it.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa79300102"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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> test<span class="token punctuation">;</span>
<span class="token prompt">mysql></span> <span class="token keyword">USE</span> test<span class="token punctuation">;</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>c1 <span class="token datatype">INT</span> <span class="token keyword">PRIMARY</span> <span class="token keyword">KEY</span><span class="token punctuation">,</span> c2 <span class="token datatype">TEXT</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 prompt">mysql></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">'Luis'</span><span class="token punctuation">)</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
Check the content of table
<code class="literal">
t1
</code>
and the binary
log.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa81384714"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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> t1<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> c1 <span class="token punctuation">|</span> c2 <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> 1 <span class="token punctuation">|</span> Luis <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">SHOW</span> <span class="token keyword">BINLOG</span> <span class="token keyword">EVENTS</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 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<span class="token output"><span class="token punctuation">|</span> Log_name <span class="token punctuation">|</span> Pos <span class="token punctuation">|</span> Event_type <span class="token punctuation">|</span> Server_id <span class="token punctuation">|</span> End_log_pos <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 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class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><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> binlog.000001 <span class="token punctuation">|</span> 4 <span class="token punctuation">|</span> Format_desc <span class="token punctuation">|</span> 1 <span class="token punctuation">|</span> 123 <span class="token punctuation">|</span> Server ver: 8.4.3<span class="token punctuation">-</span>log, Binlog ver: 4 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> binlog.000001 <span class="token punctuation">|</span> 123 <span class="token punctuation">|</span> Previous_gtids <span class="token punctuation">|</span> 1 <span class="token punctuation">|</span> 150 <span class="token punctuation">|</span> <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> binlog.000001 <span class="token punctuation">|</span> 150 <span class="token punctuation">|</span> Gtid <span class="token punctuation">|</span> 1 <span class="token punctuation">|</span> 211 <span class="token punctuation">|</span> SET @@SESSION.GTID_NEXT= 'aaaaaaaa<span class="token punctuation">-</span>aaaa<span class="token punctuation">-</span>aaaa<span class="token punctuation">-</span>aaaa<span class="token punctuation">-</span>aaaaaaaaaaaa:1' <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> binlog.000001 <span class="token punctuation">|</span> 211 <span class="token punctuation">|</span> Query <span class="token punctuation">|</span> 1 <span class="token punctuation">|</span> 270 <span class="token punctuation">|</span> BEGIN <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> binlog.000001 <span class="token punctuation">|</span> 270 <span class="token punctuation">|</span> View_change <span class="token punctuation">|</span> 1 <span class="token punctuation">|</span> 369 <span class="token punctuation">|</span> view_id=14724817264259180:1 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> binlog.000001 <span class="token punctuation">|</span> 369 <span class="token punctuation">|</span> Query <span class="token punctuation">|</span> 1 <span class="token punctuation">|</span> 434 <span class="token punctuation">|</span> COMMIT <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> binlog.000001 <span class="token punctuation">|</span> 434 <span class="token punctuation">|</span> Gtid <span class="token punctuation">|</span> 1 <span class="token punctuation">|</span> 495 <span class="token punctuation">|</span> SET @@SESSION.GTID_NEXT= 'aaaaaaaa<span class="token punctuation">-</span>aaaa<span class="token punctuation">-</span>aaaa<span class="token punctuation">-</span>aaaa<span class="token punctuation">-</span>aaaaaaaaaaaa:2' <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> binlog.000001 <span class="token punctuation">|</span> 495 <span class="token punctuation">|</span> Query <span class="token punctuation">|</span> 1 <span class="token punctuation">|</span> 585 <span class="token punctuation">|</span> CREATE DATABASE test <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> binlog.000001 <span class="token punctuation">|</span> 585 <span class="token punctuation">|</span> Gtid <span class="token punctuation">|</span> 1 <span class="token punctuation">|</span> 646 <span class="token punctuation">|</span> SET @@SESSION.GTID_NEXT= 'aaaaaaaa<span class="token punctuation">-</span>aaaa<span class="token punctuation">-</span>aaaa<span class="token punctuation">-</span>aaaa<span class="token punctuation">-</span>aaaaaaaaaaaa:3' <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> binlog.000001 <span class="token punctuation">|</span> 646 <span class="token punctuation">|</span> Query <span class="token punctuation">|</span> 1 <span class="token punctuation">|</span> 770 <span class="token punctuation">|</span> use `test`; CREATE TABLE t1 (c1 INT PRIMARY KEY, c2 TEXT NOT NULL) <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> binlog.000001 <span class="token punctuation">|</span> 770 <span class="token punctuation">|</span> Gtid <span class="token punctuation">|</span> 1 <span class="token punctuation">|</span> 831 <span class="token punctuation">|</span> SET @@SESSION.GTID_NEXT= 'aaaaaaaa<span class="token punctuation">-</span>aaaa<span class="token punctuation">-</span>aaaa<span class="token punctuation">-</span>aaaa<span class="token punctuation">-</span>aaaaaaaaaaaa:4' <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> binlog.000001 <span class="token punctuation">|</span> 831 <span class="token punctuation">|</span> Query <span class="token punctuation">|</span> 1 <span class="token punctuation">|</span> 899 <span class="token punctuation">|</span> BEGIN <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> binlog.000001 <span class="token punctuation">|</span> 899 <span class="token punctuation">|</span> Table_map <span class="token punctuation">|</span> 1 <span class="token punctuation">|</span> 942 <span class="token punctuation">|</span> table_id: 108 (test.t1) <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> binlog.000001 <span class="token punctuation">|</span> 942 <span class="token punctuation">|</span> Write_rows <span class="token punctuation">|</span> 1 <span class="token punctuation">|</span> 984 <span class="token punctuation">|</span> table_id: 108 flags: STMT_END_F <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> binlog.000001 <span class="token punctuation">|</span> 984 <span class="token punctuation">|</span> Xid <span class="token punctuation">|</span> 1 <span class="token punctuation">|</span> 1011 <span class="token punctuation">|</span> COMMIT /* xid=38 */ <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 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class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="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>
As seen above, the database and the table objects were created
and their corresponding DDL statements were written to the
binary log. Also, the data was inserted into the table and
written to the binary log, so it can be used for distributed
recovery by state transfer from a donor's binary log.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/performance-schema-hosts-table.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="performance-schema-hosts-table">
</a>
29.12.8.2 The hosts Table
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045072068768">
</a>
<a class="indexterm" name="idm46045072067280">
</a>
<p>
The
<a class="link" href="performance-schema-hosts-table.html" title="29.12.8.2 The hosts Table">
<code class="literal">
hosts
</code>
</a>
table contains a row
for each host from which clients have connected to the MySQL
server. For each host name, the table counts the current and
total number of connections. The table size is autosized at
server startup. To set the table size explicitly, set the
<a class="link" href="performance-schema-system-variables.html#sysvar_performance_schema_hosts_size">
<code class="literal">
performance_schema_hosts_size
</code>
</a>
system variable at server startup. To disable host statistics,
set this variable to 0.
</p>
<p>
The
<a class="link" href="performance-schema-hosts-table.html" title="29.12.8.2 The hosts Table">
<code class="literal">
hosts
</code>
</a>
table has the following
columns. For a description of how the Performance Schema
maintains rows in this table, including the effect of
<a class="link" href="truncate-table.html" title="15.1.37 TRUNCATE TABLE Statement">
<code class="literal">
TRUNCATE TABLE
</code>
</a>
, see
<a class="xref" href="performance-schema-connection-tables.html" title="29.12.8 Performance Schema Connection Tables">
Section 29.12.8, “Performance Schema Connection Tables”
</a>
.
</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. This is
<code class="literal">
NULL
</code>
for an internal thread, or for a
user session that failed to authenticate.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
CURRENT_CONNECTIONS
</code>
</p>
<p>
The current number of connections for the host.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
TOTAL_CONNECTIONS
</code>
</p>
<p>
The total number of connections for the host.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
MAX_SESSION_CONTROLLED_MEMORY
</code>
</p>
<p>
Reports the maximum amount of controlled memory used by a
session belonging to the host.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
MAX_SESSION_TOTAL_MEMORY
</code>
</p>
<p>
Reports the maximum amount of memory used by a session
belonging to the host.
</p>
</li>
</ul>
</div>
<p>
The
<a class="link" href="performance-schema-hosts-table.html" title="29.12.8.2 The hosts Table">
<code class="literal">
hosts
</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">
HOST
</code>
)
</p>
</li>
</ul>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/information-schema-innodb-ft-being-deleted-table.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="information-schema-innodb-ft-being-deleted-table">
</a>
28.4.14 The INFORMATION_SCHEMA INNODB_FT_BEING_DELETED Table
</h3>
</div>
</div>
</div>
<a class="indexterm" name="idm46045076972128">
</a>
<p>
The
<a class="link" href="information-schema-innodb-ft-being-deleted-table.html" title="28.4.14 The INFORMATION_SCHEMA INNODB_FT_BEING_DELETED Table">
<code class="literal">
INNODB_FT_BEING_DELETED
</code>
</a>
table
provides a snapshot of the
<a class="link" href="information-schema-innodb-ft-deleted-table.html" title="28.4.17 The INFORMATION_SCHEMA INNODB_FT_DELETED Table">
<code class="literal">
INNODB_FT_DELETED
</code>
</a>
table; it is used
only during an
<a class="link" href="optimize-table.html" title="15.7.3.4 OPTIMIZE TABLE Statement">
<code class="literal">
OPTIMIZE TABLE
</code>
</a>
maintenance operation. When
<a class="link" href="optimize-table.html" title="15.7.3.4 OPTIMIZE TABLE Statement">
<code class="literal">
OPTIMIZE
TABLE
</code>
</a>
is run, the
<a class="link" href="information-schema-innodb-ft-being-deleted-table.html" title="28.4.14 The INFORMATION_SCHEMA INNODB_FT_BEING_DELETED Table">
<code class="literal">
INNODB_FT_BEING_DELETED
</code>
</a>
table is
emptied, and
<code class="literal">
DOC_ID
</code>
values are removed from the
<a class="link" href="information-schema-innodb-ft-deleted-table.html" title="28.4.17 The INFORMATION_SCHEMA INNODB_FT_DELETED Table">
<code class="literal">
INNODB_FT_DELETED
</code>
</a>
table. Because the
contents of
<a class="link" href="information-schema-innodb-ft-being-deleted-table.html" title="28.4.14 The INFORMATION_SCHEMA INNODB_FT_BEING_DELETED Table">
<code class="literal">
INNODB_FT_BEING_DELETED
</code>
</a>
typically have a short lifetime, this table has limited utility
for monitoring or debugging. For information about running
<a class="link" href="optimize-table.html" title="15.7.3.4 OPTIMIZE TABLE Statement">
<code class="literal">
OPTIMIZE TABLE
</code>
</a>
on tables with
<code class="literal">
FULLTEXT
</code>
indexes, see
<a class="xref" href="fulltext-fine-tuning.html" title="14.9.6 Fine-Tuning MySQL Full-Text Search">
Section 14.9.6, “Fine-Tuning MySQL Full-Text Search”
</a>
.
</p>
<p>
This table is empty initially. Before querying it, set the value
of the
<a class="link" href="innodb-parameters.html#sysvar_innodb_ft_aux_table">
<code class="literal">
innodb_ft_aux_table
</code>
</a>
system
variable to the name (including the database name) of the table
that contains the
<code class="literal">
FULLTEXT
</code>
index (for example,
<code class="literal">
test/articles
</code>
). The output appears similar to
the example provided for the
<a class="link" href="information-schema-innodb-ft-deleted-table.html" title="28.4.17 The INFORMATION_SCHEMA INNODB_FT_DELETED Table">
<code class="literal">
INNODB_FT_DELETED
</code>
</a>
table.
</p>
<p>
For related usage information and examples, see
<a class="xref" href="innodb-information-schema-fulltext_index-tables.html" title="17.15.4 InnoDB INFORMATION_SCHEMA FULLTEXT Index Tables">
Section 17.15.4, “InnoDB INFORMATION_SCHEMA FULLTEXT Index Tables”
</a>
.
</p>
<p>
The
<a class="link" href="information-schema-innodb-ft-being-deleted-table.html" title="28.4.14 The INFORMATION_SCHEMA INNODB_FT_BEING_DELETED Table">
<code class="literal">
INNODB_FT_BEING_DELETED
</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">
DOC_ID
</code>
</p>
<p>
The document ID of the row that is in the process of being
deleted. This value might reflect the value of an ID column
that you defined for the underlying table, or it can be a
sequence value generated by
<code class="literal">
InnoDB
</code>
when the
table contains no suitable column. This value is used when you
perform text searches, to skip rows in the
<a class="link" href="information-schema-innodb-ft-index-table-table.html" title="28.4.19 The INFORMATION_SCHEMA INNODB_FT_INDEX_TABLE Table">
<code class="literal">
INNODB_FT_INDEX_TABLE
</code>
</a>
table
before data for deleted rows is physically removed from the
<code class="literal">
FULLTEXT
</code>
index by an
<a class="link" href="optimize-table.html" title="15.7.3.4 OPTIMIZE TABLE Statement">
<code class="literal">
OPTIMIZE TABLE
</code>
</a>
statement. For
more information, see
<a class="xref" href="fulltext-fine-tuning.html#fulltext-optimize" title="Optimizing InnoDB Full-Text Indexes">
Optimizing InnoDB Full-Text Indexes
</a>
.
</p>
</li>
</ul>
</div>
<h4>
<a name="idm46045076942752">
</a>
Notes
</h4>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
Use the
<code class="literal">
INFORMATION_SCHEMA
</code>
<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 or the
<a class="link" href="show-columns.html" title="15.7.7.6 SHOW COLUMNS Statement">
<code class="literal">
SHOW COLUMNS
</code>
</a>
statement to view
additional information about the columns of this table,
including data types and default values.
</p>
</li>
<li class="listitem">
<p>
You must have the
<a class="link" href="privileges-provided.html#priv_process">
<code class="literal">
PROCESS
</code>
</a>
privilege to query this table.
</p>
</li>
<li class="listitem">
<p>
For more information about
<code class="literal">
InnoDB
</code>
<code class="literal">
FULLTEXT
</code>
search, see
<a class="xref" href="innodb-fulltext-index.html" title="17.6.2.4 InnoDB Full-Text Indexes">
Section 17.6.2.4, “InnoDB Full-Text Indexes”
</a>
, and
<a class="xref" href="fulltext-search.html" title="14.9 Full-Text Search Functions">
Section 14.9, “Full-Text Search Functions”
</a>
.
</p>
</li>
</ul>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/mysql-cluster-shm-definition.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="mysql-cluster-shm-definition">
</a>
25.4.3.12 NDB Cluster Shared-Memory Connections
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045109104560">
</a>
<a class="indexterm" name="idm46045109103072">
</a>
<a class="indexterm" name="idm46045109101568">
</a>
<a class="indexterm" name="idm46045109100080">
</a>
<p>
Communications between NDB cluster nodes are normally handled
using TCP/IP. The shared memory (SHM) transporter is
distinguished by the fact that signals are transmitted by
writing in memory rather than on a socket. The shared-memory
transporter (SHM) can improve performance by negating up to 20%
of the overhead required by a TCP connection when running an API
node (usually an SQL node) and a data node together on the same
host. You can enable a shared memory connection in either of the
two ways listed here:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
By setting the
<a class="link" href="mysql-cluster-ndbd-definition.html#ndbparam-ndbd-useshm">
<code class="literal">
UseShm
</code>
</a>
data node
configuration parameter to
<code class="literal">
1
</code>
, and setting
<a class="link" href="mysql-cluster-ndbd-definition.html#ndbparam-ndbd-hostname">
<code class="literal">
HostName
</code>
</a>
for the
data node and
<a class="link" href="mysql-cluster-api-definition.html#ndbparam-api-hostname">
<code class="literal">
HostName
</code>
</a>
for the API
node to the same value.
</p>
</li>
<li class="listitem">
<p>
By using
<code class="literal">
[shm]
</code>
sections in the cluster
configuration file, each containing settings for
<a class="link" href="mysql-cluster-shm-definition.html#ndbparam-shm-nodeid1">
<code class="literal">
NodeId1
</code>
</a>
and
<a class="link" href="mysql-cluster-shm-definition.html#ndbparam-shm-nodeid2">
<code class="literal">
NodeId2
</code>
</a>
. This method
is described in more detail later in this section.
</p>
</li>
</ul>
</div>
<p>
Suppose a cluster is running a data node which has node ID 1 and
an SQL node having node ID 51 on the same host computer at
10.0.0.1. To enable an SHM connection between these two nodes,
all that is necessary is to insure that the following entries
are included in the cluster configuration file:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-ini"><div class="docs-select-all right" id="sa85965374"><div class="copy-help left">Press ⌘+C to 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">[ndbd]</span>
<span class="token constant">NodeId</span><span class="token attr-value"><span class="token punctuation">=</span>1</span>
<span class="token constant">HostName</span><span class="token attr-value"><span class="token punctuation">=</span>10.0.0.1</span>
<span class="token constant">UseShm</span><span class="token attr-value"><span class="token punctuation">=</span>1</span>
<span class="token selector">[mysqld]</span>
<span class="token constant">NodeId</span><span class="token attr-value"><span class="token punctuation">=</span>51</span>
<span class="token constant">HostName</span><span class="token attr-value"><span class="token punctuation">=</span>10.0.0.1</span></code></pre>
</div>
<div class="important" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Important
</div>
<p>
The two entries just shown are in addition to any other
entries and parameter settings needed by the cluster. A more
complete example is shown later in this section.
</p>
</div>
<p>
Before starting data nodes that use SHM connections, it is also
necessary to make sure that the operating system on each
computer hosting such a data node has sufficient memory
allocated to shared memory segments. See the documentation for
your operating platform for information regarding this. In
setups where multiple hosts are each running a data node and an
API node, it is possible to enable shared memory on all such
hosts by setting
<code class="literal">
UseShm
</code>
in the
<code class="literal">
[ndbd
default]
</code>
section of the configuration file. This is
shown in the example later in this section.
</p>
<p>
While not strictly required, tuning for all SHM connections in
the cluster can be done by setting one or more of the following
parameters in the
<code class="literal">
[shm default]
</code>
section of
the cluster configuration (
<code class="filename">
config.ini
</code>
)
file:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<a class="link" href="mysql-cluster-shm-definition.html#ndbparam-shm-shmsize">
<code class="literal">
ShmSize
</code>
</a>
: Shared
memory size
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="mysql-cluster-shm-definition.html#ndbparam-shm-shmspintime">
<code class="literal">
ShmSpinTime
</code>
</a>
: Time in
µs to spin before sleeping
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="mysql-cluster-shm-definition.html#ndbparam-shm-sendbuffermemory">
<code class="literal">
SendBufferMemory
</code>
</a>
:
Size of buffer for signals sent from this node, in bytes.
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="mysql-cluster-shm-definition.html#ndbparam-shm-sendsignalid">
<code class="literal">
SendSignalId
</code>
</a>
:
Indicates that a signal ID is included in each signal sent
through the transporter.
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="mysql-cluster-shm-definition.html#ndbparam-shm-checksum">
<code class="literal">
Checksum
</code>
</a>
: Indicates
that a checksum is included in each signal sent through the
transporter.
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="mysql-cluster-shm-definition.html#ndbparam-shm-presendchecksum">
<code class="literal">
PreSendChecksum
</code>
</a>
:
Checks of the checksum are made prior to sending the signal;
Checksum must also be enabled for this to work
</p>
</li>
</ul>
</div>
<p>
This example shows a simple setup with SHM connections defined
on multiple hosts, in an NDB Cluster using 3 computers listed
here by host name, hosting the node types shown:
</p>
<div class="orderedlist">
<ol class="orderedlist" type="1">
<li class="listitem">
<p>
<code class="literal">
10.0.0.0
</code>
: The management server
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
10.0.0.1
</code>
: A data node and an SQL node
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
10.0.0.2
</code>
: A data node and an SQL node
</p>
</li>
</ol>
</div>
<p>
In this scenario, each data node communicates with both the
management server and the other data node using TCP
transporters; each SQL node uses a shared memory transporter to
communicate with the data nodes that is local to it, and a TCP
transporter to communicate with the remote data node. A basic
configuration reflecting this setup is enabled by the config.ini
file whose contents are shown here:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-ini"><div class="docs-select-all right" id="sa7249325"><div class="copy-help left">Press ⌘+C to 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">[ndbd default]</span>
<span class="token constant">DataDir</span><span class="token attr-value"><span class="token punctuation">=</span><em class="replaceable">/path/to/datadir</em></span>
<span class="token constant">UseShm</span><span class="token attr-value"><span class="token punctuation">=</span>1</span>
<span class="token selector">[shm default]</span>
<span class="token constant">ShmSize</span><span class="token attr-value"><span class="token punctuation">=</span>8M</span>
<span class="token constant">ShmSpintime</span><span class="token attr-value"><span class="token punctuation">=</span>200</span>
<span class="token constant">SendBufferMemory</span><span class="token attr-value"><span class="token punctuation">=</span>4M</span>
<span class="token selector">[tcp default]</span>
<span class="token constant">SendBufferMemory</span><span class="token attr-value"><span class="token punctuation">=</span>8M</span>
<span class="token selector">[ndb_mgmd]</span>
<span class="token constant">NodeId</span><span class="token attr-value"><span class="token punctuation">=</span>49</span>
<span class="token constant">Hostname</span><span class="token attr-value"><span class="token punctuation">=</span>10.0.0.0</span>
<span class="token constant">DataDir</span><span class="token attr-value"><span class="token punctuation">=</span><em class="replaceable">/path/to/datadir</em></span>
<span class="token selector">[ndbd]</span>
<span class="token constant">NodeId</span><span class="token attr-value"><span class="token punctuation">=</span>1</span>
<span class="token constant">Hostname</span><span class="token attr-value"><span class="token punctuation">=</span>10.0.0.1</span>
<span class="token constant">DataDir</span><span class="token attr-value"><span class="token punctuation">=</span><em class="replaceable">/path/to/datadir</em></span>
<span class="token selector">[ndbd]</span>
<span class="token constant">NodeId</span><span class="token attr-value"><span class="token punctuation">=</span>2</span>
<span class="token constant">Hostname</span><span class="token attr-value"><span class="token punctuation">=</span>10.0.0.2</span>
<span class="token constant">DataDir</span><span class="token attr-value"><span class="token punctuation">=</span><em class="replaceable">/path/to/datadir</em></span>
<span class="token selector">[mysqld]</span>
<span class="token constant">NodeId</span><span class="token attr-value"><span class="token punctuation">=</span>51</span>
<span class="token constant">Hostname</span><span class="token attr-value"><span class="token punctuation">=</span>10.0.0.1</span>
<span class="token selector">[mysqld]</span>
<span class="token constant">NodeId</span><span class="token attr-value"><span class="token punctuation">=</span>52</span>
<span class="token constant">Hostname</span><span class="token attr-value"><span class="token punctuation">=</span>10.0.0.2</span>
<span class="token selector">[api]</span>
<span class="token selector">[api]</span></code></pre>
</div>
<p>
Parameters affecting all shared memory transporters are set in
the
<code class="literal">
[shm default]
</code>
section; these can be
overridden on a per-connection basis in one or more
<code class="literal">
[shm]
</code>
sections. Each such section must be
associated with a given SHM connection using
<a class="link" href="mysql-cluster-shm-definition.html#ndbparam-shm-nodeid1">
<code class="literal">
NodeId1
</code>
</a>
and
<a class="link" href="mysql-cluster-shm-definition.html#ndbparam-shm-nodeid2">
<code class="literal">
NodeId2
</code>
</a>
; the values
required for these parameters are the node IDs of the two nodes
connected by the transporter. You can also identify the nodes by
host name using
<a class="link" href="mysql-cluster-shm-definition.html#ndbparam-shm-hostname1">
<code class="literal">
HostName1
</code>
</a>
and
<a class="link" href="mysql-cluster-shm-definition.html#ndbparam-shm-hostname2">
<code class="literal">
HostName2
</code>
</a>
, but these
parameters are not required.
</p>
<p>
The API nodes for which no host names are set use the TCP
transporter to communicate with data nodes independent of the
hosts on which they are started; the parameters and values set
in the
<code class="literal">
[tcp default]
</code>
section of the
configuration file apply to all TCP transporters in the cluster.
</p>
<p>
For optimum performance, you can define a spin time for the SHM
transporter (
<a class="link" href="mysql-cluster-shm-definition.html#ndbparam-shm-shmspintime">
<code class="literal">
ShmSpinTime
</code>
</a>
parameter); this affects both the data node receiver thread and
the poll owner (receive thread or user thread) in
<code class="literal">
NDB
</code>
.
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<a name="ndbparam-shm-checksum">
</a>
<code class="literal">
Checksum
</code>
</p>
<a class="indexterm" name="idm46045109044320">
</a>
<div class="informaltable">
<a name="checksum-shm-table">
</a>
<table frame="box" rules="all" summary="Checksum shared memory configuration parameter type and value information" width="35%">
<colgroup>
<col style="width: 50%"/>
<col style="width: 50%"/>
</colgroup>
<tbody>
<tr>
<th>
Version (or later)
</th>
<td>
NDB 8.4.0
</td>
</tr>
<tr>
<th>
Type or units
</th>
<td>
boolean
</td>
</tr>
<tr>
<th>
Default
</th>
<td>
true
</td>
</tr>
<tr>
<th>
Range
</th>
<td>
true, false
</td>
</tr>
<tr>
<th>
Restart Type
</th>
<td>
<p>
<span class="bold">
<strong>
Node Restart:
</strong>
</span>
Requires a
<a class="link" href="mysql-cluster-rolling-restart.html" title="25.6.5 Performing a Rolling Restart of an NDB Cluster">
rolling
restart
</a>
of the cluster. (NDB 8.4.0)
</p>
</td>
</tr>
</tbody>
</table>
</div>
<p>
This parameter is a boolean
(
<code class="literal">
Y
</code>
/
<code class="literal">
N
</code>
) parameter which
is disabled by default. When it is enabled, checksums for
all messages are calculated before being placed in the send
buffer.
</p>
<p>
This feature prevents messages from being corrupted while
waiting in the send buffer. It also serves as a check
against data being corrupted during transport.
</p>
</li>
<li class="listitem">
<p>
<a name="ndbparam-shm-group">
</a>
<code class="literal">
Group
</code>
</p>
<a class="indexterm" name="idm46045109022480">
</a>
<div class="informaltable">
<a name="group-shm-table">
</a>
<table frame="box" rules="all" summary="Group shared memory configuration parameter type and value information" width="35%">
<colgroup>
<col style="width: 50%"/>
<col style="width: 50%"/>
</colgroup>
<tbody>
<tr>
<th>
Version (or later)
</th>
<td>
NDB 8.4.0
</td>
</tr>
<tr>
<th>
Type or units
</th>
<td>
unsigned
</td>
</tr>
<tr>
<th>
Default
</th>
<td>
35
</td>
</tr>
<tr>
<th>
Range
</th>
<td>
0 - 200
</td>
</tr>
<tr>
<th>
Restart Type
</th>
<td>
<p>
<span class="bold">
<strong>
Node Restart:
</strong>
</span>
Requires a
<a class="link" href="mysql-cluster-rolling-restart.html" title="25.6.5 Performing a Rolling Restart of an NDB Cluster">
rolling
restart
</a>
of the cluster. (NDB 8.4.0)
</p>
</td>
</tr>
</tbody>
</table>
</div>
<p>
Determines the group proximity; a smaller value is
interpreted as being closer. The default value is sufficient
for most conditions.
</p>
</li>
<li class="listitem">
<p>
<a name="ndbparam-shm-hostname1">
</a>
<code class="literal">
HostName1
</code>
</p>
<a class="indexterm" name="idm46045109002512">
</a>
<div class="informaltable">
<a name="hostname1-shm-table">
</a>
<table frame="box" rules="all" summary="HostName1 shared memory configuration parameter type and value information" width="35%">
<colgroup>
<col style="width: 50%"/>
<col style="width: 50%"/>
</colgroup>
<tbody>
<tr>
<th>
Version (or later)
</th>
<td>
NDB 8.4.0
</td>
</tr>
<tr>
<th>
Type or units
</th>
<td>
name or IP address
</td>
</tr>
<tr>
<th>
Default
</th>
<td>
[...]
</td>
</tr>
<tr>
<th>
Range
</th>
<td>
...
</td>
</tr>
<tr>
<th>
Restart Type
</th>
<td>
<p>
<span class="bold">
<strong>
Node Restart:
</strong>
</span>
Requires a
<a class="link" href="mysql-cluster-rolling-restart.html" title="25.6.5 Performing a Rolling Restart of an NDB Cluster">
rolling
restart
</a>
of the cluster. (NDB 8.4.0)
</p>
</td>
</tr>
</tbody>
</table>
</div>
<p>
The
<code class="literal">
HostName1
</code>
and
<a class="link" href="mysql-cluster-shm-definition.html#ndbparam-shm-hostname2">
<code class="literal">
HostName2
</code>
</a>
parameters
can be used to specify specific network interfaces to be
used for a given SHM connection between two nodes. The
values used for these parameters can be host names or IP
addresses.
</p>
</li>
<li class="listitem">
<p>
<a name="ndbparam-shm-hostname2">
</a>
<code class="literal">
HostName2
</code>
</p>
<a class="indexterm" name="idm46045108980496">
</a>
<div class="informaltable">
<a name="hostname2-shm-table">
</a>
<table frame="box" rules="all" summary="HostName2 shared memory configuration parameter type and value information" width="35%">
<colgroup>
<col style="width: 50%"/>
<col style="width: 50%"/>
</colgroup>
<tbody>
<tr>
<th>
Version (or later)
</th>
<td>
NDB 8.4.0
</td>
</tr>
<tr>
<th>
Type or units
</th>
<td>
name or IP address
</td>
</tr>
<tr>
<th>
Default
</th>
<td>
[...]
</td>
</tr>
<tr>
<th>
Range
</th>
<td>
...
</td>
</tr>
<tr>
<th>
Restart Type
</th>
<td>
<p>
<span class="bold">
<strong>
Node Restart:
</strong>
</span>
Requires a
<a class="link" href="mysql-cluster-rolling-restart.html" title="25.6.5 Performing a Rolling Restart of an NDB Cluster">
rolling
restart
</a>
of the cluster. (NDB 8.4.0)
</p>
</td>
</tr>
</tbody>
</table>
</div>
<p>
The
<a class="link" href="mysql-cluster-shm-definition.html#ndbparam-shm-hostname1">
<code class="literal">
HostName1
</code>
</a>
and
<code class="literal">
HostName2
</code>
parameters can be used to
specify specific network interfaces to be used for a given
SHM connection between two nodes. The values used for these
parameters can be host names or IP addresses.
</p>
</li>
<li class="listitem">
<p>
<a name="ndbparam-shm-nodeid1">
</a>
<code class="literal">
NodeId1
</code>
</p>
<a class="indexterm" name="idm46045108958624">
</a>
<a class="indexterm" name="idm46045108957552">
</a>
<div class="informaltable">
<a name="nodeid1-shm-table">
</a>
<table frame="box" rules="all" summary="NodeId1 shared memory configuration parameter type and value information" width="35%">
<colgroup>
<col style="width: 50%"/>
<col style="width: 50%"/>
</colgroup>
<tbody>
<tr>
<th>
Version (or later)
</th>
<td>
NDB 8.4.0
</td>
</tr>
<tr>
<th>
Type or units
</th>
<td>
numeric
</td>
</tr>
<tr>
<th>
Default
</th>
<td>
[none]
</td>
</tr>
<tr>
<th>
Range
</th>
<td>
1 - 255
</td>
</tr>
<tr>
<th>
Restart Type
</th>
<td>
<p>
<span class="bold">
<strong>
Node Restart:
</strong>
</span>
Requires a
<a class="link" href="mysql-cluster-rolling-restart.html" title="25.6.5 Performing a Rolling Restart of an NDB Cluster">
rolling
restart
</a>
of the cluster. (NDB 8.4.0)
</p>
</td>
</tr>
</tbody>
</table>
</div>
<p>
To identify a connection between two nodes it is necessary
to provide node identifiers for each of them, as
<code class="literal">
NodeId1
</code>
and
<a class="link" href="mysql-cluster-shm-definition.html#ndbparam-shm-nodeid2">
<code class="literal">
NodeId2
</code>
</a>
.
</p>
</li>
<li class="listitem">
<p>
<a name="ndbparam-shm-nodeid2">
</a>
<code class="literal">
NodeId2
</code>
</p>
<a class="indexterm" name="idm46045108935328">
</a>
<a class="indexterm" name="idm46045108934256">
</a>
<div class="informaltable">
<a name="nodeid2-shm-table">
</a>
<table frame="box" rules="all" summary="NodeId2 shared memory configuration parameter type and value information" width="35%">
<colgroup>
<col style="width: 50%"/>
<col style="width: 50%"/>
</colgroup>
<tbody>
<tr>
<th>
Version (or later)
</th>
<td>
NDB 8.4.0
</td>
</tr>
<tr>
<th>
Type or units
</th>
<td>
numeric
</td>
</tr>
<tr>
<th>
Default
</th>
<td>
[none]
</td>
</tr>
<tr>
<th>
Range
</th>
<td>
1 - 255
</td>
</tr>
<tr>
<th>
Restart Type
</th>
<td>
<p>
<span class="bold">
<strong>
Node Restart:
</strong>
</span>
Requires a
<a class="link" href="mysql-cluster-rolling-restart.html" title="25.6.5 Performing a Rolling Restart of an NDB Cluster">
rolling
restart
</a>
of the cluster. (NDB 8.4.0)
</p>
</td>
</tr>
</tbody>
</table>
</div>
<p>
To identify a connection between two nodes it is necessary
to provide node identifiers for each of them, as
<a class="link" href="mysql-cluster-shm-definition.html#ndbparam-shm-nodeid1">
<code class="literal">
NodeId1
</code>
</a>
and
<code class="literal">
NodeId2
</code>
.
</p>
</li>
<li class="listitem">
<p>
<a name="ndbparam-shm-nodeidserver">
</a>
<code class="literal">
NodeIdServer
</code>
</p>
<a class="indexterm" name="idm46045108911952">
</a>
<div class="informaltable">
<a name="nodeidserver-shm-table">
</a>
<table frame="box" rules="all" summary="NodeIdServer shared memory configuration parameter type and value information" width="35%">
<colgroup>
<col style="width: 50%"/>
<col style="width: 50%"/>
</colgroup>
<tbody>
<tr>
<th>
Version (or later)
</th>
<td>
NDB 8.4.0
</td>
</tr>
<tr>
<th>
Type or units
</th>
<td>
numeric
</td>
</tr>
<tr>
<th>
Default
</th>
<td>
[none]
</td>
</tr>
<tr>
<th>
Range
</th>
<td>
1 - 63
</td>
</tr>
<tr>
<th>
Restart Type
</th>
<td>
<p>
<span class="bold">
<strong>
Node Restart:
</strong>
</span>
Requires a
<a class="link" href="mysql-cluster-rolling-restart.html" title="25.6.5 Performing a Rolling Restart of an NDB Cluster">
rolling
restart
</a>
of the cluster. (NDB 8.4.0)
</p>
</td>
</tr>
</tbody>
</table>
</div>
<p>
Identify the server end of a shared memory connection. By
default, this is the node ID of the data node.
</p>
</li>
<li class="listitem">
<p>
<a name="ndbparam-shm-overloadlimit">
</a>
<code class="literal">
OverloadLimit
</code>
</p>
<a class="indexterm" name="idm46045108892064">
</a>
<div class="informaltable">
<a name="overloadlimit-shm-table">
</a>
<table frame="box" rules="all" summary="OverloadLimit shared memory configuration parameter type and value information" width="35%">
<colgroup>
<col style="width: 50%"/>
<col style="width: 50%"/>
</colgroup>
<tbody>
<tr>
<th>
Version (or later)
</th>
<td>
NDB 8.4.0
</td>
</tr>
<tr>
<th>
Type or units
</th>
<td>
bytes
</td>
</tr>
<tr>
<th>
Default
</th>
<td>
0
</td>
</tr>
<tr>
<th>
Range
</th>
<td>
0 - 4294967039 (0xFFFFFEFF)
</td>
</tr>
<tr>
<th>
Restart Type
</th>
<td>
<p>
<span class="bold">
<strong>
Node Restart:
</strong>
</span>
Requires a
<a class="link" href="mysql-cluster-rolling-restart.html" title="25.6.5 Performing a Rolling Restart of an NDB Cluster">
rolling
restart
</a>
of the cluster. (NDB 8.4.0)
</p>
</td>
</tr>
</tbody>
</table>
</div>
<p>
When more than this many unsent bytes are in the send
buffer, the connection is considered overloaded. See
<a class="xref" href="mysql-cluster-config-send-buffers.html" title="25.4.3.14 Configuring NDB Cluster Send Buffer Parameters">
Section 25.4.3.14, “Configuring NDB Cluster Send Buffer Parameters”
</a>
, and
<a class="xref" href="mysql-cluster-ndbinfo-transporters.html" title="25.6.17.66 The ndbinfo transporters Table">
Section 25.6.17.66, “The ndbinfo transporters Table”
</a>
, for
more information.
</p>
</li>
<li class="listitem">
<p>
<a name="ndbparam-shm-presendchecksum">
</a>
<a class="link" href="mysql-cluster-shm-definition.html#ndbparam-shm-presendchecksum">
<code class="literal">
PreSendChecksum
</code>
</a>
</p>
<a class="indexterm" name="idm46045108870256">
</a>
<div class="informaltable">
<a name="presendchecksum-shm-table">
</a>
<table frame="box" rules="all" summary="PreSendChecksum shared memory configuration parameter type and value information" width="35%">
<colgroup>
<col style="width: 50%"/>
<col style="width: 50%"/>
</colgroup>
<tbody>
<tr>
<th>
Version (or later)
</th>
<td>
NDB 8.4.0
</td>
</tr>
<tr>
<th>
Type or units
</th>
<td>
boolean
</td>
</tr>
<tr>
<th>
Default
</th>
<td>
false
</td>
</tr>
<tr>
<th>
Range
</th>
<td>
true, false
</td>
</tr>
<tr>
<th>
Restart Type
</th>
<td>
<p>
<span class="bold">
<strong>
Node Restart:
</strong>
</span>
Requires a
<a class="link" href="mysql-cluster-rolling-restart.html" title="25.6.5 Performing a Rolling Restart of an NDB Cluster">
rolling
restart
</a>
of the cluster. (NDB 8.4.0)
</p>
</td>
</tr>
</tbody>
</table>
</div>
<p>
If this parameter and
<a class="link" href="mysql-cluster-shm-definition.html#ndbparam-shm-checksum">
<code class="literal">
Checksum
</code>
</a>
are both
enabled, perform pre-send checksum checks, and check all SHM
signals between nodes for errors. Has no effect if
<code class="literal">
Checksum
</code>
is not also enabled.
</p>
</li>
<li class="listitem">
<p>
<a name="ndbparam-shm-sendbuffermemory">
</a>
<a class="link" href="mysql-cluster-shm-definition.html#ndbparam-shm-sendbuffermemory">
<code class="literal">
SendBufferMemory
</code>
</a>
</p>
<a class="indexterm" name="idm46045108847776">
</a>
<div class="informaltable">
<a name="sendbuffermemory-shm-table">
</a>
<table frame="box" rules="all" summary="SendBufferMemory shared memory configuration parameter type and value information" width="35%">
<colgroup>
<col style="width: 50%"/>
<col style="width: 50%"/>
</colgroup>
<tbody>
<tr>
<th>
Version (or later)
</th>
<td>
NDB 8.4.0
</td>
</tr>
<tr>
<th>
Type or units
</th>
<td>
integer
</td>
</tr>
<tr>
<th>
Default
</th>
<td>
2M
</td>
</tr>
<tr>
<th>
Range
</th>
<td>
256K - 4294967039 (0xFFFFFEFF)
</td>
</tr>
<tr>
<th>
Restart Type
</th>
<td>
<p>
<span class="bold">
<strong>
Node Restart:
</strong>
</span>
Requires a
<a class="link" href="mysql-cluster-rolling-restart.html" title="25.6.5 Performing a Rolling Restart of an NDB Cluster">
rolling
restart
</a>
of the cluster. (NDB 8.4.0)
</p>
</td>
</tr>
</tbody>
</table>
</div>
<p>
Size (in bytes) of the shared memory buffer for signals sent
from this node using a shared memory connection.
</p>
</li>
<li class="listitem">
<p>
<a name="ndbparam-shm-sendsignalid">
</a>
<code class="literal">
SendSignalId
</code>
</p>
<a class="indexterm" name="idm46045108827872">
</a>
<div class="informaltable">
<a name="sendsignalid-shm-table">
</a>
<table frame="box" rules="all" summary="SendSignalId shared memory configuration parameter type and value information" width="35%">
<colgroup>
<col style="width: 50%"/>
<col style="width: 50%"/>
</colgroup>
<tbody>
<tr>
<th>
Version (or later)
</th>
<td>
NDB 8.4.0
</td>
</tr>
<tr>
<th>
Type or units
</th>
<td>
boolean
</td>
</tr>
<tr>
<th>
Default
</th>
<td>
false
</td>
</tr>
<tr>
<th>
Range
</th>
<td>
true, false
</td>
</tr>
<tr>
<th>
Restart Type
</th>
<td>
<p>
<span class="bold">
<strong>
Node Restart:
</strong>
</span>
Requires a
<a class="link" href="mysql-cluster-rolling-restart.html" title="25.6.5 Performing a Rolling Restart of an NDB Cluster">
rolling
restart
</a>
of the cluster. (NDB 8.4.0)
</p>
</td>
</tr>
</tbody>
</table>
</div>
<p>
To retrace the path of a distributed message, it is
necessary to provide each message with a unique identifier.
Setting this parameter to
<code class="literal">
Y
</code>
causes these
message IDs to be transported over the network as well. This
feature is disabled by default in production builds, and
enabled in
<code class="literal">
-debug
</code>
builds.
</p>
</li>
<li class="listitem">
<p>
<a name="ndbparam-shm-shmkey">
</a>
<a class="link" href="mysql-cluster-shm-definition.html#ndbparam-shm-shmkey">
<code class="literal">
ShmKey
</code>
</a>
</p>
<a class="indexterm" name="idm46045108805888">
</a>
<div class="informaltable">
<a name="shmkey-shm-table">
</a>
<table frame="box" rules="all" summary="ShmKey shared memory configuration parameter type and value information" width="35%">
<colgroup>
<col style="width: 50%"/>
<col style="width: 50%"/>
</colgroup>
<tbody>
<tr>
<th>
Version (or later)
</th>
<td>
NDB 8.4.0
</td>
</tr>
<tr>
<th>
Type or units
</th>
<td>
unsigned
</td>
</tr>
<tr>
<th>
Default
</th>
<td>
0
</td>
</tr>
<tr>
<th>
Range
</th>
<td>
0 - 4294967039 (0xFFFFFEFF)
</td>
</tr>
<tr>
<th>
Restart Type
</th>
<td>
<p>
<span class="bold">
<strong>
Node Restart:
</strong>
</span>
Requires a
<a class="link" href="mysql-cluster-rolling-restart.html" title="25.6.5 Performing a Rolling Restart of an NDB Cluster">
rolling
restart
</a>
of the cluster. (NDB 8.4.0)
</p>
</td>
</tr>
</tbody>
</table>
</div>
<p>
When setting up shared memory segments, a node ID, expressed
as an integer, is used to identify uniquely the shared
memory segment to use for the communication. There is no
default value. If
<a class="link" href="mysql-cluster-ndbd-definition.html#ndbparam-ndbd-useshm">
<code class="literal">
UseShm
</code>
</a>
is enabled,
the shared memory key is calculated automatically by
<code class="literal">
NDB
</code>
.
</p>
</li>
<li class="listitem">
<p>
<a name="ndbparam-shm-shmsize">
</a>
<a class="link" href="mysql-cluster-shm-definition.html#ndbparam-shm-shmsize">
<code class="literal">
ShmSize
</code>
</a>
</p>
<a class="indexterm" name="idm46045108783312">
</a>
<div class="informaltable">
<a name="shmsize-shm-table">
</a>
<table frame="box" rules="all" summary="ShmSize shared memory configuration parameter type and value information" width="35%">
<colgroup>
<col style="width: 50%"/>
<col style="width: 50%"/>
</colgroup>
<tbody>
<tr>
<th>
Version (or later)
</th>
<td>
NDB 8.4.0
</td>
</tr>
<tr>
<th>
Type or units
</th>
<td>
bytes
</td>
</tr>
<tr>
<th>
Default
</th>
<td>
4M
</td>
</tr>
<tr>
<th>
Range
</th>
<td>
64K - 4294967039 (0xFFFFFEFF)
</td>
</tr>
<tr>
<th>
Restart Type
</th>
<td>
<p>
<span class="bold">
<strong>
Node Restart:
</strong>
</span>
Requires a
<a class="link" href="mysql-cluster-rolling-restart.html" title="25.6.5 Performing a Rolling Restart of an NDB Cluster">
rolling
restart
</a>
of the cluster. (NDB 8.4.0)
</p>
</td>
</tr>
</tbody>
</table>
</div>
<p>
Each SHM connection has a shared memory segment where
messages between nodes are placed by the sender and read by
the reader. The size of this segment is defined by
<a class="link" href="mysql-cluster-shm-definition.html#ndbparam-shm-shmsize">
<code class="literal">
ShmSize
</code>
</a>
. The default
value is 4MB.
</p>
</li>
<li class="listitem">
<p>
<a name="ndbparam-shm-shmspintime">
</a>
<a class="link" href="mysql-cluster-shm-definition.html#ndbparam-shm-shmspintime">
<code class="literal">
ShmSpinTime
</code>
</a>
</p>
<a class="indexterm" name="idm46045108761392">
</a>
<div class="informaltable">
<a name="shmspintime-shm-table">
</a>
<table frame="box" rules="all" summary="ShmSpinTime shared memory configuration parameter type and value information" width="35%">
<colgroup>
<col style="width: 50%"/>
<col style="width: 50%"/>
</colgroup>
<tbody>
<tr>
<th>
Version (or later)
</th>
<td>
NDB 8.4.0
</td>
</tr>
<tr>
<th>
Type or units
</th>
<td>
integer
</td>
</tr>
<tr>
<th>
Default
</th>
<td>
0
</td>
</tr>
<tr>
<th>
Range
</th>
<td>
0 - 2000
</td>
</tr>
<tr>
<th>
Restart Type
</th>
<td>
<p>
<span class="bold">
<strong>
Node Restart:
</strong>
</span>
Requires a
<a class="link" href="mysql-cluster-rolling-restart.html" title="25.6.5 Performing a Rolling Restart of an NDB Cluster">
rolling
restart
</a>
of the cluster. (NDB 8.4.0)
</p>
</td>
</tr>
</tbody>
</table>
</div>
<p>
When receiving, the time to wait before sleeping, in
microseconds.
</p>
</li>
<li class="listitem">
<p>
<a name="ndbparam-shm-signum">
</a>
<a class="link" href="mysql-cluster-shm-definition.html#ndbparam-shm-signum">
<code class="literal">
SigNum
</code>
</a>
</p>
<a class="indexterm" name="idm46045108741024">
</a>
<div class="informaltable">
<a name="signum-shm-table">
</a>
<table frame="box" rules="all" summary="Signum shared memory configuration parameter type and value information" width="35%">
<colgroup>
<col style="width: 50%"/>
<col style="width: 50%"/>
</colgroup>
<tbody>
<tr>
<th>
Version (or later)
</th>
<td>
NDB 8.4.0
</td>
</tr>
<tr>
<th>
Type or units
</th>
<td>
unsigned
</td>
</tr>
<tr>
<th>
Default
</th>
<td>
[...]
</td>
</tr>
<tr>
<th>
Range
</th>
<td>
0 - 4294967039 (0xFFFFFEFF)
</td>
</tr>
<tr>
<th>
Deprecated
</th>
<td>
Yes (in NDB 7.6)
</td>
</tr>
<tr>
<th>
Restart Type
</th>
<td>
<p>
<span class="bold">
<strong>
Node Restart:
</strong>
</span>
Requires a
<a class="link" href="mysql-cluster-rolling-restart.html" title="25.6.5 Performing a Rolling Restart of an NDB Cluster">
rolling
restart
</a>
of the cluster. (NDB 8.4.0)
</p>
</td>
</tr>
</tbody>
</table>
</div>
<p>
This parameter was formerly used to override operating
system signal numbers; in NDB 8.4, it is no
longer used, and any setting for it is ignored.
</p>
</li>
</ul>
</div>
<p>
<a name="mysql-cluster-shm-definition-restart-types">
</a>
<b>
Restart types.
</b>
Information about the restart types used by the parameter
descriptions in this section is shown in the following table:
</p>
<div class="table">
<a name="idm46045108718560">
</a>
<p class="title">
<b>
Table 25.21 NDB Cluster restart types
</b>
</p>
<div class="table-contents">
<table>
<colgroup>
<col style="width: 10%"/>
<col style="width: 30%"/>
<col style="width: 60%"/>
</colgroup>
<thead>
<tr>
<th scope="col">
Symbol
</th>
<th scope="col">
Restart Type
</th>
<th scope="col">
Description
</th>
</tr>
</thead>
<tbody>
<tr>
<th scope="row">
N
</th>
<td>
Node
</td>
<td>
The parameter can be updated using a rolling restart (see
<a class="xref" href="mysql-cluster-rolling-restart.html" title="25.6.5 Performing a Rolling Restart of an NDB Cluster">
Section 25.6.5, “Performing a Rolling Restart of an NDB Cluster”
</a>
)
</td>
</tr>
<tr>
<th scope="row">
S
</th>
<td>
System
</td>
<td>
All cluster nodes must be shut down completely, then restarted, to
effect a change in this parameter
</td>
</tr>
<tr>
<th scope="row">
I
</th>
<td>
Initial
</td>
<td>
Data nodes must be restarted using the
<a class="link" href="mysql-cluster-programs-ndbd.html#option_ndbd_initial">
<code class="option">
--initial
</code>
</a>
option
</td>
</tr>
</tbody>
</table>
</div>
</div>
<br class="table-break"/>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/information-schema-collation-character-set-applicability-table.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="information-schema-collation-character-set-applicability-table">
</a>
28.3.7 The INFORMATION_SCHEMA COLLATION_CHARACTER_SET_APPLICABILITY Table
</h3>
</div>
</div>
</div>
<a class="indexterm" name="idm46045080270048">
</a>
<p>
The
<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>
table indicates what character set is applicable for what
collation.
</p>
<p>
The
<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>
table has these columns:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<code class="literal">
COLLATION_NAME
</code>
</p>
<p>
The collation name.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
CHARACTER_SET_NAME
</code>
</p>
<p>
The name of the character set with which the collation is
associated.
</p>
</li>
</ul>
</div>
<h4>
<a name="idm46045080260624">
</a>
Notes
</h4>
<p>
The
<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>
columns are equivalent to the first two columns displayed by the
<a class="link" href="show-collation.html" title="15.7.7.5 SHOW COLLATION Statement">
<code class="literal">
SHOW COLLATION
</code>
</a>
statement.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/replication-multi-source-start-replica.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="replication-multi-source-start-replica">
</a>
19.1.5.5 Starting Multi-Source Replicas
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045145174208">
</a>
<p>
Once you have added channels for all of the replication sources,
issue a
<a class="link" href="start-replica.html" title="15.4.2.4 START REPLICA Statement">
<code class="literal">
START REPLICA
</code>
</a>
statement to
start replication. When you have enabled multiple channels on a
replica, you can choose to either start all channels, or select a
specific channel to start. For example, to start the two channels
separately, use 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 to issue the
following statements:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa73873658"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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">REPLICA</span> <span class="token keyword">FOR</span> <span class="token keyword">CHANNEL</span> <span class="token string">"source_1"</span><span class="token punctuation">;</span>
<span class="token prompt">mysql></span> <span class="token keyword">START</span> <span class="token keyword">REPLICA</span> <span class="token keyword">FOR</span> <span class="token keyword">CHANNEL</span> <span class="token string">"source_2"</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
For the full syntax of the
<a class="link" href="start-replica.html" title="15.4.2.4 START REPLICA Statement">
<code class="literal">
START
REPLICA
</code>
</a>
statement and other available options, see
<a class="xref" href="start-replica.html" title="15.4.2.4 START REPLICA Statement">
Section 15.4.2.4, “START REPLICA Statement”
</a>
.
</p>
<p>
To verify that both channels have started and are operating
correctly, you can issue
<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>
statements on the replica, for example:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa94082173"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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">REPLICA</span> <span class="token keyword">STATUS</span> <span class="token keyword">FOR</span> <span class="token keyword">CHANNEL</span> <span class="token string">"source_1"</span>\G
<span class="token prompt">mysql></span> <span class="token keyword">SHOW</span> <span class="token keyword">REPLICA</span> <span class="token keyword">STATUS</span> <span class="token keyword">FOR</span> <span class="token keyword">CHANNEL</span> <span class="token string">"source_2"</span>\G</code></pre>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/aggregate-functions-and-modifiers.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h2 class="title">
<a name="aggregate-functions-and-modifiers">
</a>
14.19 Aggregate Functions
</h2>
</div>
</div>
</div>
<div class="toc">
<dl class="toc">
<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>
</div>
<p>
Aggregate functions operate on sets of values. They are often used
with a
<code class="literal">
GROUP BY
</code>
clause to group values into
subsets. This section describes most aggregate functions. For
information about aggregate functions that operate on geometry
values, see
<a class="xref" href="spatial-aggregate-functions.html" title="14.16.12 Spatial Aggregate Functions">
Section 14.16.12, “Spatial Aggregate Functions”
</a>
.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/performance-schema-keyring-component-status-table.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="performance-schema-keyring-component-status-table">
</a>
29.12.18.1 The keyring_component_status Table
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045069508752">
</a>
<a class="indexterm" name="idm46045069507248">
</a>
<p>
The
<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 properties of the
keyring component in use, if one is installed. The table is
empty if no keyring component is installed (for example, if
the keyring is not being used, or is configured to manage the
keystore using a keyring plugin rather than a keyring
component).
</p>
<p>
There is no fixed set of properties. Each keyring component is
free to define its own set.
</p>
<p>
Example
<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>
contents:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa3392717"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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>keyring_component_status<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> STATUS_KEY <span class="token punctuation">|</span> STATUS_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 class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><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> Component_name <span class="token punctuation">|</span> component_keyring_file <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> Author <span class="token punctuation">|</span> Oracle Corporation <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> License <span class="token punctuation">|</span> GPL <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> Implementation_name <span class="token punctuation">|</span> component_keyring_file <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> Version <span class="token punctuation">|</span> 1.0 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> Component_status <span class="token punctuation">|</span> Active <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> Data_file <span class="token punctuation">|</span> /usr/local/mysql/keyring/component_keyring_file <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> Read_only <span class="token punctuation">|</span> No <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></code></pre>
</div>
<p>
The
<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 has these columns:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<code class="literal">
STATUS_KEY
</code>
</p>
<p>
The status item name.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
STATUS_VALUE
</code>
</p>
<p>
The status item value.
</p>
</li>
</ul>
</div>
<p>
The
<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 has no indexes.
</p>
<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-keyring-component-status-table.html" title="29.12.18.1 The keyring_component_status Table">
<code class="literal">
keyring_component_status
</code>
</a>
table.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/mysql-shell-tutorial-javascript-table-select.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="mysql-shell-tutorial-javascript-table-select">
</a>
22.3.4.2 Select Tables
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045127582048">
</a>
<p>
You can use the
<code class="literal">
select()
</code>
method to query for
and return records from a table in a database. The X DevAPI
provides additional methods to use with the
<code class="literal">
select()
</code>
method to filter and sort the
returned records.
</p>
<p>
MySQL provides the following operators to specify search
conditions:
<code class="literal">
OR
</code>
(
<code class="literal">
||
</code>
),
<code class="literal">
AND
</code>
(
<code class="literal">
&&
</code>
),
<code class="literal">
XOR
</code>
,
<code class="literal">
IS
</code>
,
<code class="literal">
NOT
</code>
,
<code class="literal">
BETWEEN
</code>
,
<code class="literal">
IN
</code>
,
<code class="literal">
LIKE
</code>
,
<code class="literal">
!=
</code>
,
<code class="literal">
<>
</code>
,
<code class="literal">
>
</code>
,
<code class="literal">
>=
</code>
,
<code class="literal">
<
</code>
,
<code class="literal">
<=
</code>
,
<code class="literal">
&
</code>
,
<code class="literal">
|
</code>
,
<code class="literal">
<<
</code>
,
<code class="literal">
>>
</code>
,
<code class="literal">
+
</code>
,
<code class="literal">
-
</code>
,
<code class="literal">
*
</code>
,
<code class="literal">
/
</code>
,
<code class="literal">
~
</code>
, and
<code class="literal">
%
</code>
.
</p>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h5 class="title">
<a name="mysql-shell-tutorial-javascript-select-all-records">
</a>
Select All Records
</h5>
</div>
</div>
</div>
<a class="indexterm" name="idm46045127558944">
</a>
<p>
To issue a query that returns all records from an existing
table, use the
<code class="literal">
select()
</code>
method without
specifying search conditions. The following example selects
all records from the city table in the
<code class="literal">
world_x
</code>
database.
</p>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
Limit the use of the empty
<code class="literal">
select()
</code>
method to interactive statements. Always use explicit
column-name selections in your application code.
</p>
</div>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-mysqlsh"><div class="docs-select-all right" id="sa29425894"><div class="copy-help left">Press ⌘+C to 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-js></span> db<span class="token punctuation">.</span>city<span class="token punctuation">.</span><span class="token function">select</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>
<span class="token output"><span class="token punctuation">|</span> ID <span class="token punctuation">|</span> Name <span class="token punctuation">|</span> CountryCode <span class="token punctuation">|</span> District <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 class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><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> Kabul <span class="token punctuation">|</span> AFG <span class="token punctuation">|</span> Kabol <span class="token punctuation">|</span>{"Population": 1780000} <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 2 <span class="token punctuation">|</span> Qandahar <span class="token punctuation">|</span> AFG <span class="token punctuation">|</span> Qandahar <span class="token punctuation">|</span>{"Population": 237500} <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 3 <span class="token punctuation">|</span> Herat <span class="token punctuation">|</span> AFG <span class="token punctuation">|</span> Herat <span class="token punctuation">|</span>{"Population": 186800} <span class="token punctuation">|</span></span>
<span class="token operator">...</span> <span class="token operator">...</span> <span class="token operator">...</span> <span class="token operator">...</span> <span class="token operator">...</span>
<span class="token output"><span class="token punctuation">|</span> 4079 <span class="token punctuation">|</span> Rafah <span class="token punctuation">|</span> PSE <span class="token punctuation">|</span> Rafah <span class="token punctuation">|</span>{"Population": 92020} <span class="token punctuation">|</span></span>
<span class="token operator">+</span><span class="token operator">--</span><span class="token operator">--</span><span class="token operator">--</span><span class="token operator">+</span><span class="token operator">--</span><span class="token operator">--</span><span class="token operator">--</span><span class="token operator">-</span> <span class="token operator">--</span><span class="token operator">--</span><span class="token operator">+</span><span class="token operator">--</span><span class="token operator">--</span><span class="token operator">--</span><span class="token operator">--</span><span class="token operator">--</span><span class="token operator">--</span><span class="token operator">-</span><span class="token operator">+</span><span class="token operator">--</span><span class="token operator">--</span><span class="token operator">--</span><span class="token operator">--</span><span class="token operator">--</span><span class="token operator">--</span><span class="token operator">+</span><span class="token operator">--</span><span class="token operator">--</span><span class="token operator">--</span><span class="token operator">--</span><span class="token operator">--</span><span class="token operator">--</span><span class="token operator">--</span><span class="token operator">--</span><span class="token operator">--</span><span class="token operator">--</span><span class="token operator">--</span><span class="token operator">--</span><span class="token operator">-</span><span class="token operator">+</span>
<span class="token output">4082 rows in set (0.01 sec)</span></code></pre>
</div>
<p>
An empty set (no matching records) returns the following
information:
</p>
<pre class="screen">Empty set (0.00 sec)
</pre>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h5 class="title">
<a name="mysql-shell-tutorial-javascript-filter-searches">
</a>
Filter Searches
</h5>
</div>
</div>
</div>
<a class="indexterm" name="idm46045127548928">
</a>
<p>
To issue a query that returns a set of table columns, use the
<code class="literal">
select()
</code>
method and specify the columns to
return between square brackets. This query returns the Name
and CountryCode columns from the city table.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-mysqlsh"><div class="docs-select-all right" id="sa55843529"><div class="copy-help left">Press ⌘+C to 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-js></span> db<span class="token punctuation">.</span>city<span class="token punctuation">.</span><span class="token function">select</span><span class="token punctuation">(</span><span class="token punctuation">[</span><span class="token string">"Name"</span><span class="token punctuation">,</span> <span class="token string">"CountryCode"</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> Name <span class="token punctuation">|</span> CountryCode <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> Kabul <span class="token punctuation">|</span> AFG <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> Qandahar <span class="token punctuation">|</span> AFG <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> Herat <span class="token punctuation">|</span> AFG <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> Mazar<span class="token punctuation">-</span>e<span class="token punctuation">-</span>Sharif <span class="token punctuation">|</span> AFG <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> Amsterdam <span class="token punctuation">|</span> NLD <span class="token punctuation">|</span></span>
<span class="token operator">...</span> <span class="token operator">...</span>
<span class="token output"><span class="token punctuation">|</span> Rafah <span class="token punctuation">|</span> PSE <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> Olympia <span class="token punctuation">|</span> USA <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> Little Falls <span class="token punctuation">|</span> USA <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> Happy Valley <span class="token punctuation">|</span> USA <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">4082 rows in set (0.00 sec)</span></code></pre>
</div>
<p>
To issue a query that returns rows matching specific search
conditions, use the
<code class="literal">
where()
</code>
method to
include those conditions. For example, the following example
returns the names and country codes of the cities that start
with the letter Z.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-mysqlsh"><div class="docs-select-all right" id="sa27310473"><div class="copy-help left">Press ⌘+C to 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-js></span> db<span class="token punctuation">.</span>city<span class="token punctuation">.</span><span class="token function">select</span><span class="token punctuation">(</span><span class="token punctuation">[</span><span class="token string">"Name"</span><span class="token punctuation">,</span> <span class="token string">"CountryCode"</span><span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">where</span><span class="token punctuation">(</span><span class="token string">"Name like 'Z%'"</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> Name <span class="token punctuation">|</span> CountryCode <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> Zaanstad <span class="token punctuation">|</span> NLD <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> Zoetermeer <span class="token punctuation">|</span> NLD <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> Zwolle <span class="token punctuation">|</span> NLD <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> Zenica <span class="token punctuation">|</span> BIH <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> Zagazig <span class="token punctuation">|</span> EGY <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> Zaragoza <span class="token punctuation">|</span> ESP <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> Zamboanga <span class="token punctuation">|</span> PHL <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> Zahedan <span class="token punctuation">|</span> IRN <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> Zanjan <span class="token punctuation">|</span> IRN <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> Zabol <span class="token punctuation">|</span> IRN <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> Zama <span class="token punctuation">|</span> JPN <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> Zhezqazghan <span class="token punctuation">|</span> KAZ <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> Zhengzhou <span class="token punctuation">|</span> CHN <span class="token punctuation">|</span></span>
<span class="token operator">...</span> <span class="token operator">...</span>
<span class="token output"><span class="token punctuation">|</span> Zeleznogorsk <span class="token punctuation">|</span> RUS <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">59 rows in set (0.00 sec)</span></code></pre>
</div>
<p>
You can separate a value from the search condition by using
the
<code class="literal">
bind()
</code>
method. For example, instead of
using "Name = 'Z%' " as the condition, substitute a named
placeholder consisting of a colon followed by a name that
begins with a letter, such as
<span class="emphasis">
<em>
name
</em>
</span>
. Then
include the placeholder and value in the
<code class="literal">
bind()
</code>
method as follows:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-mysqlsh"><div class="docs-select-all right" id="sa26890190"><div class="copy-help left">Press ⌘+C to 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-js></span> db<span class="token punctuation">.</span>city<span class="token punctuation">.</span><span class="token function">select</span><span class="token punctuation">(</span><span class="token punctuation">[</span><span class="token string">"Name"</span><span class="token punctuation">,</span> <span class="token string">"CountryCode"</span><span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token punctuation">.</span>
<span class="token function">where</span><span class="token punctuation">(</span><span class="token string">"Name like :name"</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">"name"</span><span class="token punctuation">,</span> <span class="token string">"Z%"</span><span class="token punctuation">)</span></code></pre>
</div>
<div class="tip" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Tip
</div>
<p>
Within a program, binding enables you to specify
placeholders in your expressions, which are filled in with
values before execution and can benefit from automatic
escaping, as appropriate.
</p>
<p>
Always use binding to sanitize input. Avoid introducing
values in queries using string concatenation, which can
produce invalid input and, in some cases, can cause security
issues.
</p>
</div>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h5 class="title">
<a name="mysql-shell-tutorial-javascript-project-results">
</a>
Project Results
</h5>
</div>
</div>
</div>
<a class="indexterm" name="idm46045127532784">
</a>
<p>
To issue a query using the
<a class="link" href="logical-operators.html#operator_and">
<code class="literal">
AND
</code>
</a>
operator, add the operator between search conditions in the
<code class="literal">
where()
</code>
method.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-mysqlsh"><div class="docs-select-all right" id="sa73317001"><div class="copy-help left">Press ⌘+C to 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-js></span> db<span class="token punctuation">.</span>city<span class="token punctuation">.</span><span class="token function">select</span><span class="token punctuation">(</span><span class="token punctuation">[</span><span class="token string">"Name"</span><span class="token punctuation">,</span> <span class="token string">"CountryCode"</span><span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">where</span><span class="token punctuation">(</span>
<span class="token string">"Name like 'Z%' and CountryCode = 'CHN'"</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> Name <span class="token punctuation">|</span> CountryCode <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> Zhengzhou <span class="token punctuation">|</span> CHN <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> Zibo <span class="token punctuation">|</span> CHN <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> Zhangjiakou <span class="token punctuation">|</span> CHN <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> Zhuzhou <span class="token punctuation">|</span> CHN <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> Zhangjiang <span class="token punctuation">|</span> CHN <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> Zigong <span class="token punctuation">|</span> CHN <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> Zaozhuang <span class="token punctuation">|</span> CHN <span class="token punctuation">|</span></span>
<span class="token operator">...</span> <span class="token operator">...</span>
<span class="token output"><span class="token punctuation">|</span> Zhangjiagang <span class="token punctuation">|</span> CHN <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">22 rows in set (0.01 sec)</span></code></pre>
</div>
<p>
To specify multiple conditional operators, you can enclose the
search conditions in parenthesis to change the operator
precedence. The following example demonstrates the placement
of
<a class="link" href="logical-operators.html#operator_and">
<code class="literal">
AND
</code>
</a>
and
<a class="link" href="logical-operators.html#operator_or">
<code class="literal">
OR
</code>
</a>
operators.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-mysqlsh"><div class="docs-select-all right" id="sa4644561"><div class="copy-help left">Press ⌘+C to 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-js></span> db<span class="token punctuation">.</span>city<span class="token punctuation">.</span><span class="token function">select</span><span class="token punctuation">(</span><span class="token punctuation">[</span><span class="token string">"Name"</span><span class="token punctuation">,</span> <span class="token string">"CountryCode"</span><span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token punctuation">.</span>
<span class="token function">where</span><span class="token punctuation">(</span><span class="token string">"Name like 'Z%' and (CountryCode = 'CHN' or CountryCode = 'RUS')"</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> Name <span class="token punctuation">|</span> CountryCode <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> Zhengzhou <span class="token punctuation">|</span> CHN <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> Zibo <span class="token punctuation">|</span> CHN <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> Zhangjiakou <span class="token punctuation">|</span> CHN <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> Zhuzhou <span class="token punctuation">|</span> CHN <span class="token punctuation">|</span></span>
<span class="token operator">...</span> <span class="token operator">...</span>
<span class="token output"><span class="token punctuation">|</span> Zeleznogorsk <span class="token punctuation">|</span> RUS <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">29 rows in set (0.01 sec)</span></code></pre>
</div>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h5 class="title">
<a name="mysql-shell-tutorial-javascript-limit-order-offset-results">
</a>
Limit, Order, and Offset Results
</h5>
</div>
</div>
</div>
<a class="indexterm" name="idm46045127520176">
</a>
<p>
You can apply the
<code class="literal">
limit()
</code>
,
<code class="literal">
orderBy()
</code>
, and
<code class="literal">
offSet()
</code>
methods to manage the number and order of records returned by
the
<code class="literal">
select()
</code>
method.
</p>
<p>
To specify the number of records included in a result set,
append the
<code class="literal">
limit()
</code>
method with a value to
the
<code class="literal">
select()
</code>
method. For example, the
following query returns the first five records in the country
table.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-mysqlsh"><div class="docs-select-all right" id="sa36656999"><div class="copy-help left">Press ⌘+C to 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-js></span> db<span class="token punctuation">.</span>country<span class="token punctuation">.</span><span class="token function">select</span><span class="token punctuation">(</span><span class="token punctuation">[</span><span class="token string">"Code"</span><span class="token punctuation">,</span> <span class="token string">"Name"</span><span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">limit</span><span class="token punctuation">(</span><span class="token number">5</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> Code <span class="token punctuation">|</span> 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>
<span class="token output"><span class="token punctuation">|</span> ABW <span class="token punctuation">|</span> Aruba <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> AFG <span class="token punctuation">|</span> Afghanistan <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> AGO <span class="token punctuation">|</span> Angola <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> AIA <span class="token punctuation">|</span> Anguilla <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> ALB <span class="token punctuation">|</span> Albania <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">5 rows in set (0.00 sec)</span></code></pre>
</div>
<p>
To specify an order for the results, append the
<code class="literal">
orderBy()
</code>
method to the
<code class="literal">
select()
</code>
method. Pass to the
<code class="literal">
orderBy()
</code>
method a list of one or more
columns to sort by and, optionally, the descending
(
<code class="literal">
desc
</code>
) or ascending
(
<code class="literal">
asc
</code>
) attribute as appropriate. Ascending
order is the default order type.
</p>
<p>
For example, the following query sorts all records by the Name
column and then returns the first three records in descending
order .
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-mysqlsh"><div class="docs-select-all right" id="sa89349612"><div class="copy-help left">Press ⌘+C to 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-js></span> db<span class="token punctuation">.</span>country<span class="token punctuation">.</span><span class="token function">select</span><span class="token punctuation">(</span><span class="token punctuation">[</span><span class="token string">"Code"</span><span class="token punctuation">,</span> <span class="token string">"Name"</span><span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">orderBy</span><span class="token punctuation">(</span><span class="token punctuation">[</span><span class="token string">"Name desc"</span><span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">limit</span><span class="token punctuation">(</span><span class="token number">3</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> Code <span class="token punctuation">|</span> 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>
<span class="token output"><span class="token punctuation">|</span> ZWE <span class="token punctuation">|</span> Zimbabwe <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> ZMB <span class="token punctuation">|</span> Zambia <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> YUG <span class="token punctuation">|</span> Yugoslavia <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">3 rows in set (0.00 sec)</span></code></pre>
</div>
<p>
By default, the
<code class="literal">
limit()
</code>
method starts from
the first record in the table. You can use the
<code class="literal">
offset()
</code>
method to change the starting
record. For example, to ignore the first record and return the
next three records matching the condition, pass to the
<code class="literal">
offset()
</code>
method a value of 1.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-mysqlsh"><div class="docs-select-all right" id="sa95590822"><div class="copy-help left">Press ⌘+C to 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-js></span> db<span class="token punctuation">.</span>country<span class="token punctuation">.</span><span class="token function">select</span><span class="token punctuation">(</span><span class="token punctuation">[</span><span class="token string">"Code"</span><span class="token punctuation">,</span> <span class="token string">"Name"</span><span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">orderBy</span><span class="token punctuation">(</span><span class="token punctuation">[</span><span class="token string">"Name desc"</span><span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">limit</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 function">offset</span><span class="token punctuation">(</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>
<span class="token output"><span class="token punctuation">|</span> Code <span class="token punctuation">|</span> 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>
<span class="token output"><span class="token punctuation">|</span> ZMB <span class="token punctuation">|</span> Zambia <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> YUG <span class="token punctuation">|</span> Yugoslavia <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> YEM <span class="token punctuation">|</span> Yemen <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">3 rows in set (0.00 sec)</span></code></pre>
</div>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h5 class="title">
<a name="idm46045127499792">
</a>
Related Information
</h5>
</div>
</div>
</div>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
The
<a class="link" href="functions.html" title="Chapter 14 Functions and Operators">
MySQL Reference
Manual
</a>
provides detailed documentation on functions
and operators.
</p>
</li>
<li class="listitem">
<p>
See
<a class="ulink" href="/doc/x-devapi-userguide/en/crud-ebnf-table-crud-functions.html#crud-ebnf-tableselectfunction" target="_top">
TableSelectFunction
</a>
for
the full syntax definition.
</p>
</li>
</ul>
</div>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/char.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="char">
</a>
13.3.2 The CHAR and VARCHAR Types
</h3>
</div>
</div>
</div>
<a class="indexterm" name="idm46045212759184">
</a>
<a class="indexterm" name="idm46045212757728">
</a>
<a class="indexterm" name="idm46045212756240">
</a>
<p>
The
<code class="literal">
CHAR
</code>
and
<code class="literal">
VARCHAR
</code>
types
are similar, but differ in the way they are stored and
retrieved. They also differ in maximum length and in whether
trailing spaces are retained.
</p>
<p>
The
<code class="literal">
CHAR
</code>
and
<code class="literal">
VARCHAR
</code>
types
are declared with a length that indicates the maximum number of
characters you want to store. For example,
<code class="literal">
CHAR(30)
</code>
can hold up to 30 characters.
</p>
<p>
The length of a
<code class="literal">
CHAR
</code>
column is fixed to the
length that you declare when you create the table. The length
can be any value from 0 to 255. When
<code class="literal">
CHAR
</code>
values are stored, they are right-padded with spaces to the
specified length. When
<code class="literal">
CHAR
</code>
values are
retrieved, trailing spaces are removed unless the
<a class="link" href="sql-mode.html#sqlmode_pad_char_to_full_length">
<code class="literal">
PAD_CHAR_TO_FULL_LENGTH
</code>
</a>
SQL
mode is enabled.
</p>
<p>
Values in
<code class="literal">
VARCHAR
</code>
columns are variable-length
strings. The length can be specified as a value from 0 to
65,535. The effective maximum length of a
<code class="literal">
VARCHAR
</code>
is subject to the maximum row size
(65,535 bytes, which is shared among all columns) and the
character set used. See
<a class="xref" href="column-count-limit.html" title="10.4.7 Limits on Table Column Count and Row Size">
Section 10.4.7, “Limits on Table Column Count and Row Size”
</a>
.
</p>
<p>
In contrast to
<code class="literal">
CHAR
</code>
,
<code class="literal">
VARCHAR
</code>
values are stored as a 1-byte or
2-byte length prefix plus data. The length prefix indicates the
number of bytes in the value. A column uses one length byte if
values require no more than 255 bytes, two length bytes if
values may require more than 255 bytes.
</p>
<p>
If strict SQL mode is not enabled and you assign a value to a
<code class="literal">
CHAR
</code>
or
<code class="literal">
VARCHAR
</code>
column
that exceeds the column's maximum length, the value is truncated
to fit and a warning is generated. For truncation of nonspace
characters, you can cause an error to occur (rather than a
warning) and suppress insertion of the value by using strict SQL
mode. See
<a class="xref" href="sql-mode.html" title="7.1.11 Server SQL Modes">
Section 7.1.11, “Server SQL Modes”
</a>
.
</p>
<p>
For
<code class="literal">
VARCHAR
</code>
columns, trailing spaces in
excess of the column length are truncated prior to insertion and
a warning is generated, regardless of the SQL mode in use. For
<code class="literal">
CHAR
</code>
columns, truncation of excess trailing
spaces from inserted values is performed silently regardless of
the SQL mode.
</p>
<p>
<code class="literal">
VARCHAR
</code>
values are not padded when they are
stored. Trailing spaces are retained when values are stored and
retrieved, in conformance with standard SQL.
</p>
<p>
The following table illustrates the differences between
<code class="literal">
CHAR
</code>
and
<code class="literal">
VARCHAR
</code>
by
showing the result of storing various string values into
<code class="literal">
CHAR(4)
</code>
and
<code class="literal">
VARCHAR(4)
</code>
columns (assuming that the column uses a single-byte character
set such as
<code class="literal">
latin1
</code>
).
</p>
<div class="informaltable">
<table summary="Illustration of the difference between CHAR and VARCHAR storage requirements by showing the required storage for various string values in CHAR(4) and VARCHAR(4) columns.">
<colgroup>
<col style="width: 15%"/>
<col style="width: 15%"/>
<col style="width: 20%"/>
<col style="width: 15%"/>
<col style="width: 20%"/>
</colgroup>
<thead>
<tr>
<th scope="col">
Value
</th>
<th scope="col">
<code class="literal">
CHAR(4)
</code>
</th>
<th scope="col">
Storage Required
</th>
<th scope="col">
<code class="literal">
VARCHAR(4)
</code>
</th>
<th scope="col">
Storage Required
</th>
</tr>
</thead>
<tbody>
<tr>
<th scope="row">
<code class="literal">
''
</code>
</th>
<td>
<code class="literal">
' '
</code>
</td>
<td>
4 bytes
</td>
<td>
<code class="literal">
''
</code>
</td>
<td>
1 byte
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
'ab'
</code>
</th>
<td>
<code class="literal">
'ab '
</code>
</td>
<td>
4 bytes
</td>
<td>
<code class="literal">
'ab'
</code>
</td>
<td>
3 bytes
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
'abcd'
</code>
</th>
<td>
<code class="literal">
'abcd'
</code>
</td>
<td>
4 bytes
</td>
<td>
<code class="literal">
'abcd'
</code>
</td>
<td>
5 bytes
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
'abcdefgh'
</code>
</th>
<td>
<code class="literal">
'abcd'
</code>
</td>
<td>
4 bytes
</td>
<td>
<code class="literal">
'abcd'
</code>
</td>
<td>
5 bytes
</td>
</tr>
</tbody>
</table>
</div>
<p>
The values shown as stored in the last row of the table apply
<span class="emphasis">
<em>
only when not using strict SQL mode
</em>
</span>
; if
strict mode is enabled, values that exceed the column length are
<span class="emphasis">
<em>
not stored
</em>
</span>
, and an error results.
</p>
<p>
<code class="literal">
InnoDB
</code>
encodes fixed-length fields greater
than or equal to 768 bytes in length as variable-length fields,
which can be stored off-page. For example, a
<code class="literal">
CHAR(255)
</code>
column can exceed 768 bytes if the
maximum byte length of the character set is greater than 3, as
it is with
<code class="literal">
utf8mb4
</code>
.
</p>
<p>
If a given value is stored into the
<code class="literal">
CHAR(4)
</code>
and
<code class="literal">
VARCHAR(4)
</code>
columns, the values retrieved
from the columns are not always the same because trailing spaces
are removed from
<code class="literal">
CHAR
</code>
columns upon retrieval.
The following example illustrates this difference:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa57018946"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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> vc <span class="token punctuation">(</span>v <span class="token datatype">VARCHAR</span><span class="token punctuation">(</span><span class="token number">4</span><span class="token punctuation">)</span><span class="token punctuation">,</span> c <span class="token datatype">CHAR</span><span class="token punctuation">(</span><span class="token number">4</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output">Query OK, 0 rows affected (0.01 sec)</span>
<span class="token prompt">mysql></span> <span class="token keyword">INSERT</span> <span class="token keyword">INTO</span> vc <span class="token keyword">VALUES</span> <span class="token punctuation">(</span><span class="token string">'ab '</span><span class="token punctuation">,</span> <span class="token string">'ab '</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output">Query OK, 1 row affected (0.00 sec)</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">CONCAT</span><span class="token punctuation">(</span><span class="token string">'('</span><span class="token punctuation">,</span> v<span class="token punctuation">,</span> <span class="token string">')'</span><span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token function">CONCAT</span><span class="token punctuation">(</span><span class="token string">'('</span><span class="token punctuation">,</span> c<span class="token punctuation">,</span> <span class="token string">')'</span><span class="token punctuation">)</span> <span class="token keyword">FROM</span> vc<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> CONCAT('(', v, ')') <span class="token punctuation">|</span> CONCAT('(', 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 class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><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> (ab ) <span class="token punctuation">|</span> (ab) <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">1 row in set (0.06 sec)</span></code></pre>
</div>
<p>
Values in
<code class="literal">
CHAR
</code>
,
<code class="literal">
VARCHAR
</code>
,
and
<code class="literal">
TEXT
</code>
columns are sorted and compared
according to the character set collation assigned to the column.
</p>
<a class="indexterm" name="idm46045212678880">
</a>
<a class="indexterm" name="idm46045212677392">
</a>
<a class="indexterm" name="idm46045212675904">
</a>
<a class="indexterm" name="idm46045212674832">
</a>
<a class="indexterm" name="idm46045212673344">
</a>
<p>
MySQL collations have a pad attribute of
<code class="literal">
PAD
SPACE
</code>
, other than Unicode collations based on UCA
9.0.0 and higher, which have a pad attribute of
<code class="literal">
NO
PAD
</code>
. (see
<a class="xref" href="charset-unicode-sets.html" title="12.10.1 Unicode Character Sets">
Section 12.10.1, “Unicode Character Sets”
</a>
).
</p>
<p>
To determine the pad attribute for a collation, use the
<code class="literal">
INFORMATION_SCHEMA
</code>
<a class="link" href="information-schema-collations-table.html" title="28.3.6 The INFORMATION_SCHEMA COLLATIONS Table">
<code class="literal">
COLLATIONS
</code>
</a>
table, which has a
<code class="literal">
PAD_ATTRIBUTE
</code>
column.
</p>
<p>
For nonbinary strings (
<code class="literal">
CHAR
</code>
,
<code class="literal">
VARCHAR
</code>
, and
<code class="literal">
TEXT
</code>
values),
the string collation pad attribute determines treatment in
comparisons of trailing spaces at the end of strings.
<code class="literal">
NO PAD
</code>
collations treat trailing spaces as
significant in comparisons, like any other character.
<code class="literal">
PAD SPACE
</code>
collations treat trailing spaces as
insignificant in comparisons; strings are compared without
regard to trailing spaces. See
<a class="xref" href="charset-binary-collations.html#charset-binary-collations-trailing-space-comparisons" title="Trailing Space Handling in Comparisons">
Trailing Space Handling in Comparisons
</a>
.
The server SQL mode has no effect on comparison behavior with
respect to trailing spaces.
</p>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
For more information about MySQL character sets and
collations, see
<a class="xref" href="charset.html" title="Chapter 12 Character Sets, Collations, Unicode">
Chapter 12,
<i>
Character Sets, Collations, Unicode
</i>
</a>
. For additional
information about storage requirements, see
<a class="xref" href="storage-requirements.html" title="13.7 Data Type Storage Requirements">
Section 13.7, “Data Type Storage Requirements”
</a>
.
</p>
</div>
<p>
For those cases where trailing pad characters are stripped or
comparisons ignore them, if a column has an index that requires
unique values, inserting into the column values that differ only
in number of trailing pad characters results in a duplicate-key
error. For example, if a table contains
<code class="literal">
'a'
</code>
,
an attempt to store
<code class="literal">
'a '
</code>
causes a
duplicate-key error.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/time.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="time">
</a>
13.2.3 The TIME Type
</h3>
</div>
</div>
</div>
<a class="indexterm" name="idm46045213553680">
</a>
<a class="indexterm" name="idm46045213552608">
</a>
<p>
MySQL retrieves and displays
<code class="literal">
TIME
</code>
values in
<em class="replaceable">
<code>
'hh:mm:ss'
</code>
</em>
format (or
<em class="replaceable">
<code>
'hhh:mm:ss'
</code>
</em>
format for large hours
values).
<code class="literal">
TIME
</code>
values may range from
<code class="literal">
'-838:59:59'
</code>
to
<code class="literal">
'838:59:59'
</code>
. The hours part may be so large
because the
<code class="literal">
TIME
</code>
type can be used not only to
represent a time of day (which must be less than 24 hours), but
also elapsed time or a time interval between two events (which
may be much greater than 24 hours, or even negative).
</p>
<p>
MySQL recognizes
<code class="literal">
TIME
</code>
values in several
formats, some of which can include a trailing fractional seconds
part in up to microseconds (6 digits) precision. See
<a class="xref" href="date-and-time-literals.html" title="11.1.3 Date and Time Literals">
Section 11.1.3, “Date and Time Literals”
</a>
. For information about
fractional seconds support in MySQL, see
<a class="xref" href="fractional-seconds.html" title="13.2.6 Fractional Seconds in Time Values">
Section 13.2.6, “Fractional Seconds in Time Values”
</a>
. In particular, any
fractional part in a value inserted into a
<code class="literal">
TIME
</code>
column is stored rather than discarded.
With the fractional part included, the range for
<code class="literal">
TIME
</code>
values is
<code class="literal">
'-838:59:59.000000'
</code>
to
<code class="literal">
'838:59:59.000000'
</code>
.
</p>
<p>
Be careful about assigning abbreviated values to a
<code class="literal">
TIME
</code>
column. MySQL interprets abbreviated
<code class="literal">
TIME
</code>
values with colons as time of the day.
That is,
<code class="literal">
'11:12'
</code>
means
<code class="literal">
'11:12:00'
</code>
, not
<code class="literal">
'00:11:12'
</code>
. MySQL interprets abbreviated
values without colons using the assumption that the two
rightmost digits represent seconds (that is, as elapsed time
rather than as time of day). For example, you might think of
<code class="literal">
'1112'
</code>
and
<code class="literal">
1112
</code>
as meaning
<code class="literal">
'11:12:00'
</code>
(12 minutes after 11 o'clock), but
MySQL interprets them as
<code class="literal">
'00:11:12'
</code>
(11
minutes, 12 seconds). Similarly,
<code class="literal">
'12'
</code>
and
<code class="literal">
12
</code>
are interpreted as
<code class="literal">
'00:00:12'
</code>
.
</p>
<p>
The only delimiter recognized between a time part and a
fractional seconds part is the decimal point.
</p>
<p>
By default, values that lie outside the
<code class="literal">
TIME
</code>
range but are otherwise valid are clipped to the closest
endpoint of the range. For example,
<code class="literal">
'-850:00:00'
</code>
and
<code class="literal">
'850:00:00'
</code>
are converted to
<code class="literal">
'-838:59:59'
</code>
and
<code class="literal">
'838:59:59'
</code>
. Invalid
<code class="literal">
TIME
</code>
values are converted to
<code class="literal">
'00:00:00'
</code>
. Note that
because
<code class="literal">
'00:00:00'
</code>
is itself a valid
<code class="literal">
TIME
</code>
value, there is no way to tell, from a
value of
<code class="literal">
'00:00:00'
</code>
stored in a table,
whether the original value was specified as
<code class="literal">
'00:00:00'
</code>
or whether it was invalid.
</p>
<p>
For more restrictive treatment of invalid
<code class="literal">
TIME
</code>
values, enable strict SQL mode to cause
errors to occur. See
<a class="xref" href="sql-mode.html" title="7.1.11 Server SQL Modes">
Section 7.1.11, “Server SQL Modes”
</a>
.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/innodb-information-schema-fulltext_index-tables.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="innodb-information-schema-fulltext_index-tables">
</a>
17.15.4 InnoDB INFORMATION_SCHEMA FULLTEXT Index Tables
</h3>
</div>
</div>
</div>
<p>
The following tables provide metadata for
<code class="literal">
FULLTEXT
</code>
indexes:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa83221885"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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 operator">LIKE</span> <span class="token string">'INNODB_FT%'</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> Tables_in_INFORMATION_SCHEMA (INNODB_FT%) <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> INNODB_FT_CONFIG <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> INNODB_FT_BEING_DELETED <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> INNODB_FT_DELETED <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> INNODB_FT_DEFAULT_STOPWORD <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> INNODB_FT_INDEX_TABLE <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> INNODB_FT_INDEX_CACHE <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>
<div class="itemizedlist">
<h4>
<a name="idm46045150213744">
</a>
Table Overview
</h4>
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<a class="link" href="information-schema-innodb-ft-config-table.html" title="28.4.15 The INFORMATION_SCHEMA INNODB_FT_CONFIG Table">
<code class="literal">
INNODB_FT_CONFIG
</code>
</a>
: Provides
metadata about the
<code class="literal">
FULLTEXT
</code>
index and
associated processing for an
<code class="literal">
InnoDB
</code>
table.
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="information-schema-innodb-ft-being-deleted-table.html" title="28.4.14 The INFORMATION_SCHEMA INNODB_FT_BEING_DELETED Table">
<code class="literal">
INNODB_FT_BEING_DELETED
</code>
</a>
: Provides
a snapshot of the
<a class="link" href="information-schema-innodb-ft-deleted-table.html" title="28.4.17 The INFORMATION_SCHEMA INNODB_FT_DELETED Table">
<code class="literal">
INNODB_FT_DELETED
</code>
</a>
table; it is
used only during an
<a class="link" href="optimize-table.html" title="15.7.3.4 OPTIMIZE TABLE Statement">
<code class="literal">
OPTIMIZE
TABLE
</code>
</a>
maintenance operation. When
<a class="link" href="optimize-table.html" title="15.7.3.4 OPTIMIZE TABLE Statement">
<code class="literal">
OPTIMIZE TABLE
</code>
</a>
is run, the
<a class="link" href="information-schema-innodb-ft-being-deleted-table.html" title="28.4.14 The INFORMATION_SCHEMA INNODB_FT_BEING_DELETED Table">
<code class="literal">
INNODB_FT_BEING_DELETED
</code>
</a>
table is
emptied, and
<code class="literal">
DOC_ID
</code>
values are removed from
the
<a class="link" href="information-schema-innodb-ft-deleted-table.html" title="28.4.17 The INFORMATION_SCHEMA INNODB_FT_DELETED Table">
<code class="literal">
INNODB_FT_DELETED
</code>
</a>
table.
Because the contents of
<a class="link" href="information-schema-innodb-ft-being-deleted-table.html" title="28.4.14 The INFORMATION_SCHEMA INNODB_FT_BEING_DELETED Table">
<code class="literal">
INNODB_FT_BEING_DELETED
</code>
</a>
typically
have a short lifetime, this table has limited utility for
monitoring or debugging. For information about running
<a class="link" href="optimize-table.html" title="15.7.3.4 OPTIMIZE TABLE Statement">
<code class="literal">
OPTIMIZE TABLE
</code>
</a>
on tables with
<code class="literal">
FULLTEXT
</code>
indexes, see
<a class="xref" href="fulltext-fine-tuning.html" title="14.9.6 Fine-Tuning MySQL Full-Text Search">
Section 14.9.6, “Fine-Tuning MySQL Full-Text Search”
</a>
.
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="information-schema-innodb-ft-deleted-table.html" title="28.4.17 The INFORMATION_SCHEMA INNODB_FT_DELETED Table">
<code class="literal">
INNODB_FT_DELETED
</code>
</a>
: Stores rows
that are deleted from the
<code class="literal">
FULLTEXT
</code>
index
for an
<code class="literal">
InnoDB
</code>
table. To avoid expensive
index reorganization during DML operations for an
<code class="literal">
InnoDB
</code>
<code class="literal">
FULLTEXT
</code>
index,
the information about newly deleted words is stored
separately, filtered out of search results when you do a text
search, and removed from the main search index only when you
issue an
<a class="link" href="optimize-table.html" title="15.7.3.4 OPTIMIZE TABLE Statement">
<code class="literal">
OPTIMIZE TABLE
</code>
</a>
statement for the
<code class="literal">
InnoDB
</code>
table.
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="information-schema-innodb-ft-default-stopword-table.html" title="28.4.16 The INFORMATION_SCHEMA INNODB_FT_DEFAULT_STOPWORD Table">
<code class="literal">
INNODB_FT_DEFAULT_STOPWORD
</code>
</a>
: Holds
a list of
<a class="link" href="glossary.html#glos_stopword" title="stopword">
stopwords
</a>
that
are used by default when creating a
<code class="literal">
FULLTEXT
</code>
index on
<code class="literal">
InnoDB
</code>
tables.
</p>
<p>
For information about the
<a class="link" href="information-schema-innodb-ft-default-stopword-table.html" title="28.4.16 The INFORMATION_SCHEMA INNODB_FT_DEFAULT_STOPWORD Table">
<code class="literal">
INNODB_FT_DEFAULT_STOPWORD
</code>
</a>
table,
see
<a class="xref" href="fulltext-stopwords.html" title="14.9.4 Full-Text Stopwords">
Section 14.9.4, “Full-Text Stopwords”
</a>
.
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="information-schema-innodb-ft-index-table-table.html" title="28.4.19 The INFORMATION_SCHEMA INNODB_FT_INDEX_TABLE Table">
<code class="literal">
INNODB_FT_INDEX_TABLE
</code>
</a>
: Provides
information about the inverted index used to process text
searches against the
<code class="literal">
FULLTEXT
</code>
index of an
<code class="literal">
InnoDB
</code>
table.
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="information-schema-innodb-ft-index-cache-table.html" title="28.4.18 The INFORMATION_SCHEMA INNODB_FT_INDEX_CACHE Table">
<code class="literal">
INNODB_FT_INDEX_CACHE
</code>
</a>
: Provides
token information about newly inserted rows in a
<code class="literal">
FULLTEXT
</code>
index. To avoid expensive index
reorganization during DML operations, the information about
newly indexed words is stored separately, and combined with
the main search index only when
<a class="link" href="optimize-table.html" title="15.7.3.4 OPTIMIZE TABLE Statement">
<code class="literal">
OPTIMIZE
TABLE
</code>
</a>
is run, when the server is shut down, or when
the cache size exceeds a limit defined by the
<a class="link" href="innodb-parameters.html#sysvar_innodb_ft_cache_size">
<code class="literal">
innodb_ft_cache_size
</code>
</a>
or
<a class="link" href="innodb-parameters.html#sysvar_innodb_ft_total_cache_size">
<code class="literal">
innodb_ft_total_cache_size
</code>
</a>
system variable.
</p>
</li>
</ul>
</div>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
With the exception of the
<a class="link" href="information-schema-innodb-ft-default-stopword-table.html" title="28.4.16 The INFORMATION_SCHEMA INNODB_FT_DEFAULT_STOPWORD Table">
<code class="literal">
INNODB_FT_DEFAULT_STOPWORD
</code>
</a>
table,
these tables are empty initially. Before querying any of them,
set the value of the
<a class="link" href="innodb-parameters.html#sysvar_innodb_ft_aux_table">
<code class="literal">
innodb_ft_aux_table
</code>
</a>
system
variable to the name (including the database name) of the table
that contains the
<code class="literal">
FULLTEXT
</code>
index (for
example,
<code class="literal">
test/articles
</code>
).
</p>
</div>
<div class="example">
<a name="innodb-information-schema-fulltext-tables-example">
</a>
<p class="title">
<b>
Example 17.5 InnoDB FULLTEXT Index INFORMATION_SCHEMA Tables
</b>
</p>
<div class="example-contents">
<p>
This example uses a table with a
<code class="literal">
FULLTEXT
</code>
index to demonstrate the data contained in the
<code class="literal">
FULLTEXT
</code>
index
<code class="literal">
INFORMATION_SCHEMA
</code>
tables.
</p>
<div class="orderedlist">
<ol class="orderedlist" type="1">
<li class="listitem">
<p>
Create a table with a
<code class="literal">
FULLTEXT
</code>
index and
insert some data:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa91695256"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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> articles <span class="token punctuation">(</span>
id <span class="token datatype">INT</span> <span class="token keyword">UNSIGNED</span> <span class="token keyword">AUTO_INCREMENT</span> <span class="token operator">NOT</span> <span class="token boolean">NULL</span> <span class="token keyword">PRIMARY</span> <span class="token keyword">KEY</span><span class="token punctuation">,</span>
title <span class="token datatype">VARCHAR</span><span class="token punctuation">(</span><span class="token number">200</span><span class="token punctuation">)</span><span class="token punctuation">,</span>
body <span class="token datatype">TEXT</span><span class="token punctuation">,</span>
<span class="token keyword">FULLTEXT</span> <span class="token punctuation">(</span>title<span class="token punctuation">,</span>body<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 prompt">mysql></span> <span class="token keyword">INSERT</span> <span class="token keyword">INTO</span> articles <span class="token punctuation">(</span>title<span class="token punctuation">,</span>body<span class="token punctuation">)</span> <span class="token keyword">VALUES</span>
<span class="token punctuation">(</span><span class="token string">'MySQL Tutorial'</span><span class="token punctuation">,</span><span class="token string">'DBMS stands for DataBase ...'</span><span class="token punctuation">)</span><span class="token punctuation">,</span>
<span class="token punctuation">(</span><span class="token string">'How To Use MySQL Well'</span><span class="token punctuation">,</span><span class="token string">'After you went through a ...'</span><span class="token punctuation">)</span><span class="token punctuation">,</span>
<span class="token punctuation">(</span><span class="token string">'Optimizing MySQL'</span><span class="token punctuation">,</span><span class="token string">'In this tutorial we show ...'</span><span class="token punctuation">)</span><span class="token punctuation">,</span>
<span class="token punctuation">(</span><span class="token string">'1001 MySQL Tricks'</span><span class="token punctuation">,</span><span class="token string">'1. Never run mysqld as root. 2. ...'</span><span class="token punctuation">)</span><span class="token punctuation">,</span>
<span class="token punctuation">(</span><span class="token string">'MySQL vs. YourSQL'</span><span class="token punctuation">,</span><span class="token string">'In the following database comparison ...'</span><span class="token punctuation">)</span><span class="token punctuation">,</span>
<span class="token punctuation">(</span><span class="token string">'MySQL Security'</span><span class="token punctuation">,</span><span class="token string">'When configured properly, MySQL ...'</span><span class="token punctuation">)</span><span class="token punctuation">;</span></code></pre>
</div>
</li>
<li class="listitem">
<p>
Set the
<a class="link" href="innodb-parameters.html#sysvar_innodb_ft_aux_table">
<code class="literal">
innodb_ft_aux_table
</code>
</a>
variable to the name of the table with the
<code class="literal">
FULLTEXT
</code>
index. If this variable is not
set, the
<code class="literal">
InnoDB
</code>
<code class="literal">
FULLTEXT
</code>
<code class="literal">
INFORMATION_SCHEMA
</code>
tables are empty, with
the exception of
<a class="link" href="information-schema-innodb-ft-default-stopword-table.html" title="28.4.16 The INFORMATION_SCHEMA INNODB_FT_DEFAULT_STOPWORD Table">
<code class="literal">
INNODB_FT_DEFAULT_STOPWORD
</code>
</a>
.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa17056312"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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> innodb_ft_aux_table <span class="token operator">=</span> <span class="token string">'test/articles'</span><span class="token punctuation">;</span></code></pre>
</div>
</li>
<li class="listitem">
<p>
Query the
<a class="link" href="information-schema-innodb-ft-index-cache-table.html" title="28.4.18 The INFORMATION_SCHEMA INNODB_FT_INDEX_CACHE Table">
<code class="literal">
INNODB_FT_INDEX_CACHE
</code>
</a>
table, which shows information about newly inserted rows in
a
<code class="literal">
FULLTEXT
</code>
index. To avoid expensive
index reorganization during DML operations, data for newly
inserted rows remains in the
<code class="literal">
FULLTEXT
</code>
index cache until
<a class="link" href="optimize-table.html" title="15.7.3.4 OPTIMIZE TABLE Statement">
<code class="literal">
OPTIMIZE
TABLE
</code>
</a>
is run (or until the server is shut down or
cache limits are exceeded).
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa63771503"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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> INFORMATION_SCHEMA<span class="token punctuation">.</span>INNODB_FT_INDEX_CACHE <span class="token keyword">LIMIT</span> <span class="token number">5</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>
<span class="token output"><span class="token punctuation">|</span> WORD <span class="token punctuation">|</span> FIRST_DOC_ID <span class="token punctuation">|</span> LAST_DOC_ID <span class="token punctuation">|</span> DOC_COUNT <span class="token punctuation">|</span> DOC_ID <span class="token punctuation">|</span> POSITION <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>
<span class="token output"><span class="token punctuation">|</span> 1001 <span class="token punctuation">|</span> 5 <span class="token punctuation">|</span> 5 <span class="token punctuation">|</span> 1 <span class="token punctuation">|</span> 5 <span class="token punctuation">|</span> 0 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> after <span class="token punctuation">|</span> 3 <span class="token punctuation">|</span> 3 <span class="token punctuation">|</span> 1 <span class="token punctuation">|</span> 3 <span class="token punctuation">|</span> 22 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> comparison <span class="token punctuation">|</span> 6 <span class="token punctuation">|</span> 6 <span class="token punctuation">|</span> 1 <span class="token punctuation">|</span> 6 <span class="token punctuation">|</span> 44 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> configured <span class="token punctuation">|</span> 7 <span class="token punctuation">|</span> 7 <span class="token punctuation">|</span> 1 <span class="token punctuation">|</span> 7 <span class="token punctuation">|</span> 20 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> database <span class="token punctuation">|</span> 2 <span class="token punctuation">|</span> 6 <span class="token punctuation">|</span> 2 <span class="token punctuation">|</span> 2 <span class="token punctuation">|</span> 31 <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></code></pre>
</div>
</li>
<li class="listitem">
<p>
Enable the
<a class="link" href="innodb-parameters.html#sysvar_innodb_optimize_fulltext_only">
<code class="literal">
innodb_optimize_fulltext_only
</code>
</a>
system variable and run
<a class="link" href="optimize-table.html" title="15.7.3.4 OPTIMIZE TABLE Statement">
<code class="literal">
OPTIMIZE
TABLE
</code>
</a>
on the table that contains the
<code class="literal">
FULLTEXT
</code>
index. This operation flushes
the contents of the
<code class="literal">
FULLTEXT
</code>
index cache
to the main
<code class="literal">
FULLTEXT
</code>
index.
<a class="link" href="innodb-parameters.html#sysvar_innodb_optimize_fulltext_only">
<code class="literal">
innodb_optimize_fulltext_only
</code>
</a>
changes the way the
<a class="link" href="optimize-table.html" title="15.7.3.4 OPTIMIZE TABLE Statement">
<code class="literal">
OPTIMIZE
TABLE
</code>
</a>
statement operates on
<code class="literal">
InnoDB
</code>
tables, and is intended to be
enabled temporarily, during maintenance operations on
<code class="literal">
InnoDB
</code>
tables with
<code class="literal">
FULLTEXT
</code>
indexes.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa22326967"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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> innodb_optimize_fulltext_only<span class="token operator">=</span><span class="token keyword">ON</span><span class="token punctuation">;</span>
<span class="token prompt">mysql></span> <span class="token keyword">OPTIMIZE</span> <span class="token keyword">TABLE</span> articles<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>
<span class="token output"><span class="token punctuation">|</span> Table <span class="token punctuation">|</span> Op <span class="token punctuation">|</span> Msg_type <span class="token punctuation">|</span> Msg_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>
<span class="token output"><span class="token punctuation">|</span> test.articles <span class="token punctuation">|</span> optimize <span class="token punctuation">|</span> status <span class="token punctuation">|</span> OK <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></code></pre>
</div>
</li>
<li class="listitem">
<p>
Query the
<a class="link" href="information-schema-innodb-ft-index-table-table.html" title="28.4.19 The INFORMATION_SCHEMA INNODB_FT_INDEX_TABLE Table">
<code class="literal">
INNODB_FT_INDEX_TABLE
</code>
</a>
table to view information about data in the main
<code class="literal">
FULLTEXT
</code>
index, including information
about the data that was just flushed from the
<code class="literal">
FULLTEXT
</code>
index cache.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa2593835"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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> INFORMATION_SCHEMA<span class="token punctuation">.</span>INNODB_FT_INDEX_TABLE <span class="token keyword">LIMIT</span> <span class="token number">5</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>
<span class="token output"><span class="token punctuation">|</span> WORD <span class="token punctuation">|</span> FIRST_DOC_ID <span class="token punctuation">|</span> LAST_DOC_ID <span class="token punctuation">|</span> DOC_COUNT <span class="token punctuation">|</span> DOC_ID <span class="token punctuation">|</span> POSITION <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>
<span class="token output"><span class="token punctuation">|</span> 1001 <span class="token punctuation">|</span> 5 <span class="token punctuation">|</span> 5 <span class="token punctuation">|</span> 1 <span class="token punctuation">|</span> 5 <span class="token punctuation">|</span> 0 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> after <span class="token punctuation">|</span> 3 <span class="token punctuation">|</span> 3 <span class="token punctuation">|</span> 1 <span class="token punctuation">|</span> 3 <span class="token punctuation">|</span> 22 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> comparison <span class="token punctuation">|</span> 6 <span class="token punctuation">|</span> 6 <span class="token punctuation">|</span> 1 <span class="token punctuation">|</span> 6 <span class="token punctuation">|</span> 44 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> configured <span class="token punctuation">|</span> 7 <span class="token punctuation">|</span> 7 <span class="token punctuation">|</span> 1 <span class="token punctuation">|</span> 7 <span class="token punctuation">|</span> 20 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> database <span class="token punctuation">|</span> 2 <span class="token punctuation">|</span> 6 <span class="token punctuation">|</span> 2 <span class="token punctuation">|</span> 2 <span class="token punctuation">|</span> 31 <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></code></pre>
</div>
<p>
The
<a class="link" href="information-schema-innodb-ft-index-cache-table.html" title="28.4.18 The INFORMATION_SCHEMA INNODB_FT_INDEX_CACHE Table">
<code class="literal">
INNODB_FT_INDEX_CACHE
</code>
</a>
table
is now empty since the
<a class="link" href="optimize-table.html" title="15.7.3.4 OPTIMIZE TABLE Statement">
<code class="literal">
OPTIMIZE
TABLE
</code>
</a>
operation flushed the
<code class="literal">
FULLTEXT
</code>
index cache.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa32743793"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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> INFORMATION_SCHEMA<span class="token punctuation">.</span>INNODB_FT_INDEX_CACHE <span class="token keyword">LIMIT</span> <span class="token number">5</span><span class="token punctuation">;</span>
<span class="token output">Empty set (0.00 sec)</span></code></pre>
</div>
</li>
<li class="listitem">
<p>
Delete some records from the
<code class="literal">
test/articles
</code>
table.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa64850020"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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> test<span class="token punctuation">.</span>articles <span class="token keyword">WHERE</span> id <span class="token operator"><</span> <span class="token number">4</span><span class="token punctuation">;</span></code></pre>
</div>
</li>
<li class="listitem">
<p>
Query the
<a class="link" href="information-schema-innodb-ft-deleted-table.html" title="28.4.17 The INFORMATION_SCHEMA INNODB_FT_DELETED Table">
<code class="literal">
INNODB_FT_DELETED
</code>
</a>
table. This table records rows that are deleted from the
<code class="literal">
FULLTEXT
</code>
index. To avoid expensive index
reorganization during DML operations, information about
newly deleted records is stored separately, filtered out of
search results when you do a text search, and removed from
the main search index when you run
<a class="link" href="optimize-table.html" title="15.7.3.4 OPTIMIZE TABLE Statement">
<code class="literal">
OPTIMIZE TABLE
</code>
</a>
.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa82002594"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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> INFORMATION_SCHEMA<span class="token punctuation">.</span>INNODB_FT_DELETED<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>
<span class="token output"><span class="token punctuation">|</span> DOC_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>
<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> 3 <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></code></pre>
</div>
</li>
<li class="listitem">
<p>
Run
<a class="link" href="optimize-table.html" title="15.7.3.4 OPTIMIZE TABLE Statement">
<code class="literal">
OPTIMIZE TABLE
</code>
</a>
to remove
the deleted records.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa52623236"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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">OPTIMIZE</span> <span class="token keyword">TABLE</span> articles<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>
<span class="token output"><span class="token punctuation">|</span> Table <span class="token punctuation">|</span> Op <span class="token punctuation">|</span> Msg_type <span class="token punctuation">|</span> Msg_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>
<span class="token output"><span class="token punctuation">|</span> test.articles <span class="token punctuation">|</span> optimize <span class="token punctuation">|</span> status <span class="token punctuation">|</span> OK <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></code></pre>
</div>
<p>
The
<a class="link" href="information-schema-innodb-ft-deleted-table.html" title="28.4.17 The INFORMATION_SCHEMA INNODB_FT_DELETED Table">
<code class="literal">
INNODB_FT_DELETED
</code>
</a>
table
should now be empty.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa3578608"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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> INFORMATION_SCHEMA<span class="token punctuation">.</span>INNODB_FT_DELETED<span class="token punctuation">;</span>
<span class="token output">Empty set (0.00 sec)</span></code></pre>
</div>
</li>
<li class="listitem">
<p>
Query the
<a class="link" href="information-schema-innodb-ft-config-table.html" title="28.4.15 The INFORMATION_SCHEMA INNODB_FT_CONFIG Table">
<code class="literal">
INNODB_FT_CONFIG
</code>
</a>
table. This table contains metadata about the
<code class="literal">
FULLTEXT
</code>
index and related processing:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<code class="literal">
optimize_checkpoint_limit
</code>
: The number
of seconds after which an
<a class="link" href="optimize-table.html" title="15.7.3.4 OPTIMIZE TABLE Statement">
<code class="literal">
OPTIMIZE
TABLE
</code>
</a>
run stops.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
synced_doc_id
</code>
: The next
<code class="literal">
DOC_ID
</code>
to be issued.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
stopword_table_name
</code>
: The
<em class="replaceable">
<code>
database/table
</code>
</em>
name for a
user-defined stopword table. The
<code class="literal">
VALUE
</code>
column is empty if there is no
user-defined stopword table.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
use_stopword
</code>
: Indicates whether a
stopword table is used, which is defined when the
<code class="literal">
FULLTEXT
</code>
index is created.
</p>
</li>
</ul>
</div>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa27502308"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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> INFORMATION_SCHEMA<span class="token punctuation">.</span>INNODB_FT_CONFIG<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> KEY <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>
<span class="token output"><span class="token punctuation">|</span> optimize_checkpoint_limit <span class="token punctuation">|</span> 180 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> synced_doc_id <span class="token punctuation">|</span> 8 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> stopword_table_name <span class="token punctuation">|</span> <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> use_stopword <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></code></pre>
</div>
</li>
<li class="listitem">
<p>
Disable
<a class="link" href="innodb-parameters.html#sysvar_innodb_optimize_fulltext_only">
<code class="literal">
innodb_optimize_fulltext_only
</code>
</a>
,
since it is intended to be enabled only temporarily:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa43251695"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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> innodb_optimize_fulltext_only<span class="token operator">=</span><span class="token keyword">OFF</span><span class="token punctuation">;</span></code></pre>
</div>
</li>
</ol>
</div>
</div>
</div>
<br class="example-break"/>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/data-size.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="data-size">
</a>
10.4.1 Optimizing Data Size
</h3>
</div>
</div>
</div>
<a class="indexterm" name="idm46045226859168">
</a>
<a class="indexterm" name="idm46045226857680">
</a>
<a class="indexterm" name="idm46045226856192">
</a>
<a class="indexterm" name="idm46045226854704">
</a>
<a class="indexterm" name="idm46045226853216">
</a>
<p>
Design your tables to minimize their space on the disk. This can
result in huge improvements by reducing the amount of data
written to and read from disk. Smaller tables normally require
less main memory while their contents are being actively
processed during query execution. Any space reduction for table
data also results in smaller indexes that can be processed
faster.
</p>
<p>
MySQL supports many different storage engines (table types) and
row formats. For each table, you can decide which storage and
indexing method to use. Choosing the proper table format for
your application can give you a big performance gain. 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>
, and
<a class="xref" href="storage-engines.html" title="Chapter 18 Alternative Storage Engines">
Chapter 18,
<i>
Alternative Storage Engines
</i>
</a>
.
</p>
<p>
You can get better performance for a table and minimize storage
space by using the techniques listed here:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<a class="xref" href="data-size.html#data-size-table-columns" title="Table Columns">
Table Columns
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="data-size.html#data-size-row-format" title="Row Format">
Row Format
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="data-size.html#data-size-indexes" title="Indexes">
Indexes
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="data-size.html#data-size-joins" title="Joins">
Joins
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="data-size.html#data-size-normalization" title="Normalization">
Normalization
</a>
</p>
</li>
</ul>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h4 class="title">
<a name="data-size-table-columns">
</a>
Table Columns
</h4>
</div>
</div>
</div>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
Use the most efficient (smallest) data types possible.
MySQL has many specialized types that save disk space and
memory. For example, use the smaller integer types if
possible to get smaller tables.
<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>
is often a better
choice than
<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>
because 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">
MEDIUMINT
</code>
</a>
column uses 25%
less space.
</p>
</li>
<li class="listitem">
<p>
Declare columns to be
<code class="literal">
NOT NULL
</code>
if
possible. It makes SQL operations faster, by enabling
better use of indexes and eliminating overhead for testing
whether each value is
<code class="literal">
NULL
</code>
. You also
save some storage space, one bit per column. If you really
need
<code class="literal">
NULL
</code>
values in your tables, use
them. Just avoid the default setting that allows
<code class="literal">
NULL
</code>
values in every column.
</p>
</li>
</ul>
</div>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h4 class="title">
<a name="data-size-row-format">
</a>
Row Format
</h4>
</div>
</div>
</div>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<code class="literal">
InnoDB
</code>
tables are created using the
<code class="literal">
DYNAMIC
</code>
row format by default. To use a
row format other than
<code class="literal">
DYNAMIC
</code>
,
configure
<a class="link" href="innodb-parameters.html#sysvar_innodb_default_row_format">
<code class="literal">
innodb_default_row_format
</code>
</a>
,
or specify the
<code class="literal">
ROW_FORMAT
</code>
option
explicitly in a
<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="alter-table.html" title="15.1.9 ALTER TABLE Statement">
<code class="literal">
ALTER
TABLE
</code>
</a>
statement.
</p>
<p>
The compact family of row formats, which includes
<code class="literal">
COMPACT
</code>
,
<code class="literal">
DYNAMIC
</code>
,
and
<code class="literal">
COMPRESSED
</code>
, decreases row storage
space at the cost of increasing CPU use for some
operations. If your workload is a typical one that is
limited by cache hit rates and disk speed it is likely to
be faster. If it is a rare case that is limited by CPU
speed, it might be slower.
</p>
<p>
The compact family of row formats also optimizes
<a class="link" href="char.html" title="13.3.2 The CHAR and VARCHAR Types">
<code class="literal">
CHAR
</code>
</a>
column storage when
using a variable-length character set such as
<code class="literal">
utf8mb3
</code>
or
<code class="literal">
utf8mb4
</code>
.
With
<code class="literal">
ROW_FORMAT=REDUNDANT
</code>
,
<code class="literal">
CHAR(
<em class="replaceable">
<code>
N
</code>
</em>
)
</code>
occupies
<em class="replaceable">
<code>
N
</code>
</em>
× the maximum
byte length of the character set. Many languages can be
written primarily using single-byte
<code class="literal">
utf8mb3
</code>
or
<code class="literal">
utf8mb4
</code>
characters, so a fixed storage length often wastes space.
With the compact family of rows formats,
<code class="literal">
InnoDB
</code>
allocates a variable amount of
storage in the range of
<em class="replaceable">
<code>
N
</code>
</em>
to
<em class="replaceable">
<code>
N
</code>
</em>
× the maximum byte
length of the character set for these columns by stripping
trailing spaces. The minimum storage length is
<em class="replaceable">
<code>
N
</code>
</em>
bytes to facilitate in-place
updates in typical cases. For more information, 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>
To minimize space even further by storing table data in
compressed form, specify
<code class="literal">
ROW_FORMAT=COMPRESSED
</code>
when creating
<code class="literal">
InnoDB
</code>
tables, or run the
<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>
command on an existing
<code class="literal">
MyISAM
</code>
table.
(
<code class="literal">
InnoDB
</code>
compressed tables are readable
and writable, while
<code class="literal">
MyISAM
</code>
compressed
tables are read-only.)
</p>
</li>
<li class="listitem">
<p>
For
<code class="literal">
MyISAM
</code>
tables, if you do not have
any variable-length columns
(
<a class="link" href="char.html" title="13.3.2 The CHAR and VARCHAR Types">
<code class="literal">
VARCHAR
</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="blob.html" title="13.3.4 The BLOB and TEXT Types">
<code class="literal">
BLOB
</code>
</a>
columns), a fixed-size
row format is used. This is faster but may waste some
space. 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>
. You can
hint that you want to have fixed length rows even if you
have
<a class="link" href="char.html" title="13.3.2 The CHAR and VARCHAR Types">
<code class="literal">
VARCHAR
</code>
</a>
columns with
the
<a class="link" href="create-table.html" title="15.1.20 CREATE TABLE Statement">
<code class="literal">
CREATE TABLE
</code>
</a>
option
<code class="literal">
ROW_FORMAT=FIXED
</code>
.
</p>
</li>
</ul>
</div>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h4 class="title">
<a name="data-size-indexes">
</a>
Indexes
</h4>
</div>
</div>
</div>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
The primary index of a table should be as short as
possible. This makes identification of each row easy and
efficient. For
<code class="literal">
InnoDB
</code>
tables, the
primary key columns are duplicated in each secondary index
entry, so a short primary key saves considerable space if
you have many secondary indexes.
</p>
</li>
<li class="listitem">
<p>
Create only the indexes that you need to improve query
performance. Indexes are good for retrieval, but slow down
insert and update operations. If you access a table mostly
by searching on a combination of columns, create a single
composite index on them rather than a separate index for
each column. The first part of the index should be the
column most used. If you
<span class="emphasis">
<em>
always
</em>
</span>
use
many columns when selecting from the table, the first
column in the index should be the one with the most
duplicates, to obtain better compression of the index.
</p>
</li>
<li class="listitem">
<p>
If it is very likely that a long string column has a
unique prefix on the first number of characters, it is
better to index only this prefix, using MySQL's
support for creating an index on the leftmost part of the
column (see
<a class="xref" href="create-index.html" title="15.1.15 CREATE INDEX Statement">
Section 15.1.15, “CREATE INDEX Statement”
</a>
). Shorter
indexes are faster, not only because they require less
disk space, but because they also give you more hits in
the index cache, and thus fewer disk seeks. See
<a class="xref" href="server-configuration.html" title="7.1.1 Configuring the Server">
Section 7.1.1, “Configuring the Server”
</a>
.
</p>
</li>
</ul>
</div>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h4 class="title">
<a name="data-size-joins">
</a>
Joins
</h4>
</div>
</div>
</div>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
In some circumstances, it can be beneficial to split into
two a table that is scanned very often. This is especially
true if it is a dynamic-format table and it is possible to
use a smaller static format table that can be used to find
the relevant rows when scanning the table.
</p>
</li>
<li class="listitem">
<p>
Declare columns with identical information in different
tables with identical data types, to speed up joins based
on the corresponding columns.
</p>
</li>
<li class="listitem">
<p>
Keep column names simple, so that you can use the same
name across different tables and simplify join queries.
For example, in a table named
<code class="literal">
customer
</code>
,
use a column name of
<code class="literal">
name
</code>
instead of
<code class="literal">
customer_name
</code>
. To make your names
portable to other SQL servers, consider keeping them
shorter than 18 characters.
</p>
</li>
</ul>
</div>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h4 class="title">
<a name="data-size-normalization">
</a>
Normalization
</h4>
</div>
</div>
</div>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
Normally, try to keep all data nonredundant (observing
what is referred to in database theory as
<span class="firstterm">
third normal form
</span>
).
Instead of repeating lengthy values such as names and
addresses, assign them unique IDs, repeat these IDs as
needed across multiple smaller tables, and join the tables
in queries by referencing the IDs in the join clause.
</p>
</li>
<li class="listitem">
<p>
If speed is more important than disk space and the
maintenance costs of keeping multiple copies of data, for
example in a business intelligence scenario where you
analyze all the data from large tables, you can relax the
normalization rules, duplicating information or creating
summary tables to gain more speed.
</p>
</li>
</ul>
</div>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/enterprise-encryption-function-reference.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="enterprise-encryption-function-reference">
</a>
8.6.4 MySQL Enterprise Encryption Function Reference
</h3>
</div>
</div>
</div>
<p>
MySQL Enterprise Encryption functions are provided by the MySQL
<code class="literal">
component_enterprise_encryption
</code>
component. See
<a class="xref" href="enterprise-encryption-functions.html" title="8.6.5 MySQL Enterprise Encryption Component Function Descriptions">
Section 8.6.5, “MySQL Enterprise Encryption Component Function Descriptions”
</a>
.
</p>
<div class="table">
<a name="idm46045231888896">
</a>
<p class="title">
<b>
Table 8.48 MySQL Enterprise Encryption Functions
</b>
</p>
<div class="table-contents">
<table frame="box" rules="all" summary="A reference that lists MySQL Enterprise Encryption 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="enterprise-encryption-functions.html#function_asymmetric-decrypt">
<code class="literal">
asymmetric_decrypt()
</code>
</a>
</td>
<td>
Decrypt ciphertext using private or public key
</td>
</tr>
<tr>
<td>
<code class="literal">
asymmetric_derive()
</code>
</td>
<td>
Derive symmetric key from asymmetric keys
</td>
</tr>
<tr>
<td>
<a class="link" href="enterprise-encryption-functions.html#function_asymmetric-encrypt">
<code class="literal">
asymmetric_encrypt()
</code>
</a>
</td>
<td>
Encrypt cleartext using private or public key
</td>
</tr>
<tr>
<td>
<a class="link" href="enterprise-encryption-functions.html#function_asymmetric-sign">
<code class="literal">
asymmetric_sign()
</code>
</a>
</td>
<td>
Generate signature from digest
</td>
</tr>
<tr>
<td>
<a class="link" href="enterprise-encryption-functions.html#function_asymmetric-verify">
<code class="literal">
asymmetric_verify()
</code>
</a>
</td>
<td>
Verify that signature matches digest
</td>
</tr>
<tr>
<td>
<a class="link" href="enterprise-encryption-functions.html#function_create-asymmetric-priv-key">
<code class="literal">
create_asymmetric_priv_key()
</code>
</a>
</td>
<td>
Create private key
</td>
</tr>
<tr>
<td>
<a class="link" href="enterprise-encryption-functions.html#function_create-asymmetric-pub-key">
<code class="literal">
create_asymmetric_pub_key()
</code>
</a>
</td>
<td>
Create public key
</td>
</tr>
<tr>
<td>
<code class="literal">
create_dh_parameters()
</code>
</td>
<td>
Generate shared DH secret
</td>
</tr>
<tr>
<td>
<a class="link" href="enterprise-encryption-functions.html#function_create-digest">
<code class="literal">
create_digest()
</code>
</a>
</td>
<td>
Generate digest from string
</td>
</tr>
</tbody>
</table>
</div>
</div>
<br class="table-break"/>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/kill.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="kill">
</a>
15.7.8.4 KILL Statement
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045168490544">
</a>
<a class="indexterm" name="idm46045168489472">
</a>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa88244701"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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">KILL</span> <span class="token punctuation">[</span><span class="token keyword">CONNECTION</span> <span class="token operator">|</span> <span class="token keyword">QUERY</span><span class="token punctuation">]</span> <em class="replaceable">processlist_id</em></code></pre>
</div>
<p>
Each connection to
<a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
<span class="command">
<strong>
mysqld
</strong>
</span>
</a>
runs in a separate
thread. You can kill a thread with the
<code class="literal">
KILL
<em class="replaceable">
<code>
processlist_id
</code>
</em>
</code>
statement.
</p>
<p>
Thread processlist identifiers can be determined from the
<code class="literal">
ID
</code>
column of the
<code class="literal">
INFORMATION_SCHEMA
</code>
<a class="link" href="information-schema-processlist-table.html" title="28.3.23 The INFORMATION_SCHEMA PROCESSLIST Table">
<code class="literal">
PROCESSLIST
</code>
</a>
table, the
<code class="literal">
Id
</code>
column of
<a class="link" href="show-processlist.html" title="15.7.7.31 SHOW PROCESSLIST Statement">
<code class="literal">
SHOW
PROCESSLIST
</code>
</a>
output, and the
<code class="literal">
PROCESSLIST_ID
</code>
column of the Performance
Schema
<a class="link" href="performance-schema-threads-table.html" title="29.12.22.8 The threads Table">
<code class="literal">
threads
</code>
</a>
table. The value for
the current thread is returned by the
<a class="link" href="information-functions.html#function_connection-id">
<code class="literal">
CONNECTION_ID()
</code>
</a>
function.
</p>
<p>
<a class="link" href="kill.html" title="15.7.8.4 KILL Statement">
<code class="literal">
KILL
</code>
</a>
permits an optional
<code class="literal">
CONNECTION
</code>
or
<code class="literal">
QUERY
</code>
modifier:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<a class="link" href="kill.html" title="15.7.8.4 KILL Statement">
<code class="literal">
KILL
CONNECTION
</code>
</a>
is the same as
<a class="link" href="kill.html" title="15.7.8.4 KILL Statement">
<code class="literal">
KILL
</code>
</a>
with no modifier: It
terminates the connection associated with the given
<em class="replaceable">
<code>
processlist_id
</code>
</em>
, after terminating
any statement the connection is executing.
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="kill.html" title="15.7.8.4 KILL Statement">
<code class="literal">
KILL QUERY
</code>
</a>
terminates the statement the connection is currently
executing, but leaves the connection itself intact.
</p>
</li>
</ul>
</div>
<p>
The ability to see which threads are available to be killed
depends on the
<a class="link" href="privileges-provided.html#priv_process">
<code class="literal">
PROCESS
</code>
</a>
privilege:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
Without
<a class="link" href="privileges-provided.html#priv_process">
<code class="literal">
PROCESS
</code>
</a>
, you can see
only your own threads.
</p>
</li>
<li class="listitem">
<p>
With
<a class="link" href="privileges-provided.html#priv_process">
<code class="literal">
PROCESS
</code>
</a>
, you can see all
threads.
</p>
</li>
</ul>
</div>
<p>
The ability to kill threads and statements depends on the
<a class="link" href="privileges-provided.html#priv_connection-admin">
<code class="literal">
CONNECTION_ADMIN
</code>
</a>
privilege and
the deprecated
<a class="link" href="privileges-provided.html#priv_super">
<code class="literal">
SUPER
</code>
</a>
privilege:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
Without
<a class="link" href="privileges-provided.html#priv_connection-admin">
<code class="literal">
CONNECTION_ADMIN
</code>
</a>
or
<a class="link" href="privileges-provided.html#priv_super">
<code class="literal">
SUPER
</code>
</a>
, you can kill only your
own threads and statements.
</p>
</li>
<li class="listitem">
<p>
With
<a class="link" href="privileges-provided.html#priv_connection-admin">
<code class="literal">
CONNECTION_ADMIN
</code>
</a>
or
<a class="link" href="privileges-provided.html#priv_super">
<code class="literal">
SUPER
</code>
</a>
, you can kill all
threads and statements, except that to affect a thread or
statement that is executing with the
<a class="link" href="privileges-provided.html#priv_system-user">
<code class="literal">
SYSTEM_USER
</code>
</a>
privilege, your
own session must additionally have the
<a class="link" href="privileges-provided.html#priv_system-user">
<code class="literal">
SYSTEM_USER
</code>
</a>
privilege.
</p>
</li>
</ul>
</div>
<p>
You can also use the
<a class="link" href="mysqladmin.html" title="6.5.2 mysqladmin — A MySQL Server Administration Program">
<span class="command">
<strong>
mysqladmin processlist
</strong>
</span>
</a>
and
<a class="link" href="mysqladmin.html" title="6.5.2 mysqladmin — A MySQL Server Administration Program">
<span class="command">
<strong>
mysqladmin kill
</strong>
</span>
</a>
commands to examine and
kill threads.
</p>
<p>
When you use
<a class="link" href="kill.html" title="15.7.8.4 KILL Statement">
<code class="literal">
KILL
</code>
</a>
, a
thread-specific kill flag is set for the thread. In most cases,
it might take some time for the thread to die because the kill
flag is checked only at specific intervals:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
During
<a class="link" href="select.html" title="15.2.13 SELECT Statement">
<code class="literal">
SELECT
</code>
</a>
operations, for
<code class="literal">
ORDER BY
</code>
and
<code class="literal">
GROUP BY
</code>
loops, the flag is checked after reading a block of rows. If
the kill flag is set, the statement is aborted.
</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>
operations that
make a table copy check the kill flag periodically for each
few copied rows read from the original table. If the kill
flag was set, the statement is aborted and the temporary
table is deleted.
</p>
<p>
The
<a class="link" href="kill.html" title="15.7.8.4 KILL Statement">
<code class="literal">
KILL
</code>
</a>
statement returns
without waiting for confirmation, but the kill flag check
aborts the operation within a reasonably small amount of
time. Aborting the operation to perform any necessary
cleanup also takes some time.
</p>
</li>
<li class="listitem">
<p>
During
<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>
operations, the kill
flag is checked after each block read and after each updated
or deleted row. If the kill flag is set, the statement is
aborted. If you are not using transactions, the changes are
not rolled back.
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="locking-functions.html#function_get-lock">
<code class="literal">
GET_LOCK()
</code>
</a>
aborts and returns
<code class="literal">
NULL
</code>
.
</p>
</li>
<li class="listitem">
<p>
If the thread is in the table lock handler (state:
<code class="literal">
Locked
</code>
), the table lock is quickly
aborted.
</p>
</li>
<li class="listitem">
<p>
If the thread is waiting for free disk space in a write
call, the write is aborted with a
<span class="quote">
“
<span class="quote">
disk full
</span>
”
</span>
error message.
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="explain.html#explain-analyze" title="Obtaining Information with EXPLAIN ANALYZE">
<code class="literal">
EXPLAIN ANALYZE
</code>
</a>
aborts and
prints the first row of output.
</p>
</li>
</ul>
</div>
<div class="warning" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Warning
</div>
<p>
Killing a
<a class="link" href="repair-table.html" title="15.7.3.5 REPAIR TABLE Statement">
<code class="literal">
REPAIR TABLE
</code>
</a>
or
<a class="link" href="optimize-table.html" title="15.7.3.4 OPTIMIZE TABLE Statement">
<code class="literal">
OPTIMIZE TABLE
</code>
</a>
operation on a
<code class="literal">
MyISAM
</code>
table results in a table that is
corrupted and unusable. Any reads or writes to such a table
fail until you optimize or repair it again (without
interruption).
</p>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/faqs-triggers.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h2 class="title">
<a name="faqs-triggers">
</a>
A.5 MySQL 8.4 FAQ: Triggers
</h2>
</div>
</div>
</div>
<div class="qandaset">
<a name="idm46045056252976">
</a>
<dl>
<dt>
A.5.1.
<a href="faqs-triggers.html#faq-mysql-where-triggers-docs">
Where can I find the documentation for MySQL 8.4
triggers?
</a>
</dt>
<dt>
A.5.2.
<a href="faqs-triggers.html#faq-mysql-where-triggers-forum">
Is there a discussion forum for MySQL Triggers?
</a>
</dt>
<dt>
A.5.3.
<a href="faqs-triggers.html#faq-mysql-have-trigger-levels">
Does MySQL have statement-level or row-level triggers?
</a>
</dt>
<dt>
A.5.4.
<a href="faqs-triggers.html#faq-mysql-have-trigger-defaults">
Are there any default triggers?
</a>
</dt>
<dt>
A.5.5.
<a href="faqs-triggers.html#faq-mysql-how-triggers-managed">
How are triggers managed in MySQL?
</a>
</dt>
<dt>
A.5.6.
<a href="faqs-triggers.html#faq-mysql-can-view-all-triggers">
Is there a way to view all triggers in a given database?
</a>
</dt>
<dt>
A.5.7.
<a href="faqs-triggers.html#faq-mysql-how-triggers-stored">
Where are triggers stored?
</a>
</dt>
<dt>
A.5.8.
<a href="faqs-triggers.html#faq-mysql-can-trigger-procedure">
Can a trigger call a stored procedure?
</a>
</dt>
<dt>
A.5.9.
<a href="faqs-triggers.html#faq-mysql-can-triggers-tables">
Can triggers access tables?
</a>
</dt>
<dt>
A.5.10.
<a href="faqs-triggers.html#faq-mysql-can-triggers-same-events">
Can a table have multiple triggers with the same trigger event
and action time?
</a>
</dt>
<dt>
A.5.11.
<a href="faqs-triggers.html#faq-mysql-can-triggers-remote">
Is it possible for a trigger to update tables on a remote
server?
</a>
</dt>
<dt>
A.5.12.
<a href="faqs-triggers.html#faq-mysql-can-triggers-replication">
Do triggers work with replication?
</a>
</dt>
<dt>
A.5.13.
<a href="faqs-triggers.html#faq-mysql-how-triggers-source-replica">
How are actions carried out through triggers on a source
replicated to a replica?
</a>
</dt>
</dl>
<table border="0" style="width: 100%;">
<colgroup>
<col align="left" width="1%"/>
<col/>
</colgroup>
<tbody>
<tr class="question">
<td align="left" valign="top">
<a name="faq-mysql-where-triggers-docs">
</a>
<a name="idm46045056252224">
</a>
<p>
<b>
A.5.1.
</b>
</p>
</td>
<td align="left" valign="top">
<p>
Where can I find the documentation for MySQL 8.4
triggers?
</p>
</td>
</tr>
<tr class="answer">
<td align="left" valign="top">
</td>
<td align="left" valign="top">
<p>
See
<a class="xref" href="triggers.html" title="27.3 Using Triggers">
Section 27.3, “Using Triggers”
</a>
.
</p>
</td>
</tr>
<tr class="question">
<td align="left" valign="top">
<a name="faq-mysql-where-triggers-forum">
</a>
<a name="idm46045056249568">
</a>
<p>
<b>
A.5.2.
</b>
</p>
</td>
<td align="left" valign="top">
<p>
Is there a discussion forum for MySQL Triggers?
</p>
</td>
</tr>
<tr class="answer">
<td align="left" valign="top">
</td>
<td align="left" valign="top">
<p>
Yes. It is available at
<a class="ulink" href="https://forums.mysql.com/list.php?99" target="_blank">
https://forums.mysql.com/list.php?99
</a>
.
</p>
</td>
</tr>
<tr class="question">
<td align="left" valign="top">
<a name="faq-mysql-have-trigger-levels">
</a>
<a name="idm46045056247008">
</a>
<p>
<b>
A.5.3.
</b>
</p>
</td>
<td align="left" valign="top">
<p>
Does MySQL have statement-level or row-level triggers?
</p>
</td>
</tr>
<tr class="answer">
<td align="left" valign="top">
</td>
<td align="left" valign="top">
<p>
All triggers are
<code class="literal">
FOR EACH ROW
</code>
; that is, the
trigger is activated for each row that is inserted, updated, or
deleted. MySQL does not support triggers using
<code class="literal">
FOR EACH
STATEMENT
</code>
.
</p>
</td>
</tr>
<tr class="question">
<td align="left" valign="top">
<a name="faq-mysql-have-trigger-defaults">
</a>
<a name="idm46045056243376">
</a>
<p>
<b>
A.5.4.
</b>
</p>
</td>
<td align="left" valign="top">
<p>
Are there any default triggers?
</p>
</td>
</tr>
<tr class="answer">
<td align="left" valign="top">
</td>
<td align="left" valign="top">
<p>
Not explicitly. MySQL does have specific special behavior for
some
<a class="link" href="datetime.html" title="13.2.2 The DATE, DATETIME, and TIMESTAMP Types">
<code class="literal">
TIMESTAMP
</code>
</a>
columns, as well
as for columns which are defined using
<code class="literal">
AUTO_INCREMENT
</code>
.
</p>
</td>
</tr>
<tr class="question">
<td align="left" valign="top">
<a name="faq-mysql-how-triggers-managed">
</a>
<a name="idm46045056239344">
</a>
<p>
<b>
A.5.5.
</b>
</p>
</td>
<td align="left" valign="top">
<p>
How are triggers managed in MySQL?
</p>
</td>
</tr>
<tr class="answer">
<td align="left" valign="top">
</td>
<td align="left" valign="top">
<p>
Triggers can be created using the
<a class="link" href="create-trigger.html" title="15.1.22 CREATE TRIGGER Statement">
<code class="literal">
CREATE
TRIGGER
</code>
</a>
statement, and dropped using
<a class="link" href="drop-trigger.html" title="15.1.34 DROP TRIGGER Statement">
<code class="literal">
DROP TRIGGER
</code>
</a>
. See
<a class="xref" href="create-trigger.html" title="15.1.22 CREATE TRIGGER Statement">
Section 15.1.22, “CREATE TRIGGER Statement”
</a>
, and
<a class="xref" href="drop-trigger.html" title="15.1.34 DROP TRIGGER Statement">
Section 15.1.34, “DROP TRIGGER Statement”
</a>
, for more about these statements.
</p>
<p>
Information about triggers can be obtained by querying the
<a class="link" href="information-schema-triggers-table.html" title="28.3.44 The INFORMATION_SCHEMA TRIGGERS Table">
<code class="literal">
INFORMATION_SCHEMA.TRIGGERS
</code>
</a>
table.
See
<a class="xref" href="information-schema-triggers-table.html" title="28.3.44 The INFORMATION_SCHEMA TRIGGERS Table">
Section 28.3.44, “The INFORMATION_SCHEMA TRIGGERS Table”
</a>
.
</p>
</td>
</tr>
<tr class="question">
<td align="left" valign="top">
<a name="faq-mysql-can-view-all-triggers">
</a>
<a name="idm46045056230976">
</a>
<p>
<b>
A.5.6.
</b>
</p>
</td>
<td align="left" valign="top">
<p>
Is there a way to view all triggers in a given database?
</p>
</td>
</tr>
<tr class="answer">
<td align="left" valign="top">
</td>
<td align="left" valign="top">
<p>
Yes. You can obtain a listing of all triggers defined on
database
<code class="literal">
dbname
</code>
using a query on the
<a class="link" href="information-schema-triggers-table.html" title="28.3.44 The INFORMATION_SCHEMA TRIGGERS Table">
<code class="literal">
INFORMATION_SCHEMA.TRIGGERS
</code>
</a>
table
such as the one shown here:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa63395923"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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> TRIGGER_NAME<span class="token punctuation">,</span> EVENT_MANIPULATION<span class="token punctuation">,</span> EVENT_OBJECT_TABLE<span class="token punctuation">,</span> ACTION_STATEMENT
<span class="token keyword">FROM</span> INFORMATION_SCHEMA<span class="token punctuation">.</span><span class="token keyword">TRIGGERS</span>
<span class="token keyword">WHERE</span> TRIGGER_SCHEMA<span class="token operator">=</span><span class="token string">'<em class="replaceable">dbname</em>'</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
For more information about this table, see
<a class="xref" href="information-schema-triggers-table.html" title="28.3.44 The INFORMATION_SCHEMA TRIGGERS Table">
Section 28.3.44, “The INFORMATION_SCHEMA TRIGGERS Table”
</a>
.
</p>
<p>
You can also use the
<a class="link" href="show-triggers.html" title="15.7.7.40 SHOW TRIGGERS Statement">
<code class="literal">
SHOW
TRIGGERS
</code>
</a>
statement, which is specific to MySQL. See
<a class="xref" href="show-triggers.html" title="15.7.7.40 SHOW TRIGGERS Statement">
Section 15.7.7.40, “SHOW TRIGGERS Statement”
</a>
.
</p>
</td>
</tr>
<tr class="question">
<td align="left" valign="top">
<a name="faq-mysql-how-triggers-stored">
</a>
<a name="idm46045056221808">
</a>
<p>
<b>
A.5.7.
</b>
</p>
</td>
<td align="left" valign="top">
<p>
Where are triggers stored?
</p>
</td>
</tr>
<tr class="answer">
<td align="left" valign="top">
</td>
<td align="left" valign="top">
<p>
Triggers are stored in the
<code class="literal">
mysql.triggers
</code>
system table, which is part of the data dictionary.
</p>
</td>
</tr>
<tr class="question">
<td align="left" valign="top">
<a name="faq-mysql-can-trigger-procedure">
</a>
<a name="idm46045056219008">
</a>
<p>
<b>
A.5.8.
</b>
</p>
</td>
<td align="left" valign="top">
<p>
Can a trigger call a stored procedure?
</p>
</td>
</tr>
<tr class="answer">
<td align="left" valign="top">
</td>
<td align="left" valign="top">
<p>
Yes.
</p>
</td>
</tr>
<tr class="question">
<td align="left" valign="top">
<a name="faq-mysql-can-triggers-tables">
</a>
<a name="idm46045056216992">
</a>
<p>
<b>
A.5.9.
</b>
</p>
</td>
<td align="left" valign="top">
<p>
Can triggers access tables?
</p>
</td>
</tr>
<tr class="answer">
<td align="left" valign="top">
</td>
<td align="left" valign="top">
<p>
A trigger can access both old and new data in its own table. A
trigger can also affect other tables, but it is not permitted to
modify a table that is already being used (for reading or
writing) by the statement that invoked the function or trigger.
</p>
</td>
</tr>
<tr class="question">
<td align="left" valign="top">
<a name="faq-mysql-can-triggers-same-events">
</a>
<a name="idm46045056214704">
</a>
<p>
<b>
A.5.10.
</b>
</p>
</td>
<td align="left" valign="top">
<p>
Can a table have multiple triggers with the same trigger event
and action time?
</p>
</td>
</tr>
<tr class="answer">
<td align="left" valign="top">
</td>
<td align="left" valign="top">
<p>
In MySQL 8.4, it is possible to define multiple
triggers for a given table that have the same trigger event and
action time. For example, you can have two
<code class="literal">
BEFORE
UPDATE
</code>
triggers for a table. By default, triggers that
have the same trigger event and action time activate in the
order they were created. To affect trigger order, specify a
clause after
<code class="literal">
FOR EACH ROW
</code>
that indicates
<code class="literal">
FOLLOWS
</code>
or
<code class="literal">
PRECEDES
</code>
and
the name of an existing trigger that also has the same trigger
event and action time. With
<code class="literal">
FOLLOWS
</code>
, the new
trigger activates after the existing trigger. With
<code class="literal">
PRECEDES
</code>
, the new trigger activates before
the existing trigger.
</p>
</td>
</tr>
<tr class="question">
<td align="left" valign="top">
<a name="faq-mysql-can-triggers-remote">
</a>
<a name="idm46045056207744">
</a>
<p>
<b>
A.5.11.
</b>
</p>
</td>
<td align="left" valign="top">
<p>
Is it possible for a trigger to update tables on a remote
server?
</p>
</td>
</tr>
<tr class="answer">
<td align="left" valign="top">
</td>
<td align="left" valign="top">
<p>
Yes. A table on a remote server could be updated using the
<code class="literal">
FEDERATED
</code>
storage engine. (See
<a class="xref" href="federated-storage-engine.html" title="18.8 The FEDERATED Storage Engine">
Section 18.8, “The FEDERATED Storage Engine”
</a>
).
</p>
</td>
</tr>
<tr class="question">
<td align="left" valign="top">
<a name="faq-mysql-can-triggers-replication">
</a>
<a name="idm46045056204240">
</a>
<p>
<b>
A.5.12.
</b>
</p>
</td>
<td align="left" valign="top">
<p>
Do triggers work with replication?
</p>
</td>
</tr>
<tr class="answer">
<td align="left" valign="top">
</td>
<td align="left" valign="top">
<p>
Yes. However, the way in which they work depends whether you are
using MySQL's
<span class="quote">
“
<span class="quote">
classic
</span>
”
</span>
statement-based or
row-based replication format.
</p>
<p>
When using statement-based replication, triggers on the replica
are executed by statements that are executed on the source (and
replicated to the replica).
</p>
<p>
When using row-based replication, triggers are not executed on
the replica due to statements that were run on the source and
then replicated to the replica. Instead, when using row-based
replication, the changes caused by executing the trigger on the
source are applied on the replica.
</p>
<p>
For more information, see
<a class="xref" href="replication-features-triggers.html" title="19.5.1.36 Replication and Triggers">
Section 19.5.1.36, “Replication and Triggers”
</a>
.
</p>
</td>
</tr>
<tr class="question">
<td align="left" valign="top">
<a name="faq-mysql-how-triggers-source-replica">
</a>
<a name="idm46045056199168">
</a>
<p>
<b>
A.5.13.
</b>
</p>
</td>
<td align="left" valign="top">
<p>
How are actions carried out through triggers on a source
replicated to a replica?
</p>
</td>
</tr>
<tr class="answer">
<td align="left" valign="top">
</td>
<td align="left" valign="top">
<p>
Again, this depends on whether you are using statement-based or
row-based replication.
</p>
<p>
<b>
Statement-based replication.
</b>
First, the triggers that exist on a source must be re-created
on the replica server. Once this is done, the replication flow
works as any other standard DML statement that participates in
replication. For example, consider a table
<code class="literal">
EMP
</code>
that has an
<code class="literal">
AFTER
</code>
insert trigger, which exists on a replication source server.
The same
<code class="literal">
EMP
</code>
table and
<code class="literal">
AFTER
</code>
insert trigger exist on the replica
server as well. The replication flow would be:
</p>
<div class="orderedlist">
<ol class="orderedlist" type="1">
<li class="listitem">
<p>
An
<a class="link" href="insert.html" title="15.2.7 INSERT Statement">
<code class="literal">
INSERT
</code>
</a>
statement is made
to
<code class="literal">
EMP
</code>
.
</p>
</li>
<li class="listitem">
<p>
The
<code class="literal">
AFTER
</code>
trigger on
<code class="literal">
EMP
</code>
activates.
</p>
</li>
<li class="listitem">
<p>
The
<a class="link" href="insert.html" title="15.2.7 INSERT Statement">
<code class="literal">
INSERT
</code>
</a>
statement is
written to the binary log.
</p>
</li>
<li class="listitem">
<p>
The replica picks up the
<a class="link" href="insert.html" title="15.2.7 INSERT Statement">
<code class="literal">
INSERT
</code>
</a>
statement to
<code class="literal">
EMP
</code>
and executes it.
</p>
</li>
<li class="listitem">
<p>
The
<code class="literal">
AFTER
</code>
trigger on
<code class="literal">
EMP
</code>
that exists on the replica activates.
</p>
</li>
</ol>
</div>
<p>
<b>
Row-based replication.
</b>
When you use row-based replication, the changes caused by
executing the trigger on the source are applied on the
replica. However, the triggers themselves are not actually
executed on the replica under row-based replication. This is
because, if both the source and the replica applied the
changes from the source and, in addition, the trigger causing
these changes were applied on the replica, the changes would
in effect be applied twice on the replica, leading to
different data on the source and the replica.
</p>
<p>
In most cases, the outcome is the same for both row-based and
statement-based replication. However, if you use different
triggers on the source and replica, you cannot use row-based
replication. (This is because the row-based format replicates
the changes made by triggers executing on the source to the
replicas, rather than the statements that caused the triggers to
execute, and the corresponding triggers on the replica are not
executed.) Instead, any statements causing such triggers to be
executed must be replicated using statement-based replication.
</p>
<p>
For more information, see
<a class="xref" href="replication-features-triggers.html" title="19.5.1.36 Replication and Triggers">
Section 19.5.1.36, “Replication and Triggers”
</a>
.
</p>
</td>
</tr>
</tbody>
</table>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/performance-schema-replication-applier-configuration-table.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="performance-schema-replication-applier-configuration-table">
</a>
29.12.11.2 The replication_applier_configuration Table
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045071586032">
</a>
<a class="indexterm" name="idm46045071584528">
</a>
<p>
This table shows the configuration parameters that affect
transactions applied by the replica. Parameters stored in the
table can be changed at runtime with 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.
</p>
<p>
The
<a class="link" href="performance-schema-replication-applier-configuration-table.html" title="29.12.11.2 The replication_applier_configuration Table">
<code class="literal">
replication_applier_configuration
</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">
CHANNEL_NAME
</code>
</p>
<p>
The replication channel which this row is displaying.
There is always a default replication channel, and more
replication channels can be added. See
<a class="xref" href="replication-channels.html" title="19.2.2 Replication Channels">
Section 19.2.2, “Replication Channels”
</a>
for more
information.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
DESIRED_DELAY
</code>
</p>
<p>
The number of seconds that the replica must lag the source
(
<code class="literal">
CHANGE REPLICATION SOURCE TO
</code>
option:
<code class="literal">
SOURCE_DELAY
</code>
). See
<a class="xref" href="replication-delayed.html" title="19.4.11 Delayed Replication">
Section 19.4.11, “Delayed Replication”
</a>
for more
information.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
PRIVILEGE_CHECKS_USER
</code>
</p>
<p>
The user account that provides the security context for
the channel (
<code class="literal">
CHANGE REPLICATION SOURCE
TO
</code>
option:
<code class="literal">
PRIVILEGE_CHECKS_USER
</code>
). This is escaped
so that it can be copied into an SQL statement to execute
individual transactions. See
<a class="xref" href="replication-privilege-checks.html" title="19.3.3 Replication Privilege Checks">
Section 19.3.3, “Replication Privilege Checks”
</a>
for more
information.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
REQUIRE_ROW_FORMAT
</code>
</p>
<p>
Whether the channel accepts only row-based events
(
<code class="literal">
CHANGE REPLICATION SOURCE TO
</code>
option:
<code class="literal">
REQUIRE_ROW_FORMAT
</code>
). See
<a class="xref" href="replication-privilege-checks.html" title="19.3.3 Replication Privilege Checks">
Section 19.3.3, “Replication Privilege Checks”
</a>
for more
information.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
REQUIRE_TABLE_PRIMARY_KEY_CHECK
</code>
</p>
<p>
Whether the channel requires primary keys always, never,
or according to the source's setting (
<code class="literal">
CHANGE
REPLICATION SOURCE TO
</code>
option:
<code class="literal">
REQUIRE_TABLE_PRIMARY_KEY_CHECK
</code>
). See
<a class="xref" href="replication-privilege-checks.html" title="19.3.3 Replication Privilege Checks">
Section 19.3.3, “Replication Privilege Checks”
</a>
for more
information.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
ASSIGN_GTIDS_TO_ANONYMOUS_TRANSACTIONS_TYPE
</code>
</p>
<p>
Whether the channel assigns a GTID to replicated
transactions that do not already have one (
<code class="literal">
CHANGE
REPLICATION SOURCE TO
</code>
option:
<code class="literal">
ASSIGN_GTIDS_TO_ANONYMOUS_TRANSACTIONS
</code>
).
<code class="literal">
OFF
</code>
means no GTIDs are assigned.
<code class="literal">
LOCAL
</code>
means a GTID is assigned that
includes the replica's own UUID (the
<a class="link" href="replication-options.html#sysvar_server_uuid">
<code class="literal">
server_uuid
</code>
</a>
setting).
<code class="literal">
UUID
</code>
means a GTID is assigned that
includes a manually set UUID. See
<a class="xref" href="replication-gtids-assign-anon.html" title="19.1.3.6 Replication From a Source Without GTIDs to a Replica With GTIDs">
Section 19.1.3.6, “Replication From a Source Without GTIDs to a Replica With GTIDs”
</a>
for more
information.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
ASSIGN_GTIDS_TO_ANONYMOUS_TRANSACTIONS_VALUE
</code>
</p>
<p>
The UUID that is used as part of the GTIDs assigned to
anonymous transactions (
<code class="literal">
CHANGE REPLICATION SOURCE
TO
</code>
option:
<code class="literal">
ASSIGN_GTIDS_TO_ANONYMOUS_TRANSACTIONS
</code>
).
See
<a class="xref" href="replication-gtids-assign-anon.html" title="19.1.3.6 Replication From a Source Without GTIDs to a Replica With GTIDs">
Section 19.1.3.6, “Replication From a Source Without GTIDs to a Replica With GTIDs”
</a>
for
more information.
</p>
</li>
</ul>
</div>
<p>
The
<a class="link" href="performance-schema-replication-applier-configuration-table.html" title="29.12.11.2 The replication_applier_configuration Table">
<code class="literal">
replication_applier_configuration
</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">
CHANNEL_NAME
</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-replication-applier-configuration-table.html" title="29.12.11.2 The replication_applier_configuration Table">
<code class="literal">
replication_applier_configuration
</code>
</a>
table.
</p>
<p>
The following table shows the correspondence between
<a class="link" href="performance-schema-replication-applier-configuration-table.html" title="29.12.11.2 The replication_applier_configuration Table">
<code class="literal">
replication_applier_configuration
</code>
</a>
columns and
<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>
columns.
</p>
<div class="informaltable">
<table summary="Correspondence between replication_applier_configuration columns and SHOW REPLICA STATUS columns">
<colgroup>
<col style="width: 60%"/>
<col style="width: 40%"/>
</colgroup>
<thead>
<tr>
<th>
<code class="literal">
replication_applier_configuration
</code>
Column
</th>
<th>
<code class="literal">
SHOW REPLICA STATUS
</code>
Column
</th>
</tr>
</thead>
<tbody>
<tr>
<td>
<code class="literal">
DESIRED_DELAY
</code>
</td>
<td>
<code class="literal">
SQL_Delay
</code>
</td>
</tr>
</tbody>
</table>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/mysql-shell-tutorial-javascript-table-insert.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="mysql-shell-tutorial-javascript-table-insert">
</a>
22.3.4.1 Insert Records into Tables
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045127606400">
</a>
<p>
You can use the
<code class="literal">
insert()
</code>
method with the
<code class="literal">
values()
</code>
method to insert records into an
existing relational table. The
<code class="literal">
insert()
</code>
method accepts individual columns or all columns in the table.
Use one or more
<code class="literal">
values()
</code>
methods to specify
the values to be inserted.
</p>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h5 class="title">
<a name="mysql-shell-tutorial-javascript-insert-complete-record">
</a>
Insert a Complete Record
</h5>
</div>
</div>
</div>
<a class="indexterm" name="idm46045127600192">
</a>
<p>
To insert a complete record, pass to the
<code class="literal">
insert()
</code>
method all columns in the table.
Then pass to the
<code class="literal">
values()
</code>
method one value
for each column in the table. For example, to add a new record
to the city table in the
<code class="literal">
world_x
</code>
schema,
insert the following record and press
<span class="keycap">
<strong>
Enter
</strong>
</span>
twice.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-mysqlsh"><div class="docs-select-all right" id="sa12736204"><div class="copy-help left">Press ⌘+C to 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-js></span> db<span class="token punctuation">.</span>city<span class="token punctuation">.</span><span class="token function">insert</span><span class="token punctuation">(</span><span class="token string">"ID"</span><span class="token punctuation">,</span> <span class="token string">"Name"</span><span class="token punctuation">,</span> <span class="token string">"CountryCode"</span><span class="token punctuation">,</span> <span class="token string">"District"</span><span class="token punctuation">,</span> <span class="token string">"Info"</span><span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">values</span><span class="token punctuation">(</span>
None<span class="token punctuation">,</span> <span class="token string">"Olympia"</span><span class="token punctuation">,</span> <span class="token string">"USA"</span><span class="token punctuation">,</span> <span class="token string">"Washington"</span><span class="token punctuation">,</span> <span class="token string">'{"Population": 5000}'</span><span class="token punctuation">)</span></code></pre>
</div>
<p>
The city table has five columns: ID, Name, CountryCode,
District, and Info. Each value must match the data type of the
column it represents.
</p>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h5 class="title">
<a name="mysql-shell-tutorial-javascript-insert-partial-record">
</a>
Insert a Partial Record
</h5>
</div>
</div>
</div>
<a class="indexterm" name="idm46045127591440">
</a>
<p>
The following example inserts values into the ID, Name, and
CountryCode columns of the city table.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-mysqlsh"><div class="docs-select-all right" id="sa6756219"><div class="copy-help left">Press ⌘+C to 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-js></span> db<span class="token punctuation">.</span>city<span class="token punctuation">.</span><span class="token function">insert</span><span class="token punctuation">(</span><span class="token string">"ID"</span><span class="token punctuation">,</span> <span class="token string">"Name"</span><span class="token punctuation">,</span> <span class="token string">"CountryCode"</span><span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">values</span><span class="token punctuation">(</span>
None<span class="token punctuation">,</span> <span class="token string">"Little Falls"</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 function">values</span><span class="token punctuation">(</span>None<span class="token punctuation">,</span> <span class="token string">"Happy Valley"</span><span class="token punctuation">,</span> <span class="token string">"USA"</span><span class="token punctuation">)</span></code></pre>
</div>
<p>
When you specify columns using the
<code class="literal">
insert()
</code>
method, the number of values must match the number of columns.
In the previous example, you must supply three values to match
the three columns specified.
</p>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h5 class="title">
<a name="idm46045127586256">
</a>
Related Information
</h5>
</div>
</div>
</div>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
See
<a class="ulink" href="/doc/x-devapi-userguide/en/crud-ebnf-table-crud-functions.html#crud-ebnf-tableinsertfunction" target="_top">
TableInsertFunction
</a>
for
the full syntax definition.
</p>
</li>
</ul>
</div>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/drop-trigger.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="drop-trigger">
</a>
15.1.34 DROP TRIGGER Statement
</h3>
</div>
</div>
</div>
<a class="indexterm" name="idm46045183240496">
</a>
<a class="indexterm" name="idm46045183239424">
</a>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa57097968"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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">TRIGGER</span> <span class="token punctuation">[</span><span class="token keyword">IF</span> <span class="token keyword">EXISTS</span><span class="token punctuation">]</span> <span class="token punctuation">[</span><span class="token keyword"><em class="replaceable">schema_name</em></span><span class="token punctuation">.</span><span class="token punctuation">]</span><em class="replaceable">trigger_name</em></code></pre>
</div>
<p>
This statement drops a trigger. The schema (database) name is
optional. If the schema is omitted, the trigger is dropped from
the default schema.
<a class="link" href="drop-trigger.html" title="15.1.34 DROP TRIGGER Statement">
<code class="literal">
DROP TRIGGER
</code>
</a>
requires the
<a class="link" href="privileges-provided.html#priv_trigger">
<code class="literal">
TRIGGER
</code>
</a>
privilege for
the table associated with the trigger.
</p>
<p>
Use
<code class="literal">
IF EXISTS
</code>
to prevent an error from
occurring for a trigger that does not exist. A
<code class="literal">
NOTE
</code>
is generated for a nonexistent trigger
when using
<code class="literal">
IF EXISTS
</code>
. See
<a class="xref" href="show-warnings.html" title="15.7.7.42 SHOW WARNINGS Statement">
Section 15.7.7.42, “SHOW WARNINGS Statement”
</a>
.
</p>
<p>
Triggers for a table are also dropped if you drop the table.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/obtaining-component-information.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="obtaining-component-information">
</a>
7.5.2 Obtaining Component Information
</h3>
</div>
</div>
</div>
<p>
The
<code class="literal">
mysql.component
</code>
system table contains
information about currently loaded components and shows which
components have been registered using
<a class="link" href="install-component.html" title="15.7.4.3 INSTALL COMPONENT Statement">
<code class="literal">
INSTALL
COMPONENT
</code>
</a>
. Selecting from the table shows which
components are installed. For example:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa54414644"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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> mysql<span class="token punctuation">.</span><span class="token keyword">component</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>
<span class="token output"><span class="token punctuation">|</span> component_id <span class="token punctuation">|</span> component_group_id <span class="token punctuation">|</span> component_urn <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>
<span class="token output"><span class="token punctuation">|</span> 1 <span class="token punctuation">|</span> 1 <span class="token punctuation">|</span> file://component_validate_password <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> file://component_log_sink_json <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></code></pre>
</div>
<p>
The
<code class="literal">
component_id
</code>
and
<code class="literal">
component_group_id
</code>
values are for internal use.
The
<code class="literal">
component_urn
</code>
is the URN used in
<a class="link" href="install-component.html" title="15.7.4.3 INSTALL COMPONENT Statement">
<code class="literal">
INSTALL COMPONENT
</code>
</a>
and
<a class="link" href="uninstall-component.html" title="15.7.4.5 UNINSTALL COMPONENT Statement">
<code class="literal">
UNINSTALL COMPONENT
</code>
</a>
statements to
load and unload the component.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/group-replication-fine-tuning-the-group-communication-thread.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="group-replication-fine-tuning-the-group-communication-thread">
</a>
20.7.1 Fine Tuning the Group Communication Thread
</h3>
</div>
</div>
</div>
<a class="indexterm" name="idm46045132229808">
</a>
<a class="indexterm" name="idm46045132228288">
</a>
<p>
The group communication thread (GCT) runs in a loop while the
Group Replication plugin is loaded. The GCT receives messages from
the group and from the plugin, handles quorum and failure
detection related tasks, sends out some keep alive messages and
also handles the incoming and outgoing transactions from/to the
server/group. The GCT waits for incoming messages in a queue. When
there are no messages, the GCT waits. By configuring this wait to
be a little longer (doing an active wait) before actually going to
sleep can prove to be beneficial in some cases. This is because
the alternative is for the operating system to switch out the GCT
from the processor and do a context switch.
</p>
<p>
To force the GCT to do an active wait, use the
<a class="link" href="group-replication-system-variables.html#sysvar_group_replication_poll_spin_loops">
<code class="literal">
group_replication_poll_spin_loops
</code>
</a>
option, which makes the GCT loop, doing nothing relevant for the
configured number of loops, before actually polling the queue for
the next message.
</p>
<p>
For example:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa3825314"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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_poll_spin_loops<span class="token operator">=</span> <span class="token number">10000</span><span class="token punctuation">;</span></code></pre>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/innodb-performance-optimizer-statistics.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="innodb-performance-optimizer-statistics">
</a>
17.8.10 Configuring Optimizer Statistics for InnoDB
</h3>
</div>
</div>
</div>
<div class="toc">
<dl class="toc">
<dt>
<span class="section">
<a href="innodb-persistent-stats.html">
17.8.10.1 Configuring Persistent Optimizer Statistics Parameters
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="innodb-statistics-estimation.html">
17.8.10.2 Configuring Non-Persistent Optimizer Statistics Parameters
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="innodb-analyze-table-complexity.html">
17.8.10.3 Estimating ANALYZE TABLE Complexity for InnoDB Tables
</a>
</span>
</dt>
</dl>
</div>
<p>
This section describes how to configure persistent and
non-persistent optimizer statistics for
<code class="literal">
InnoDB
</code>
tables.
</p>
<p>
Persistent optimizer statistics are persisted across server
restarts, allowing for greater
<a class="link" href="glossary.html#glos_plan_stability" title="plan stability">
plan stability
</a>
and more
consistent query performance. Persistent optimizer statistics also
provide control and flexibility with these additional benefits:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
You can use the
<a class="link" href="innodb-parameters.html#sysvar_innodb_stats_auto_recalc">
<code class="literal">
innodb_stats_auto_recalc
</code>
</a>
configuration option to control whether statistics are updated
automatically after substantial changes to a table.
</p>
</li>
<li class="listitem">
<p>
You can use the
<code class="literal">
STATS_PERSISTENT
</code>
,
<code class="literal">
STATS_AUTO_RECALC
</code>
, and
<code class="literal">
STATS_SAMPLE_PAGES
</code>
clauses with
<a class="link" href="create-table.html" title="15.1.20 CREATE TABLE Statement">
<code class="literal">
CREATE TABLE
</code>
</a>
and
<a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement">
<code class="literal">
ALTER TABLE
</code>
</a>
statements to
configure optimizer statistics for individual tables.
</p>
</li>
<li class="listitem">
<p>
You can query optimizer statistics data in the
<code class="literal">
mysql.innodb_table_stats
</code>
and
<code class="literal">
mysql.innodb_index_stats
</code>
tables.
</p>
</li>
<li class="listitem">
<p>
You can view the
<code class="literal">
last_update
</code>
column of the
<code class="literal">
mysql.innodb_table_stats
</code>
and
<code class="literal">
mysql.innodb_index_stats
</code>
tables to see when
statistics were last updated.
</p>
</li>
<li class="listitem">
<p>
You can manually modify the
<code class="literal">
mysql.innodb_table_stats
</code>
and
<code class="literal">
mysql.innodb_index_stats
</code>
tables to force a
specific query optimization plan or to test alternative plans
without modifying the database.
</p>
</li>
</ul>
</div>
<p>
The persistent optimizer statistics feature is enabled by default
(
<a class="link" href="innodb-parameters.html#sysvar_innodb_stats_persistent">
<code class="literal">
innodb_stats_persistent=ON
</code>
</a>
).
</p>
<p>
Non-persistent optimizer statistics are cleared on each server
restart and after some other operations, and recomputed on the
next table access. As a result, different estimates could be
produced when recomputing statistics, leading to different choices
in execution plans and variations in query performance.
</p>
<p>
This section also provides information about estimating
<a class="link" href="analyze-table.html" title="15.7.3.1 ANALYZE TABLE Statement">
<code class="literal">
ANALYZE TABLE
</code>
</a>
complexity, which may
be useful when attempting to achieve a balance between accurate
statistics and
<a class="link" href="analyze-table.html" title="15.7.3.1 ANALYZE TABLE Statement">
<code class="literal">
ANALYZE TABLE
</code>
</a>
execution time.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/mysql-cluster-config-starting.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="mysql-cluster-config-starting">
</a>
25.4.3.2 Recommended Starting Configuration for NDB Cluster
</h4>
</div>
</div>
</div>
<p>
Achieving the best performance from an NDB Cluster depends on a
number of factors including the following:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
NDB Cluster software version
</p>
</li>
<li class="listitem">
<p>
Numbers of data nodes and SQL nodes
</p>
</li>
<li class="listitem">
<p>
Hardware
</p>
</li>
<li class="listitem">
<p>
Operating system
</p>
</li>
<li class="listitem">
<p>
Amount of data to be stored
</p>
</li>
<li class="listitem">
<p>
Size and type of load under which the cluster is to operate
</p>
</li>
</ul>
</div>
<p>
Therefore, obtaining an optimum configuration is likely to be an
iterative process, the outcome of which can vary widely with the
specifics of each NDB Cluster deployment. Changes in
configuration are also likely to be indicated when changes are
made in the platform on which the cluster is run, or in
applications that use the NDB Cluster 's data. For these
reasons, it is not possible to offer a single configuration that
is ideal for all usage scenarios. However, in this section, we
provide a recommended base configuration.
</p>
<p>
<b>
Starting config.ini file.
</b>
The following
<code class="filename">
config.ini
</code>
file is a
recommended starting point for configuring a cluster running
NDB Cluster 8.4:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-ini"><div class="docs-select-all right" id="sa56045213"><div class="copy-help left">Press ⌘+C to 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 comment" spellcheck="true"># TCP PARAMETERS</span>
<span class="token selector">[tcp default]</span>
<span class="token constant">SendBufferMemory</span><span class="token attr-value"><span class="token punctuation">=</span>2M</span>
<span class="token constant">ReceiveBufferMemory</span><span class="token attr-value"><span class="token punctuation">=</span>2M</span>
<span class="token comment" spellcheck="true"># Increasing the sizes of these 2 buffers beyond the default values</span>
<span class="token comment" spellcheck="true"># helps prevent bottlenecks due to slow disk I/O.</span>
<span class="token comment" spellcheck="true"># MANAGEMENT NODE PARAMETERS</span>
<span class="token selector">[ndb_mgmd default]</span>
<span class="token constant">DataDir</span><span class="token attr-value"><span class="token punctuation">=</span><em class="replaceable">path/to/management/server/data/directory</em></span>
<span class="token comment" spellcheck="true"># It is possible to use a different data directory for each management</span>
<span class="token comment" spellcheck="true"># server, but for ease of administration it is preferable to be</span>
<span class="token comment" spellcheck="true"># consistent.</span>
<span class="token selector">[ndb_mgmd]</span>
<span class="token constant">HostName</span><span class="token attr-value"><span class="token punctuation">=</span><em class="replaceable">management-server-A-hostname</em></span>
<span class="token comment" spellcheck="true"># NodeId=<em class="replaceable">management-server-A-nodeid</em></span>
<span class="token selector">[ndb_mgmd]</span>
<span class="token constant">HostName</span><span class="token attr-value"><span class="token punctuation">=</span><em class="replaceable">management-server-B-hostname</em></span>
<span class="token comment" spellcheck="true"># NodeId=<em class="replaceable">management-server-B-nodeid</em></span>
<span class="token comment" spellcheck="true"># Using 2 management servers helps guarantee that there is always an</span>
<span class="token comment" spellcheck="true"># arbitrator in the event of network partitioning, and so is</span>
<span class="token comment" spellcheck="true"># recommended for high availability. Each management server must be</span>
<span class="token comment" spellcheck="true"># identified by a HostName. You may for the sake of convenience specify</span>
<span class="token comment" spellcheck="true"># a NodeId for any management server, although one is allocated</span>
<span class="token comment" spellcheck="true"># for it automatically; if you do so, it must be in the range 1-255</span>
<span class="token comment" spellcheck="true"># inclusive and must be unique among all IDs specified for cluster</span>
<span class="token comment" spellcheck="true"># nodes.</span>
<span class="token comment" spellcheck="true"># DATA NODE PARAMETERS</span>
<span class="token selector">[ndbd default]</span>
<span class="token constant">NoOfReplicas</span><span class="token attr-value"><span class="token punctuation">=</span>2</span>
<span class="token comment" spellcheck="true"># Using two fragment replicas is recommended to guarantee availability of data;</span>
<span class="token comment" spellcheck="true"># using only one fragment replica does not provide any redundancy, which means</span>
<span class="token comment" spellcheck="true"># that the failure of a single data node causes the entire cluster to shut down. </span>
<span class="token comment" spellcheck="true"># It is also possible (but not required) to use more than two fragment replicas, </span>
<span class="token comment" spellcheck="true"># although two fragment replicas are sufficient to provide high availability. </span>
<span class="token constant">LockPagesInMainMemory</span><span class="token attr-value"><span class="token punctuation">=</span>1</span>
<span class="token comment" spellcheck="true"># On Linux and Solaris systems, setting this parameter locks data node</span>
<span class="token comment" spellcheck="true"># processes into memory. Doing so prevents them from swapping to disk,</span>
<span class="token comment" spellcheck="true"># which can severely degrade cluster performance.</span>
<span class="token constant">DataMemory</span><span class="token attr-value"><span class="token punctuation">=</span>3456M</span>
<span class="token comment" spellcheck="true"># The value provided for DataMemory assumes 4 GB RAM</span>
<span class="token comment" spellcheck="true"># per data node. However, for best results, you should first calculate</span>
<span class="token comment" spellcheck="true"># the memory that would be used based on the data you actually plan to</span>
<span class="token comment" spellcheck="true"># store (you may find the ndb_size.pl utility helpful in estimating</span>
<span class="token comment" spellcheck="true"># this), then allow an extra 20% over the calculated values. Naturally,</span>
<span class="token comment" spellcheck="true"># you should ensure that each data node host has at least as much</span>
<span class="token comment" spellcheck="true"># physical memory as the sum of these two values.</span>
<span class="token comment" spellcheck="true"># ODirect=1</span>
<span class="token comment" spellcheck="true"># Enabling this parameter causes NDBCLUSTER to try using O_DIRECT</span>
<span class="token comment" spellcheck="true"># writes for local checkpoints and redo logs; this can reduce load on</span>
<span class="token comment" spellcheck="true"># CPUs. We recommend doing so when using NDB Cluster on systems running</span>
<span class="token comment" spellcheck="true"># Linux kernel 2.6 or later.</span>
<span class="token constant">NoOfFragmentLogFiles</span><span class="token attr-value"><span class="token punctuation">=</span>300</span>
<span class="token constant">DataDir</span><span class="token attr-value"><span class="token punctuation">=</span><em class="replaceable">path/to/data/node/data/directory</em></span>
<span class="token constant">MaxNoOfConcurrentOperations</span><span class="token attr-value"><span class="token punctuation">=</span>100000</span>
<span class="token constant">SchedulerSpinTimer</span><span class="token attr-value"><span class="token punctuation">=</span>400</span>
<span class="token constant">SchedulerExecutionTimer</span><span class="token attr-value"><span class="token punctuation">=</span>100</span>
<span class="token constant">RealTimeScheduler</span><span class="token attr-value"><span class="token punctuation">=</span>1</span>
<span class="token comment" spellcheck="true"># Setting these parameters allows you to take advantage of real-time scheduling</span>
<span class="token comment" spellcheck="true"># of NDB threads to achieve increased throughput when using ndbd. They</span>
<span class="token comment" spellcheck="true"># are not needed when using ndbmtd; in particular, you should not set</span>
<span class="token comment" spellcheck="true"># RealTimeScheduler for ndbmtd data nodes.</span>
<span class="token constant">TimeBetweenGlobalCheckpoints</span><span class="token attr-value"><span class="token punctuation">=</span>1000</span>
<span class="token constant">TimeBetweenEpochs</span><span class="token attr-value"><span class="token punctuation">=</span>200</span>
<span class="token constant">RedoBuffer</span><span class="token attr-value"><span class="token punctuation">=</span>32M</span>
<span class="token comment" spellcheck="true"># CompressedLCP=1</span>
<span class="token comment" spellcheck="true"># CompressedBackup=1</span>
<span class="token comment" spellcheck="true"># Enabling CompressedLCP and CompressedBackup causes, respectively, local</span>
checkpoint files and backup files to be compressed, which can result in a space
savings of up to 50% over noncompressed LCPs and backups.
<span class="token comment" spellcheck="true"># MaxNoOfLocalScans=64</span>
<span class="token constant">MaxNoOfTables</span><span class="token attr-value"><span class="token punctuation">=</span>1024</span>
<span class="token constant">MaxNoOfOrderedIndexes</span><span class="token attr-value"><span class="token punctuation">=</span>256</span>
<span class="token selector">[ndbd]</span>
<span class="token constant">HostName</span><span class="token attr-value"><span class="token punctuation">=</span><em class="replaceable">data-node-A-hostname</em></span>
<span class="token comment" spellcheck="true"># NodeId=<em class="replaceable">data-node-A-nodeid</em></span>
<span class="token constant">LockExecuteThreadToCPU</span><span class="token attr-value"><span class="token punctuation">=</span>1</span>
<span class="token constant">LockMaintThreadsToCPU</span><span class="token attr-value"><span class="token punctuation">=</span>0</span>
<span class="token comment" spellcheck="true"># On systems with multiple CPUs, these parameters can be used to lock NDBCLUSTER</span>
<span class="token comment" spellcheck="true"># threads to specific CPUs</span>
<span class="token selector">[ndbd]</span>
<span class="token constant">HostName</span><span class="token attr-value"><span class="token punctuation">=</span><em class="replaceable">data-node-B-hostname</em></span>
<span class="token comment" spellcheck="true"># NodeId=<em class="replaceable">data-node-B-nodeid</em></span>
<span class="token constant">LockExecuteThreadToCPU</span><span class="token attr-value"><span class="token punctuation">=</span>1</span>
<span class="token constant">LockMaintThreadsToCPU</span><span class="token attr-value"><span class="token punctuation">=</span>0</span>
<span class="token comment" spellcheck="true"># You must have an [ndbd] section for every data node in the cluster;</span>
<span class="token comment" spellcheck="true"># each of these sections must include a HostName. Each section may</span>
<span class="token comment" spellcheck="true"># optionally include a NodeId for convenience, but in most cases, it is</span>
<span class="token comment" spellcheck="true"># sufficient to allow the cluster to allocate node IDs dynamically. If</span>
<span class="token comment" spellcheck="true"># you do specify the node ID for a data node, it must be in the range 1</span>
<span class="token comment" spellcheck="true"># to 144 inclusive and must be unique among all IDs specified for</span>
<span class="token comment" spellcheck="true"># cluster nodes.</span>
<span class="token comment" spellcheck="true"># SQL NODE / API NODE PARAMETERS</span>
<span class="token selector">[mysqld]</span>
<span class="token comment" spellcheck="true"># HostName=<em class="replaceable">sql-node-A-hostname</em></span>
<span class="token comment" spellcheck="true"># NodeId=<em class="replaceable">sql-node-A-nodeid</em></span>
<span class="token selector">[mysqld]</span>
<span class="token selector">[mysqld]</span>
<span class="token comment" spellcheck="true"># Each API or SQL node that connects to the cluster requires a [mysqld]</span>
<span class="token comment" spellcheck="true"># or [api] section of its own. Each such section defines a connection</span>
<span class="token comment" spellcheck="true"># “slot”; you should have at least as many of these sections in the</span>
<span class="token comment" spellcheck="true"># config.ini file as the total number of API nodes and SQL nodes that</span>
<span class="token comment" spellcheck="true"># you wish to have connected to the cluster at any given time. There is</span>
<span class="token comment" spellcheck="true"># no performance or other penalty for having extra slots available in</span>
<span class="token comment" spellcheck="true"># case you find later that you want or need more API or SQL nodes to</span>
<span class="token comment" spellcheck="true"># connect to the cluster at the same time.</span>
<span class="token comment" spellcheck="true"># If no HostName is specified for a given [mysqld] or [api] section,</span>
<span class="token comment" spellcheck="true"># then <em>any</em> API or SQL node may use that slot to connect to the</span>
<span class="token comment" spellcheck="true"># cluster. You may wish to use an explicit HostName for one connection slot</span>
<span class="token comment" spellcheck="true"># to guarantee that an API or SQL node from that host can always</span>
<span class="token comment" spellcheck="true"># connect to the cluster. If you wish to prevent API or SQL nodes from</span>
<span class="token comment" spellcheck="true"># connecting from other than a desired host or hosts, then use a</span>
<span class="token comment" spellcheck="true"># HostName for every [mysqld] or [api] section in the config.ini file.</span>
<span class="token comment" spellcheck="true"># You can if you wish define a node ID (NodeId parameter) for any API or</span>
<span class="token comment" spellcheck="true"># SQL node, but this is not necessary; if you do so, it must be in the</span>
<span class="token comment" spellcheck="true"># range 1 to 255 inclusive and must be unique among all IDs specified</span>
<span class="token comment" spellcheck="true"># for cluster nodes.</span></code></pre>
</div>
<p>
<b>
Required my.cnf options for SQL nodes.
</b>
MySQL servers acting as NDB Cluster SQL nodes must always be
started with the
<a class="link" href="mysql-cluster-options-variables.html#option_mysqld_ndbcluster">
<code class="option">
--ndbcluster
</code>
</a>
and
<a class="link" href="mysql-cluster-options-variables.html#option_mysqld_ndb-connectstring">
<code class="option">
--ndb-connectstring
</code>
</a>
options, either on the command line or in
<code class="filename">
my.cnf
</code>
.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/thread-information.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h2 class="title">
<a name="thread-information">
</a>
10.14 Examining Server Thread (Process) Information
</h2>
</div>
</div>
</div>
<div class="toc">
<dl class="toc">
<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>
</div>
<a class="indexterm" name="idm46045222055360">
</a>
<a class="indexterm" name="idm46045222053904">
</a>
<a class="indexterm" name="idm46045222052416">
</a>
<a class="indexterm" name="idm46045222050928">
</a>
<p>
To ascertain what your MySQL server is doing, it can be helpful to
examine the process list, which indicates the operations currently
being performed by the set of threads executing within the server.
For example:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa84389418"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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">PROCESSLIST</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> 5
User<span class="token punctuation">:</span> event_scheduler
Host<span class="token punctuation">:</span> localhost
db<span class="token punctuation">:</span> NULL
Command<span class="token punctuation">:</span> Daemon
Time<span class="token punctuation">:</span> 2756681
State<span class="token punctuation">:</span> Waiting on empty queue
Info<span class="token punctuation">:</span> NULL
<span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span 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>
Id<span class="token punctuation">:</span> 20
User<span class="token punctuation">:</span> me
Host<span class="token punctuation">:</span> localhost<span class="token punctuation">:</span>52943
db<span class="token punctuation">:</span> test
Command<span class="token punctuation">:</span> Query
Time<span class="token punctuation">:</span> 0
State<span class="token punctuation">:</span> starting
Info<span class="token punctuation">:</span> SHOW PROCESSLIST</span></code></pre>
</div>
<p>
Threads can be killed with the
<a class="link" href="kill.html" title="15.7.8.4 KILL Statement">
<code class="literal">
KILL
</code>
</a>
statement. See
<a class="xref" href="kill.html" title="15.7.8.4 KILL Statement">
Section 15.7.8.4, “KILL Statement”
</a>
.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/connector-python-info.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h2 class="title">
<a name="connector-python-info">
</a>
31.5 MySQL Connector/Python
</h2>
</div>
</div>
</div>
<a class="indexterm" name="idm46045060363776">
</a>
<a class="indexterm" name="idm46045060362736">
</a>
<p>
The MySQL Connector/Python manual is published in standalone form,
not as part of the MySQL Reference Manual. For information, see
these documents:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
Main manual:
<a class="ulink" href="/doc/connector-python/en/" target="_top">
MySQL Connector/Python Developer Guide
</a>
</p>
</li>
<li class="listitem">
<p>
Release notes:
<a class="ulink" href="/doc/relnotes/connector-python/en/" target="_top">
MySQL
Connector/Python Release Notes
</a>
</p>
</li>
</ul>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/getting-information.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h2 class="title">
<a name="getting-information">
</a>
5.4 Getting Information About Databases and Tables
</h2>
</div>
</div>
</div>
<a class="indexterm" name="idm46045324837216">
</a>
<a class="indexterm" name="idm46045324835760">
</a>
<a class="indexterm" name="idm46045324834272">
</a>
<p>
What if you forget the name of a database or table, or what the
structure of a given table is (for example, what its columns are
called)? MySQL addresses this problem through several statements
that provide information about the databases and tables it
supports.
</p>
<p>
You have previously seen
<a class="link" href="show-databases.html" title="15.7.7.15 SHOW DATABASES Statement">
<code class="literal">
SHOW
DATABASES
</code>
</a>
, which lists the databases managed by the
server. To find out which database is currently selected, use the
<a class="link" href="information-functions.html#function_database">
<code class="literal">
DATABASE()
</code>
</a>
function:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa75342601"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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">DATABASE</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>
<span class="token output"><span class="token punctuation">|</span> DATABASE() <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> menagerie <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></code></pre>
</div>
<p>
If you have not yet selected any database, the result is
<code class="literal">
NULL
</code>
.
</p>
<p>
To find out what tables the default database contains (for
example, when you are not sure about the name of a table), use
this statement:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa31612465"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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 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>
<span class="token output"><span class="token punctuation">|</span> Tables_in_menagerie <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>
<span class="token output"><span class="token punctuation">|</span> event <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> pet <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></code></pre>
</div>
<p>
The name of the column in the output produced by this statement is
always
<code class="literal">
Tables_in_
<em class="replaceable">
<code>
db_name
</code>
</em>
</code>
,
where
<em class="replaceable">
<code>
db_name
</code>
</em>
is the name of the
database. 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>
, for more information.
</p>
<p>
If you want to find out about the structure of a table, the
<a class="link" href="describe.html" title="15.8.1 DESCRIBE Statement">
<code class="literal">
DESCRIBE
</code>
</a>
statement is useful; it
displays information about each of a table's columns:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa78258567"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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">DESCRIBE</span> pet<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> Field <span class="token punctuation">|</span> Type <span class="token punctuation">|</span> Null <span class="token punctuation">|</span> Key <span class="token punctuation">|</span> Default <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>
<span class="token output"><span class="token punctuation">|</span> name <span class="token punctuation">|</span> varchar(20) <span class="token punctuation">|</span> YES <span class="token punctuation">|</span> <span class="token punctuation">|</span> NULL <span class="token punctuation">|</span> <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> owner <span class="token punctuation">|</span> varchar(20) <span class="token punctuation">|</span> YES <span class="token punctuation">|</span> <span class="token punctuation">|</span> NULL <span class="token punctuation">|</span> <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> species <span class="token punctuation">|</span> varchar(20) <span class="token punctuation">|</span> YES <span class="token punctuation">|</span> <span class="token punctuation">|</span> NULL <span class="token punctuation">|</span> <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> sex <span class="token punctuation">|</span> char(1) <span class="token punctuation">|</span> YES <span class="token punctuation">|</span> <span class="token punctuation">|</span> NULL <span class="token punctuation">|</span> <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> birth <span class="token punctuation">|</span> date <span class="token punctuation">|</span> YES <span class="token punctuation">|</span> <span class="token punctuation">|</span> NULL <span class="token punctuation">|</span> <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> death <span class="token punctuation">|</span> date <span class="token punctuation">|</span> YES <span class="token punctuation">|</span> <span class="token punctuation">|</span> NULL <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 class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="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>
<code class="literal">
Field
</code>
indicates the column name,
<code class="literal">
Type
</code>
is the data type for the column,
<code class="literal">
NULL
</code>
indicates whether the column can contain
<code class="literal">
NULL
</code>
values,
<code class="literal">
Key
</code>
indicates
whether the column is indexed, and
<code class="literal">
Default
</code>
specifies the column's default value.
<code class="literal">
Extra
</code>
displays special information about columns: If a column was
created with the
<code class="literal">
AUTO_INCREMENT
</code>
option, the
value is
<code class="literal">
auto_increment
</code>
rather than empty.
</p>
<p>
<code class="literal">
DESC
</code>
is a short form of
<a class="link" href="describe.html" title="15.8.1 DESCRIBE Statement">
<code class="literal">
DESCRIBE
</code>
</a>
. See
<a class="xref" href="describe.html" title="15.8.1 DESCRIBE Statement">
Section 15.8.1, “DESCRIBE Statement”
</a>
, for more information.
</p>
<p>
You can obtain the
<a class="link" href="create-table.html" title="15.1.20 CREATE TABLE Statement">
<code class="literal">
CREATE TABLE
</code>
</a>
statement necessary to create an existing table using the
<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>
statement. See
<a class="xref" href="show-create-table.html" title="15.7.7.11 SHOW CREATE TABLE Statement">
Section 15.7.7.11, “SHOW CREATE TABLE Statement”
</a>
.
</p>
<p>
If you have indexes on a table,
<code class="literal">
SHOW INDEX FROM
<em class="replaceable">
<code>
tbl_name
</code>
</em>
</code>
produces information
about them. See
<a class="xref" href="show-index.html" title="15.7.7.23 SHOW INDEX Statement">
Section 15.7.7.23, “SHOW INDEX Statement”
</a>
, for more about this
statement.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/sql-compound-statements.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h2 class="title">
<a name="sql-compound-statements">
</a>
15.6 Compound Statement Syntax
</h2>
</div>
</div>
</div>
<div class="toc">
<dl class="toc">
<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>
</div>
<a class="indexterm" name="idm46045176520912">
</a>
<a class="indexterm" name="idm46045176519872">
</a>
<a class="indexterm" name="idm46045176518384">
</a>
<a class="indexterm" name="idm46045176517312">
</a>
<p>
This section describes the syntax for the
<a class="link" href="begin-end.html" title="15.6.1 BEGIN ... END Compound Statement">
<code class="literal">
BEGIN ... END
</code>
</a>
compound statement and other statements that can be used in the body
of stored programs: Stored procedures and functions, triggers, and
events. These objects are defined in terms of SQL code that is
stored on the server for later invocation (see
<a class="xref" href="stored-objects.html" title="Chapter 27 Stored Objects">
Chapter 27,
<i>
Stored Objects
</i>
</a>
).
</p>
<p>
A compound statement is a block that can contain other blocks;
declarations for variables, condition handlers, and cursors; and
flow control constructs such as loops and conditional tests.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/mysqldump-tips.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="mysqldump-tips">
</a>
9.4.5 mysqldump Tips
</h3>
</div>
</div>
</div>
<div class="toc">
<dl class="toc">
<dt>
<span class="section">
<a href="mysqldump-copying-database.html">
9.4.5.1 Making a Copy of a Database
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysqldump-copying-to-other-server.html">
9.4.5.2 Copy a Database from one Server to Another
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysqldump-stored-programs.html">
9.4.5.3 Dumping Stored Programs
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysqldump-definition-data-dumps.html">
9.4.5.4 Dumping Table Definitions and Content Separately
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysqldump-upgrade-testing.html">
9.4.5.5 Using mysqldump to Test for Upgrade Incompatibilities
</a>
</span>
</dt>
</dl>
</div>
<p>
This section surveys techniques that enable you 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 solve specific problems:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
How to make a copy a database
</p>
</li>
<li class="listitem">
<p>
How to copy a database from one server to another
</p>
</li>
<li class="listitem">
<p>
How to dump stored programs (stored procedures and
functions, triggers, and events)
</p>
</li>
<li class="listitem">
<p>
How to dump definitions and data separately
</p>
</li>
</ul>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/query-attribute-components.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="query-attribute-components">
</a>
7.5.4 Query Attribute Components
</h3>
</div>
</div>
</div>
<p>
A component service provides access to query attributes (see
<a class="xref" href="query-attributes.html" title="11.6 Query Attributes">
Section 11.6, “Query Attributes”
</a>
). The
<code class="literal">
query_attributes
</code>
component uses this service to
provide access to query attributes within SQL statements.
</p>
<a class="indexterm" name="idm46045257175296">
</a>
<a class="indexterm" name="idm46045257174208">
</a>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
Purpose: Implements the
<a class="link" href="query-attributes.html#function_mysql-query-attribute-string">
<code class="literal">
mysql_query_attribute_string()
</code>
</a>
function that takes an attribute name argument and returns the
attribute value as a string, or
<code class="literal">
NULL
</code>
if the
attribute does not exist.
</p>
</li>
<li class="listitem">
<p>
URN:
<code class="literal">
file://component_query_attributes
</code>
</p>
</li>
</ul>
</div>
<p>
Developers who wish to incorporate the same query-attribute
component service used by
<code class="literal">
query_attributes
</code>
should consult the
<code class="filename">
mysql_query_attributes.h
</code>
file in a MySQL source distribution.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/verifying-package-integrity.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="verifying-package-integrity">
</a>
2.1.4 Verifying Package Integrity Using MD5 Checksums or GnuPG
</h3>
</div>
</div>
</div>
<div class="toc">
<dl class="toc">
<dt>
<span class="section">
<a href="verifying-md5-checksum.html">
2.1.4.1 Verifying the MD5 Checksum
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="checking-gpg-signature.html">
2.1.4.2 Signature Checking Using GnuPG
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="checking-gpg-signature-windows.html">
2.1.4.3 Signature Checking Using Gpg4win for Windows
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="checking-rpm-signature.html">
2.1.4.4 Signature Checking Using RPM
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="gpg-key-archived-packages.html">
2.1.4.5 GPG Public Build Key for Archived Packages
</a>
</span>
</dt>
</dl>
</div>
<p>
After downloading the MySQL package that suits your needs and
before attempting to install it, make sure that it is intact and
has not been tampered with. There are three means of integrity
checking:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
MD5 checksums
</p>
</li>
<li class="listitem">
<p>
Cryptographic signatures using
<code class="literal">
GnuPG
</code>
, the
GNU Privacy Guard
</p>
</li>
<li class="listitem">
<p>
For RPM packages, the built-in RPM integrity verification
mechanism
</p>
</li>
</ul>
</div>
<p>
The following sections describe how to use these methods.
</p>
<p>
If you notice that the MD5 checksum or GPG signatures do not
match, first try to download the respective package one more time,
perhaps from another mirror site.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/what-is-mysql.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="what-is-mysql">
</a>
1.2.1 What is MySQL?
</h3>
</div>
</div>
</div>
<a class="indexterm" name="idm46045335241616">
</a>
<a class="indexterm" name="idm46045335240224">
</a>
<p>
MySQL, the most popular Open Source SQL database management
system, is developed, distributed, and supported by Oracle
Corporation.
</p>
<p>
The MySQL website (
<a class="ulink" href="http://www.mysql.com/" target="_blank">
http://www.mysql.com/
</a>
) provides
the latest information about MySQL software.
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<span class="bold">
<strong>
MySQL is a database management
system.
</strong>
</span>
</p>
<p>
A database is a structured collection of data. It may be
anything from a simple shopping list to a picture gallery or
the vast amounts of information in a corporate network. To
add, access, and process data stored in a computer database,
you need a database management system such as MySQL Server.
Since computers are very good at handling large amounts of
data, database management systems play a central role in
computing, as standalone utilities, or as parts of other
applications.
</p>
</li>
<li class="listitem">
<p>
<span class="bold">
<strong>
MySQL databases are
relational.
</strong>
</span>
</p>
<p>
<a class="indexterm" name="idm46045335233152">
</a>
A relational database stores data in separate tables rather
than putting all the data in one big storeroom. The database
structures are organized into physical files optimized for
speed. The logical model, with objects such as databases,
tables, views, rows, and columns, offers a flexible
programming environment. You set up rules governing the
relationships between different data fields, such as
one-to-one, one-to-many, unique, required or optional, and
<span class="quote">
“
<span class="quote">
pointers
</span>
”
</span>
between different tables. The database
enforces these rules, so that with a well-designed database,
your application never sees inconsistent, duplicate, orphan,
out-of-date, or missing data.
</p>
<p>
The SQL part of
<span class="quote">
“
<span class="quote">
MySQL
</span>
”
</span>
stands for
<span class="quote">
“
<span class="quote">
Structured Query Language
</span>
”
</span>
. SQL is the most
common standardized language used to access databases.
Depending on your programming environment, you might enter SQL
directly (for example, to generate reports), embed SQL
statements into code written in another language, or use a
language-specific API that hides the SQL syntax.
</p>
<p>
SQL is defined by the ANSI/ISO SQL Standard. The SQL standard
has been evolving since 1986 and several versions exist. In
this manual,
<span class="quote">
“
<span class="quote">
SQL-92
</span>
”
</span>
refers to the standard
released in 1992,
<span class="quote">
“
<span class="quote">
SQL:1999
</span>
”
</span>
refers to the
standard released in 1999, and
<span class="quote">
“
<span class="quote">
SQL:2003
</span>
”
</span>
refers
to the current version of the standard. We use the phrase
<span class="quote">
“
<span class="quote">
the SQL standard
</span>
”
</span>
to mean the current version of
the SQL Standard at any time.
</p>
</li>
<li class="listitem">
<p>
<span class="bold">
<strong>
MySQL software is Open
Source.
</strong>
</span>
</p>
<p>
<a class="indexterm" name="idm46045335225280">
</a>
<a class="indexterm" name="idm46045335223888">
</a>
<a class="indexterm" name="idm46045335222496">
</a>
<a class="indexterm" name="idm46045335221104">
</a>
Open Source means that it is possible for anyone to use and
modify the software. Anybody can download the MySQL software
from the Internet and use it without paying anything. If you
wish, you may study the source code and change it to suit your
needs. The MySQL software uses the GPL (GNU General Public
License),
<a class="ulink" href="http://www.fsf.org/licenses/" target="_blank">
http://www.fsf.org/licenses/
</a>
, to
define what you may and may not do with the software in
different situations. If you feel uncomfortable with the GPL
or need to embed MySQL code into a commercial application, you
can buy a commercially licensed version from us. See the MySQL
Licensing Overview for more information
(
<a class="ulink" href="http://www.mysql.com/company/legal/licensing/" target="_blank">
http://www.mysql.com/company/legal/licensing/
</a>
).
</p>
</li>
<li class="listitem">
<p>
<span class="bold">
<strong>
The MySQL Database Server is very fast,
reliable, scalable, and easy to use.
</strong>
</span>
</p>
<p>
If that is what you are looking for, you should give it a try.
MySQL Server can run comfortably on a desktop or laptop,
alongside your other applications, web servers, and so on,
requiring little or no attention. If you dedicate an entire
machine to MySQL, you can adjust the settings to take
advantage of all the memory, CPU power, and I/O capacity
available. MySQL can also scale up to clusters of machines,
networked together.
</p>
<p>
MySQL Server was originally developed to handle large
databases much faster than existing solutions and has been
successfully used in highly demanding production environments
for several years. Although under constant development, MySQL
Server today offers a rich and useful set of functions. Its
connectivity, speed, and security make MySQL Server highly
suited for accessing databases on the Internet.
</p>
</li>
<li class="listitem">
<p>
<span class="bold">
<strong>
MySQL Server works in client/server or
embedded systems.
</strong>
</span>
</p>
<p>
The MySQL Database Software is a client/server system that
consists of a multithreaded SQL server that supports different
back ends, several different client programs and libraries,
administrative tools, and a wide range of application
programming interfaces (APIs).
</p>
<p>
We also provide MySQL Server as an embedded multithreaded
library that you can link into your application to get a
smaller, faster, easier-to-manage standalone product.
</p>
</li>
<li class="listitem">
<p>
<span class="bold">
<strong>
A large amount of contributed MySQL
software is available.
</strong>
</span>
</p>
<p>
MySQL Server has a practical set of features developed in
close cooperation with our users. It is very likely that your
favorite application or language supports the MySQL Database
Server.
</p>
</li>
<li class="listitem">
<p>
<span class="bold">
<strong>
HeatWave.
</strong>
</span>
</p>
<p>
HeatWave is a fully managed database service, powered by the
HeatWave in-memory query accelerator. It is the only cloud
service that combines transactions, real-time analytics across
data warehouses and data lakes, and machine learning in one
MySQL Database; without the complexity, latency, risks, and
cost of ETL duplication. It is available on OCI, AWS, and
Azure. Learn more at:
<a class="ulink" href="https://www.oracle.com/mysql/" target="_blank">
https://www.oracle.com/mysql/
</a>
.
</p>
</li>
</ul>
</div>
<a class="indexterm" name="idm46045335209840">
</a>
<a class="indexterm" name="idm46045335208448">
</a>
<p>
The official way to pronounce
<span class="quote">
“
<span class="quote">
MySQL
</span>
”
</span>
is
<span class="quote">
“
<span class="quote">
My
Ess Que Ell
</span>
”
</span>
(not
<span class="quote">
“
<span class="quote">
my sequel
</span>
”
</span>
), but we do not
mind if you pronounce it as
<span class="quote">
“
<span class="quote">
my sequel
</span>
”
</span>
or in some
other localized way.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/charset-collate-precedence.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="charset-collate-precedence">
</a>
12.8.2 COLLATE Clause Precedence
</h3>
</div>
</div>
</div>
<p>
The
<code class="literal">
COLLATE
</code>
clause has high precedence
(higher than
<a class="link" href="logical-operators.html#operator_or">
<code class="literal">
||
</code>
</a>
), so
the following two expressions are equivalent:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa44055180"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql">x <span class="token operator">||</span> y <span class="token keyword">COLLATE</span> z
x <span class="token operator">||</span> <span class="token punctuation">(</span>y <span class="token keyword">COLLATE</span> z<span class="token punctuation">)</span></code></pre>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/data-masking-component-usage.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="data-masking-component-usage">
</a>
8.5.2.2 Using MySQL Enterprise Data Masking and De-Identification Components
</h4>
</div>
</div>
</div>
<p>
Before using MySQL Enterprise Data Masking and De-Identification, install it according to the instructions
provided at
<a class="xref" href="data-masking-components-installation.html" title="8.5.2.1 MySQL Enterprise Data Masking and De-Identification Component Installation">
Section 8.5.2.1, “MySQL Enterprise Data Masking and De-Identification Component Installation”
</a>
.
</p>
<p>
To use MySQL Enterprise Data Masking and De-Identification in applications, invoke the functions that are
appropriate for the operations you wish to perform. For detailed
function descriptions, see
<a class="xref" href="data-masking-component-functions.html" title="8.5.2.4 MySQL Enterprise Data Masking and De-Identification Component Function Descriptions">
Section 8.5.2.4, “MySQL Enterprise Data Masking and De-Identification Component Function Descriptions”
</a>
. This section
demonstrates how to use the functions to carry out some
representative tasks. It first presents an overview of the
available functions, followed by some examples of how the
functions might be used in real-world context:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<a class="xref" href="data-masking-component-usage.html#data-masking-component-usage-masking-functions" title="Masking Data to Remove Identifying Characteristics">
Masking Data to Remove Identifying Characteristics
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="data-masking-component-usage.html#data-masking-component-usage-generation-functions" title="Generating Random Data with Specific Characteristics">
Generating Random Data with Specific Characteristics
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="data-masking-component-usage.html#data-masking-component-usage-dictionary-functions" title="Generating Random Data Using Dictionaries">
Generating Random Data Using Dictionaries
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="data-masking-component-usage.html#data-masking-component-usage-customer-identification" title="Using Masked Data for Customer Identification">
Using Masked Data for Customer Identification
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="data-masking-component-usage.html#data-masking-component-usage-views" title="Creating Views that Display Masked Data">
Creating Views that Display Masked Data
</a>
</p>
</li>
</ul>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h5 class="title">
<a name="data-masking-component-usage-masking-functions">
</a>
Masking Data to Remove Identifying Characteristics
</h5>
</div>
</div>
</div>
<p>
MySQL provides general-purpose masking component functions
that mask arbitrary strings, and special-purpose masking
functions that mask specific types of values.
</p>
<h6>
<a name="idm46045233323296">
</a>
General-Purpose Masking Component Functions
</h6>
<p>
<a class="link" href="data-masking-component-functions.html#function_mask-inner">
<code class="literal">
mask_inner()
</code>
</a>
and
<a class="link" href="data-masking-component-functions.html#function_mask-outer">
<code class="literal">
mask_outer()
</code>
</a>
are
general-purpose functions that mask parts of arbitrary strings
based on position within the string. Both functions support an
input string that is encoded in any character set:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<a class="link" href="data-masking-component-functions.html#function_mask-inner">
<code class="literal">
mask_inner()
</code>
</a>
masks the
interior of its string argument, leaving the ends
unmasked. Other arguments specify the sizes of the
unmasked ends.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa81509850"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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> mask_inner<span class="token punctuation">(</span><span class="token string">'This is a string'</span><span class="token punctuation">,</span> <span class="token number">5</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"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><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> mask_inner('This is a string', 5, 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>
<span class="token output"><span class="token punctuation">|</span> This XXXXXXXXXXg <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>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> mask_inner<span class="token punctuation">(</span><span class="token string">'This is a string'</span><span class="token punctuation">,</span> <span class="token number">1</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 output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><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> mask_inner('This is a string', 1, 5) <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>
<span class="token output"><span class="token punctuation">|</span> TXXXXXXXXXXtring <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>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> mask_inner<span class="token punctuation">(</span><span class="token string">"かすみがうら市"</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>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><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> mask_inner("かすみがうら市", 3, 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 output"><span class="token punctuation">|</span> かすみXXX市 <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> mask_inner<span class="token punctuation">(</span><span class="token string">"かすみがうら市"</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 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> mask_inner("かすみがうら市", 1, 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>
<span class="token output"><span class="token punctuation">|</span> かXXXうら市 <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>
</li>
<li class="listitem">
<p>
<a class="link" href="data-masking-component-functions.html#function_mask-outer">
<code class="literal">
mask_outer()
</code>
</a>
does the
reverse, masking the ends of its string argument, leaving
the interior unmasked. Other arguments specify the sizes
of the masked ends.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa69751443"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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> mask_outer<span class="token punctuation">(</span><span class="token string">'This is a string'</span><span class="token punctuation">,</span> <span class="token number">5</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"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><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> mask_outer('This is a string', 5, 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>
<span class="token output"><span class="token punctuation">|</span> XXXXXis a strinX <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>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> mask_outer<span class="token punctuation">(</span><span class="token string">'This is a string'</span><span class="token punctuation">,</span> <span class="token number">1</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 output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><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> mask_outer('This is a string', 1, 5) <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>
<span class="token output"><span class="token punctuation">|</span> Xhis is a sXXXXX <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></code></pre>
</div>
</li>
</ul>
</div>
<p>
By default,
<a class="link" href="data-masking-component-functions.html#function_mask-inner">
<code class="literal">
mask_inner()
</code>
</a>
and
<a class="link" href="data-masking-component-functions.html#function_mask-outer">
<code class="literal">
mask_outer()
</code>
</a>
use
<code class="literal">
'X'
</code>
as the masking character, but permit an
optional masking-character argument:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa95533176"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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> mask_inner<span class="token punctuation">(</span><span class="token string">'This is a string'</span><span class="token punctuation">,</span> <span class="token number">5</span><span class="token punctuation">,</span> <span class="token number">1</span><span class="token punctuation">,</span> <span class="token string">'*'</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> mask_inner('This is a string', 5, 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>
<span class="token output"><span class="token punctuation">|</span> This **********g <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 prompt">mysql></span> <span class="token keyword">SELECT</span> mask_inner<span class="token punctuation">(</span><span class="token string">"かすみがうら市"</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 string">"#"</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> mask_inner("かすみがうら市", 2, 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 class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><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> かす###ら市 <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>
<h6>
<a name="idm46045233300832">
</a>
Special-Purpose Masking Component Functions
</h6>
<p>
Other masking functions expect a string argument representing
a specific type of value and mask it to remove identifying
characteristics.
</p>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
The examples here supply function arguments using the random
value generation functions that return the appropriate type
of value. For more information about generation functions,
see
<a class="xref" href="data-masking-component-usage.html#data-masking-component-usage-generation-functions" title="Generating Random Data with Specific Characteristics">
Generating Random Data with Specific Characteristics
</a>
.
</p>
</div>
<p>
<b>
Payment card Primary Account Number masking.
</b>
Masking functions provide strict and relaxed masking of
Primary Account numbers.
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<a class="link" href="data-masking-component-functions.html#function_mask-pan">
<code class="literal">
mask_pan()
</code>
</a>
masks all but
the last four digits of the number:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa4293434"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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> mask_pan<span class="token punctuation">(</span>gen_rnd_pan<span class="token punctuation">(</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>
<span class="token output"><span class="token punctuation">|</span> mask_pan(gen_rnd_pan()) <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> XXXXXXXXXXXX2461 <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></code></pre>
</div>
</li>
<li class="listitem">
<p>
<a class="link" href="data-masking-component-functions.html#function_mask-pan-relaxed">
<code class="literal">
mask_pan_relaxed()
</code>
</a>
is
similar but does not mask the first six digits that
indicate the payment card issuer unmasked:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa70648090"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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> mask_pan_relaxed<span class="token punctuation">(</span>gen_rnd_pan<span class="token punctuation">(</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>
<span class="token output"><span class="token punctuation">|</span> mask_pan_relaxed(gen_rnd_pan()) <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> 770630XXXXXX0807 <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>
</li>
</ul>
</div>
<p>
<b>
International Bank Account Number masking.
</b>
<a class="link" href="data-masking-component-functions.html#function_mask-iban">
<code class="literal">
mask_iban()
</code>
</a>
masks all but the
first two letters (denoting the country) of the number:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa75637073"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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> mask_iban<span class="token punctuation">(</span>gen_rnd_iban<span class="token punctuation">(</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>
<span class="token output"><span class="token punctuation">|</span> mask_iban(gen_rnd_iban()) <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> ZZ** **** **** **** <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>
<p>
<b>
Universally Unique Identifier masking.
</b>
<a class="link" href="data-masking-component-functions.html#function_mask-uuid">
<code class="literal">
mask_uuid()
</code>
</a>
masks all
meaningful characters:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa12906854"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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> mask_uuid<span class="token punctuation">(</span>gen_rnd_uuid<span class="token punctuation">(</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>
<span class="token output"><span class="token punctuation">|</span> mask_uuid(gen_rnd_uuid()) <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>
<span class="token output"><span class="token punctuation">|</span> ********<span class="token punctuation">-</span>****<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 class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="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>
<b>
US Social Security Number masking.
</b>
<a class="link" href="data-masking-component-functions.html#function_mask-ssn">
<code class="literal">
mask_ssn()
</code>
</a>
masks all but the
last four digits of the number:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa30701062"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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> mask_ssn<span class="token punctuation">(</span>gen_rnd_ssn<span class="token punctuation">(</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>
<span class="token output"><span class="token punctuation">|</span> mask_ssn(gen_rnd_ssn()) <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> ***<span class="token punctuation">-</span>**<span class="token punctuation">-</span>1723 <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></code></pre>
</div>
<p>
<b>
Canada Social Insurance Number masking.
</b>
<a class="link" href="data-masking-component-functions.html#function_mask-canada-sin">
<code class="literal">
mask_canada_sin()
</code>
</a>
masks
meaningful digits of the number:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa80948242"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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> mask_canada_sin<span class="token punctuation">(</span>gen_rnd_canada_sin<span class="token punctuation">(</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>
<span class="token output"><span class="token punctuation">|</span> mask_canada_sin(gen_rnd_canada_sin()) <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> XXX<span class="token punctuation">-</span>XXX<span class="token punctuation">-</span>XXX <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>
<b>
United Kingdom National Insurance Number masking.
</b>
<a class="link" href="data-masking-component-functions.html#function_mask-uk-nin">
<code class="literal">
mask_uk_nin()
</code>
</a>
masks all but
the first two digits of the number:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa80457322"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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> mask_uk_nin<span class="token punctuation">(</span>gen_rnd_uk_nin<span class="token punctuation">(</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>
<span class="token output"><span class="token punctuation">|</span> mask_uk_nin(gen_rnd_uk_nin()) <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> ZH******* <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>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h5 class="title">
<a name="data-masking-component-usage-generation-functions">
</a>
Generating Random Data with Specific Characteristics
</h5>
</div>
</div>
</div>
<p>
Several component functions generate random values. These
values can be used for testing, simulation, and so forth.
</p>
<p>
<a class="link" href="data-masking-component-functions.html#function_gen-range">
<code class="literal">
gen_range()
</code>
</a>
returns a random
integer selected from a given range:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa57113810"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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> gen_range<span class="token punctuation">(</span><span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">10</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>
<span class="token output"><span class="token punctuation">|</span> gen_range(1, 10) <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> 6 <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>
<a class="link" href="data-masking-component-functions.html#function_gen-rnd-canada-sin">
<code class="literal">
gen_rnd_canada_sin()
</code>
</a>
returns a
random number chosen from a range not used for legitimate
numbers:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa40422908"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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> gen_rnd_canada_sin<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 output"><span class="token punctuation">|</span> gen_rnd_canada_sin() <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></code></pre>
</div>
<p>
(The
<a class="link" href="data-masking-component-functions.html#function_gen-rnd-canada-sin">
<code class="literal">
gen_rnd_canada_sin()
</code>
</a>
function result is not shown because its return values should
be used only for testing purposes, and not for publication. It
cannot be guaranteed the number is not assigned to a
legitimate Canada SIN.)
</p>
<p>
<a class="link" href="data-masking-component-functions.html#function_gen-rnd-email">
<code class="literal">
gen_rnd_email()
</code>
</a>
returns a
random email address with a specified number of digits for the
name and surname parts in the specified domain,
<code class="literal">
mynet.com
</code>
in the following example:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa75070146"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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> gen_rnd_email<span class="token punctuation">(</span><span class="token number">6</span><span class="token punctuation">,</span> <span class="token number">8</span><span class="token punctuation">,</span> <span class="token string">'mynet.com'</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>
<span class="token output"><span class="token punctuation">|</span> gen_rnd_email(6, 8, 'mynet') <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> [email protected] <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>
<a class="link" href="data-masking-component-functions.html#function_gen-rnd-iban">
<code class="literal">
gen_rnd_iban()
</code>
</a>
returns a number
chosen from a range not used for legitimate numbers:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa18986257"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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> gen_rnd_iban<span class="token punctuation">(</span><span class="token string">'XO'</span><span class="token punctuation">,</span> <span class="token number">24</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> gen_rnd_iban('XO', 24) <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> XO25 SL7A PGQR B9NN 6IVB RFE8 <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>
<a class="link" href="data-masking-component-functions.html#function_gen-rnd-pan">
<code class="literal">
gen_rnd_pan()
</code>
</a>
returns a random
payment card Primary Account Number:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa89346959"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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> gen_rnd_pan<span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
(The
<a class="link" href="data-masking-component-functions.html#function_gen-rnd-pan">
<code class="literal">
gen_rnd_pan()
</code>
</a>
function
result is not shown because its return values should be used
only for testing purposes, and not for publication. It cannot
be guaranteed the number is not assigned to a legitimate
payment account.)
</p>
<p>
<a class="link" href="data-masking-component-functions.html#function_gen-rnd-ssn">
<code class="literal">
gen_rnd_ssn()
</code>
</a>
returns a random
US Social Security Number with the first and second parts each
chosen from a range not used for legitimate numbers:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa57669238"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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> gen_rnd_ssn<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>
<span class="token output"><span class="token punctuation">|</span> gen_rnd_ssn() <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> 912<span class="token punctuation">-</span>45<span class="token punctuation">-</span>1615 <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></code></pre>
</div>
<p>
<a class="link" href="data-masking-component-functions.html#function_gen-rnd-uk-nin">
<code class="literal">
gen_rnd_uk_nin()
</code>
</a>
returns a
number chosen from a range not used for legitimate numbers:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa56194675"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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> gen_rnd_uk_nin<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>
<span class="token output"><span class="token punctuation">|</span> gen_rnd_uk_nin() <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>
(The
<a class="link" href="data-masking-component-functions.html#function_gen-rnd-uk-nin">
<code class="literal">
gen_rnd_uk_nin()
</code>
</a>
function
result is not shown because its return values should be used
only for testing purposes, and not for publication. It cannot
be guaranteed the number is not assigned to a legitimate NIN.)
</p>
<p>
<a class="link" href="data-masking-component-functions.html#function_gen-rnd-us-phone">
<code class="literal">
gen_rnd_us_phone()
</code>
</a>
returns a
random US phone number in the 555 area code not used for
legitimate numbers:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa90673792"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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> gen_rnd_us_phone<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>
<span class="token output"><span class="token punctuation">|</span> gen_rnd_us_phone() <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> 1<span class="token punctuation">-</span>555<span class="token punctuation">-</span>747<span class="token punctuation">-</span>5627 <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>
<a class="link" href="data-masking-component-functions.html#function_gen-rnd-uuid">
<code class="literal">
gen_rnd_uuid()
</code>
</a>
returns a number
chosen from a range not used for legitimate identifiers:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa4891353"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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> gen_rnd_uuid<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>
<span class="token output"><span class="token punctuation">|</span> gen_rnd_uuid() <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>
<span class="token output"><span class="token punctuation">|</span> 68946384<span class="token punctuation">-</span>6880<span class="token punctuation">-</span>3150<span class="token punctuation">-</span>6889<span class="token punctuation">-</span>928076732539 <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></code></pre>
</div>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h5 class="title">
<a name="data-masking-component-usage-dictionary-functions">
</a>
Generating Random Data Using Dictionaries
</h5>
</div>
</div>
</div>
<p>
MySQL Enterprise Data Masking and De-Identification enables dictionaries to be used as sources of random
values called
<em class="firstterm">
terms
</em>
. To use a
dictionary, it must first be added to the
<code class="literal">
masking_dictionaries
</code>
system table and given
a name. The dictionaries are read from the table and loaded to
the cache during initialization of the components (on server
startup). Terms then can then be added, removed, and selected
from dictionaries and used as random values or as replacements
for other values.
</p>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
Always edit dictionaries using dictionary administration
functions rather than modifying the table directly. If you
manipulate the table manually, the dictionary cache becomes
inconsistent with the table.
</p>
</div>
<p>
A valid
<code class="literal">
masking_dictionaries
</code>
table has
these characteristics:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
An administrator created the
<code class="literal">
masking_dictionaries
</code>
system table in
the
<code class="literal">
mysql
</code>
schema as follows:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa7217062"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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 keyword">IF</span> <span class="token operator">NOT</span> <span class="token keyword">EXISTS</span>
masking_dictionaries<span class="token punctuation">(</span>
Dictionary <span class="token datatype">VARCHAR</span><span class="token punctuation">(</span><span class="token number">256</span><span class="token punctuation">)</span> <span class="token operator">NOT</span> <span class="token boolean">NULL</span><span class="token punctuation">,</span>
Term <span class="token datatype">VARCHAR</span><span class="token punctuation">(</span><span class="token number">256</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">UNIQUE</span> <span class="token keyword">INDEX</span> dictionary_term_idx <span class="token punctuation">(</span>Dictionary<span class="token punctuation">,</span> Term<span class="token punctuation">)</span><span class="token punctuation">,</span>
<span class="token keyword">INDEX</span> dictionary_idx <span class="token punctuation">(</span>Dictionary<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 keyword">DEFAULT</span> <span class="token keyword">CHARSET</span><span class="token operator">=</span>utf8mb4<span class="token punctuation">;</span></code></pre>
</div>
</li>
<li class="listitem">
<p>
MASKING_DICTIONARY_ADMIN privilege is required to add and
remove terms, or to remove an entire dictionary.
</p>
</li>
<li class="listitem">
<p>
The table may contain multiple dictionaries and their
terms.
</p>
</li>
<li class="listitem">
<p>
Any user account can view the dictionaries. Given enough
queries, all of the terms in dictionaries are retrievable.
Avoid adding sensitive data to the dictionary table.
</p>
</li>
</ul>
</div>
<p>
Suppose that a dictionary named
<code class="literal">
DE_cities
</code>
includes these city names in Germany:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-none"><div class="docs-select-all right" id="sa60778064"><div class="copy-help left">Press ⌘+C to 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">Berlin
Munich
Bremen</code></pre>
</div>
<p>
Use
<code class="literal">
masking_dictionary_term_add()
</code>
to assign
a dictionary name and one term:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa71294538"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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> masking_dictionary_term_add<span class="token punctuation">(</span><span class="token string">'DE_Cities'</span><span class="token punctuation">,</span> <span class="token string">'Berlin'</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>
<span class="token output"><span class="token punctuation">|</span> masking_dictionary_term_add('DE_Cities', 'Berlin') <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>
<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 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> masking_dictionary_term_add<span class="token punctuation">(</span><span class="token string">'DE_Cities'</span><span class="token punctuation">,</span> <span class="token string">'Munich'</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>
<span class="token output"><span class="token punctuation">|</span> masking_dictionary_term_add('DE_Cities', 'Munich') <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>
<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 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> masking_dictionary_term_add<span class="token punctuation">(</span><span class="token string">'DE_Cities'</span><span class="token punctuation">,</span> <span class="token string">'Bremen'</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>
<span class="token output"><span class="token punctuation">|</span> masking_dictionary_term_add('DE_Cities', 'Bremen') <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>
<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 class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
</div>
<p>
Also suppose that a dictionary named
<code class="literal">
US_Cities
</code>
contains these city names in the
United States:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-none"><div class="docs-select-all right" id="sa30569188"><div class="copy-help left">Press ⌘+C to 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">Houston
Phoenix
Detroit</code></pre>
</div>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa37607010"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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> masking_dictionary_term_add<span class="token punctuation">(</span><span class="token string">'US_Cities'</span><span class="token punctuation">,</span> <span class="token string">'Houston'</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>
<span class="token output"><span class="token punctuation">|</span> masking_dictionary_term_add('US_Cities', 'Houston') <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> 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 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> masking_dictionary_term_add<span class="token punctuation">(</span><span class="token string">'US_Cities'</span><span class="token punctuation">,</span> <span class="token string">'Phoenix'</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>
<span class="token output"><span class="token punctuation">|</span> masking_dictionary_term_add('US_Cities', 'Phoenix') <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> 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 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> masking_dictionary_term_add<span class="token punctuation">(</span><span class="token string">'US_Cities'</span><span class="token punctuation">,</span> <span class="token string">'Detroit'</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>
<span class="token output"><span class="token punctuation">|</span> masking_dictionary_term_add('US_Cities', 'Detroit') <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> 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 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 select a random term from a dictionary, use
<a class="link" href="data-masking-component-functions.html#function_gen-dictionary">
<code class="literal">
gen_dictionary()
</code>
</a>
:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa21028556"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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> gen_dictionary<span class="token punctuation">(</span><span class="token string">'DE_Cities'</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>
<span class="token output"><span class="token punctuation">|</span> gen_dictionary('DE_Cities') <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 output"><span class="token punctuation">|</span> Berlin <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 prompt">mysql></span> <span class="token keyword">SELECT</span> gen_dictionary<span class="token punctuation">(</span><span class="token string">'US_Cities'</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>
<span class="token output"><span class="token punctuation">|</span> gen_dictionary('US_Cities') <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 output"><span class="token punctuation">|</span> Phoenix <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></code></pre>
</div>
<p>
To select a random term from multiple dictionaries, randomly
select one of the dictionaries, then select a term from it:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa47222033"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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> gen_dictionary<span class="token punctuation">(</span><span class="token function">ELT</span><span class="token punctuation">(</span>gen_range<span class="token punctuation">(</span><span class="token number">1</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 string">'DE_Cities'</span><span class="token punctuation">,</span> <span class="token string">'US_Cities'</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 class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><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> gen_dictionary(ELT(gen_range(1,2), 'DE_Cities', 'US_Cities')) <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> Detroit <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 prompt">mysql></span> <span class="token keyword">SELECT</span> gen_dictionary<span class="token punctuation">(</span><span class="token function">ELT</span><span class="token punctuation">(</span>gen_range<span class="token punctuation">(</span><span class="token number">1</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 string">'DE_Cities'</span><span class="token punctuation">,</span> <span class="token string">'US_Cities'</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 class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><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> gen_dictionary(ELT(gen_range(1,2), 'DE_Cities', 'US_Cities')) <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> Bremen <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>
The
<a class="link" href="data-masking-component-functions.html#function_gen-blocklist">
<code class="literal">
gen_blocklist()
</code>
</a>
function
enables a term from one dictionary to be replaced by a term
from another dictionary, which effects masking by
substitution. Its arguments are the term to replace, the
dictionary in which the term appears, and the dictionary from
which to choose a replacement. For example, to substitute a US
city for a German city, or vice versa, use
<a class="link" href="data-masking-component-functions.html#function_gen-blocklist">
<code class="literal">
gen_blocklist()
</code>
</a>
like this:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa25691749"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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> gen_blocklist<span class="token punctuation">(</span><span class="token string">'Munich'</span><span class="token punctuation">,</span> <span class="token string">'DE_Cities'</span><span class="token punctuation">,</span> <span class="token string">'US_Cities'</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>
<span class="token output"><span class="token punctuation">|</span> gen_blocklist('Munich', 'DE_Cities', 'US_Cities') <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>
<span class="token output"><span class="token punctuation">|</span> Houston <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>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> gen_blocklist<span class="token punctuation">(</span><span class="token string">'El Paso'</span><span class="token punctuation">,</span> <span class="token string">'US_Cities'</span><span class="token punctuation">,</span> <span class="token string">'DE_Cities'</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>
<span class="token output"><span class="token punctuation">|</span> gen_blocklist('El Paso', 'US_Cities', 'DE_Cities') <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>
<span class="token output"><span class="token punctuation">|</span> Bremen <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></code></pre>
</div>
<p>
If the term to replace is not in the first dictionary,
<a class="link" href="data-masking-component-functions.html#function_gen-blocklist">
<code class="literal">
gen_blocklist()
</code>
</a>
returns it
unchanged:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa37627821"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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> gen_blocklist<span class="token punctuation">(</span><span class="token string">'Moscow'</span><span class="token punctuation">,</span> <span class="token string">'DE_Cities'</span><span class="token punctuation">,</span> <span class="token string">'US_Cities'</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>
<span class="token output"><span class="token punctuation">|</span> gen_blocklist('Moscow', 'DE_Cities', 'US_Cities') <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>
<span class="token output"><span class="token punctuation">|</span> Moscow <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></code></pre>
</div>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h5 class="title">
<a name="data-masking-component-usage-customer-identification">
</a>
Using Masked Data for Customer Identification
</h5>
</div>
</div>
</div>
<p>
At customer-service call centers, one common identity
verification technique is to ask customers to provide their
last four Social Security Number (SSN) digits. For example, a
customer might say her name is Joanna Bond and that her last
four SSN digits are
<code class="literal">
0007
</code>
.
</p>
<p>
Suppose that a
<code class="literal">
customer
</code>
table containing
customer records has these columns:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<code class="literal">
id
</code>
: Customer ID number.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
first_name
</code>
: Customer first name.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
last_name
</code>
: Customer last name.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
ssn
</code>
: Customer Social Security Number.
</p>
</li>
</ul>
</div>
<p>
For example, the table might be defined as follows:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa11295811"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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> customer
<span class="token punctuation">(</span>
id <span class="token datatype">BIGINT</span> <span class="token operator">NOT</span> <span class="token boolean">NULL</span> <span class="token keyword">AUTO_INCREMENT</span> <span class="token keyword">PRIMARY</span> <span class="token keyword">KEY</span><span class="token punctuation">,</span>
first_name <span class="token datatype">VARCHAR</span><span class="token punctuation">(</span><span class="token number">40</span><span class="token punctuation">)</span><span class="token punctuation">,</span>
last_name <span class="token datatype">VARCHAR</span><span class="token punctuation">(</span><span class="token number">40</span><span class="token punctuation">)</span><span class="token punctuation">,</span>
ssn <span class="token datatype">VARCHAR</span><span class="token punctuation">(</span><span class="token number">11</span><span class="token punctuation">)</span>
<span class="token punctuation">)</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
The application used by customer-service representatives to
check the customer SSN might execute a query like this:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa36494293"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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> ssn
<span class="token prompt">mysql></span> <span class="token keyword">FROM</span> customer
<span class="token prompt">mysql></span> <span class="token keyword">WHERE</span> first_name <span class="token operator">=</span> <span class="token string">'Joanna'</span> <span class="token operator">AND</span> last_name <span class="token operator">=</span> <span class="token string">'Bond'</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> id <span class="token punctuation">|</span> ssn <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> 786 <span class="token punctuation">|</span> 906<span class="token punctuation">-</span>39<span class="token punctuation">-</span>0007 <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></code></pre>
</div>
<p>
However, that exposes the SSN to the customer-service
representative, who has no need to see anything but the last
four digits. Instead, the application can use this query to
display only the masked SSN:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa60218643"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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> mask_ssn<span class="token punctuation">(</span><span class="token function">CONVERT</span><span class="token punctuation">(</span>ssn <span class="token keyword">USING</span> <span class="token datatype">binary</span><span class="token punctuation">)</span><span class="token punctuation">)</span> <span class="token keyword">AS</span> masked_ssn
<span class="token prompt">mysql></span> <span class="token keyword">FROM</span> customer
<span class="token prompt">mysql></span> <span class="token keyword">WHERE</span> first_name <span class="token operator">=</span> <span class="token string">'Joanna'</span> <span class="token operator">AND</span> last_name <span class="token operator">=</span> <span class="token string">'Bond'</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> id <span class="token punctuation">|</span> masked_ssn <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> 786 <span class="token punctuation">|</span> ***<span class="token punctuation">-</span>**<span class="token punctuation">-</span>0007 <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></code></pre>
</div>
<p>
Now the representative sees only what is necessary, and
customer privacy is preserved.
</p>
<p>
Why was the
<a class="link" href="cast-functions.html#function_convert">
<code class="literal">
CONVERT()
</code>
</a>
function
used for the argument to
<a class="link" href="data-masking-component-functions.html#function_mask-ssn">
<code class="literal">
mask_ssn()
</code>
</a>
? Because
<a class="link" href="data-masking-component-functions.html#function_mask-ssn">
<code class="literal">
mask_ssn()
</code>
</a>
requires an argument
of length 11. Thus, even though
<code class="literal">
ssn
</code>
is
defined as
<code class="literal">
VARCHAR(11)
</code>
, if the
<code class="literal">
ssn
</code>
column has a multibyte character set,
it may appear to be longer than 11 bytes when passed to a
loadable function, and returns
<code class="literal">
NULL
</code>
while
logging the error. Converting the value to a binary string
ensures that the function sees an argument of length 11.
</p>
<p>
A similar technique may be needed for other data masking
functions when string arguments do not have a single-byte
character set.
</p>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h5 class="title">
<a name="data-masking-component-usage-views">
</a>
Creating Views that Display Masked Data
</h5>
</div>
</div>
</div>
<p>
If masked data from a table is used for multiple queries, it
may be convenient to define a view that produces masked data.
That way, applications can select from the view without
performing masking in individual queries.
</p>
<p>
For example, a masking view on the
<code class="literal">
customer
</code>
table from the previous section can be defined like this:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa3461645"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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">VIEW</span> masked_customer <span class="token keyword">AS</span>
<span class="token keyword">SELECT</span> id<span class="token punctuation">,</span> first_name<span class="token punctuation">,</span> last_name<span class="token punctuation">,</span>
mask_ssn<span class="token punctuation">(</span><span class="token function">CONVERT</span><span class="token punctuation">(</span>ssn <span class="token keyword">USING</span> <span class="token datatype">binary</span><span class="token punctuation">)</span><span class="token punctuation">)</span> <span class="token keyword">AS</span> masked_ssn
<span class="token keyword">FROM</span> customer<span class="token punctuation">;</span></code></pre>
</div>
<p>
Then the query to look up a customer becomes simpler but still
returns masked data:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa56843925"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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> masked_ssn
<span class="token prompt">mysql></span> <span class="token keyword">FROM</span> masked_customer
<span class="token prompt">mysql></span> <span class="token keyword">WHERE</span> first_name <span class="token operator">=</span> <span class="token string">'Joanna'</span> <span class="token operator">AND</span> last_name <span class="token operator">=</span> <span class="token string">'Bond'</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> id <span class="token punctuation">|</span> masked_ssn <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> 786 <span class="token punctuation">|</span> ***<span class="token punctuation">-</span>**<span class="token punctuation">-</span>0007 <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></code></pre>
</div>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/replication-mode-change-online-concepts.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="replication-mode-change-online-concepts">
</a>
19.1.4.1 Replication Mode Concepts
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045145596608">
</a>
<p>
Before setting the replication mode of an online server, it is
important to understand some key concepts of replication. This
section explains these concepts and is essential reading before
attempting to modify the replication mode of an online server.
</p>
<p>
The modes of replication available in MySQL rely on different
techniques for identifying logged transactions. The types of
transactions used by replication are listed here:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
A GTID transaction is identified by a global transaction
identifier (GTID) which takes one of two forms:
<code class="literal">
UUID:NUMBER
</code>
or
<code class="literal">
UUID:TAG:NUMBER
</code>
. Every GTID transaction in
the binary log is preceded by a
<code class="literal">
Gtid_log_event
</code>
. A GTID transaction can be
addressed either by its GTID, or by the name of the file in
which it is logged and its position within that file.
</p>
</li>
<li class="listitem">
<p>
An anonymous transaction has no GTID; MySQL 8.4
ensures that every anonymous transaction in a log is preceded
by an
<code class="literal">
Anonymous_gtid_log_event
</code>
. (In old
versions of MySQL, an anonymous transaction was not preceded
by any particular event.) An anonymous transaction can be
addressed by file name and position only.
</p>
</li>
</ul>
</div>
<p>
When using GTIDs you can take advantage of GTID auto-positioning
and automatic failover, and use
<a class="link" href="gtid-functions.html#function_wait-for-executed-gtid-set">
<code class="literal">
WAIT_FOR_EXECUTED_GTID_SET()
</code>
</a>
,
<a class="link" href="server-system-variables.html#sysvar_session_track_gtids">
<code class="literal">
session_track_gtids
</code>
</a>
, and
Performance Schema tables to monitor replicated transactions (see
<a class="xref" href="performance-schema-replication-tables.html" title="29.12.11 Performance Schema Replication Tables">
Section 29.12.11, “Performance Schema Replication Tables”
</a>
).
</p>
<p>
A transaction in a relay log from a source running a previous
version of MySQL might not be preceded by any particular event,
but after being replayed and recorded in the replica's binary
log, it is preceded with an
<code class="literal">
Anonymous_gtid_log_event
</code>
.
</p>
<p>
To change the replication mode online, it is necessary to set the
<a class="link" href="replication-options-gtids.html#sysvar_gtid_mode">
<code class="literal">
gtid_mode
</code>
</a>
and
<a class="link" href="replication-options-gtids.html#sysvar_enforce_gtid_consistency">
<code class="literal">
enforce_gtid_consistency
</code>
</a>
variables using an account that has privileges sufficient to set
global system 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>
. Permitted values for
<a class="link" href="replication-options-gtids.html#sysvar_gtid_mode">
<code class="literal">
gtid_mode
</code>
</a>
are listed here, in
order, with their meanings:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<code class="literal">
OFF
</code>
: Only anonymous transactions can be
replicated.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
OFF_PERMISSIVE
</code>
: New transactions are
anonymous; replicated transactions may be either GTID or
anonymous.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
ON_PERMISSIVE
</code>
: New transactions use GTIDs;
replicated transactions may be either GTID or anonymous.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
ON
</code>
: All transaction must have GTIDs;
anonymous transactions cannot be replicated.
</p>
</li>
</ul>
</div>
<p>
It is possible to have servers using anonymous and servers using
GTID transactions in the same replication topology. For example, a
source where
<a class="link" href="replication-options-gtids.html#sysvar_gtid_mode">
<code class="literal">
gtid_mode=ON
</code>
</a>
can
replicate to a replica where
<a class="link" href="replication-options-gtids.html#sysvar_gtid_mode">
<code class="literal">
gtid_mode=ON_PERMISSIVE
</code>
</a>
.
</p>
<p>
Replication from a source using
<a class="link" href="replication-options-gtids.html#sysvar_gtid_mode">
<code class="literal">
gtid_mode=ON
</code>
</a>
provides the ability
to use GTID auto-positioning, configured using the
<a class="link" href="change-replication-source-to.html#crs-opt-source_auto_position">
<code class="literal">
SOURCE_AUTO_POSITION
</code>
</a>
option of
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 replication topology in use has an impact on
whether it is possible to enable auto-positioning or not, since
this feature relies on GTIDs and is not compatible with anonymous
transactions. It is strongly recommended to ensure there are no
anonymous transactions remaining in the topology before enabling
auto-positioning; see
<a class="xref" href="replication-mode-change-online-enable-gtids.html" title="19.1.4.2 Enabling GTID Transactions Online">
Section 19.1.4.2, “Enabling GTID Transactions Online”
</a>
.
</p>
<p>
Valid combinations of
<a class="link" href="replication-options-gtids.html#sysvar_gtid_mode">
<code class="literal">
gtid_mode
</code>
</a>
and auto-positioning on source and replica are shown in the next
table. The meaning of each entry is as follows:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<code class="literal">
Y
</code>
: The values of
<a class="link" href="replication-options-gtids.html#sysvar_gtid_mode">
<code class="literal">
gtid_mode
</code>
</a>
on the source and
on the replica are compatible.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
N
</code>
: The values of
<a class="link" href="replication-options-gtids.html#sysvar_gtid_mode">
<code class="literal">
gtid_mode
</code>
</a>
on the source and
on the replica are not compatible.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
*
</code>
: Auto-positioning can be used with this
combination of values.
</p>
</li>
</ul>
</div>
<div class="table">
<a name="idm46045145553584">
</a>
<p class="title">
<b>
Table 19.1 Valid Combinations of Source and Replica gtid_mode
</b>
</p>
<div class="table-contents">
<table summary="Explains compatible (Y) and incompatible (N) combinations of source and replica GTID mode. An asterisk (*) indicates that auto-positioning can be used with this combination of GTID modes.">
<colgroup>
<col style="width: 26%"/>
<col style="width: 12%"/>
<col style="width: 24%"/>
<col style="width: 24%"/>
<col style="width: 12%"/>
</colgroup>
<thead>
<tr>
<th scope="col">
<p>
<a class="link" href="replication-options-gtids.html#sysvar_gtid_mode">
<code class="literal">
gtid_mode
</code>
</a>
</p>
</th>
<th scope="col">
<p>
Source
<code class="literal">
OFF
</code>
</p>
</th>
<th scope="col">
<p>
Source
<code class="literal">
OFF_PERMISSIVE
</code>
</p>
</th>
<th scope="col">
<p>
Source
<code class="literal">
ON_PERMISSIVE
</code>
</p>
</th>
<th scope="col">
<p>
Source
<code class="literal">
ON
</code>
</p>
</th>
</tr>
</thead>
<tbody>
<tr>
<th scope="row">
<p>
Replica
<code class="literal">
OFF
</code>
</p>
</th>
<td>
<p>
Y
</p>
</td>
<td>
<p>
Y
</p>
</td>
<td>
<p>
N
</p>
</td>
<td>
<p>
N
</p>
</td>
</tr>
<tr>
<th scope="row">
<p>
Replica
<code class="literal">
OFF_PERMISSIVE
</code>
</p>
</th>
<td>
<p>
Y
</p>
</td>
<td>
<p>
Y
</p>
</td>
<td>
<p>
Y
</p>
</td>
<td>
<p>
Y*
</p>
</td>
</tr>
<tr>
<th scope="row">
<p>
Replica
<code class="literal">
ON_PERMISSIVE
</code>
</p>
</th>
<td>
<p>
Y
</p>
</td>
<td>
<p>
Y
</p>
</td>
<td>
<p>
Y
</p>
</td>
<td>
<p>
Y*
</p>
</td>
</tr>
<tr>
<th scope="row">
<p>
Replica
<code class="literal">
ON
</code>
</p>
</th>
<td>
<p>
N
</p>
</td>
<td>
<p>
N
</p>
</td>
<td>
<p>
Y
</p>
</td>
<td>
<p>
Y*
</p>
</td>
</tr>
</tbody>
</table>
</div>
</div>
<br class="table-break"/>
<p>
The current value of
<a class="link" href="replication-options-gtids.html#sysvar_gtid_mode">
<code class="literal">
gtid_mode
</code>
</a>
also affects
<a class="link" href="replication-options-gtids.html#sysvar_gtid_next">
<code class="literal">
gtid_next
</code>
</a>
. The next
table shows the behavior of the server for combinations of
different values of
<a class="link" href="replication-options-gtids.html#sysvar_gtid_mode">
<code class="literal">
gtid_mode
</code>
</a>
and
<a class="link" href="replication-options-gtids.html#sysvar_gtid_next">
<code class="literal">
gtid_next
</code>
</a>
. The meaning of each
entry is as follows:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<code class="literal">
ANONYMOUS
</code>
: Generate an anonymous
transaction.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
Error
</code>
: Generate an error, and do not
execute
<code class="literal">
SET GTID_NEXT
</code>
.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
UUID:NUMBER
</code>
: Generate a GTID with the
specified UUID:NUMBER.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
UUID:TAG:NUMBER
</code>
: Generate a GTID with the
specified UUID:TAG:NUMBER.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
New GTID
</code>
: Generate a GTID with an
automatically generated number.
</p>
</li>
</ul>
</div>
<div class="table">
<a name="idm46045145497024">
</a>
<p class="title">
<b>
Table 19.2 Valid Combinations of gtid_mode and gtid_next
</b>
</p>
<div class="table-contents">
<table summary="Explains the behavior for each of the possible combinations of GTID mode and setting for the gtid_next variable. With gtid_next set to AUTOMATIC, the behavior also varies depending on whether binary logging is enabled or disabled.">
<colgroup>
<col style="width:16%"/>
<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">
</th>
<th scope="col">
<code class="literal">
gtid_next
</code>
=
<code class="literal">
AUTOMATIC
</code>
(binary log
on)
</th>
<th scope="col">
<code class="literal">
gtid_next
</code>
=
<code class="literal">
AUTOMATIC
</code>
(binary log
off)
</th>
<th scope="col">
<code class="literal">
gtid_next
</code>
=
<code class="literal">
AUTOMATIC:<TAG>
</code>
</th>
<th scope="col">
<code class="literal">
gtid_next
</code>
=
<code class="literal">
ANONYMOUS
</code>
</th>
<th scope="col">
<code class="literal">
gtid_next
</code>
=
<code class="literal">
<UUID>:<NUMBER>
</code>
</th>
<th scope="col">
<code class="literal">
gtid_next
</code>
=
<code class="literal">
<UUID>:<TAG>:<NUMBER>
</code>
</th>
</tr>
</thead>
<tbody>
<tr>
<th scope="row">
<code class="literal">
gtid_mode
</code>
=
<code class="literal">
OFF
</code>
</th>
<td>
ANONYMOUS
</td>
<td>
ANONYMOUS
</td>
<td>
Error
</td>
<td>
ANONYMOUS
</td>
<td>
Error
</td>
<td>
Error
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
gtid_mode
</code>
=
<code class="literal">
OFF_PERMISSIVE
</code>
</th>
<td>
ANONYMOUS
</td>
<td>
ANONYMOUS
</td>
<td>
Error
</td>
<td>
ANONYMOUS
</td>
<td>
<UUID>:<NUMBER>
</td>
<td>
<UUID>:<TAG>:<NUMBER>
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
gtid_mode
</code>
=
<code class="literal">
ON_PERMISSIVE
</code>
</th>
<td>
New GTID
</td>
<td>
ANONYMOUS
</td>
<td>
New GTID
</td>
<td>
ANONYMOUS
</td>
<td>
<UUID>:<NUMBER>
</td>
<td>
<UUID>:<TAG>:<NUMBER>
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
gtid_mode
</code>
=
<code class="literal">
ON
</code>
</th>
<td>
New GTID
</td>
<td>
ANONYMOUS
</td>
<td>
New GTID
</td>
<td>
Error
</td>
<td>
<UUID>:<NUMBER>
</td>
<td>
<UUID>:<TAG>:<NUMBER>
</td>
</tr>
</tbody>
</table>
</div>
</div>
<br class="table-break"/>
<p>
When binary logging is not in use and
<a class="link" href="replication-options-gtids.html#sysvar_gtid_next">
<code class="literal">
gtid_next
</code>
</a>
is
<code class="literal">
AUTOMATIC
</code>
, then no GTID is generated.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/drop-function.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="drop-function">
</a>
15.1.26 DROP FUNCTION Statement
</h3>
</div>
</div>
</div>
<p>
The
<a class="link" href="drop-function.html" title="15.1.26 DROP FUNCTION Statement">
<code class="literal">
DROP FUNCTION
</code>
</a>
statement is used
to drop stored functions and loadable functions:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
For information about dropping stored functions, see
<a class="xref" href="drop-procedure.html" title="15.1.29 DROP PROCEDURE and DROP FUNCTION Statements">
Section 15.1.29, “DROP PROCEDURE and DROP FUNCTION Statements”
</a>
.
</p>
</li>
<li class="listitem">
<p>
For information about dropping loadable functions, see
<a class="xref" href="drop-function-loadable.html" title="15.7.4.2 DROP FUNCTION Statement for Loadable Functions">
Section 15.7.4.2, “DROP FUNCTION Statement for Loadable Functions”
</a>
.
</p>
</li>
</ul>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/mysql-cluster-ps-tables.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="mysql-cluster-ps-tables">
</a>
25.6.19 NDB Cluster and the Performance Schema
</h3>
</div>
</div>
</div>
<a class="indexterm" name="idm46045087318608">
</a>
<a class="indexterm" name="idm46045087317152">
</a>
<p>
NDB provides information in the MySQL Performance Schema about
<code class="literal">
ndbcluster
</code>
plugin threads and instrumenting for
transaction batch memory. These features are described in greater
detail in the sections which follow.
</p>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h4 class="title">
<a name="mysql-cluster-plugin-threads">
</a>
ndbcluster Plugin Threads
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045087313184">
</a>
<p>
<code class="literal">
ndbcluster
</code>
plugin threads are visible in the
Performance Schema
<a class="link" href="performance-schema-threads-table.html" title="29.12.22.8 The threads Table">
<code class="literal">
threads
</code>
</a>
table,
as shown in the following query:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa57750451"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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> <span class="token keyword">type</span><span class="token punctuation">,</span> thread_id<span class="token punctuation">,</span> thread_os_id
<span class="token prompt"> -></span> <span class="token keyword">FROM</span> performance_schema<span class="token punctuation">.</span>threads
<span class="token prompt"> -></span> <span class="token keyword">WHERE</span> <span class="token keyword">name</span> <span class="token operator">LIKE</span> <span class="token string">'%ndbcluster%'</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><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><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> type <span class="token punctuation">|</span> thread_id <span class="token punctuation">|</span> thread_os_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 class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><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/ndbcluster/ndb_binlog <span class="token punctuation">|</span> BACKGROUND <span class="token punctuation">|</span> 30 <span class="token punctuation">|</span> 11980 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> thread/ndbcluster/ndb_index_stat <span class="token punctuation">|</span> BACKGROUND <span class="token punctuation">|</span> 31 <span class="token punctuation">|</span> 11981 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> thread/ndbcluster/ndb_metadata <span class="token punctuation">|</span> BACKGROUND <span class="token punctuation">|</span> 32 <span class="token punctuation">|</span> 11982 <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>
<p>
The
<code class="literal">
threads
</code>
table shows all three of the
threads listed here:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<code class="literal">
ndb_binlog
</code>
: Binary logging thread
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
ndb_index_stat
</code>
: Index statistics thread
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
ndb_metadata
</code>
: Metadata thread
</p>
</li>
</ul>
</div>
<p>
These threads are also shown by name in the
<a class="link" href="performance-schema-setup-threads-table.html" title="29.12.2.5 The setup_threads Table">
<code class="literal">
setup_threads
</code>
</a>
table.
</p>
<p>
Thread names are shown in the
<code class="literal">
name
</code>
column of
the
<code class="literal">
threads
</code>
and
<code class="literal">
setup_threads
</code>
tables using the format
<code class="literal">
<em class="replaceable">
<code>
prefix
</code>
</em>
/
<em class="replaceable">
<code>
plugin_name
</code>
</em>
/
<em class="replaceable">
<code>
thread_name
</code>
</em>
</code>
.
<em class="replaceable">
<code>
prefix
</code>
</em>
, the object type as determined
by the
<a class="link" href="performance-schema.html" title="Chapter 29 MySQL Performance Schema">
<code class="literal">
performance_schema
</code>
</a>
engine,
is
<code class="literal">
thread
</code>
for plugin threads (see
<a class="xref" href="performance-schema-instrument-naming.html#performance-schema-thread-instrument-elements" title="Thread Instrument Elements">
Thread Instrument Elements
</a>
).
The
<em class="replaceable">
<code>
plugin_name
</code>
</em>
is
<code class="literal">
ndbcluster
</code>
.
<em class="replaceable">
<code>
thread_name
</code>
</em>
is the standalone name of
the thread (
<code class="literal">
ndb_binlog
</code>
,
<code class="literal">
ndb_index_stat
</code>
, or
<code class="literal">
ndb_metadata
</code>
).
</p>
<p>
Using the thread ID or OS thread ID for a given thread in the
<code class="literal">
threads
</code>
or
<code class="literal">
setup_threads
</code>
table, it is possible to obtain considerable information from
Performance Schema about plugin execution and resource usage.
This example shows how to obtain the amount of memory allocated
by the threads created by the
<code class="literal">
ndbcluster
</code>
plugin from the
<code class="literal">
mem_root
</code>
arena by joining the
<code class="literal">
threads
</code>
and
<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>
tables:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa3272820"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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 prompt"> -></span> t<span class="token punctuation">.</span><span class="token keyword">name</span><span class="token punctuation">,</span>
<span class="token prompt"> -></span> m<span class="token punctuation">.</span>sum_number_of_bytes_alloc<span class="token punctuation">,</span>
<span class="token prompt"> -></span> <span class="token function">IF</span><span class="token punctuation">(</span>m<span class="token punctuation">.</span>sum_number_of_bytes_alloc <span class="token operator">></span> <span class="token number">0</span><span class="token punctuation">,</span> <span class="token string">"true"</span><span class="token punctuation">,</span> <span class="token string">"false"</span><span class="token punctuation">)</span> <span class="token keyword">AS</span> <span class="token string">'Has allocated memory'</span>
<span class="token prompt"> -></span> <span class="token keyword">FROM</span> performance_schema<span class="token punctuation">.</span>memory_summary_by_thread_by_event_name m
<span class="token prompt"> -></span> <span class="token keyword">JOIN</span> performance_schema<span class="token punctuation">.</span>threads t
<span class="token prompt"> -></span> <span class="token keyword">ON</span> m<span class="token punctuation">.</span>thread_id <span class="token operator">=</span> t<span class="token punctuation">.</span>thread_id
<span class="token prompt"> -></span> <span class="token keyword">WHERE</span> t<span class="token punctuation">.</span><span class="token keyword">name</span> <span class="token operator">LIKE</span> <span class="token string">'%ndbcluster%'</span>
<span class="token prompt"> -></span> <span class="token operator">AND</span> event_name <span class="token operator">LIKE</span> <span class="token string">'%THD::main_mem_root%'</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>
<span class="token output"><span class="token punctuation">|</span> name <span class="token punctuation">|</span> sum_number_of_bytes_alloc <span class="token punctuation">|</span> Has allocated memory <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>
<span class="token output"><span class="token punctuation">|</span> thread/ndbcluster/ndb_binlog <span class="token punctuation">|</span> 20576 <span class="token punctuation">|</span> true <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> thread/ndbcluster/ndb_index_stat <span class="token punctuation">|</span> 0 <span class="token punctuation">|</span> false <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> thread/ndbcluster/ndb_metadata <span class="token punctuation">|</span> 8240 <span class="token punctuation">|</span> true <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></code></pre>
</div>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h4 class="title">
<a name="mysql-cluster-trx-batch-memory">
</a>
Transaction Memory Usage
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045087270560">
</a>
<p>
You can see the amount of memory used for transaction batching
by querying the Performance Schema
<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>
table, similar to what is shown here:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa38793028"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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> EVENT_NAME
<span class="token prompt"> -></span> <span class="token keyword">FROM</span> performance_schema<span class="token punctuation">.</span>memory_summary_by_thread_by_event_name
<span class="token prompt"> -></span> <span class="token keyword">WHERE</span> THREAD_ID <span class="token operator">=</span> PS_CURRENT_THREAD_ID<span class="token punctuation">(</span><span class="token punctuation">)</span>
<span class="token prompt"> -></span> <span class="token operator">AND</span> EVENT_NAME <span class="token operator">LIKE</span> <span class="token string">'memory/ndbcluster/%'</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> EVENT_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 class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><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> memory/ndbcluster/Thd_ndb::batch_mem_root <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">1 row in set (0.01 sec)</span></code></pre>
</div>
<p>
The
<code class="literal">
ndbcluster
</code>
transaction memory instrument
is also visible in the Performance Schema
<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, as shown
here:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa79911348"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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_instruments
<span class="token prompt"> -></span> <span class="token keyword">WHERE</span> <span class="token keyword">NAME</span> <span class="token operator">LIKE</span> <span class="token string">'%ndb%'</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>
NAME<span class="token punctuation">:</span> memory/ndbcluster/Thd_ndb<span class="token punctuation">:</span><span class="token punctuation">:</span>batch_mem_root
ENABLED<span class="token punctuation">:</span> YES
TIMED<span class="token punctuation">:</span> NULL
PROPERTIES<span class="token punctuation">:</span>
VOLATILITY<span class="token punctuation">:</span> 0
DOCUMENTATION<span class="token punctuation">:</span> Memory used for transaction batching
</span><span class="token output">1 row in set (0.01 sec)</span></code></pre>
</div>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/known-issues.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="known-issues">
</a>
B.3.7 Known Issues in MySQL
</h3>
</div>
</div>
</div>
<a class="indexterm" name="idm46045053320000">
</a>
<a class="indexterm" name="idm46045053318512">
</a>
<a class="indexterm" name="idm46045053317024">
</a>
<a class="indexterm" name="idm46045053315536">
</a>
<p>
This section lists known issues in recent versions of MySQL.
</p>
<p>
For information about platform-specific issues, see the
installation and debugging instructions in
<a class="xref" href="general-installation-issues.html" title="2.1 General Installation Guidance">
Section 2.1, “General Installation Guidance”
</a>
, and
<a class="xref" href="debugging-mysql.html" title="7.9 Debugging MySQL">
Section 7.9, “Debugging MySQL”
</a>
.
</p>
<p>
The following problems are known:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
Subquery optimization for
<code class="literal">
IN
</code>
is not as
effective as for
<code class="literal">
=
</code>
.
</p>
</li>
<li class="listitem">
<p>
Even if you use
<code class="literal">
lower_case_table_names=2
</code>
(which enables MySQL to remember the case used for databases
and table names), MySQL does not remember the case used for
database names for the function
<a class="link" href="information-functions.html#function_database">
<code class="literal">
DATABASE()
</code>
</a>
or within the
various logs (on case-insensitive systems).
</p>
</li>
<li class="listitem">
<p>
Dropping a
<code class="literal">
FOREIGN KEY
</code>
constraint does
not work in replication because the constraint may have
another name on the replica.
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="replace.html" title="15.2.12 REPLACE Statement">
<code class="literal">
REPLACE
</code>
</a>
(and
<a class="link" href="load-data.html" title="15.2.9 LOAD DATA Statement">
<code class="literal">
LOAD DATA
</code>
</a>
with the
<a class="link" href="replace.html" title="15.2.12 REPLACE Statement">
<code class="literal">
REPLACE
</code>
</a>
option) does not
trigger
<code class="literal">
ON DELETE CASCADE
</code>
.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
DISTINCT
</code>
with
<code class="literal">
ORDER BY
</code>
does not work inside
<a class="link" href="aggregate-functions.html#function_group-concat">
<code class="literal">
GROUP_CONCAT()
</code>
</a>
if you do not
use all and only those columns that are in the
<code class="literal">
DISTINCT
</code>
list.
</p>
</li>
<li class="listitem">
<p>
When inserting a big integer value (between
2
<sup>
63
</sup>
and
2
<sup>
64
</sup>
−1) into a decimal or
string column, it is inserted as a negative value because
the number is evaluated in signed integer context.
</p>
</li>
<li class="listitem">
<p>
With statement-based binary logging, the source server
writes the executed queries to the binary log. This is a
very fast, compact, and efficient logging method that works
perfectly in most cases. However, it is possible for the
data on the source and replica to become different if a
query is designed in such a way that the data modification
is nondeterministic (generally not a recommended practice,
even outside of replication).
</p>
<p>
For example:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
<a class="link" href="create-table-select.html" title="15.1.20.4 CREATE TABLE ... SELECT Statement">
<code class="literal">
CREATE
TABLE ... SELECT
</code>
</a>
or
<a class="link" href="insert-select.html" title="15.2.7.1 INSERT ... SELECT Statement">
<code class="literal">
INSERT
... SELECT
</code>
</a>
statements that insert zero or
<code class="literal">
NULL
</code>
values into an
<code class="literal">
AUTO_INCREMENT
</code>
column.
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="delete.html" title="15.2.2 DELETE Statement">
<code class="literal">
DELETE
</code>
</a>
if you are
deleting rows from a table that has foreign keys with
<code class="literal">
ON DELETE CASCADE
</code>
properties.
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="replace.html" title="15.2.12 REPLACE Statement">
<code class="literal">
REPLACE ...
SELECT
</code>
</a>
,
<code class="literal">
INSERT IGNORE ...
SELECT
</code>
if you have duplicate key values in the
inserted data.
</p>
</li>
</ul>
</div>
<p>
<span class="bold">
<strong>
If and only if the preceding queries
have no
<code class="literal">
ORDER BY
</code>
clause guaranteeing a
deterministic order
</strong>
</span>
.
</p>
<p>
For example, for
<a class="link" href="insert-select.html" title="15.2.7.1 INSERT ... SELECT Statement">
<code class="literal">
INSERT ...
SELECT
</code>
</a>
with no
<code class="literal">
ORDER BY
</code>
, the
<a class="link" href="select.html" title="15.2.13 SELECT Statement">
<code class="literal">
SELECT
</code>
</a>
may return rows in a
different order (which results in a row having different
ranks, hence getting a different number in the
<code class="literal">
AUTO_INCREMENT
</code>
column), depending on the
choices made by the optimizers on the source and replica.
</p>
<p>
A query is optimized differently on the source and replica
only if:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
The table is stored using a different storage engine on
the source than on the replica. (It is possible to use
different storage engines on the source and replica. For
example, you can use
<code class="literal">
InnoDB
</code>
on the
source, but
<code class="literal">
MyISAM
</code>
on the replica if
the replica has less available disk space.)
</p>
</li>
<li class="listitem">
<p>
MySQL buffer sizes
(
<a class="link" href="server-system-variables.html#sysvar_key_buffer_size">
<code class="literal">
key_buffer_size
</code>
</a>
, and
so on) are different on the source and replica.
</p>
</li>
<li class="listitem">
<p>
The source and replica run different MySQL versions, and
the optimizer code differs between these versions.
</p>
</li>
</ul>
</div>
<p>
This problem may also affect database restoration using
<span class="command">
<strong>
mysqlbinlog|mysql
</strong>
</span>
.
</p>
<p>
The easiest way to avoid this problem is to add an
<code class="literal">
ORDER BY
</code>
clause to the aforementioned
nondeterministic queries to ensure that the rows are always
stored or modified in the same order. Using row-based or
mixed logging format also avoids the problem.
</p>
</li>
<li class="listitem">
<p>
Log file names are based on the server host name if you do
not specify a file name with the startup option. To retain
the same log file names if you change your host name to
something else, you must explicitly use options such as
<a class="link" href="replication-options-binary-log.html#option_mysqld_log-bin">
<code class="option">
--log-bin=
<em class="replaceable">
<code>
old_host_name
</code>
</em>
-bin
</code>
</a>
.
See
<a class="xref" href="server-options.html" title="7.1.7 Server Command Options">
Section 7.1.7, “Server Command Options”
</a>
. Alternatively, rename
the old files to reflect your host name change. If these are
binary logs, you must edit the binary log index file and fix
the binary log file names there as well. (The same is true
for the relay logs on a replica.)
</p>
</li>
<li class="listitem">
<p>
<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>
does not delete temporary
files left after a
<a class="link" href="load-data.html" title="15.2.9 LOAD DATA Statement">
<code class="literal">
LOAD DATA
</code>
</a>
statement. See
<a class="xref" href="mysqlbinlog.html" title="6.6.9 mysqlbinlog — Utility for Processing Binary Log Files">
Section 6.6.9, “mysqlbinlog — Utility for Processing Binary Log Files”
</a>
.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
RENAME
</code>
does not work with
<code class="literal">
TEMPORARY
</code>
tables or tables used in a
<code class="literal">
MERGE
</code>
table.
</p>
</li>
<li class="listitem">
<p>
When using
<code class="literal">
SET CHARACTER SET
</code>
, you cannot
use translated characters in database, table, and column
names.
</p>
</li>
<li class="listitem">
<p>
The server uses only the first
<a class="link" href="server-system-variables.html#sysvar_max_sort_length">
<code class="literal">
max_sort_length
</code>
</a>
bytes when
comparing data values. This means that values cannot
reliably be used in
<code class="literal">
GROUP BY
</code>
,
<code class="literal">
ORDER BY
</code>
, or
<code class="literal">
DISTINCT
</code>
if they differ only after the first
<a class="link" href="server-system-variables.html#sysvar_max_sort_length">
<code class="literal">
max_sort_length
</code>
</a>
bytes. To
work around this, increase the variable value. The default
value of
<a class="link" href="server-system-variables.html#sysvar_max_sort_length">
<code class="literal">
max_sort_length
</code>
</a>
is
1024 and can be changed at server startup time or at
runtime.
</p>
</li>
<li class="listitem">
<p>
Numeric calculations are done with
<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>
or
<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>
(both are normally 64
bits long). Which precision you get depends on the function.
The general rule is that bit functions are performed with
<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>
precision,
<a class="link" href="flow-control-functions.html#function_if">
<code class="literal">
IF()
</code>
</a>
and
<a class="link" href="string-functions.html#function_elt">
<code class="literal">
ELT()
</code>
</a>
with
<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>
or
<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>
precision, and the
rest with
<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>
precision.
You should try to avoid using unsigned long long values if
they resolve to be larger than 63 bits (9223372036854775807)
for anything other than bit fields.
</p>
</li>
<li class="listitem">
<p>
You can have up to 255
<a class="link" href="enum.html" title="13.3.5 The ENUM Type">
<code class="literal">
ENUM
</code>
</a>
and
<a class="link" href="set.html" title="13.3.6 The SET Type">
<code class="literal">
SET
</code>
</a>
columns in one table.
</p>
</li>
<li class="listitem">
<p>
In
<a class="link" href="aggregate-functions.html#function_min">
<code class="literal">
MIN()
</code>
</a>
,
<a class="link" href="aggregate-functions.html#function_max">
<code class="literal">
MAX()
</code>
</a>
, and other aggregate
functions, MySQL currently compares
<a class="link" href="enum.html" title="13.3.5 The ENUM Type">
<code class="literal">
ENUM
</code>
</a>
and
<a class="link" href="set.html" title="13.3.6 The SET Type">
<code class="literal">
SET
</code>
</a>
columns by their string
value rather than by the string's relative position in the
set.
</p>
</li>
<li class="listitem">
<p>
In an
<a class="link" href="update.html" title="15.2.17 UPDATE Statement">
<code class="literal">
UPDATE
</code>
</a>
statement,
columns are updated from left to right. If you refer to an
updated column, you get the updated value instead of the
original value. For example, the following statement
increments
<code class="literal">
KEY
</code>
by
<code class="literal">
2
</code>
,
<span class="bold">
<strong>
not
</strong>
</span>
<code class="literal">
1
</code>
:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa80669013"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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> <em class="replaceable">tbl_name</em> <span class="token keyword">SET</span> <span class="token keyword">KEY</span><span class="token operator">=</span><span class="token keyword">KEY</span><span class="token operator">+</span><span class="token number">1</span><span class="token punctuation">,</span><span class="token keyword">KEY</span><span class="token operator">=</span><span class="token keyword">KEY</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>
You can refer to multiple temporary tables in the same
query, but you cannot refer to any given temporary table
more than once. For example, the following does not work:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa80698939"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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> temp_table<span class="token punctuation">,</span> temp_table <span class="token keyword">AS</span> t2<span class="token punctuation">;</span>
<span class="token output">ERROR 1137<span class="token punctuation">:</span> Can't reopen table<span class="token punctuation">:</span> 'temp_table'</span></code></pre>
</div>
</li>
<li class="listitem">
<p>
The optimizer may handle
<code class="literal">
DISTINCT
</code>
differently when you are using
<span class="quote">
“
<span class="quote">
hidden
</span>
”
</span>
columns
in a join than when you are not. In a join, hidden columns
are counted as part of the result (even if they are not
shown), whereas in normal queries, hidden columns do not
participate in the
<code class="literal">
DISTINCT
</code>
comparison.
</p>
<p>
An example of this is:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa51942486"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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">DISTINCT</span> mp3id <span class="token keyword">FROM</span> band_downloads
<span class="token keyword">WHERE</span> userid <span class="token operator">=</span> <span class="token number">9</span> <span class="token keyword">ORDER</span> <span class="token keyword">BY</span> id <span class="token keyword">DESC</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
and
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa59504686"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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">DISTINCT</span> band_downloads<span class="token punctuation">.</span>mp3id
<span class="token keyword">FROM</span> band_downloads<span class="token punctuation">,</span>band_mp3
<span class="token keyword">WHERE</span> band_downloads<span class="token punctuation">.</span>userid <span class="token operator">=</span> <span class="token number">9</span>
<span class="token operator">AND</span> band_mp3<span class="token punctuation">.</span>id <span class="token operator">=</span> band_downloads<span class="token punctuation">.</span>mp3id
<span class="token keyword">ORDER</span> <span class="token keyword">BY</span> band_downloads<span class="token punctuation">.</span>id <span class="token keyword">DESC</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
In the second case, you may get two identical rows in the
result set (because the values in the hidden
<code class="literal">
id
</code>
column may differ).
</p>
<p>
Note that this happens only for queries that do not have the
<code class="literal">
ORDER BY
</code>
columns in the result.
</p>
</li>
<li class="listitem">
<p>
If you execute a
<code class="literal">
PROCEDURE
</code>
on a query
that returns an empty set, in some cases the
<code class="literal">
PROCEDURE
</code>
does not transform the columns.
</p>
</li>
<li class="listitem">
<p>
Creation of a table of type
<code class="literal">
MERGE
</code>
does
not check whether the underlying tables are compatible
types.
</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
</code>
</a>
to add
a
<code class="literal">
UNIQUE
</code>
index to a table used in a
<code class="literal">
MERGE
</code>
table and then add a normal index
on the
<code class="literal">
MERGE
</code>
table, the key order is
different for the tables if there was an old,
non-
<code class="literal">
UNIQUE
</code>
key in the table. This is
because
<a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement">
<code class="literal">
ALTER TABLE
</code>
</a>
puts
<code class="literal">
UNIQUE
</code>
indexes before normal indexes to
be able to detect duplicate keys as early as possible.
</p>
</li>
</ul>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/column-indexes.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="column-indexes">
</a>
10.3.5 Column Indexes
</h3>
</div>
</div>
</div>
<a class="indexterm" name="idm46045227471248">
</a>
<a class="indexterm" name="idm46045227469760">
</a>
<a class="indexterm" name="idm46045227468272">
</a>
<p>
The most common type of index involves a single column, storing
copies of the values from that column in a data structure,
allowing fast lookups for the rows with the corresponding column
values. The B-tree data structure lets the index quickly find a
specific value, a set of values, or a range of values,
corresponding to operators such as
<code class="literal">
=
</code>
,
<code class="literal">
>
</code>
,
<code class="literal">
≤
</code>
,
<code class="literal">
BETWEEN
</code>
,
<code class="literal">
IN
</code>
, and so on, in
a
<code class="literal">
WHERE
</code>
clause.
</p>
<p>
The maximum number of indexes per table and the maximum index
length is defined per storage engine. 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>
, and
<a class="xref" href="storage-engines.html" title="Chapter 18 Alternative Storage Engines">
Chapter 18,
<i>
Alternative Storage Engines
</i>
</a>
. All storage engines support
at least 16 indexes per table and a total index length of at
least 256 bytes. Most storage engines have higher limits.
</p>
<p>
For additional information about column indexes, see
<a class="xref" href="create-index.html" title="15.1.15 CREATE INDEX Statement">
Section 15.1.15, “CREATE INDEX Statement”
</a>
.
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<a class="xref" href="column-indexes.html#column-indexes-prefix" title="Index Prefixes">
Index Prefixes
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="column-indexes.html#column-indexes-fulltext" title="FULLTEXT Indexes">
FULLTEXT Indexes
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="column-indexes.html#column-indexes-spatial" title="Spatial Indexes">
Spatial Indexes
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="column-indexes.html#column-indexes-memory-storage-engine" title="Indexes in the MEMORY Storage Engine">
Indexes in the MEMORY Storage Engine
</a>
</p>
</li>
</ul>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h4 class="title">
<a name="column-indexes-prefix">
</a>
Index Prefixes
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045227453408">
</a>
<a class="indexterm" name="idm46045227451920">
</a>
<a class="indexterm" name="idm46045227450432">
</a>
<a class="indexterm" name="idm46045227448944">
</a>
<a class="indexterm" name="idm46045227447456">
</a>
<p>
With
<code class="literal">
<em class="replaceable">
<code>
col_name
</code>
</em>
(
<em class="replaceable">
<code>
N
</code>
</em>
)
</code>
syntax in an index specification for a string column, you can
create an index that uses only the first
<em class="replaceable">
<code>
N
</code>
</em>
characters of the column.
Indexing only a prefix of column values in this way can make
the index file much smaller. When you index a
<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>
column, you
<span class="emphasis">
<em>
must
</em>
</span>
specify a prefix length for the
index. For example:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa39375566"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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>blob_col <span class="token datatype">BLOB</span><span class="token punctuation">,</span> <span class="token keyword">INDEX</span><span class="token punctuation">(</span>blob_col<span class="token punctuation">(</span><span class="token number">10</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
Prefixes can be up to 767 bytes long for
<code class="literal">
InnoDB
</code>
tables that use the
<code class="literal">
<a class="link" href="glossary.html#glos_redundant_row_format" title="redundant row format">
REDUNDANT
</a>
</code>
or
<code class="literal">
<a class="link" href="glossary.html#glos_compact_row_format" title="compact row format">
COMPACT
</a>
</code>
row format. The prefix length limit is 3072 bytes for
<code class="literal">
InnoDB
</code>
tables that use the
<code class="literal">
<a class="link" href="glossary.html#glos_dynamic_row_format" title="dynamic row format">
DYNAMIC
</a>
</code>
or
<code class="literal">
<a class="link" href="glossary.html#glos_compressed_row_format" title="compressed row format">
COMPRESSED
</a>
</code>
row format. For MyISAM tables, the prefix length limit is 1000
bytes.
</p>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
Prefix limits are measured in bytes, whereas the prefix
length in
<a class="link" href="create-table.html" title="15.1.20 CREATE TABLE Statement">
<code class="literal">
CREATE TABLE
</code>
</a>
,
<a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement">
<code class="literal">
ALTER TABLE
</code>
</a>
, and
<a class="link" href="create-index.html" title="15.1.15 CREATE INDEX Statement">
<code class="literal">
CREATE INDEX
</code>
</a>
statements is
interpreted as number of characters for nonbinary string
types (
<a class="link" href="char.html" title="13.3.2 The CHAR and VARCHAR Types">
<code class="literal">
CHAR
</code>
</a>
,
<a class="link" href="char.html" title="13.3.2 The CHAR and VARCHAR Types">
<code class="literal">
VARCHAR
</code>
</a>
,
<a class="link" href="blob.html" title="13.3.4 The BLOB and TEXT Types">
<code class="literal">
TEXT
</code>
</a>
) and number of bytes for
binary string types (
<a class="link" href="binary-varbinary.html" title="13.3.3 The BINARY and VARBINARY Types">
<code class="literal">
BINARY
</code>
</a>
,
<a class="link" href="binary-varbinary.html" title="13.3.3 The BINARY and VARBINARY Types">
<code class="literal">
VARBINARY
</code>
</a>
,
<a class="link" href="blob.html" title="13.3.4 The BLOB and TEXT Types">
<code class="literal">
BLOB
</code>
</a>
). Take this into account
when specifying a prefix length for a nonbinary string
column that uses a multibyte character set.
</p>
</div>
<p>
If a search term exceeds the index prefix length, the index is
used to exclude non-matching rows, and the remaining rows are
examined for possible matches.
</p>
<p>
For additional information about index prefixes, see
<a class="xref" href="create-index.html" title="15.1.15 CREATE INDEX Statement">
Section 15.1.15, “CREATE INDEX Statement”
</a>
.
</p>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h4 class="title">
<a name="column-indexes-fulltext">
</a>
FULLTEXT Indexes
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045227416720">
</a>
<a class="indexterm" name="idm46045227415232">
</a>
<p>
<code class="literal">
FULLTEXT
</code>
indexes are used for full-text
searches. Only the
<a class="link" href="innodb-storage-engine.html" title="Chapter 17 The InnoDB Storage Engine">
<code class="literal">
InnoDB
</code>
</a>
and
<a class="link" href="myisam-storage-engine.html" title="18.2 The MyISAM Storage Engine">
<code class="literal">
MyISAM
</code>
</a>
storage engines support
<code class="literal">
FULLTEXT
</code>
indexes and only for
<a class="link" href="char.html" title="13.3.2 The CHAR and VARCHAR Types">
<code class="literal">
CHAR
</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. Indexing always
takes place over the entire column and column prefix indexing
is not supported. For details, see
<a class="xref" href="fulltext-search.html" title="14.9 Full-Text Search Functions">
Section 14.9, “Full-Text Search Functions”
</a>
.
</p>
<p>
Optimizations are applied to certain kinds of
<code class="literal">
FULLTEXT
</code>
queries against single
<code class="literal">
InnoDB
</code>
tables. Queries with these
characteristics are particularly efficient:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<code class="literal">
FULLTEXT
</code>
queries that only return the
document ID, or the document ID and the search rank.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
FULLTEXT
</code>
queries that sort the matching
rows in descending order of score and apply a
<code class="literal">
LIMIT
</code>
clause to take the top N matching
rows. For this optimization to apply, there must be no
<code class="literal">
WHERE
</code>
clauses and only a single
<code class="literal">
ORDER BY
</code>
clause in descending order.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
FULLTEXT
</code>
queries that retrieve only the
<code class="literal">
COUNT(*)
</code>
value of rows matching a
search term, with no additional
<code class="literal">
WHERE
</code>
clauses. Code the
<code class="literal">
WHERE
</code>
clause as
<code class="literal">
WHERE MATCH(
<em class="replaceable">
<code>
text
</code>
</em>
)
AGAINST
('
<em class="replaceable">
<code>
other_text
</code>
</em>
')
</code>
,
without any
<code class="literal">
> 0
</code>
comparison operator.
</p>
</li>
</ul>
</div>
<p>
For queries that contain full-text expressions, MySQL
evaluates those expressions during the optimization phase of
query execution. The optimizer does not just look at full-text
expressions and make estimates, it actually evaluates them in
the process of developing an execution plan.
</p>
<p>
An implication of this behavior is that
<a class="link" href="explain.html" title="15.8.2 EXPLAIN Statement">
<code class="literal">
EXPLAIN
</code>
</a>
for full-text queries
is typically slower than for non-full-text queries for which
no expression evaluation occurs during the optimization phase.
</p>
<p>
<a class="link" href="explain.html" title="15.8.2 EXPLAIN Statement">
<code class="literal">
EXPLAIN
</code>
</a>
for full-text queries
may show
<code class="literal">
Select tables optimized away
</code>
in
the
<code class="literal">
Extra
</code>
column due to matching occurring
during optimization; in this case, no table access need occur
during later execution.
</p>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h4 class="title">
<a name="column-indexes-spatial">
</a>
Spatial Indexes
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045227383552">
</a>
<a class="indexterm" name="idm46045227382064">
</a>
<p>
You can create indexes on spatial data types.
<code class="literal">
MyISAM
</code>
and
<code class="literal">
InnoDB
</code>
support R-tree indexes on spatial types. Other storage engines
use B-trees for indexing spatial types (except for
<code class="literal">
ARCHIVE
</code>
, which does not support spatial
type indexing).
</p>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h4 class="title">
<a name="column-indexes-memory-storage-engine">
</a>
Indexes in the MEMORY Storage Engine
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045227376496">
</a>
<a class="indexterm" name="idm46045227375008">
</a>
<p>
The
<code class="literal">
MEMORY
</code>
storage engine uses
<code class="literal">
HASH
</code>
indexes by default, but also supports
<code class="literal">
BTREE
</code>
indexes.
</p>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/native-pluggable-authentication.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="native-pluggable-authentication">
</a>
8.4.1.1 Native Pluggable Authentication
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045246352832">
</a>
<a class="indexterm" name="idm46045246351728">
</a>
<p>
MySQL includes a
<code class="literal">
mysql_native_password
</code>
plugin
that implements native authentication; that is, authentication
based on the password hashing method in use from before the
introduction of pluggable authentication.
</p>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
The
<code class="literal">
mysql_native_password
</code>
authentication
plugin is deprecated as of MySQL 8.0.34, disabled by default
in MySQL 8.4, and removed as of MySQL 9.0.0.
</p>
</div>
<p>
The following table shows the plugin names on the server and
client sides.
</p>
<div class="table">
<a name="idm46045246346752">
</a>
<p class="title">
<b>
Table 8.14 Plugin and Library Names for Native Password Authentication
</b>
</p>
<div class="table-contents">
<table summary="Names for the plugins and library file used for native password authentication.">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<thead>
<tr>
<th>
Plugin or File
</th>
<th>
Plugin or File Name
</th>
</tr>
</thead>
<tbody>
<tr>
<td>
Server-side plugin
</td>
<td>
<code class="literal">
mysql_native_password
</code>
</td>
</tr>
<tr>
<td>
Client-side plugin
</td>
<td>
<code class="literal">
mysql_native_password
</code>
</td>
</tr>
<tr>
<td>
Library file
</td>
<td>
None (plugins are built in)
</td>
</tr>
</tbody>
</table>
</div>
</div>
<br class="table-break"/>
<p>
The following sections provide installation and usage
information specific to native pluggable authentication:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<a class="xref" href="native-pluggable-authentication.html#native-pluggable-authentication-installation" title="Installing Native Pluggable Authentication">
Installing Native Pluggable Authentication
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="native-pluggable-authentication.html#native-pluggable-authentication-usage" title="Using Native Pluggable Authentication">
Using Native Pluggable Authentication
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="native-pluggable-authentication.html#native-pluggable-authentication-disable" title="Disabling Native Pluggable Authentication">
Disabling Native Pluggable Authentication
</a>
</p>
</li>
</ul>
</div>
<p>
For general information about pluggable authentication in MySQL,
see
<a class="xref" href="pluggable-authentication.html" title="8.2.17 Pluggable Authentication">
Section 8.2.17, “Pluggable Authentication”
</a>
.
</p>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h5 class="title">
<a name="native-pluggable-authentication-installation">
</a>
Installing Native Pluggable Authentication
</h5>
</div>
</div>
</div>
<p>
The
<code class="literal">
mysql_native_password
</code>
plugin exists in
server and client forms:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
The server-side plugin is built into the server, but is
disabled by default. To enable it, start the MySQL Server
with
<a class="link" href="server-options.html#option_mysqld_mysql-native-password">
<code class="option">
--mysql-native-password=ON
</code>
</a>
or by including
<code class="literal">
mysql_native_password=ON
</code>
in the
<code class="literal">
[mysqld]
</code>
section of your MySQL
configuration file.
</p>
</li>
<li class="listitem">
<p>
The client-side plugin is built into the
<code class="literal">
libmysqlclient
</code>
client library and is
available to any program linked against
<code class="literal">
libmysqlclient
</code>
.
</p>
</li>
</ul>
</div>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h5 class="title">
<a name="native-pluggable-authentication-usage">
</a>
Using Native Pluggable Authentication
</h5>
</div>
</div>
</div>
<p>
MySQL client programs in MySQL 8.4 (and later)
use
<code class="literal">
caching_sha2_password
</code>
for
authentication by default. Use the
<a class="link" href="mysql-command-options.html#option_mysql_default-auth">
<code class="option">
--default-auth
</code>
</a>
option to set
<code class="literal">
mysql_native_password
</code>
as the default
client-side authentication plugin, if that is what is desired,
like this:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-terminal"><div class="docs-select-all right" id="sa32058230"><div class="copy-help left">Press ⌘+C to 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">$> </span><span class="token command">mysql</span> <span class="token constant">--default-auth</span><span class="token attr-value"><span class="token punctuation">=</span>mysql_native_password</span> <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span></code></pre>
</div>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h5 class="title">
<a name="native-pluggable-authentication-disable">
</a>
Disabling Native Pluggable Authentication
</h5>
</div>
</div>
</div>
<p>
In MySQL 8.4, the
<code class="literal">
mysql_native_password
</code>
server-side plugin is
disabled by default. To keep it disabled, be sure the server
is started without specifying the
<a class="link" href="server-options.html#option_mysqld_mysql-native-password">
<code class="option">
--mysql-native-password
</code>
</a>
option.
Using
<code class="option">
--mysql-native-password=OFF
</code>
also works
for this purpose, but is not required. In addition, do not
enable
<code class="literal">
mysql_native_password
</code>
in your MySQL
configuration file to keep it disabled.
</p>
<p>
When the plugin is disabled, all of the operations that depend
on the plugin are inaccessible. Specifically:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
Defined user accounts that authenticate with
<code class="literal">
mysql_native_password
</code>
encounter an
error when they attempt to connect.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-terminal"><div class="docs-select-all right" id="sa70983884"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-terminal"><span class="token prompt">$> </span><span class="token command">MYSQL</span> <span class="token property">-u</span> userx <span class="token property">-p</span>
<span class="token output">ERROR 1045 (28000)<span class="token punctuation">:</span> Access denied for user 'userx'@'localhost' (using password<span class="token punctuation">:</span> NO)</span></code></pre>
</div>
<p>
The server writes these errors to the server log.
</p>
</li>
<li class="listitem">
<p>
Attempts to create a new user account or to alter an
existing user account identified with
<code class="literal">
mysql_native_password
</code>
also fail and
emit an error.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa87460414"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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">USER</span> userxx<span class="token variable">@localhost</span> <span class="token keyword">IDENTIFIED</span> <span class="token keyword">WITH</span> <span class="token string">'mysql_native_password'</span><span class="token punctuation">;</span>
<span class="token output">ERROR 1524 (HY000)<span class="token punctuation">:</span> Plugin 'mysql_native_password' is not loaded</span>
<span class="token prompt">mysql></span> <span class="token keyword">ALTER</span> <span class="token keyword">USER</span> userxy<span class="token variable">@localhost</span> <span class="token keyword">IDENTIFIED</span> <span class="token keyword">WITH</span> <span class="token string">'mysql_native_password'</span><span class="token punctuation">;</span>
<span class="token output">ERROR 1524 (HY000)<span class="token punctuation">:</span> Plugin 'mysql_native_password' is not loaded</span></code></pre>
</div>
</li>
</ul>
</div>
<p>
For instructions on enabling the plugin, see
<a class="xref" href="native-pluggable-authentication.html#native-pluggable-authentication-installation" title="Installing Native Pluggable Authentication">
Installing Native Pluggable Authentication
</a>
.
</p>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/replication-gtids-lifecycle.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="replication-gtids-lifecycle">
</a>
19.1.3.2 GTID Life Cycle
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045146267120">
</a>
<p>
The life cycle of a GTID consists of the following steps:
</p>
<div class="orderedlist">
<ol class="orderedlist" type="1">
<li class="listitem">
<p>
A transaction is executed and committed on the source. This
client transaction is assigned a GTID composed of the source's
UUID and the smallest nonzero transaction sequence number not
yet used on this server. The GTID is written to the source's
binary log (immediately preceding the transaction itself in
the log). If a client transaction is not written to the binary
log (for example, because the transaction was filtered out, or
the transaction was read-only), it is not assigned a GTID.
</p>
</li>
<li class="listitem">
<p>
If a GTID was assigned for the transaction, the GTID is
persisted atomically at commit time by writing it to the
binary log at the beginning of the transaction (as a
<code class="literal">
Gtid_log_event
</code>
). Whenever the binary log is
rotated or the server is shut down, the server writes GTIDs
for all transactions that were written into the previous
binary log file into the
<code class="literal">
mysql.gtid_executed
</code>
table.
</p>
</li>
<li class="listitem">
<p>
If a GTID was assigned for the transaction, the GTID is
externalized non-atomically (very shortly after the
transaction is committed) by adding it to the set of GTIDs in
the
<a class="link" href="replication-options-gtids.html#sysvar_gtid_executed">
<code class="literal">
gtid_executed
</code>
</a>
system
variable (
<code class="literal">
@@GLOBAL.gtid_executed
</code>
). This
GTID set contains a representation of the set of all committed
GTID transactions, and it is used in replication as a token
that represents the server state. With binary logging enabled
(as required for the source), the set of GTIDs in the
<a class="link" href="replication-options-gtids.html#sysvar_gtid_executed">
<code class="literal">
gtid_executed
</code>
</a>
system variable
is a complete record of the transactions applied, but the
<code class="literal">
mysql.gtid_executed
</code>
table is not, because
the most recent history is still in the current binary log
file.
</p>
</li>
<li class="listitem">
<p>
After the binary log data is transmitted to the replica and
stored in the replica's relay log (using established
mechanisms for this process, see
<a class="xref" href="replication-implementation.html" title="19.2 Replication Implementation">
Section 19.2, “Replication Implementation”
</a>
, for details),
the replica reads the GTID and sets the value of its
<a class="link" href="replication-options-gtids.html#sysvar_gtid_next">
<code class="literal">
gtid_next
</code>
</a>
system variable as
this GTID. This tells the replica that the next transaction
must be logged using this GTID. It is important to note that
the replica sets
<code class="literal">
gtid_next
</code>
in a session
context.
</p>
</li>
<li class="listitem">
<p>
The replica verifies that no thread has yet taken ownership of
the GTID in
<a class="link" href="replication-options-gtids.html#sysvar_gtid_next">
<code class="literal">
gtid_next
</code>
</a>
in
order to process the transaction. By reading and checking the
replicated transaction's GTID first, before processing the
transaction itself, the replica guarantees not only that no
previous transaction having this GTID has been applied on the
replica, but also that no other session has already read this
GTID but has not yet committed the associated transaction. So
if multiple clients attempt to apply the same transaction
concurrently, the server resolves this by letting only one of
them execute. The
<a class="link" href="replication-options-gtids.html#sysvar_gtid_owned">
<code class="literal">
gtid_owned
</code>
</a>
system variable (
<code class="literal">
@@GLOBAL.gtid_owned
</code>
) for
the replica shows each GTID that is currently in use and the
ID of the thread that owns it. If the GTID has already been
used, no error is raised, and the auto-skip function is used
to ignore the transaction.
</p>
</li>
<li class="listitem">
<p>
If the GTID has not been used, the replica applies the
replicated transaction. Because
<a class="link" href="replication-options-gtids.html#sysvar_gtid_next">
<code class="literal">
gtid_next
</code>
</a>
is set to the GTID
already assigned by the source, the replica does not attempt
to generate a new GTID for this transaction, but instead uses
the GTID stored in
<a class="link" href="replication-options-gtids.html#sysvar_gtid_next">
<code class="literal">
gtid_next
</code>
</a>
.
</p>
</li>
<li class="listitem">
<p>
If binary logging is enabled on the replica, the GTID is
persisted atomically at commit time by writing it to the
binary log at the beginning of the transaction (as a
<code class="literal">
Gtid_log_event
</code>
). Whenever the binary log is
rotated or the server is shut down, the server writes GTIDs
for all transactions that were written into the previous
binary log file into the
<code class="literal">
mysql.gtid_executed
</code>
table.
</p>
</li>
<li class="listitem">
<p>
If binary logging is disabled on the replica, the GTID is
persisted atomically by writing it directly into the
<code class="literal">
mysql.gtid_executed
</code>
table. MySQL appends a
statement to the transaction to insert the GTID into the
table. This operation is atomic for DDL statements as well as
for DML statements. In this situation, the
<code class="literal">
mysql.gtid_executed
</code>
table is a complete
record of the transactions applied on the replica.
</p>
</li>
<li class="listitem">
<p>
Very shortly after the replicated transaction is committed on
the replica, the GTID is externalized non-atomically by adding
it to the set of GTIDs in the
<a class="link" href="replication-options-gtids.html#sysvar_gtid_executed">
<code class="literal">
gtid_executed
</code>
</a>
system variable
(
<code class="literal">
@@GLOBAL.gtid_executed
</code>
) for the replica.
As for the source, this GTID set contains a representation of
the set of all committed GTID transactions. If binary logging
is disabled on the replica, the
<code class="literal">
mysql.gtid_executed
</code>
table is also a
complete record of the transactions applied on the replica. If
binary logging is enabled on the replica, meaning that some
GTIDs are only recorded in the binary log, the set of GTIDs in
the
<a class="link" href="replication-options-gtids.html#sysvar_gtid_executed">
<code class="literal">
gtid_executed
</code>
</a>
system
variable is the only complete record.
</p>
</li>
</ol>
</div>
<p>
Client transactions that are completely filtered out on the source
are not assigned a GTID, therefore they are not added to the set
of transactions in the
<a class="link" href="replication-options-gtids.html#sysvar_gtid_executed">
<code class="literal">
gtid_executed
</code>
</a>
system variable, or
added to the
<code class="literal">
mysql.gtid_executed
</code>
table.
However, the GTIDs of replicated transactions that are completely
filtered out on the replica are persisted. If binary logging is
enabled on the replica, the filtered-out transaction is written to
the binary log as a
<code class="literal">
Gtid_log_event
</code>
followed by
an empty transaction containing only
<code class="literal">
BEGIN
</code>
and
<code class="literal">
COMMIT
</code>
statements. If binary logging is
disabled, the GTID of the filtered-out transaction is written to
the
<code class="literal">
mysql.gtid_executed
</code>
table. Preserving the
GTIDs for filtered-out transactions ensures that the
<code class="literal">
mysql.gtid_executed
</code>
table and the set of GTIDs
in the
<a class="link" href="replication-options-gtids.html#sysvar_gtid_executed">
<code class="literal">
gtid_executed
</code>
</a>
system
variable can be compressed. It also ensures that the filtered-out
transactions are not retrieved again if the replica reconnects to
the source, as explained in
<a class="xref" href="replication-gtids-auto-positioning.html" title="19.1.3.3 GTID Auto-Positioning">
Section 19.1.3.3, “GTID Auto-Positioning”
</a>
.
</p>
<p>
On a multithreaded replica (with
<a class="link" href="replication-options-replica.html#sysvar_replica_parallel_workers">
<code class="literal">
replica_parallel_workers > 0
</code>
</a>
),
transactions can be applied in parallel, so replicated
transactions can commit out of order (unless
<a class="link" href="replication-options-replica.html#sysvar_replica_preserve_commit_order">
<code class="literal">
replica_preserve_commit_order =
1
</code>
</a>
). When that happens, the set of GTIDs in the
<a class="link" href="replication-options-gtids.html#sysvar_gtid_executed">
<code class="literal">
gtid_executed
</code>
</a>
system variable
contains multiple GTID ranges with gaps between them. (On a source
or a single-threaded replica, there are monotonically increasing
GTIDs without gaps between the numbers.) Gaps on multithreaded
replicas only occur among the most recently applied transactions,
and are filled in as replication progresses. When replication
threads are stopped cleanly using the
<a class="link" href="stop-replica.html" title="15.4.2.5 STOP REPLICA Statement">
<code class="literal">
STOP
REPLICA
</code>
</a>
statement, ongoing transactions are applied so
that the gaps are filled in. In the event of a shutdown such as a
server failure or the use of the
<a class="link" href="kill.html" title="15.7.8.4 KILL Statement">
<code class="literal">
KILL
</code>
</a>
statement to stop replication
threads, the gaps might remain.
</p>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h5 class="title">
<a name="replication-gtids-assign">
</a>
What changes are assigned a GTID?
</h5>
</div>
</div>
</div>
<p>
The typical scenario is that the server generates a new GTID for
a committed transaction. However, GTIDs can also be assigned to
other changes besides transactions, and in some cases a single
transaction can be assigned multiple GTIDs.
</p>
<p>
Every database change (DDL or DML) that is written to the binary
log is assigned a GTID. This includes changes that are
autocommitted, and changes that are committed using
<code class="literal">
BEGIN
</code>
and
<code class="literal">
COMMIT
</code>
or
<code class="literal">
START TRANSACTION
</code>
statements. A GTID is also
assigned to the creation, alteration, or deletion of a database,
and of a non-table database object such as a procedure,
function, trigger, event, view, user, role, or grant.
</p>
<p>
Non-transactional updates as well as transactional updates are
assigned GTIDs. In addition, for a non-transactional update, if
a disk write failure occurs while attempting to write to the
binary log cache and a gap is therefore created in the binary
log, the resulting incident log event is assigned a GTID.
</p>
<p>
When a table is automatically dropped by a generated statement
in the binary log, a GTID is assigned to the statement.
Temporary tables are dropped automatically when a replica begins
to apply events from a source that has just been started, and
when statement-based replication is in use
(
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_format">
<code class="literal">
binlog_format=STATEMENT
</code>
</a>
) and a
user session that has open temporary tables disconnects. Tables
that use the
<a class="link" href="memory-storage-engine.html" title="18.3 The MEMORY Storage Engine">
<code class="literal">
MEMORY
</code>
</a>
storage engine
are deleted automatically the first time they are accessed after
the server is started, because rows might have been lost during
the shutdown.
</p>
<p>
When a transaction is not written to the binary log on the
server of origin, the server does not assign a GTID to it. This
includes transactions that are rolled back and transactions that
are executed while binary logging is disabled on the server of
origin, either globally (with
<code class="literal">
--skip-log-bin
</code>
specified in the server's configuration) or for the session
(
<code class="literal">
SET @@SESSION.sql_log_bin = 0
</code>
). This also
includes no-op transactions when row-based replication is in use
(
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_format">
<code class="literal">
binlog_format=ROW
</code>
</a>
).
</p>
<p>
XA transactions are assigned separate GTIDs for the
<code class="literal">
XA
PREPARE
</code>
phase of the transaction and the
<code class="literal">
XA
COMMIT
</code>
or
<code class="literal">
XA ROLLBACK
</code>
phase of the
transaction. XA transactions are persistently prepared so that
users can commit them or roll them back in the case of a failure
(which in a replication topology might include a failover to
another server). The two parts of the transaction are therefore
replicated separately, so they must have their own GTIDs, even
though a non-XA transaction that is rolled back would not have a
GTID.
</p>
<p>
In the following special cases, a single statement can generate
multiple transactions, and therefore be assigned multiple GTIDs:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
A stored procedure is invoked that commits multiple
transactions. One GTID is generated for each transaction
that the procedure commits.
</p>
</li>
<li class="listitem">
<p>
A multi-table
<a class="link" href="drop-table.html" title="15.1.32 DROP TABLE Statement">
<code class="literal">
DROP TABLE
</code>
</a>
statement drops tables of different types. Multiple GTIDs
can be generated if any of the tables use storage engines
that do not support atomic DDL, or if any of the tables are
temporary tables.
</p>
</li>
<li class="listitem">
<p>
A
<a class="link" href="create-table-select.html" title="15.1.20.4 CREATE TABLE ... SELECT Statement">
<code class="literal">
CREATE
TABLE ... SELECT
</code>
</a>
statement is issued when
row-based replication is in use
(
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_format">
<code class="literal">
binlog_format=ROW
</code>
</a>
). One
GTID is generated for the
<a class="link" href="create-table.html" title="15.1.20 CREATE TABLE Statement">
<code class="literal">
CREATE
TABLE
</code>
</a>
action and one GTID is generated for the
row-insert actions.
</p>
</li>
</ul>
</div>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h5 class="title">
<a name="replication-gtids-gtid-next">
</a>
The gtid_next System Variable
</h5>
</div>
</div>
</div>
<p>
By default, for new transactions committed in user sessions, the
server automatically generates and assigns a new GTID. When the
transaction is applied on a replica, the GTID from the server of
origin is preserved. You can change this behavior by setting the
session value of the
<a class="link" href="replication-options-gtids.html#sysvar_gtid_next">
<code class="literal">
gtid_next
</code>
</a>
system variable:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
When
<a class="link" href="replication-options-gtids.html#sysvar_gtid_next">
<code class="literal">
gtid_next
</code>
</a>
is set to
<code class="literal">
AUTOMATIC
</code>
(the default) and a transaction
is committed and written to the binary log, the server
automatically generates and assigns a new GTID. If a
transaction is rolled back or not written to the binary log
for another reason, the server does not generate and assign
a GTID.
</p>
</li>
<li class="listitem">
<p>
If you set
<a class="link" href="replication-options-gtids.html#sysvar_gtid_next">
<code class="literal">
gtid_next
</code>
</a>
to
<code class="literal">
AUTOMATIC:
<em class="replaceable">
<code>
TAG
</code>
</em>
</code>
,
a new GTID including the specified tag is assigned to each
new transaction.
</p>
</li>
<li class="listitem">
<p>
If you set
<a class="link" href="replication-options-gtids.html#sysvar_gtid_next">
<code class="literal">
gtid_next
</code>
</a>
to a
valid GTID (consisting of a UUID, an optional tag, and a
transaction sequence number, separated by a colon), the
server assigns that GTID to your transaction. This GTID is
assigned and added to
<a class="link" href="replication-options-gtids.html#sysvar_gtid_executed">
<code class="literal">
gtid_executed
</code>
</a>
even when the
transaction is not written to the binary log, or when the
transaction is empty.
</p>
</li>
</ul>
</div>
<p>
Note that after you set
<a class="link" href="replication-options-gtids.html#sysvar_gtid_next">
<code class="literal">
gtid_next
</code>
</a>
to a specific GTID
(in either
<code class="literal">
<em class="replaceable">
<code>
UUID
</code>
</em>
:
<em class="replaceable">
<code>
NUMBER
</code>
</em>
</code>
or
<code class="literal">
<em class="replaceable">
<code>
UUID
</code>
</em>
:
<em class="replaceable">
<code>
TAG
</code>
</em>
:
<em class="replaceable">
<code>
NUMBER
</code>
</em>
</code>
format), and the transaction has been committed or rolled back,
an explicit
<code class="literal">
SET @@SESSION.gtid_next
</code>
statement
must be issued before any other statement. You can use this to
set the GTID value back to
<code class="literal">
AUTOMATIC
</code>
if you
do not want to assign any more GTIDs explicitly.
</p>
<p>
When replication applier threads apply replicated transactions,
they use this technique, setting
<code class="literal">
@@SESSION.gtid_next
</code>
explicitly to the GTID of
the replicated transaction as assigned on the server of origin.
This means the GTID from the server of origin is retained,
rather than a new GTID being generated and assigned by the
replica. It also means the GTID is added to
<a class="link" href="replication-options-gtids.html#sysvar_gtid_executed">
<code class="literal">
gtid_executed
</code>
</a>
on the replica
even when binary logging or replica update logging is disabled
on the replica, or when the transaction is a no-op or is
filtered out on the replica.
</p>
<p>
It is possible for a client to simulate a replicated transaction
by setting
<code class="literal">
@@SESSION.gtid_next
</code>
to a specific
GTID before executing the transaction. This technique is used by
<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>
to generate a dump of the binary
log that the client can replay to preserve GTIDs. A simulated
replicated transaction committed through a client is completely
equivalent to a replicated transaction committed through a
replication applier thread, and they cannot be distinguished
after the fact.
</p>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h5 class="title">
<a name="replication-gtids-gtid-purged">
</a>
The
<code class="literal">
gtid_purged
</code>
System Variable
</h5>
</div>
</div>
</div>
<a class="indexterm" name="idm46045146162944">
</a>
<a class="indexterm" name="idm46045146161456">
</a>
<p>
The set of GTIDs in the
<a class="link" href="replication-options-gtids.html#sysvar_gtid_purged">
<code class="literal">
gtid_purged
</code>
</a>
system variable
(
<code class="literal">
@@GLOBAL.gtid_purged
</code>
) contains the GTIDs of
all the transactions that have been committed on the server, but
that do not exist in any binary log file on the server.
<a class="link" href="replication-options-gtids.html#sysvar_gtid_purged">
<code class="literal">
gtid_purged
</code>
</a>
is a subset of
<a class="link" href="replication-options-gtids.html#sysvar_gtid_executed">
<code class="literal">
gtid_executed
</code>
</a>
. The following
categories of GTIDs are in
<a class="link" href="replication-options-gtids.html#sysvar_gtid_purged">
<code class="literal">
gtid_purged
</code>
</a>
:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
GTIDs of replicated transactions that were committed with
binary logging disabled on the replica.
</p>
</li>
<li class="listitem">
<p>
GTIDs of transactions that were written to a binary log file
that has now been purged.
</p>
</li>
<li class="listitem">
<p>
GTIDs that were added explicitly to the set by the statement
<code class="literal">
SET @@GLOBAL.gtid_purged
</code>
.
</p>
</li>
</ul>
</div>
<p>
You can change the value of
<a class="link" href="replication-options-gtids.html#sysvar_gtid_purged">
<code class="literal">
gtid_purged
</code>
</a>
in order to record
on the server that the transactions in a certain GTID set have
been applied, although they do not exist in any binary log on
the server. When you add GTIDs to
<a class="link" href="replication-options-gtids.html#sysvar_gtid_purged">
<code class="literal">
gtid_purged
</code>
</a>
, they are also
added to
<a class="link" href="replication-options-gtids.html#sysvar_gtid_executed">
<code class="literal">
gtid_executed
</code>
</a>
. An
example use case for this action is when you are restoring a
backup of one or more databases on a server, but you do not have
the relevant binary logs containing the transactions on the
server. You can also choose whether to replace the whole GTID
set in
<a class="link" href="replication-options-gtids.html#sysvar_gtid_purged">
<code class="literal">
gtid_purged
</code>
</a>
with a
specified GTID set, or to add a specified GTID set to the GTIDs
already in
<a class="link" href="replication-options-gtids.html#sysvar_gtid_purged">
<code class="literal">
gtid_purged
</code>
</a>
. For
details of how to do this, see the description for
<a class="link" href="replication-options-gtids.html#sysvar_gtid_purged">
<code class="literal">
gtid_purged
</code>
</a>
.
</p>
<p>
The sets of GTIDs in the
<a class="link" href="replication-options-gtids.html#sysvar_gtid_executed">
<code class="literal">
gtid_executed
</code>
</a>
and
<a class="link" href="replication-options-gtids.html#sysvar_gtid_purged">
<code class="literal">
gtid_purged
</code>
</a>
system variables
are initialized when the server starts. Every binary log file
begins with the event
<code class="literal">
Previous_gtids_log_event
</code>
, which contains the
set of GTIDs in all previous binary log files (composed from the
GTIDs in the preceding file's
<code class="literal">
Previous_gtids_log_event
</code>
, and the GTIDs of
every
<code class="literal">
Gtid_log_event
</code>
in the preceding file
itself). The contents of
<code class="literal">
Previous_gtids_log_event
</code>
in the oldest and
most recent binary log files are used to compute the
<a class="link" href="replication-options-gtids.html#sysvar_gtid_executed">
<code class="literal">
gtid_executed
</code>
</a>
and
<a class="link" href="replication-options-gtids.html#sysvar_gtid_purged">
<code class="literal">
gtid_purged
</code>
</a>
sets at server
startup:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<a class="link" href="replication-options-gtids.html#sysvar_gtid_executed">
<code class="literal">
gtid_executed
</code>
</a>
is computed
as the union of the GTIDs in
<code class="literal">
Previous_gtids_log_event
</code>
in the most
recent binary log file, the GTIDs of transactions in that
binary log file, and the GTIDs stored in the
<code class="literal">
mysql.gtid_executed
</code>
table. This GTID set
contains all the GTIDs that have been used (or added
explicitly to
<a class="link" href="replication-options-gtids.html#sysvar_gtid_purged">
<code class="literal">
gtid_purged
</code>
</a>
)
on the server, whether or not they are currently in a binary
log file on the server. It does not include the GTIDs for
transactions that are currently being processed on the
server (
<code class="literal">
@@GLOBAL.gtid_owned
</code>
).
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="replication-options-gtids.html#sysvar_gtid_purged">
<code class="literal">
gtid_purged
</code>
</a>
is computed by
first adding the GTIDs in
<code class="literal">
Previous_gtids_log_event
</code>
in the most
recent binary log file and the GTIDs of transactions in that
binary log file. This step gives the set of GTIDs that are
currently, or were once, recorded in a binary log on the
server (
<code class="literal">
gtids_in_binlog
</code>
). Next, the GTIDs
in
<code class="literal">
Previous_gtids_log_event
</code>
in the oldest
binary log file are subtracted from
<code class="literal">
gtids_in_binlog
</code>
. This step gives the set
of GTIDs that are currently recorded in a binary log on the
server (
<code class="literal">
gtids_in_binlog_not_purged
</code>
).
Finally,
<code class="literal">
gtids_in_binlog_not_purged
</code>
is
subtracted from
<a class="link" href="replication-options-gtids.html#sysvar_gtid_executed">
<code class="literal">
gtid_executed
</code>
</a>
. The result
is the set of GTIDs that have been used on the server, but
are not currently recorded in a binary log file on the
server, and this result is used to initialize
<a class="link" href="replication-options-gtids.html#sysvar_gtid_purged">
<code class="literal">
gtid_purged
</code>
</a>
.
</p>
</li>
</ul>
</div>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h5 class="title">
<a name="replication-gtids-execution-history">
</a>
Resetting the GTID Execution History
</h5>
</div>
</div>
</div>
<p>
If you need to reset the GTID execution history on a server, use
the
<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>
statement. You might need to do this after carrying out test
queries to verify a replication setup on new GTID-enabled
servers, or when you want to join a new server to a replication
group but it contains some unwanted local transactions that are
not accepted by Group Replication.
</p>
<div class="warning" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Warning
</div>
<p>
Use
<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>
with caution to avoid losing any wanted GTID execution history
and binary log files.
</p>
</div>
<p>
Before issuing
<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>
, ensure that you have backups of the server's
binary log files and binary log index file, if any, and obtain
and save the GTID set held in the global value of the
<a class="link" href="replication-options-gtids.html#sysvar_gtid_executed">
<code class="literal">
gtid_executed
</code>
</a>
system variable
(for example, by issuing a
<code class="literal">
SELECT
@@GLOBAL.gtid_executed
</code>
statement and saving the
results). If you are removing unwanted transactions from that
GTID set, use
<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>
to examine the
contents of the transactions to ensure that they have no value,
contain no data that must be saved or replicated, and did not
result in data changes on the server.
</p>
<p>
When you issue
<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>
, the following reset operations are carried out:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
The value of the
<a class="link" href="replication-options-gtids.html#sysvar_gtid_purged">
<code class="literal">
gtid_purged
</code>
</a>
system variable
is set to an empty string (
<code class="literal">
''
</code>
).
</p>
</li>
<li class="listitem">
<p>
The global value (but not the session value) of the
<a class="link" href="replication-options-gtids.html#sysvar_gtid_executed">
<code class="literal">
gtid_executed
</code>
</a>
system
variable is set to an empty string.
</p>
</li>
<li class="listitem">
<p>
The
<code class="literal">
mysql.gtid_executed
</code>
table is cleared
(see
<a class="xref" href="replication-gtids-concepts.html#replication-gtids-gtid-executed-table" title="mysql.gtid_executed Table">
mysql.gtid_executed Table
</a>
).
</p>
</li>
<li class="listitem">
<p>
If the server has binary logging enabled, the existing
binary log files are deleted and the binary log index file
is cleared.
</p>
</li>
</ul>
</div>
<p>
Note that
<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>
is the method to reset the GTID execution
history even if the server is a replica where binary logging is
disabled.
<a class="link" href="reset-replica.html" title="15.4.2.3 RESET REPLICA Statement">
<code class="literal">
RESET REPLICA
</code>
</a>
has no
effect on the GTID execution history.
</p>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/switchable-optimizations.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="switchable-optimizations">
</a>
10.9.2 Switchable Optimizations
</h3>
</div>
</div>
</div>
<a class="indexterm" name="idm46045224519808">
</a>
<a class="indexterm" name="idm46045224518720">
</a>
<p>
The
<a class="link" href="server-system-variables.html#sysvar_optimizer_switch">
<code class="literal">
optimizer_switch
</code>
</a>
system
variable enables control over optimizer behavior. Its value is a
set of flags, each of which has a value of
<code class="literal">
on
</code>
or
<code class="literal">
off
</code>
to indicate whether the corresponding
optimizer behavior is enabled or disabled. This variable has
global and session values and can be changed at runtime. The
global default can be set at server startup.
</p>
<p>
To see the current set of optimizer flags, select the variable
value:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa65054569"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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">@@optimizer_switch</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>
@@optimizer_switch<span class="token punctuation">:</span> index_merge=on,index_merge_union=on,
index_merge_sort_union=on,index_merge_intersection=on,
engine_condition_pushdown=on,index_condition_pushdown=on,
mrr=on,mrr_cost_based=on,block_nested_loop=on,
batched_key_access=off,materialization=on,semijoin=on,
loosescan=on,firstmatch=on,duplicateweedout=on,
subquery_materialization_cost_based=on,
use_index_extensions=on,condition_fanout_filter=on,
derived_merge=on,use_invisible_indexes=off,skip_scan=on,
hash_join=on,subquery_to_derived=off,
prefer_ordering_index=on,hypergraph_optimizer=off,
derived_condition_pushdown=on,hash_set_operations=on
</span><span class="token output">1 row in set (0.00 sec)</span></code></pre>
</div>
<p>
To change the value of
<a class="link" href="server-system-variables.html#sysvar_optimizer_switch">
<code class="literal">
optimizer_switch
</code>
</a>
, assign a
value consisting of a comma-separated list of one or more
commands:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa42973806"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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> optimizer_switch<span class="token operator">=</span><span class="token string">'<em class="replaceable">command</em>[,<em class="replaceable">command</em>]...'</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
Each
<em class="replaceable">
<code>
command
</code>
</em>
value should have one of
the forms shown in the following table.
</p>
<div class="informaltable">
<table summary="The syntax of the command value for SET optimizer_switch commands.">
<colgroup>
<col style="width: 25%"/>
<col style="width: 75%"/>
</colgroup>
<thead>
<tr>
<th>
Command Syntax
</th>
<th>
Meaning
</th>
</tr>
</thead>
<tbody>
<tr>
<td>
<code class="literal">
default
</code>
</td>
<td>
Reset every optimization to its default value
</td>
</tr>
<tr>
<td>
<code class="literal">
<em class="replaceable">
<code>
opt_name
</code>
</em>
=default
</code>
</td>
<td>
Set the named optimization to its default value
</td>
</tr>
<tr>
<td>
<code class="literal">
<em class="replaceable">
<code>
opt_name
</code>
</em>
=off
</code>
</td>
<td>
Disable the named optimization
</td>
</tr>
<tr>
<td>
<code class="literal">
<em class="replaceable">
<code>
opt_name
</code>
</em>
=on
</code>
</td>
<td>
Enable the named optimization
</td>
</tr>
</tbody>
</table>
</div>
<p>
The order of the commands in the value does not matter, although
the
<code class="literal">
default
</code>
command is executed first if
present. Setting an
<em class="replaceable">
<code>
opt_name
</code>
</em>
flag to
<code class="literal">
default
</code>
sets it to whichever of
<code class="literal">
on
</code>
or
<code class="literal">
off
</code>
is its default
value. Specifying any given
<em class="replaceable">
<code>
opt_name
</code>
</em>
more than once in the value is not permitted and causes an
error. Any errors in the value cause the assignment to fail with
an error, leaving the value of
<a class="link" href="server-system-variables.html#sysvar_optimizer_switch">
<code class="literal">
optimizer_switch
</code>
</a>
unchanged.
</p>
<p>
The following list describes the permissible
<em class="replaceable">
<code>
opt_name
</code>
</em>
flag names, grouped by
optimization strategy:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
Batched Key Access Flags
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
<a name="optflag_batched-key-access">
</a>
<a class="link" href="switchable-optimizations.html#optflag_batched-key-access">
<code class="literal">
batched_key_access
</code>
</a>
(default
<code class="literal">
off
</code>
)
</p>
<p>
Controls use of BKA join algorithm.
</p>
</li>
</ul>
</div>
<p>
For
<a class="link" href="switchable-optimizations.html#optflag_batched-key-access">
<code class="literal">
batched_key_access
</code>
</a>
to
have any effect when set to
<code class="literal">
on
</code>
, the
<a class="link" href="switchable-optimizations.html#optflag_mrr">
<code class="literal">
mrr
</code>
</a>
flag must also be
<code class="literal">
on
</code>
. Currently, the cost estimation for
MRR is too pessimistic. Hence, it is also necessary for
<a class="link" href="switchable-optimizations.html#optflag_mrr-cost-based">
<code class="literal">
mrr_cost_based
</code>
</a>
to be
<code class="literal">
off
</code>
for BKA to be used.
</p>
<p>
For more information, see
<a class="xref" href="bnl-bka-optimization.html" title="10.2.1.12 Block Nested-Loop and Batched Key Access Joins">
Section 10.2.1.12, “Block Nested-Loop and Batched Key Access Joins”
</a>
.
</p>
</li>
<li class="listitem">
<p>
Block Nested-Loop Flags
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
<a name="optflag_block-nested-loop">
</a>
<a class="link" href="switchable-optimizations.html#optflag_block-nested-loop">
<code class="literal">
block_nested_loop
</code>
</a>
(default
<code class="literal">
on
</code>
)
</p>
<p>
Controls use of hash joins, as do the
<a class="link" href="optimizer-hints.html#optimizer-hints-table-level" title="Table-Level Optimizer Hints">
<code class="literal">
BNL
</code>
</a>
and
<a class="link" href="optimizer-hints.html#optimizer-hints-table-level" title="Table-Level Optimizer Hints">
<code class="literal">
NO_BNL
</code>
</a>
optimizer
hints.
</p>
</li>
</ul>
</div>
<p>
For more information, see
<a class="xref" href="bnl-bka-optimization.html" title="10.2.1.12 Block Nested-Loop and Batched Key Access Joins">
Section 10.2.1.12, “Block Nested-Loop and Batched Key Access Joins”
</a>
.
</p>
</li>
<li class="listitem">
<p>
Condition Filtering Flags
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
<a name="optflag_condition-fanout-filter">
</a>
<a class="link" href="switchable-optimizations.html#optflag_condition-fanout-filter">
<code class="literal">
condition_fanout_filter
</code>
</a>
(default
<code class="literal">
on
</code>
)
</p>
<p>
Controls use of condition filtering.
</p>
</li>
</ul>
</div>
<p>
For more information, see
<a class="xref" href="condition-filtering.html" title="10.2.1.13 Condition Filtering">
Section 10.2.1.13, “Condition Filtering”
</a>
.
</p>
</li>
<li class="listitem">
<p>
Derived Condition Pushdown Flags
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
<a name="optflag_derived-condition-pushdown">
</a>
<a class="link" href="switchable-optimizations.html#optflag_derived-condition-pushdown">
<code class="literal">
derived_condition_pushdown
</code>
</a>
(default
<code class="literal">
on
</code>
)
</p>
<p>
Controls derived condition pushdown.
</p>
</li>
</ul>
</div>
<p>
For more information, see
<a class="xref" href="derived-condition-pushdown-optimization.html" title="10.2.2.5 Derived Condition Pushdown Optimization">
Section 10.2.2.5, “Derived Condition Pushdown Optimization”
</a>
</p>
</li>
<li class="listitem">
<p>
Derived Table Merging Flags
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
<a name="optflag_derived-merge">
</a>
<a class="link" href="switchable-optimizations.html#optflag_derived-merge">
<code class="literal">
derived_merge
</code>
</a>
(default
<code class="literal">
on
</code>
)
</p>
<p>
Controls merging of derived tables and views into outer
query block.
</p>
</li>
</ul>
</div>
<p>
The
<a class="link" href="switchable-optimizations.html#optflag_derived-merge">
<code class="literal">
derived_merge
</code>
</a>
flag
controls whether the optimizer attempts to merge derived
tables, view references, and common table expressions into
the outer query block, assuming that no other rule prevents
merging; for example, an
<code class="literal">
ALGORITHM
</code>
directive for a view takes precedence over the
<a class="link" href="switchable-optimizations.html#optflag_derived-merge">
<code class="literal">
derived_merge
</code>
</a>
setting. By
default, the flag is
<code class="literal">
on
</code>
to enable
merging.
</p>
<p>
For more information, see
<a class="xref" href="derived-table-optimization.html" title="10.2.2.4 Optimizing Derived Tables, View References, and Common Table Expressions with Merging or Materialization">
Section 10.2.2.4, “Optimizing Derived Tables, View References, and Common Table Expressions
with Merging or Materialization”
</a>
.
</p>
</li>
<li class="listitem">
<p>
Engine Condition Pushdown Flags
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
<a name="optflag_engine-condition-pushdown">
</a>
<a class="link" href="switchable-optimizations.html#optflag_engine-condition-pushdown">
<code class="literal">
engine_condition_pushdown
</code>
</a>
(default
<code class="literal">
on
</code>
)
</p>
<p>
Controls engine condition pushdown.
</p>
</li>
</ul>
</div>
<p>
For more information, see
<a class="xref" href="engine-condition-pushdown-optimization.html" title="10.2.1.5 Engine Condition Pushdown Optimization">
Section 10.2.1.5, “Engine Condition Pushdown Optimization”
</a>
.
</p>
</li>
<li class="listitem">
<p>
Hash Join Flags
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
<a name="optflag_hash-join">
</a>
<a class="link" href="switchable-optimizations.html#optflag_hash-join">
<code class="literal">
hash_join
</code>
</a>
(default
<code class="literal">
on
</code>
)
</p>
<p>
Has no effect in MySQL 8.4. Use the
<a class="link" href="switchable-optimizations.html#optflag_block-nested-loop">
<code class="literal">
block_nested_loop
</code>
</a>
flag, instead.
</p>
</li>
</ul>
</div>
<p>
For more information, see
<a class="xref" href="hash-joins.html" title="10.2.1.4 Hash Join Optimization">
Section 10.2.1.4, “Hash Join Optimization”
</a>
.
</p>
</li>
<li class="listitem">
<p>
Index Condition Pushdown Flags
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
<a name="optflag_index-condition-pushdown">
</a>
<a class="link" href="switchable-optimizations.html#optflag_index-condition-pushdown">
<code class="literal">
index_condition_pushdown
</code>
</a>
(default
<code class="literal">
on
</code>
)
</p>
<p>
Controls index condition pushdown.
</p>
</li>
</ul>
</div>
<p>
For more information, see
<a class="xref" href="index-condition-pushdown-optimization.html" title="10.2.1.6 Index Condition Pushdown Optimization">
Section 10.2.1.6, “Index Condition Pushdown Optimization”
</a>
.
</p>
</li>
<li class="listitem">
<p>
Index Extensions Flags
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
<a name="optflag_use-index-extensions">
</a>
<a class="link" href="switchable-optimizations.html#optflag_use-index-extensions">
<code class="literal">
use_index_extensions
</code>
</a>
(default
<code class="literal">
on
</code>
)
</p>
<p>
Controls use of index extensions.
</p>
</li>
</ul>
</div>
<p>
For more information, see
<a class="xref" href="index-extensions.html" title="10.3.10 Use of Index Extensions">
Section 10.3.10, “Use of Index Extensions”
</a>
.
</p>
</li>
<li class="listitem">
<p>
Index Merge Flags
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
<a name="optflag_index-merge">
</a>
<a class="link" href="switchable-optimizations.html#optflag_index-merge">
<code class="literal">
index_merge
</code>
</a>
(default
<code class="literal">
on
</code>
)
</p>
<p>
Controls all Index Merge optimizations.
</p>
</li>
<li class="listitem">
<p>
<a name="optflag_index-merge-intersection">
</a>
<a class="link" href="switchable-optimizations.html#optflag_index-merge-intersection">
<code class="literal">
index_merge_intersection
</code>
</a>
(default
<code class="literal">
on
</code>
)
</p>
<p>
Controls the Index Merge Intersection Access
optimization.
</p>
</li>
<li class="listitem">
<p>
<a name="optflag_index-merge-sort-union">
</a>
<a class="link" href="switchable-optimizations.html#optflag_index-merge-sort-union">
<code class="literal">
index_merge_sort_union
</code>
</a>
(default
<code class="literal">
on
</code>
)
</p>
<p>
Controls the Index Merge Sort-Union Access optimization.
</p>
</li>
<li class="listitem">
<p>
<a name="optflag_index-merge-union">
</a>
<a class="link" href="switchable-optimizations.html#optflag_index-merge-union">
<code class="literal">
index_merge_union
</code>
</a>
(default
<code class="literal">
on
</code>
)
</p>
<p>
Controls the Index Merge Union Access optimization.
</p>
</li>
</ul>
</div>
<p>
For more information, see
<a class="xref" href="index-merge-optimization.html" title="10.2.1.3 Index Merge Optimization">
Section 10.2.1.3, “Index Merge Optimization”
</a>
.
</p>
</li>
<li class="listitem">
<p>
Index Visibility Flags
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
<a name="optflag_use-invisible-indexes">
</a>
<a class="link" href="switchable-optimizations.html#optflag_use-invisible-indexes">
<code class="literal">
use_invisible_indexes
</code>
</a>
(default
<code class="literal">
off
</code>
)
</p>
<p>
Controls use of invisible indexes.
</p>
</li>
</ul>
</div>
<p>
For more information, see
<a class="xref" href="invisible-indexes.html" title="10.3.12 Invisible Indexes">
Section 10.3.12, “Invisible Indexes”
</a>
.
</p>
</li>
<li class="listitem">
<p>
Limit Optimization Flags
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
<a name="optflag_prefer-ordering-index">
</a>
<a class="link" href="switchable-optimizations.html#optflag_prefer-ordering-index">
<code class="literal">
prefer_ordering_index
</code>
</a>
(default
<code class="literal">
on
</code>
)
</p>
<p>
Controls whether, in the case of a query having an
<code class="literal">
ORDER BY
</code>
or
<code class="literal">
GROUP
BY
</code>
with a
<code class="literal">
LIMIT
</code>
clause, the
optimizer tries to use an ordered index instead of an
unordered index, a filesort, or some other optimization.
This optimization is performed by default whenever the
optimizer determines that using it would allow for
faster execution of the query.
</p>
<p>
Because the algorithm that makes this determination
cannot handle every conceivable case (due in part to the
assumption that the distribution of data is always more
or less uniform), there are cases in which this
optimization may not be desirable. This optimization can
be disabled by setting the
<a class="link" href="switchable-optimizations.html#optflag_prefer-ordering-index">
<code class="literal">
prefer_ordering_index
</code>
</a>
flag to
<code class="literal">
off
</code>
.
</p>
</li>
</ul>
</div>
<p>
For more information and examples, see
<a class="xref" href="limit-optimization.html" title="10.2.1.19 LIMIT Query Optimization">
Section 10.2.1.19, “LIMIT Query Optimization”
</a>
.
</p>
</li>
<li class="listitem">
<p>
Multi-Range Read Flags
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
<a name="optflag_mrr">
</a>
<a class="link" href="switchable-optimizations.html#optflag_mrr">
<code class="literal">
mrr
</code>
</a>
(default
<code class="literal">
on
</code>
)
</p>
<p>
Controls the Multi-Range Read strategy.
</p>
</li>
<li class="listitem">
<p>
<a name="optflag_mrr-cost-based">
</a>
<a class="link" href="switchable-optimizations.html#optflag_mrr-cost-based">
<code class="literal">
mrr_cost_based
</code>
</a>
(default
<code class="literal">
on
</code>
)
</p>
<p>
Controls use of cost-based MRR if
<a class="link" href="switchable-optimizations.html#optflag_mrr">
<code class="literal">
mrr=on
</code>
</a>
.
</p>
</li>
</ul>
</div>
<p>
For more information, see
<a class="xref" href="mrr-optimization.html" title="10.2.1.11 Multi-Range Read Optimization">
Section 10.2.1.11, “Multi-Range Read Optimization”
</a>
.
</p>
</li>
<li class="listitem">
<p>
Semijoin Flags
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
<a name="optflag_duplicateweedout">
</a>
<a class="link" href="switchable-optimizations.html#optflag_duplicateweedout">
<code class="literal">
duplicateweedout
</code>
</a>
(default
<code class="literal">
on
</code>
)
</p>
<p>
Controls the semijoin Duplicate Weedout strategy.
</p>
</li>
<li class="listitem">
<p>
<a name="optflag_firstmatch">
</a>
<a class="link" href="switchable-optimizations.html#optflag_firstmatch">
<code class="literal">
firstmatch
</code>
</a>
(default
<code class="literal">
on
</code>
)
</p>
<p>
Controls the semijoin FirstMatch strategy.
</p>
</li>
<li class="listitem">
<p>
<a name="optflag_loosescan">
</a>
<a class="link" href="switchable-optimizations.html#optflag_loosescan">
<code class="literal">
loosescan
</code>
</a>
(default
<code class="literal">
on
</code>
)
</p>
<p>
Controls the semijoin LooseScan strategy (not to be
confused with Loose Index Scan for
<code class="literal">
GROUP
BY
</code>
).
</p>
</li>
<li class="listitem">
<p>
<a name="optflag_semijoin">
</a>
<a class="link" href="switchable-optimizations.html#optflag_semijoin">
<code class="literal">
semijoin
</code>
</a>
(default
<code class="literal">
on
</code>
)
</p>
<p>
Controls all semijoin strategies.
</p>
<p>
This also applies to the antijoin optimization.
</p>
</li>
</ul>
</div>
<p>
The
<a class="link" href="switchable-optimizations.html#optflag_semijoin">
<code class="literal">
semijoin
</code>
</a>
,
<a class="link" href="switchable-optimizations.html#optflag_firstmatch">
<code class="literal">
firstmatch
</code>
</a>
,
<a class="link" href="switchable-optimizations.html#optflag_loosescan">
<code class="literal">
loosescan
</code>
</a>
, and
<a class="link" href="switchable-optimizations.html#optflag_duplicateweedout">
<code class="literal">
duplicateweedout
</code>
</a>
flags
enable control over semijoin strategies. The
<a class="link" href="switchable-optimizations.html#optflag_semijoin">
<code class="literal">
semijoin
</code>
</a>
flag controls
whether semijoins are used. If it is set to
<code class="literal">
on
</code>
, the
<a class="link" href="switchable-optimizations.html#optflag_firstmatch">
<code class="literal">
firstmatch
</code>
</a>
and
<a class="link" href="switchable-optimizations.html#optflag_loosescan">
<code class="literal">
loosescan
</code>
</a>
flags enable
finer control over the permitted semijoin strategies.
</p>
<p>
If the
<a class="link" href="switchable-optimizations.html#optflag_duplicateweedout">
<code class="literal">
duplicateweedout
</code>
</a>
semijoin strategy is disabled, it is not used unless all
other applicable strategies are also disabled.
</p>
<p>
If
<a class="link" href="switchable-optimizations.html#optflag_semijoin">
<code class="literal">
semijoin
</code>
</a>
and
<a class="link" href="switchable-optimizations.html#optflag_materialization">
<code class="literal">
materialization
</code>
</a>
are both
<code class="literal">
on
</code>
, semijoins also use materialization
where applicable. These flags are
<code class="literal">
on
</code>
by
default.
</p>
<p>
For more information, see
<a class="ulink" href="/doc/refman/8.0/en/semijoins.html" target="_top">
Optimizing IN and EXISTS Subquery Predicates with Semijoin Transformations
</a>
.
</p>
</li>
<li class="listitem">
<p>
Set Operations Flags
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
<a name="optflag_hash-set-operations">
</a>
<a class="link" href="switchable-optimizations.html#optflag_hash-set-operations">
<code class="literal">
hash_set_operations
</code>
</a>
(default
<code class="literal">
on
</code>
)
</p>
<p>
Enables the hash table optimization for set operations
involving
<a class="link" href="except.html" title="15.2.4 EXCEPT Clause">
<code class="literal">
EXCEPT
</code>
</a>
and
<a class="link" href="intersect.html" title="15.2.8 INTERSECT Clause">
<code class="literal">
INTERSECT
</code>
</a>
); enabled by
default. Otherwise, temporary table based de-duplication
is used, as in previous versions of MySQL.
</p>
<p>
The amount of memory used for hashing by this
optimization can be controlled using the
<a class="link" href="server-system-variables.html#sysvar_set_operations_buffer_size">
<code class="literal">
set_operations_buffer_size
</code>
</a>
system variable; increasing this generally results in
faster execution times for statements using these
operations.
</p>
</li>
</ul>
</div>
</li>
<li class="listitem">
<p>
Skip Scan Flags
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
<a name="optflag_skip-scan">
</a>
<a class="link" href="switchable-optimizations.html#optflag_skip-scan">
<code class="literal">
skip_scan
</code>
</a>
(default
<code class="literal">
on
</code>
)
</p>
<p>
Controls use of Skip Scan access method.
</p>
</li>
</ul>
</div>
<p>
For more information, 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>
</li>
<li class="listitem">
<p>
Subquery Materialization Flags
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
<a name="optflag_materialization">
</a>
<a class="link" href="switchable-optimizations.html#optflag_materialization">
<code class="literal">
materialization
</code>
</a>
(default
<code class="literal">
on
</code>
)
</p>
<p>
Controls materialization (including semijoin
materialization).
</p>
</li>
<li class="listitem">
<p>
<a name="optflag_subquery-materialization-cost-based">
</a>
<a class="link" href="switchable-optimizations.html#optflag_subquery-materialization-cost-based">
<code class="literal">
subquery_materialization_cost_based
</code>
</a>
(default
<code class="literal">
on
</code>
)
</p>
<p>
Use cost-based materialization choice.
</p>
</li>
</ul>
</div>
<p>
The
<a class="link" href="switchable-optimizations.html#optflag_materialization">
<code class="literal">
materialization
</code>
</a>
flag
controls whether subquery materialization is used. If
<a class="link" href="switchable-optimizations.html#optflag_semijoin">
<code class="literal">
semijoin
</code>
</a>
and
<a class="link" href="switchable-optimizations.html#optflag_materialization">
<code class="literal">
materialization
</code>
</a>
are both
<code class="literal">
on
</code>
, semijoins also use materialization
where applicable. These flags are
<code class="literal">
on
</code>
by
default.
</p>
<p>
The
<a class="link" href="switchable-optimizations.html#optflag_subquery-materialization-cost-based">
<code class="literal">
subquery_materialization_cost_based
</code>
</a>
flag enables control over the choice between subquery
materialization and
<code class="literal">
IN
</code>
-to-
<code class="literal">
EXISTS
</code>
subquery
transformation. If the flag is
<code class="literal">
on
</code>
(the
default), the optimizer performs a cost-based choice between
subquery materialization and
<code class="literal">
IN
</code>
-to-
<code class="literal">
EXISTS
</code>
subquery
transformation if either method could be used. If the flag
is
<code class="literal">
off
</code>
, the optimizer chooses subquery
materialization over
<code class="literal">
IN
</code>
-to-
<code class="literal">
EXISTS
</code>
subquery
transformation.
</p>
<p>
For more information, see
<a class="xref" href="subquery-optimization.html" title="10.2.2 Optimizing Subqueries, Derived Tables, View References, and Common Table Expressions">
Section 10.2.2, “Optimizing Subqueries, Derived Tables, View References, and Common Table
Expressions”
</a>
.
</p>
</li>
<li class="listitem">
<p>
Subquery Transformation Flags
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
<a name="optflag_subquery-to-derived">
</a>
<a class="link" href="switchable-optimizations.html#optflag_subquery-to-derived">
<code class="literal">
subquery_to_derived
</code>
</a>
(default
<code class="literal">
off
</code>
)
</p>
<p>
The optimizer is able in many cases to transform a
scalar subquery in a
<code class="literal">
SELECT
</code>
,
<code class="literal">
WHERE
</code>
,
<code class="literal">
JOIN
</code>
, or
<code class="literal">
HAVING
</code>
clause into a left outer joins
on a derived table. (Depending on the nullability of the
derived table, this can sometimes be simplified further
to an inner join.) This can be done for a subquery which
meets the following conditions:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: square; ">
<li class="listitem">
<p>
The subquery does not make use of any
nondeterministic functions, such as
<a class="link" href="mathematical-functions.html#function_rand">
<code class="literal">
RAND()
</code>
</a>
.
</p>
</li>
<li class="listitem">
<p>
The subquery is not an
<code class="literal">
ANY
</code>
or
<code class="literal">
ALL
</code>
subquery which can be
rewritten to use
<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>
</li>
<li class="listitem">
<p>
The parent query does not set a user variable, since
rewriting it may affect the order of execution,
which could lead to unexpected results if the
variable is accessed more than once in the same
query.
</p>
</li>
<li class="listitem">
<p>
The subquery should not be correlated, that is, it
should not reference a column from a table in the
outer query, or contain an aggregate that is
evaluated in the outer query.
</p>
</li>
</ul>
</div>
<p>
This optimization can also be applied to a table
subquery which is the argument to
<code class="literal">
IN
</code>
,
<code class="literal">
NOT IN
</code>
,
<code class="literal">
EXISTS
</code>
, or
<code class="literal">
NOT EXISTS
</code>
, that does not contain a
<code class="literal">
GROUP BY
</code>
.
</p>
<p>
The default value for this flag is
<code class="literal">
off
</code>
, since, in most cases, enabling
this optimization does not produce any noticeable
improvement in performance (and in many cases can even
make queries run more slowly), but you can enable the
optimization by setting the
<a class="link" href="switchable-optimizations.html#optflag_subquery-to-derived">
<code class="literal">
subquery_to_derived
</code>
</a>
flag to
<code class="literal">
on
</code>
. It is primarily intended
for use in testing.
</p>
<p>
Example, using a scalar subquery:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa79125465"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql">d
<span class="token prompt">mysql></span> <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 punctuation">)</span><span class="token punctuation">;</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>a <span class="token datatype">INT</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt">mysql></span> <span class="token keyword">INSERT</span> <span class="token keyword">INTO</span> t1 <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> <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 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 punctuation">,</span> <span class="token keyword">ROW</span><span class="token punctuation">(</span><span class="token number">4</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt">mysql></span> <span class="token keyword">INSERT</span> <span class="token keyword">INTO</span> t2 <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> <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 punctuation">;</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token operator">*</span> <span class="token keyword">FROM</span> t1
<span class="token prompt"> -></span> <span class="token keyword">WHERE</span> t1<span class="token punctuation">.</span>a <span class="token operator">></span> <span class="token punctuation">(</span><span class="token keyword">SELECT</span> <span class="token function">COUNT</span><span class="token punctuation">(</span>a<span class="token punctuation">)</span> <span class="token keyword">FROM</span> t2<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>
<span class="token output"><span class="token punctuation">|</span> a <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> 3 <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>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token variable">@@optimizer_switch</span> <span class="token operator">LIKE</span> <span class="token string">'%subquery_to_derived=off%'</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>
<span class="token output"><span class="token punctuation">|</span> @@optimizer_switch LIKE '%subquery_to_derived=off%' <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> 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 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">EXPLAIN</span> <span class="token keyword">SELECT</span> <span class="token operator">*</span> <span class="token keyword">FROM</span> t1 <span class="token keyword">WHERE</span> t1<span class="token punctuation">.</span>a <span class="token operator">></span> <span class="token punctuation">(</span><span class="token keyword">SELECT</span> <span class="token function">COUNT</span><span class="token punctuation">(</span>a<span class="token punctuation">)</span> <span class="token keyword">FROM</span> t2<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> PRIMARY
table<span class="token punctuation">:</span> t1
partitions<span class="token punctuation">:</span> NULL
type<span class="token punctuation">:</span> ALL
possible_keys<span class="token punctuation">:</span> NULL
key<span class="token punctuation">:</span> NULL
key_len<span class="token punctuation">:</span> NULL
ref<span class="token punctuation">:</span> NULL
rows<span class="token punctuation">:</span> 4
filtered<span class="token punctuation">:</span> 33.33
Extra<span class="token punctuation">:</span> Using where
<span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span 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>
id<span class="token punctuation">:</span> 2
select_type<span class="token punctuation">:</span> SUBQUERY
table<span class="token punctuation">:</span> t2
partitions<span class="token punctuation">:</span> NULL
type<span class="token punctuation">:</span> ALL
possible_keys<span class="token punctuation">:</span> NULL
key<span class="token punctuation">:</span> NULL
key_len<span class="token punctuation">:</span> NULL
ref<span class="token punctuation">:</span> NULL
rows<span class="token punctuation">:</span> 2
filtered<span class="token punctuation">:</span> 100.00
Extra<span class="token punctuation">:</span> NULL
</span>
<span class="token prompt">mysql></span> <span class="token keyword">SET</span> <span class="token variable">@@optimizer_switch</span><span class="token operator">=</span><span class="token string">'subquery_to_derived=on'</span><span class="token punctuation">;</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token variable">@@optimizer_switch</span> <span class="token operator">LIKE</span> <span class="token string">'%subquery_to_derived=off%'</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>
<span class="token output"><span class="token punctuation">|</span> @@optimizer_switch LIKE '%subquery_to_derived=off%' <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> 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 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">@@optimizer_switch</span> <span class="token operator">LIKE</span> <span class="token string">'%subquery_to_derived=on%'</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>
<span class="token output"><span class="token punctuation">|</span> @@optimizer_switch LIKE '%subquery_to_derived=on%' <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>
<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 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">EXPLAIN</span> <span class="token keyword">SELECT</span> <span class="token operator">*</span> <span class="token keyword">FROM</span> t1 <span class="token keyword">WHERE</span> t1<span class="token punctuation">.</span>a <span class="token operator">></span> <span class="token punctuation">(</span><span class="token keyword">SELECT</span> <span class="token function">COUNT</span><span class="token punctuation">(</span>a<span class="token punctuation">)</span> <span class="token keyword">FROM</span> t2<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> PRIMARY
table<span class="token punctuation">:</span> <derived2>
partitions<span class="token punctuation">:</span> NULL
type<span class="token punctuation">:</span> ALL
possible_keys<span class="token punctuation">:</span> NULL
key<span class="token punctuation">:</span> NULL
key_len<span class="token punctuation">:</span> NULL
ref<span class="token punctuation">:</span> NULL
rows<span class="token punctuation">:</span> 1
filtered<span class="token punctuation">:</span> 100.00
Extra<span class="token punctuation">:</span> NULL
<span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span 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>
id<span class="token punctuation">:</span> 1
select_type<span class="token punctuation">:</span> PRIMARY
table<span class="token punctuation">:</span> t1
partitions<span class="token punctuation">:</span> NULL
type<span class="token punctuation">:</span> ALL
possible_keys<span class="token punctuation">:</span> NULL
key<span class="token punctuation">:</span> NULL
key_len<span class="token punctuation">:</span> NULL
ref<span class="token punctuation">:</span> NULL
rows<span class="token punctuation">:</span> 4
filtered<span class="token punctuation">:</span> 33.33
Extra<span class="token punctuation">:</span> Using where; Using join buffer (hash join)
<span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span> 3. 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> 2
select_type<span class="token punctuation">:</span> DERIVED
table<span class="token punctuation">:</span> t2
partitions<span class="token punctuation">:</span> NULL
type<span class="token punctuation">:</span> ALL
possible_keys<span class="token punctuation">:</span> NULL
key<span class="token punctuation">:</span> NULL
key_len<span class="token punctuation">:</span> NULL
ref<span class="token punctuation">:</span> NULL
rows<span class="token punctuation">:</span> 2
filtered<span class="token punctuation">:</span> 100.00
Extra<span class="token punctuation">:</span> NULL</span></code></pre>
</div>
<p>
As can be seen from executing
<a class="link" href="show-warnings.html" title="15.7.7.42 SHOW WARNINGS Statement">
<code class="literal">
SHOW
WARNINGS
</code>
</a>
immediately following the second
<a class="link" href="explain.html" title="15.8.2 EXPLAIN Statement">
<code class="literal">
EXPLAIN
</code>
</a>
statement, with
the optimization enabled, the query
<code class="literal">
SELECT *
FROM t1 WHERE t1.a > (SELECT COUNT(a) FROM
t2)
</code>
is rewritten in a form similar to what is
shown here:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa81041783"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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> t1<span class="token punctuation">.</span>a <span class="token keyword">FROM</span> t1
<span class="token keyword">JOIN</span> <span class="token punctuation">(</span> <span class="token keyword">SELECT</span> <span class="token function">COUNT</span><span class="token punctuation">(</span>t2<span class="token punctuation">.</span>a<span class="token punctuation">)</span> <span class="token keyword">AS</span> c <span class="token keyword">FROM</span> t2 <span class="token punctuation">)</span> <span class="token keyword">AS</span> d
<span class="token keyword">WHERE</span> t1<span class="token punctuation">.</span>a <span class="token operator">></span> d<span class="token punctuation">.</span>c<span class="token punctuation">;</span></code></pre>
</div>
<p>
Example, using a query with
<code class="literal">
IN
(
<em class="replaceable">
<code>
subquery
</code>
</em>
)
</code>
:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa87867367"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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">DROP</span> <span class="token keyword">TABLE</span> <span class="token keyword">IF</span> <span class="token keyword">EXISTS</span> t1<span class="token punctuation">,</span> t2<span class="token punctuation">;</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>a <span class="token datatype">INT</span><span class="token punctuation">,</span> b <span class="token datatype">INT</span><span class="token punctuation">)</span><span class="token punctuation">;</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>a <span class="token datatype">INT</span><span class="token punctuation">,</span> b <span class="token datatype">INT</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt">mysql></span> <span class="token keyword">INSERT</span> <span class="token keyword">INTO</span> t1 <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">10</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">20</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">30</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt">mysql></span> <span class="token keyword">INSERT</span> <span class="token keyword">INTO</span> t2
<span class="token prompt"> -></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">10</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">20</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">30</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">1</span><span class="token punctuation">,</span><span class="token number">110</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">120</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">130</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 operator">*</span> <span class="token keyword">FROM</span> t1
<span class="token prompt"> -></span> <span class="token keyword">WHERE</span> t1<span class="token punctuation">.</span>b <span class="token operator"><</span> <span class="token number">0</span>
<span class="token prompt"> -></span> <span class="token operator">OR</span>
<span class="token prompt"> -></span> t1<span class="token punctuation">.</span>a <span class="token keyword">IN</span> <span class="token punctuation">(</span><span class="token keyword">SELECT</span> t2<span class="token punctuation">.</span>a <span class="token operator">+</span> <span class="token number">1</span> <span class="token keyword">FROM</span> t2<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>
<span class="token output"><span class="token punctuation">|</span> a <span class="token punctuation">|</span> 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>
<span class="token output"><span class="token punctuation">|</span> 2 <span class="token punctuation">|</span> 20 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 3 <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>
<span class="token prompt">mysql></span> <span class="token keyword">SET</span> <span class="token variable">@@optimizer_switch</span><span class="token operator">=</span><span class="token string">"subquery_to_derived=off"</span><span class="token punctuation">;</span>
<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> t1
<span class="token prompt"> -></span> <span class="token keyword">WHERE</span> t1<span class="token punctuation">.</span>b <span class="token operator"><</span> <span class="token number">0</span>
<span class="token prompt"> -></span> <span class="token operator">OR</span>
<span class="token prompt"> -></span> t1<span class="token punctuation">.</span>a <span class="token keyword">IN</span> <span class="token punctuation">(</span><span class="token keyword">SELECT</span> t2<span class="token punctuation">.</span>a <span class="token operator">+</span> <span class="token number">1</span> <span class="token keyword">FROM</span> t2<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> PRIMARY
table<span class="token punctuation">:</span> t1
partitions<span class="token punctuation">:</span> NULL
type<span class="token punctuation">:</span> ALL
possible_keys<span class="token punctuation">:</span> NULL
key<span class="token punctuation">:</span> NULL
key_len<span class="token punctuation">:</span> NULL
ref<span class="token punctuation">:</span> NULL
rows<span class="token punctuation">:</span> 3
filtered<span class="token punctuation">:</span> 100.00
Extra<span class="token punctuation">:</span> Using where
<span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span 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>
id<span class="token punctuation">:</span> 2
select_type<span class="token punctuation">:</span> DEPENDENT SUBQUERY
table<span class="token punctuation">:</span> t2
partitions<span class="token punctuation">:</span> NULL
type<span class="token punctuation">:</span> ALL
possible_keys<span class="token punctuation">:</span> NULL
key<span class="token punctuation">:</span> NULL
key_len<span class="token punctuation">:</span> NULL
ref<span class="token punctuation">:</span> NULL
rows<span class="token punctuation">:</span> 6
filtered<span class="token punctuation">:</span> 100.00
Extra<span class="token punctuation">:</span> Using where
</span>
<span class="token prompt">mysql></span> <span class="token keyword">SET</span> <span class="token variable">@@optimizer_switch</span><span class="token operator">=</span><span class="token string">"subquery_to_derived=on"</span><span class="token punctuation">;</span>
<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> t1
<span class="token prompt"> -></span> <span class="token keyword">WHERE</span> t1<span class="token punctuation">.</span>b <span class="token operator"><</span> <span class="token number">0</span>
<span class="token prompt"> -></span> <span class="token operator">OR</span>
<span class="token prompt"> -></span> t1<span class="token punctuation">.</span>a <span class="token keyword">IN</span> <span class="token punctuation">(</span><span class="token keyword">SELECT</span> t2<span class="token punctuation">.</span>a <span class="token operator">+</span> <span class="token number">1</span> <span class="token keyword">FROM</span> t2<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> PRIMARY
table<span class="token punctuation">:</span> t1
partitions<span class="token punctuation">:</span> NULL
type<span class="token punctuation">:</span> ALL
possible_keys<span class="token punctuation">:</span> NULL
key<span class="token punctuation">:</span> NULL
key_len<span class="token punctuation">:</span> NULL
ref<span class="token punctuation">:</span> NULL
rows<span class="token punctuation">:</span> 3
filtered<span class="token punctuation">:</span> 100.00
Extra<span class="token punctuation">:</span> NULL
<span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span 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>
id<span class="token punctuation">:</span> 1
select_type<span class="token punctuation">:</span> PRIMARY
table<span class="token punctuation">:</span> <derived2>
partitions<span class="token punctuation">:</span> NULL
type<span class="token punctuation">:</span> ref
possible_keys<span class="token punctuation">:</span> <auto_key0>
key<span class="token punctuation">:</span> <auto_key0>
key_len<span class="token punctuation">:</span> 9
ref<span class="token punctuation">:</span> std2.t1.a
rows<span class="token punctuation">:</span> 2
filtered<span class="token punctuation">:</span> 100.00
Extra<span class="token punctuation">:</span> Using where; Using index
<span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span> 3. 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> 2
select_type<span class="token punctuation">:</span> DERIVED
table<span class="token punctuation">:</span> t2
partitions<span class="token punctuation">:</span> NULL
type<span class="token punctuation">:</span> ALL
possible_keys<span class="token punctuation">:</span> NULL
key<span class="token punctuation">:</span> NULL
key_len<span class="token punctuation">:</span> NULL
ref<span class="token punctuation">:</span> NULL
rows<span class="token punctuation">:</span> 6
filtered<span class="token punctuation">:</span> 100.00
Extra<span class="token punctuation">:</span> Using temporary</span></code></pre>
</div>
<p>
Checking and simplifying the result of
<a class="link" href="show-warnings.html" title="15.7.7.42 SHOW WARNINGS Statement">
<code class="literal">
SHOW WARNINGS
</code>
</a>
after
executing
<a class="link" href="explain.html" title="15.8.2 EXPLAIN Statement">
<code class="literal">
EXPLAIN
</code>
</a>
on this
query shows that, when the
<a class="link" href="switchable-optimizations.html#optflag_subquery-to-derived">
<code class="literal">
subquery_to_derived
</code>
</a>
flag enabled,
<code class="literal">
SELECT * FROM t1 WHERE t1.b <
0 OR t1.a IN (SELECT t2.a + 1 FROM t2)
</code>
is
rewritten in a form similar to what is shown here:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa16843391"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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> a<span class="token punctuation">,</span> b <span class="token keyword">FROM</span> t1
<span class="token keyword">LEFT</span> <span class="token keyword">JOIN</span> <span class="token punctuation">(</span><span class="token keyword">SELECT</span> <span class="token keyword">DISTINCT</span> a <span class="token operator">+</span> <span class="token number">1</span> <span class="token keyword">AS</span> e <span class="token keyword">FROM</span> t2<span class="token punctuation">)</span> d
<span class="token keyword">ON</span> t1<span class="token punctuation">.</span>a <span class="token operator">=</span> d<span class="token punctuation">.</span>e
<span class="token keyword">WHERE</span> t1<span class="token punctuation">.</span>b <span class="token operator"><</span> <span class="token number">0</span>
<span class="token operator">OR</span>
d<span class="token punctuation">.</span>e <span class="token operator">IS</span> <span class="token operator">NOT</span> <span class="token boolean">NULL</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
Example, using a query with
<code class="literal">
EXISTS
(
<em class="replaceable">
<code>
subquery
</code>
</em>
)
</code>
and the
same tables and data as in the previous example:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa34975977"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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> t1
<span class="token prompt"> -></span> <span class="token keyword">WHERE</span> t1<span class="token punctuation">.</span>b <span class="token operator"><</span> <span class="token number">0</span>
<span class="token prompt"> -></span> <span class="token operator">OR</span>
<span class="token prompt"> -></span> <span class="token keyword">EXISTS</span><span class="token punctuation">(</span><span class="token keyword">SELECT</span> <span class="token operator">*</span> <span class="token keyword">FROM</span> t2 <span class="token keyword">WHERE</span> t2<span class="token punctuation">.</span>a <span class="token operator">=</span> t1<span class="token punctuation">.</span>a <span class="token operator">+</span> <span class="token number">1</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>
<span class="token output"><span class="token punctuation">|</span> a <span class="token punctuation">|</span> 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>
<span class="token output"><span class="token punctuation">|</span> 1 <span class="token punctuation">|</span> 10 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 2 <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>
<span class="token prompt">mysql></span> <span class="token keyword">SET</span> <span class="token variable">@@optimizer_switch</span><span class="token operator">=</span><span class="token string">"subquery_to_derived=off"</span><span class="token punctuation">;</span>
<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> t1
<span class="token prompt"> -></span> <span class="token keyword">WHERE</span> t1<span class="token punctuation">.</span>b <span class="token operator"><</span> <span class="token number">0</span>
<span class="token prompt"> -></span> <span class="token operator">OR</span>
<span class="token prompt"> -></span> <span class="token keyword">EXISTS</span><span class="token punctuation">(</span><span class="token keyword">SELECT</span> <span class="token operator">*</span> <span class="token keyword">FROM</span> t2 <span class="token keyword">WHERE</span> t2<span class="token punctuation">.</span>a <span class="token operator">=</span> t1<span class="token punctuation">.</span>a <span class="token operator">+</span> <span class="token number">1</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> PRIMARY
table<span class="token punctuation">:</span> t1
partitions<span class="token punctuation">:</span> NULL
type<span class="token punctuation">:</span> ALL
possible_keys<span class="token punctuation">:</span> NULL
key<span class="token punctuation">:</span> NULL
key_len<span class="token punctuation">:</span> NULL
ref<span class="token punctuation">:</span> NULL
rows<span class="token punctuation">:</span> 3
filtered<span class="token punctuation">:</span> 100.00
Extra<span class="token punctuation">:</span> Using where
<span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span 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>
id<span class="token punctuation">:</span> 2
select_type<span class="token punctuation">:</span> DEPENDENT SUBQUERY
table<span class="token punctuation">:</span> t2
partitions<span class="token punctuation">:</span> NULL
type<span class="token punctuation">:</span> ALL
possible_keys<span class="token punctuation">:</span> NULL
key<span class="token punctuation">:</span> NULL
key_len<span class="token punctuation">:</span> NULL
ref<span class="token punctuation">:</span> NULL
rows<span class="token punctuation">:</span> 6
filtered<span class="token punctuation">:</span> 16.67
Extra<span class="token punctuation">:</span> Using where
</span>
<span class="token prompt">mysql></span> <span class="token keyword">SET</span> <span class="token variable">@@optimizer_switch</span><span class="token operator">=</span><span class="token string">"subquery_to_derived=on"</span><span class="token punctuation">;</span>
<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> t1
<span class="token prompt"> -></span> <span class="token keyword">WHERE</span> t1<span class="token punctuation">.</span>b <span class="token operator"><</span> <span class="token number">0</span>
<span class="token prompt"> -></span> <span class="token operator">OR</span>
<span class="token prompt"> -></span> <span class="token keyword">EXISTS</span><span class="token punctuation">(</span><span class="token keyword">SELECT</span> <span class="token operator">*</span> <span class="token keyword">FROM</span> t2 <span class="token keyword">WHERE</span> t2<span class="token punctuation">.</span>a <span class="token operator">=</span> t1<span class="token punctuation">.</span>a <span class="token operator">+</span> <span class="token number">1</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> PRIMARY
table<span class="token punctuation">:</span> t1
partitions<span class="token punctuation">:</span> NULL
type<span class="token punctuation">:</span> ALL
possible_keys<span class="token punctuation">:</span> NULL
key<span class="token punctuation">:</span> NULL
key_len<span class="token punctuation">:</span> NULL
ref<span class="token punctuation">:</span> NULL
rows<span class="token punctuation">:</span> 3
filtered<span class="token punctuation">:</span> 100.00
Extra<span class="token punctuation">:</span> NULL
<span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span 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>
id<span class="token punctuation">:</span> 1
select_type<span class="token punctuation">:</span> PRIMARY
table<span class="token punctuation">:</span> <derived2>
partitions<span class="token punctuation">:</span> NULL
type<span class="token punctuation">:</span> ALL
possible_keys<span class="token punctuation">:</span> NULL
key<span class="token punctuation">:</span> NULL
key_len<span class="token punctuation">:</span> NULL
ref<span class="token punctuation">:</span> NULL
rows<span class="token punctuation">:</span> 6
filtered<span class="token punctuation">:</span> 100.00
Extra<span class="token punctuation">:</span> Using where; Using join buffer (hash join)
<span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span> 3. 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> 2
select_type<span class="token punctuation">:</span> DERIVED
table<span class="token punctuation">:</span> t2
partitions<span class="token punctuation">:</span> NULL
type<span class="token punctuation">:</span> ALL
possible_keys<span class="token punctuation">:</span> NULL
key<span class="token punctuation">:</span> NULL
key_len<span class="token punctuation">:</span> NULL
ref<span class="token punctuation">:</span> NULL
rows<span class="token punctuation">:</span> 6
filtered<span class="token punctuation">:</span> 100.00
Extra<span class="token punctuation">:</span> Using temporary</span></code></pre>
</div>
<p>
If we execute
<a class="link" href="show-warnings.html" title="15.7.7.42 SHOW WARNINGS Statement">
<code class="literal">
SHOW
WARNINGS
</code>
</a>
after running
<a class="link" href="explain.html" title="15.8.2 EXPLAIN Statement">
<code class="literal">
EXPLAIN
</code>
</a>
on the query
<code class="literal">
SELECT * FROM t1 WHERE t1.b < 0 OR
EXISTS(SELECT * FROM t2 WHERE t2.a = t1.a + 1)
</code>
when
<a class="link" href="switchable-optimizations.html#optflag_subquery-to-derived">
<code class="literal">
subquery_to_derived
</code>
</a>
has been enabled, and simplify the second row of the
result, we see that it has been rewritten in a form
which resembles this:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa3250283"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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> a<span class="token punctuation">,</span> b <span class="token keyword">FROM</span> t1
<span class="token keyword">LEFT</span> <span class="token keyword">JOIN</span> <span class="token punctuation">(</span><span class="token keyword">SELECT</span> <span class="token keyword">DISTINCT</span> <span class="token number">1</span> <span class="token keyword">AS</span> e1<span class="token punctuation">,</span> t2<span class="token punctuation">.</span>a <span class="token keyword">AS</span> e2 <span class="token keyword">FROM</span> t2<span class="token punctuation">)</span> d
<span class="token keyword">ON</span> t1<span class="token punctuation">.</span>a <span class="token operator">+</span> <span class="token number">1</span> <span class="token operator">=</span> d<span class="token punctuation">.</span>e2
<span class="token keyword">WHERE</span> t1<span class="token punctuation">.</span>b <span class="token operator"><</span> <span class="token number">0</span>
<span class="token operator">OR</span>
d<span class="token punctuation">.</span>e1 <span class="token operator">IS</span> <span class="token operator">NOT</span> <span class="token boolean">NULL</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
For more information, see
<a class="xref" href="derived-table-optimization.html" title="10.2.2.4 Optimizing Derived Tables, View References, and Common Table Expressions with Merging or Materialization">
Section 10.2.2.4, “Optimizing Derived Tables, View References, and Common Table Expressions
with Merging or Materialization”
</a>
, as well as
<a class="xref" href="limit-optimization.html" title="10.2.1.19 LIMIT Query Optimization">
Section 10.2.1.19, “LIMIT Query Optimization”
</a>
, and
<a class="ulink" href="/doc/refman/8.0/en/semijoins.html" target="_top">
Optimizing IN and EXISTS Subquery Predicates with Semijoin Transformations
</a>
.
</p>
</li>
</ul>
</div>
</li>
</ul>
</div>
<p>
When you assign a value to
<a class="link" href="server-system-variables.html#sysvar_optimizer_switch">
<code class="literal">
optimizer_switch
</code>
</a>
, flags that
are not mentioned keep their current values. This makes it
possible to enable or disable specific optimizer behaviors in a
single statement without affecting other behaviors. The
statement does not depend on what other optimizer flags exist
and what their values are. Suppose that all Index Merge
optimizations are enabled:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa47944846"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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">@@optimizer_switch</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>
@@optimizer_switch<span class="token punctuation">:</span> index_merge=on,index_merge_union=on,
index_merge_sort_union=on,index_merge_intersection=on,
engine_condition_pushdown=on,index_condition_pushdown=on,
mrr=on,mrr_cost_based=on,block_nested_loop=on,
batched_key_access=off,materialization=on,semijoin=on,
loosescan=on, firstmatch=on,
subquery_materialization_cost_based=on,
use_index_extensions=on,condition_fanout_filter=on,
derived_merge=on,use_invisible_indexes=off,skip_scan=on,
hash_join=on,subquery_to_derived=off,
prefer_ordering_index=on</span></code></pre>
</div>
<p>
If the server is using the Index Merge Union or Index Merge
Sort-Union access methods for certain queries and you want to
check whether the optimizer can perform better without them, set
the variable value like this:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa3626019"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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> optimizer_switch<span class="token operator">=</span><span class="token string">'index_merge_union=off,index_merge_sort_union=off'</span><span class="token punctuation">;</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token variable">@@optimizer_switch</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>
@@optimizer_switch<span class="token punctuation">:</span> index_merge=on,index_merge_union=off,
index_merge_sort_union=off,index_merge_intersection=on,
engine_condition_pushdown=on,index_condition_pushdown=on,
mrr=on,mrr_cost_based=on,block_nested_loop=on,
batched_key_access=off,materialization=on,semijoin=on,
loosescan=on, firstmatch=on,
subquery_materialization_cost_based=on,
use_index_extensions=on,condition_fanout_filter=on,
derived_merge=on,use_invisible_indexes=off,skip_scan=on,
hash_join=on,subquery_to_derived=off,
prefer_ordering_index=on</span></code></pre>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/storage-requirements.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h2 class="title">
<a name="storage-requirements">
</a>
13.7 Data Type Storage Requirements
</h2>
</div>
</div>
</div>
<a class="indexterm" name="idm46045210772800">
</a>
<a class="indexterm" name="idm46045210771344">
</a>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<a class="xref" href="storage-requirements.html#data-types-storage-reqs-innodb" title="InnoDB Table Storage Requirements">
InnoDB Table Storage Requirements
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="storage-requirements.html#data-types-storage-reqs-ndb" title="NDB Table Storage Requirements">
NDB Table Storage Requirements
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="storage-requirements.html#data-types-storage-reqs-numeric" title="Numeric Type Storage Requirements">
Numeric Type Storage Requirements
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="storage-requirements.html#data-types-storage-reqs-date-time" title="Date and Time Type Storage Requirements">
Date and Time Type Storage Requirements
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="storage-requirements.html#data-types-storage-reqs-strings" title="String Type Storage Requirements">
String Type Storage Requirements
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="storage-requirements.html#data-types-storage-reqs-gis" title="Spatial Type Storage Requirements">
Spatial Type Storage Requirements
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="storage-requirements.html#data-types-storage-reqs-json" title="JSON Storage Requirements">
JSON Storage Requirements
</a>
</p>
</li>
</ul>
</div>
<p>
The storage requirements for table data on disk depend on several
factors. Different storage engines represent data types and store
raw data differently. Table data might be compressed, either for a
column or an entire row, complicating the calculation of storage
requirements for a table or column.
</p>
<p>
Despite differences in storage layout on disk, the internal MySQL
APIs that communicate and exchange information about table rows
use a consistent data structure that applies across all storage
engines.
</p>
<p>
This section includes guidelines and information for the storage
requirements for each data type supported by MySQL, including the
internal format and size for storage engines that use a fixed-size
representation for data types. Information is listed by category
or storage engine.
</p>
<a class="indexterm" name="idm46045210759904">
</a>
<p>
The internal representation of a table has a maximum row size of
65,535 bytes, even if the storage engine is capable of supporting
larger rows. This figure excludes
<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, which contribute only
9 to 12 bytes toward this size. For
<a class="link" href="blob.html" title="13.3.4 The BLOB and TEXT Types">
<code class="literal">
BLOB
</code>
</a>
and
<a class="link" href="blob.html" title="13.3.4 The BLOB and TEXT Types">
<code class="literal">
TEXT
</code>
</a>
data, the information is
stored internally in a different area of memory than the row
buffer. Different storage engines handle the allocation and
storage of this data in different ways, according to the method
they use for handling the corresponding types. For more
information, see
<a class="xref" href="storage-engines.html" title="Chapter 18 Alternative Storage Engines">
Chapter 18,
<i>
Alternative Storage Engines
</i>
</a>
, and
<a class="xref" href="column-count-limit.html" title="10.4.7 Limits on Table Column Count and Row Size">
Section 10.4.7, “Limits on Table Column Count and Row Size”
</a>
.
</p>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h3 class="title">
<a name="data-types-storage-reqs-innodb">
</a>
InnoDB Table Storage Requirements
</h3>
</div>
</div>
</div>
<a class="indexterm" name="idm46045210750080">
</a>
<a class="indexterm" name="idm46045210748592">
</a>
<p>
See
<a class="xref" href="innodb-row-format.html" title="17.10 InnoDB Row Formats">
Section 17.10, “InnoDB Row Formats”
</a>
for information about
storage requirements for
<code class="literal">
InnoDB
</code>
tables.
</p>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h3 class="title">
<a name="data-types-storage-reqs-ndb">
</a>
NDB Table Storage Requirements
</h3>
</div>
</div>
</div>
<a class="indexterm" name="idm46045210743968">
</a>
<a class="indexterm" name="idm46045210742480">
</a>
<div class="important" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Important
</div>
<p>
<a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4">
<code class="literal">
NDB
</code>
</a>
tables use
<span class="firstterm">
4-byte alignment
</span>
; all
<a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4">
<code class="literal">
NDB
</code>
</a>
data storage is done in
multiples of 4 bytes. Thus, a column value that would
typically take 15 bytes requires 16 bytes in an
<a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4">
<code class="literal">
NDB
</code>
</a>
table. For example, in
<a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4">
<code class="literal">
NDB
</code>
</a>
tables, the
<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>
,
<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>
,
<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>
, and
<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>
(
<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>
) column types each require
4 bytes storage per record due to the alignment factor.
</p>
<p>
Each
<code class="literal">
BIT(
<em class="replaceable">
<code>
M
</code>
</em>
)
</code>
column takes
<em class="replaceable">
<code>
M
</code>
</em>
bits of storage
space. Although an individual
<a class="link" href="bit-type.html" title="13.1.5 Bit-Value Type - BIT">
<code class="literal">
BIT
</code>
</a>
column is
<span class="emphasis">
<em>
not
</em>
</span>
4-byte aligned,
<a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4">
<code class="literal">
NDB
</code>
</a>
reserves 4 bytes (32 bits)
per row for the first 1-32 bits needed for
<code class="literal">
BIT
</code>
columns, then another 4 bytes for bits
33-64, and so on.
</p>
<p>
While a
<code class="literal">
NULL
</code>
itself does not require any
storage space,
<a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4">
<code class="literal">
NDB
</code>
</a>
reserves 4
bytes per row if the table definition contains any columns
allowing
<code class="literal">
NULL
</code>
, up to 32
<code class="literal">
NULL
</code>
columns. (If an NDB Cluster table is
defined with more than 32
<code class="literal">
NULL
</code>
columns up
to 64
<code class="literal">
NULL
</code>
columns, then 8 bytes per row
are reserved.)
</p>
</div>
<p>
Every table using the
<a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4">
<code class="literal">
NDB
</code>
</a>
storage
engine requires a primary key; if you do not define a primary
key, a
<span class="quote">
“
<span class="quote">
hidden
</span>
”
</span>
primary key is created by
<a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4">
<code class="literal">
NDB
</code>
</a>
. This hidden primary key
consumes 31-35 bytes per table record.
</p>
<a class="indexterm" name="idm46045210713776">
</a>
<p>
You can use the
<a class="link" href="mysql-cluster-programs-ndb-size-pl.html" title="25.5.29 ndb_size.pl — NDBCLUSTER Size Requirement Estimator">
<span class="command">
<strong>
ndb_size.pl
</strong>
</span>
</a>
Perl script to
estimate
<a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4">
<code class="literal">
NDB
</code>
</a>
storage requirements.
It connects to a current MySQL (not NDB Cluster) database and
creates a report on how much space that database would require
if it used the
<a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4">
<code class="literal">
NDB
</code>
</a>
storage engine.
See
<a class="xref" href="mysql-cluster-programs-ndb-size-pl.html" title="25.5.29 ndb_size.pl — NDBCLUSTER Size Requirement Estimator">
Section 25.5.29, “ndb_size.pl — NDBCLUSTER Size Requirement Estimator”
</a>
for
more information.
</p>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h3 class="title">
<a name="data-types-storage-reqs-numeric">
</a>
Numeric Type Storage Requirements
</h3>
</div>
</div>
</div>
<a class="indexterm" name="idm46045210706288">
</a>
<a class="indexterm" name="idm46045210704800">
</a>
<div class="informaltable">
<table summary="Storage required for numeric data types.">
<colgroup>
<col style="width: 40%"/>
<col style="width: 60%"/>
</colgroup>
<thead>
<tr>
<th>
Data Type
</th>
<th>
Storage Required
</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">
TINYINT
</code>
</a>
</td>
<td>
1 byte
</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">
SMALLINT
</code>
</a>
</td>
<td>
2 bytes
</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">
MEDIUMINT
</code>
</a>
</td>
<td>
3 bytes
</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">
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>
</td>
<td>
4 bytes
</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">
BIGINT
</code>
</a>
</td>
<td>
8 bytes
</td>
</tr>
<tr>
<td>
<code class="literal">
FLOAT(
<em class="replaceable">
<code>
p
</code>
</em>
)
</code>
</td>
<td>
4 bytes if 0 <=
<em class="replaceable">
<code>
p
</code>
</em>
<= 24, 8 bytes if 25
<=
<em class="replaceable">
<code>
p
</code>
</em>
<= 53
</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">
FLOAT
</code>
</a>
</td>
<td>
4 bytes
</td>
</tr>
<tr>
<td>
<code class="literal">
DOUBLE [PRECISION]
</code>
,
<a class="link" href="floating-point-types.html" title="13.1.4 Floating-Point Types (Approximate Value) - FLOAT, DOUBLE">
<code class="literal">
REAL
</code>
</a>
</td>
<td>
8 bytes
</td>
</tr>
<tr>
<td>
<code class="literal">
DECIMAL(
<em class="replaceable">
<code>
M
</code>
</em>
,
<em class="replaceable">
<code>
D
</code>
</em>
)
</code>
,
<code class="literal">
NUMERIC(
<em class="replaceable">
<code>
M
</code>
</em>
,
<em class="replaceable">
<code>
D
</code>
</em>
)
</code>
</td>
<td>
Varies; see following discussion
</td>
</tr>
<tr>
<td>
<code class="literal">
BIT(
<em class="replaceable">
<code>
M
</code>
</em>
)
</code>
</td>
<td>
approximately (
<em class="replaceable">
<code>
M
</code>
</em>
+7)/8 bytes
</td>
</tr>
</tbody>
</table>
</div>
<div class="informaltable">
<table cellpadding="0" cellspacing="0" style="position: fixed; top: 0px; display: none; left: 401px; width: 539px;">
<thead>
<tr>
<th style="width: 215.312px;">
Data Type
</th>
<th style="width: 322.969px;">
Storage Required
</th>
</tr>
</thead>
</table>
</div>
<p>
Values for
<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>
(and
<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>
) columns are represented
using a binary format that packs nine decimal (base 10) digits
into four bytes. Storage for the integer and fractional parts of
each value are determined separately. Each multiple of nine
digits requires four bytes, and the
<span class="quote">
“
<span class="quote">
leftover
</span>
”
</span>
digits require some fraction of four bytes. The storage required
for excess digits is given by the following table.
</p>
<div class="informaltable">
<table summary="Storage required by excess/leftover digits in DECIMAL values.">
<colgroup>
<col style="width: 25%"/>
<col style="width: 25%"/>
</colgroup>
<thead>
<tr>
<th>
Leftover Digits
</th>
<th>
Number of Bytes
</th>
</tr>
</thead>
<tbody>
<tr>
<td>
0
</td>
<td>
0
</td>
</tr>
<tr>
<td>
1
</td>
<td>
1
</td>
</tr>
<tr>
<td>
2
</td>
<td>
1
</td>
</tr>
<tr>
<td>
3
</td>
<td>
2
</td>
</tr>
<tr>
<td>
4
</td>
<td>
2
</td>
</tr>
<tr>
<td>
5
</td>
<td>
3
</td>
</tr>
<tr>
<td>
6
</td>
<td>
3
</td>
</tr>
<tr>
<td>
7
</td>
<td>
4
</td>
</tr>
<tr>
<td>
8
</td>
<td>
4
</td>
</tr>
</tbody>
</table>
</div>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h3 class="title">
<a name="data-types-storage-reqs-date-time">
</a>
Date and Time Type Storage Requirements
</h3>
</div>
</div>
</div>
<a class="indexterm" name="idm46045210633312">
</a>
<a class="indexterm" name="idm46045210631824">
</a>
<a class="indexterm" name="idm46045210630336">
</a>
<a class="indexterm" name="idm46045210628848">
</a>
<p>
For
<a class="link" href="time.html" title="13.2.3 The TIME Type">
<code class="literal">
TIME
</code>
</a>
,
<a class="link" href="datetime.html" title="13.2.2 The DATE, DATETIME, and TIMESTAMP Types">
<code class="literal">
DATETIME
</code>
</a>
, and
<a class="link" href="datetime.html" title="13.2.2 The DATE, DATETIME, and TIMESTAMP Types">
<code class="literal">
TIMESTAMP
</code>
</a>
columns, the storage
required for tables created before MySQL 5.6.4 differs from
tables created from 5.6.4 on. This is due to a change in 5.6.4
that permits these types to have a fractional part, which
requires from 0 to 3 bytes.
</p>
<div class="informaltable">
<table summary="Storage required for date and time data types before MySQL 5.6.4 and as of MySQL 5.6.4.">
<colgroup>
<col style="width: 20%"/>
<col style="width: 40%"/>
<col style="width: 40%"/>
</colgroup>
<thead>
<tr>
<th scope="col">
Data Type
</th>
<th scope="col">
Storage Required Before MySQL 5.6.4
</th>
<th scope="col">
Storage Required as of MySQL 5.6.4
</th>
</tr>
</thead>
<tbody>
<tr>
<th scope="row">
<a class="link" href="year.html" title="13.2.4 The YEAR Type">
<code class="literal">
YEAR
</code>
</a>
</th>
<td>
1 byte
</td>
<td>
1 byte
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="datetime.html" title="13.2.2 The DATE, DATETIME, and TIMESTAMP Types">
<code class="literal">
DATE
</code>
</a>
</th>
<td>
3 bytes
</td>
<td>
3 bytes
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="time.html" title="13.2.3 The TIME Type">
<code class="literal">
TIME
</code>
</a>
</th>
<td>
3 bytes
</td>
<td>
3 bytes + fractional seconds storage
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="datetime.html" title="13.2.2 The DATE, DATETIME, and TIMESTAMP Types">
<code class="literal">
DATETIME
</code>
</a>
</th>
<td>
8 bytes
</td>
<td>
5 bytes + fractional seconds storage
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="datetime.html" title="13.2.2 The DATE, DATETIME, and TIMESTAMP Types">
<code class="literal">
TIMESTAMP
</code>
</a>
</th>
<td>
4 bytes
</td>
<td>
4 bytes + fractional seconds storage
</td>
</tr>
</tbody>
</table>
</div>
<p>
As of MySQL 5.6.4, storage for
<a class="link" href="year.html" title="13.2.4 The YEAR Type">
<code class="literal">
YEAR
</code>
</a>
and
<a class="link" href="datetime.html" title="13.2.2 The DATE, DATETIME, and TIMESTAMP Types">
<code class="literal">
DATE
</code>
</a>
remains unchanged. However,
<a class="link" href="time.html" title="13.2.3 The TIME Type">
<code class="literal">
TIME
</code>
</a>
,
<a class="link" href="datetime.html" title="13.2.2 The DATE, DATETIME, and TIMESTAMP Types">
<code class="literal">
DATETIME
</code>
</a>
, and
<a class="link" href="datetime.html" title="13.2.2 The DATE, DATETIME, and TIMESTAMP Types">
<code class="literal">
TIMESTAMP
</code>
</a>
are represented
differently.
<a class="link" href="datetime.html" title="13.2.2 The DATE, DATETIME, and TIMESTAMP Types">
<code class="literal">
DATETIME
</code>
</a>
is packed
more efficiently, requiring 5 rather than 8 bytes for the
nonfractional part, and all three parts have a fractional part
that requires from 0 to 3 bytes, depending on the fractional
seconds precision of stored values.
</p>
<div class="informaltable">
<table summary="Required storage for fractional seconds precision.">
<colgroup>
<col style="width: 50%"/>
<col style="width: 50%"/>
</colgroup>
<thead>
<tr>
<th>
Fractional Seconds Precision
</th>
<th>
Storage Required
</th>
</tr>
</thead>
<tbody>
<tr>
<td>
0
</td>
<td>
0 bytes
</td>
</tr>
<tr>
<td>
1, 2
</td>
<td>
1 byte
</td>
</tr>
<tr>
<td>
3, 4
</td>
<td>
2 bytes
</td>
</tr>
<tr>
<td>
5, 6
</td>
<td>
3 bytes
</td>
</tr>
</tbody>
</table>
</div>
<p>
For example,
<a class="link" href="time.html" title="13.2.3 The TIME Type">
<code class="literal">
TIME(0)
</code>
</a>
,
<a class="link" href="time.html" title="13.2.3 The TIME Type">
<code class="literal">
TIME(2)
</code>
</a>
,
<a class="link" href="time.html" title="13.2.3 The TIME Type">
<code class="literal">
TIME(4)
</code>
</a>
, and
<a class="link" href="time.html" title="13.2.3 The TIME Type">
<code class="literal">
TIME(6)
</code>
</a>
use 3, 4, 5, and 6 bytes,
respectively.
<a class="link" href="time.html" title="13.2.3 The TIME Type">
<code class="literal">
TIME
</code>
</a>
and
<a class="link" href="time.html" title="13.2.3 The TIME Type">
<code class="literal">
TIME(0)
</code>
</a>
are equivalent and
require the same storage.
</p>
<p>
For details about internal representation of temporal values,
see
<a class="ulink" href="/doc/internals/en/algorithms.html" target="_top">
MySQL
Internals: Important Algorithms and Structures
</a>
.
</p>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h3 class="title">
<a name="data-types-storage-reqs-strings">
</a>
String Type Storage Requirements
</h3>
</div>
</div>
</div>
<a class="indexterm" name="idm46045210561776">
</a>
<a class="indexterm" name="idm46045210560288">
</a>
<p>
In the following table,
<em class="replaceable">
<code>
M
</code>
</em>
represents
the declared column length in characters for nonbinary string
types and bytes for binary string types.
<em class="replaceable">
<code>
L
</code>
</em>
represents the actual length in
bytes of a given string value.
</p>
<div class="informaltable">
<table summary="Storage required for string types.">
<colgroup>
<col style="width: 40%"/>
<col style="width: 60%"/>
</colgroup>
<thead>
<tr>
<th>
Data Type
</th>
<th>
Storage Required
</th>
</tr>
</thead>
<tbody>
<tr>
<td>
<code class="literal">
CHAR(
<em class="replaceable">
<code>
M
</code>
</em>
)
</code>
</td>
<td>
The compact family of InnoDB row formats optimize storage for
variable-length character sets. See
<a class="xref" href="innodb-row-format.html#innodb-compact-row-format-characteristics" title="COMPACT Row Format Storage Characteristics">
COMPACT Row Format Storage Characteristics
</a>
.
Otherwise,
<em class="replaceable">
<code>
M
</code>
</em>
×
<em class="replaceable">
<code>
w
</code>
</em>
bytes,
<code class="literal">
<=
<em class="replaceable">
<code>
M
</code>
</em>
<=
</code>
255, where
<em class="replaceable">
<code>
w
</code>
</em>
is the number of bytes
required for the maximum-length character in the character
set.
</td>
</tr>
<tr>
<td>
<code class="literal">
BINARY(
<em class="replaceable">
<code>
M
</code>
</em>
)
</code>
</td>
<td>
<em class="replaceable">
<code>
M
</code>
</em>
bytes, 0
<code class="literal">
<=
<em class="replaceable">
<code>
M
</code>
</em>
<=
</code>
255
</td>
</tr>
<tr>
<td>
<code class="literal">
VARCHAR(
<em class="replaceable">
<code>
M
</code>
</em>
)
</code>
,
<code class="literal">
VARBINARY(
<em class="replaceable">
<code>
M
</code>
</em>
)
</code>
</td>
<td>
<em class="replaceable">
<code>
L
</code>
</em>
+ 1 bytes if column values require 0
− 255 bytes,
<em class="replaceable">
<code>
L
</code>
</em>
+ 2 bytes
if values may require more than 255 bytes
</td>
</tr>
<tr>
<td>
<a class="link" href="blob.html" title="13.3.4 The BLOB and TEXT Types">
<code class="literal">
TINYBLOB
</code>
</a>
,
<a class="link" href="blob.html" title="13.3.4 The BLOB and TEXT Types">
<code class="literal">
TINYTEXT
</code>
</a>
</td>
<td>
<em class="replaceable">
<code>
L
</code>
</em>
+ 1 bytes, where
<em class="replaceable">
<code>
L
</code>
</em>
<
2
<sup>
8
</sup>
</td>
</tr>
<tr>
<td>
<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>
</td>
<td>
<em class="replaceable">
<code>
L
</code>
</em>
+ 2 bytes, where
<em class="replaceable">
<code>
L
</code>
</em>
<
2
<sup>
16
</sup>
</td>
</tr>
<tr>
<td>
<a class="link" href="blob.html" title="13.3.4 The BLOB and TEXT Types">
<code class="literal">
MEDIUMBLOB
</code>
</a>
,
<a class="link" href="blob.html" title="13.3.4 The BLOB and TEXT Types">
<code class="literal">
MEDIUMTEXT
</code>
</a>
</td>
<td>
<em class="replaceable">
<code>
L
</code>
</em>
+ 3 bytes, where
<em class="replaceable">
<code>
L
</code>
</em>
<
2
<sup>
24
</sup>
</td>
</tr>
<tr>
<td>
<a class="link" href="blob.html" title="13.3.4 The BLOB and TEXT Types">
<code class="literal">
LONGBLOB
</code>
</a>
,
<a class="link" href="blob.html" title="13.3.4 The BLOB and TEXT Types">
<code class="literal">
LONGTEXT
</code>
</a>
</td>
<td>
<em class="replaceable">
<code>
L
</code>
</em>
+ 4 bytes, where
<em class="replaceable">
<code>
L
</code>
</em>
<
2
<sup>
32
</sup>
</td>
</tr>
<tr>
<td>
<code class="literal">
ENUM('
<em class="replaceable">
<code>
value1
</code>
</em>
','
<em class="replaceable">
<code>
value2
</code>
</em>
',...)
</code>
</td>
<td>
1 or 2 bytes, depending on the number of enumeration values (65,535
values maximum)
</td>
</tr>
<tr>
<td>
<code class="literal">
SET('
<em class="replaceable">
<code>
value1
</code>
</em>
','
<em class="replaceable">
<code>
value2
</code>
</em>
',...)
</code>
</td>
<td>
1, 2, 3, 4, or 8 bytes, depending on the number of set members (64
members maximum)
</td>
</tr>
</tbody>
</table>
</div>
<p>
Variable-length string types are stored using a length prefix
plus data. The length prefix requires from one to four bytes
depending on the data type, and the value of the prefix is
<em class="replaceable">
<code>
L
</code>
</em>
(the byte length of the string).
For example, storage for a
<a class="link" href="blob.html" title="13.3.4 The BLOB and TEXT Types">
<code class="literal">
MEDIUMTEXT
</code>
</a>
value requires
<em class="replaceable">
<code>
L
</code>
</em>
bytes to store the value plus three
bytes to store the length of the value.
</p>
<p>
To calculate the number of bytes used to store a particular
<a class="link" href="char.html" title="13.3.2 The CHAR and VARCHAR Types">
<code class="literal">
CHAR
</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>
column value, you must take
into account the character set used for that column and whether
the value contains multibyte characters. In particular, when
using a UTF-8 Unicode character set, you must keep in mind that
not all characters use the same number of bytes.
<code class="literal">
utf8mb3
</code>
and
<code class="literal">
utf8mb4
</code>
character sets can require up to three and four bytes per
character, respectively. For a breakdown of the storage used for
different categories of
<code class="literal">
utf8mb3
</code>
or
<code class="literal">
utf8mb4
</code>
characters, see
<a class="xref" href="charset-unicode.html" title="12.9 Unicode Support">
Section 12.9, “Unicode Support”
</a>
.
</p>
<a class="indexterm" name="idm46045210497120">
</a>
<a class="indexterm" name="idm46045210495632">
</a>
<a class="indexterm" name="idm46045210494144">
</a>
<p>
<a class="link" href="char.html" title="13.3.2 The CHAR and VARCHAR Types">
<code class="literal">
VARCHAR
</code>
</a>
,
<a class="link" href="binary-varbinary.html" title="13.3.3 The BINARY and VARBINARY Types">
<code class="literal">
VARBINARY
</code>
</a>
, and the
<a class="link" href="blob.html" title="13.3.4 The BLOB and TEXT Types">
<code class="literal">
BLOB
</code>
</a>
and
<a class="link" href="blob.html" title="13.3.4 The BLOB and TEXT Types">
<code class="literal">
TEXT
</code>
</a>
types are variable-length
types. For each, the storage requirements depend on these
factors:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
The actual length of the column value
</p>
</li>
<li class="listitem">
<p>
The column's maximum possible length
</p>
</li>
<li class="listitem">
<p>
The character set used for the column, because some
character sets contain multibyte characters
</p>
</li>
</ul>
</div>
<p>
For example, a
<code class="literal">
VARCHAR(255)
</code>
column can hold a
string with a maximum length of 255 characters. Assuming that
the column uses the
<code class="literal">
latin1
</code>
character set (one
byte per character), the actual storage required is the length
of the string (
<em class="replaceable">
<code>
L
</code>
</em>
), plus one byte to
record the length of the string. For the string
<code class="literal">
'abcd'
</code>
,
<em class="replaceable">
<code>
L
</code>
</em>
is 4 and
the storage requirement is five bytes. If the same column is
instead declared to use the
<code class="literal">
ucs2
</code>
double-byte
character set, the storage requirement is 10 bytes: The length
of
<code class="literal">
'abcd'
</code>
is eight bytes and the column
requires two bytes to store lengths because the maximum length
is greater than 255 (up to 510 bytes).
</p>
<p>
The effective maximum number of
<span class="emphasis">
<em>
bytes
</em>
</span>
that
can be stored in 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="binary-varbinary.html" title="13.3.3 The BINARY and VARBINARY Types">
<code class="literal">
VARBINARY
</code>
</a>
column is subject to
the maximum row size of 65,535 bytes, which is shared among all
columns. For a
<a class="link" href="char.html" title="13.3.2 The CHAR and VARCHAR Types">
<code class="literal">
VARCHAR
</code>
</a>
column
that stores multibyte characters, the effective maximum number
of
<span class="emphasis">
<em>
characters
</em>
</span>
is less. For example,
<code class="literal">
utf8mb4
</code>
characters can require up to four
bytes per character, so a
<a class="link" href="char.html" title="13.3.2 The CHAR and VARCHAR Types">
<code class="literal">
VARCHAR
</code>
</a>
column that uses the
<code class="literal">
utf8mb4
</code>
character set
can be declared to be a maximum of 16,383 characters. See
<a class="xref" href="column-count-limit.html" title="10.4.7 Limits on Table Column Count and Row Size">
Section 10.4.7, “Limits on Table Column Count and Row Size”
</a>
.
</p>
<p>
<code class="literal">
InnoDB
</code>
encodes fixed-length fields greater
than or equal to 768 bytes in length as variable-length fields,
which can be stored off-page. For example, a
<code class="literal">
CHAR(255)
</code>
column can exceed 768 bytes if the
maximum byte length of the character set is greater than 3, as
it is with
<code class="literal">
utf8mb4
</code>
.
</p>
<p>
The
<a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4">
<code class="literal">
NDB
</code>
</a>
storage engine supports
variable-width columns. This means that a
<a class="link" href="char.html" title="13.3.2 The CHAR and VARCHAR Types">
<code class="literal">
VARCHAR
</code>
</a>
column in an NDB Cluster
table requires the same amount of storage as would any other
storage engine, with the exception that such values are 4-byte
aligned. Thus, the string
<code class="literal">
'abcd'
</code>
stored in a
<code class="literal">
VARCHAR(50)
</code>
column using the
<code class="literal">
latin1
</code>
character set requires 8 bytes (rather
than 5 bytes for the same column value in a
<code class="literal">
MyISAM
</code>
table).
</p>
<p>
<a class="link" href="blob.html" title="13.3.4 The BLOB and TEXT Types">
<code class="literal">
TEXT
</code>
</a>
,
<a class="link" href="blob.html" title="13.3.4 The BLOB and TEXT Types">
<code class="literal">
BLOB
</code>
</a>
, and
<a class="link" href="json.html" title="13.5 The JSON Data Type">
<code class="literal">
JSON
</code>
</a>
columns are implemented
differently in the
<a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4">
<code class="literal">
NDB
</code>
</a>
storage
engine, wherein each row in the column is made up of two
separate parts. One of these is of fixed size (256 bytes for
<code class="literal">
TEXT
</code>
and
<code class="literal">
BLOB
</code>
, 4000 bytes
for
<code class="literal">
JSON
</code>
), and is actually stored in the
original table. The other consists of any data in excess of 256
bytes, which is stored in a hidden blob parts table. The size of
the rows in this second table are determined by the exact type
of the column, as shown in the following table:
</p>
<div class="informaltable">
<table summary="NDB blob table row lengths for TEXT and BLOB types.">
<colgroup>
<col style="width: 40%"/>
<col style="width: 60%"/>
</colgroup>
<thead>
<tr>
<th>
Type
</th>
<th>
Blob Part Size
</th>
</tr>
</thead>
<tbody>
<tr>
<td>
<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>
</td>
<td>
2000
</td>
</tr>
<tr>
<td>
<a class="link" href="blob.html" title="13.3.4 The BLOB and TEXT Types">
<code class="literal">
MEDIUMBLOB
</code>
</a>
,
<a class="link" href="blob.html" title="13.3.4 The BLOB and TEXT Types">
<code class="literal">
MEDIUMTEXT
</code>
</a>
</td>
<td>
4000
</td>
</tr>
<tr>
<td>
<a class="link" href="blob.html" title="13.3.4 The BLOB and TEXT Types">
<code class="literal">
LONGBLOB
</code>
</a>
,
<a class="link" href="blob.html" title="13.3.4 The BLOB and TEXT Types">
<code class="literal">
LONGTEXT
</code>
</a>
</td>
<td>
13948
</td>
</tr>
<tr>
<td>
<a class="link" href="json.html" title="13.5 The JSON Data Type">
<code class="literal">
JSON
</code>
</a>
</td>
<td>
8100
</td>
</tr>
</tbody>
</table>
</div>
<p>
This means that the size of a
<a class="link" href="blob.html" title="13.3.4 The BLOB and TEXT Types">
<code class="literal">
TEXT
</code>
</a>
column is 256 if
<em class="replaceable">
<code>
size
</code>
</em>
<= 256 (where
<em class="replaceable">
<code>
size
</code>
</em>
represents the size of the row);
otherwise, the size is 256 +
<em class="replaceable">
<code>
size
</code>
</em>
+ (2000 ×
(
<em class="replaceable">
<code>
size
</code>
</em>
− 256) % 2000).
</p>
<p>
No blob parts are stored separately by
<code class="literal">
NDB
</code>
for
<code class="literal">
TINYBLOB
</code>
or
<code class="literal">
TINYTEXT
</code>
column values.
</p>
<p>
You can increase the size of an
<code class="literal">
NDB
</code>
blob
column's blob part to the maximum of 13948 using
<code class="literal">
NDB_COLUMN
</code>
in a column comment when creating
or altering the parent table.
<code class="literal">
NDB
</code>
also
supports setting the inline size for a
<code class="literal">
TEXT
</code>
,
<code class="literal">
BLOB
</code>
, or
<code class="literal">
JSON
</code>
column,
using
<code class="literal">
NDB_TABLE
</code>
in a column comment. See
<a class="xref" href="create-table-ndb-comment-options.html#create-table-ndb-comment-column-options" title="NDB_COLUMN Options">
NDB_COLUMN Options
</a>
, for
more information.
</p>
<a class="indexterm" name="idm46045210419472">
</a>
<p>
The size of an
<a class="link" href="enum.html" title="13.3.5 The ENUM Type">
<code class="literal">
ENUM
</code>
</a>
object is
determined by the number of different enumeration values. One
byte is used for enumerations with up to 255 possible values.
Two bytes are used for enumerations having between 256 and
65,535 possible values. See
<a class="xref" href="enum.html" title="13.3.5 The ENUM Type">
Section 13.3.5, “The ENUM Type”
</a>
.
</p>
<a class="indexterm" name="idm46045210415408">
</a>
<p>
The size of a
<a class="link" href="set.html" title="13.3.6 The SET Type">
<code class="literal">
SET
</code>
</a>
object is
determined by the number of different set members. If the set
size is
<em class="replaceable">
<code>
N
</code>
</em>
, the object occupies
<code class="literal">
(
<em class="replaceable">
<code>
N
</code>
</em>
+7)/8
</code>
bytes,
rounded up to 1, 2, 3, 4, or 8 bytes. A
<a class="link" href="set.html" title="13.3.6 The SET Type">
<code class="literal">
SET
</code>
</a>
can have a maximum of 64
members. See
<a class="xref" href="set.html" title="13.3.6 The SET Type">
Section 13.3.6, “The SET Type”
</a>
.
</p>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h3 class="title">
<a name="data-types-storage-reqs-gis">
</a>
Spatial Type Storage Requirements
</h3>
</div>
</div>
</div>
<a class="indexterm" name="idm46045210407584">
</a>
<a class="indexterm" name="idm46045210406096">
</a>
<a class="indexterm" name="idm46045210404608">
</a>
<p>
MySQL stores geometry values using 4 bytes to indicate the SRID
followed by the WKB representation of the value. The
<a class="link" href="string-functions.html#function_length">
<code class="literal">
LENGTH()
</code>
</a>
function returns the
space in bytes required for value storage.
</p>
<p>
For descriptions of WKB and internal storage formats for spatial
values, see
<a class="xref" href="gis-data-formats.html" title="13.4.3 Supported Spatial Data Formats">
Section 13.4.3, “Supported Spatial Data Formats”
</a>
.
</p>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h3 class="title">
<a name="data-types-storage-reqs-json">
</a>
JSON Storage Requirements
</h3>
</div>
</div>
</div>
<p>
In general, the storage requirement for a
<a class="link" href="json.html" title="13.5 The JSON Data Type">
<code class="literal">
JSON
</code>
</a>
column is approximately the
same as for a
<code class="literal">
LONGBLOB
</code>
or
<code class="literal">
LONGTEXT
</code>
column; that is, the space consumed
by a JSON document is roughly the same as it would be for the
document's string representation stored in a column of one
of these types. However, there is an overhead imposed by the
binary encoding, including metadata and dictionaries needed for
lookup, of the individual values stored in the JSON document.
For example, a string stored in a JSON document requires 4 to 10
bytes additional storage, depending on the length of the string
and the size of the object or array in which it is stored.
</p>
<p>
In addition, MySQL imposes a limit on the size of any JSON
document stored in a
<code class="literal">
JSON
</code>
column such that it
cannot be any larger than the value of
<a class="link" href="server-system-variables.html#sysvar_max_allowed_packet">
<code class="literal">
max_allowed_packet
</code>
</a>
.
</p>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/faqs-sql-modes.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h2 class="title">
<a name="faqs-sql-modes">
</a>
A.3 MySQL 8.4 FAQ: Server SQL Mode
</h2>
</div>
</div>
</div>
<div class="qandaset">
<a name="idm46045056413088">
</a>
<dl>
<dt>
A.3.1.
<a href="faqs-sql-modes.html#faq-mysql-what-sql-modes">
What are server SQL modes?
</a>
</dt>
<dt>
A.3.2.
<a href="faqs-sql-modes.html#faq-mysql-count-sql-modes">
How many server SQL modes are there?
</a>
</dt>
<dt>
A.3.3.
<a href="faqs-sql-modes.html#faq-mysql-how-see-sql-mode">
How do you determine the server SQL mode?
</a>
</dt>
<dt>
A.3.4.
<a href="faqs-sql-modes.html#faq-mysql-sql-mode-dependency">
Is the mode dependent on the database or connection?
</a>
</dt>
<dt>
A.3.5.
<a href="faqs-sql-modes.html#faq-mysql-extend-strict-mode">
Can the rules for strict mode be extended?
</a>
</dt>
<dt>
A.3.6.
<a href="faqs-sql-modes.html#faq-mysql-strict-impact">
Does strict mode impact performance?
</a>
</dt>
<dt>
A.3.7.
<a href="faqs-sql-modes.html#faq-mysql-what-default-mode">
What is the default server SQL mode when MySQL 8.4
is installed?
</a>
</dt>
</dl>
<table border="0" style="width: 100%;">
<colgroup>
<col align="left" width="1%"/>
<col/>
</colgroup>
<tbody>
<tr class="question">
<td align="left" valign="top">
<a name="faq-mysql-what-sql-modes">
</a>
<a name="idm46045056412272">
</a>
<p>
<b>
A.3.1.
</b>
</p>
</td>
<td align="left" valign="top">
<p>
What are server SQL modes?
</p>
</td>
</tr>
<tr class="answer">
<td align="left" valign="top">
</td>
<td align="left" valign="top">
<p>
Server SQL modes define what SQL syntax MySQL should support and
what kind of data validation checks it should perform. This
makes it easier to use MySQL in different environments and to
use MySQL together with other database servers. The MySQL Server
apply these modes individually to different clients. For more
information, see
<a class="xref" href="sql-mode.html" title="7.1.11 Server SQL Modes">
Section 7.1.11, “Server SQL Modes”
</a>
.
</p>
</td>
</tr>
<tr class="question">
<td align="left" valign="top">
<a name="faq-mysql-count-sql-modes">
</a>
<a name="idm46045056408864">
</a>
<p>
<b>
A.3.2.
</b>
</p>
</td>
<td align="left" valign="top">
<p>
How many server SQL modes are there?
</p>
</td>
</tr>
<tr class="answer">
<td align="left" valign="top">
</td>
<td align="left" valign="top">
<p>
Each mode can be independently switched on and off. See
<a class="xref" href="sql-mode.html" title="7.1.11 Server SQL Modes">
Section 7.1.11, “Server SQL Modes”
</a>
, for a complete list of available
modes.
</p>
</td>
</tr>
<tr class="question">
<td align="left" valign="top">
<a name="faq-mysql-how-see-sql-mode">
</a>
<a name="idm46045056406096">
</a>
<p>
<b>
A.3.3.
</b>
</p>
</td>
<td align="left" valign="top">
<p>
How do you determine the server SQL mode?
</p>
</td>
</tr>
<tr class="answer">
<td align="left" valign="top">
</td>
<td align="left" valign="top">
<p>
You can set the default SQL mode (for
<a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
<span class="command">
<strong>
mysqld
</strong>
</span>
</a>
startup) with the
<a class="link" href="server-options.html#option_mysqld_sql-mode">
<code class="option">
--sql-mode
</code>
</a>
option. Using the statement
<a class="link" href="set-variable.html" title="15.7.6.1 SET Syntax for Variable Assignment">
<code class="literal">
SET
[GLOBAL|SESSION]
sql_mode='
<em class="replaceable">
<code>
modes
</code>
</em>
'
</code>
</a>
, you can
change the settings from within a connection, either locally to
the connection, or to take effect globally. You can retrieve the
current mode by issuing a
<code class="literal">
SELECT @@sql_mode
</code>
statement.
</p>
</td>
</tr>
<tr class="question">
<td align="left" valign="top">
<a name="faq-mysql-sql-mode-dependency">
</a>
<a name="idm46045056399280">
</a>
<p>
<b>
A.3.4.
</b>
</p>
</td>
<td align="left" valign="top">
<p>
Is the mode dependent on the database or connection?
</p>
</td>
</tr>
<tr class="answer">
<td align="left" valign="top">
</td>
<td align="left" valign="top">
<p>
A mode is not linked to a particular database. Modes can be set
locally to the session (connection), or globally for the server.
you can change these settings using
<a class="link" href="set-variable.html" title="15.7.6.1 SET Syntax for Variable Assignment">
<code class="literal">
SET
[GLOBAL|SESSION]
sql_mode='
<em class="replaceable">
<code>
modes
</code>
</em>
'
</code>
</a>
.
</p>
</td>
</tr>
<tr class="question">
<td align="left" valign="top">
<a name="faq-mysql-extend-strict-mode">
</a>
<a name="idm46045056395392">
</a>
<p>
<b>
A.3.5.
</b>
</p>
</td>
<td align="left" valign="top">
<p>
Can the rules for strict mode be extended?
</p>
</td>
</tr>
<tr class="answer">
<td align="left" valign="top">
</td>
<td align="left" valign="top">
<p>
When we refer to
<span class="emphasis">
<em>
strict mode
</em>
</span>
, we mean a
mode where at least one of the modes
<a class="link" href="sql-mode.html#sqlmode_traditional">
<code class="literal">
TRADITIONAL
</code>
</a>
,
<a class="link" href="sql-mode.html#sqlmode_strict_trans_tables">
<code class="literal">
STRICT_TRANS_TABLES
</code>
</a>
, or
<a class="link" href="sql-mode.html#sqlmode_strict_all_tables">
<code class="literal">
STRICT_ALL_TABLES
</code>
</a>
is enabled.
Options can be combined, so you can add restrictions to a mode.
See
<a class="xref" href="sql-mode.html" title="7.1.11 Server SQL Modes">
Section 7.1.11, “Server SQL Modes”
</a>
, for more information.
</p>
</td>
</tr>
<tr class="question">
<td align="left" valign="top">
<a name="faq-mysql-strict-impact">
</a>
<a name="idm46045056388432">
</a>
<p>
<b>
A.3.6.
</b>
</p>
</td>
<td align="left" valign="top">
<p>
Does strict mode impact performance?
</p>
</td>
</tr>
<tr class="answer">
<td align="left" valign="top">
</td>
<td align="left" valign="top">
<p>
The intensive validation of input data that some settings
requires more time than if the validation is not done. While the
performance impact is not that great, if you do not require such
validation (perhaps your application already handles all of
this), then MySQL gives you the option of leaving strict mode
disabled. However, if you do require it, strict mode can provide
such validation.
</p>
</td>
</tr>
<tr class="question">
<td align="left" valign="top">
<a name="faq-mysql-what-default-mode">
</a>
<a name="idm46045056386000">
</a>
<p>
<b>
A.3.7.
</b>
</p>
</td>
<td align="left" valign="top">
<p>
What is the default server SQL mode when MySQL 8.4
is installed?
</p>
</td>
</tr>
<tr class="answer">
<td align="left" valign="top">
</td>
<td align="left" valign="top">
<p>
The default SQL mode in MySQL 8.0 includes these modes:
<a class="link" href="sql-mode.html#sqlmode_only_full_group_by">
<code class="literal">
ONLY_FULL_GROUP_BY
</code>
</a>
,
<a class="link" href="sql-mode.html#sqlmode_strict_trans_tables">
<code class="literal">
STRICT_TRANS_TABLES
</code>
</a>
,
<a class="link" href="sql-mode.html#sqlmode_no_zero_in_date">
<code class="literal">
NO_ZERO_IN_DATE
</code>
</a>
,
<a class="link" href="sql-mode.html#sqlmode_no_zero_date">
<code class="literal">
NO_ZERO_DATE
</code>
</a>
,
<a class="link" href="sql-mode.html#sqlmode_error_for_division_by_zero">
<code class="literal">
ERROR_FOR_DIVISION_BY_ZERO
</code>
</a>
,
and
<a class="link" href="sql-mode.html#sqlmode_no_engine_substitution">
<code class="literal">
NO_ENGINE_SUBSTITUTION
</code>
</a>
.
</p>
<p>
For information about all available modes and default MySQL
behavior, see
<a class="xref" href="sql-mode.html" title="7.1.11 Server SQL Modes">
Section 7.1.11, “Server SQL Modes”
</a>
.
</p>
</td>
</tr>
</tbody>
</table>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/connector-j-info.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h2 class="title">
<a name="connector-j-info">
</a>
31.2 MySQL Connector/J
</h2>
</div>
</div>
</div>
<a class="indexterm" name="idm46045060384880">
</a>
<a class="indexterm" name="idm46045060383840">
</a>
<p>
The MySQL Connector/J manual is published in standalone form, not as
part of the MySQL Reference Manual. For information, see these
documents:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
Main manual:
<a class="ulink" href="/doc/connector-j/en/" target="_top">
MySQL
Connector/J Developer Guide
</a>
</p>
</li>
<li class="listitem">
<p>
Release notes:
<a class="ulink" href="/doc/relnotes/connector-j/en/" target="_top">
MySQL
Connector/J Release Notes
</a>
</p>
</li>
</ul>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/alter-instance.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="alter-instance">
</a>
15.1.5 ALTER INSTANCE Statement
</h3>
</div>
</div>
</div>
<a class="indexterm" name="idm46045189736672">
</a>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa93815863"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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">INSTANCE</span> <em class="replaceable">instance_action</em>
<em class="replaceable">instance_action</em>: {
<span class="token operator">|</span> {<span class="token keyword">ENABLE</span><span class="token operator">|</span><span class="token keyword">DISABLE</span>} INNODB REDO_LOG
<span class="token operator">|</span> <span class="token keyword">ROTATE</span> INNODB <span class="token keyword">MASTER</span> <span class="token keyword">KEY</span>
<span class="token operator">|</span> <span class="token keyword">ROTATE</span> <span class="token keyword">BINLOG</span> <span class="token keyword">MASTER</span> <span class="token keyword">KEY</span>
<span class="token operator">|</span> <span class="token keyword">RELOAD</span> <span class="token keyword">TLS</span>
<span class="token punctuation">[</span><span class="token keyword">FOR</span> <span class="token keyword">CHANNEL</span> {mysql_main <span class="token operator">|</span> mysql_admin}<span class="token punctuation">]</span>
<span class="token punctuation">[</span><span class="token keyword">NO</span> <span class="token keyword">ROLLBACK</span> <span class="token keyword">ON</span> <span class="token keyword">ERROR</span><span class="token punctuation">]</span>
<span class="token operator">|</span> <span class="token keyword">RELOAD</span> KEYRING
}</code></pre>
</div>
<p>
<code class="literal">
ALTER INSTANCE
</code>
defines actions applicable to a
MySQL server instance. The statement supports these actions:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<a name="alter-instance-enable-disable-innodb-redo-log">
</a>
<code class="literal">
ALTER INSTANCE {ENABLE | DISABLE} INNODB
REDO_LOG
</code>
</p>
<p>
This action enables or disables
<code class="literal">
InnoDB
</code>
redo
logging. Redo logging is enabled by default. This feature is
intended only for loading data into a new MySQL instance. The
statement is not written to the binary log.
</p>
<div class="warning" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Warning
</div>
<p>
<span class="emphasis">
<em>
Do not disable redo logging on a production
system.
</em>
</span>
While it is permitted to shut down and
restart the server while redo logging is disabled, an
unexpected server stoppage while redo logging is disabled
can cause data loss and instance corruption.
</p>
</div>
<p>
An
<a class="link" href="alter-instance.html" title="15.1.5 ALTER INSTANCE Statement">
<code class="literal">
ALTER
INSTANCE [ENABLE|DISABLE] INNODB REDO_LOG
</code>
</a>
operation
requires an exclusive backup lock, which prevents other
<a class="link" href="alter-instance.html" title="15.1.5 ALTER INSTANCE Statement">
<code class="literal">
ALTER INSTANCE
</code>
</a>
operations from
executing concurrently. Other
<a class="link" href="alter-instance.html" title="15.1.5 ALTER INSTANCE Statement">
<code class="literal">
ALTER
INSTANCE
</code>
</a>
operations must wait for the lock to be
released before executing.
</p>
<p>
For more information, see
<a class="xref" href="innodb-redo-log.html#innodb-disable-redo-logging" title="Disabling Redo Logging">
Disabling Redo Logging
</a>
.
</p>
</li>
<li class="listitem">
<p>
<a name="alter-instance-rotate-innodb-master-key">
</a>
<code class="literal">
ALTER INSTANCE ROTATE INNODB MASTER KEY
</code>
</p>
<p>
This action rotates the master encryption key used for
<code class="literal">
InnoDB
</code>
tablespace encryption. Key rotation
requires the
<a class="link" href="privileges-provided.html#priv_encryption-key-admin">
<code class="literal">
ENCRYPTION_KEY_ADMIN
</code>
</a>
or
<a class="link" href="privileges-provided.html#priv_super">
<code class="literal">
SUPER
</code>
</a>
privilege. To perform
this action, a keyring plugin must be installed and
configured. For instructions, see
<a class="xref" href="keyring.html" title="8.4.4 The MySQL Keyring">
Section 8.4.4, “The MySQL Keyring”
</a>
.
</p>
<p>
<code class="literal">
ALTER INSTANCE ROTATE INNODB MASTER KEY
</code>
supports concurrent DML. However, it cannot be run
concurrently with
<a class="link" href="create-table.html" title="15.1.20 CREATE TABLE Statement">
<code class="literal">
CREATE TABLE ...
ENCRYPTION
</code>
</a>
or
<a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement">
<code class="literal">
ALTER TABLE ...
ENCRYPTION
</code>
</a>
operations, and locks are taken to
prevent conflicts that could arise from concurrent execution
of these statements. If one of the conflicting statements is
running, it must complete before another can proceed.
</p>
<p>
<code class="literal">
ALTER INSTANCE ROTATE INNODB MASTER KEY
</code>
statements are written to the binary log so that they can be
executed on replicated servers.
</p>
<p>
For additional
<code class="literal">
ALTER INSTANCE ROTATE INNODB MASTER
KEY
</code>
usage information, 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>
<a name="alter-instance-rotate-binlog-master-key">
</a>
<code class="literal">
ALTER INSTANCE ROTATE BINLOG MASTER KEY
</code>
</p>
<p>
This action rotates the binary log master key used for binary
log encryption. Key rotation for the binary log master key
requires the
<a class="link" href="privileges-provided.html#priv_binlog-encryption-admin">
<code class="literal">
BINLOG_ENCRYPTION_ADMIN
</code>
</a>
or
<a class="link" href="privileges-provided.html#priv_super">
<code class="literal">
SUPER
</code>
</a>
privilege. The statement
cannot be used if the
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_encryption">
<code class="literal">
binlog_encryption
</code>
</a>
system
variable is set to
<code class="literal">
OFF
</code>
. To perform this
action, a keyring plugin must be installed and configured. For
instructions, see
<a class="xref" href="keyring.html" title="8.4.4 The MySQL Keyring">
Section 8.4.4, “The MySQL Keyring”
</a>
.
</p>
<p>
<code class="literal">
ALTER INSTANCE ROTATE BINLOG MASTER KEY
</code>
actions are not written to the binary log and are not executed
on replicas. Binary log master key rotation can therefore be
carried out in replication environments including a mix of
MySQL versions. To schedule regular rotation of the binary log
master key on all applicable source and replica servers, you
can enable the MySQL Event Scheduler on each server and issue
the
<code class="literal">
ALTER INSTANCE ROTATE BINLOG MASTER KEY
</code>
statement using a
<a class="link" href="create-event.html" title="15.1.13 CREATE EVENT Statement">
<code class="literal">
CREATE EVENT
</code>
</a>
statement. If you rotate the binary log master key because you
suspect that the current or any of the previous binary log
master keys might have been compromised, issue the statement
on every applicable source and replica server, which enables
you to verify immediate compliance.
</p>
<p>
For additional
<code class="literal">
ALTER INSTANCE ROTATE BINLOG MASTER
KEY
</code>
usage information, including what to do if the
process does not complete correctly or is interrupted by an
unexpected server halt, 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>
<a name="alter-instance-reload-tls">
</a>
<code class="literal">
ALTER INSTANCE RELOAD TLS
</code>
</p>
<p>
This action reconfigures a TLS context from the current values
of the system variables that define the context. It also
updates the status variables that reflect the active context
values. This action requires the
<a class="link" href="privileges-provided.html#priv_connection-admin">
<code class="literal">
CONNECTION_ADMIN
</code>
</a>
privilege. For
additional information about reconfiguring the TLS context,
including which system and status variables are
context-related, see
<a class="xref" href="using-encrypted-connections.html#using-encrypted-connections-server-side-runtime-configuration" title="Server-Side Runtime Configuration and Monitoring for Encrypted Connections">
Server-Side Runtime Configuration and Monitoring for Encrypted
Connections
</a>
.
</p>
<p>
By default, the statement reloads the TLS context for the main
connection interface. If the
<code class="literal">
FOR CHANNEL
</code>
clause is given, the statement reloads the TLS context for the
named channel:
<code class="literal">
mysql_main
</code>
for the main
connection interface,
<code class="literal">
mysql_admin
</code>
for the
administrative connection interface. For information about the
different interfaces, see
<a class="xref" href="connection-interfaces.html" title="7.1.12.1 Connection Interfaces">
Section 7.1.12.1, “Connection Interfaces”
</a>
. The updated TLS
context properties are exposed in the Performance Schema
<a class="link" href="performance-schema-tls-channel-status-table.html" title="29.12.22.9 The tls_channel_status Table">
<code class="literal">
tls_channel_status
</code>
</a>
table. See
<a class="xref" href="performance-schema-tls-channel-status-table.html" title="29.12.22.9 The tls_channel_status Table">
Section 29.12.22.9, “The tls_channel_status Table”
</a>
.
</p>
<p>
Updating the TLS context for the main interface may also
affect the administrative interface because unless some
nondefault TLS value is configured for that interface, it uses
the same TLS context as the main interface.
</p>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
When you reload the TLS context, OpenSSL reloads the file
containing the CRL (certificate revocation list) as part of
the process. If the CRL file is large, the server allocates
a large chunk of memory (ten times the file size), which is
doubled while the new instance is being loaded and the old
one has not yet been released. The process resident memory
is not immediately reduced after a large allocation is
freed, so if you issue the
<code class="literal">
ALTER INSTANCE RELOAD
TLS
</code>
statement repeatedly with a large CRL file,
the process resident memory usage may grow as a result of
this.
</p>
</div>
<p>
By default, the
<code class="literal">
RELOAD TLS
</code>
action rolls
back with an error and has no effect if the configuration
values do not permit creation of the new TLS context. The
previous context values continue to be used for new
connections. If the optional
<code class="literal">
NO ROLLBACK ON
ERROR
</code>
clause is given and the new context cannot be
created, rollback does not occur. Instead, a warning is
generated and encryption is disabled for new connections on
the interface to which the statement applies.
</p>
<p>
<code class="literal">
ALTER INSTANCE RELOAD TLS
</code>
statements are
not written to the binary log (and thus are not replicated).
TLS configuration is local and depends on local files not
necessarily present on all servers involved.
</p>
</li>
<li class="listitem">
<p>
<a name="alter-instance-reload-keyring">
</a>
<code class="literal">
ALTER INSTANCE RELOAD KEYRING
</code>
</p>
<p>
If a keyring component is installed, this action tells the
component to re-read its configuration file and reinitialize
any keyring in-memory data. If you modify the component
configuration at runtime, the new configuration does not take
effect until you perform this action. Keyring reloading
requires the
<a class="link" href="privileges-provided.html#priv_encryption-key-admin">
<code class="literal">
ENCRYPTION_KEY_ADMIN
</code>
</a>
privilege.
</p>
<p>
This action enables reconfiguring only the currently installed
keyring component. It does not enable changing which component
is installed. For example, if you change the configuration for
the installed keyring component,
<a class="link" href="alter-instance.html#alter-instance-reload-keyring">
<code class="literal">
ALTER
INSTANCE RELOAD KEYRING
</code>
</a>
causes the new configuration
to take effect. On the other hand, if you change the keyring
component named in the server manifest file,
<a class="link" href="alter-instance.html#alter-instance-reload-keyring">
<code class="literal">
ALTER INSTANCE RELOAD KEYRING
</code>
</a>
has no effect and the current component remains installed.
</p>
<p>
<code class="literal">
ALTER INSTANCE RELOAD KEYRING
</code>
statements
are not written to the binary log (and thus are not
replicated).
</p>
</li>
</ul>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/binary-varbinary.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="binary-varbinary">
</a>
13.3.3 The BINARY and VARBINARY Types
</h3>
</div>
</div>
</div>
<a class="indexterm" name="idm46045212655488">
</a>
<a class="indexterm" name="idm46045212654448">
</a>
<a class="indexterm" name="idm46045212653376">
</a>
<a class="indexterm" name="idm46045212651888">
</a>
<p>
The
<code class="literal">
BINARY
</code>
and
<code class="literal">
VARBINARY
</code>
types are similar to
<a class="link" href="char.html" title="13.3.2 The CHAR and VARCHAR Types">
<code class="literal">
CHAR
</code>
</a>
and
<a class="link" href="char.html" title="13.3.2 The CHAR and VARCHAR Types">
<code class="literal">
VARCHAR
</code>
</a>
, except that they store
binary strings rather than nonbinary strings. That is, they
store byte strings rather than character strings. This means
they have the
<code class="literal">
binary
</code>
character set and
collation, and comparison and sorting are based on the numeric
values of the bytes in the values.
</p>
<p>
The permissible maximum length is the same for
<code class="literal">
BINARY
</code>
and
<code class="literal">
VARBINARY
</code>
as it
is for
<a class="link" href="char.html" title="13.3.2 The CHAR and VARCHAR Types">
<code class="literal">
CHAR
</code>
</a>
and
<a class="link" href="char.html" title="13.3.2 The CHAR and VARCHAR Types">
<code class="literal">
VARCHAR
</code>
</a>
, except that the length
for
<code class="literal">
BINARY
</code>
and
<code class="literal">
VARBINARY
</code>
is measured in bytes rather than characters.
</p>
<p>
The
<code class="literal">
BINARY
</code>
and
<code class="literal">
VARBINARY
</code>
data types are distinct from the
<code class="literal">
CHAR BINARY
</code>
and
<code class="literal">
VARCHAR BINARY
</code>
data types. For the latter
types, the
<code class="literal">
BINARY
</code>
attribute does not cause
the column to be treated as a binary string column. Instead, it
causes the binary (
<code class="literal">
_bin
</code>
) collation for the
column character set (or the table default character set if no
column character set is specified) to be used, and the column
itself stores nonbinary character strings rather than binary
byte strings. For example, if the default character set is
<code class="literal">
utf8mb4
</code>
,
<code class="literal">
CHAR(5) BINARY
</code>
is
treated as
<code class="literal">
CHAR(5) CHARACTER SET utf8mb4 COLLATE
utf8mb4_bin
</code>
. This differs from
<code class="literal">
BINARY(5)
</code>
, which stores 5-byte binary strings
that have the
<code class="literal">
binary
</code>
character set and
collation. For information about the differences between the
<code class="literal">
binary
</code>
collation of the
<code class="literal">
binary
</code>
character set and the
<code class="literal">
_bin
</code>
collations of nonbinary character sets,
see
<a class="xref" href="charset-binary-collations.html" title="12.8.5 The binary Collation Compared to _bin Collations">
Section 12.8.5, “The binary Collation Compared to _bin Collations”
</a>
.
</p>
<p>
If strict SQL mode is not enabled and you assign a value to a
<code class="literal">
BINARY
</code>
or
<code class="literal">
VARBINARY
</code>
column
that exceeds the column's maximum length, the value is truncated
to fit and a warning is generated. For cases of truncation, to
cause an error to occur (rather than a warning) and suppress
insertion of the value, use strict SQL mode. See
<a class="xref" href="sql-mode.html" title="7.1.11 Server SQL Modes">
Section 7.1.11, “Server SQL Modes”
</a>
.
</p>
<p>
When
<code class="literal">
BINARY
</code>
values are stored, they are
right-padded with the pad value to the specified length. The pad
value is
<code class="literal">
0x00
</code>
(the zero byte). Values are
right-padded with
<code class="literal">
0x00
</code>
for inserts, and no
trailing bytes are removed for retrievals. All bytes are
significant in comparisons, including
<code class="literal">
ORDER
BY
</code>
and
<code class="literal">
DISTINCT
</code>
operations.
<code class="literal">
0x00
</code>
and space differ in comparisons, with
<code class="literal">
0x00
</code>
sorting before space.
</p>
<p>
Example: For a
<code class="literal">
BINARY(3)
</code>
column,
<code class="literal">
'a '
</code>
becomes
<code class="literal">
'a \0'
</code>
when inserted.
<code class="literal">
'a\0'
</code>
becomes
<code class="literal">
'a\0\0'
</code>
when
inserted. Both inserted values remain unchanged for retrievals.
</p>
<p>
For
<code class="literal">
VARBINARY
</code>
, there is no padding for
inserts and no bytes are stripped for retrievals. All bytes are
significant in comparisons, including
<code class="literal">
ORDER
BY
</code>
and
<code class="literal">
DISTINCT
</code>
operations.
<code class="literal">
0x00
</code>
and space differ in comparisons, with
<code class="literal">
0x00
</code>
sorting before space.
</p>
<p>
For those cases where trailing pad bytes are stripped or
comparisons ignore them, if a column has an index that requires
unique values, inserting values into the column that differ only
in number of trailing pad bytes results in a duplicate-key
error. For example, if a table contains
<code class="literal">
'a'
</code>
,
an attempt to store
<code class="literal">
'a\0'
</code>
causes a
duplicate-key error.
</p>
<p>
You should consider the preceding padding and stripping
characteristics carefully if you plan to use the
<code class="literal">
BINARY
</code>
data type for storing binary data and
you require that the value retrieved be exactly the same as the
value stored. The following example illustrates how
<code class="literal">
0x00
</code>
-padding of
<code class="literal">
BINARY
</code>
values affects column value comparisons:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa75270060"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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>c <span class="token datatype">BINARY</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 punctuation">;</span>
<span class="token output">Query OK, 0 rows affected (0.01 sec)</span>
<span class="token prompt">mysql></span> <span class="token keyword">INSERT</span> <span class="token keyword">INTO</span> t <span class="token keyword">SET</span> c <span class="token operator">=</span> <span class="token string">'a'</span><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">SELECT</span> <span class="token function">HEX</span><span class="token punctuation">(</span>c<span class="token punctuation">)</span><span class="token punctuation">,</span> c <span class="token operator">=</span> <span class="token string">'a'</span><span class="token punctuation">,</span> c <span class="token operator">=</span> <span class="token string">'a\0\0'</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 class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><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> HEX(c) <span class="token punctuation">|</span> c = 'a' <span class="token punctuation">|</span> c = 'a\0\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>
<span class="token output"><span class="token punctuation">|</span> 610000 <span class="token punctuation">|</span> 0 <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>
<span class="token output">1 row in set (0.09 sec)</span></code></pre>
</div>
<p>
If the value retrieved must be the same as the value specified
for storage with no padding, it might be preferable to use
<code class="literal">
VARBINARY
</code>
or one of the
<a class="link" href="blob.html" title="13.3.4 The BLOB and TEXT Types">
<code class="literal">
BLOB
</code>
</a>
data types instead.
</p>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
Within 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, binary strings
display using hexadecimal notation, depending on the value of
the
<a class="link" href="mysql-command-options.html#option_mysql_binary-as-hex">
<code class="option">
--binary-as-hex
</code>
</a>
. For more
information about that option, see
<a class="xref" href="mysql.html" title="6.5.1 mysql — The MySQL Command-Line Client">
Section 6.5.1, “mysql — The MySQL Command-Line Client”
</a>
.
</p>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/group-replication-responses-failure.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="group-replication-responses-failure">
</a>
20.7.7 Responses to Failure Detection and Network Partitioning
</h3>
</div>
</div>
</div>
<div class="toc">
<dl class="toc">
<dt>
<span class="section">
<a href="group-replication-responses-failure-expel.html">
20.7.7.1 Expel Timeout
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="group-replication-responses-failure-partition.html">
20.7.7.2 Unreachable Majority Timeout
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="group-replication-responses-failure-rejoin.html">
20.7.7.3 Auto-Rejoin
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="group-replication-responses-failure-exit.html">
20.7.7.4 Exit Action
</a>
</span>
</dt>
</dl>
</div>
<a class="indexterm" name="idm46045132077344">
</a>
<a class="indexterm" name="idm46045132075888">
</a>
<a class="indexterm" name="idm46045132074400">
</a>
<p>
Group Replication's failure detection mechanism is designed to
identify group members that are no longer communicating with the
group, and expel them as and when it seems likely that they have
failed. Having a failure detection mechanism increases the chance
that the group contains a majority of correctly working members,
and that requests from clients are therefore processed correctly.
</p>
<p>
Normally, all group members regularly exchange messages with all
other group members. If a group member does not receive any
messages from a particular fellow member for 5 seconds, when this
detection period ends, it creates a suspicion of the fellow
member. When a suspicion times out, the suspected member is
assumed to have failed, and is expelled from the group. An
expelled member is removed from the membership list seen by the
other members, but it does not know that it has been expelled from
the group, so it sees itself as online and the other members as
unreachable. If the member has not in fact failed (for example,
because it was just disconnected due to a temporary network issue)
and it is able to resume communication with the other members, it
receives a view containing the information that it has been
expelled from the group.
</p>
<p>
The responses of group members, including the failed member
itself, to these situations can be configured at a number of
points in the process. By default, the following behaviors happen
if a member is suspected of having failed:
</p>
<div class="orderedlist">
<ol class="orderedlist" type="1">
<li class="listitem">
<p>
In MySQL 8.4, when a suspicion is created, a
waiting period of 5 seconds is added before the suspicion
times out and the suspected member is liable for expulsion.
</p>
</li>
<li class="listitem">
<p>
If an expelled member resumes communication and realises that
it was expelled, it automatically makes three attempts to
rejoin the group (with 5 minutes between each attempt); if
this auto-rejoin procedure does not work, it then stops trying
to rejoin the group.
</p>
</li>
<li class="listitem">
<p>
When an expelled member is not trying to rejoin the group, it
switches to super-read-only mode and awaits operator
attention.
</p>
</li>
</ol>
</div>
<p>
You can use the Group Replication configuration options described
in this section to change these behaviors either permanently or
temporarily, to suit your system's requirements and your
priorities. If you are experiencing unnecessary expulsions caused
by slower networks or machines, networks with a high rate of
unexpected transient outages, or planned network outages, consider
increasing the expel timeout and auto-rejoin attempts. While a
member is undergoing any of the default behaviors described
previously, although it does not accept writes, reads can still be
performed if the member is still communicating with clients, with
an increasing likelihood of stale reads over time. If avoiding
stale reads is a higher priority for you than avoiding operator
intervention, consider reducing the expel timeout and auto-rejoin
attempts or setting them to zero.
</p>
<p>
Members that have not failed might lose contact with part, but not
all, of the replication group due to a network partition. For
example, in a group of 5 servers (S1, S2, S3, S4, S5), if there is
a disconnection between (S1, S2) and (S3, S4, S5) there is a
network partition. The first group (S1, S2) is now in a minority
because it cannot contact more than half of the group. Any
transactions that are processed by the members in the minority
group are blocked, because the majority of the group is
unreachable, therefore the group cannot achieve quorum. For a
detailed description of this scenario, see
<a class="xref" href="group-replication-network-partitioning.html" title="20.7.8 Handling a Network Partition and Loss of Quorum">
Section 20.7.8, “Handling a Network Partition and Loss of Quorum”
</a>
. In this
situation, the default behavior is for the members in both the
minority and the majority to remain in the group, continue to
accept transactions (although they are blocked on the members in
the minority), and wait for operator intervention. This behavior
is also configurable.
</p>
<p>
Note that where group members are at an older MySQL Server release
that does not support a relevant setting, or at a release with a
different default, they act towards themselves and other group
members according to the default behaviors stated above. For
example, a member that does not support the
<a class="link" href="group-replication-system-variables.html#sysvar_group_replication_member_expel_timeout">
<code class="literal">
group_replication_member_expel_timeout
</code>
</a>
system variable expels other members as soon as an expired
suspicion is detected, and this expulsion is accepted by other
members even if they support the system variable and have a longer
timeout set.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/precision-math-expressions.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="precision-math-expressions">
</a>
14.24.3 Expression Handling
</h3>
</div>
</div>
</div>
<p>
With precision math, exact-value numbers are used as given
whenever possible. For example, numbers in comparisons are used
exactly as given without a change in value. In strict SQL mode,
for
<a class="link" href="insert.html" title="15.2.7 INSERT Statement">
<code class="literal">
INSERT
</code>
</a>
into a column with an
exact data type (
<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>
or
integer), a number is inserted with its exact value if it is
within the column range. When retrieved, the value should be the
same as what was inserted. (If strict SQL mode is not enabled,
truncation for
<a class="link" href="insert.html" title="15.2.7 INSERT Statement">
<code class="literal">
INSERT
</code>
</a>
is
permissible.)
</p>
<p>
Handling of a numeric expression depends on what kind of values
the expression contains:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
If any approximate values are present, the expression is
approximate and is evaluated using floating-point arithmetic.
</p>
</li>
<li class="listitem">
<p>
If no approximate values are present, the expression contains
only exact values. If any exact value contains a fractional
part (a value following the decimal point), the expression is
evaluated using
<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>
exact
arithmetic and has a precision of 65 digits. The term
<span class="quote">
“
<span class="quote">
exact
</span>
”
</span>
is subject to the limits of what can be
represented in binary. For example,
<code class="literal">
1.0/3.0
</code>
can be approximated in decimal notation as
<code class="literal">
.333...
</code>
, but not written as an exact
number, so
<code class="literal">
(1.0/3.0)*3.0
</code>
does not evaluate
to exactly
<code class="literal">
1.0
</code>
.
</p>
</li>
<li class="listitem">
<p>
Otherwise, the expression contains only integer values. The
expression is exact and is evaluated using integer arithmetic
and has a precision the same as
<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>
(64 bits).
</p>
</li>
</ul>
</div>
<p>
If a numeric expression contains any strings, they are converted
to double-precision floating-point values and the expression is
approximate.
</p>
<p>
Inserts into numeric columns are affected by the SQL mode, which
is controlled by the
<a class="link" href="server-system-variables.html#sysvar_sql_mode">
<code class="literal">
sql_mode
</code>
</a>
system variable. (See
<a class="xref" href="sql-mode.html" title="7.1.11 Server SQL Modes">
Section 7.1.11, “Server SQL Modes”
</a>
.) The following
discussion mentions strict mode (selected by the
<a class="link" href="sql-mode.html#sqlmode_strict_all_tables">
<code class="literal">
STRICT_ALL_TABLES
</code>
</a>
or
<a class="link" href="sql-mode.html#sqlmode_strict_trans_tables">
<code class="literal">
STRICT_TRANS_TABLES
</code>
</a>
mode values)
and
<a class="link" href="sql-mode.html#sqlmode_error_for_division_by_zero">
<code class="literal">
ERROR_FOR_DIVISION_BY_ZERO
</code>
</a>
.
To turn on all restrictions, you can simply use
<a class="link" href="sql-mode.html#sqlmode_traditional">
<code class="literal">
TRADITIONAL
</code>
</a>
mode, which includes
both strict mode values and
<a class="link" href="sql-mode.html#sqlmode_error_for_division_by_zero">
<code class="literal">
ERROR_FOR_DIVISION_BY_ZERO
</code>
</a>
:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa47308558"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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> sql_mode<span class="token operator">=</span><span class="token string">'TRADITIONAL'</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
If a number is inserted into an exact type column
(
<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>
or integer), it is
inserted with its exact value if it is within the column range and
precision.
</p>
<p>
If the value has too many digits in the fractional part, rounding
occurs and a note is generated. Rounding is done as described in
<a class="xref" href="precision-math-rounding.html" title="14.24.4 Rounding Behavior">
Section 14.24.4, “Rounding Behavior”
</a>
. Truncation due to
rounding of the fractional part is not an error, even in strict
mode.
</p>
<p>
If the value has too many digits in the integer part, it is too
large (out of range) and is handled as follows:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
If strict mode is not enabled, the value is truncated to the
nearest legal value and a warning is generated.
</p>
</li>
<li class="listitem">
<p>
If strict mode is enabled, an overflow error occurs.
</p>
</li>
</ul>
</div>
<p>
Underflow is not detected, so underflow handling is undefined.
</p>
<p>
For inserts of strings into numeric columns, conversion from
string to number is handled as follows if the string has
nonnumeric contents:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
A string that does not begin with a number cannot be used as a
number and produces an error in strict mode, or a warning
otherwise. This includes the empty string.
</p>
</li>
<li class="listitem">
<p>
A string that begins with a number can be converted, but the
trailing nonnumeric portion is truncated. If the truncated
portion contains anything other than spaces, this produces an
error in strict mode, or a warning otherwise.
</p>
</li>
</ul>
</div>
<p>
By default, division by zero produces a result of
<code class="literal">
NULL
</code>
and no warning. By setting the SQL mode
appropriately, division by zero can be restricted.
</p>
<p>
With the
<a class="link" href="sql-mode.html#sqlmode_error_for_division_by_zero">
<code class="literal">
ERROR_FOR_DIVISION_BY_ZERO
</code>
</a>
SQL
mode enabled, MySQL handles division by zero differently:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
If strict mode is not enabled, a warning occurs.
</p>
</li>
<li class="listitem">
<p>
If strict mode is enabled, inserts and updates involving
division by zero are prohibited, and an error occurs.
</p>
</li>
</ul>
</div>
<p>
In other words, inserts and updates involving expressions that
perform division by zero can be treated as errors, but this
requires
<a class="link" href="sql-mode.html#sqlmode_error_for_division_by_zero">
<code class="literal">
ERROR_FOR_DIVISION_BY_ZERO
</code>
</a>
in
addition to strict mode.
</p>
<p>
Suppose that we have this statement:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa60296509"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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> t <span class="token keyword">SET</span> i <span class="token operator">=</span> <span class="token number">1</span><span class="token operator">/</span><span class="token number">0</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
This is what happens for combinations of strict and
<a class="link" href="sql-mode.html#sqlmode_error_for_division_by_zero">
<code class="literal">
ERROR_FOR_DIVISION_BY_ZERO
</code>
</a>
modes.
</p>
<div class="informaltable">
<table summary="What happens for combinations of strict and ERROR_FOR_DIVISION_BY_ZERO modes.">
<colgroup>
<col style="width: 50%"/>
<col style="width: 50%"/>
</colgroup>
<thead>
<tr>
<th>
<a class="link" href="server-system-variables.html#sysvar_sql_mode">
<code class="literal">
sql_mode
</code>
</a>
Value
</th>
<th>
Result
</th>
</tr>
</thead>
<tbody>
<tr>
<td>
<code class="literal">
''
</code>
(Default)
</td>
<td>
No warning, no error;
<code class="literal">
i
</code>
is set to
<code class="literal">
NULL
</code>
.
</td>
</tr>
<tr>
<td>
strict
</td>
<td>
No warning, no error;
<code class="literal">
i
</code>
is set to
<code class="literal">
NULL
</code>
.
</td>
</tr>
<tr>
<td>
<a class="link" href="sql-mode.html#sqlmode_error_for_division_by_zero">
<code class="literal">
ERROR_FOR_DIVISION_BY_ZERO
</code>
</a>
</td>
<td>
Warning, no error;
<code class="literal">
i
</code>
is set to
<code class="literal">
NULL
</code>
.
</td>
</tr>
<tr>
<td>
strict,
<a class="link" href="sql-mode.html#sqlmode_error_for_division_by_zero">
<code class="literal">
ERROR_FOR_DIVISION_BY_ZERO
</code>
</a>
</td>
<td>
Error condition; no row is inserted.
</td>
</tr>
</tbody>
</table>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/sys-version-patch.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="sys-version-patch">
</a>
30.4.5.22 The version_patch() Function
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045060631712">
</a>
<a class="indexterm" name="idm46045060630240">
</a>
<p>
This function returns the patch release version of the MySQL
server.
</p>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h5 class="title">
<a name="sys-version-patch-parameters">
</a>
Parameters
</h5>
</div>
</div>
</div>
<p>
None.
</p>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h5 class="title">
<a name="sys-version-patch-return-value">
</a>
Return Value
</h5>
</div>
</div>
</div>
<p>
A
<code class="literal">
TINYINT UNSIGNED
</code>
value.
</p>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h5 class="title">
<a name="sys-version-patch-example">
</a>
Example
</h5>
</div>
</div>
</div>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa64784577"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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">VERSION</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">,</span> sys<span class="token punctuation">.</span>version_patch<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>
<span class="token output"><span class="token punctuation">|</span> VERSION() <span class="token punctuation">|</span> sys.version_patch() <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> 8.4.0<span class="token punctuation">-</span>tr <span class="token punctuation">|</span> 26 <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></code></pre>
</div>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/clone-plugin-local.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="clone-plugin-local">
</a>
7.6.7.2 Cloning Data Locally
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045255666704">
</a>
<p>
The clone plugin supports the following syntax for cloning data
locally; that is, cloning data from the local MySQL data
directory to another directory on the same server or node where
the MySQL server instance runs:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa42952767"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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">CLONE</span> <span class="token keyword">LOCAL</span> <span class="token keyword">DATA</span> <span class="token keyword">DIRECTORY</span> <span class="token punctuation">[</span><span class="token operator">=</span><span class="token punctuation">]</span> <span class="token string">'<em class="replaceable">clone_dir</em>'</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
To use
<a class="link" href="clone.html" title="15.7.5 CLONE Statement">
<code class="literal">
CLONE
</code>
</a>
syntax, the clone
plugin must be installed. For installation instructions, see
<a class="xref" href="clone-plugin-installation.html" title="7.6.7.1 Installing the Clone Plugin">
Section 7.6.7.1, “Installing the Clone Plugin”
</a>
.
</p>
<p>
The
<a class="link" href="privileges-provided.html#priv_backup-admin">
<code class="literal">
BACKUP_ADMIN
</code>
</a>
privilege is
required to execute
<a class="link" href="clone.html" title="15.7.5 CLONE Statement">
<code class="literal">
CLONE
LOCAL DATA DIRECTORY
</code>
</a>
statements.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa48760545"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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">GRANT</span> BACKUP_ADMIN <span class="token keyword">ON</span> <span class="token operator">*</span><span class="token punctuation">.</span><span class="token operator">*</span> <span class="token keyword">TO</span> <span class="token string">'<em class="replaceable">clone_user</em>'</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
where
<code class="literal">
<em class="replaceable">
<code>
clone_user
</code>
</em>
</code>
is the MySQL user that performs the cloning operation. The user
you select to perform the cloning operation can be any MySQL
user with the
<a class="link" href="privileges-provided.html#priv_backup-admin">
<code class="literal">
BACKUP_ADMIN
</code>
</a>
privilege on *.*.
</p>
<p>
The following example demonstrates cloning data locally:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa1510228"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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">CLONE</span> <span class="token keyword">LOCAL</span> <span class="token keyword">DATA</span> <span class="token keyword">DIRECTORY</span> <span class="token operator">=</span> <span class="token string">'<em class="replaceable">/path/to/clone_dir</em>'</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
where
<em class="replaceable">
<code>
/path/to/clone_dir
</code>
</em>
is the full
path of the local directory that data is cloned to. An absolute
path is required, and the specified directory
(
<span class="quote">
“
<span class="quote">
<em class="replaceable">
<code>
clone_dir
</code>
</em>
</span>
”
</span>
) must not
exist, but the specified path must be an existent path. The
MySQL server must have the necessary write access to create the
directory.
</p>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
A local cloning operation does not support cloning of
user-created tables or tablespaces that reside outside of the
data directory. Attempting to clone such tables or tablespaces
causes the following error:
<span class="errortext">
ERROR 1086 (HY000):
File '
<em class="replaceable">
<code>
/path/to/tablespace_name.ibd
</code>
</em>
'
already exists
</span>
. Cloning a tablespace with the same
path as the source tablespace would cause a conflict and is
therefore prohibited.
</p>
<p>
All other user-created
<code class="literal">
InnoDB
</code>
tables and
tablespaces, the
<code class="literal">
InnoDB
</code>
system tablespace,
redo logs, and undo tablespaces are cloned to the specified
directory.
</p>
</div>
<p>
If desired, you can start the MySQL server on the cloned
directory after the cloning operation is complete.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-terminal"><div class="docs-select-all right" id="sa49172545"><div class="copy-help left">Press ⌘+C to 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_safe</span> <span class="token constant">--datadir</span><span class="token attr-value"><span class="token punctuation">=</span><em class="replaceable">clone_dir</em></span></code></pre>
</div>
<p>
where
<em class="replaceable">
<code>
clone_dir
</code>
</em>
is the directory that
data was cloned to.
</p>
<p>
For information about monitoring cloning operation status and
progress, see
<a class="xref" href="clone-plugin-monitoring.html" title="7.6.7.10 Monitoring Cloning Operations">
Section 7.6.7.10, “Monitoring Cloning Operations”
</a>
.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/performance-schema-statement-histogram-summary-tables.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="performance-schema-statement-histogram-summary-tables">
</a>
29.12.20.4 Statement Histogram Summary Tables
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045068734656">
</a>
<a class="indexterm" name="idm46045068733200">
</a>
<a class="indexterm" name="idm46045068731680">
</a>
<a class="indexterm" name="idm46045068730160">
</a>
<p>
The Performance Schema maintains statement event summary
tables that contain information about minimum, maximum, and
average statement latency (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>
).
Those tables permit high-level assessment of system
performance. To permit assessment at a more fine-grained
level, the Performance Schema also collects histogram data for
statement latencies. These histograms provide additional
insight into latency distributions.
</p>
<p>
<a class="xref" href="performance-schema-statement-tables.html" title="29.12.6 Performance Schema Statement Event Tables">
Section 29.12.6, “Performance Schema Statement Event Tables”
</a>
describes the events on which statement summaries are based.
See that discussion for information about the content of
statement events, the current and historical statement event
tables, and how to control statement event collection, which
is partially disabled by default.
</p>
<p>
Example statement histogram information:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa5621459"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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_statements_histogram_by_digest
<span class="token keyword">WHERE</span> <span class="token keyword">SCHEMA_NAME</span> <span class="token operator">=</span> <span class="token string">'mydb'</span> <span class="token operator">AND</span> DIGEST <span class="token operator">=</span> <span class="token string">'bb3f69453119b2d7b3ae40673a9d4c7c'</span>
<span class="token operator">AND</span> COUNT_BUCKET <span class="token operator">></span> <span class="token number">0</span> <span class="token keyword">ORDER</span> <span class="token keyword">BY</span> BUCKET_NUMBER\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>
SCHEMA_NAME<span class="token punctuation">:</span> mydb
DIGEST<span class="token punctuation">:</span> bb3f69453119b2d7b3ae40673a9d4c7c
BUCKET_NUMBER<span class="token punctuation">:</span> 42
BUCKET_TIMER_LOW<span class="token punctuation">:</span> 66069344
BUCKET_TIMER_HIGH<span class="token punctuation">:</span> 69183097
COUNT_BUCKET<span class="token punctuation">:</span> 1
COUNT_BUCKET_AND_LOWER<span class="token punctuation">:</span> 1
BUCKET_QUANTILE<span class="token punctuation">:</span> 0.058824
<span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span 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>
SCHEMA_NAME<span class="token punctuation">:</span> mydb
DIGEST<span class="token punctuation">:</span> bb3f69453119b2d7b3ae40673a9d4c7c
BUCKET_NUMBER<span class="token punctuation">:</span> 43
BUCKET_TIMER_LOW<span class="token punctuation">:</span> 69183097
BUCKET_TIMER_HIGH<span class="token punctuation">:</span> 72443596
COUNT_BUCKET<span class="token punctuation">:</span> 1
COUNT_BUCKET_AND_LOWER<span class="token punctuation">:</span> 2
BUCKET_QUANTILE<span class="token punctuation">:</span> 0.117647
<span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span> 3. 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>
SCHEMA_NAME<span class="token punctuation">:</span> mydb
DIGEST<span class="token punctuation">:</span> bb3f69453119b2d7b3ae40673a9d4c7c
BUCKET_NUMBER<span class="token punctuation">:</span> 44
BUCKET_TIMER_LOW<span class="token punctuation">:</span> 72443596
BUCKET_TIMER_HIGH<span class="token punctuation">:</span> 75857757
COUNT_BUCKET<span class="token punctuation">:</span> 2
COUNT_BUCKET_AND_LOWER<span class="token punctuation">:</span> 4
BUCKET_QUANTILE<span class="token punctuation">:</span> 0.235294
<span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span> 4. 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>
SCHEMA_NAME<span class="token punctuation">:</span> mydb
DIGEST<span class="token punctuation">:</span> bb3f69453119b2d7b3ae40673a9d4c7c
BUCKET_NUMBER<span class="token punctuation">:</span> 45
BUCKET_TIMER_LOW<span class="token punctuation">:</span> 75857757
BUCKET_TIMER_HIGH<span class="token punctuation">:</span> 79432823
COUNT_BUCKET<span class="token punctuation">:</span> 6
COUNT_BUCKET_AND_LOWER<span class="token punctuation">:</span> 10
BUCKET_QUANTILE<span class="token punctuation">:</span> 0.625000
...</span></code></pre>
</div>
<p>
For example, in row 3, these values indicate that 23.52% of
queries run in under 75.86 microseconds:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa81485135"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql">BUCKET_TIMER_HIGH: <span class="token number">75857757</span>
BUCKET_QUANTILE: <span class="token number">0.235294</span></code></pre>
</div>
<p>
In row 4, these values indicate that 62.50% of queries run in
under 79.44 microseconds:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa99075892"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql">BUCKET_TIMER_HIGH: <span class="token number">79432823</span>
BUCKET_QUANTILE: <span class="token number">0.625000</span></code></pre>
</div>
<p>
Each statement histogram summary table has one or more
grouping columns to indicate how the table aggregates events:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<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>
has
<code class="literal">
SCHEMA_NAME
</code>
,
<code class="literal">
DIGEST
</code>
, and
<code class="literal">
BUCKET_NUMBER
</code>
columns:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
The
<code class="literal">
SCHEMA_NAME
</code>
and
<code class="literal">
DIGEST
</code>
columns identify a statement
digest row in the
<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.
</p>
</li>
<li class="listitem">
<p>
The
<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>
rows with the same
<code class="literal">
SCHEMA_NAME
</code>
and
<code class="literal">
DIGEST
</code>
values comprise the
histogram for that schema/digest combination.
</p>
</li>
<li class="listitem">
<p>
Within a given histogram, the
<code class="literal">
BUCKET_NUMBER
</code>
column indicates the
bucket number.
</p>
</li>
</ul>
</div>
</li>
<li class="listitem">
<p>
<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>
has a
<code class="literal">
BUCKET_NUMBER
</code>
column. This table
summarizes latencies globally across schema name and
digest values, using a single histogram. The
<code class="literal">
BUCKET_NUMBER
</code>
column indicates the
bucket number within this global histogram.
</p>
</li>
</ul>
</div>
<p>
A histogram consists of
<em class="replaceable">
<code>
N
</code>
</em>
buckets,
where each row represents one bucket, with the bucket number
indicated by the
<code class="literal">
BUCKET_NUMBER
</code>
column.
Bucket numbers begin with 0.
</p>
<p>
Each statement histogram summary table has these summary
columns containing aggregated values:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<code class="literal">
BUCKET_TIMER_LOW
</code>
,
<code class="literal">
BUCKET_TIMER_HIGH
</code>
</p>
<p>
A bucket counts statements that have a latency, in
picoseconds, measured between
<code class="literal">
BUCKET_TIMER_LOW
</code>
and
<code class="literal">
BUCKET_TIMER_HIGH
</code>
:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
The value of
<code class="literal">
BUCKET_TIMER_LOW
</code>
for
the first bucket (
<code class="literal">
BUCKET_NUMBER
</code>
=
0) is 0.
</p>
</li>
<li class="listitem">
<p>
The value of
<code class="literal">
BUCKET_TIMER_LOW
</code>
for a
bucket (
<code class="literal">
BUCKET_NUMBER
</code>
=
<em class="replaceable">
<code>
k
</code>
</em>
) is the same as
<code class="literal">
BUCKET_TIMER_HIGH
</code>
for the previous
bucket (
<code class="literal">
BUCKET_NUMBER
</code>
=
<em class="replaceable">
<code>
k
</code>
</em>
−1)
</p>
</li>
<li class="listitem">
<p>
The last bucket is a catchall for statements that have
a latency exceeding previous buckets in the histogram.
</p>
</li>
</ul>
</div>
</li>
<li class="listitem">
<p>
<code class="literal">
COUNT_BUCKET
</code>
</p>
<p>
The number of statements measured with a latency in the
interval from
<code class="literal">
BUCKET_TIMER_LOW
</code>
up to
but not including
<code class="literal">
BUCKET_TIMER_HIGH
</code>
.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
COUNT_BUCKET_AND_LOWER
</code>
</p>
<p>
The number of statements measured with a latency in the
interval from 0 up to but not including
<code class="literal">
BUCKET_TIMER_HIGH
</code>
.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
BUCKET_QUANTILE
</code>
</p>
<p>
The proportion of statements that fall into this or a
lower bucket. This proportion corresponds by definition to
<code class="literal">
COUNT_BUCKET_AND_LOWER /
SUM(COUNT_BUCKET)
</code>
and is displayed as a
convenience column.
</p>
</li>
</ul>
</div>
<p>
The statement histogram summary tables have these indexes:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<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>
:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
Unique index on (
<code class="literal">
SCHEMA_NAME
</code>
,
<code class="literal">
DIGEST
</code>
,
<code class="literal">
BUCKET_NUMBER
</code>
)
</p>
</li>
</ul>
</div>
</li>
<li class="listitem">
<p>
<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>
:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
Primary key on (
<code class="literal">
BUCKET_NUMBER
</code>
)
</p>
</li>
</ul>
</div>
</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
statement histogram summary tables. Truncation sets the
<code class="literal">
COUNT_BUCKET
</code>
and
<code class="literal">
COUNT_BUCKET_AND_LOWER
</code>
columns to 0.
</p>
<p>
In addition, truncating
<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>
implicitly truncates
<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>
,
and truncating
<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>
implicitly truncates
<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>
.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/mysql-shell-tutorial-javascript-documents-modify.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="mysql-shell-tutorial-javascript-documents-modify">
</a>
22.3.3.4 Modify Documents
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045127784432">
</a>
<p>
You can use the
<code class="literal">
modify()
</code>
method to update one
or more documents in a collection. The X DevAPI provides
additional methods for use with the
<code class="literal">
modify()
</code>
method to:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
Set and unset fields within documents.
</p>
</li>
<li class="listitem">
<p>
Append, insert, and delete arrays.
</p>
</li>
<li class="listitem">
<p>
Bind, limit, and sort the documents to be modified.
</p>
</li>
</ul>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h5 class="title">
<a name="idm46045127777984">
</a>
Set and Unset Document Fields
</h5>
</div>
</div>
</div>
<a class="indexterm" name="idm46045127777296">
</a>
<p>
The
<code class="literal">
modify()
</code>
method works by filtering a
collection to include only the documents to be modified and
then applying the operations that you specify to those
documents.
</p>
<p>
In the following example, the
<code class="literal">
modify()
</code>
method uses the search condition to identify the document to
change and then the
<code class="literal">
set()
</code>
method replaces
two values within the nested demographics object.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-mysqlsh"><div class="docs-select-all right" id="sa99452794"><div class="copy-help left">Press ⌘+C to 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-js></span> db<span class="token punctuation">.</span>countryinfo<span class="token punctuation">.</span><span class="token function">modify</span><span class="token punctuation">(</span><span class="token string">"Code = 'SEA'"</span><span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token keyword">set</span><span class="token punctuation">(</span>
<span class="token string">"demographics"</span><span class="token punctuation">,</span> <span class="token punctuation">{</span><span class="token string">"LifeExpectancy"</span><span class="token punctuation">:</span> <span class="token number">78</span><span class="token punctuation">,</span> <span class="token string">"Population"</span><span class="token punctuation">:</span> <span class="token number">28</span><span class="token punctuation">}</span><span class="token punctuation">)</span></code></pre>
</div>
<p>
After you modify a document, use the
<code class="literal">
find()
</code>
method to verify the change.
</p>
<p>
To remove content from a document, use the
<code class="literal">
modify()
</code>
and
<code class="literal">
unset()
</code>
methods. For example, the following query removes the GNP from
a document that matches the search condition.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-mysqlsh"><div class="docs-select-all right" id="sa88853952"><div class="copy-help left">Press ⌘+C to 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-js></span> db<span class="token punctuation">.</span>countryinfo<span class="token punctuation">.</span><span class="token function">modify</span><span class="token punctuation">(</span><span class="token string">"Name = 'Sealand'"</span><span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">unset</span><span class="token punctuation">(</span><span class="token string">"GNP"</span><span class="token punctuation">)</span></code></pre>
</div>
<p>
Use the
<code class="literal">
find()
</code>
method to verify the change.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-mysqlsh"><div class="docs-select-all right" id="sa44365245"><div class="copy-help left">Press ⌘+C to 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-js></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 = 'Sealand'"</span><span class="token punctuation">)</span>
<span class="token inlinejson"><span class="token punctuation">{</span>
<span class="token property">"_id"</span><span class="token operator">:</span> <span class="token string">"00005e2ff4af00000000000000f4"</span><span class="token punctuation">,</span>
<span class="token property">"Name"</span><span class="token operator">:</span> <span class="token string">"Sealand"</span><span class="token punctuation">,</span>
<span class="token property">"Code:"</span><span class="token operator">:</span> <span class="token string">"SEA"</span><span class="token punctuation">,</span>
<span class="token property">"IndepYear"</span><span class="token operator">:</span> <span class="token number">1967</span><span class="token punctuation">,</span>
<span class="token property">"geography"</span><span class="token operator">:</span> <span class="token punctuation">{</span>
<span class="token property">"Region"</span><span class="token operator">:</span> <span class="token string">"British Islands"</span><span class="token punctuation">,</span>
<span class="token property">"Continent"</span><span class="token operator">:</span> <span class="token string">"Europe"</span><span class="token punctuation">,</span>
<span class="token property">"SurfaceArea"</span><span class="token operator">:</span> <span class="token number">193</span>
<span class="token punctuation">}</span><span class="token punctuation">,</span>
<span class="token property">"government"</span><span class="token operator">:</span> <span class="token punctuation">{</span>
<span class="token property">"HeadOfState"</span><span class="token operator">:</span> <span class="token string">"Michael Bates"</span><span class="token punctuation">,</span>
<span class="token property">"GovernmentForm"</span><span class="token operator">:</span> <span class="token string">"Monarchy"</span>
<span class="token punctuation">}</span><span class="token punctuation">,</span>
<span class="token property">"demographics"</span><span class="token operator">:</span> <span class="token punctuation">{</span>
<span class="token property">"Population"</span><span class="token operator">:</span> <span class="token number">27</span><span class="token punctuation">,</span>
<span class="token property">"LifeExpectancy"</span><span class="token operator">:</span> <span class="token number">79</span>
<span class="token punctuation">}</span>
<span class="token punctuation">}</span></span></code></pre>
</div>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h5 class="title">
<a name="mysql-shell-tutorial-javascript-append-insert-delete">
</a>
Append, Insert, and Delete Arrays
</h5>
</div>
</div>
</div>
<a class="indexterm" name="idm46045127761264">
</a>
<p>
To append an element to an array field, or insert, or delete
elements in an array, use the
<code class="literal">
arrayAppend()
</code>
,
<code class="literal">
arrayInsert()
</code>
, or
<code class="literal">
arrayDelete()
</code>
methods. The following
examples modify the
<code class="literal">
countryinfo
</code>
collection
to enable tracking of international airports.
</p>
<p>
The first example uses the
<code class="literal">
modify()
</code>
and
<code class="literal">
set()
</code>
methods to create a new Airports
field in all documents.
</p>
<div class="caution" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Caution
</div>
<p>
Use care when you modify documents without specifying a
search condition; doing so modifies all documents in the
collection.
</p>
</div>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-mysqlsh"><div class="docs-select-all right" id="sa78636580"><div class="copy-help left">Press ⌘+C to 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-js></span> db<span class="token punctuation">.</span>countryinfo<span class="token punctuation">.</span><span class="token function">modify</span><span class="token punctuation">(</span><span class="token string">"true"</span><span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token keyword">set</span><span class="token punctuation">(</span><span class="token string">"Airports"</span><span class="token punctuation">,</span> <span class="token punctuation">[</span><span class="token punctuation">]</span><span class="token punctuation">)</span></code></pre>
</div>
<p>
With the Airports field added, the next example uses the
<code class="literal">
arrayAppend()
</code>
method to add a new airport
to one of the documents.
<span class="emphasis">
<em>
$.Airports
</em>
</span>
in
the following example represents the Airports field of the
current document.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-mysqlsh"><div class="docs-select-all right" id="sa88978832"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-mysqlsh"><span class="token prompt">mysql-js></span> db<span class="token punctuation">.</span>countryinfo<span class="token punctuation">.</span><span class="token function">modify</span><span class="token punctuation">(</span><span class="token string">"Name = 'France'"</span><span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">arrayAppend</span><span class="token punctuation">(</span><span class="token string">"$.Airports"</span><span class="token punctuation">,</span> <span class="token string">"ORY"</span><span class="token punctuation">)</span></code></pre>
</div>
<p>
Use
<code class="literal">
find()
</code>
to see the change.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-mysqlsh"><div class="docs-select-all right" id="sa2315023"><div class="copy-help left">Press ⌘+C to 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-js></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 = 'France'"</span><span class="token punctuation">)</span>
<span class="token inlinejson"><span class="token punctuation">{</span>
<span class="token property">"GNP"</span><span class="token operator">:</span> <span class="token number">1424285</span><span class="token punctuation">,</span>
<span class="token property">"_id"</span><span class="token operator">:</span> <span class="token string">"00005de917d80000000000000048"</span><span class="token punctuation">,</span>
<span class="token property">"Code"</span><span class="token operator">:</span> <span class="token string">"FRA"</span><span class="token punctuation">,</span>
<span class="token property">"Name"</span><span class="token operator">:</span> <span class="token string">"France"</span><span class="token punctuation">,</span>
<span class="token property">"Airports"</span><span class="token operator">:</span> <span class="token punctuation">[</span>
<span class="token string">"ORY"</span>
<span class="token punctuation">]</span><span class="token punctuation">,</span>
<span class="token property">"IndepYear"</span><span class="token operator">:</span> <span class="token number">843</span><span class="token punctuation">,</span>
<span class="token property">"geography"</span><span class="token operator">:</span> <span class="token punctuation">{</span>
<span class="token property">"Region"</span><span class="token operator">:</span> <span class="token string">"Western Europe"</span><span class="token punctuation">,</span>
<span class="token property">"Continent"</span><span class="token operator">:</span> <span class="token string">"Europe"</span><span class="token punctuation">,</span>
<span class="token property">"SurfaceArea"</span><span class="token operator">:</span> <span class="token number">551500</span>
<span class="token punctuation">}</span><span class="token punctuation">,</span>
<span class="token property">"government"</span><span class="token operator">:</span> <span class="token punctuation">{</span>
<span class="token property">"HeadOfState"</span><span class="token operator">:</span> <span class="token string">"Jacques Chirac"</span><span class="token punctuation">,</span>
<span class="token property">"GovernmentForm"</span><span class="token operator">:</span> <span class="token string">"Republic"</span>
<span class="token punctuation">}</span><span class="token punctuation">,</span>
<span class="token property">"demographics"</span><span class="token operator">:</span> <span class="token punctuation">{</span>
<span class="token property">"Population"</span><span class="token operator">:</span> <span class="token number">59225700</span><span class="token punctuation">,</span>
<span class="token property">"LifeExpectancy"</span><span class="token operator">:</span> <span class="token number">78.80000305175781</span>
<span class="token punctuation">}</span>
<span class="token punctuation">}</span></span></code></pre>
</div>
<p>
To insert an element at a different position in the array, use
the
<code class="literal">
arrayInsert()
</code>
method to specify which
index to insert in the path expression. In this case, the
index is 0, or the first element in the array.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-mysqlsh"><div class="docs-select-all right" id="sa47422024"><div class="copy-help left">Press ⌘+C to 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-js></span> db<span class="token punctuation">.</span>countryinfo<span class="token punctuation">.</span><span class="token function">modify</span><span class="token punctuation">(</span><span class="token string">"Name = 'France'"</span><span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">arrayInsert</span><span class="token punctuation">(</span><span class="token string">"$.Airports[0]"</span><span class="token punctuation">,</span> <span class="token string">"CDG"</span><span class="token punctuation">)</span></code></pre>
</div>
<p>
To delete an element from the array, you must pass to the
<code class="literal">
arrayDelete()
</code>
method the index of the
element to be deleted.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-mysqlsh"><div class="docs-select-all right" id="sa58454430"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-mysqlsh"><span class="token prompt">mysql-js></span> db<span class="token punctuation">.</span>countryinfo<span class="token punctuation">.</span><span class="token function">modify</span><span class="token punctuation">(</span><span class="token string">"Name = 'France'"</span><span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">arrayDelete</span><span class="token punctuation">(</span><span class="token string">"$.Airports[1]"</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="idm46045127738768">
</a>
Related Information
</h5>
</div>
</div>
</div>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
The
<a class="link" href="json.html#json-paths" title="Searching and Modifying JSON Values">
MySQL Reference
Manual
</a>
provides instructions to help you search for
and modify JSON values.
</p>
</li>
<li class="listitem">
<p>
See
<a class="ulink" href="/doc/x-devapi-userguide/en/crud-ebnf-collection-crud-functions.html#crud-ebnf-collectionmodifyfunction" target="_top">
CollectionModifyFunction
</a>
for the full syntax definition.
</p>
</li>
</ul>
</div>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/loadable-function-reference.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h2 class="title">
<a name="loadable-function-reference">
</a>
14.2 Loadable Function Reference
</h2>
</div>
</div>
</div>
<a class="indexterm" name="idm46045208367968">
</a>
<p>
The following table lists each function that is loadable at
runtime and provides a short description of each one. For a table
listing built-in functions and operators, see
<a class="xref" href="built-in-function-reference.html" title="14.1 Built-In Function and Operator Reference">
Section 14.1, “Built-In Function and Operator Reference”
</a>
</p>
<p>
For general information about loadable functions, see
<a class="xref" href="server-loadable-functions.html" title="7.7 MySQL Server Loadable Functions">
Section 7.7, “MySQL Server Loadable Functions”
</a>
.
</p>
<div class="table">
<a name="idm46045208364000">
</a>
<p class="title">
<b>
Table 14.2 Loadable Functions
</b>
</p>
<div class="table-contents">
<table frame="box" rules="all" summary="A reference that lists all loadable functions.">
<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="enterprise-encryption-functions.html#function_asymmetric-decrypt">
<code class="literal">
asymmetric_decrypt()
</code>
</a>
</th>
<td>
Decrypt ciphertext using private or public key
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
asymmetric_derive()
</code>
</th>
<td>
Derive symmetric key from asymmetric keys
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="enterprise-encryption-functions.html#function_asymmetric-encrypt">
<code class="literal">
asymmetric_encrypt()
</code>
</a>
</th>
<td>
Encrypt cleartext using private or public key
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="enterprise-encryption-functions.html#function_asymmetric-sign">
<code class="literal">
asymmetric_sign()
</code>
</a>
</th>
<td>
Generate signature from digest
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="enterprise-encryption-functions.html#function_asymmetric-verify">
<code class="literal">
asymmetric_verify()
</code>
</a>
</th>
<td>
Verify that signature matches digest
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="replication-functions-async-failover.html#function_asynchronous-connection-failover-add-managed">
<code class="literal">
asynchronous_connection_failover_add_managed()
</code>
</a>
</th>
<td>
Add a replication source server in a managed group to the source
list
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="replication-functions-async-failover.html#function_asynchronous-connection-failover-add-source">
<code class="literal">
asynchronous_connection_failover_add_source()
</code>
</a>
</th>
<td>
Add a replication source server to the source list
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="replication-functions-async-failover.html#function_asynchronous-connection-failover-delete-managed">
<code class="literal">
asynchronous_connection_failover_delete_managed()
</code>
</a>
</th>
<td>
Remove managed group of replication source servers from the source
list
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="replication-functions-async-failover.html#function_asynchronous-connection-failover-delete-source">
<code class="literal">
asynchronous_connection_failover_delete_source()
</code>
</a>
</th>
<td>
Remove a replication source server from the source list
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="audit-api-message-emit.html#function_audit-api-message-emit-udf">
<code class="literal">
audit_api_message_emit_udf()
</code>
</a>
</th>
<td>
Add message event to audit log
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="audit-log-reference.html#function_audit-log-encryption-password-get">
<code class="literal">
audit_log_encryption_password_get()
</code>
</a>
</th>
<td>
Fetch audit log encryption password
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="audit-log-reference.html#function_audit-log-encryption-password-set">
<code class="literal">
audit_log_encryption_password_set()
</code>
</a>
</th>
<td>
Set audit log encryption password
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="audit-log-reference.html#function_audit-log-filter-flush">
<code class="literal">
audit_log_filter_flush()
</code>
</a>
</th>
<td>
Flush audit log filter tables
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="audit-log-reference.html#function_audit-log-filter-remove-filter">
<code class="literal">
audit_log_filter_remove_filter()
</code>
</a>
</th>
<td>
Remove audit log filter
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="audit-log-reference.html#function_audit-log-filter-remove-user">
<code class="literal">
audit_log_filter_remove_user()
</code>
</a>
</th>
<td>
Unassign audit log filter from user
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="audit-log-reference.html#function_audit-log-filter-set-filter">
<code class="literal">
audit_log_filter_set_filter()
</code>
</a>
</th>
<td>
Define audit log filter
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="audit-log-reference.html#function_audit-log-filter-set-user">
<code class="literal">
audit_log_filter_set_user()
</code>
</a>
</th>
<td>
Assign audit log filter to user
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="audit-log-reference.html#function_audit-log-read">
<code class="literal">
audit_log_read()
</code>
</a>
</th>
<td>
Return audit log records
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="audit-log-reference.html#function_audit-log-read-bookmark">
<code class="literal">
audit_log_read_bookmark()
</code>
</a>
</th>
<td>
Bookmark for most recent audit log event
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="audit-log-reference.html#function_audit-log-rotate">
<code class="literal">
audit_log_rotate()
</code>
</a>
</th>
<td>
Rotate audit log file
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="enterprise-encryption-functions.html#function_create-asymmetric-priv-key">
<code class="literal">
create_asymmetric_priv_key()
</code>
</a>
</th>
<td>
Create private key
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="enterprise-encryption-functions.html#function_create-asymmetric-pub-key">
<code class="literal">
create_asymmetric_pub_key()
</code>
</a>
</th>
<td>
Create public key
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
create_dh_parameters()
</code>
</th>
<td>
Generate shared DH secret
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="enterprise-encryption-functions.html#function_create-digest">
<code class="literal">
create_digest()
</code>
</a>
</th>
<td>
Generate digest from string
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="firewall-reference.html#function_firewall-group-delist">
<code class="literal">
firewall_group_delist()
</code>
</a>
</th>
<td>
Remove account from firewall group profile
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="firewall-reference.html#function_firewall-group-enlist">
<code class="literal">
firewall_group_enlist()
</code>
</a>
</th>
<td>
Add account to firewall group profile
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="rewriter-query-rewrite-plugin-reference.html#function_flush-rewrite-rules">
<code class="literal">
flush_rewrite_rules()
</code>
</a>
</th>
<td>
Load rewrite_rules table into Rewriter cache
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="data-masking-plugin-functions.html#function_gen-blacklist-plugin">
<code class="literal">
gen_blacklist()
</code>
</a>
</th>
<td>
Perform dictionary term replacement
</td>
<td>
Yes
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="data-masking-component-functions.html#function_gen-blocklist">
<code class="literal">
gen_blocklist()
</code>
</a>
</th>
<td>
Perform dictionary term replacement
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="data-masking-plugin-functions.html#function_gen-blocklist-plugin">
<code class="literal">
gen_blocklist()
</code>
</a>
</th>
<td>
Perform dictionary term replacement
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="data-masking-component-functions.html#function_gen-dictionary">
<code class="literal">
gen_dictionary()
</code>
</a>
</th>
<td>
Return random term from dictionary
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="data-masking-plugin-functions.html#function_gen-dictionary-drop-plugin">
<code class="literal">
gen_dictionary_drop()
</code>
</a>
</th>
<td>
Remove dictionary from registry
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="data-masking-plugin-functions.html#function_gen-dictionary-load-plugin">
<code class="literal">
gen_dictionary_load()
</code>
</a>
</th>
<td>
Load dictionary into registry
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="data-masking-plugin-functions.html#function_gen-dictionary-plugin">
<code class="literal">
gen_dictionary()
</code>
</a>
</th>
<td>
Return random term from dictionary
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="data-masking-component-functions.html#function_gen-range">
<code class="literal">
gen_range()
</code>
</a>
</th>
<td>
Generate random number within range
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="data-masking-plugin-functions.html#function_gen-range-plugin">
<code class="literal">
gen_range()
</code>
</a>
</th>
<td>
Generate random number within range
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="data-masking-component-functions.html#function_gen-rnd-canada-sin">
<code class="literal">
gen_rnd_canada_sin()
</code>
</a>
</th>
<td>
Generate random Canada Social Insurance Number
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="data-masking-component-functions.html#function_gen-rnd-email">
<code class="literal">
gen_rnd_email()
</code>
</a>
</th>
<td>
Generate random email address
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="data-masking-plugin-functions.html#function_gen-rnd-email-plugin">
<code class="literal">
gen_rnd_email()
</code>
</a>
</th>
<td>
Generate random email address
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="data-masking-component-functions.html#function_gen-rnd-iban">
<code class="literal">
gen_rnd_iban()
</code>
</a>
</th>
<td>
Generate random International Bank Account Number
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="data-masking-component-functions.html#function_gen-rnd-pan">
<code class="literal">
gen_rnd_pan()
</code>
</a>
</th>
<td>
Generate random payment card Primary Account Number
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="data-masking-plugin-functions.html#function_gen-rnd-pan-plugin">
<code class="literal">
gen_rnd_pan()
</code>
</a>
</th>
<td>
Generate random payment card Primary Account Number
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="data-masking-component-functions.html#function_gen-rnd-ssn">
<code class="literal">
gen_rnd_ssn()
</code>
</a>
</th>
<td>
Generate random US Social Security Number
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="data-masking-plugin-functions.html#function_gen-rnd-ssn-plugin">
<code class="literal">
gen_rnd_ssn()
</code>
</a>
</th>
<td>
Generate random US Social Security Number
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="data-masking-component-functions.html#function_gen-rnd-uk-nin">
<code class="literal">
gen_rnd_uk_nin()
</code>
</a>
</th>
<td>
Generate random United Kingdom National Insurance Number
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="data-masking-component-functions.html#function_gen-rnd-us-phone">
<code class="literal">
gen_rnd_us_phone()
</code>
</a>
</th>
<td>
Generate random US phone number
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="data-masking-plugin-functions.html#function_gen-rnd-us-phone-plugin">
<code class="literal">
gen_rnd_us_phone()
</code>
</a>
</th>
<td>
Generate random US phone number
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="data-masking-component-functions.html#function_gen-rnd-uuid">
<code class="literal">
gen_rnd_uuid()
</code>
</a>
</th>
<td>
Generate random Universally Unique Identifier
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="group-replication-functions-for-member-actions.html#function_group-replication-disable-member-action">
<code class="literal">
group_replication_disable_member_action()
</code>
</a>
</th>
<td>
Enable a member action so that the member does not take it in the
specified situation
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="group-replication-functions-for-member-actions.html#function_group-replication-enable-member-action">
<code class="literal">
group_replication_enable_member_action()
</code>
</a>
</th>
<td>
Enable a member action for the member to take in the specified
situation
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="group-replication-functions-for-communication-protocol.html#function_group-replication-get-communication-protocol">
<code class="literal">
group_replication_get_communication_protocol()
</code>
</a>
</th>
<td>
Return Group Replication protocol version
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<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>
</th>
<td>
Return maximum number of consensus instances executable in
parallel
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="group-replication-functions-for-member-actions.html#function_group-replication-reset-member-actions">
<code class="literal">
group_replication_reset_member_actions()
</code>
</a>
</th>
<td>
Reset the member actions configuration to the default settings
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<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>
</th>
<td>
Assign group member as new primary
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="group-replication-functions-for-communication-protocol.html#function_group-replication-set-communication-protocol">
<code class="literal">
group_replication_set_communication_protocol()
</code>
</a>
</th>
<td>
Set Group Replication protocol version
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<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>
</th>
<td>
Set maximum number of consensus instances executable in parallel
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="group-replication-functions-for-mode.html#function_group-replication-switch-to-multi-primary-mode">
<code class="literal">
group_replication_switch_to_multi_primary_mode()
</code>
</a>
</th>
<td>
Change group from single-primary to multi-primary mode
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="group-replication-functions-for-mode.html#function_group-replication-switch-to-single-primary-mode">
<code class="literal">
group_replication_switch_to_single_primary_mode()
</code>
</a>
</th>
<td>
Change group from multi-primary to single-primary mode
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="keyring-functions-plugin-specific.html#function_keyring-aws-rotate-cmk">
<code class="literal">
keyring_aws_rotate_cmk()
</code>
</a>
</th>
<td>
Rotate AWS customer master key
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="keyring-functions-plugin-specific.html#function_keyring-aws-rotate-keys">
<code class="literal">
keyring_aws_rotate_keys()
</code>
</a>
</th>
<td>
Rotate keys in keyring_aws storage file
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="keyring-functions-plugin-specific.html#function_keyring-hashicorp-update-config">
<code class="literal">
keyring_hashicorp_update_config()
</code>
</a>
</th>
<td>
Cause runtime keyring_hashicorp reconfiguration
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="keyring-functions-general-purpose.html#function_keyring-key-fetch">
<code class="literal">
keyring_key_fetch()
</code>
</a>
</th>
<td>
Fetch keyring key value
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="keyring-functions-general-purpose.html#function_keyring-key-generate">
<code class="literal">
keyring_key_generate()
</code>
</a>
</th>
<td>
Generate random keyring key
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="keyring-functions-general-purpose.html#function_keyring-key-length-fetch">
<code class="literal">
keyring_key_length_fetch()
</code>
</a>
</th>
<td>
Return keyring key length
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="keyring-functions-general-purpose.html#function_keyring-key-remove">
<code class="literal">
keyring_key_remove()
</code>
</a>
</th>
<td>
Remove keyring key
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="keyring-functions-general-purpose.html#function_keyring-key-store">
<code class="literal">
keyring_key_store()
</code>
</a>
</th>
<td>
Store key in keyring
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="keyring-functions-general-purpose.html#function_keyring-key-type-fetch">
<code class="literal">
keyring_key_type_fetch()
</code>
</a>
</th>
<td>
Return keyring key type
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="rewriter-query-rewrite-plugin-reference.html#function_load-rewrite-rules">
<code class="literal">
load_rewrite_rules()
</code>
</a>
</th>
<td>
Rewriter plugin helper routine
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="data-masking-component-functions.html#function_mask-canada-sin">
<code class="literal">
mask_canada_sin()
</code>
</a>
</th>
<td>
Mask Canada Social Insurance Number
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="data-masking-component-functions.html#function_mask-iban">
<code class="literal">
mask_iban()
</code>
</a>
</th>
<td>
Mask International Bank Account Number
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="data-masking-component-functions.html#function_mask-inner">
<code class="literal">
mask_inner()
</code>
</a>
</th>
<td>
Mask interior part of string
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="data-masking-plugin-functions.html#function_mask-inner-plugin">
<code class="literal">
mask_inner()
</code>
</a>
</th>
<td>
Mask interior part of string
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="data-masking-component-functions.html#function_mask-outer">
<code class="literal">
mask_outer()
</code>
</a>
</th>
<td>
Mask left and right parts of string
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="data-masking-plugin-functions.html#function_mask-outer-plugin">
<code class="literal">
mask_outer()
</code>
</a>
</th>
<td>
Mask left and right parts of string
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="data-masking-component-functions.html#function_mask-pan">
<code class="literal">
mask_pan()
</code>
</a>
</th>
<td>
Mask payment card Primary Account Number part of string
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="data-masking-plugin-functions.html#function_mask-pan-plugin">
<code class="literal">
mask_pan()
</code>
</a>
</th>
<td>
Mask payment card Primary Account Number part of string
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="data-masking-component-functions.html#function_mask-pan-relaxed">
<code class="literal">
mask_pan_relaxed()
</code>
</a>
</th>
<td>
Mask payment card Primary Account Number part of string
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="data-masking-plugin-functions.html#function_mask-pan-relaxed-plugin">
<code class="literal">
mask_pan_relaxed()
</code>
</a>
</th>
<td>
Mask payment card Primary Account Number part of string
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="data-masking-component-functions.html#function_mask-ssn">
<code class="literal">
mask_ssn()
</code>
</a>
</th>
<td>
Mask US Social Security Number
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="data-masking-plugin-functions.html#function_mask-ssn-plugin">
<code class="literal">
mask_ssn()
</code>
</a>
</th>
<td>
Mask US Social Security Number
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="data-masking-component-functions.html#function_mask-uk-nin">
<code class="literal">
mask_uk_nin()
</code>
</a>
</th>
<td>
Mask United Kingdom National Insurance Number
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="data-masking-component-functions.html#function_mask-uuid">
<code class="literal">
mask_uuid()
</code>
</a>
</th>
<td>
Mask Universally Unique Identifier part of string
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="data-masking-component-functions.html#function_masking-dictionaries-flush">
<code class="literal">
masking_dictionaries_flush()
</code>
</a>
</th>
<td>
Cause masking_dictionaries cache to be reloaded from table
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="data-masking-component-functions.html#function_masking-dictionary-remove">
<code class="literal">
masking_dictionary_remove()
</code>
</a>
</th>
<td>
Remove dictionary from the database table
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="data-masking-component-functions.html#function_masking-dictionary-term-add">
<code class="literal">
masking_dictionary_term_add()
</code>
</a>
</th>
<td>
Add new term to the dictionary
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="data-masking-component-functions.html#function_masking-dictionary-term-remove">
<code class="literal">
masking_dictionary_term_remove()
</code>
</a>
</th>
<td>
Remove existing term from the dictionary
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="firewall-reference.html#function_mysql-firewall-flush-status">
<code class="literal">
mysql_firewall_flush_status()
</code>
</a>
</th>
<td>
Reset firewall status variables
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="query-attributes.html#function_mysql-query-attribute-string">
<code class="literal">
mysql_query_attribute_string()
</code>
</a>
</th>
<td>
Fetch query attribute value
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="firewall-reference.html#function_normalize-statement">
<code class="literal">
normalize_statement()
</code>
</a>
</th>
<td>
Normalize SQL statement to digest form
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="firewall-reference.html#function_read-firewall-group-allowlist">
<code class="literal">
read_firewall_group_allowlist()
</code>
</a>
</th>
<td>
Update firewall group profile recorded-statement cache
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="firewall-reference.html#function_read-firewall-groups">
<code class="literal">
read_firewall_groups()
</code>
</a>
</th>
<td>
Update firewall group profile cache
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="firewall-reference.html#function_read-firewall-users">
<code class="literal">
read_firewall_users()
</code>
</a>
</th>
<td>
Update firewall account profile cache
</td>
<td>
Yes
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="firewall-reference.html#function_read-firewall-whitelist">
<code class="literal">
read_firewall_whitelist()
</code>
</a>
</th>
<td>
Update firewall account profile recorded-statement cache
</td>
<td>
Yes
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="locking-service.html#function_service-get-read-locks">
<code class="literal">
service_get_read_locks()
</code>
</a>
</th>
<td>
Acquire locking service shared locks
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="locking-service.html#function_service-get-write-locks">
<code class="literal">
service_get_write_locks()
</code>
</a>
</th>
<td>
Acquire locking service exclusive locks
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="locking-service.html#function_service-release-locks">
<code class="literal">
service_release_locks()
</code>
</a>
</th>
<td>
Release locking service locks
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="firewall-reference.html#function_set-firewall-group-mode">
<code class="literal">
set_firewall_group_mode()
</code>
</a>
</th>
<td>
Establish firewall group profile operational mode
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="firewall-reference.html#function_set-firewall-mode">
<code class="literal">
set_firewall_mode()
</code>
</a>
</th>
<td>
Establish firewall account profile operational mode
</td>
<td>
Yes
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="version-tokens-reference.html#function_version-tokens-delete">
<code class="literal">
version_tokens_delete()
</code>
</a>
</th>
<td>
Delete tokens from version tokens list
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="version-tokens-reference.html#function_version-tokens-edit">
<code class="literal">
version_tokens_edit()
</code>
</a>
</th>
<td>
Modify version tokens list
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="version-tokens-reference.html#function_version-tokens-lock-exclusive">
<code class="literal">
version_tokens_lock_exclusive()
</code>
</a>
</th>
<td>
Acquire exclusive locks on version tokens
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="version-tokens-reference.html#function_version-tokens-lock-shared">
<code class="literal">
version_tokens_lock_shared()
</code>
</a>
</th>
<td>
Acquire shared locks on version tokens
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="version-tokens-reference.html#function_version-tokens-set">
<code class="literal">
version_tokens_set()
</code>
</a>
</th>
<td>
Set version tokens list
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="version-tokens-reference.html#function_version-tokens-show">
<code class="literal">
version_tokens_show()
</code>
</a>
</th>
<td>
Return version tokens list
</td>
<td>
</td>
</tr>
<tr>
<th scope="row">
<a class="link" href="version-tokens-reference.html#function_version-tokens-unlock">
<code class="literal">
version_tokens_unlock()
</code>
</a>
</th>
<td>
Release version tokens locks
</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: 405.156px;">
Name
</th>
<th style="width: 243.688px;">
Description
</th>
<th style="width: 89.1562px;">
Deprecated
</th>
</tr>
</thead>
</table>
</div>
</div>
<br class="table-break"/>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/performance-schema-events-transactions-history-table.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="performance-schema-events-transactions-history-table">
</a>
29.12.7.2 The events_transactions_history Table
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045072233744">
</a>
<a class="indexterm" name="idm46045072232240">
</a>
<p>
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 contains the
<em class="replaceable">
<code>
N
</code>
</em>
most recent
transaction events that have ended per thread. Transaction
events are not added to the table until they have ended. When
the table contains the maximum number of rows for a given
thread, the oldest thread row is discarded when a new row for
that thread is added. When a thread ends, all its rows are
discarded.
</p>
<p>
The Performance Schema autosizes the value of
<em class="replaceable">
<code>
N
</code>
</em>
during server startup. To set the
number of rows per thread explicitly, set the
<a class="link" href="performance-schema-system-variables.html#sysvar_performance_schema_events_transactions_history_size">
<code class="literal">
performance_schema_events_transactions_history_size
</code>
</a>
system variable at server startup.
</p>
<p>
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 has the same columns and indexing as
<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>
. See
<a class="xref" href="performance-schema-events-transactions-current-table.html" title="29.12.7.1 The events_transactions_current Table">
Section 29.12.7.1, “The events_transactions_current Table”
</a>
.
</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-transactions-history-table.html" title="29.12.7.2 The events_transactions_history Table">
<code class="literal">
events_transactions_history
</code>
</a>
table. It removes the rows.
</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>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/innodb-and-mysql-replication.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h2 class="title">
<a name="innodb-and-mysql-replication">
</a>
17.19 InnoDB and MySQL Replication
</h2>
</div>
</div>
</div>
<a class="indexterm" name="idm46045149111920">
</a>
<p>
It is possible to use replication in a way where the storage engine
on the replica is not the same as the storage engine on the source.
For example, you can replicate modifications to an
<code class="literal">
InnoDB
</code>
table on the source to a
<code class="literal">
MyISAM
</code>
table on the replica. For more information
see,
<a class="xref" href="replication-solutions-diffengines.html" title="19.4.4 Using Replication with Different Source and Replica Storage Engines">
Section 19.4.4, “Using Replication with Different Source and Replica Storage Engines”
</a>
.
</p>
<p>
For information about setting up a replica, see
<a class="xref" href="replication-setup-replicas.html" title="19.1.2.6 Setting Up Replicas">
Section 19.1.2.6, “Setting Up Replicas”
</a>
, and
<a class="xref" href="replication-snapshot-method.html" title="19.1.2.5 Choosing a Method for Data Snapshots">
Section 19.1.2.5, “Choosing a Method for Data Snapshots”
</a>
. To make a new replica
without taking down the source or an existing replica, use the
<a class="link" href="mysql-enterprise-backup.html" title="32.1 MySQL Enterprise Backup Overview">
MySQL Enterprise Backup
</a>
product.
</p>
<p>
Transactions that fail on the source do not affect replication.
MySQL replication is based on the binary log where MySQL writes SQL
statements that modify data. A transaction that fails (for example,
because of a foreign key violation, or because it is rolled back) is
not written to the binary log, so it is not sent to replicas. See
<a class="xref" href="commit.html" title="15.3.1 START TRANSACTION, COMMIT, and ROLLBACK Statements">
Section 15.3.1, “START TRANSACTION, COMMIT, and ROLLBACK Statements”
</a>
.
</p>
<p>
<b>
Replication and CASCADE.
</b>
Cascading actions for
<code class="literal">
InnoDB
</code>
tables on the
source are executed on the replica
<span class="emphasis">
<em>
only
</em>
</span>
if
the tables sharing the foreign key relation use
<code class="literal">
InnoDB
</code>
on both the source and replica. This is
true whether you are using statement-based or row-based
replication. Suppose that you have started replication, and then
create two tables on the source, where
<code class="literal">
InnoDB
</code>
is defined as the default storage engine, using the following
<a class="link" href="create-table.html" title="15.1.20 CREATE TABLE Statement">
<code class="literal">
CREATE TABLE
</code>
</a>
statements:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa96885351"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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> fc1 <span class="token punctuation">(</span>
i <span class="token datatype">INT</span> <span class="token keyword">PRIMARY</span> <span class="token keyword">KEY</span><span class="token punctuation">,</span>
j <span class="token datatype">INT</span>
<span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token keyword">CREATE</span> <span class="token keyword">TABLE</span> fc2 <span class="token punctuation">(</span>
m <span class="token datatype">INT</span> <span class="token keyword">PRIMARY</span> <span class="token keyword">KEY</span><span class="token punctuation">,</span>
n <span class="token datatype">INT</span><span class="token punctuation">,</span>
<span class="token keyword">FOREIGN</span> <span class="token keyword">KEY</span> ni <span class="token punctuation">(</span>n<span class="token punctuation">)</span> <span class="token keyword">REFERENCES</span> fc1 <span class="token punctuation">(</span>i<span class="token punctuation">)</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 punctuation">;</span></code></pre>
</div>
<p>
If the replica has
<code class="literal">
MyISAM
</code>
defined as the default
storage engine, the same tables are created on the replica, but they
use the
<code class="literal">
MyISAM
</code>
storage engine, and the
<code class="literal">
FOREIGN KEY
</code>
option is ignored. Now we insert some
rows into the tables on the source:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa75177364"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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">source></span> <span class="token keyword">INSERT</span> <span class="token keyword">INTO</span> fc1 <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 number">1</span><span class="token punctuation">)</span><span class="token punctuation">,</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">Query OK, 2 rows affected (0.09 sec)</span>
<span class="token output">Records: 2 Duplicates: 0 Warnings: 0</span>
<span class="token prompt">source></span> <span class="token keyword">INSERT</span> <span class="token keyword">INTO</span> fc2 <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 number">1</span><span class="token punctuation">)</span><span class="token punctuation">,</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 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>
<span class="token output">Query OK, 3 rows affected (0.19 sec)</span>
<span class="token output">Records: 3 Duplicates: 0 Warnings: 0</span></code></pre>
</div>
<p>
At this point, on both the source and the replica, table
<code class="literal">
fc1
</code>
contains 2 rows, and table
<code class="literal">
fc2
</code>
contains 3 rows, as shown here:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa81892216"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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">source></span> <span class="token keyword">SELECT</span> <span class="token operator">*</span> <span class="token keyword">FROM</span> fc1<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>
<span class="token output"><span class="token punctuation">|</span> i <span class="token punctuation">|</span> j <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>
<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> 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>
<span class="token output">2 rows in set (0.00 sec)</span>
<span class="token prompt">source></span> <span class="token keyword">SELECT</span> <span class="token operator">*</span> <span class="token keyword">FROM</span> fc2<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>
<span class="token output"><span class="token punctuation">|</span> m <span class="token punctuation">|</span> n <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>
<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> 2 <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>
<span class="token output">3 rows in set (0.00 sec)</span>
<span class="token prompt">replica></span> <span class="token keyword">SELECT</span> <span class="token operator">*</span> <span class="token keyword">FROM</span> fc1<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>
<span class="token output"><span class="token punctuation">|</span> i <span class="token punctuation">|</span> j <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>
<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> 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>
<span class="token output">2 rows in set (0.00 sec)</span>
<span class="token prompt">replica></span> <span class="token keyword">SELECT</span> <span class="token operator">*</span> <span class="token keyword">FROM</span> fc2<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>
<span class="token output"><span class="token punctuation">|</span> m <span class="token punctuation">|</span> n <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>
<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> 2 <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>
<span class="token output">3 rows in set (0.00 sec)</span></code></pre>
</div>
<p>
Now suppose that you perform the following
<a class="link" href="delete.html" title="15.2.2 DELETE Statement">
<code class="literal">
DELETE
</code>
</a>
statement on the source:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa11977555"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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">source></span> <span class="token keyword">DELETE</span> <span class="token keyword">FROM</span> fc1 <span class="token keyword">WHERE</span> i<span class="token operator">=</span><span class="token number">1</span><span class="token punctuation">;</span>
<span class="token output">Query OK, 1 row affected (0.09 sec)</span></code></pre>
</div>
<p>
Due to the cascade, table
<code class="literal">
fc2
</code>
on the source now
contains only 1 row:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa99018064"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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">source></span> <span class="token keyword">SELECT</span> <span class="token operator">*</span> <span class="token keyword">FROM</span> fc2<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>
<span class="token output"><span class="token punctuation">|</span> m <span class="token punctuation">|</span> n <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>
<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><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><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>
However, the cascade does not propagate on the replica because on
the replica the
<a class="link" href="delete.html" title="15.2.2 DELETE Statement">
<code class="literal">
DELETE
</code>
</a>
for
<code class="literal">
fc1
</code>
deletes no rows from
<code class="literal">
fc2
</code>
.
The replica's copy of
<code class="literal">
fc2
</code>
still contains all of
the rows that were originally inserted:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa64956061"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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">replica></span> <span class="token keyword">SELECT</span> <span class="token operator">*</span> <span class="token keyword">FROM</span> fc2<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>
<span class="token output"><span class="token punctuation">|</span> m <span class="token punctuation">|</span> n <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>
<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> 3 <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> 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>
<span class="token output">3 rows in set (0.00 sec)</span></code></pre>
</div>
<p>
This difference is due to the fact that the cascading deletes are
handled internally by the
<code class="literal">
InnoDB
</code>
storage engine,
which means that none of the changes are logged.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/mysql-cluster-ndbinfo-dict-obj-types.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="mysql-cluster-ndbinfo-dict-obj-types">
</a>
25.6.17.27 The ndbinfo dict_obj_types Table
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045089536560">
</a>
<p>
The
<code class="literal">
dict_obj_types
</code>
table is a static table
listing possible dictionary object types used in the NDB kernel.
These are the same types defined by
<a class="ulink" href="/doc/ndbapi/en/ndb-object.html#ndb-object-type" target="_top">
<code class="literal">
Object::Type
</code>
</a>
in the NDB API.
</p>
<p>
The
<code class="literal">
dict_obj_types
</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">
type_id
</code>
</p>
<p>
The type ID for this type
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
type_name
</code>
</p>
<p>
The name of this type
</p>
</li>
</ul>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/upgrade-troubleshooting.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h2 class="title">
<a name="upgrade-troubleshooting">
</a>
3.13 Upgrade Troubleshooting
</h2>
</div>
</div>
</div>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
A schema mismatch in a MySQL 8.3 instance
between the
<code class="filename">
.frm
</code>
file of a table and the
<code class="literal">
InnoDB
</code>
data dictionary can cause an upgrade
to MySQL 8.4 to fail. Such mismatches may be due
to
<code class="filename">
.frm
</code>
file corruption. To address this
issue, dump and restore affected tables before attempting the
upgrade again.
</p>
</li>
<li class="listitem">
<p>
If problems occur, such as that the new
<a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
<span class="command">
<strong>
mysqld
</strong>
</span>
</a>
server does not start, verify that
you do not have an old
<code class="filename">
my.cnf
</code>
file from
your previous installation. You can check this with the
<a class="link" href="option-file-options.html#option_general_print-defaults">
<code class="option">
--print-defaults
</code>
</a>
option (for
example,
<a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
<span class="command">
<strong>
mysqld --print-defaults
</strong>
</span>
</a>
). If this
command displays anything other than the program name, you
have an active
<code class="filename">
my.cnf
</code>
file that affects
server or client operation.
</p>
</li>
<li class="listitem">
<p>
If, after an upgrade, you experience problems with compiled
client programs, such as
<code class="literal">
Commands out of
sync
</code>
or unexpected core dumps, you probably have
used old header or library files when compiling your programs.
In this case, check the date for your
<code class="filename">
mysql.h
</code>
file and
<code class="filename">
libmysqlclient.a
</code>
library to verify that
they are from the new MySQL distribution. If not, recompile
your programs with the new headers and libraries.
Recompilation might also be necessary for programs compiled
against the shared client library if the library major version
number has changed (for example, from
<code class="filename">
libmysqlclient.so.20
</code>
to
<code class="filename">
libmysqlclient.so.21
</code>
).
</p>
</li>
<li class="listitem">
<p>
If you have created a loadable function with a given name and
upgrade MySQL to a version that implements a new built-in
function with the same name, the loadable function becomes
inaccessible. To correct this, use
<a class="link" href="drop-function.html" title="15.1.26 DROP FUNCTION Statement">
<code class="literal">
DROP
FUNCTION
</code>
</a>
to drop the loadable function, and then use
<a class="link" href="create-function.html" title="15.1.14 CREATE FUNCTION Statement">
<code class="literal">
CREATE FUNCTION
</code>
</a>
to re-create
the loadable function with a different nonconflicting name.
The same is true if the new version of MySQL implements a
built-in function with the same name as an existing stored
function. See
<a class="xref" href="function-resolution.html" title="11.2.5 Function Name Parsing and Resolution">
Section 11.2.5, “Function Name Parsing and Resolution”
</a>
, for the
rules describing how the server interprets references to
different kinds of functions.
</p>
</li>
<li class="listitem">
<p>
If upgrade to MySQL 8.4 fails due to any of the
issues outlined 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>
,
the server reverts all changes to the data directory. In this
case, remove all redo log files and restart the MySQL
8.3 server on the existing data directory to
address the errors. The redo log files
(
<code class="filename">
ib_logfile*
</code>
) reside in the MySQL data
directory by default. After the errors are fixed, perform a
slow shutdown (by setting
<a class="link" href="innodb-parameters.html#sysvar_innodb_fast_shutdown">
<code class="literal">
innodb_fast_shutdown=0
</code>
</a>
)
before attempting the upgrade again.
</p>
</li>
</ul>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/apache.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h2 class="title">
<a name="apache">
</a>
5.7 Using MySQL with Apache
</h2>
</div>
</div>
</div>
<a class="indexterm" name="idm46045324499680">
</a>
<p>
There are programs that let you authenticate your users from a
MySQL database and also let you write your log files into a MySQL
table.
</p>
<p>
You can change the Apache logging format to be easily readable by
MySQL by putting the following into the Apache configuration file:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-none"><div class="docs-select-all right" id="sa57392319"><div class="copy-help left">Press ⌘+C to 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">LogFormat \
"\"%h\",%{%Y%m%d%H%M%S}t,%>s,\"%b\",\"%{Content-Type}o\", \
\"%U\",\"%{Referer}i\",\"%{User-Agent}i\""</code></pre>
</div>
<p>
To load a log file in that format into MySQL, you can use a
statement something like this:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa64379494"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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">LOAD</span> <span class="token keyword">DATA</span> <span class="token keyword">INFILE</span> <span class="token string">'<em class="replaceable">/local/access_log</em>'</span> <span class="token keyword">INTO</span> <span class="token keyword">TABLE</span> <em class="replaceable">tbl_name</em>
<span class="token keyword">FIELDS</span> <span class="token keyword">TERMINATED</span> <span class="token keyword">BY</span> <span class="token string">','</span> <span class="token keyword">OPTIONALLY</span> <span class="token keyword">ENCLOSED</span> <span class="token keyword">BY</span> <span class="token string">'"'</span> <span class="token keyword">ESCAPED</span> <span class="token keyword">BY</span> <span class="token string">'\\'</span></code></pre>
</div>
<p>
The named table should be created to have columns that correspond
to those that the
<code class="literal">
LogFormat
</code>
line writes to the
log file.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/scalar-subqueries.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="scalar-subqueries">
</a>
15.2.15.1 The Subquery as Scalar Operand
</h4>
</div>
</div>
</div>
<p>
In its simplest form, a subquery is a scalar subquery that
returns a single value. A scalar subquery is a simple operand,
and you can use it almost anywhere a single column value or
literal is legal, and you can expect it to have those
characteristics that all operands have: a data type, a length,
an indication that it can be
<code class="literal">
NULL
</code>
, and so on.
For example:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa89622869"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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>s1 <span class="token datatype">INT</span><span class="token punctuation">,</span> s2 <span class="token datatype">CHAR</span><span class="token punctuation">(</span><span class="token number">5</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 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">100</span><span class="token punctuation">,</span> <span class="token string">'abcde'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token keyword">SELECT</span> <span class="token punctuation">(</span><span class="token keyword">SELECT</span> s2 <span class="token keyword">FROM</span> t1<span class="token punctuation">)</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
The subquery in this
<a class="link" href="select.html" title="15.2.13 SELECT Statement">
<code class="literal">
SELECT
</code>
</a>
returns a single value (
<code class="literal">
'abcde'
</code>
) that has a
data type of
<a class="link" href="char.html" title="13.3.2 The CHAR and VARCHAR Types">
<code class="literal">
CHAR
</code>
</a>
, a length of 5,
a character set and collation equal to the defaults in effect at
<a class="link" href="create-table.html" title="15.1.20 CREATE TABLE Statement">
<code class="literal">
CREATE TABLE
</code>
</a>
time, and an
indication that the value in the column can be
<code class="literal">
NULL
</code>
. Nullability of the value selected by a
scalar subquery is not copied because if the subquery result is
empty, the result is
<code class="literal">
NULL
</code>
. For the subquery
just shown, if
<code class="literal">
t1
</code>
were empty, the result
would be
<code class="literal">
NULL
</code>
even though
<code class="literal">
s2
</code>
is
<code class="literal">
NOT NULL
</code>
.
</p>
<p>
There are a few contexts in which a scalar subquery cannot be
used. If a statement permits only a literal value, you cannot
use a subquery. For example,
<code class="literal">
LIMIT
</code>
requires
literal integer arguments, and
<a class="link" href="load-data.html" title="15.2.9 LOAD DATA Statement">
<code class="literal">
LOAD
DATA
</code>
</a>
requires a literal string file name. You cannot
use subqueries to supply these values.
</p>
<p>
When you see examples in the following sections that contain the
rather spartan construct
<code class="literal">
(SELECT column1 FROM
t1)
</code>
, imagine that your own code contains much more
diverse and complex constructions.
</p>
<p>
Suppose that we make two tables:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa55521098"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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>s1 <span class="token datatype">INT</span><span class="token punctuation">)</span><span class="token punctuation">;</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 punctuation">;</span>
<span class="token keyword">CREATE</span> <span class="token keyword">TABLE</span> t2 <span class="token punctuation">(</span>s1 <span class="token datatype">INT</span><span class="token punctuation">)</span><span class="token punctuation">;</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 punctuation">;</span></code></pre>
</div>
<p>
Then perform a
<a class="link" href="select.html" title="15.2.13 SELECT Statement">
<code class="literal">
SELECT
</code>
</a>
:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa84855267"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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> s1 <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>
The result is
<code class="literal">
2
</code>
because there is a row in
<code class="literal">
t2
</code>
containing a column
<code class="literal">
s1
</code>
that has a value of
<code class="literal">
2
</code>
.
</p>
<p>
The preceding query can also be written like this, using
<a class="link" href="table.html" title="15.2.16 TABLE Statement">
<code class="literal">
TABLE
</code>
</a>
:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa51364742"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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">TABLE</span> t2<span class="token punctuation">)</span> <span class="token keyword">FROM</span> t1<span class="token punctuation">;</span></code></pre>
</div>
<p>
A scalar subquery can be part of an expression, but remember the
parentheses, even if the subquery is an operand that provides an
argument for a function. For example:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa89749608"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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">UPPER</span><span class="token punctuation">(</span><span class="token punctuation">(</span><span class="token keyword">SELECT</span> s1 <span class="token keyword">FROM</span> t1<span class="token punctuation">)</span><span class="token punctuation">)</span> <span class="token keyword">FROM</span> t2<span class="token punctuation">;</span></code></pre>
</div>
<p>
The same result can be obtained using
<code class="literal">
SELECT
UPPER((TABLE t1)) FROM t2
</code>
.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/data-masking-plugin.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="data-masking-plugin">
</a>
8.5.3 MySQL Enterprise Data Masking and De-Identification Plugin
</h3>
</div>
</div>
</div>
<div class="toc">
<dl class="toc">
<dt>
<span class="section">
<a href="data-masking-plugin-installation.html">
8.5.3.1 MySQL Enterprise Data Masking and De-Identification Plugin Installation
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="data-masking-plugin-usage.html">
8.5.3.2 Using the MySQL Enterprise Data Masking and De-Identification Plugin
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="data-masking-plugin-function-reference.html">
8.5.3.3 MySQL Enterprise Data Masking and De-Identification Plugin Function Reference
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="data-masking-plugin-functions.html">
8.5.3.4 MySQL Enterprise Data Masking and De-Identification Plugin Function Descriptions
</a>
</span>
</dt>
</dl>
</div>
<p>
MySQL Enterprise Data Masking and De-Identification is based on a plugin library that implements these
elements:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
A server-side plugin named
<code class="literal">
data_masking
</code>
.
</p>
</li>
<li class="listitem">
<p>
A set of loadable functions provides an SQL-level API for
performing masking and de-identification operations. Some of
these functions require the
<a class="link" href="privileges-provided.html#priv_super">
<code class="literal">
SUPER
</code>
</a>
privilege.
</p>
</li>
</ul>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/group-replication-change-primary.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="group-replication-change-primary">
</a>
20.5.1.1 Changing the Primary
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045133606832">
</a>
<a class="indexterm" name="idm46045133605344">
</a>
<a class="indexterm" name="idm46045133604240">
</a>
<a class="indexterm" name="idm46045133602752">
</a>
<p>
This section explains how to change which member of a
single-primary group is the primary, using the
<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>
function, which can be can be run on any member of the group.
When this is done, the current primary becomes a read-only
secondary, and the specified group member becomes the read/write
primary; this replaces the usual primary election process (see
<a class="xref" href="group-replication-single-primary-mode.html" title="20.1.3.1 Single-Primary Mode">
Section 20.1.3.1, “Single-Primary Mode”
</a>
).
</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>
If all members are not running the same MySQL Server version,
you can specify a new primary member that is running the lowest
MySQL Server version in the group only. This safeguard is
applied to ensure the group maintains compatibility with new
functions.
</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 from 0 seconds
(immediately) up to 3600 seconds (60 minutes) for transactions
that are running when you use the function. 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>
<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>
<p>
Pass in the
<a class="link" href="replication-options.html#sysvar_server_uuid">
<code class="literal">
server_uuid
</code>
</a>
of the
member which you want to become the new primary of the group by
issuing the following statement:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa97614673"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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><em class="replaceable">member_uuid</em><span class="token punctuation">)</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
You can add a timeout as shown here:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa470391"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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></code></pre>
</div>
<p>
To check the status of the timeout, use the
<code class="literal">
PROCESSLIST_INFO
</code>
column in the Performance
Schema
<a class="link" href="performance-schema-threads-table.html" title="29.12.22.8 The threads Table">
<code class="literal">
threads
</code>
</a>
table, like this:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa99791230"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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> PROCESSLIST_INFO <span class="token keyword">FROM</span> performance_schema<span class="token punctuation">.</span>threads
<span class="token prompt"> -></span> <span class="token keyword">WHERE</span> <span class="token keyword">NAME</span><span class="token operator">=</span><span class="token string">"thread/group_rpl/THD_transaction_monitor"</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>
NAME<span class="token punctuation">:</span> thread/group_rpl/THD_transaction_monitor
PROCESSLIST_INFO<span class="token punctuation">:</span> Group replication transaction monitor<span class="token punctuation">:</span> Stopped client connections</span></code></pre>
</div>
<p>
The status shows when the transaction monitoring thread has been
created, when new transactions have been stopped, when the
client connections with uncommitted transactions have been
disconnected, and finally, when the process is complete and new
transactions are allowed again.
</p>
<p>
While the action runs, you can check its progress by issuing the
statement shown here:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa73960582"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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> event_name<span class="token punctuation">,</span> work_completed<span class="token punctuation">,</span> work_estimated
<span class="token prompt"> -></span> <span class="token keyword">FROM</span> performance_schema<span class="token punctuation">.</span>events_stages_current
<span class="token prompt"> -></span> <span class="token keyword">WHERE</span> event_name <span class="token operator">LIKE</span> <span class="token string">"%stage/group_rpl%"</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>
EVENT_NAME<span class="token punctuation">:</span> stage/group_rpl/Primary Election<span class="token punctuation">:</span> Waiting for members to turn on super_read_only
WORK_COMPLETED<span class="token punctuation">:</span> 3
WORK_ESTIMATED<span class="token punctuation">:</span> 5</span></code></pre>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/mysql-cluster-api-definition.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="mysql-cluster-api-definition">
</a>
25.4.3.7 Defining SQL and Other API Nodes in an NDB Cluster
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045114596848">
</a>
<a class="indexterm" name="idm46045114595360">
</a>
<a class="indexterm" name="idm46045114593872">
</a>
<p>
The
<code class="literal">
[mysqld]
</code>
and
<code class="literal">
[api]
</code>
sections in the
<code class="filename">
config.ini
</code>
file define the
behavior of the MySQL servers (SQL nodes) and other applications
(API nodes) used to access cluster data. None of the parameters
shown is required. If no computer or host name is provided, any
host can use this SQL or API node.
</p>
<p>
Generally speaking, a
<code class="literal">
[mysqld]
</code>
section is
used to indicate a MySQL server providing an SQL interface to
the cluster, and an
<code class="literal">
[api]
</code>
section is used for
applications other than
<a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
<span class="command">
<strong>
mysqld
</strong>
</span>
</a>
processes
accessing cluster data, but the two designations are actually
synonymous; you can, for instance, list parameters for a MySQL
server acting as an SQL node in an
<code class="literal">
[api]
</code>
section.
</p>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
For a discussion of MySQL server options for NDB Cluster, see
<a class="xref" href="mysql-cluster-options-variables.html#mysql-cluster-program-options-mysqld" title="25.4.3.9.1 MySQL Server Options for NDB Cluster">
Section 25.4.3.9.1, “MySQL Server Options for NDB Cluster”
</a>
. For
information about MySQL server system variables relating to
NDB Cluster, see
<a class="xref" href="mysql-cluster-options-variables.html#mysql-cluster-system-variables" title="25.4.3.9.2 NDB Cluster System Variables">
Section 25.4.3.9.2, “NDB Cluster System Variables”
</a>
.
</p>
</div>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<a name="ndbparam-api-id">
</a>
<code class="literal">
Id
</code>
</p>
<a class="indexterm" name="idm46045114581088">
</a>
<div class="informaltable">
<a name="id-api-table">
</a>
<table frame="box" rules="all" summary="Id API node configuration parameter type and value information" width="35%">
<colgroup>
<col style="width: 50%"/>
<col style="width: 50%"/>
</colgroup>
<tbody>
<tr>
<th>
Version (or later)
</th>
<td>
NDB 8.4.0
</td>
</tr>
<tr>
<th>
Type or units
</th>
<td>
unsigned
</td>
</tr>
<tr>
<th>
Default
</th>
<td>
[...]
</td>
</tr>
<tr>
<th>
Range
</th>
<td>
1 - 255
</td>
</tr>
<tr>
<th>
Restart Type
</th>
<td>
<p>
<span class="bold">
<strong>
Initial System Restart:
</strong>
</span>
Requires a complete shutdown of the
cluster, wiping and restoring the cluster file
system from a
<a class="link" href="mysql-cluster-backup.html" title="25.6.8 Online Backup of NDB Cluster">
backup
</a>
,
and then restarting the cluster. (NDB 8.4.0)
</p>
</td>
</tr>
</tbody>
</table>
</div>
<p>
The
<code class="literal">
Id
</code>
is an integer value used to
identify the node in all cluster internal messages. The
permitted range of values is 1 to 255 inclusive. This value
must be unique for each node in the cluster, regardless of
the type of node.
</p>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
Data node IDs must be less than 145. If you plan to deploy
a large number of data nodes, it is a good idea to limit
the node IDs for API nodes (and management nodes) to
values greater than 144.
</p>
</div>
<p>
<a class="link" href="mysql-cluster-api-definition.html#ndbparam-api-nodeid">
<code class="literal">
NodeId
</code>
</a>
is the
preferred parameter name to use when identifying API nodes.
(
<code class="literal">
Id
</code>
continues to be supported for
backward compatibility, but is now deprecated and generates
a warning when used. It is also subject to future removal.)
</p>
</li>
<li class="listitem">
<p>
<a name="ndbparam-api-connectionmap">
</a>
<code class="literal">
ConnectionMap
</code>
</p>
<a class="indexterm" name="idm46045114556688">
</a>
<div class="informaltable">
<a name="connectionmap-api-table">
</a>
<table frame="box" rules="all" summary="ConnectionMap API node configuration parameter type and value information" width="35%">
<colgroup>
<col style="width: 50%"/>
<col style="width: 50%"/>
</colgroup>
<tbody>
<tr>
<th>
Version (or later)
</th>
<td>
NDB 8.4.0
</td>
</tr>
<tr>
<th>
Type or units
</th>
<td>
string
</td>
</tr>
<tr>
<th>
Default
</th>
<td>
[...]
</td>
</tr>
<tr>
<th>
Range
</th>
<td>
...
</td>
</tr>
<tr>
<th>
Restart Type
</th>
<td>
<p>
<span class="bold">
<strong>
Node Restart:
</strong>
</span>
Requires a
<a class="link" href="mysql-cluster-rolling-restart.html" title="25.6.5 Performing a Rolling Restart of an NDB Cluster">
rolling
restart
</a>
of the cluster. (NDB 8.4.0)
</p>
</td>
</tr>
</tbody>
</table>
</div>
<p>
Specifies which data nodes to connect.
</p>
</li>
<li class="listitem">
<p>
<a name="ndbparam-api-nodeid">
</a>
<code class="literal">
NodeId
</code>
</p>
<a class="indexterm" name="idm46045114536928">
</a>
<div class="informaltable">
<a name="nodeid-api-table">
</a>
<table frame="box" rules="all" summary="NodeId API node configuration parameter type and value information" width="35%">
<colgroup>
<col style="width: 50%"/>
<col style="width: 50%"/>
</colgroup>
<tbody>
<tr>
<th>
Version (or later)
</th>
<td>
NDB 8.4.0
</td>
</tr>
<tr>
<th>
Type or units
</th>
<td>
unsigned
</td>
</tr>
<tr>
<th>
Default
</th>
<td>
[...]
</td>
</tr>
<tr>
<th>
Range
</th>
<td>
1 - 255
</td>
</tr>
<tr>
<th>
Restart Type
</th>
<td>
<p>
<span class="bold">
<strong>
Initial System Restart:
</strong>
</span>
Requires a complete shutdown of the
cluster, wiping and restoring the cluster file
system from a
<a class="link" href="mysql-cluster-backup.html" title="25.6.8 Online Backup of NDB Cluster">
backup
</a>
,
and then restarting the cluster. (NDB 8.4.0)
</p>
</td>
</tr>
</tbody>
</table>
</div>
<p>
The
<code class="literal">
NodeId
</code>
is an integer value used to
identify the node in all cluster internal messages. The
permitted range of values is 1 to 255 inclusive. This value
must be unique for each node in the cluster, regardless of
the type of node.
</p>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
Data node IDs must be less than 145. If you plan to deploy
a large number of data nodes, it is a good idea to limit
the node IDs for API nodes (and management nodes) to
values greater than 144.
</p>
</div>
<p>
<a class="link" href="mysql-cluster-api-definition.html#ndbparam-api-nodeid">
<code class="literal">
NodeId
</code>
</a>
is the
preferred parameter name to use when identifying management
nodes. An alias,
<code class="literal">
Id
</code>
, was used for this
purpose in very old versions of NDB Cluster, and continues
to be supported for backward compatibility; it is now
deprecated and generates a warning when used, and is subject
to removal in a future release of NDB Cluster.
</p>
</li>
<li class="listitem">
<p>
<a name="ndbparam-api-executeoncomputer">
</a>
<code class="literal">
ExecuteOnComputer
</code>
</p>
<a class="indexterm" name="idm46045114512288">
</a>
<div class="informaltable">
<a name="executeoncomputer-api-table">
</a>
<table frame="box" rules="all" summary="ExecuteOnComputer API node configuration parameter type and value information" width="35%">
<colgroup>
<col style="width: 50%"/>
<col style="width: 50%"/>
</colgroup>
<tbody>
<tr>
<th>
Version (or later)
</th>
<td>
NDB 8.4.0
</td>
</tr>
<tr>
<th>
Type or units
</th>
<td>
name
</td>
</tr>
<tr>
<th>
Default
</th>
<td>
[...]
</td>
</tr>
<tr>
<th>
Range
</th>
<td>
...
</td>
</tr>
<tr>
<th>
Deprecated
</th>
<td>
Yes (in NDB 7.5)
</td>
</tr>
<tr>
<th>
Restart Type
</th>
<td>
<p>
<span class="bold">
<strong>
System Restart:
</strong>
</span>
Requires a complete shutdown and restart
of the cluster. (NDB 8.4.0)
</p>
</td>
</tr>
</tbody>
</table>
</div>
<p>
This refers to the
<code class="literal">
Id
</code>
set for one of the
computers (hosts) defined in a
<code class="literal">
[computer]
</code>
section of the configuration file.
</p>
<div class="important" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Important
</div>
<p>
This parameter is deprecated, and is subject to removal in
a future release. Use the
<a class="link" href="mysql-cluster-api-definition.html#ndbparam-api-hostname">
<code class="literal">
HostName
</code>
</a>
parameter
instead.
</p>
</div>
</li>
<li class="listitem">
<a name="ndbparam-api-dedicated">
</a>
<a class="indexterm" name="idm46045114488496">
</a>
<p>
</p>
<p>
The node ID for this node can be given out only to
connections that explicitly request it. A management server
that requests
<span class="quote">
“
<span class="quote">
any
</span>
”
</span>
node ID cannot use this
one. This parameter can be used when running multiple
management servers on the same host, and
<a class="link" href="mysql-cluster-api-definition.html#ndbparam-api-hostname">
<code class="literal">
HostName
</code>
</a>
is not
sufficient for distinguishing among processes.
</p>
</li>
<li class="listitem">
<p>
<a name="ndbparam-api-hostname">
</a>
<code class="literal">
HostName
</code>
</p>
<a class="indexterm" name="idm46045114482272">
</a>
<div class="informaltable">
<a name="hostname-api-table">
</a>
<table frame="box" rules="all" summary="HostName API node configuration parameter type and value information" width="35%">
<colgroup>
<col style="width: 50%"/>
<col style="width: 50%"/>
</colgroup>
<tbody>
<tr>
<th>
Version (or later)
</th>
<td>
NDB 8.4.0
</td>
</tr>
<tr>
<th>
Type or units
</th>
<td>
name or IP address
</td>
</tr>
<tr>
<th>
Default
</th>
<td>
[...]
</td>
</tr>
<tr>
<th>
Range
</th>
<td>
...
</td>
</tr>
<tr>
<th>
Restart Type
</th>
<td>
<p>
<span class="bold">
<strong>
Node Restart:
</strong>
</span>
Requires a
<a class="link" href="mysql-cluster-rolling-restart.html" title="25.6.5 Performing a Rolling Restart of an NDB Cluster">
rolling
restart
</a>
of the cluster. (NDB 8.4.0)
</p>
</td>
</tr>
</tbody>
</table>
</div>
<p>
Specifying this parameter defines the hostname of the
computer on which the SQL node (API node) is to reside. Use
<code class="literal">
HostName
</code>
to specify a host name other
than
<code class="literal">
localhost
</code>
.
</p>
<p>
If no
<code class="literal">
HostName
</code>
is specified in a given
<code class="literal">
[mysql]
</code>
or
<code class="literal">
[api]
</code>
section of the
<code class="filename">
config.ini
</code>
file, then an
SQL or API node may connect using the corresponding
<span class="quote">
“
<span class="quote">
slot
</span>
”
</span>
from any host which can establish a
network connection to the management server host machine.
<span class="emphasis">
<em>
This differs from the default behavior for data
nodes, where
<code class="literal">
localhost
</code>
is assumed for
<code class="literal">
HostName
</code>
unless otherwise
specified
</em>
</span>
.
</p>
</li>
<li class="listitem">
<p>
<a name="ndbparam-api-locationdomainid">
</a>
<a class="link" href="mysql-cluster-api-definition.html#ndbparam-api-locationdomainid">
<code class="literal">
LocationDomainId
</code>
</a>
</p>
<a class="indexterm" name="idm46045114454368">
</a>
<div class="informaltable">
<a name="locationdomainid-api-table">
</a>
<table frame="box" rules="all" summary="LocationDomainId API node configuration parameter type and value information" width="35%">
<colgroup>
<col style="width: 50%"/>
<col style="width: 50%"/>
</colgroup>
<tbody>
<tr>
<th>
Version (or later)
</th>
<td>
NDB 8.4.0
</td>
</tr>
<tr>
<th>
Type or units
</th>
<td>
integer
</td>
</tr>
<tr>
<th>
Default
</th>
<td>
0
</td>
</tr>
<tr>
<th>
Range
</th>
<td>
0 - 16
</td>
</tr>
<tr>
<th>
Restart Type
</th>
<td>
<p>
<span class="bold">
<strong>
System Restart:
</strong>
</span>
Requires a complete shutdown and restart
of the cluster. (NDB 8.4.0)
</p>
</td>
</tr>
</tbody>
</table>
</div>
<p>
Assigns an SQL or other API node to a specific
<a class="ulink" href="https://docs.us-phoenix-1.oraclecloud.com/Content/General/Concepts/regions.htm" target="_blank">
availability
domain
</a>
(also known as an availability zone) within a
cloud. By informing
<code class="literal">
NDB
</code>
which nodes are
in which availability domains, performance can be improved
in a cloud environment in the following ways:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
If requested data is not found on the same node, reads
can be directed to another node in the same availability
domain.
</p>
</li>
<li class="listitem">
<p>
Communication between nodes in different availability
domains are guaranteed to use
<code class="literal">
NDB
</code>
transporters' WAN support without any further
manual intervention.
</p>
</li>
<li class="listitem">
<p>
The transporter's group number can be based on
which availability domain is used, such that also SQL
and other API nodes communicate with local data nodes in
the same availability domain whenever possible.
</p>
</li>
<li class="listitem">
<p>
The arbitrator can be selected from an availability
domain in which no data nodes are present, or, if no
such availability domain can be found, from a third
availability domain.
</p>
</li>
</ul>
</div>
<p>
<code class="literal">
LocationDomainId
</code>
takes an integer value
between 0 and 16 inclusive, with 0 being the default; using
0 is the same as leaving the parameter unset.
</p>
</li>
<li class="listitem">
<p>
<a name="ndbparam-api-arbitrationrank">
</a>
<code class="literal">
ArbitrationRank
</code>
</p>
<a class="indexterm" name="idm46045114427280">
</a>
<div class="informaltable">
<a name="arbitrationrank-api-table">
</a>
<table frame="box" rules="all" summary="ArbitrationRank API node configuration parameter type and value information" width="35%">
<colgroup>
<col style="width: 50%"/>
<col style="width: 50%"/>
</colgroup>
<tbody>
<tr>
<th>
Version (or later)
</th>
<td>
NDB 8.4.0
</td>
</tr>
<tr>
<th>
Type or units
</th>
<td>
0-2
</td>
</tr>
<tr>
<th>
Default
</th>
<td>
0
</td>
</tr>
<tr>
<th>
Range
</th>
<td>
0 - 2
</td>
</tr>
<tr>
<th>
Restart Type
</th>
<td>
<p>
<span class="bold">
<strong>
Node Restart:
</strong>
</span>
Requires a
<a class="link" href="mysql-cluster-rolling-restart.html" title="25.6.5 Performing a Rolling Restart of an NDB Cluster">
rolling
restart
</a>
of the cluster. (NDB 8.4.0)
</p>
</td>
</tr>
</tbody>
</table>
</div>
<p>
This parameter defines which nodes can act as arbitrators.
Both management nodes and SQL nodes can be arbitrators. A
value of 0 means that the given node is never used as an
arbitrator, a value of 1 gives the node high priority as an
arbitrator, and a value of 2 gives it low priority. A normal
configuration uses the management server as arbitrator,
setting its
<code class="literal">
ArbitrationRank
</code>
to 1 (the
default for management nodes) and those for all SQL nodes to
0 (the default for SQL nodes).
</p>
<p>
By setting
<code class="literal">
ArbitrationRank
</code>
to 0 on all
management and SQL nodes, you can disable arbitration
completely. You can also control arbitration by overriding
this parameter; to do so, set the
<a class="link" href="mysql-cluster-ndbd-definition.html#ndbparam-ndbd-arbitration">
<code class="literal">
Arbitration
</code>
</a>
parameter in the
<code class="literal">
[ndbd default]
</code>
section
of the
<code class="filename">
config.ini
</code>
global configuration
file.
</p>
</li>
<li class="listitem">
<p>
<a name="ndbparam-api-arbitrationdelay">
</a>
<code class="literal">
ArbitrationDelay
</code>
</p>
<a class="indexterm" name="idm46045114402208">
</a>
<div class="informaltable">
<a name="arbitrationdelay-api-table">
</a>
<table frame="box" rules="all" summary="ArbitrationDelay API node configuration parameter type and value information" width="35%">
<colgroup>
<col style="width: 50%"/>
<col style="width: 50%"/>
</colgroup>
<tbody>
<tr>
<th>
Version (or later)
</th>
<td>
NDB 8.4.0
</td>
</tr>
<tr>
<th>
Type or units
</th>
<td>
milliseconds
</td>
</tr>
<tr>
<th>
Default
</th>
<td>
0
</td>
</tr>
<tr>
<th>
Range
</th>
<td>
0 - 4294967039 (0xFFFFFEFF)
</td>
</tr>
<tr>
<th>
Restart Type
</th>
<td>
<p>
<span class="bold">
<strong>
Node Restart:
</strong>
</span>
Requires a
<a class="link" href="mysql-cluster-rolling-restart.html" title="25.6.5 Performing a Rolling Restart of an NDB Cluster">
rolling
restart
</a>
of the cluster. (NDB 8.4.0)
</p>
</td>
</tr>
</tbody>
</table>
</div>
<p>
Setting this parameter to any other value than 0 (the
default) means that responses by the arbitrator to
arbitration requests are delayed by the stated number of
milliseconds. It is usually not necessary to change this
value.
</p>
</li>
<li class="listitem">
<p>
<a name="ndbparam-api-batchbytesize">
</a>
<a class="link" href="mysql-cluster-api-definition.html#ndbparam-api-batchbytesize">
<code class="literal">
BatchByteSize
</code>
</a>
</p>
<a class="indexterm" name="idm46045114381472">
</a>
<div class="informaltable">
<a name="batchbytesize-api-table">
</a>
<table frame="box" rules="all" summary="BatchByteSize API node configuration parameter type and value information" width="35%">
<colgroup>
<col style="width: 50%"/>
<col style="width: 50%"/>
</colgroup>
<tbody>
<tr>
<th>
Version (or later)
</th>
<td>
NDB 8.4.0
</td>
</tr>
<tr>
<th>
Type or units
</th>
<td>
bytes
</td>
</tr>
<tr>
<th>
Default
</th>
<td>
16K
</td>
</tr>
<tr>
<th>
Range
</th>
<td>
1K - 1M
</td>
</tr>
<tr>
<th>
Restart Type
</th>
<td>
<p>
<span class="bold">
<strong>
Node Restart:
</strong>
</span>
Requires a
<a class="link" href="mysql-cluster-rolling-restart.html" title="25.6.5 Performing a Rolling Restart of an NDB Cluster">
rolling
restart
</a>
of the cluster. (NDB 8.4.0)
</p>
</td>
</tr>
</tbody>
</table>
</div>
<p>
For queries that are translated into full table scans or
range scans on indexes, it is important for best performance
to fetch records in properly sized batches. It is possible
to set the proper size both in terms of number of records
(
<a class="link" href="mysql-cluster-api-definition.html#ndbparam-api-batchsize">
<code class="literal">
BatchSize
</code>
</a>
) and in
terms of bytes (
<code class="literal">
BatchByteSize
</code>
). The
actual batch size is limited by both parameters.
</p>
<p>
The speed at which queries are performed can vary by more
than 40% depending upon how this parameter is set.
</p>
<p>
This parameter is measured in bytes. The default value is
16K.
</p>
</li>
<li class="listitem">
<p>
<a name="ndbparam-api-batchsize">
</a>
<a class="link" href="mysql-cluster-api-definition.html#ndbparam-api-batchsize">
<code class="literal">
BatchSize
</code>
</a>
</p>
<a class="indexterm" name="idm46045114357888">
</a>
<div class="informaltable">
<a name="batchsize-api-table">
</a>
<table frame="box" rules="all" summary="BatchSize API node configuration parameter type and value information" width="35%">
<colgroup>
<col style="width: 50%"/>
<col style="width: 50%"/>
</colgroup>
<tbody>
<tr>
<th>
Version (or later)
</th>
<td>
NDB 8.4.0
</td>
</tr>
<tr>
<th>
Type or units
</th>
<td>
records
</td>
</tr>
<tr>
<th>
Default
</th>
<td>
256
</td>
</tr>
<tr>
<th>
Range
</th>
<td>
1 - 992
</td>
</tr>
<tr>
<th>
Restart Type
</th>
<td>
<p>
<span class="bold">
<strong>
Node Restart:
</strong>
</span>
Requires a
<a class="link" href="mysql-cluster-rolling-restart.html" title="25.6.5 Performing a Rolling Restart of an NDB Cluster">
rolling
restart
</a>
of the cluster. (NDB 8.4.0)
</p>
</td>
</tr>
</tbody>
</table>
</div>
<p>
This parameter is measured in number of records and is by
default set to 256. The maximum size is 992.
</p>
</li>
<li class="listitem">
<p>
<a name="ndbparam-api-extrasendbuffermemory">
</a>
<a class="link" href="mysql-cluster-api-definition.html#ndbparam-api-extrasendbuffermemory">
<code class="literal">
ExtraSendBufferMemory
</code>
</a>
</p>
<a class="indexterm" name="idm46045114337392">
</a>
<div class="informaltable">
<a name="extrasendbuffermemory-api-table">
</a>
<table frame="box" rules="all" summary="ExtraSendBufferMemory API node configuration parameter type and value information" width="35%">
<colgroup>
<col style="width: 50%"/>
<col style="width: 50%"/>
</colgroup>
<tbody>
<tr>
<th>
Version (or later)
</th>
<td>
NDB 8.4.0
</td>
</tr>
<tr>
<th>
Type or units
</th>
<td>
bytes
</td>
</tr>
<tr>
<th>
Default
</th>
<td>
0
</td>
</tr>
<tr>
<th>
Range
</th>
<td>
0 - 4294967039 (0xFFFFFEFF)
</td>
</tr>
<tr>
<th>
Restart Type
</th>
<td>
<p>
<span class="bold">
<strong>
Node Restart:
</strong>
</span>
Requires a
<a class="link" href="mysql-cluster-rolling-restart.html" title="25.6.5 Performing a Rolling Restart of an NDB Cluster">
rolling
restart
</a>
of the cluster. (NDB 8.4.0)
</p>
</td>
</tr>
</tbody>
</table>
</div>
<p>
This parameter specifies the amount of transporter send
buffer memory to allocate in addition to any that has been
set using
<a class="link" href="mysql-cluster-api-definition.html#ndbparam-api-totalsendbuffermemory">
<code class="literal">
TotalSendBufferMemory
</code>
</a>
,
<a class="link" href="mysql-cluster-tcp-definition.html#ndbparam-tcp-sendbuffermemory">
<code class="literal">
SendBufferMemory
</code>
</a>
, or
both.
</p>
</li>
<li class="listitem">
<p>
<a name="ndbparam-api-heartbeatthreadpriority">
</a>
<a class="link" href="mysql-cluster-api-definition.html#ndbparam-api-heartbeatthreadpriority">
<code class="literal">
HeartbeatThreadPriority
</code>
</a>
</p>
<a class="indexterm" name="idm46045114313888">
</a>
<div class="informaltable">
<a name="heartbeatthreadpriority-api-table">
</a>
<table frame="box" rules="all" summary="HeartbeatThreadPriority API node configuration parameter type and value information" width="35%">
<colgroup>
<col style="width: 50%"/>
<col style="width: 50%"/>
</colgroup>
<tbody>
<tr>
<th>
Version (or later)
</th>
<td>
NDB 8.4.0
</td>
</tr>
<tr>
<th>
Type or units
</th>
<td>
string
</td>
</tr>
<tr>
<th>
Default
</th>
<td>
[...]
</td>
</tr>
<tr>
<th>
Range
</th>
<td>
...
</td>
</tr>
<tr>
<th>
Restart Type
</th>
<td>
<p>
<span class="bold">
<strong>
Node Restart:
</strong>
</span>
Requires a
<a class="link" href="mysql-cluster-rolling-restart.html" title="25.6.5 Performing a Rolling Restart of an NDB Cluster">
rolling
restart
</a>
of the cluster. (NDB 8.4.0)
</p>
</td>
</tr>
</tbody>
</table>
</div>
<p>
Use this parameter to set the scheduling policy and priority
of heartbeat threads for management and API nodes. The
syntax for setting this parameter is shown here:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-simple"><div class="docs-select-all right" id="sa94625309"><div class="copy-help left">Press ⌘+C to 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">HeartbeatThreadPriority <span class="token operator">=</span> <em class="replaceable">policy</em><span class="token punctuation">[</span><span class="token punctuation">,</span> <em class="replaceable">priority</em><span class="token punctuation">]</span>
<em class="replaceable">policy</em><span class="token operator">:</span>
<span class="token punctuation">{</span>FIFO <span class="token operator">|</span> RR<span class="token punctuation">}</span></code></pre>
</div>
<p>
When setting this parameter, you must specify a policy. This
is one of
<code class="literal">
FIFO
</code>
(first in, first in) or
<code class="literal">
RR
</code>
(round robin). This followed
optionally by the priority (an integer).
</p>
</li>
<li class="listitem">
<p>
<a name="ndbparam-api-maxscanbatchsize">
</a>
<a class="link" href="mysql-cluster-api-definition.html#ndbparam-api-maxscanbatchsize">
<code class="literal">
MaxScanBatchSize
</code>
</a>
</p>
<a class="indexterm" name="idm46045114289072">
</a>
<div class="informaltable">
<a name="maxscanbatchsize-api-table">
</a>
<table frame="box" rules="all" summary="MaxScanBatchSize API node configuration parameter type and value information" width="35%">
<colgroup>
<col style="width: 50%"/>
<col style="width: 50%"/>
</colgroup>
<tbody>
<tr>
<th>
Version (or later)
</th>
<td>
NDB 8.4.0
</td>
</tr>
<tr>
<th>
Type or units
</th>
<td>
bytes
</td>
</tr>
<tr>
<th>
Default
</th>
<td>
256K
</td>
</tr>
<tr>
<th>
Range
</th>
<td>
32K - 16M
</td>
</tr>
<tr>
<th>
Restart Type
</th>
<td>
<p>
<span class="bold">
<strong>
Node Restart:
</strong>
</span>
Requires a
<a class="link" href="mysql-cluster-rolling-restart.html" title="25.6.5 Performing a Rolling Restart of an NDB Cluster">
rolling
restart
</a>
of the cluster. (NDB 8.4.0)
</p>
</td>
</tr>
</tbody>
</table>
</div>
<p>
The batch size is the size of each batch sent from each data
node. Most scans are performed in parallel to protect the
MySQL Server from receiving too much data from many nodes in
parallel; this parameter sets a limit to the total batch
size over all nodes.
</p>
<p>
The default value of this parameter is set to 256KB. Its
maximum size is 16MB.
</p>
</li>
<li class="listitem">
<p>
<a name="ndbparam-api-totalsendbuffermemory">
</a>
<code class="literal">
TotalSendBufferMemory
</code>
</p>
<a class="indexterm" name="idm46045114268448">
</a>
<div class="informaltable">
<a name="totalsendbuffermemory-api-table">
</a>
<table frame="box" rules="all" summary="TotalSendBufferMemory API node configuration parameter type and value information" width="35%">
<colgroup>
<col style="width: 50%"/>
<col style="width: 50%"/>
</colgroup>
<tbody>
<tr>
<th>
Version (or later)
</th>
<td>
NDB 8.4.0
</td>
</tr>
<tr>
<th>
Type or units
</th>
<td>
bytes
</td>
</tr>
<tr>
<th>
Default
</th>
<td>
0
</td>
</tr>
<tr>
<th>
Range
</th>
<td>
256K - 4294967039 (0xFFFFFEFF)
</td>
</tr>
<tr>
<th>
Restart Type
</th>
<td>
<p>
<span class="bold">
<strong>
Node Restart:
</strong>
</span>
Requires a
<a class="link" href="mysql-cluster-rolling-restart.html" title="25.6.5 Performing a Rolling Restart of an NDB Cluster">
rolling
restart
</a>
of the cluster. (NDB 8.4.0)
</p>
</td>
</tr>
</tbody>
</table>
</div>
<p>
This parameter is used to determine the total amount of
memory to allocate on this node for shared send buffer
memory among all configured transporters.
</p>
<p>
If this parameter is set, its minimum permitted value is
256KB; 0 indicates that the parameter has not been set. For
more detailed information, see
<a class="xref" href="mysql-cluster-config-send-buffers.html" title="25.4.3.14 Configuring NDB Cluster Send Buffer Parameters">
Section 25.4.3.14, “Configuring NDB Cluster Send Buffer Parameters”
</a>
.
</p>
</li>
<li class="listitem">
<p>
<a name="ndbparam-api-autoreconnect">
</a>
<a class="link" href="mysql-cluster-api-definition.html#ndbparam-api-autoreconnect">
<code class="literal">
AutoReconnect
</code>
</a>
</p>
<a class="indexterm" name="idm46045114246224">
</a>
<div class="informaltable">
<a name="autoreconnect-api-table">
</a>
<table frame="box" rules="all" summary="AutoReconnect API node configuration parameter type and value information" width="35%">
<colgroup>
<col style="width: 50%"/>
<col style="width: 50%"/>
</colgroup>
<tbody>
<tr>
<th>
Version (or later)
</th>
<td>
NDB 8.4.0
</td>
</tr>
<tr>
<th>
Type or units
</th>
<td>
boolean
</td>
</tr>
<tr>
<th>
Default
</th>
<td>
false
</td>
</tr>
<tr>
<th>
Range
</th>
<td>
true, false
</td>
</tr>
<tr>
<th>
Restart Type
</th>
<td>
<p>
<span class="bold">
<strong>
Node Restart:
</strong>
</span>
Requires a
<a class="link" href="mysql-cluster-rolling-restart.html" title="25.6.5 Performing a Rolling Restart of an NDB Cluster">
rolling
restart
</a>
of the cluster. (NDB 8.4.0)
</p>
</td>
</tr>
</tbody>
</table>
</div>
<p>
This parameter is
<code class="literal">
false
</code>
by default. This
forces disconnected API nodes (including MySQL Servers
acting as SQL nodes) to use a new connection to the cluster
rather than attempting to re-use an existing one, as re-use
of connections can cause problems when using
dynamically-allocated node IDs. (Bug #45921)
</p>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
This parameter can be overridden using the NDB API. For
more information, see
<a class="ulink" href="/doc/ndbapi/en/ndb-ndb-cluster-connection.html#ndb-ndb-cluster-connection-set-auto-reconnect" target="_top">
Ndb_cluster_connection::set_auto_reconnect()
</a>
,
and
<a class="ulink" href="/doc/ndbapi/en/ndb-ndb-cluster-connection.html#ndb-ndb-cluster-connection-get-auto-reconnect" target="_top">
Ndb_cluster_connection::get_auto_reconnect()
</a>
.
</p>
</div>
</li>
<li class="listitem">
<p>
<a name="ndbparam-api-defaultoperationredoproblemaction">
</a>
<a class="link" href="mysql-cluster-api-definition.html#ndbparam-api-defaultoperationredoproblemaction">
<code class="literal">
DefaultOperationRedoProblemAction
</code>
</a>
</p>
<a class="indexterm" name="idm46045114221648">
</a>
<div class="informaltable">
<a name="defaultoperationredoproblemaction-api-table">
</a>
<table frame="box" rules="all" summary="DefaultOperationRedoProblemAction API node configuration parameter type and value information" width="35%">
<colgroup>
<col style="width: 50%"/>
<col style="width: 50%"/>
</colgroup>
<tbody>
<tr>
<th>
Version (or later)
</th>
<td>
NDB 8.4.0
</td>
</tr>
<tr>
<th>
Type or units
</th>
<td>
enumeration
</td>
</tr>
<tr>
<th>
Default
</th>
<td>
QUEUE
</td>
</tr>
<tr>
<th>
Range
</th>
<td>
ABORT, QUEUE
</td>
</tr>
<tr>
<th>
Restart Type
</th>
<td>
<p>
<span class="bold">
<strong>
Node Restart:
</strong>
</span>
Requires a
<a class="link" href="mysql-cluster-rolling-restart.html" title="25.6.5 Performing a Rolling Restart of an NDB Cluster">
rolling
restart
</a>
of the cluster. (NDB 8.4.0)
</p>
</td>
</tr>
</tbody>
</table>
</div>
<p>
This parameter (along with
<a class="link" href="mysql-cluster-ndbd-definition.html#ndbparam-ndbd-redoovercommitlimit">
<code class="literal">
RedoOverCommitLimit
</code>
</a>
and
<a class="link" href="mysql-cluster-ndbd-definition.html#ndbparam-ndbd-redoovercommitcounter">
<code class="literal">
RedoOverCommitCounter
</code>
</a>
)
controls the data node's handling of operations when
too much time is taken flushing redo logs to disk. This
occurs when a given redo log flush takes longer than
<a class="link" href="mysql-cluster-ndbd-definition.html#ndbparam-ndbd-redoovercommitlimit">
<code class="literal">
RedoOverCommitLimit
</code>
</a>
seconds, more than
<a class="link" href="mysql-cluster-ndbd-definition.html#ndbparam-ndbd-redoovercommitcounter">
<code class="literal">
RedoOverCommitCounter
</code>
</a>
times, causing any pending transactions to be aborted.
</p>
<p>
When this happens, the node can respond in either of two
ways, according to the value of
<code class="literal">
DefaultOperationRedoProblemAction
</code>
, listed
here:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
<code class="literal">
ABORT
</code>
: Any pending operations from
aborted transactions are also aborted.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
QUEUE
</code>
: Pending operations from
transactions that were aborted are queued up to be
re-tried. This the default. Pending operations are still
aborted when the redo log runs out of space—that
is, when
<span class="errorname">
P_TAIL_PROBLEM
</span>
errors
occur.
</p>
</li>
</ul>
</div>
</li>
<li class="listitem">
<p>
<a name="ndbparam-api-defaulthashmapsize">
</a>
<a class="link" href="mysql-cluster-api-definition.html#ndbparam-api-defaulthashmapsize">
<code class="literal">
DefaultHashMapSize
</code>
</a>
</p>
<a class="indexterm" name="idm46045114189696">
</a>
<div class="informaltable">
<a name="defaulthashmapsize-api-table">
</a>
<table frame="box" rules="all" summary="DefaultHashMapSize API node configuration parameter type and value information" width="35%">
<colgroup>
<col style="width: 50%"/>
<col style="width: 50%"/>
</colgroup>
<tbody>
<tr>
<th>
Version (or later)
</th>
<td>
NDB 8.4.0
</td>
</tr>
<tr>
<th>
Type or units
</th>
<td>
buckets
</td>
</tr>
<tr>
<th>
Default
</th>
<td>
3840
</td>
</tr>
<tr>
<th>
Range
</th>
<td>
0 - 3840
</td>
</tr>
<tr>
<th>
Restart Type
</th>
<td>
<p>
<span class="bold">
<strong>
Node Restart:
</strong>
</span>
Requires a
<a class="link" href="mysql-cluster-rolling-restart.html" title="25.6.5 Performing a Rolling Restart of an NDB Cluster">
rolling
restart
</a>
of the cluster. (NDB 8.4.0)
</p>
</td>
</tr>
</tbody>
</table>
</div>
<p>
The size of the table hash maps used by
<a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4">
<code class="literal">
NDB
</code>
</a>
is configurable using this
parameter.
<code class="literal">
DefaultHashMapSize
</code>
can take
any of three possible values (0, 240, 3840). These values
and their effects are described in the following table.
</p>
<div class="table">
<a name="idm46045114169664">
</a>
<p class="title">
<b>
Table 25.16 DefaultHashMapSize parameter values
</b>
</p>
<div class="table-contents">
<table>
<colgroup>
<col style="width: 20%"/>
<col style="width: 80%"/>
</colgroup>
<thead>
<tr>
<th>
Value
</th>
<th>
Description / Effect
</th>
</tr>
</thead>
<tbody>
<tr>
<td>
<code class="literal">
0
</code>
</td>
<td>
Use the lowest value set, if any, for this parameter among all data
nodes and API nodes in the cluster; if it is not set
on any data or API node, use the default value.
</td>
</tr>
<tr>
<td>
<code class="literal">
240
</code>
</td>
<td>
Old default hash map size
</td>
</tr>
<tr>
<td>
<code class="literal">
3840
</code>
</td>
<td>
Hash map size used by default in NDB 8.4
</td>
</tr>
</tbody>
</table>
</div>
</div>
<br class="table-break"/>
<p>
The original intended use for this parameter was to
facilitate upgrades and downgrades to and from older NDB
Cluster versions, in which the hash map size differed, due
to the fact that this change was not otherwise backward
compatible.
</p>
</li>
<li class="listitem">
<p>
<a name="ndbparam-api-wan">
</a>
<a class="link" href="mysql-cluster-api-definition.html#ndbparam-api-wan">
<code class="literal">
Wan
</code>
</a>
</p>
<a class="indexterm" name="idm46045114153456">
</a>
<div class="informaltable">
<a name="wan-api-table">
</a>
<table frame="box" rules="all" summary="wan API node configuration parameter type and value information" width="35%">
<colgroup>
<col style="width: 50%"/>
<col style="width: 50%"/>
</colgroup>
<tbody>
<tr>
<th>
Version (or later)
</th>
<td>
NDB 8.4.0
</td>
</tr>
<tr>
<th>
Type or units
</th>
<td>
boolean
</td>
</tr>
<tr>
<th>
Default
</th>
<td>
false
</td>
</tr>
<tr>
<th>
Range
</th>
<td>
true, false
</td>
</tr>
<tr>
<th>
Restart Type
</th>
<td>
<p>
<span class="bold">
<strong>
Node Restart:
</strong>
</span>
Requires a
<a class="link" href="mysql-cluster-rolling-restart.html" title="25.6.5 Performing a Rolling Restart of an NDB Cluster">
rolling
restart
</a>
of the cluster. (NDB 8.4.0)
</p>
</td>
</tr>
</tbody>
</table>
</div>
<p>
Use WAN TCP setting as default.
</p>
</li>
<li class="listitem">
<p>
<a name="ndbparam-api-connectbackoffmaxtime">
</a>
<a class="link" href="mysql-cluster-api-definition.html#ndbparam-api-connectbackoffmaxtime">
<code class="literal">
ConnectBackoffMaxTime
</code>
</a>
</p>
<a class="indexterm" name="idm46045114133056">
</a>
<div class="informaltable">
<a name="connectbackoffmaxtime-api-table">
</a>
<table frame="box" rules="all" summary="ConnectBackoffMaxTime API node configuration parameter type and value information" width="35%">
<colgroup>
<col style="width: 50%"/>
<col style="width: 50%"/>
</colgroup>
<tbody>
<tr>
<th>
Version (or later)
</th>
<td>
NDB 8.4.0
</td>
</tr>
<tr>
<th>
Type or units
</th>
<td>
integer
</td>
</tr>
<tr>
<th>
Default
</th>
<td>
0
</td>
</tr>
<tr>
<th>
Range
</th>
<td>
0 - 4294967039 (0xFFFFFEFF)
</td>
</tr>
<tr>
<th>
Restart Type
</th>
<td>
<p>
<span class="bold">
<strong>
Node Restart:
</strong>
</span>
Requires a
<a class="link" href="mysql-cluster-rolling-restart.html" title="25.6.5 Performing a Rolling Restart of an NDB Cluster">
rolling
restart
</a>
of the cluster. (NDB 8.4.0)
</p>
</td>
</tr>
</tbody>
</table>
</div>
<p>
In an NDB Cluster with many unstarted data nodes, the value
of this parameter can be raised to circumvent connection
attempts to data nodes which have not yet begun to function
in the cluster, as well as moderate high traffic to
management nodes. As long as the API node is not connected
to any new data nodes, the value of the
<a class="link" href="mysql-cluster-api-definition.html#ndbparam-api-startconnectbackoffmaxtime">
<code class="literal">
StartConnectBackoffMaxTime
</code>
</a>
parameter is applied; otherwise,
<code class="literal">
ConnectBackoffMaxTime
</code>
is used to
determine the length of time in milliseconds to wait between
connection attempts.
</p>
<p>
Time elapsed
<span class="emphasis">
<em>
during
</em>
</span>
node connection
attempts is not taken into account when calculating elapsed
time for this parameter. The timeout is applied with
approximately 100 ms resolution, starting with a 100 ms
delay; for each subsequent attempt, the length of this
period is doubled until it reaches
<code class="literal">
ConnectBackoffMaxTime
</code>
milliseconds, up to
a maximum of 100000 ms (100s).
</p>
<p>
Once the API node is connected to a data node and that node
reports (in a heartbeat message) that it has connected to
other data nodes, connection attempts to those data nodes
are no longer affected by this parameter, and are made every
100 ms thereafter until connected. Once a data node has
started, it can take up
<a class="link" href="mysql-cluster-ndbd-definition.html#ndbparam-ndbd-heartbeatintervaldbapi">
<code class="literal">
HeartbeatIntervalDbApi
</code>
</a>
for the API node to be notified that this has occurred.
</p>
</li>
<li class="listitem">
<p>
<a name="ndbparam-api-startconnectbackoffmaxtime">
</a>
<a class="link" href="mysql-cluster-api-definition.html#ndbparam-api-startconnectbackoffmaxtime">
<code class="literal">
StartConnectBackoffMaxTime
</code>
</a>
</p>
<a class="indexterm" name="idm46045114105728">
</a>
<div class="informaltable">
<a name="startconnectbackoffmaxtime-api-table">
</a>
<table frame="box" rules="all" summary="StartConnectBackoffMaxTime API node configuration parameter type and value information" width="35%">
<colgroup>
<col style="width: 50%"/>
<col style="width: 50%"/>
</colgroup>
<tbody>
<tr>
<th>
Version (or later)
</th>
<td>
NDB 8.4.0
</td>
</tr>
<tr>
<th>
Type or units
</th>
<td>
integer
</td>
</tr>
<tr>
<th>
Default
</th>
<td>
0
</td>
</tr>
<tr>
<th>
Range
</th>
<td>
0 - 4294967039 (0xFFFFFEFF)
</td>
</tr>
<tr>
<th>
Restart Type
</th>
<td>
<p>
<span class="bold">
<strong>
Node Restart:
</strong>
</span>
Requires a
<a class="link" href="mysql-cluster-rolling-restart.html" title="25.6.5 Performing a Rolling Restart of an NDB Cluster">
rolling
restart
</a>
of the cluster. (NDB 8.4.0)
</p>
</td>
</tr>
</tbody>
</table>
</div>
<p>
In an NDB Cluster with many unstarted data nodes, the value
of this parameter can be raised to circumvent connection
attempts to data nodes which have not yet begun to function
in the cluster, as well as moderate high traffic to
management nodes. As long as the API node is not connected
to any new data nodes, the value of the
<code class="literal">
StartConnectBackoffMaxTime
</code>
parameter is
applied; otherwise,
<a class="link" href="mysql-cluster-api-definition.html#ndbparam-api-connectbackoffmaxtime">
<code class="literal">
ConnectBackoffMaxTime
</code>
</a>
is used to determine the length of time in milliseconds to
wait between connection attempts.
</p>
<p>
Time elapsed
<span class="emphasis">
<em>
during
</em>
</span>
node connection
attempts is not taken into account when calculating elapsed
time for this parameter. The timeout is applied with
approximately 100 ms resolution, starting with a 100 ms
delay; for each subsequent attempt, the length of this
period is doubled until it reaches
<code class="literal">
StartConnectBackoffMaxTime
</code>
milliseconds,
up to a maximum of 100000 ms (100s).
</p>
<p>
Once the API node is connected to a data node and that node
reports (in a heartbeat message) that it has connected to
other data nodes, connection attempts to those data nodes
are no longer affected by this parameter, and are made every
100 ms thereafter until connected. Once a data node has
started, it can take up
<a class="link" href="mysql-cluster-ndbd-definition.html#ndbparam-ndbd-heartbeatintervaldbapi">
<code class="literal">
HeartbeatIntervalDbApi
</code>
</a>
for the API node to be notified that this has occurred.
</p>
</li>
</ul>
</div>
<p>
<a name="ndbparam-api-apiverbose">
</a>
<b>
API Node Debugging Parameters.
</b>
You can use the
<code class="literal">
ApiVerbose
</code>
configuration
parameter to enable debugging output from a given API node.
This parameter takes an integer value. 0 is the default, and
disables such debugging; 1 enables debugging output to the
cluster log; 2 adds
<a class="ulink" href="/doc/ndb-internals/en/ndb-internals-kernel-blocks-dbdict.html" target="_top">
<code class="literal">
DBDICT
</code>
</a>
debugging output as well. (Bug #20638450) See also
<a class="ulink" href="/doc/ndb-internals/en/dump-command-1229.html" target="_top">
DUMP 1229
</a>
.
</p>
<p>
You can also obtain information from a MySQL server running as
an NDB Cluster SQL node using
<a class="link" href="show-status.html" title="15.7.7.37 SHOW STATUS Statement">
<code class="literal">
SHOW
STATUS
</code>
</a>
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, as
shown here:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa96556202"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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">STATUS</span> <span class="token operator">LIKE</span> <span class="token string">'ndb%'</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>
<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 class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><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> Ndb_cluster_node_id <span class="token punctuation">|</span> 5 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> Ndb_config_from_host <span class="token punctuation">|</span> 198.51.100.112 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> Ndb_config_from_port <span class="token punctuation">|</span> 1186 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> Ndb_number_of_storage_nodes <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>
<span class="token output">4 rows in set (0.02 sec)</span></code></pre>
</div>
<p>
For information about the status variables appearing in the
output from this statement, see
<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 class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
To add new SQL or API nodes to the configuration of a running
NDB Cluster, it is necessary to perform a rolling restart of
all cluster nodes after adding new
<code class="literal">
[mysqld]
</code>
or
<code class="literal">
[api]
</code>
sections to the
<code class="filename">
config.ini
</code>
file (or files, if you are
using more than one management server). This must be done
before the new SQL or API nodes can connect to the cluster.
</p>
<p>
It is
<span class="emphasis">
<em>
not
</em>
</span>
necessary to perform any
restart of the cluster if new SQL or API nodes can employ
previously unused API slots in the cluster configuration to
connect to the cluster.
</p>
</div>
<p>
<a name="mysql-cluster-api-definition-restart-types">
</a>
<b>
Restart types.
</b>
Information about the restart types used by the parameter
descriptions in this section is shown in the following table:
</p>
<div class="table">
<a name="idm46045114063744">
</a>
<p class="title">
<b>
Table 25.17 NDB Cluster restart types
</b>
</p>
<div class="table-contents">
<table>
<colgroup>
<col style="width: 10%"/>
<col style="width: 30%"/>
<col style="width: 60%"/>
</colgroup>
<thead>
<tr>
<th scope="col">
Symbol
</th>
<th scope="col">
Restart Type
</th>
<th scope="col">
Description
</th>
</tr>
</thead>
<tbody>
<tr>
<th scope="row">
N
</th>
<td>
Node
</td>
<td>
The parameter can be updated using a rolling restart (see
<a class="xref" href="mysql-cluster-rolling-restart.html" title="25.6.5 Performing a Rolling Restart of an NDB Cluster">
Section 25.6.5, “Performing a Rolling Restart of an NDB Cluster”
</a>
)
</td>
</tr>
<tr>
<th scope="row">
S
</th>
<td>
System
</td>
<td>
All cluster nodes must be shut down completely, then restarted, to
effect a change in this parameter
</td>
</tr>
<tr>
<th scope="row">
I
</th>
<td>
Initial
</td>
<td>
Data nodes must be restarted using the
<a class="link" href="mysql-cluster-programs-ndbd.html#option_ndbd_initial">
<code class="option">
--initial
</code>
</a>
option
</td>
</tr>
</tbody>
</table>
</div>
</div>
<br class="table-break"/>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/multiple-data-directories.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="multiple-data-directories">
</a>
7.8.1 Setting Up Multiple Data Directories
</h3>
</div>
</div>
</div>
<p>
Each MySQL Instance on a machine should have its own data
directory. The location is specified using the
<a class="link" href="server-system-variables.html#sysvar_datadir">
<code class="option">
--datadir=
<em class="replaceable">
<code>
dir_name
</code>
</em>
</code>
</a>
option.
</p>
<p>
There are different methods of setting up a data directory for a
new instance:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
Create a new data directory.
</p>
</li>
<li class="listitem">
<p>
Copy an existing data directory.
</p>
</li>
</ul>
</div>
<p>
The following discussion provides more detail about each method.
</p>
<div class="warning" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Warning
</div>
<p>
Normally, you should never have two servers that update data in
the same databases. This may lead to unpleasant surprises if
your operating system does not support fault-free system
locking. If (despite this warning) you run multiple servers
using the same data directory and they have logging enabled, you
must use the appropriate options to specify log file names that
are unique to each server. Otherwise, the servers try to log to
the same files.
</p>
<p>
Even when the preceding precautions are observed, this kind of
setup works only with
<code class="literal">
MyISAM
</code>
and
<code class="literal">
MERGE
</code>
tables, and not with any of the other
storage engines. Also, this warning against sharing a data
directory among servers always applies in an NFS environment.
Permitting multiple MySQL servers to access a common data
directory over NFS is a
<span class="emphasis">
<em>
very bad idea
</em>
</span>
. The
primary problem is that NFS is the speed bottleneck. It is not
meant for such use. Another risk with NFS is that you must
devise a way to ensure that two or more servers do not interfere
with each other. Usually NFS file locking is handled by the
<code class="literal">
lockd
</code>
daemon, but at the moment there is no
platform that performs locking 100% reliably in every situation.
</p>
</div>
<h4>
<a name="idm46045254065072">
</a>
Create a New Data Directory
</h4>
<p>
With this method, the data directory is in the same state as when
you first install MySQL, and has the default set of MySQL accounts
and no user data.
</p>
<p>
On Unix, initialize the data directory. See
<a class="xref" href="postinstallation.html" title="2.9 Postinstallation Setup and Testing">
Section 2.9, “Postinstallation Setup and Testing”
</a>
.
</p>
<p>
On Windows, the data directory is included in the MySQL
distribution:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
MySQL Zip archive distributions for Windows contain an
unmodified data directory. You can unpack such a distribution
into a temporary location, then copy it
<code class="filename">
data
</code>
directory to where you are setting
up the new instance.
</p>
</li>
<li class="listitem">
<p>
Windows MSI package installers create and set up the data
directory that the installed server uses, but also create a
pristine
<span class="quote">
“
<span class="quote">
template
</span>
”
</span>
data directory named
<code class="filename">
data
</code>
under the installation directory.
After an installation has been performed using an MSI package,
the template data directory can be copied to set up additional
MySQL instances.
</p>
</li>
</ul>
</div>
<h4>
<a name="idm46045254057680">
</a>
Copy an Existing Data Directory
</h4>
<a class="indexterm" name="idm46045254056960">
</a>
<p>
With this method, any MySQL accounts or user data present in the
data directory are carried over to the new data directory.
</p>
<div class="orderedlist">
<ol class="orderedlist" type="1">
<li class="listitem">
<p>
Stop the existing MySQL instance using the data directory.
This must be a clean shutdown so that the instance flushes any
pending changes to disk.
</p>
</li>
<li class="listitem">
<p>
Copy the data directory to the location where the new data
directory should be.
</p>
</li>
<li class="listitem">
<p>
Copy the
<code class="filename">
my.cnf
</code>
or
<code class="filename">
my.ini
</code>
option file used by the existing
instance. This serves as a basis for the new instance.
</p>
</li>
<li class="listitem">
<p>
Modify the new option file so that any pathnames referring to
the original data directory refer to the new data directory.
Also, modify any other options that must be unique per
instance, such as the TCP/IP port number and the log files.
For a list of parameters that must be unique per instance, see
<a class="xref" href="multiple-servers.html" title="7.8 Running Multiple MySQL Instances on One Machine">
Section 7.8, “Running Multiple MySQL Instances on One Machine”
</a>
.
</p>
</li>
<li class="listitem">
<p>
Start the new instance, telling it to use the new option file.
</p>
</li>
</ol>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/full-table.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="full-table">
</a>
B.3.2.10 The table is full
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045054256960">
</a>
<p>
If a table-full error occurs, it may be that the disk is full
or that the table has reached its maximum size. The effective
maximum table size for MySQL databases is usually determined
by operating system constraints on file sizes, not by MySQL
internal limits. See
<a class="xref" href="table-size-limit.html" title="10.4.6 Limits on Table Size">
Section 10.4.6, “Limits on Table Size”
</a>
.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/repair-table-optimization.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="repair-table-optimization">
</a>
10.6.3 Optimizing REPAIR TABLE Statements
</h3>
</div>
</div>
</div>
<a class="indexterm" name="idm46045225699328">
</a>
<p>
<a class="link" href="repair-table.html" title="15.7.3.5 REPAIR TABLE Statement">
<code class="literal">
REPAIR TABLE
</code>
</a>
for
<code class="literal">
MyISAM
</code>
tables is similar to using
<a class="link" href="myisamchk.html" title="6.6.4 myisamchk — MyISAM Table-Maintenance Utility">
<span class="command">
<strong>
myisamchk
</strong>
</span>
</a>
for repair operations, and some of
the same performance optimizations apply:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<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>
has variables that control
memory allocation. You may be able to its improve
performance by setting these variables, as described in
<a class="xref" href="myisamchk-memory.html" title="6.6.4.6 myisamchk Memory Usage">
Section 6.6.4.6, “myisamchk Memory Usage”
</a>
.
</p>
</li>
<li class="listitem">
<p>
For
<a class="link" href="repair-table.html" title="15.7.3.5 REPAIR TABLE Statement">
<code class="literal">
REPAIR TABLE
</code>
</a>
, the same
principle applies, but because the repair is done by the
server, you set server system variables instead of
<a class="link" href="myisamchk.html" title="6.6.4 myisamchk — MyISAM Table-Maintenance Utility">
<span class="command">
<strong>
myisamchk
</strong>
</span>
</a>
variables. Also, in addition to
setting memory-allocation variables, increasing the
<a class="link" href="server-system-variables.html#sysvar_myisam_max_sort_file_size">
<code class="literal">
myisam_max_sort_file_size
</code>
</a>
system variable increases the likelihood that the repair
uses the faster filesort method and avoids the slower repair
by key cache method. Set the variable to the maximum file
size for your system, after checking to be sure that there
is enough free space to hold a copy of the table files. The
free space must be available in the file system containing
the original table files.
</p>
</li>
</ul>
</div>
<p>
Suppose that a
<a class="link" href="myisamchk.html" title="6.6.4 myisamchk — MyISAM Table-Maintenance Utility">
<span class="command">
<strong>
myisamchk
</strong>
</span>
</a>
table-repair
operation is done using the following options to set its
memory-allocation variables:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-terminal"><div class="docs-select-all right" id="sa83959236"><div class="copy-help left">Press ⌘+C to 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 constant">--key_buffer_size</span><span class="token attr-value"><span class="token punctuation">=</span>128M</span> <span class="token constant">--myisam_sort_buffer_size</span><span class="token attr-value"><span class="token punctuation">=</span>256M</span>
<span class="token constant">--read_buffer_size</span><span class="token attr-value"><span class="token punctuation">=</span>64M</span> <span class="token constant">--write_buffer_size</span><span class="token attr-value"><span class="token punctuation">=</span>64M</span></code></pre>
</div>
<p>
Some of those
<a class="link" href="myisamchk.html" title="6.6.4 myisamchk — MyISAM Table-Maintenance Utility">
<span class="command">
<strong>
myisamchk
</strong>
</span>
</a>
variables correspond
to server system variables:
</p>
<div class="informaltable">
<table summary="myisamchk variables and corresponding server system variables.">
<colgroup>
<col style="width: 50%"/>
<col style="width: 50%"/>
</colgroup>
<thead>
<tr>
<th>
<a class="link" href="myisamchk.html" title="6.6.4 myisamchk — MyISAM Table-Maintenance Utility">
<span class="command">
<strong>
myisamchk
</strong>
</span>
</a>
Variable
</th>
<th>
System Variable
</th>
</tr>
</thead>
<tbody>
<tr>
<td>
<code class="literal">
key_buffer_size
</code>
</td>
<td>
<a class="link" href="server-system-variables.html#sysvar_key_buffer_size">
<code class="literal">
key_buffer_size
</code>
</a>
</td>
</tr>
<tr>
<td>
<code class="literal">
myisam_sort_buffer_size
</code>
</td>
<td>
<a class="link" href="server-system-variables.html#sysvar_myisam_sort_buffer_size">
<code class="literal">
myisam_sort_buffer_size
</code>
</a>
</td>
</tr>
<tr>
<td>
<code class="literal">
read_buffer_size
</code>
</td>
<td>
<a class="link" href="server-system-variables.html#sysvar_read_buffer_size">
<code class="literal">
read_buffer_size
</code>
</a>
</td>
</tr>
<tr>
<td>
<code class="literal">
write_buffer_size
</code>
</td>
<td>
none
</td>
</tr>
</tbody>
</table>
</div>
<p>
Each of the server system variables can be set at runtime, and
some of them
(
<a class="link" href="server-system-variables.html#sysvar_myisam_sort_buffer_size">
<code class="literal">
myisam_sort_buffer_size
</code>
</a>
,
<a class="link" href="server-system-variables.html#sysvar_read_buffer_size">
<code class="literal">
read_buffer_size
</code>
</a>
) have a
session value in addition to a global value. Setting a session
value limits the effect of the change to your current session
and does not affect other users. Changing a global-only variable
(
<a class="link" href="server-system-variables.html#sysvar_key_buffer_size">
<code class="literal">
key_buffer_size
</code>
</a>
,
<a class="link" href="server-system-variables.html#sysvar_myisam_max_sort_file_size">
<code class="literal">
myisam_max_sort_file_size
</code>
</a>
)
affects other users as well. For
<a class="link" href="server-system-variables.html#sysvar_key_buffer_size">
<code class="literal">
key_buffer_size
</code>
</a>
, you must take
into account that the buffer is shared with those users. For
example, if you set the
<a class="link" href="myisamchk.html" title="6.6.4 myisamchk — MyISAM Table-Maintenance Utility">
<span class="command">
<strong>
myisamchk
</strong>
</span>
</a>
<code class="literal">
key_buffer_size
</code>
variable to 128MB, you could
set the corresponding
<a class="link" href="server-system-variables.html#sysvar_key_buffer_size">
<code class="literal">
key_buffer_size
</code>
</a>
system variable
larger than that (if it is not already set larger), to permit
key buffer use by activity in other sessions. However, changing
the global key buffer size invalidates the buffer, causing
increased disk I/O and slowdown for other sessions. An
alternative that avoids this problem is to use a separate key
cache, assign to it the indexes from the table to be repaired,
and deallocate it when the repair is complete. See
<a class="xref" href="multiple-key-caches.html" title="10.10.2.2 Multiple Key Caches">
Section 10.10.2.2, “Multiple Key Caches”
</a>
.
</p>
<p>
Based on the preceding remarks, a
<a class="link" href="repair-table.html" title="15.7.3.5 REPAIR TABLE Statement">
<code class="literal">
REPAIR
TABLE
</code>
</a>
operation can be done as follows to use settings
similar to 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. Here a
separate 128MB key buffer is allocated and the file system is
assumed to permit a file size of at least 100GB.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa89771036"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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> myisam_sort_buffer_size <span class="token operator">=</span> <span class="token number">256</span><span class="token operator">*</span><span class="token number">1024</span><span class="token operator">*</span><span class="token number">1024</span><span class="token punctuation">;</span>
<span class="token keyword">SET</span> <span class="token keyword">SESSION</span> read_buffer_size <span class="token operator">=</span> <span class="token number">64</span><span class="token operator">*</span><span class="token number">1024</span><span class="token operator">*</span><span class="token number">1024</span><span class="token punctuation">;</span>
<span class="token keyword">SET</span> <span class="token keyword">GLOBAL</span> myisam_max_sort_file_size <span class="token operator">=</span> <span class="token number">100</span><span class="token operator">*</span><span class="token number">1024</span><span class="token operator">*</span><span class="token number">1024</span><span class="token operator">*</span><span class="token number">1024</span><span class="token punctuation">;</span>
<span class="token keyword">SET</span> <span class="token keyword">GLOBAL</span> repair_cache<span class="token punctuation">.</span>key_buffer_size <span class="token operator">=</span> <span class="token number">128</span><span class="token operator">*</span><span class="token number">1024</span><span class="token operator">*</span><span class="token number">1024</span><span class="token punctuation">;</span>
<span class="token keyword">CACHE</span> <span class="token keyword">INDEX</span> <em class="replaceable">tbl_name</em> <span class="token keyword">IN</span> repair_cache<span class="token punctuation">;</span>
<span class="token keyword">LOAD</span> <span class="token keyword">INDEX</span> <span class="token keyword">INTO</span> <span class="token keyword">CACHE</span> <em class="replaceable">tbl_name</em><span class="token punctuation">;</span>
<span class="token keyword">REPAIR</span> <span class="token keyword">TABLE</span> <em class="replaceable">tbl_name</em> <span class="token punctuation">;</span>
<span class="token keyword">SET</span> <span class="token keyword">GLOBAL</span> repair_cache<span class="token punctuation">.</span>key_buffer_size <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
If you intend to change a global variable but want to do so only
for the duration of a
<a class="link" href="repair-table.html" title="15.7.3.5 REPAIR TABLE Statement">
<code class="literal">
REPAIR
TABLE
</code>
</a>
operation to minimally affect other users, save
its value in a user variable and restore it afterward. For
example:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa72544093"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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">@old_myisam_sort_buffer_size</span> <span class="token operator">=</span> <span class="token variable">@@GLOBAL.myisam_max_sort_file_size</span><span class="token punctuation">;</span>
<span class="token keyword">SET</span> <span class="token keyword">GLOBAL</span> myisam_max_sort_file_size <span class="token operator">=</span> <span class="token number">100</span><span class="token operator">*</span><span class="token number">1024</span><span class="token operator">*</span><span class="token number">1024</span><span class="token operator">*</span><span class="token number">1024</span><span class="token punctuation">;</span>
<span class="token keyword">REPAIR</span> <span class="token keyword">TABLE</span> tbl_name <span class="token punctuation">;</span>
<span class="token keyword">SET</span> <span class="token keyword">GLOBAL</span> myisam_max_sort_file_size <span class="token operator">=</span> <span class="token variable">@old_myisam_max_sort_file_size</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
The system variables that affect
<a class="link" href="repair-table.html" title="15.7.3.5 REPAIR TABLE Statement">
<code class="literal">
REPAIR
TABLE
</code>
</a>
can be set globally at server startup if you
want the values to be in effect by default. For example, add
these lines to the server
<code class="filename">
my.cnf
</code>
file:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-ini"><div class="docs-select-all right" id="sa4239659"><div class="copy-help left">Press ⌘+C to 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">myisam_sort_buffer_size</span><span class="token attr-value"><span class="token punctuation">=</span>256M</span>
<span class="token constant">key_buffer_size</span><span class="token attr-value"><span class="token punctuation">=</span>1G</span>
<span class="token constant">myisam_max_sort_file_size</span><span class="token attr-value"><span class="token punctuation">=</span>100G</span></code></pre>
</div>
<p>
These settings do not include
<a class="link" href="server-system-variables.html#sysvar_read_buffer_size">
<code class="literal">
read_buffer_size
</code>
</a>
. Setting
<a class="link" href="server-system-variables.html#sysvar_read_buffer_size">
<code class="literal">
read_buffer_size
</code>
</a>
globally to a
large value does so for all sessions and can cause performance
to suffer due to excessive memory allocation for a server with
many simultaneous sessions.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/mysql-cluster-ndbinfo-tc-time-track-stats.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="mysql-cluster-ndbinfo-tc-time-track-stats">
</a>
25.6.17.61 The ndbinfo tc_time_track_stats Table
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045087627024">
</a>
<p>
The
<code class="literal">
tc_time_track_stats
</code>
table provides
time-tracking information obtained from the
<a class="ulink" href="/doc/ndb-internals/en/ndb-internals-kernel-blocks-dbtc.html" target="_top">
<code class="literal">
DBTC
</code>
</a>
block (TC) instances in
the data nodes, through API nodes access
<code class="literal">
NDB
</code>
.
Each TC instance tracks latencies for a set of activities it
undertakes on behalf of API nodes or other data nodes; these
activities include transactions, transaction errors, key reads,
key writes, unique index operations, failed key operations of
any type, scans, failed scans, fragment scans, and failed
fragment scans.
</p>
<p>
A set of counters is maintained for each activity, each counter
covering a range of latencies less than or equal to an upper
bound. At the conclusion of each activity, its latency is
determined and the appropriate counter incremented.
<code class="literal">
tc_time_track_stats
</code>
presents this information
as rows, with a row for each instance of the following:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
Data node, using its ID
</p>
</li>
<li class="listitem">
<p>
TC block instance
</p>
</li>
<li class="listitem">
<p>
Other communicating data node or API node, using its ID
</p>
</li>
<li class="listitem">
<p>
Upper bound value
</p>
</li>
</ul>
</div>
<p>
Each row contains a value for each activity type. This is the
number of times that this activity occurred with a latency
within the range specified by the row (that is, where the
latency does not exceed the upper bound).
</p>
<p>
The
<code class="literal">
tc_time_track_stats
</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">
node_id
</code>
</p>
<p>
Requesting node ID
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
block_number
</code>
</p>
<p>
TC block number
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
block_instance
</code>
</p>
<p>
TC block instance number
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
comm_node_id
</code>
</p>
<p>
Node ID of communicating API or data node
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
upper_bound
</code>
</p>
<p>
Upper bound of interval (in microseconds)
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
scans
</code>
</p>
<p>
Based on duration of successful scans from opening to
closing, tracked against the API or data nodes requesting
them.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
scan_errors
</code>
</p>
<p>
Based on duration of failed scans from opening to closing,
tracked against the API or data nodes requesting them.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
scan_fragments
</code>
</p>
<p>
Based on duration of successful fragment scans from opening
to closing, tracked against the data nodes executing them
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
scan_fragment_errors
</code>
</p>
<p>
Based on duration of failed fragment scans from opening to
closing, tracked against the data nodes executing them
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
transactions
</code>
</p>
<p>
Based on duration of successful transactions from beginning
until sending of commit
<code class="literal">
ACK
</code>
, tracked
against the API or data nodes requesting them. Stateless
transactions are not included.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
transaction_errors
</code>
</p>
<p>
Based on duration of failing transactions from start to
point of failure, tracked against the API or data nodes
requesting them.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
read_key_ops
</code>
</p>
<p>
Based on duration of successful primary key reads with
locks. Tracked against both the API or data node requesting
them and the data node executing them.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
write_key_ops
</code>
</p>
<p>
Based on duration of successful primary key writes, tracked
against both the API or data node requesting them and the
data node executing them.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
index_key_ops
</code>
</p>
<p>
Based on duration of successful unique index key operations,
tracked against both the API or data node requesting them
and the data node executing reads of base tables.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
key_op_errors
</code>
</p>
<p>
Based on duration of all unsuccessful key read or write
operations, tracked against both the API or data node
requesting them and the data node executing them.
</p>
</li>
</ul>
</div>
<h5>
<a name="idm46045087584000">
</a>
Notes
</h5>
<p>
The
<code class="literal">
block_instance
</code>
column provides the
<a class="ulink" href="/doc/ndb-internals/en/ndb-internals-kernel-blocks-dbtc.html" target="_top">
<code class="literal">
DBTC
</code>
</a>
kernel block instance
number. You can use this together with the block name to obtain
information about specific threads from the
<a class="link" href="mysql-cluster-ndbinfo-threadblocks.html" title="25.6.17.62 The ndbinfo threadblocks Table">
<code class="literal">
threadblocks
</code>
</a>
table.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/precision-math-decimal-characteristics.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="precision-math-decimal-characteristics">
</a>
14.24.2 DECIMAL Data Type Characteristics
</h3>
</div>
</div>
</div>
<p>
This section discusses the characteristics of the
<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>
data type (and its
synonyms), with particular regard to the following topics:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
Maximum number of digits
</p>
</li>
<li class="listitem">
<p>
Storage format
</p>
</li>
<li class="listitem">
<p>
Storage requirements
</p>
</li>
<li class="listitem">
<p>
The nonstandard MySQL extension to the upper range of
<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>
columns
</p>
</li>
</ul>
</div>
<p>
The declaration syntax for a
<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>
column is
<code class="literal">
DECIMAL(
<em class="replaceable">
<code>
M
</code>
</em>
,
<em class="replaceable">
<code>
D
</code>
</em>
)
</code>
.
The ranges of values for the arguments are as follows:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<em class="replaceable">
<code>
M
</code>
</em>
is the maximum number of digits
(the precision). It has a range of 1 to 65.
</p>
</li>
<li class="listitem">
<p>
<em class="replaceable">
<code>
D
</code>
</em>
is the number of digits to the
right of the decimal point (the scale). It has a range of 0 to
30 and must be no larger than
<em class="replaceable">
<code>
M
</code>
</em>
.
</p>
</li>
</ul>
</div>
<p>
If
<em class="replaceable">
<code>
D
</code>
</em>
is omitted, the default is 0. If
<em class="replaceable">
<code>
M
</code>
</em>
is omitted, the default is 10.
</p>
<p>
The maximum value of 65 for
<em class="replaceable">
<code>
M
</code>
</em>
means
that calculations on
<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>
values
are accurate up to 65 digits. This limit of 65 digits of precision
also applies to exact-value numeric literals, so the maximum range
of such literals differs from before. (There is also a limit on
how long the text of
<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>
literals can be; see
<a class="xref" href="precision-math-expressions.html" title="14.24.3 Expression Handling">
Section 14.24.3, “Expression Handling”
</a>
.)
</p>
<p>
Values for
<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>
columns are
stored using a binary format that packs nine decimal digits into 4
bytes. The storage requirements for the integer and fractional
parts of each value are determined separately. Each multiple of
nine digits requires 4 bytes, and any remaining digits left over
require some fraction of 4 bytes. The storage required for
remaining digits is given by the following table.
</p>
<div class="informaltable">
<table summary="The number of bytes required for remaining/leftover digits in DECIMAL values.">
<colgroup>
<col style="width: 25%"/>
<col style="width: 25%"/>
</colgroup>
<thead>
<tr>
<th>
Leftover Digits
</th>
<th>
Number of Bytes
</th>
</tr>
</thead>
<tbody>
<tr>
<td>
0
</td>
<td>
0
</td>
</tr>
<tr>
<td>
1–2
</td>
<td>
1
</td>
</tr>
<tr>
<td>
3–4
</td>
<td>
2
</td>
</tr>
<tr>
<td>
5–6
</td>
<td>
3
</td>
</tr>
<tr>
<td>
7–9
</td>
<td>
4
</td>
</tr>
</tbody>
</table>
</div>
<p>
For example, a
<code class="literal">
DECIMAL(18,9)
</code>
column has nine
digits on either side of the decimal point, so the integer part
and the fractional part each require 4 bytes. A
<code class="literal">
DECIMAL(20,6)
</code>
column has fourteen integer
digits and six fractional digits. The integer digits require four
bytes for nine of the digits and 3 bytes for the remaining five
digits. The six fractional digits require 3 bytes.
</p>
<p>
<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>
columns do not store a
leading
<code class="literal">
+
</code>
character or
<code class="literal">
-
</code>
character or leading
<code class="literal">
0
</code>
digits. If you insert
<code class="literal">
+0003.1
</code>
into a
<code class="literal">
DECIMAL(5,1)
</code>
column, it is stored as
<code class="literal">
3.1
</code>
. For negative
numbers, a literal
<code class="literal">
-
</code>
character is not stored.
</p>
<p>
<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>
columns do not permit
values larger than the range implied by the column definition. For
example, a
<code class="literal">
DECIMAL(3,0)
</code>
column supports a range
of
<code class="literal">
-999
</code>
to
<code class="literal">
999
</code>
. A
<code class="literal">
DECIMAL(
<em class="replaceable">
<code>
M
</code>
</em>
,
<em class="replaceable">
<code>
D
</code>
</em>
)
</code>
column permits up to
<em class="replaceable">
<code>
M
</code>
</em>
-
<em class="replaceable">
<code>
D
</code>
</em>
digits to the left of the decimal
point.
</p>
<p>
The SQL standard requires that the precision of
<code class="literal">
NUMERIC(
<em class="replaceable">
<code>
M
</code>
</em>
,
<em class="replaceable">
<code>
D
</code>
</em>
)
</code>
be
<span class="emphasis">
<em>
exactly
</em>
</span>
<em class="replaceable">
<code>
M
</code>
</em>
digits. For
<code class="literal">
DECIMAL(
<em class="replaceable">
<code>
M
</code>
</em>
,
<em class="replaceable">
<code>
D
</code>
</em>
)
</code>
,
the standard requires a precision of at least
<em class="replaceable">
<code>
M
</code>
</em>
digits but permits more. In MySQL,
<code class="literal">
DECIMAL(
<em class="replaceable">
<code>
M
</code>
</em>
,
<em class="replaceable">
<code>
D
</code>
</em>
)
</code>
and
<code class="literal">
NUMERIC(
<em class="replaceable">
<code>
M
</code>
</em>
,
<em class="replaceable">
<code>
D
</code>
</em>
)
</code>
are the same, and both have a precision of exactly
<em class="replaceable">
<code>
M
</code>
</em>
digits.
</p>
<p>
For a full explanation of the internal format of
<code class="literal">
DECIMAL
</code>
values, see the file
<code class="filename">
strings/decimal.c
</code>
in a MySQL source
distribution. The format is explained (with an example) in the
<code class="literal">
decimal2bin()
</code>
function.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/mysql-cluster-replication-backups.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="mysql-cluster-replication-backups">
</a>
25.7.9 NDB Cluster Backups With NDB Cluster Replication
</h3>
</div>
</div>
</div>
<div class="toc">
<dl class="toc">
<dt>
<span class="section">
<a href="mysql-cluster-replication-auto-sync.html">
25.7.9.1 NDB Cluster Replication: Automating Synchronization of the Replica to
the Source Binary Log
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-replication-pitr.html">
25.7.9.2 Point-In-Time Recovery Using NDB Cluster Replication
</a>
</span>
</dt>
</dl>
</div>
<a class="indexterm" name="idm46045085937456">
</a>
<a class="indexterm" name="idm46045085935968">
</a>
<a class="indexterm" name="idm46045085934512">
</a>
<a class="indexterm" name="idm46045085933024">
</a>
<p>
This section discusses making backups and restoring from them
using NDB Cluster replication. We assume that the replication
servers have already been configured as covered previously (see
<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 the
sections immediately following). This having been done, the
procedure for making a backup and then restoring from it is as
follows:
</p>
<div class="orderedlist">
<ol class="orderedlist" type="1">
<li class="listitem">
<p>
There are two different methods by which the backup may be
started.
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<b>
Method A.
</b>
This method requires that the cluster backup process was
previously enabled on the source server, prior to
starting the replication process. This can be done by
including the following line in a
<code class="literal">
[mysql_cluster]
</code>
section in the
<code class="filename">
my.cnf file
</code>
, where
<em class="replaceable">
<code>
management_host
</code>
</em>
is the IP
address or host name of the
<a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4">
<code class="literal">
NDB
</code>
</a>
management server for
the source cluster, and
<em class="replaceable">
<code>
port
</code>
</em>
is the management server's port number:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-ini"><div class="docs-select-all right" id="sa4031905"><div class="copy-help left">Press ⌘+C to 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 constant">ndb-connectstring</span><span class="token attr-value"><span class="token punctuation">=</span><em class="replaceable">management_host</em>[:<em class="replaceable">port</em>]</span></code></pre>
</div>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
The port number needs to be specified only if the
default port (1186) is not being used. See
<a class="xref" href="mysql-cluster-install-configuration.html" title="25.3.3 Initial Configuration of NDB Cluster">
Section 25.3.3, “Initial Configuration of NDB Cluster”
</a>
,
for more information about ports and port allocation in
NDB Cluster.
</p>
</div>
<p>
<a class="indexterm" name="idm46045085918896">
</a>
In this case, the backup can be started by executing this
statement on the replication source:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-terminal"><div class="docs-select-all right" id="sa97943730"><div class="copy-help left">Press ⌘+C to 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">shell<em class="replaceable">S</em>></span><span class="token command"> ndb_mgm</span> <span class="token property">-e</span> <span class="token atrule">"START BACKUP"</span></code></pre>
</div>
</li>
<li class="listitem">
<p>
<b>
Method B.
</b>
If the
<code class="filename">
my.cnf
</code>
file does not specify
where to find the management host, you can start the
backup process by passing this information to the
<a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4">
<code class="literal">
NDB
</code>
</a>
management client as
part of 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. This can be done as shown
here, where
<em class="replaceable">
<code>
management_host
</code>
</em>
and
<em class="replaceable">
<code>
port
</code>
</em>
are the host name
and port number of the management server:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-terminal"><div class="docs-select-all right" id="sa12062299"><div class="copy-help left">Press ⌘+C to 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">shell<em class="replaceable">S</em>></span><span class="token command"> ndb_mgm</span> <em class="replaceable">management_host</em><span class="token punctuation">:</span><em class="replaceable">port</em> <span class="token property">-e</span> <span class="token atrule">"START BACKUP"</span></code></pre>
</div>
<p>
In our scenario as outlined earlier (see
<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>
),
this would be executed as follows:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-terminal"><div class="docs-select-all right" id="sa2125942"><div class="copy-help left">Press ⌘+C to 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">shell<em class="replaceable">S</em>></span><span class="token command"> ndb_mgm</span> rep-source<span class="token punctuation">:</span>1186 <span class="token property">-e</span> <span class="token atrule">"START BACKUP"</span></code></pre>
</div>
</li>
</ul>
</div>
</li>
<li class="listitem">
<p>
Copy the cluster backup files to the replica that is being
brought on line. Each system running an
<a class="link" href="mysql-cluster-programs-ndbd.html" title="25.5.1 ndbd — The NDB Cluster Data Node Daemon">
<span class="command">
<strong>
ndbd
</strong>
</span>
</a>
process for the source cluster has
cluster backup files located on it, and
<span class="emphasis">
<em>
all
</em>
</span>
of these files must be copied to the
replica to ensure a successful restore. The backup files can
be copied into any directory on the computer where the
replica's management host resides, as long as the MySQL
and NDB binaries have read permissions in that directory. In
this case, we assume that these files have been copied into
the directory
<code class="filename">
/var/BACKUPS/BACKUP-1
</code>
.
</p>
<p>
While it is not necessary that the replica cluster have the
same number of data nodes as the source, it is highly
recommended this number be the same. It
<span class="emphasis">
<em>
is
</em>
</span>
necessary that the replication process
is prevented from starting when the replica server starts. You
can do this by starting the replica with
<a class="link" href="replication-options-replica.html#option_mysqld_skip-replica-start">
<code class="option">
--skip-replica-start
</code>
</a>
.
</p>
</li>
<li class="listitem">
<p>
Create any databases on the replica cluster that are present
on the source cluster and that are to be replicated.
</p>
<div class="important" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Important
</div>
<p>
A
<a class="link" href="create-database.html" title="15.1.12 CREATE DATABASE Statement">
<code class="literal">
CREATE DATABASE
</code>
</a>
(or
<a class="link" href="create-database.html" title="15.1.12 CREATE DATABASE Statement">
<code class="literal">
CREATE
SCHEMA
</code>
</a>
) statement corresponding to each database
to be replicated must be executed on each SQL node in the
replica cluster.
</p>
</div>
</li>
<li class="listitem">
<p>
Reset the replica cluster using this statement 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>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa45676273"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql">mysql<em class="replaceable">R</em><span class="token operator">></span> <span class="token keyword">RESET</span> <span class="token keyword">REPLICA</span><span class="token punctuation">;</span></code></pre>
</div>
</li>
<li class="listitem">
<p>
You can now start the cluster restoration process on the
replica using the
<a class="link" href="mysql-cluster-programs-ndb-restore.html" title="25.5.23 ndb_restore — Restore an NDB Cluster Backup">
<span class="command">
<strong>
ndb_restore
</strong>
</span>
</a>
command for
each backup file in turn. For the first of these, it is
necessary to include the
<code class="option">
-m
</code>
option to restore
the cluster metadata, as shown here:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-terminal"><div class="docs-select-all right" id="sa84625050"><div class="copy-help left">Press ⌘+C to 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">shell<em class="replaceable">R</em>> ndb_restore <span class="token property">-c</span> <em class="replaceable">replica_host</em><span class="token punctuation">:</span><em class="replaceable">port</em> <span class="token property">-n</span> <em class="replaceable">node-id</em> \
<span class="token property">-b</span> <em class="replaceable">backup-id</em> <span class="token property">-m</span> <span class="token property">-r</span> <em class="replaceable">dir</em></code></pre>
</div>
<p>
<em class="replaceable">
<code>
dir
</code>
</em>
is the path to the directory
where the backup files have been placed on the replica. For
the
<a class="link" href="mysql-cluster-programs-ndb-restore.html" title="25.5.23 ndb_restore — Restore an NDB Cluster Backup">
<span class="command">
<strong>
ndb_restore
</strong>
</span>
</a>
commands corresponding to
the remaining backup files, the
<code class="option">
-m
</code>
option
should
<span class="emphasis">
<em>
not
</em>
</span>
be used.
</p>
<p>
For restoring from a source cluster with four data nodes (as
shown in the figure in
<a class="xref" href="mysql-cluster-replication.html" title="25.7 NDB Cluster Replication">
Section 25.7, “NDB Cluster Replication”
</a>
) where the backup
files have been copied to the directory
<code class="filename">
/var/BACKUPS/BACKUP-1
</code>
, the proper
sequence of commands to be executed on the replica might look
like this:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-terminal"><div class="docs-select-all right" id="sa83908445"><div class="copy-help left">Press ⌘+C to 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">shell<em class="replaceable">R</em>> ndb_restore <span class="token property">-c</span> replica-host<span class="token punctuation">:</span>1186 <span class="token property">-n</span> 2 <span class="token property">-b</span> 1 <span class="token property">-m</span> \
<span class="token property">-r</span> <span class="token punctuation">.</span>/var/BACKUPS/BACKUP-1
shell<em class="replaceable">R</em>> ndb_restore <span class="token property">-c</span> replica-host<span class="token punctuation">:</span>1186 <span class="token property">-n</span> 3 <span class="token property">-b</span> 1 \
<span class="token property">-r</span> <span class="token punctuation">.</span>/var/BACKUPS/BACKUP-1
shell<em class="replaceable">R</em>> ndb_restore <span class="token property">-c</span> replica-host<span class="token punctuation">:</span>1186 <span class="token property">-n</span> 4 <span class="token property">-b</span> 1 \
<span class="token property">-r</span> <span class="token punctuation">.</span>/var/BACKUPS/BACKUP-1
shell<em class="replaceable">R</em>> ndb_restore <span class="token property">-c</span> replica-host<span class="token punctuation">:</span>1186 <span class="token property">-n</span> 5 <span class="token property">-b</span> 1 <span class="token property">-e</span> \
<span class="token property">-r</span> <span class="token punctuation">.</span>/var/BACKUPS/BACKUP-1</code></pre>
</div>
<div class="important" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Important
</div>
<p>
The
<code class="option">
-e
</code>
(or
<a class="link" href="mysql-cluster-programs-ndb-restore.html#option_ndb_restore_restore-epoch">
<code class="option">
--restore-epoch
</code>
</a>
) option
in the final invocation of
<a class="link" href="mysql-cluster-programs-ndb-restore.html" title="25.5.23 ndb_restore — Restore an NDB Cluster Backup">
<span class="command">
<strong>
ndb_restore
</strong>
</span>
</a>
in
this example is required to make sure that the epoch is
written to the replica's
<code class="literal">
mysql.ndb_apply_status
</code>
table. Without
this information, the replica cannot synchronize properly
with the source. (See
<a class="xref" href="mysql-cluster-programs-ndb-restore.html" title="25.5.23 ndb_restore — Restore an NDB Cluster Backup">
Section 25.5.23, “ndb_restore — Restore an NDB Cluster Backup”
</a>
.)
</p>
</div>
</li>
<li class="listitem">
<p>
Now you need to obtain the most recent epoch from the
<code class="literal">
ndb_apply_status
</code>
table on the replica (as
discussed in
<a class="xref" href="mysql-cluster-replication-failover.html" title="25.7.8 Implementing Failover with NDB Cluster Replication">
Section 25.7.8, “Implementing Failover with NDB Cluster Replication”
</a>
):
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa93077241"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql">mysql<em class="replaceable">R</em><span class="token operator">></span> <span class="token keyword">SELECT</span> <span class="token variable">@latest</span><span class="token operator">:=</span><span class="token function">MAX</span><span class="token punctuation">(</span>epoch<span class="token punctuation">)</span>
<span class="token keyword">FROM</span> mysql<span class="token punctuation">.</span>ndb_apply_status<span class="token punctuation">;</span></code></pre>
</div>
</li>
<li class="listitem">
<p>
Using
<code class="literal">
@latest
</code>
as the epoch value obtained
in the previous step, you can obtain the correct starting
position
<code class="literal">
@pos
</code>
in the correct binary log
file
<code class="literal">
@file
</code>
from the
<code class="literal">
mysql.ndb_binlog_index
</code>
table on the source.
The query shown here gets these from the
<code class="literal">
Position
</code>
and
<code class="literal">
File
</code>
columns from the last epoch applied before the logical restore
position:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa30028766"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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<em class="replaceable">S</em>></span> <span class="token keyword">SELECT</span>
<span class="token prompt"> -></span> <span class="token variable">@file</span><span class="token operator">:=</span><span class="token function">SUBSTRING_INDEX</span><span class="token punctuation">(</span><span class="token keyword">File</span><span class="token punctuation">,</span> <span class="token string">'/'</span><span class="token punctuation">,</span> <span class="token operator">-</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 variable">@pos</span><span class="token operator">:=</span>Position
<span class="token prompt"> -></span> <span class="token keyword">FROM</span> mysql<span class="token punctuation">.</span>ndb_binlog_index
<span class="token prompt"> -></span> <span class="token keyword">WHERE</span> epoch <span class="token operator">></span> <span class="token variable">@latest</span>
<span class="token prompt"> -></span> <span class="token keyword">ORDER</span> <span class="token keyword">BY</span> epoch <span class="token keyword">ASC</span> <span class="token keyword">LIMIT</span> <span class="token number">1</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
In the event that there is currently no replication traffic,
you can get similar information by running
<a class="link" href="show-binary-log-status.html" title="15.7.7.1 SHOW BINARY LOG STATUS Statement">
<code class="literal">
SHOW BINARY LOG STATUS
</code>
</a>
on the
source and using the value shown in the
<code class="literal">
Position
</code>
column of the output for the file
whose name has the suffix with the greatest value for all
files shown in the
<code class="literal">
File
</code>
column. In this
case, you must determine which file this is and supply the
name in the next step manually or by parsing the output with a
script.
</p>
</li>
<li class="listitem">
<p>
Using the values obtained in the previous step, you can now
issue the appropriate in the replica's
<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. Use the following
<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:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa38868556"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql">mysql<em class="replaceable">R</em><span class="token operator">></span> <span class="token keyword">CHANGE</span> <span class="token keyword">REPLICATION</span> <span class="token keyword">SOURCE</span> <span class="token keyword">TO</span>
<span class="token prompt"> -></span> <span class="token keyword">SOURCE_LOG_FILE</span><span class="token operator">=</span><span class="token string">'@file'</span><span class="token punctuation">,</span>
<span class="token prompt"> -></span> <span class="token keyword">SOURCE_LOG_POS</span><span class="token operator">=</span><span class="token variable">@pos</span><span class="token punctuation">;</span></code></pre>
</div>
</li>
<li class="listitem">
<p>
Now that the replica knows from what point in which binary log
file to start reading data from the source, you can cause the
replica to begin replicating with this statement:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa53425857"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql">mysql<em class="replaceable">R</em><span class="token operator">></span> <span class="token keyword">START</span> <span class="token keyword">REPLICA</span><span class="token punctuation">;</span></code></pre>
</div>
</li>
</ol>
</div>
<p>
To perform a backup and restore on a second replication channel,
it is necessary only to repeat these steps, substituting the host
names and IDs of the secondary source and replica for those of the
primary source and replica servers where appropriate, and running
the preceding statements on them.
</p>
<p>
For additional information on performing Cluster backups and
restoring Cluster from backups, see
<a class="xref" href="mysql-cluster-backup.html" title="25.6.8 Online Backup of NDB Cluster">
Section 25.6.8, “Online Backup of NDB Cluster”
</a>
.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/replication-multi-source-configuration.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="replication-multi-source-configuration">
</a>
19.1.5.1 Configuring Multi-Source Replication
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045145309984">
</a>
<p>
A multi-source replication topology requires at least two sources
and one replica configured. In these tutorials, we assume that you
have two sources
<code class="literal">
source1
</code>
and
<code class="literal">
source2
</code>
, and a replica
<code class="literal">
replicahost
</code>
. The replica replicates one
database from each of the sources,
<code class="literal">
db1
</code>
from
<code class="literal">
source1
</code>
and
<code class="literal">
db2
</code>
from
<code class="literal">
source2
</code>
.
</p>
<p>
Sources in a multi-source replication topology can be configured
to use either GTID-based replication, or binary log position-based
replication. See
<a class="xref" href="replication-gtids-howto.html" title="19.1.3.4 Setting Up Replication Using GTIDs">
Section 19.1.3.4, “Setting Up Replication Using GTIDs”
</a>
for how
to configure a source using GTID-based replication. See
<a class="xref" href="replication-howto-masterbaseconfig.html" title="19.1.2.1 Setting the Replication Source Configuration">
Section 19.1.2.1, “Setting the Replication Source Configuration”
</a>
for how to
configure a source using file position based replication.
</p>
<p>
Replicas in a multi-source replication topology require
<code class="literal">
TABLE
</code>
repositories for the replica's connection
metadata repository and applier metadata repository, which are the
default in MySQL 8.4. Multi-source replication is not
compatible with the deprecated alternative file repositories.
</p>
<p>
Create a suitable user account on all the sources that the replica
can use to connect. You can use the same account on all the
sources, or a different account on each. If you create an account
solely for the purposes of replication, that account needs only
the
<a class="link" href="privileges-provided.html#priv_replication-slave">
<code class="literal">
REPLICATION SLAVE
</code>
</a>
privilege.
For example, to set up a new user,
<code class="literal">
ted
</code>
, that
can connect from the replica
<code class="literal">
replicahost
</code>
, use
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 to issue these statements on
each of the sources:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa42733034"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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">USER</span> <span class="token string">'ted'</span>@<span class="token string">'replicahost'</span> <span class="token keyword">IDENTIFIED</span> <span class="token keyword">BY</span> <span class="token string">'<em class="replaceable">password</em>'</span><span class="token punctuation">;</span>
<span class="token prompt">mysql></span> <span class="token keyword">GRANT</span> <span class="token keyword">REPLICATION</span> <span class="token keyword">SLAVE</span> <span class="token keyword">ON</span> <span class="token operator">*</span><span class="token punctuation">.</span><span class="token operator">*</span> <span class="token keyword">TO</span> <span class="token string">'ted'</span>@<span class="token string">'replicahost'</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
For more information about the default authentication plugin for
new users, see
<a class="xref" href="replication-howto-repuser.html" title="19.1.2.3 Creating a User for Replication">
Section 19.1.2.3, “Creating a User for Replication”
</a>
.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/selinux-context-mysql-feature-ports.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="selinux-context-mysql-feature-ports">
</a>
8.7.5.2 Setting the TCP Port Context for MySQL Features
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045231541200">
</a>
<p>
If you enable certain MySQL features, you might need to set the
SELinux TCP port context for additional ports used by those
features. If ports used by MySQL features do not have the
correct SELinux context, the features might not function
correctly.
</p>
<p>
The following sections describe how to set port contexts for
MySQL features. Generally, the same method can be used to set
the port context for any MySQL features. For information about
ports used by MySQL features, refer to the
<a class="ulink" href="/doc/mysql-port-reference/en/" target="_top">
MySQL Port Reference
</a>
.
</p>
<p>
For MySQL 8.4, enabling
<code class="literal">
mysql_connect_any
</code>
is not required or
recommended.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-simple"><div class="docs-select-all right" id="sa67682942"><div class="copy-help left">Press ⌘+C to 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">setsebool <span class="token operator">-</span>P mysql_connect_any<span class="token operator">=</span>ON</code></pre>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h5 class="title">
<a name="selinux-context-group-replication-port">
</a>
Setting the TCP Port Context for Group Replication
</h5>
</div>
</div>
</div>
<a class="indexterm" name="idm46045231533504">
</a>
<p>
If SELinux is enabled, you must set the port context for the
Group Replication communication port, which is defined by the
<a class="link" href="group-replication-system-variables.html#sysvar_group_replication_local_address">
<code class="literal">
group_replication_local_address
</code>
</a>
variable.
<a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
<span class="command">
<strong>
mysqld
</strong>
</span>
</a>
must be able to bind to
the Group Replication communication port and listen there.
InnoDB Cluster relies on Group Replication so this applies
equally to instances used in a cluster. To view ports
currently used by MySQL, issue:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-simple"><div class="docs-select-all right" id="sa53826537"><div class="copy-help left">Press ⌘+C to 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">semanage port <span class="token operator">-</span>l <span class="token operator">|</span> grep mysqld</code></pre>
</div>
<p>
Assuming the Group Replication communication port is 33061,
set the port context by issuing:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-simple"><div class="docs-select-all right" id="sa74681659"><div class="copy-help left">Press ⌘+C to 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">semanage port <span class="token operator">-</span>a <span class="token operator">-</span>t mysqld_port_t <span class="token operator">-</span>p tcp 33061</code></pre>
</div>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h5 class="title">
<a name="selinux-context-document-store-ports">
</a>
Setting the TCP Port Context for Document Store
</h5>
</div>
</div>
</div>
<a class="indexterm" name="idm46045231524832">
</a>
<p>
If SELinux is enabled, you must set the port context for the
communication port used by X Plugin, which is defined by the
<a class="link" href="x-plugin-options-system-variables.html#sysvar_mysqlx_port">
<code class="literal">
mysqlx_port
</code>
</a>
variable.
<a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
<span class="command">
<strong>
mysqld
</strong>
</span>
</a>
must be able to bind to the
X Plugin communication port and listen there.
</p>
<p>
Assuming the X Plugin communication port is 33060, set the
port context by issuing:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-simple"><div class="docs-select-all right" id="sa91995107"><div class="copy-help left">Press ⌘+C to 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">semanage port <span class="token operator">-</span>a <span class="token operator">-</span>t mysqld_port_t <span class="token operator">-</span>p tcp 33060</code></pre>
</div>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h5 class="title">
<a name="selinux-context-router-ports">
</a>
Setting the TCP Port Context for MySQL Router
</h5>
</div>
</div>
</div>
<a class="indexterm" name="idm46045231517376">
</a>
<p>
If SELinux is enabled, you must set the port context for the
communication ports used by MySQL Router. Assuming the additional
communication ports used by MySQL Router are the default 6446,
6447, 64460 and 64470, on each instance set the port context
by issuing:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-simple"><div class="docs-select-all right" id="sa39843038"><div class="copy-help left">Press ⌘+C to 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">semanage port <span class="token operator">-</span>a <span class="token operator">-</span>t mysqld_port_t <span class="token operator">-</span>p tcp 6446
semanage port <span class="token operator">-</span>a <span class="token operator">-</span>t mysqld_port_t <span class="token operator">-</span>p tcp 6447
semanage port <span class="token operator">-</span>a <span class="token operator">-</span>t mysqld_port_t <span class="token operator">-</span>p tcp 64460
semanage port <span class="token operator">-</span>a <span class="token operator">-</span>t mysqld_port_t <span class="token operator">-</span>p tcp 64470</code></pre>
</div>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/group-replication-replication-group-members.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="group-replication-replication-group-members">
</a>
20.4.3 The replication_group_members Table
</h3>
</div>
</div>
</div>
<a class="indexterm" name="idm46045133655008">
</a>
<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">
performance_schema.replication_group_members
</code>
</a>
table is used for monitoring the status of the different server
instances that are members of the group. The information in the
table is updated whenever there is a view change, for example when
the configuration of the group is dynamically changed when a new
member joins. At that point, servers exchange some of their
metadata to synchronize themselves and continue to cooperate
together. The information is shared between all the server
instances that are members of the replication group, so
information on all the group members can be queried from any
member. This table can be used to get a high level view of the
state of a replication group, for example by issuing:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa41326853"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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>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 class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><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> CHANNEL_NAME <span class="token punctuation">|</span> MEMBER_ID <span class="token punctuation">|</span> MEMBER_HOST <span class="token punctuation">|</span> MEMBER_PORT <span class="token punctuation">|</span> MEMBER_STATE <span class="token punctuation">|</span> MEMBER_ROLE <span class="token punctuation">|</span> MEMBER_VERSION <span class="token punctuation">|</span> MEMBER_COMMUNICATION_STACK <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 class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><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> group_replication_applier <span class="token punctuation">|</span> d391e9ee<span class="token punctuation">-</span>2691<span class="token punctuation">-</span>11ec<span class="token punctuation">-</span>bf61<span class="token punctuation">-</span>00059a3c7a00 <span class="token punctuation">|</span> example1 <span class="token punctuation">|</span> 4410 <span class="token punctuation">|</span> ONLINE <span class="token punctuation">|</span> PRIMARY <span class="token punctuation">|</span> 8.4.3 <span class="token punctuation">|</span> XCom <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> group_replication_applier <span class="token punctuation">|</span> e059ce5c<span class="token punctuation">-</span>2691<span class="token punctuation">-</span>11ec<span class="token punctuation">-</span>8632<span class="token punctuation">-</span>00059a3c7a00 <span class="token punctuation">|</span> example2 <span class="token punctuation">|</span> 4420 <span class="token punctuation">|</span> ONLINE <span class="token punctuation">|</span> SECONDARY <span class="token punctuation">|</span> 8.4.3 <span class="token punctuation">|</span> XCom <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> group_replication_applier <span class="token punctuation">|</span> ecd9ad06<span class="token punctuation">-</span>2691<span class="token punctuation">-</span>11ec<span class="token punctuation">-</span>91c7<span class="token punctuation">-</span>00059a3c7a00 <span class="token punctuation">|</span> example3 <span class="token punctuation">|</span> 4430 <span class="token punctuation">|</span> ONLINE <span class="token punctuation">|</span> SECONDARY <span class="token punctuation">|</span> 8.4.3 <span class="token punctuation">|</span> XCom <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 class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><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 (0.0007 sec)</span></code></pre>
</div>
<p>
Based on this result we can see that the group consists of three
members. Shown in the table is each member's
<a class="link" href="replication-options.html#sysvar_server_uuid">
<code class="literal">
server_uuid
</code>
</a>
, as well as the
member's host name and port number, which clients use to connect
to it. The
<code class="literal">
MEMBER_STATE
</code>
column shows one of the
<a class="xref" href="group-replication-server-states.html" title="20.4.2 Group Replication Server States">
Section 20.4.2, “Group Replication Server States”
</a>
, in this case it
shows that all three members in this group are
<code class="literal">
ONLINE
</code>
, and the
<code class="literal">
MEMBER_ROLE
</code>
column shows that there are two secondaries, and a single primary.
Therefore this group must be running in single-primary mode. The
<code class="literal">
MEMBER_VERSION
</code>
column can be useful when you
are upgrading a group and are combining members running different
MySQL versions. The
<code class="literal">
MEMBER_COMMUNICATION_STACK
</code>
column shows the communication stack used for the group.
</p>
<p>
For more information about the
<code class="literal">
MEMBER_HOST
</code>
value and its impact on the distributed recovery process, see
<a class="xref" href="group-replication-user-credentials.html" title="20.2.1.3 User Credentials For Distributed Recovery">
Section 20.2.1.3, “User Credentials For Distributed Recovery”
</a>
.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/replication-solutions.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h2 class="title">
<a name="replication-solutions">
</a>
19.4 Replication Solutions
</h2>
</div>
</div>
</div>
<div class="toc">
<dl class="toc">
<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>
</div>
<p>
Replication can be used in many different environments for a range
of purposes. This section provides general notes and advice on using
replication for specific solution types.
</p>
<p>
For information on using replication in a backup environment,
including notes on the setup, backup procedure, and files to back
up, see
<a class="xref" href="replication-solutions-backups.html" title="19.4.1 Using Replication for Backups">
Section 19.4.1, “Using Replication for Backups”
</a>
.
</p>
<p>
For advice and tips on using different storage engines on the source
and replica, see
<a class="xref" href="replication-solutions-diffengines.html" title="19.4.4 Using Replication with Different Source and Replica Storage Engines">
Section 19.4.4, “Using Replication with Different Source and Replica Storage Engines”
</a>
.
</p>
<p>
Using replication as a scale-out solution requires some changes in
the logic and operation of applications that use the solution. 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>
For performance or data distribution reasons, you may want to
replicate different databases to different replicas. See
<a class="xref" href="replication-solutions-partitioning.html" title="19.4.6 Replicating Different Databases to Different Replicas">
Section 19.4.6, “Replicating Different Databases to Different Replicas”
</a>
</p>
<p>
As the number of replicas increases, the load on the source can
increase and lead to reduced performance (because of the need to
replicate the binary log to each replica). For tips on improving
your replication performance, including using a single secondary
server as the source, see
<a class="xref" href="replication-solutions-performance.html" title="19.4.7 Improving Replication Performance">
Section 19.4.7, “Improving Replication Performance”
</a>
.
</p>
<p>
For guidance on switching sources, or converting replicas into
sources as part of an emergency failover solution, see
<a class="xref" href="replication-solutions-switch.html" title="19.4.8 Switching Sources During Failover">
Section 19.4.8, “Switching Sources During Failover”
</a>
.
</p>
<p>
For information on security measures specific to servers in a
replication topology, see
<a class="xref" href="replication-security.html" title="19.3 Replication Security">
Section 19.3, “Replication Security”
</a>
.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/charset-column.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="charset-column">
</a>
12.3.5 Column Character Set and Collation
</h3>
</div>
</div>
</div>
<p>
Every
<span class="quote">
“
<span class="quote">
character
</span>
”
</span>
column (that is, a column of type
<a class="link" href="char.html" title="13.3.2 The CHAR and VARCHAR Types">
<code class="literal">
CHAR
</code>
</a>
,
<a class="link" href="char.html" title="13.3.2 The CHAR and VARCHAR Types">
<code class="literal">
VARCHAR
</code>
</a>
, a
<a class="link" href="blob.html" title="13.3.4 The BLOB and TEXT Types">
<code class="literal">
TEXT
</code>
</a>
type, or any synonym) has a
column character set and a column collation. Column definition
syntax for
<a class="link" href="create-table.html" title="15.1.20 CREATE TABLE Statement">
<code class="literal">
CREATE TABLE
</code>
</a>
and
<a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement">
<code class="literal">
ALTER TABLE
</code>
</a>
has optional clauses
for specifying the column character set and collation:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa97122512"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><em class="replaceable">col_name</em> {<span class="token datatype">CHAR</span> <span class="token operator">|</span> <span class="token datatype">VARCHAR</span> <span class="token operator">|</span> <span class="token datatype">TEXT</span>} <span class="token punctuation">(</span><em class="replaceable">col_length</em><span class="token punctuation">)</span>
<span class="token punctuation">[</span><span class="token keyword">CHARACTER</span> <span class="token keyword">SET</span> <em class="replaceable">charset_name</em><span class="token punctuation">]</span>
<span class="token punctuation">[</span><span class="token keyword">COLLATE</span> <em class="replaceable">collation_name</em><span class="token punctuation">]</span></code></pre>
</div>
<p>
These clauses can also be used for
<a class="link" href="enum.html" title="13.3.5 The ENUM Type">
<code class="literal">
ENUM
</code>
</a>
and
<a class="link" href="set.html" title="13.3.6 The SET Type">
<code class="literal">
SET
</code>
</a>
columns:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa72996852"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><em class="replaceable">col_name</em> {<span class="token datatype">ENUM</span> <span class="token operator">|</span> <span class="token keyword">SET</span>} <span class="token punctuation">(</span><em class="replaceable">val_list</em><span class="token punctuation">)</span>
<span class="token punctuation">[</span><span class="token keyword">CHARACTER</span> <span class="token keyword">SET</span> <em class="replaceable">charset_name</em><span class="token punctuation">]</span>
<span class="token punctuation">[</span><span class="token keyword">COLLATE</span> <em class="replaceable">collation_name</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="sa57541583"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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>
col1 <span class="token datatype">VARCHAR</span><span class="token punctuation">(</span><span class="token number">5</span><span class="token punctuation">)</span>
<span class="token keyword">CHARACTER</span> <span class="token keyword">SET</span> latin1
<span class="token keyword">COLLATE</span> latin1_german1_ci
<span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token keyword">ALTER</span> <span class="token keyword">TABLE</span> t1 <span class="token keyword">MODIFY</span>
col1 <span class="token datatype">VARCHAR</span><span class="token punctuation">(</span><span class="token number">5</span><span class="token punctuation">)</span>
<span class="token keyword">CHARACTER</span> <span class="token keyword">SET</span> latin1
<span class="token keyword">COLLATE</span> latin1_swedish_ci<span class="token punctuation">;</span></code></pre>
</div>
<p>
MySQL chooses the column character set and collation in the
following manner:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
If both
<code class="literal">
CHARACTER SET
<em class="replaceable">
<code>
charset_name
</code>
</em>
</code>
and
<code class="literal">
COLLATE
<em class="replaceable">
<code>
collation_name
</code>
</em>
</code>
are
specified, character set
<em class="replaceable">
<code>
charset_name
</code>
</em>
and collation
<em class="replaceable">
<code>
collation_name
</code>
</em>
are used.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa11732331"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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>
col1 <span class="token datatype">CHAR</span><span class="token punctuation">(</span><span class="token number">10</span><span class="token punctuation">)</span> <span class="token keyword">CHARACTER</span> <span class="token keyword">SET</span> utf8mb4 <span class="token keyword">COLLATE</span> utf8mb4_unicode_ci
<span class="token punctuation">)</span> <span class="token keyword">CHARACTER</span> <span class="token keyword">SET</span> latin1 <span class="token keyword">COLLATE</span> latin1_bin<span class="token punctuation">;</span></code></pre>
</div>
<p>
The character set and collation are specified for the
column, so they are used. The column has character set
<code class="literal">
utf8mb4
</code>
and collation
<code class="literal">
utf8mb4_unicode_ci
</code>
.
</p>
</li>
<li class="listitem">
<p>
If
<code class="literal">
CHARACTER SET
<em class="replaceable">
<code>
charset_name
</code>
</em>
</code>
is
specified without
<code class="literal">
COLLATE
</code>
, character set
<em class="replaceable">
<code>
charset_name
</code>
</em>
and its default
collation are used.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa39689946"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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>
col1 <span class="token datatype">CHAR</span><span class="token punctuation">(</span><span class="token number">10</span><span class="token punctuation">)</span> <span class="token keyword">CHARACTER</span> <span class="token keyword">SET</span> utf8mb4
<span class="token punctuation">)</span> <span class="token keyword">CHARACTER</span> <span class="token keyword">SET</span> latin1 <span class="token keyword">COLLATE</span> latin1_bin<span class="token punctuation">;</span></code></pre>
</div>
<p>
The character set is specified for the column, but the
collation is not. The column has character set
<code class="literal">
utf8mb4
</code>
and the default collation for
<code class="literal">
utf8mb4
</code>
, which is
<code class="literal">
utf8mb4_0900_ai_ci
</code>
. To see the default
collation for each character set, 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>
statement
or query the
<code class="literal">
INFORMATION_SCHEMA
</code>
<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>
table.
</p>
</li>
<li class="listitem">
<p>
If
<code class="literal">
COLLATE
<em class="replaceable">
<code>
collation_name
</code>
</em>
</code>
is
specified without
<code class="literal">
CHARACTER SET
</code>
, the
character set associated with
<em class="replaceable">
<code>
collation_name
</code>
</em>
and collation
<em class="replaceable">
<code>
collation_name
</code>
</em>
are used.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa76361105"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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>
col1 <span class="token datatype">CHAR</span><span class="token punctuation">(</span><span class="token number">10</span><span class="token punctuation">)</span> <span class="token keyword">COLLATE</span> utf8mb4_polish_ci
<span class="token punctuation">)</span> <span class="token keyword">CHARACTER</span> <span class="token keyword">SET</span> latin1 <span class="token keyword">COLLATE</span> latin1_bin<span class="token punctuation">;</span></code></pre>
</div>
<p>
The collation is specified for the column, but the character
set is not. The column has collation
<code class="literal">
utf8mb4_polish_ci
</code>
and the character set
is the one associated with the collation, which is
<code class="literal">
utf8mb4
</code>
.
</p>
</li>
<li class="listitem">
<p>
Otherwise (neither
<code class="literal">
CHARACTER SET
</code>
nor
<code class="literal">
COLLATE
</code>
is specified), the table
character set and collation are used.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa82328898"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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>
col1 <span class="token datatype">CHAR</span><span class="token punctuation">(</span><span class="token number">10</span><span class="token punctuation">)</span>
<span class="token punctuation">)</span> <span class="token keyword">CHARACTER</span> <span class="token keyword">SET</span> latin1 <span class="token keyword">COLLATE</span> latin1_bin<span class="token punctuation">;</span></code></pre>
</div>
<p>
Neither the character set nor collation is specified for the
column, so the table defaults are used. The column has
character set
<code class="literal">
latin1
</code>
and collation
<code class="literal">
latin1_bin
</code>
.
</p>
</li>
</ul>
</div>
<p>
The
<code class="literal">
CHARACTER SET
</code>
and
<code class="literal">
COLLATE
</code>
clauses are standard SQL.
</p>
<p>
If you use
<a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement">
<code class="literal">
ALTER TABLE
</code>
</a>
to convert
a column from one character set to another, MySQL attempts to
map the data values, but if the character sets are incompatible,
there may be data loss.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/source-installation-doxygen.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="source-installation-doxygen">
</a>
2.8.10 Generating MySQL Doxygen Documentation Content
</h3>
</div>
</div>
</div>
<p>
The MySQL source code contains internal documentation written
using Doxygen. The generated Doxygen content is available at
<a class="ulink" href="/doc/index-other.html" target="_top">
https://dev.mysql.com/doc/index-other.html
</a>
. It is also possible to
generate this content locally from a MySQL source distribution
using the following procedure:
</p>
<div class="orderedlist">
<ol class="orderedlist" type="1">
<li class="listitem">
<p>
Install
<span class="command">
<strong>
doxygen
</strong>
</span>
1.9.2 or later.
Distributions are available here at
<a class="ulink" href="http://www.doxygen.nl/" target="_blank">
http://www.doxygen.nl/
</a>
.
</p>
<p>
After installing
<span class="command">
<strong>
doxygen
</strong>
</span>
, verify the
version number:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-terminal"><div class="docs-select-all right" id="sa39148732"><div class="copy-help left">Press ⌘+C to 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">$> </span><span class="token command">doxygen</span> <span class="token property">--version</span>
1<span class="token punctuation">.</span>9<span class="token punctuation">.</span>2</code></pre>
</div>
</li>
<li class="listitem">
<p>
Install
<a class="ulink" href="http://plantuml.com/download.html" target="_blank">
PlantUML
</a>
.
</p>
<p>
When you install PlantUML on Windows (tested on Windows 10),
you must run it at least once as administrator so it creates
the registry keys. Open an administrator console and run this
command:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-terminal"><div class="docs-select-all right" id="sa97740789"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-terminal"><span class="token prompt">$> </span><span class="token command">java</span> <span class="token property">-jar</span> <em class="replaceable">path-to-plantuml<span class="token punctuation">.</span>jar</em></code></pre>
</div>
<p>
The command should open a GUI window and return no errors on
the console.
</p>
</li>
<li class="listitem">
<p>
Set the
<code class="literal">
PLANTUML_JAR_PATH
</code>
environment to
the location where you installed PlantUML. For example:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-terminal"><div class="docs-select-all right" id="sa5942745"><div class="copy-help left">Press ⌘+C to 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">$> </span><span class="token command">export</span> PLANTUML_JAR_PATH<span class="token attr-value"><span class="token punctuation">=</span><em class="replaceable">path-to-plantuml.jar</em></span></code></pre>
</div>
</li>
<li class="listitem">
<p>
Install the
<a class="ulink" href="http://www.graphviz.org/" target="_blank">
Graphviz
</a>
<span class="command">
<strong>
dot
</strong>
</span>
command.
</p>
<p>
After installing Graphviz, verify
<span class="command">
<strong>
dot
</strong>
</span>
availability. For example:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-terminal"><div class="docs-select-all right" id="sa46127159"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-terminal"><span class="token prompt">$> </span><span class="token command">which</span> dot
/usr/bin/dot
<span class="token prompt">$> </span><span class="token command">dot</span> <span class="token property">-V</span>
dot - graphviz version 2<span class="token punctuation">.</span>40<span class="token punctuation">.</span>1 <span class="token punctuation">(</span>20161225<span class="token punctuation">.</span>0304<span class="token punctuation">)</span></code></pre>
</div>
</li>
<li class="listitem">
<p>
Change location to the top-level directory of your MySQL
source distribution and do the following:
</p>
<p>
First, execute
<span class="command">
<strong>
cmake
</strong>
</span>
:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-terminal"><div class="docs-select-all right" id="sa71563337"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-terminal"><span class="token prompt">$> </span><span class="token command">cd</span> <em class="replaceable">mysql-source-directory</em>
<span class="token prompt">$> </span><span class="token command">mkdir</span> build
<span class="token prompt">$> </span><span class="token command">cd</span> build
<span class="token prompt">$> </span><span class="token command">cmake</span> <span class="token punctuation">.</span><span class="token punctuation">.</span></code></pre>
</div>
<p>
Next, generate the
<span class="command">
<strong>
doxygen
</strong>
</span>
documentation:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-terminal"><div class="docs-select-all right" id="sa89729466"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-terminal"><span class="token prompt">$> </span><span class="token command">make</span> doxygen</code></pre>
</div>
<p>
Inspect the error log, which is available in the
<code class="filename">
doxyerror.log
</code>
file in the top-level
directory. Assuming that the build executed successfully, view
the generated output using a browser. For example:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-terminal"><div class="docs-select-all right" id="sa90928850"><div class="copy-help left">Press ⌘+C to 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">firefox</span> doxygen/html/index<span class="token punctuation">.</span>html</code></pre>
</div>
</li>
</ol>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/group-replication-group-membership.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="group-replication-group-membership">
</a>
20.1.4.1 Group Membership
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045134392208">
</a>
<a class="indexterm" name="idm46045134390720">
</a>
<a class="indexterm" name="idm46045134389232">
</a>
<p>
In MySQL Group Replication, a set of servers forms a replication
group. A group has a name, which takes the form of a UUID. The
group is dynamic and servers can leave (either voluntarily or
involuntarily) and join it at any time. The group adjusts itself
whenever servers join or leave.
</p>
<p>
If a server joins the group, it automatically brings itself up
to date by fetching the missing state from an existing server.
If a server leaves the group, for instance it was taken down for
maintenance, the remaining servers notice that it has left and
reconfigure the group automatically.
</p>
<p>
Group Replication has a group membership service that defines
which servers are online and participating in the group. The
list of online servers is referred to as a
<span class="emphasis">
<em>
view
</em>
</span>
. Every server in the group has a
consistent view of which servers are the members participating
actively in the group at a given moment in time.
</p>
<p>
Group members must agree not only on transaction commits, but
also on which is the current view. If existing members agree
that a new server should become part of the group, the group is
reconfigured to integrate that server in it, which triggers a
view change. If a server leaves the group, either voluntarily or
not, the group dynamically rearranges its configuration and a
view change is triggered.
</p>
<p>
In the case where a member leaves the group voluntarily, it
first initiates a dynamic group reconfiguration, during which
all members have to agree on a new view without the leaving
server. However, if a member leaves the group involuntarily, for
example because it has stopped unexpectedly or the network
connection is down, it cannot initiate the reconfiguration. In
this situation, Group Replication's failure detection mechanism
recognizes after a short period of time that the member has
left, and a reconfiguration of the group without the failed
member is proposed. As with a member that leaves voluntarily,
the reconfiguration requires agreement from the majority of
servers in the group. However, if the group is not able to reach
agreement, for example because it partitioned in such a way that
there is no majority of servers online, the system is not able
to dynamically change the configuration, and blocks to prevent a
split-brain situation. This situation requires intervention from
an administrator.
</p>
<p>
It is possible for a member to go offline for a short time, then
attempt to rejoin the group again before the failure detection
mechanism has detected its failure, and before the group has
been reconfigured to remove the member. In this situation, the
rejoining member forgets its previous state, but if other
members send it messages that are intended for its pre-crash
state, this can cause issues including possible data
inconsistency. If a member in this situation participates in
XCom's consensus protocol, it could potentially cause XCom to
deliver different values for the same consensus round, by making
a different decision before and after failure.
</p>
<p>
To counter this possibility, MySQL Group Replication checks for
the situation where a new incarnation of the same server is
trying to join the group while its old incarnation (with the
same address and port number) is still listed as a member. The
new incarnation is blocked from joining the group until the old
incarnation can be removed by a reconfiguration. Note that if a
waiting period has been added by the
<a class="link" href="group-replication-system-variables.html#sysvar_group_replication_member_expel_timeout">
<code class="literal">
group_replication_member_expel_timeout
</code>
</a>
system variable to allow additional time for members to
reconnect with the group before they are expelled, a member
under suspicion can become active in the group again as its
current incarnation if it reconnects to the group before the
suspicion times out. When a member exceeds the expel timeout and
is expelled from the group, or when Group Replication is stopped
on the server by a
<a class="link" href="stop-group-replication.html" title="15.4.3.2 STOP GROUP_REPLICATION Statement">
<code class="literal">
STOP
GROUP_REPLICATION
</code>
</a>
statement or a server failure, it
must rejoin as a new incarnation.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/invisible-indexes.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="invisible-indexes">
</a>
10.3.12 Invisible Indexes
</h3>
</div>
</div>
</div>
<a class="indexterm" name="idm46045227027712">
</a>
<p>
MySQL supports invisible indexes; that is, indexes that are not
used by the optimizer. The feature applies to indexes other than
primary keys (either explicit or implicit).
</p>
<p>
Indexes are visible by default. To control visibility explicitly
for a new index, use a
<code class="literal">
VISIBLE
</code>
or
<code class="literal">
INVISIBLE
</code>
keyword as part of the index
definition for
<a class="link" href="create-table.html" title="15.1.20 CREATE TABLE Statement">
<code class="literal">
CREATE TABLE
</code>
</a>
,
<a class="link" href="create-index.html" title="15.1.15 CREATE INDEX Statement">
<code class="literal">
CREATE INDEX
</code>
</a>
, or
<a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement">
<code class="literal">
ALTER TABLE
</code>
</a>
:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa55693823"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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>
i <span class="token datatype">INT</span><span class="token punctuation">,</span>
j <span class="token datatype">INT</span><span class="token punctuation">,</span>
k <span class="token datatype">INT</span><span class="token punctuation">,</span>
<span class="token keyword">INDEX</span> i_idx <span class="token punctuation">(</span>i<span class="token punctuation">)</span> <span class="token keyword">INVISIBLE</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">INDEX</span> j_idx <span class="token keyword">ON</span> t1 <span class="token punctuation">(</span>j<span class="token punctuation">)</span> <span class="token keyword">INVISIBLE</span><span class="token punctuation">;</span>
<span class="token keyword">ALTER</span> <span class="token keyword">TABLE</span> t1 <span class="token keyword">ADD</span> <span class="token keyword">INDEX</span> k_idx <span class="token punctuation">(</span>k<span class="token punctuation">)</span> <span class="token keyword">INVISIBLE</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
To alter the visibility of an existing index, use a
<code class="literal">
VISIBLE
</code>
or
<code class="literal">
INVISIBLE
</code>
keyword with the
<code class="literal">
ALTER TABLE ... ALTER INDEX
</code>
operation:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa70964676"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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> t1 <span class="token keyword">ALTER</span> <span class="token keyword">INDEX</span> i_idx <span class="token keyword">INVISIBLE</span><span class="token punctuation">;</span>
<span class="token keyword">ALTER</span> <span class="token keyword">TABLE</span> t1 <span class="token keyword">ALTER</span> <span class="token keyword">INDEX</span> i_idx <span class="token keyword">VISIBLE</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
Information about whether an index is visible or invisible is
available from the Information Schema
<a class="link" href="information-schema-statistics-table.html" title="28.3.34 The INFORMATION_SCHEMA STATISTICS Table">
<code class="literal">
STATISTICS
</code>
</a>
table or
<a class="link" href="show-index.html" title="15.7.7.23 SHOW INDEX Statement">
<code class="literal">
SHOW INDEX
</code>
</a>
output. For example:
</p>
<a class="indexterm" name="idm46045227012560">
</a>
<a class="indexterm" name="idm46045227011072">
</a>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa44552294"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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> INDEX_NAME<span class="token punctuation">,</span> IS_VISIBLE
<span class="token keyword">FROM</span> INFORMATION_SCHEMA<span class="token punctuation">.</span>STATISTICS
<span class="token keyword">WHERE</span> TABLE_SCHEMA <span class="token operator">=</span> <span class="token string">'db1'</span> <span class="token operator">AND</span> <span class="token keyword">TABLE_NAME</span> <span class="token operator">=</span> <span class="token string">'t1'</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>
<span class="token output"><span class="token punctuation">|</span> INDEX_NAME <span class="token punctuation">|</span> IS_VISIBLE <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> i_idx <span class="token punctuation">|</span> YES <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> j_idx <span class="token punctuation">|</span> NO <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> k_idx <span class="token punctuation">|</span> NO <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></code></pre>
</div>
<p>
Invisible indexes make it possible to test the effect of
removing an index on query performance, without making a
destructive change that must be undone should the index turn out
to be required. Dropping and re-adding an index can be expensive
for a large table, whereas making it invisible and visible are
fast, in-place operations.
</p>
<p>
If an index made invisible actually is needed or used by the
optimizer, there are several ways to notice the effect of its
absence on queries for the table:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
Errors occur for queries that include index hints that refer
to the invisible index.
</p>
</li>
<li class="listitem">
<p>
Performance Schema data shows an increase in workload for
affected queries.
</p>
</li>
<li class="listitem">
<p>
Queries have different
<a class="link" href="explain.html" title="15.8.2 EXPLAIN Statement">
<code class="literal">
EXPLAIN
</code>
</a>
execution plans.
</p>
</li>
<li class="listitem">
<p>
Queries appear in the slow query log that did not appear
there previously.
</p>
</li>
</ul>
</div>
<a class="indexterm" name="idm46045226999776">
</a>
<a class="indexterm" name="idm46045226998256">
</a>
<p>
The
<a class="link" href="switchable-optimizations.html#optflag_use-invisible-indexes">
<code class="literal">
use_invisible_indexes
</code>
</a>
flag
of the
<a class="link" href="server-system-variables.html#sysvar_optimizer_switch">
<code class="literal">
optimizer_switch
</code>
</a>
system
variable controls whether the optimizer uses invisible indexes
for query execution plan construction. If the flag is
<code class="literal">
off
</code>
(the default), the optimizer ignores
invisible indexes (the same behavior as prior to the
introduction of this flag). If the flag is
<code class="literal">
on
</code>
, invisible indexes remain invisible but
the optimizer takes them into account for execution plan
construction.
</p>
<p>
Using the
<a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
<code class="literal">
SET_VAR
</code>
</a>
optimizer
hint to update the value of
<a class="link" href="server-system-variables.html#sysvar_optimizer_switch">
<code class="literal">
optimizer_switch
</code>
</a>
temporarily,
you can enable invisible indexes for the duration of a single
query only, like this:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa16262817"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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 comment" spellcheck="true">/*+ SET_VAR(optimizer_switch = 'use_invisible_indexes=on') */</span>
<span class="token operator">></span> i<span class="token punctuation">,</span> j <span class="token keyword">FROM</span> t1 <span class="token keyword">WHERE</span> j <span class="token operator">>=</span> <span class="token number">50</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> t1
partitions<span class="token punctuation">:</span> NULL
type<span class="token punctuation">:</span> range
possible_keys<span class="token punctuation">:</span> j_idx
key<span class="token punctuation">:</span> j_idx
key_len<span class="token punctuation">:</span> 5
ref<span class="token punctuation">:</span> NULL
rows<span class="token punctuation">:</span> 2
filtered<span class="token punctuation">:</span> 100.00
Extra<span class="token punctuation">:</span> Using index condition
</span>
<span class="token prompt">mysql></span> <span class="token keyword">EXPLAIN</span> <span class="token keyword">SELECT</span> i<span class="token punctuation">,</span> j <span class="token keyword">FROM</span> t1 <span class="token keyword">WHERE</span> j <span class="token operator">>=</span> <span class="token number">50</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> t1
partitions<span class="token punctuation">:</span> NULL
type<span class="token punctuation">:</span> ALL
possible_keys<span class="token punctuation">:</span> NULL
key<span class="token punctuation">:</span> NULL
key_len<span class="token punctuation">:</span> NULL
ref<span class="token punctuation">:</span> NULL
rows<span class="token punctuation">:</span> 5
filtered<span class="token punctuation">:</span> 33.33
Extra<span class="token punctuation">:</span> Using where</span></code></pre>
</div>
<p>
Index visibility does not affect index maintenance. For example,
an index continues to be updated per changes to table rows, and
a unique index prevents insertion of duplicates into a column,
regardless of whether the index is visible or invisible.
</p>
<p>
A table with no explicit primary key may still have an effective
implicit primary key if it has any
<code class="literal">
UNIQUE
</code>
indexes on
<code class="literal">
NOT NULL
</code>
columns. In this case,
the first such index places the same constraint on table rows as
an explicit primary key and that index cannot be made invisible.
Consider the following table definition:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa5318849"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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> t2 <span class="token punctuation">(</span>
i <span class="token datatype">INT</span> <span class="token operator">NOT</span> <span class="token boolean">NULL</span><span class="token punctuation">,</span>
j <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">UNIQUE</span> j_idx <span class="token punctuation">(</span>j<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>
The definition includes no explicit primary key, but the index
on
<code class="literal">
NOT NULL
</code>
column
<code class="literal">
j
</code>
places the same constraint on rows as a primary key and cannot
be made invisible:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa19284679"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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">TABLE</span> t2 <span class="token keyword">ALTER</span> <span class="token keyword">INDEX</span> j_idx <span class="token keyword">INVISIBLE</span><span class="token punctuation">;</span>
<span class="token output">ERROR 3522 (HY000)<span class="token punctuation">:</span> A primary key index cannot be invisible.</span></code></pre>
</div>
<p>
Now suppose that an explicit primary key is added to the table:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa7222166"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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> t2 <span class="token keyword">ADD</span> <span class="token keyword">PRIMARY</span> <span class="token keyword">KEY</span> <span class="token punctuation">(</span>i<span class="token punctuation">)</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
The explicit primary key cannot be made invisible. In addition,
the unique index on
<code class="literal">
j
</code>
no longer acts as an
implicit primary key and as a result can be made invisible:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa61652479"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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">TABLE</span> t2 <span class="token keyword">ALTER</span> <span class="token keyword">INDEX</span> j_idx <span class="token keyword">INVISIBLE</span><span class="token punctuation">;</span>
<span class="token output">Query OK, 0 rows affected (0.03 sec)</span></code></pre>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/data-masking-plugin-installation.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="data-masking-plugin-installation">
</a>
8.5.3.1 MySQL Enterprise Data Masking and De-Identification Plugin Installation
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045232497664">
</a>
<a class="indexterm" name="idm46045232496176">
</a>
<a class="indexterm" name="idm46045232494688">
</a>
<a class="indexterm" name="idm46045232493200">
</a>
<p>
This section describes how to install or uninstall MySQL Enterprise Data Masking and De-Identification,
which is implemented as a plugin library file containing a
plugin and several loadable functions. For general information
about installing or uninstalling plugins and loadable functions,
see
<a class="xref" href="plugin-loading.html" title="7.6.1 Installing and Uninstalling Plugins">
Section 7.6.1, “Installing and Uninstalling Plugins”
</a>
, and
<a class="xref" href="function-loading.html" title="7.7.1 Installing and Uninstalling Loadable Functions">
Section 7.7.1, “Installing and Uninstalling Loadable Functions”
</a>
.
</p>
<p>
To be usable by the server, the plugin library file must be
located in the MySQL plugin directory (the directory named by
the
<a class="link" href="server-system-variables.html#sysvar_plugin_dir">
<code class="literal">
plugin_dir
</code>
</a>
system
variable). If necessary, configure the plugin directory location
by setting the value of
<a class="link" href="server-system-variables.html#sysvar_plugin_dir">
<code class="literal">
plugin_dir
</code>
</a>
at server startup.
</p>
<p>
The plugin library file base name is
<code class="literal">
data_masking
</code>
. The file name suffix differs
per platform (for example,
<code class="filename">
.so
</code>
for Unix and
Unix-like systems,
<code class="filename">
.dll
</code>
for Windows).
</p>
<p>
To install the MySQL Enterprise Data Masking and De-Identification plugin and functions, use the
<a class="link" href="install-plugin.html" title="15.7.4.4 INSTALL PLUGIN Statement">
<code class="literal">
INSTALL PLUGIN
</code>
</a>
and
<a class="link" href="create-function.html" title="15.1.14 CREATE FUNCTION Statement">
<code class="literal">
CREATE FUNCTION
</code>
</a>
statements,
adjusting the
<code class="filename">
.so
</code>
suffix for your platform
as necessary:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa48046319"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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">INSTALL</span> <span class="token keyword">PLUGIN</span> data_masking <span class="token keyword">SONAME</span> <span class="token string">'data_masking.so'</span><span class="token punctuation">;</span>
<span class="token keyword">CREATE</span> <span class="token keyword">FUNCTION</span> gen_blocklist <span class="token keyword">RETURNS</span> <span class="token keyword">STRING</span>
<span class="token keyword">SONAME</span> <span class="token string">'data_masking.so'</span><span class="token punctuation">;</span>
<span class="token keyword">CREATE</span> <span class="token keyword">FUNCTION</span> gen_dictionary <span class="token keyword">RETURNS</span> <span class="token keyword">STRING</span>
<span class="token keyword">SONAME</span> <span class="token string">'data_masking.so'</span><span class="token punctuation">;</span>
<span class="token keyword">CREATE</span> <span class="token keyword">FUNCTION</span> gen_dictionary_drop <span class="token keyword">RETURNS</span> <span class="token keyword">STRING</span>
<span class="token keyword">SONAME</span> <span class="token string">'data_masking.so'</span><span class="token punctuation">;</span>
<span class="token keyword">CREATE</span> <span class="token keyword">FUNCTION</span> gen_dictionary_load <span class="token keyword">RETURNS</span> <span class="token keyword">STRING</span>
<span class="token keyword">SONAME</span> <span class="token string">'data_masking.so'</span><span class="token punctuation">;</span>
<span class="token keyword">CREATE</span> <span class="token keyword">FUNCTION</span> gen_range <span class="token keyword">RETURNS</span> <span class="token datatype">INTEGER</span>
<span class="token keyword">SONAME</span> <span class="token string">'data_masking.so'</span><span class="token punctuation">;</span>
<span class="token keyword">CREATE</span> <span class="token keyword">FUNCTION</span> gen_rnd_email <span class="token keyword">RETURNS</span> <span class="token keyword">STRING</span>
<span class="token keyword">SONAME</span> <span class="token string">'data_masking.so'</span><span class="token punctuation">;</span>
<span class="token keyword">CREATE</span> <span class="token keyword">FUNCTION</span> gen_rnd_pan <span class="token keyword">RETURNS</span> <span class="token keyword">STRING</span>
<span class="token keyword">SONAME</span> <span class="token string">'data_masking.so'</span><span class="token punctuation">;</span>
<span class="token keyword">CREATE</span> <span class="token keyword">FUNCTION</span> gen_rnd_ssn <span class="token keyword">RETURNS</span> <span class="token keyword">STRING</span>
<span class="token keyword">SONAME</span> <span class="token string">'data_masking.so'</span><span class="token punctuation">;</span>
<span class="token keyword">CREATE</span> <span class="token keyword">FUNCTION</span> gen_rnd_us_phone <span class="token keyword">RETURNS</span> <span class="token keyword">STRING</span>
<span class="token keyword">SONAME</span> <span class="token string">'data_masking.so'</span><span class="token punctuation">;</span>
<span class="token keyword">CREATE</span> <span class="token keyword">FUNCTION</span> mask_inner <span class="token keyword">RETURNS</span> <span class="token keyword">STRING</span>
<span class="token keyword">SONAME</span> <span class="token string">'data_masking.so'</span><span class="token punctuation">;</span>
<span class="token keyword">CREATE</span> <span class="token keyword">FUNCTION</span> mask_outer <span class="token keyword">RETURNS</span> <span class="token keyword">STRING</span>
<span class="token keyword">SONAME</span> <span class="token string">'data_masking.so'</span><span class="token punctuation">;</span>
<span class="token keyword">CREATE</span> <span class="token keyword">FUNCTION</span> mask_pan <span class="token keyword">RETURNS</span> <span class="token keyword">STRING</span>
<span class="token keyword">SONAME</span> <span class="token string">'data_masking.so'</span><span class="token punctuation">;</span>
<span class="token keyword">CREATE</span> <span class="token keyword">FUNCTION</span> mask_pan_relaxed <span class="token keyword">RETURNS</span> <span class="token keyword">STRING</span>
<span class="token keyword">SONAME</span> <span class="token string">'data_masking.so'</span><span class="token punctuation">;</span>
<span class="token keyword">CREATE</span> <span class="token keyword">FUNCTION</span> mask_ssn <span class="token keyword">RETURNS</span> <span class="token keyword">STRING</span>
<span class="token keyword">SONAME</span> <span class="token string">'data_masking.so'</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
If the plugin and functions are used on a replication source
server, install them on all replica servers as well to avoid
replication issues.
</p>
<p>
Once installed as just described, the plugin and functions
remain installed until uninstalled. To remove them, use the
<a class="link" href="uninstall-plugin.html" title="15.7.4.6 UNINSTALL PLUGIN Statement">
<code class="literal">
UNINSTALL PLUGIN
</code>
</a>
and
<a class="link" href="drop-function.html" title="15.1.26 DROP FUNCTION Statement">
<code class="literal">
DROP FUNCTION
</code>
</a>
statements:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa94701483"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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">UNINSTALL</span> <span class="token keyword">PLUGIN</span> data_masking<span class="token punctuation">;</span>
<span class="token keyword">DROP</span> <span class="token keyword">FUNCTION</span> gen_blocklist<span class="token punctuation">;</span>
<span class="token keyword">DROP</span> <span class="token keyword">FUNCTION</span> gen_dictionary<span class="token punctuation">;</span>
<span class="token keyword">DROP</span> <span class="token keyword">FUNCTION</span> gen_dictionary_drop<span class="token punctuation">;</span>
<span class="token keyword">DROP</span> <span class="token keyword">FUNCTION</span> gen_dictionary_load<span class="token punctuation">;</span>
<span class="token keyword">DROP</span> <span class="token keyword">FUNCTION</span> gen_range<span class="token punctuation">;</span>
<span class="token keyword">DROP</span> <span class="token keyword">FUNCTION</span> gen_rnd_email<span class="token punctuation">;</span>
<span class="token keyword">DROP</span> <span class="token keyword">FUNCTION</span> gen_rnd_pan<span class="token punctuation">;</span>
<span class="token keyword">DROP</span> <span class="token keyword">FUNCTION</span> gen_rnd_ssn<span class="token punctuation">;</span>
<span class="token keyword">DROP</span> <span class="token keyword">FUNCTION</span> gen_rnd_us_phone<span class="token punctuation">;</span>
<span class="token keyword">DROP</span> <span class="token keyword">FUNCTION</span> mask_inner<span class="token punctuation">;</span>
<span class="token keyword">DROP</span> <span class="token keyword">FUNCTION</span> mask_outer<span class="token punctuation">;</span>
<span class="token keyword">DROP</span> <span class="token keyword">FUNCTION</span> mask_pan<span class="token punctuation">;</span>
<span class="token keyword">DROP</span> <span class="token keyword">FUNCTION</span> mask_pan_relaxed<span class="token punctuation">;</span>
<span class="token keyword">DROP</span> <span class="token keyword">FUNCTION</span> mask_ssn<span class="token punctuation">;</span></code></pre>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/innodb-deadlocks.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="innodb-deadlocks">
</a>
17.7.5 Deadlocks in InnoDB
</h3>
</div>
</div>
</div>
<div class="toc">
<dl class="toc">
<dt>
<span class="section">
<a href="innodb-deadlock-example.html">
17.7.5.1 An InnoDB Deadlock Example
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="innodb-deadlock-detection.html">
17.7.5.2 Deadlock Detection
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="innodb-deadlocks-handling.html">
17.7.5.3 How to Minimize and Handle Deadlocks
</a>
</span>
</dt>
</dl>
</div>
<a class="indexterm" name="idm46045163854400">
</a>
<a class="indexterm" name="idm46045163852912">
</a>
<a class="indexterm" name="idm46045163851008">
</a>
<a class="indexterm" name="idm46045163849520">
</a>
<p>
A deadlock is a situation in which multiple transactions are
unable to proceed because each transaction holds a lock that is
needed by another one. Because all transactions involved are
waiting for the same resource to become available, none of them
ever releases the lock it holds.
</p>
<p>
A deadlock can occur when transactions lock rows in multiple
tables (through statements such as
<a class="link" href="update.html" title="15.2.17 UPDATE Statement">
<code class="literal">
UPDATE
</code>
</a>
or
<a class="link" href="select.html" title="15.2.13 SELECT Statement">
<code class="literal">
SELECT ... FOR
UPDATE
</code>
</a>
), but in the opposite order. A deadlock can also
occur when such statements lock ranges of index records and gaps,
with each transaction acquiring some locks but not others due to a
timing issue. For a deadlock example, see
<a class="xref" href="innodb-deadlock-example.html" title="17.7.5.1 An InnoDB Deadlock Example">
Section 17.7.5.1, “An InnoDB Deadlock Example”
</a>
.
</p>
<p>
To reduce the possibility of deadlocks, use transactions rather
than
<a class="link" href="lock-tables.html" title="15.3.6 LOCK TABLES and UNLOCK TABLES Statements">
<code class="literal">
LOCK TABLES
</code>
</a>
statements; keep
transactions that insert or update data small enough that they do
not stay open for long periods of time; when different
transactions update multiple tables or large ranges of rows, use
the same order of operations (such as
<a class="link" href="select.html" title="15.2.13 SELECT Statement">
<code class="literal">
SELECT ... FOR
UPDATE
</code>
</a>
) in each transaction; create indexes on the
columns used in
<a class="link" href="select.html" title="15.2.13 SELECT Statement">
<code class="literal">
SELECT ...
FOR UPDATE
</code>
</a>
and
<a class="link" href="update.html" title="15.2.17 UPDATE Statement">
<code class="literal">
UPDATE ... WHERE
</code>
</a>
statements. The possibility of deadlocks is not affected by the
isolation level, because the isolation level changes the behavior
of read operations, while deadlocks occur because of write
operations. For more information about avoiding and recovering
from deadlock conditions, see
<a class="xref" href="innodb-deadlocks-handling.html" title="17.7.5.3 How to Minimize and Handle Deadlocks">
Section 17.7.5.3, “How to Minimize and Handle Deadlocks”
</a>
.
</p>
<p>
When deadlock detection is enabled (the default) and a deadlock
does occur,
<code class="literal">
InnoDB
</code>
detects the condition and
rolls back one of the transactions (the victim). If deadlock
detection is disabled using the
<a class="link" href="innodb-parameters.html#sysvar_innodb_deadlock_detect">
<code class="literal">
innodb_deadlock_detect
</code>
</a>
variable,
<code class="literal">
InnoDB
</code>
relies on the
<a class="link" href="innodb-parameters.html#sysvar_innodb_lock_wait_timeout">
<code class="literal">
innodb_lock_wait_timeout
</code>
</a>
setting
to roll back transactions in case of a deadlock. Thus, even if
your application logic is correct, you must still handle the case
where a transaction must be retried. To view the last deadlock in
an
<code class="literal">
InnoDB
</code>
user transaction, use
<a class="link" href="show-engine.html" title="15.7.7.16 SHOW ENGINE Statement">
<code class="literal">
SHOW ENGINE INNODB
STATUS
</code>
</a>
. If frequent deadlocks highlight a problem with
transaction structure or application error handling, enable
<a class="link" href="innodb-parameters.html#sysvar_innodb_print_all_deadlocks">
<code class="literal">
innodb_print_all_deadlocks
</code>
</a>
to
print information about all deadlocks to the
<a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
<span class="command">
<strong>
mysqld
</strong>
</span>
</a>
error log. For more information about
how deadlocks are automatically detected and handled, see
<a class="xref" href="innodb-deadlock-detection.html" title="17.7.5.2 Deadlock Detection">
Section 17.7.5.2, “Deadlock Detection”
</a>
.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/collation-diagnostics.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="collation-diagnostics">
</a>
12.14.4.3 Diagnostics During Index.xml Parsing
</h4>
</div>
</div>
</div>
<p>
The MySQL server generates diagnostics when it finds problems
while parsing the
<code class="filename">
Index.xml
</code>
file:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
Unknown tags are written to the error log. For example,
the following message results if a collation definition
contains a
<code class="literal">
<aaa>
</code>
tag:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-none"><div class="docs-select-all right" id="sa72810425"><div class="copy-help left">Press ⌘+C to 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">[Warning] Buffered warning: Unknown LDML tag:
'charsets/charset/collation/rules/aaa'</code></pre>
</div>
</li>
<li class="listitem">
<p>
If collation initialization is not possible, the server
reports an
<span class="quote">
“
<span class="quote">
Unknown collation
</span>
”
</span>
error, and
also generates warnings explaining the problems, such as
in the previous example. In other cases, when a collation
description is generally correct but contains some unknown
tags, the collation is initialized and is available for
use. The unknown parts are ignored, but a warning is
generated in the error log.
</p>
</li>
<li class="listitem">
<p>
Problems with collations generate warnings that clients
can display with
<a class="link" href="show-warnings.html" title="15.7.7.42 SHOW WARNINGS Statement">
<code class="literal">
SHOW
WARNINGS
</code>
</a>
. Suppose that a reset rule contains an
expansion longer than the maximum supported length of 6
characters:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-xml"><div class="docs-select-all right" id="sa33482238"><div class="copy-help left">Press ⌘+C to 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>reset</span><span class="token punctuation">></span></span>abcdefghi<span class="token tag"><span class="token tag"><span class="token punctuation"></</span>reset</span><span class="token punctuation">></span></span>
<span class="token tag"><span class="token tag"><span class="token punctuation"><</span>i</span><span class="token punctuation">></span></span>x<span class="token tag"><span class="token tag"><span class="token punctuation"></</span>i</span><span class="token punctuation">></span></span></code></pre>
</div>
<p>
An attempt to use the collation produces warnings:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa63166861"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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> _utf8mb4<span class="token string">'test'</span> <span class="token keyword">COLLATE</span> utf8mb4_test_ci<span class="token punctuation">;</span>
<span class="token output">ERROR 1273 (HY000)<span class="token punctuation">:</span> Unknown collation<span class="token punctuation">:</span> 'utf8mb4_test_ci'</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> Error <span class="token punctuation">|</span> 1273 <span class="token punctuation">|</span> Unknown collation: 'utf8mb4_test_ci' <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> Warning <span class="token punctuation">|</span> 1273 <span class="token punctuation">|</span> Expansion is too long at 'abcdefghi=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 class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="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>
</ul>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/faqs-c-api.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h2 class="title">
<a name="faqs-c-api">
</a>
A.13 MySQL 8.4 FAQ: C API, libmysql
</h2>
</div>
</div>
</div>
<a class="indexterm" name="idm46045055076832">
</a>
<a class="indexterm" name="idm46045055075408">
</a>
<a class="indexterm" name="idm46045055073952">
</a>
<a class="indexterm" name="idm46045055072464">
</a>
<p>
Frequently asked questions about MySQL C API and libmysql.
</p>
<div class="qandaset">
<a name="idm46045055070512">
</a>
<dl>
<dt>
A.13.1.
<a href="faqs-c-api.html#faq-mysql-c-api-what-is-native-c-api">
What is “MySQL Native C API”? What are typical
benefits and use cases?
</a>
</dt>
<dt>
A.13.2.
<a href="faqs-c-api.html#faq-mysql-c-api-which-version-to-use">
Which version of libmysql should I use?
</a>
</dt>
<dt>
A.13.3.
<a href="faqs-c-api.html#faq-mysql-c-api-using-x-devapi">
What if I want to use the “NoSQL” X DevAPI?
</a>
</dt>
<dt>
A.13.4.
<a href="faqs-c-api.html#faq-mysql-c-api-download">
How to I download libmysql?
</a>
</dt>
<dt>
A.13.5.
<a href="faqs-c-api.html#faq-mysql-c-api-documentation">
Where is the documentation?
</a>
</dt>
<dt>
A.13.6.
<a href="faqs-c-api.html#faq-mysql-c-api-bugs">
How do I report bugs?
</a>
</dt>
<dt>
A.13.7.
<a href="faqs-c-api.html#faq-mysql-c-api-compile">
Is it possible to compile the library myself?
</a>
</dt>
</dl>
<table border="0" style="width: 100%;">
<colgroup>
<col align="left" width="1%"/>
<col/>
</colgroup>
<tbody>
<tr class="question">
<td align="left" valign="top">
<a name="faq-mysql-c-api-what-is-native-c-api">
</a>
<a name="idm46045055069760">
</a>
<p>
<b>
A.13.1.
</b>
</p>
</td>
<td align="left" valign="top">
<p>
What is
<span class="quote">
“
<span class="quote">
MySQL Native C API
</span>
”
</span>
? What are typical
benefits and use cases?
</p>
</td>
</tr>
<tr class="answer">
<td align="left" valign="top">
</td>
<td align="left" valign="top">
<p>
libmysql is a C-based API that you can use in C applications to
connect with the MySQL database server. It is also itself used
as the foundation for drivers for standard database APIs like
ODBC, Perl's DBI, and Python's DB API.
</p>
</td>
</tr>
<tr class="question">
<td align="left" valign="top">
<a name="faq-mysql-c-api-which-version-to-use">
</a>
<a name="idm46045055067024">
</a>
<p>
<b>
A.13.2.
</b>
</p>
</td>
<td align="left" valign="top">
<p>
Which version of libmysql should I use?
</p>
</td>
</tr>
<tr class="answer">
<td align="left" valign="top">
</td>
<td align="left" valign="top">
<p>
For MySQL 8.4 we recommend libmysql 8.4.
</p>
</td>
</tr>
<tr class="question">
<td align="left" valign="top">
<a name="faq-mysql-c-api-using-x-devapi">
</a>
<a name="idm46045055065024">
</a>
<p>
<b>
A.13.3.
</b>
</p>
</td>
<td align="left" valign="top">
<p>
What if I want to use the
<span class="quote">
“
<span class="quote">
NoSQL
</span>
”
</span>
X DevAPI?
</p>
</td>
</tr>
<tr class="answer">
<td align="left" valign="top">
</td>
<td align="left" valign="top">
<p>
For C-language and X DevApi Document Store for MySQL, we
recommend MySQL Connector/C++. Connector/C++ has compatible C
headers. (This is not applicable to MySQL 5.7 or before.)
</p>
</td>
</tr>
<tr class="question">
<td align="left" valign="top">
<a name="faq-mysql-c-api-download">
</a>
<a name="idm46045055062448">
</a>
<p>
<b>
A.13.4.
</b>
</p>
</td>
<td align="left" valign="top">
<p>
How to I download libmysql?
</p>
</td>
</tr>
<tr class="answer">
<td align="left" valign="top">
</td>
<td align="left" valign="top">
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
Linux: The Client Utilities Package is available from the
<a class="ulink" href="https://dev.mysql.com/downloads/mysql/" target="_top">
MySQL
Community Server
</a>
download page.
</p>
</li>
<li class="listitem">
<p>
Repos: The Client Utilities Package is available from the
<a class="ulink" href="https://dev.mysql.com/downloads/repo/yum/" target="_top">
Yum
</a>
,
<a class="ulink" href="https://dev.mysql.com/downloads/repo/apt/" target="_top">
APT
</a>
,
<a class="ulink" href="https://dev.mysql.com/downloads/repo/suse/" target="_top">
SuSE
repositories
</a>
.
</p>
</li>
<li class="listitem">
<p>
Windows: The Client Utilities Package is available from
<a class="ulink" href="https://dev.mysql.com/downloads/installer/" target="_top">
Windows
Installer
</a>
.
</p>
</li>
</ul>
</div>
</td>
</tr>
<tr class="question">
<td align="left" valign="top">
<a name="faq-mysql-c-api-documentation">
</a>
<a name="idm46045055054080">
</a>
<p>
<b>
A.13.5.
</b>
</p>
</td>
<td align="left" valign="top">
<p>
Where is the documentation?
</p>
</td>
</tr>
<tr class="answer">
<td align="left" valign="top">
</td>
<td align="left" valign="top">
<p>
See
<a class="ulink" href="/doc/c-api/8.4/en/" target="_top">
MySQL 8.4 C API Developer Guide
</a>
.
</p>
</td>
</tr>
<tr class="question">
<td align="left" valign="top">
<a name="faq-mysql-c-api-bugs">
</a>
<a name="idm46045055051424">
</a>
<p>
<b>
A.13.6.
</b>
</p>
</td>
<td align="left" valign="top">
<p>
How do I report bugs?
</p>
</td>
</tr>
<tr class="answer">
<td align="left" valign="top">
</td>
<td align="left" valign="top">
<p>
Please report any bugs or inconsistencies you observe to our
<a class="ulink" href="https://bugs.mysql.com/" target="_blank">
Bugs Database
</a>
.
Select the C API Client as shown.
</p>
</td>
</tr>
<tr class="question">
<td align="left" valign="top">
<a name="faq-mysql-c-api-compile">
</a>
<a name="idm46045055048704">
</a>
<p>
<b>
A.13.7.
</b>
</p>
</td>
<td align="left" valign="top">
<p>
Is it possible to compile the library myself?
</p>
</td>
</tr>
<tr class="answer">
<td align="left" valign="top">
</td>
<td align="left" valign="top">
<p>
Compiling MySQL Server also compiles libmysqlclient; there is
not a way to only compile libmysqlclient. For related
information, see
<a class="ulink" href="/doc/c-api/8.4/en/c-api-implementations.html" target="_top">
MySQL C API Implementations
</a>
.
</p>
</td>
</tr>
</tbody>
</table>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/sys-user-summary-by-file-io-type.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="sys-user-summary-by-file-io-type">
</a>
30.4.3.43 The user_summary_by_file_io_type and x$user_summary_by_file_io_type
Views
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045061923408">
</a>
<a class="indexterm" name="idm46045061921952">
</a>
<a class="indexterm" name="idm46045061920448">
</a>
<a class="indexterm" name="idm46045061918944">
</a>
<p>
These views summarize file I/O, grouped by user and event
type. By default, rows are sorted by user and descending total
latency.
</p>
<p>
The
<a class="link" href="sys-user-summary-by-file-io-type.html" title="30.4.3.43 The user_summary_by_file_io_type and x$user_summary_by_file_io_type Views">
<code class="literal">
user_summary_by_file_io_type
</code>
</a>
and
<a class="link" href="sys-user-summary-by-file-io-type.html" title="30.4.3.43 The user_summary_by_file_io_type and x$user_summary_by_file_io_type Views">
<code class="literal">
x$user_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">
user
</code>
</p>
<p>
The client user name. Rows for which the
<code class="literal">
USER
</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 user.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
latency
</code>
</p>
<p>
The total wait time of timed occurrences of the file I/O
event for the user.
</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 user.
</p>
</li>
</ul>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/performance-schema-tp-connections-table.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="performance-schema-tp-connections-table">
</a>
29.12.16.1 The tp_connections Table
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045069904720">
</a>
<a class="indexterm" name="idm46045069903232">
</a>
<p>
The
<code class="literal">
tp_connections
</code>
table contains one row
per connection managed by the Thread Pool plugin. Each row
provides information about the current state of a thread pool
connection.
</p>
<p>
The
<code class="literal">
tp_connections
</code>
table contains the
following rows:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<code class="literal">
CONNECTION_ID
</code>
</p>
<p>
The connection ID as reported by
<a class="link" href="select.html" title="15.2.13 SELECT Statement">
<code class="literal">
SELECT
</code>
</a>
<a class="link" href="information-functions.html#function_connection-id">
<code class="literal">
CONNECTION_ID()
</code>
</a>
.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
TP_GROUP_ID
</code>
</p>
<p>
The index of the thread group in the global array. This
column and
<code class="literal">
TP_PROCESSING_THREAD_NUMBER
</code>
serve as a foreign key into the
<a class="link" href="performance-schema-tp-thread-state-table.html" title="29.12.16.4 The tp_thread_state Table">
<code class="literal">
tp_thread_state
</code>
</a>
table.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
TP_PROCESSING_THREAD_NUMBER
</code>
</p>
<p>
This may be NULL if no thread is currently attached to the
connection.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
THREAD_ID
</code>
</p>
<p>
The Performance Schema thread ID.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
STATE
</code>
</p>
<p>
The connection state; this is one of
<code class="literal">
Established
</code>
,
<code class="literal">
Armed
</code>
,
<code class="literal">
Queued
</code>
,
<code class="literal">
Waiting for
Credit
</code>
,
<code class="literal">
Attached
</code>
,
<code class="literal">
Expired
</code>
, or
<code class="literal">
Killed
</code>
.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
ACTIVE_FLAG
</code>
</p>
<p>
When this is
<code class="literal">
0
</code>
, the connection is not
attached to any worker thread.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
KILLED_STATE
</code>
</p>
<p>
Reports the current stage in the process of killing the
connection.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
CLEANUP_STATE
</code>
</p>
<p>
Reports the current stage in the cleanup process when
closing the connection.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
TIME_OF_LAST_EVENT_COMPLETION
</code>
</p>
<p>
Timestamp showing when the connection last processed a
request.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
TIME_OF_EXPIRY
</code>
</p>
<p>
Timestamp showing when an idle connection will expire if
no new request arrives before then; this is
<code class="literal">
NULL
</code>
when the thread is currently
processing a request.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
TIME_OF_ADD
</code>
</p>
<p>
Timestamp showing when the connection was added to the
thread pool's connection request queue.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
TIME_OF_POP
</code>
</p>
<p>
Timestamp showing when the connection was dequeued
(popped) from the queue by a connection handler thread.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
TIME_OF_ARM
</code>
</p>
<p>
Timestamp showing when the connection file descriptor was
last added to the set monitored by
<code class="literal">
poll()
</code>
or
<code class="literal">
epoll()
</code>
.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
CONNECT_HANDLER_INDEX
</code>
</p>
<p>
The index of the connection handler thread in the group
which processed the connection request; a higher number
means the connection load has triggered the creation of
additional connection handler threads.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
TYPE
</code>
</p>
<p>
The connection type; this is one of
<code class="literal">
User
</code>
,
<code class="literal">
Admin_interface
</code>
or
<code class="literal">
Admin_privilege
</code>
;
<code class="literal">
Admin_privilege
</code>
means that this
connection had been using the normal interface, but was
placed in the
<code class="literal">
admin
</code>
group due to the
user having the
<a class="link" href="privileges-provided.html#priv_tp-connection-admin">
<code class="literal">
TP_CONNECTION_ADMIN
</code>
</a>
privilege.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
DIRECT_QUERY_EVENTS
</code>
</p>
<p>
The number of queries executed directly by this
connection.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
QUEUED_QUERY_EVENTS
</code>
</p>
<p>
The number of queued queries executed by this connection.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
TIME_OF_EVENT_ARRIVAL
</code>
</p>
<p>
A timestamp showing when
<code class="literal">
poll_wait()
</code>
returns with an event for the connection; this value is
needed to calculate
<code class="literal">
MANAGEMENT_TIME
</code>
.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
MANAGEMENT_TIME
</code>
</p>
<p>
The accumulated time between the return from waiting on
file descriptors; this includes the time spent queued for
queries which are not executed directly.
</p>
</li>
</ul>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/mysql-cluster-tls-overview.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="mysql-cluster-tls-overview">
</a>
25.6.15.1 Overview of TLS for NDB Cluster
</h4>
</div>
</div>
</div>
<p>
TLS can be used to secure network communications in NDB Cluster
8.3 and later. NDB Transporter connections secured by TLS use
TLS mutual authentication, in which each node validates the
certificate of its peer. A node certificate can also be bound to
a particular hostname; in this case, a peer authorizes the
certificate only if the hostname can be verified.
</p>
<p>
A node's own certificate file contains the entire chain of
trust it uses to validate the certificates of its peers. This
usually includes only its own certificate and that of the
issuing CA, but may include additional CAs. Because an NDB
cluster is considered a realm of trust, the CA should be limited
in scope to a single cluster.
</p>
<p>
In order to obtain signed node certificates, it is necessary
first to create a Certification Authority (CA). When TLS is
deployed, every node has an authentic certificate, which is
signed by the CA. Only the administrator (DBA) should have
access to the private CA signing key with which valid node
certificates are created.
</p>
<p>
Hostname bindings are created for management and API node
certificates by default. Since NDB Cluster data nodes are
already subject to hostname checks as part of node ID
allocation, the default behavior is to not add an additional
hostname check for TLS.
</p>
<p>
A certificate is no longer valid upon arrival of the expiration
date. To minimize the impact of certificate expiration on system
availability, a cluster should have several certificates with
staggered expiration dates; client certificates should expire
earliest, followed by data node certificates, and then by
management server certificates. To facilitate staggered
expiration, each certificate is associated with a node type; a
given node uses keys and certificates of the appropriate type
only.
</p>
<p>
Private keys are created in place; copying of files containing
private keys is minimized. Both private keys and certificates
are labeled as either active (current) or pending. It is
possible to rotate keys to allow for pending keys to replace
active keys before the active keys expire.
</p>
<p>
Due to the potentially large numbers of files involved, NDB
follows several naming conventions for files storing keys,
signing requests, and certificates. These names are not user
configurable, although the directories where these files are
stored can be determined by the user.
</p>
<p>
By default, NDB Cluster CA private keys are protected by a
passphrase which must be provided when creating a signed node
certificate. Node private keys are stored unencrypted, so that
they can be opened automatically at node startup time. Private
key files are read-only (Unix file mode 0400).
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/replication-howto-additionalslaves.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="replication-howto-additionalslaves">
</a>
19.1.2.8 Adding Replicas to a Replication Environment
</h4>
</div>
</div>
</div>
<p>
You can add another replica to an existing replication
configuration without stopping the source server. To do this,
you can set up the new replica by copying the data directory of
an existing replica, and giving the new replica a different
server ID (which is user-specified) and server UUID (which is
generated at startup).
</p>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
If the replication source server or existing replica that you
are copying to create the new replica has any scheduled
events, ensure that these are disabled on the new replica
before you start it. If an event runs on the new replica that
has already run on the source, the duplicated operation causes
an error. The Event Scheduler is controlled by the
<a class="link" href="server-system-variables.html#sysvar_event_scheduler">
<code class="literal">
event_scheduler
</code>
</a>
system
variable, which defaults to
<code class="literal">
ON
</code>
, so events
that are active on the original server run by default when the
new replica starts up. To stop all events from running on the
new replica, set the
<a class="link" href="server-system-variables.html#sysvar_event_scheduler">
<code class="literal">
event_scheduler
</code>
</a>
system
variable to
<code class="literal">
OFF
</code>
or
<code class="literal">
DISABLED
</code>
on the new replica. Alternatively,
you can use the
<a class="link" href="alter-event.html" title="15.1.3 ALTER EVENT Statement">
<code class="literal">
ALTER EVENT
</code>
</a>
statement to set individual events to
<code class="literal">
DISABLE
</code>
or
<code class="literal">
DISABLE ON
REPLICA
</code>
to prevent them from running on the new
replica. You can list the events on a server using the
<a class="link" href="show.html" title="15.7.7 SHOW Statements">
<code class="literal">
SHOW
</code>
</a>
statement or the
Information Schema
<a class="link" href="information-schema-events-table.html" title="28.3.14 The INFORMATION_SCHEMA EVENTS Table">
<code class="literal">
EVENTS
</code>
</a>
table.
For more information, see
<a class="xref" href="replication-features-invoked.html" title="19.5.1.16 Replication of Invoked Features">
Section 19.5.1.16, “Replication of Invoked Features”
</a>
.
</p>
</div>
<p>
As an alternative to creating a new replica in this way, MySQL
Server's clone plugin can be used to transfer all the data and
replication settings from an existing replica to a clone. For
instructions to use this method, see
<a class="xref" href="clone-plugin-replication.html" title="7.6.7.7 Cloning for Replication">
Section 7.6.7.7, “Cloning for Replication”
</a>
.
</p>
<p>
To duplicate an existing replica without cloning, follow these
steps:
</p>
<div class="orderedlist">
<ol class="orderedlist" type="1">
<li class="listitem">
<p>
Stop the existing replica and record the replica status
information, particularly the source binary log file and
relay log file positions. You can view the replica status
either in the Performance Schema replication tables (see
<a class="xref" href="performance-schema-replication-tables.html" title="29.12.11 Performance Schema Replication Tables">
Section 29.12.11, “Performance Schema Replication Tables”
</a>
), or
by issuing
<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>
as follows:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa5314456"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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">STOP</span> <span class="token keyword">REPLICA</span><span class="token punctuation">;</span>
<span class="token prompt">mysql></span> <span class="token keyword">SHOW</span> <span class="token keyword">REPLICA</span> <span class="token keyword">STATUS</span>\G</code></pre>
</div>
</li>
<li class="listitem">
<p>
Shut down the existing replica:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-terminal"><div class="docs-select-all right" id="sa46558841"><div class="copy-help left">Press ⌘+C to 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">mysqladmin</span> shutdown</code></pre>
</div>
</li>
<li class="listitem">
<p>
Copy the data directory from the existing replica to the new
replica, including the log files and relay log files. You
can do this by creating an archive using
<span class="command">
<strong>
tar
</strong>
</span>
or
<code class="literal">
WinZip
</code>
, or by
performing a direct copy using a tool such as
<span class="command">
<strong>
cp
</strong>
</span>
or
<span class="command">
<strong>
rsync
</strong>
</span>
.
</p>
<div class="important" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Important
</div>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
Before copying, verify that all the files relating to
the existing replica actually are stored in the data
directory. For example, the
<code class="literal">
InnoDB
</code>
system tablespace, undo tablespace, and redo log might
be stored in an alternative location.
<code class="literal">
InnoDB
</code>
tablespace files and
file-per-table tablespaces might have been created in
other directories. The binary logs and relay logs for
the replica might be in their own directories outside
the data directory. Check through the system variables
that are set for the existing replica and look for any
alternative paths that have been specified. If you
find any, copy these directories over as well.
</p>
</li>
<li class="listitem">
<p>
During copying, if files have been used for the
replication metadata repositories (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>
), ensure that you also
copy these files from the existing replica to the new
replica. If tables have been used for the repositories
(the default, the tables are in the data directory.
</p>
</li>
<li class="listitem">
<p>
After copying, delete the
<code class="filename">
auto.cnf
</code>
file from the copy of
the data directory on the new replica, so that the new
replica is started with a different generated server
UUID. The server UUID must be unique.
</p>
</li>
</ul>
</div>
</div>
<p>
A common problem that is encountered when adding new
replicas is that the new replica fails with a series of
warning and error messages like these:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-none"><div class="docs-select-all right" id="sa91986509"><div class="copy-help left">Press ⌘+C to 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">071118 16:44:10 [Warning] Neither --relay-log nor --relay-log-index were used; so
replication may break when this MySQL server acts as a replica and has his hostname
changed!! Please use '--relay-log=<em class="replaceable">new_replica_hostname</em>-relay-bin' to avoid this problem.
071118 16:44:10 [ERROR] Failed to open the relay log './<em class="replaceable">old_replica_hostname</em>-relay-bin.003525'
(relay_log_pos 22940879)
071118 16:44:10 [ERROR] Could not find target log during relay log initialization
071118 16:44:10 [ERROR] Failed to initialize the master info structure</code></pre>
</div>
<p>
This situation can occur if the
<a class="link" href="replication-options-replica.html#sysvar_relay_log">
<code class="literal">
relay_log
</code>
</a>
system variable
is not specified, as the relay log files contain the host
name as part of their file names. This is also true of the
relay log index file if the
<a class="link" href="replication-options-replica.html#sysvar_relay_log_index">
<code class="literal">
relay_log_index
</code>
</a>
system
variable is not used. For more information about these
variables, see
<a class="xref" href="replication-options.html" title="19.1.6 Replication and Binary Logging Options and Variables">
Section 19.1.6, “Replication and Binary Logging Options and Variables”
</a>
.
</p>
<p>
To avoid this problem, use the same value for
<a class="link" href="replication-options-replica.html#sysvar_relay_log">
<code class="literal">
relay_log
</code>
</a>
on the new
replica that was used on the existing replica. If this
option was not set explicitly on the existing replica, use
<code class="literal">
<em class="replaceable">
<code>
existing_replica_hostname
</code>
</em>
-relay-bin
</code>
.
If this is not possible, copy the existing replica's relay
log index file to the new replica and set the
<a class="link" href="replication-options-replica.html#sysvar_relay_log_index">
<code class="literal">
relay_log_index
</code>
</a>
system
variable on the new replica to match what was used on the
existing replica. If this option was not set explicitly on
the existing replica, use
<code class="literal">
<em class="replaceable">
<code>
existing_replica_hostname
</code>
</em>
-relay-bin.index
</code>
.
Alternatively, if you have already tried to start the new
replica after following the remaining steps in this section
and have encountered errors like those described previously,
then perform the following steps:
</p>
<div class="orderedlist">
<ol class="orderedlist" type="a">
<li class="listitem">
<p>
If you have not already done so, issue
<a class="link" href="stop-replica.html" title="15.4.2.5 STOP REPLICA Statement">
<code class="literal">
STOP REPLICA
</code>
</a>
on the new
replica.
</p>
<p>
If you have already started the existing replica again,
issue
<a class="link" href="stop-replica.html" title="15.4.2.5 STOP REPLICA Statement">
<code class="literal">
STOP REPLICA
</code>
</a>
on the
existing replica as well.
</p>
</li>
<li class="listitem">
<p>
Copy the contents of the existing replica's relay log
index file into the new replica's relay log index file,
making sure to overwrite any content already in the
file.
</p>
</li>
<li class="listitem">
<p>
Proceed with the remaining steps in this section.
</p>
</li>
</ol>
</div>
</li>
<li class="listitem">
<p>
When copying is complete, restart the existing replica.
</p>
</li>
<li class="listitem">
<p>
On the new replica, edit the configuration and give the new
replica a unique server ID (using the
<a class="link" href="replication-options.html#sysvar_server_id">
<code class="literal">
server_id
</code>
</a>
system variable)
that is not used by the source or any of the existing
replicas.
</p>
</li>
<li class="listitem">
<p>
Start the new replica server, ensuring that replication does
not start yet by specifying
<a class="link" href="replication-options-replica.html#option_mysqld_skip-replica-start">
<code class="option">
--skip-replica-start
</code>
</a>
. Use the
Performance Schema replication tables or issue
<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>
to
confirm that the new replica has the correct settings when
compared with the existing replica. Also display the server
ID and server UUID and verify that these are correct and
unique for the new replica.
</p>
</li>
<li class="listitem">
<p>
Start the replica threads by issuing a
<a class="link" href="start-replica.html" title="15.4.2.4 START REPLICA Statement">
<code class="literal">
START REPLICA
</code>
</a>
statement. The
new replica now uses the information in its connection
metadata repository to start the replication process.
</p>
</li>
</ol>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/innodb-restrictions-limitations.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h2 class="title">
<a name="innodb-restrictions-limitations">
</a>
17.22 InnoDB Restrictions and Limitations
</h2>
</div>
</div>
</div>
<a class="indexterm" name="idm46045148758752">
</a>
<a class="indexterm" name="idm46045148757264">
</a>
<a class="indexterm" name="idm46045148755776">
</a>
<a class="indexterm" name="idm46045148754288">
</a>
<p>
This section describes restrictions and limitations of the
<code class="literal">
InnoDB
</code>
storage engine.
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
You cannot create a table with a column name that matches the
name of an internal
<code class="literal">
InnoDB
</code>
column
(including
<code class="literal">
DB_ROW_ID
</code>
,
<code class="literal">
DB_TRX_ID
</code>
, and
<code class="literal">
DB_ROLL_PTR
</code>
. This restriction applies to
use of the names in any lettercase.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa1757328"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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> t1 <span class="token punctuation">(</span>c1 <span class="token datatype">INT</span><span class="token punctuation">,</span> db_row_id <span class="token datatype">INT</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 output">ERROR 1166 (42000)<span class="token punctuation">:</span> Incorrect column name 'db_row_id'</span></code></pre>
</div>
</li>
<li class="listitem">
<p>
<a class="link" href="show-table-status.html" title="15.7.7.38 SHOW TABLE STATUS Statement">
<code class="literal">
SHOW TABLE STATUS
</code>
</a>
does not
provide accurate statistics for
<code class="literal">
InnoDB
</code>
tables except for the physical size reserved by the table. The
row count is only a rough estimate used in SQL optimization.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
InnoDB
</code>
does not keep an internal count of
rows in a table because concurrent transactions might
<span class="quote">
“
<span class="quote">
see
</span>
”
</span>
different numbers of rows at the same time.
Consequently,
<code class="literal">
SELECT COUNT(*)
</code>
statements
only count rows visible to the current transaction.
</p>
<p>
For information about how
<code class="literal">
InnoDB
</code>
processes
<code class="literal">
SELECT COUNT(*)
</code>
statements, refer to the
<a class="link" href="aggregate-functions.html#function_count">
<code class="literal">
COUNT()
</code>
</a>
description in
<a class="xref" href="aggregate-functions.html" title="14.19.1 Aggregate Function Descriptions">
Section 14.19.1, “Aggregate Function Descriptions”
</a>
.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
ROW_FORMAT=COMPRESSED
</code>
is unsupported for
page sizes greater than 16KB.
</p>
</li>
<li class="listitem">
<p>
A MySQL instance using a particular
<code class="literal">
InnoDB
</code>
page size (
<a class="link" href="innodb-parameters.html#sysvar_innodb_page_size">
<code class="literal">
innodb_page_size
</code>
</a>
)
cannot use data files or log files from an instance that uses
a different page size.
</p>
</li>
<li class="listitem">
<p>
For limitations associated with importing tables using the
<span class="emphasis">
<em>
Transportable Tablespaces
</em>
</span>
feature, see
<a class="link" href="innodb-statistics-estimation.html" title="17.8.10.2 Configuring Non-Persistent Optimizer Statistics Parameters">
Table Import
Limitations
</a>
.
</p>
</li>
<li class="listitem">
<p>
For limitations associated with online DDL, see
<a class="xref" href="innodb-online-ddl-limitations.html" title="17.12.8 Online DDL Limitations">
Section 17.12.8, “Online DDL Limitations”
</a>
.
</p>
</li>
<li class="listitem">
<p>
For limitations associated with general tablespaces, see
<a class="xref" href="general-tablespaces.html#general-tablespaces-limitations" title="General Tablespace Limitations">
General Tablespace Limitations
</a>
.
</p>
</li>
<li class="listitem">
<p>
For limitations associated with data-at-rest encryption, see
<a class="xref" href="innodb-data-encryption.html#innodb-data-encryption-limitations" title="Encryption Limitations">
Encryption Limitations
</a>
.
</p>
</li>
</ul>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/multiple-windows-servers.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="multiple-windows-servers">
</a>
7.8.2 Running Multiple MySQL Instances on Windows
</h3>
</div>
</div>
</div>
<div class="toc">
<dl class="toc">
<dt>
<span class="section">
<a href="multiple-windows-command-line-servers.html">
7.8.2.1 Starting Multiple MySQL Instances at the Windows Command Line
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="multiple-windows-services.html">
7.8.2.2 Starting Multiple MySQL Instances as Windows Services
</a>
</span>
</dt>
</dl>
</div>
<p>
You can run multiple servers on Windows by starting them manually
from the command line, each with appropriate operating parameters,
or by installing several servers as Windows services and running
them that way. General instructions for running MySQL from the
command line or as a service are given in
<a class="xref" href="windows-installation.html" title="2.3 Installing MySQL on Microsoft Windows">
Section 2.3, “Installing MySQL on Microsoft Windows”
</a>
. The following sections
describe how to start each server with different values for those
options that must be unique per server, such as the data
directory. These options are listed in
<a class="xref" href="multiple-servers.html" title="7.8 Running Multiple MySQL Instances on One Machine">
Section 7.8, “Running Multiple MySQL Instances on One Machine”
</a>
.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/replication-rbr-usage.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="replication-rbr-usage">
</a>
19.2.1.2 Usage of Row-Based Logging and Replication
</h4>
</div>
</div>
</div>
<p>
MySQL uses statement-based logging (SBL), row-based logging
(RBL) or mixed-format logging. The type of binary log used
impacts the size and efficiency of logging. Therefore the choice
between row-based replication (RBR) or statement-based
replication (SBR) depends on your application and environment.
This section describes known issues when using a row-based
format log, and describes some best practices using it in
replication.
</p>
<p>
For additional information, see
<a class="xref" href="replication-formats.html" title="19.2.1 Replication Formats">
Section 19.2.1, “Replication Formats”
</a>
, and
<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>
.
</p>
<p>
For information about issues specific to NDB Cluster Replication
(which depends on row-based replication), see
<a class="xref" href="mysql-cluster-replication-issues.html" title="25.7.3 Known Issues in NDB Cluster Replication">
Section 25.7.3, “Known Issues in NDB Cluster Replication”
</a>
.
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<a name="replication-rbr-usage-temptables">
</a>
<b>
Row-based logging of temporary tables.
</b>
As noted in
<a class="xref" href="replication-features-temptables.html" title="19.5.1.31 Replication and Temporary Tables">
Section 19.5.1.31, “Replication and Temporary Tables”
</a>
,
temporary tables are not replicated when using row-based
or mixed format. For more information, 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>
.
</p>
<p>
Temporary tables are not replicated when using row-based or
mixed format because there is no need. In addition, because
temporary tables can be read only from the thread which
created them, there is seldom if ever any benefit obtained
from replicating them, even when using statement-based
format.
</p>
<p>
You can switch from statement-based to row-based binary
logging format at runtime even when temporary tables have
been created, but you cannot switch from row-based or mixed
format for binary logging to statement-based format at
runtime, due to any
<code class="literal">
CREATE TEMPORARY
TABLE
</code>
statements having been omitted from the
binary log in the previous mode.
</p>
<p>
The MySQL server tracks the logging mode that was in effect
when each temporary table was created. When a given client
session ends, the server logs a
<code class="literal">
DROP TEMPORARY
TABLE IF EXISTS
</code>
statement for each temporary table
that still exists and was created when statement-based
binary logging was in use. If row-based or mixed format
binary logging was in use when the table was created, the
<code class="literal">
DROP TEMPORARY TABLE IF EXISTS
</code>
statement
is not logged.
</p>
<p>
Nontransactional DML statements involving temporary tables
are allowed when using
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_format">
<code class="literal">
binlog_format=ROW
</code>
</a>
, as long
as any nontransactional tables affected by the statements
are temporary tables.
</p>
</li>
<li class="listitem">
<p>
<b>
RBL and synchronization of nontransactional tables.
</b>
When many rows are affected, the set of changes is split
into several events; when the statement commits, all of
these events are written to the binary log. When executing
on the replica, a table lock is taken on all tables
involved, and then the rows are applied in batch mode.
Depending on the engine used for the replica's copy of the
table, this may or may not be effective.
</p>
</li>
<li class="listitem">
<p>
<b>
Latency and binary log size.
</b>
RBL writes changes for each row to the binary log and so
its size can increase quite rapidly. This can
significantly increase the time required to make changes
on the replica that match those on the source. You should
be aware of the potential for this delay in your
applications.
</p>
</li>
<li class="listitem">
<p>
<b>
Reading the binary log.
</b>
<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>
displays row-based events
in the binary log using the
<a class="link" href="binlog.html" title="15.7.8.1 BINLOG Statement">
<code class="literal">
BINLOG
</code>
</a>
statement. This
statement displays an event as a base 64-encoded string,
the meaning of which is not evident. When invoked with the
<a class="link" href="mysqlbinlog.html#option_mysqlbinlog_base64-output">
<code class="option">
--base64-output=DECODE-ROWS
</code>
</a>
and
<a class="link" href="mysqlbinlog.html#option_mysqlbinlog_verbose">
<code class="option">
--verbose
</code>
</a>
options,
<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>
formats the contents of the
binary log to be human readable. When binary log events
were written in row-based format and you want to read or
recover from a replication or database failure you can use
this command to read contents of the binary log. For more
information, see
<a class="xref" href="mysqlbinlog-row-events.html" title="6.6.9.2 mysqlbinlog Row Event Display">
Section 6.6.9.2, “mysqlbinlog Row Event Display”
</a>
.
</p>
</li>
<li class="listitem">
<p>
<b>
Binary log execution errors and replica execution mode.
</b>
Using
<a class="link" href="replication-options-replica.html#sysvar_replica_exec_mode">
<code class="literal">
replica_exec_mode=IDEMPOTENT
</code>
</a>
is generally only useful with MySQL NDB Cluster
replication, for which
<code class="literal">
IDEMPOTENT
</code>
is
the default value. (See
<a class="xref" href="mysql-cluster-replication-multi-source.html" title="25.7.10 NDB Cluster Replication: Bidirectional and Circular Replication">
Section 25.7.10, “NDB Cluster Replication: Bidirectional and Circular Replication”
</a>
).
When
<code class="literal">
replica_exec_mode
</code>
is
<code class="literal">
IDEMPOTENT
</code>
, a failure to apply changes
from RBL because the original row cannot be found does not
trigger an error or cause replication to fail. This means
that it is possible that updates are not applied on the
replica, so that the source and replica are no longer
synchronized. Latency issues and use of nontransactional
tables with RBR when
<a class="link" href="replication-options-replica.html#sysvar_replica_exec_mode">
<code class="literal">
replica_exec_mode
</code>
</a>
is
<code class="literal">
IDEMPOTENT
</code>
can cause the source and
replica to diverge even further. For more information
about
<a class="link" href="replication-options-replica.html#sysvar_replica_exec_mode">
<code class="literal">
replica_exec_mode
</code>
</a>
,
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>
<p>
For other scenarios, setting
<a class="link" href="replication-options-replica.html#sysvar_replica_exec_mode">
<code class="literal">
replica_exec_mode
</code>
</a>
to
<code class="literal">
STRICT
</code>
is normally sufficient; this is
the default value for storage engines other than
<a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4">
<code class="literal">
NDB
</code>
</a>
.
</p>
</li>
<li class="listitem">
<p>
<b>
Filtering based on server ID not supported.
</b>
You can filter based on server ID using the
<a class="link" href="change-replication-source-to.html#crs-opt-ignore_server_ids">
<code class="literal">
IGNORE_SERVER_IDS
</code>
</a>
option
for
<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>
. This option works with both the
statement-based and row-based logging formats, but cannot
be used when
<a class="link" href="replication-options-gtids.html#sysvar_gtid_mode">
<code class="literal">
gtid_mode=ON
</code>
</a>
. Another
method to filter out changes on some replicas is to use a
<code class="literal">
WHERE
</code>
clause that includes the relation
<code class="literal">
@@server_id <>
<em class="replaceable">
<code>
id_value
</code>
</em>
</code>
clause with
<a class="link" href="update.html" title="15.2.17 UPDATE Statement">
<code class="literal">
UPDATE
</code>
</a>
and
<a class="link" href="delete.html" title="15.2.2 DELETE Statement">
<code class="literal">
DELETE
</code>
</a>
statements. For
example,
<code class="literal">
WHERE @@server_id <> 1
</code>
.
However, this does not work correctly with row-based
logging. To use the
<a class="link" href="replication-options.html#sysvar_server_id">
<code class="literal">
server_id
</code>
</a>
system variable
for statement filtering, use statement-based logging.
</p>
</li>
<li class="listitem">
<p>
<b>
RBL, nontransactional tables, and stopped replicas.
</b>
When using row-based logging, if the replica server is
stopped while a replica thread is updating a
nontransactional table, the replica database can reach an
inconsistent state. For this reason, it is recommended
that you use a transactional storage engine such as
<a class="link" href="innodb-storage-engine.html" title="Chapter 17 The InnoDB Storage Engine">
<code class="literal">
InnoDB
</code>
</a>
for all tables
replicated using the row-based format. Use of
<a class="link" href="stop-replica.html" title="15.4.2.5 STOP REPLICA Statement">
<code class="literal">
STOP REPLICA
</code>
</a>
or
<a class="link" href="stop-replica.html" title="15.4.2.5 STOP REPLICA Statement">
<code class="literal">
STOP REPLICA
SQL_THREAD
</code>
</a>
prior to shutting down the replica
MySQL server helps prevent issues from occurring, and is
always recommended regardless of the logging format or
storage engine you use.
</p>
</li>
</ul>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/performance-schema-event-tables.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h2 class="title">
<a name="performance-schema-event-tables">
</a>
29.9 Performance Schema Tables for Current and Historical Events
</h2>
</div>
</div>
</div>
<p>
For wait, stage, statement, and transaction events, the
Performance Schema can monitor and store current events. In
addition, when events end, the Performance Schema can store them
in history tables. For each event type, the Performance Schema
uses three tables for storing current and historical events. The
tables have names of the following forms, where
<em class="replaceable">
<code>
xxx
</code>
</em>
indicates the event type
(
<code class="literal">
waits
</code>
,
<code class="literal">
stages
</code>
,
<code class="literal">
statements
</code>
,
<code class="literal">
transactions
</code>
):
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<code class="literal">
events_
<em class="replaceable">
<code>
xxx
</code>
</em>
_current
</code>
:
The
<span class="quote">
“
<span class="quote">
current events
</span>
”
</span>
table stores the current
monitored event for each thread (one row per thread).
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
events_
<em class="replaceable">
<code>
xxx
</code>
</em>
_history
</code>
:
The
<span class="quote">
“
<span class="quote">
recent history
</span>
”
</span>
table stores the most recent
events that have ended per thread (up to a maximum number of
rows per thread).
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
events_
<em class="replaceable">
<code>
xxx
</code>
</em>
_history_long
</code>
:
The
<span class="quote">
“
<span class="quote">
long history
</span>
”
</span>
table stores the most recent
events that have ended globally (across all threads, up to a
maximum number of rows per table).
</p>
</li>
</ul>
</div>
<p>
The
<code class="literal">
_current
</code>
table for each event type contains
one row per thread, so there is no system variable for configuring
its maximum size. The Performance Schema autosizes the history
tables, or the sizes can be configured explicitly at server
startup using table-specific system variables, as indicated in the
sections that describe the individual history tables. Typical
autosized values are 10 rows per thread for
<code class="literal">
_history
</code>
tables, and 10,000 rows total for
<code class="literal">
_history_long
</code>
tables.
</p>
<p>
For each event type, the
<code class="literal">
_current
</code>
,
<code class="literal">
_history
</code>
, and
<code class="literal">
_history_long
</code>
tables have the same columns. The
<code class="literal">
_current
</code>
and
<code class="literal">
_history
</code>
tables have the same indexing. The
<code class="literal">
_history_long
</code>
table has no indexing.
</p>
<p>
The
<code class="literal">
_current
</code>
tables show what is currently
happening within the server. When a current event ends, it is
removed from its
<code class="literal">
_current
</code>
table.
</p>
<p>
The
<code class="literal">
_history
</code>
and
<code class="literal">
_history_long
</code>
tables show what has happened in
the recent past. When the history tables become full, old events
are discarded as new events are added. Rows expire from the
<code class="literal">
_history
</code>
and
<code class="literal">
_history_long
</code>
tables in different ways because the tables serve different
purposes:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<code class="literal">
_history
</code>
is meant to investigate individual
threads, independently of the global server load.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
_history_long
</code>
is meant to investigate the
server globally, not each thread.
</p>
</li>
</ul>
</div>
<p>
The difference between the two types of history tables relates to
the data retention policy. Both tables contains the same data when
an event is first seen. However, data within each table expires
differently over time, so that data might be preserved for a
longer or shorter time in each table:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
For
<code class="literal">
_history
</code>
, when the table contains the
maximum number of rows for a given thread, the oldest thread
row is discarded when a new row for that thread is added.
</p>
</li>
<li class="listitem">
<p>
For
<code class="literal">
_history_long
</code>
, when the table becomes
full, the oldest row is discarded when a new row is added,
regardless of which thread generated either row.
</p>
</li>
</ul>
</div>
<p>
When a thread ends, all its rows are discarded from the
<code class="literal">
_history
</code>
table but not from the
<code class="literal">
_history_long
</code>
table.
</p>
<p>
The following example illustrates the differences in how events
are added to and discarded from the two types of history tables.
The principles apply equally to all event types. The example is
based on these assumptions:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
The Performance Schema is configured to retain 10 rows per
thread in the
<code class="literal">
_history
</code>
table and 10,000
rows total in the
<code class="literal">
_history_long
</code>
table.
</p>
</li>
<li class="listitem">
<p>
Thread A generates 1 event per second.
</p>
<p>
Thread B generates 100 events per second.
</p>
</li>
<li class="listitem">
<p>
No other threads are running.
</p>
</li>
</ul>
</div>
<p>
After 5 seconds of execution:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
A and B have generated 5 and 500 events, respectively.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
_history
</code>
contains 5 rows for A and 10 rows
for B. Because storage per thread is limited to 10 rows, no
rows have been discarded for A, whereas 490 rows have been
discarded for B.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
_history_long
</code>
contains 5 rows for A and 500
rows for B. Because the table has a maximum size of 10,000
rows, no rows have been discarded for either thread.
</p>
</li>
</ul>
</div>
<p>
After 5 minutes (300 seconds) of execution:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
A and B have generated 300 and 30,000 events, respectively.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
_history
</code>
contains 10 rows for A and 10 rows
for B. Because storage per thread is limited to 10 rows, 290
rows have been discarded for A, whereas 29,990 rows have been
discarded for B. Rows for A include data up to 10 seconds old,
whereas rows for B include data up to only .1 seconds old.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
_history_long
</code>
contains 10,000 rows. Because
A and B together generate 101 events per second, the table
contains data up to approximately 10,000/101 = 99 seconds old,
with a mix of rows approximately 100 to 1 from B as opposed to
A.
</p>
</li>
</ul>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/insert-select.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="insert-select">
</a>
15.2.7.1 INSERT ... SELECT Statement
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045182259824">
</a>
<a class="indexterm" name="idm46045182258784">
</a>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa76747507"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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 punctuation">[</span><span class="token keyword">LOW_PRIORITY</span> <span class="token operator">|</span> <span class="token keyword">HIGH_PRIORITY</span><span class="token punctuation">]</span> <span class="token punctuation">[</span><span class="token keyword">IGNORE</span><span class="token punctuation">]</span>
<span class="token punctuation">[</span><span class="token keyword">INTO</span><span class="token punctuation">]</span> <em class="replaceable">tbl_name</em>
<span class="token punctuation">[</span><span class="token keyword">PARTITION</span> <span class="token punctuation">(</span><em class="replaceable">partition_name</em> <span class="token punctuation">[</span><span class="token punctuation">,</span> <em class="replaceable">partition_name</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 punctuation">[</span><span class="token punctuation">(</span><em class="replaceable">col_name</em> <span class="token punctuation">[</span><span class="token punctuation">,</span> <em class="replaceable">col_name</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">SELECT</span> <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span>
<span class="token operator">|</span> <span class="token keyword">TABLE</span> <span class="token keyword"><em class="replaceable">table_name</em></span>
<span class="token operator">|</span> <span class="token keyword">VALUES</span> <em class="replaceable">row_constructor_list</em>
}
<span class="token punctuation">[</span><span class="token keyword">ON</span> <span class="token keyword">DUPLICATE</span> <span class="token keyword">KEY</span> <span class="token keyword">UPDATE</span> <em class="replaceable">assignment_list</em><span class="token punctuation">]</span>
<span class="token keyword"><em class="replaceable">value</em></span>:
{<em class="replaceable">expr</em> <span class="token operator">|</span> <span class="token keyword">DEFAULT</span>}
<em class="replaceable">value_list</em>:
<span class="token keyword"><em class="replaceable">value</em></span> <span class="token punctuation">[</span><span class="token punctuation">,</span> <span class="token keyword"><em class="replaceable">value</em></span><span class="token punctuation">]</span> <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span>
<em class="replaceable">row_constructor_list</em>:
<span class="token keyword">ROW</span><span class="token punctuation">(</span><em class="replaceable">value_list</em><span class="token punctuation">)</span><span class="token punctuation">[</span><span class="token punctuation">,</span> <span class="token keyword">ROW</span><span class="token punctuation">(</span><em class="replaceable">value_list</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 punctuation">.</span><span class="token punctuation">]</span>
<em class="replaceable">assignment</em>:
<em class="replaceable">col_name</em> <span class="token operator">=</span>
<span class="token keyword"><em class="replaceable">value</em></span>
<span class="token operator">|</span> <span class="token punctuation">[</span><em class="replaceable">row_alias</em><span class="token punctuation">.</span><span class="token punctuation">]</span><em class="replaceable">col_name</em>
<span class="token operator">|</span> <span class="token punctuation">[</span><em class="replaceable">tbl_name</em><span class="token punctuation">.</span><span class="token punctuation">]</span><em class="replaceable">col_name</em>
<span class="token operator">|</span> <span class="token punctuation">[</span><em class="replaceable">row_alias</em><span class="token punctuation">.</span><span class="token punctuation">]</span><em class="replaceable">col_alias</em>
<em class="replaceable">assignment_list</em>:
<em class="replaceable">assignment</em> <span class="token punctuation">[</span><span class="token punctuation">,</span> <em class="replaceable">assignment</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>
With
<a class="link" href="insert-select.html" title="15.2.7.1 INSERT ... SELECT Statement">
<code class="literal">
INSERT ...
SELECT
</code>
</a>
, you can quickly insert many rows into a table
from the result of a
<a class="link" href="select.html" title="15.2.13 SELECT Statement">
<code class="literal">
SELECT
</code>
</a>
statement, which can select from one or many tables. For
example:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa30096150"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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> tbl_temp2 <span class="token punctuation">(</span>fld_id<span class="token punctuation">)</span>
<span class="token keyword">SELECT</span> tbl_temp1<span class="token punctuation">.</span>fld_order_id
<span class="token keyword">FROM</span> tbl_temp1 <span class="token keyword">WHERE</span> tbl_temp1<span class="token punctuation">.</span>fld_order_id <span class="token operator">></span> <span class="token number">100</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
<a class="link" href="table.html" title="15.2.16 TABLE Statement">
<code class="literal">
TABLE
</code>
</a>
statement in place of
<a class="link" href="select.html" title="15.2.13 SELECT Statement">
<code class="literal">
SELECT
</code>
</a>
, as shown here:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa39536678"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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> ta <span class="token keyword">TABLE</span> tb<span class="token punctuation">;</span></code></pre>
</div>
<p>
<code class="literal">
TABLE tb
</code>
is equivalent to
<code class="literal">
SELECT *
FROM tb
</code>
. It can be useful when inserting all columns
from the source table into the target table, and no filtering
with WHERE is required. In addition, the rows from
<a class="link" href="table.html" title="15.2.16 TABLE Statement">
<code class="literal">
TABLE
</code>
</a>
can be ordered by one or
more columns using
<code class="literal">
ORDER BY
</code>
, and the number
of rows inserted can be limited using a
<code class="literal">
LIMIT
</code>
clause. For more information, see
<a class="xref" href="table.html" title="15.2.16 TABLE Statement">
Section 15.2.16, “TABLE Statement”
</a>
.
</p>
<p>
The following conditions hold for
<a class="link" href="insert-select.html" title="15.2.7.1 INSERT ... SELECT Statement">
<code class="literal">
INSERT ...
SELECT
</code>
</a>
statements, and, except where noted, for
<code class="literal">
INSERT ... TABLE
</code>
as well:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
Specify
<code class="literal">
IGNORE
</code>
to ignore rows that would
cause duplicate-key violations.
</p>
</li>
<li class="listitem">
<p>
The target table of the
<a class="link" href="insert.html" title="15.2.7 INSERT Statement">
<code class="literal">
INSERT
</code>
</a>
statement may appear
in the
<code class="literal">
FROM
</code>
clause of the
<a class="link" href="select.html" title="15.2.13 SELECT Statement">
<code class="literal">
SELECT
</code>
</a>
part of the query, or
as the table named by
<a class="link" href="table.html" title="15.2.16 TABLE Statement">
<code class="literal">
TABLE
</code>
</a>
.
However, you cannot insert into a table and select from the
same table in a subquery.
</p>
<p>
When selecting from and inserting into the same table, MySQL
creates an internal temporary table to hold the rows from
the
<a class="link" href="select.html" title="15.2.13 SELECT Statement">
<code class="literal">
SELECT
</code>
</a>
and then inserts
those rows into the target table. However, you cannot use
<code class="literal">
INSERT INTO t ... SELECT ... FROM t
</code>
when
<code class="literal">
t
</code>
is a
<code class="literal">
TEMPORARY
</code>
table, because
<code class="literal">
TEMPORARY
</code>
tables cannot be
referred to twice in the same statement. For the same
reason, you cannot use
<code class="literal">
INSERT INTO t ... TABLE
t
</code>
when
<code class="literal">
t
</code>
is a temporary table.
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>
, and
<a class="xref" href="temporary-table-problems.html" title="B.3.6.2 TEMPORARY Table Problems">
Section B.3.6.2, “TEMPORARY Table Problems”
</a>
.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
AUTO_INCREMENT
</code>
columns work as usual.
</p>
</li>
<li class="listitem">
<p>
To ensure that the binary log can be used to re-create the
original tables, MySQL does not permit concurrent inserts
for
<a class="link" href="insert-select.html" title="15.2.7.1 INSERT ... SELECT Statement">
<code class="literal">
INSERT
... SELECT
</code>
</a>
or
<code class="literal">
INSERT ... TABLE
</code>
statements (see
<a class="xref" href="concurrent-inserts.html" title="10.11.3 Concurrent Inserts">
Section 10.11.3, “Concurrent Inserts”
</a>
).
</p>
</li>
<li class="listitem">
<p>
To avoid ambiguous column reference problems when the
<a class="link" href="select.html" title="15.2.13 SELECT Statement">
<code class="literal">
SELECT
</code>
</a>
and the
<a class="link" href="insert.html" title="15.2.7 INSERT Statement">
<code class="literal">
INSERT
</code>
</a>
refer to the same
table, provide a unique alias for each table used in the
<a class="link" href="select.html" title="15.2.13 SELECT Statement">
<code class="literal">
SELECT
</code>
</a>
part, and qualify
column names in that part with the appropriate alias.
</p>
<p>
The
<a class="link" href="table.html" title="15.2.16 TABLE Statement">
<code class="literal">
TABLE
</code>
</a>
statement does not
support aliases.
</p>
</li>
</ul>
</div>
<p>
You can explicitly select which partitions or subpartitions (or
both) of the source or target table (or both) are to be used
with a
<code class="literal">
PARTITION
</code>
clause following the name of
the table. When
<code class="literal">
PARTITION
</code>
is used with the
name of the source table in the
<a class="link" href="select.html" title="15.2.13 SELECT Statement">
<code class="literal">
SELECT
</code>
</a>
portion of the statement,
rows are selected only from the partitions or subpartitions
named in its partition list. When
<code class="literal">
PARTITION
</code>
is used with the name of the target table for the
<a class="link" href="insert.html" title="15.2.7 INSERT Statement">
<code class="literal">
INSERT
</code>
</a>
portion of the statement,
it must be possible to insert all rows selected into the
partitions or subpartitions named in the partition list
following the option. Otherwise, the
<code class="literal">
INSERT ...
SELECT
</code>
statement fails. For more information and
examples, see
<a class="xref" href="partitioning-selection.html" title="26.5 Partition Selection">
Section 26.5, “Partition Selection”
</a>
.
</p>
<p>
<a class="link" href="table.html" title="15.2.16 TABLE Statement">
<code class="literal">
TABLE
</code>
</a>
does not support a
<code class="literal">
PARTITION
</code>
clause.
</p>
<p>
For
<a class="link" href="insert-on-duplicate.html" title="15.2.7.2 INSERT ... ON DUPLICATE KEY UPDATE Statement">
<code class="literal">
INSERT
... SELECT
</code>
</a>
statements, see
<a class="xref" href="insert-on-duplicate.html" title="15.2.7.2 INSERT ... ON DUPLICATE KEY UPDATE Statement">
Section 15.2.7.2, “INSERT ... ON DUPLICATE KEY UPDATE Statement”
</a>
for conditions under which
the
<a class="link" href="select.html" title="15.2.13 SELECT Statement">
<code class="literal">
SELECT
</code>
</a>
columns can be
referred to in an
<code class="literal">
ON DUPLICATE KEY UPDATE
</code>
clause. This also works for
<code class="literal">
INSERT ... TABLE
</code>
.
</p>
<p>
The order in which a
<a class="link" href="select.html" title="15.2.13 SELECT Statement">
<code class="literal">
SELECT
</code>
</a>
or
<a class="link" href="table.html" title="15.2.16 TABLE Statement">
<code class="literal">
TABLE
</code>
</a>
statement with no
<code class="literal">
ORDER BY
</code>
clause returns rows is
nondeterministic. This means that, when using replication, there
is no guarantee that such a
<a class="link" href="select.html" title="15.2.13 SELECT Statement">
<code class="literal">
SELECT
</code>
</a>
returns rows in the same
order on the source and the replica, which can lead to
inconsistencies between them. To prevent this from occurring,
always write
<code class="literal">
INSERT ... SELECT
</code>
or
<code class="literal">
INSERT ... TABLE
</code>
statements that are to be
replicated using an
<code class="literal">
ORDER BY
</code>
clause that
produces the same row order on the source and the replica. See
also
<a class="xref" href="replication-features-limit.html" title="19.5.1.18 Replication and LIMIT">
Section 19.5.1.18, “Replication and LIMIT”
</a>
.
</p>
<p>
Due to this issue,
<a class="link" href="insert-on-duplicate.html" title="15.2.7.2 INSERT ... ON DUPLICATE KEY UPDATE Statement">
<code class="literal">
INSERT ...
SELECT ON DUPLICATE KEY UPDATE
</code>
</a>
and
<a class="link" href="insert-select.html" title="15.2.7.1 INSERT ... SELECT Statement">
<code class="literal">
INSERT IGNORE ...
SELECT
</code>
</a>
statements are flagged as unsafe for
statement-based replication. Such statements produce a warning
in the error log when using statement-based mode and are written
to the binary log using the row-based format when using
<code class="literal">
MIXED
</code>
mode. (Bug #11758262, Bug #50439)
</p>
<p>
See also
<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>
.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/mysql-cluster-what-is-new.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="mysql-cluster-what-is-new">
</a>
25.2.4 What is New in MySQL NDB Cluster 8.4
</h3>
</div>
</div>
</div>
<a class="indexterm" name="idm46045124080864">
</a>
<a class="indexterm" name="idm46045124079792">
</a>
<a class="indexterm" name="idm46045124078704">
</a>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<a class="xref" href="mysql-cluster-what-is-new.html#mysql-cluster-what-is-new-8-4" title="What is New in NDB Cluster 8.4">
What is New in NDB Cluster 8.4
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="mysql-cluster-what-is-new.html#mysql-cluster-innovation-8.x-changes" title="Changes in NDB 8.x Innovation Releases">
Changes in NDB 8.x Innovation Releases
</a>
</p>
</li>
</ul>
</div>
<p>
The following sections describe changes in the implementation of
MySQL NDB Cluster in NDB Cluster 8.4.3, as compared to
earlier release series. NDB Cluster 8.4 is available as a
Development release for preview and testing of new features
currently under development. For production, please use NDB 8.0;
for more information, see
<a class="ulink" href="/doc/refman/8.0/en/mysql-cluster.html" target="_top">
MySQL NDB Cluster 8.0
</a>
. NDB Cluster 7.6 and
7.5 are previous GA releases still supported in production,
although we recommend that new deployments for production use
MySQL NDB Cluster 8.0.
</p>
<p>
NDB Cluster 7.4 and 7.3 were previous GA releases which have
reached their end of life; they are no longer supported or
maintained.
</p>
<h4>
<a name="mysql-cluster-what-is-new-8-4">
</a>
What is New in NDB Cluster 8.4
</h4>
<p>
Major changes and new features in NDB Cluster 8.4
which are likely to be of interest are listed here:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<b>
ndbinfo transporter_details table.
</b>
The
<a class="link" href="mysql-cluster-ndbinfo-transporter-details.html" title="25.6.17.65 The ndbinfo transporter_details Table">
<code class="literal">
transporter_details
</code>
</a>
table provides information about individual transporters
used in an NDB cluster. It is otherwise similar to the
<code class="literal">
ndbinfo
</code>
<a class="link" href="mysql-cluster-ndbinfo-transporters.html" title="25.6.17.66 The ndbinfo transporters Table">
<code class="literal">
transporters
</code>
</a>
table, which
provides such information in aggregate form.
</p>
<p>
NDB 8.4.0 provides additional columns as compared to the
version introduced in NDB 8.0. These new columns, along with
brief dscriptions of each, are listed here:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
<code class="literal">
sendbuffer_used_bytes
</code>
: Number of bytes
of signal data currently stored pending send using this
transporter.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
sendbuffer_max_used_bytes
</code>
: Historical
maximum number of bytes of signal data stored pending send
using this transporter. Reset when the transporter
connects.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
sendbuffer_alloc_bytes
</code>
: Number of bytes
of send buffer currently allocated to store pending send
bytes for this transporter. Send buffer memory is
allocated in large blocks which may be sparsely used.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
sendbuffer_max_alloc_bytes
</code>
: Historical
maximum number of bytes of send buffer allocated to store
pending send bytes for this transporter.
</p>
</li>
</ul>
</div>
<p>
NDB 8.4.1 adds a
<code class="literal">
type
</code>
column, which
displays the transport's connection type
(
<code class="literal">
TCP
</code>
or
<code class="literal">
SHM
</code>
).
</p>
<p>
See
<a class="xref" href="mysql-cluster-ndbinfo-transporter-details.html" title="25.6.17.65 The ndbinfo transporter_details Table">
Section 25.6.17.65, “The ndbinfo transporter_details Table”
</a>
,
for more information.
</p>
</li>
<li class="listitem">
<p>
<b>
NDB Replication: Filtering of unused updates.
</b>
Previously, when SQL nodes performing binary logging used
<a class="link" href="replication-options-binary-log.html#sysvar_log_replica_updates">
<code class="literal">
log_replica_updates=OFF
</code>
</a>
,
any replicated updates which were applied on a replica NDB
cluster were sent on to the SQL nodes performing binary
logging. These updates were not actually applied or used for
any other purpose; this entailed unnecessary network traffic
and consumption of resources.
</p>
<p>
In NDB 8.4.0 and later, updates applied on the replica SQL
node are filtered out on this node, and are no longer sent
onward to any other SQL nodes. Updates that do not trigger any
logging are also no longer sent by the replica.
</p>
</li>
<li class="listitem">
<p>
<b>
Per-session binary log transaction cache sizing.
</b>
<code class="literal">
NDB
</code>
8.4.3 adds the
<a class="link" href="mysql-cluster-options-variables.html#sysvar_ndb_log_cache_size">
<code class="literal">
ndb_log_cache_size
</code>
</a>
server
system variable, which makes it possible to set the size of
the transaction cache used for writing the binary log. This
enables use of a large cache for logging NDB transactions,
and (using
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_cache_size">
<code class="literal">
binlog_cache_size
</code>
</a>
) a
smaller cache for logging other transactions, thus making
more efficient use of resources.
</p>
</li>
<li class="listitem">
<p>
<b>
Ndb.cfg file deprecation.
</b>
Use of an
<code class="filename">
Ndb.cfg
</code>
file for setting the
connection string for an NDB process was not well documented
or supported. As of NDB 8.4.3, use of this file is now
formally deprecated; you should expect support for it to be
removed in a future release of MySQL Cluster.
</p>
</li>
</ul>
</div>
<p>
MySQL Cluster Manager has an advanced command-line interface that can simplify
many complex NDB Cluster management tasks. See
<a class="ulink" href="/doc/mysql-cluster-manager/8.4/en/" target="_top">
MySQL Cluster Manager 8.4.3 User Manual
</a>
, for more information.
</p>
<h4>
<a name="mysql-cluster-innovation-8.x-changes">
</a>
Changes in NDB 8.x Innovation Releases
</h4>
<p>
New features and major changes in NDB Cluster Innovation releases
(8.1, 8.2, 8.3) compared with NDB 8.0 which are likely to be of
interest are listed here:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<b>
TLS for cluster node communications.
</b>
NDB Cluster 8.3 and later provides support for network
communications secured by Transport Layer Security (TLS) and
Internet Public Key Infrastructure (PKI) to authenticate and
encrypt connections between NDB nodes, and between the NDB
management server and its clients; TLS is applied to the NDB
Transporter Protocol, and to the NDB Management Protocol.
</p>
<p>
This feature uses TLS mutual authentication, in which a
node's own certificate file contains the chain of trust
which the node uses to validate the certificates of its peers.
When TLS is enabled on the cluster, data and management nodes
use TLS to perform the following tasks:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
Mutually authenticate
<code class="literal">
NDB
</code>
clients and
servers at the network level, preventing unprivileged
access as a client or server
</p>
</li>
<li class="listitem">
<p>
Encrypt data transfer, avoiding data eavesdropping,
modification, and man-in-the-middle attacks
</p>
</li>
</ul>
</div>
<p>
Connections that use the MySQL client protocol employ MySQL
user authentication, and may use TLS (including optional
mutual TLS) as described elsewhere in this Manual; see
<a class="xref" href="encrypted-connections.html" title="8.3 Using Encrypted Connections">
Section 8.3, “Using Encrypted Connections”
</a>
, for more information.
</p>
<p>
<code class="literal">
NDB
</code>
implements a new tool
<a class="link" href="mysql-cluster-programs-ndb-sign-keys.html" title="25.5.28 ndb_sign_keys — Create, Sign, and Manage TLS Keys and Certificates for NDB Cluster">
<span class="command">
<strong>
ndb_sign_keys
</strong>
</span>
</a>
which can be used to create
and manage CA, certificate files, and keys. You can generate a
set of keys and certificates for all nodes in a cluster with a
given configuration file using
<a class="link" href="mysql-cluster-programs-ndb-sign-keys.html" title="25.5.28 ndb_sign_keys — Create, Sign, and Manage TLS Keys and Certificates for NDB Cluster">
<span class="command">
<strong>
ndb_sign_keys
</strong>
</span>
</a>
<a class="link" href="mysql-cluster-programs-ndb-sign-keys.html#option_ndb_sign_keys_create-key">
<code class="option">
--create-key
</code>
</a>
.
</p>
<p>
Using
<a class="link" href="mysql-cluster-programs-ndb-sign-keys.html" title="25.5.28 ndb_sign_keys — Create, Sign, and Manage TLS Keys and Certificates for NDB Cluster">
<span class="command">
<strong>
ndb_sign_keys
</strong>
</span>
</a>
, a node certificate can
be bound to a particular hostname, made to expire on a given
date, and be associated with a given node type, so that
clients are distinct from servers, and management servers from
data nodes. (Every NDB TLS certificate can be used for MGM
client connections.) Private keys are created in place, so
that copying of files containing private keys is minimized.
Both private keys and certificates are labeled as either
active or pending;
<a class="link" href="mysql-cluster-programs-ndb-sign-keys.html" title="25.5.28 ndb_sign_keys — Create, Sign, and Manage TLS Keys and Certificates for NDB Cluster">
<span class="command">
<strong>
ndb_sign_keys
</strong>
</span>
</a>
also
provides help with rotating keys to allow for pending keys to
replace active keys before the active keys expire.
</p>
<p>
Testing of node TLS connections can be done from the system
shell using
<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 with
<a class="link" href="mysql-cluster-programs-ndb-mgm.html#option_ndb_mgm_test-tls">
<code class="option">
--test-tls
</code>
</a>
, or within 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 using the
<a class="link" href="mysql-cluster-mgm-client-commands.html#ndbclient-tls-info">
<code class="literal">
TLS INFO
</code>
</a>
command. You can
obtain information about certificates used by cluster nodes by
checking the
<code class="literal">
ndbinfo
</code>
<a class="link" href="mysql-cluster-ndbinfo-certificates.html" title="25.6.17.6 The ndbinfo certificates Table">
<code class="literal">
certificates
</code>
</a>
table.
</p>
<p>
To enforce a requirement for TLS, set the client option
<code class="option">
ndb-mgm-tls=strict
</code>
in
<code class="filename">
my.cnf
</code>
on each cluster host, then set
<a class="link" href="mysql-cluster-mgm-definition.html#ndbparam-mgmd-requiretls">
<code class="literal">
RequireTls=true
</code>
</a>
in the
<code class="literal">
[mgm default]
</code>
section of the cluster
<code class="filename">
config.ini
</code>
file, and set
<a class="link" href="mysql-cluster-ndbd-definition.html#ndbparam-ndbd-requiretls">
<code class="literal">
RequireTls=true
</code>
</a>
in the
<code class="literal">
[ndbd default]
</code>
section of the configuration
file as well. Then perform a rolling restart of the cluster,
restarting the management server with
<a class="link" href="mysql-cluster-programs-ndb-mgmd.html#option_ndb_mgmd_reload">
<code class="option">
--reload
</code>
</a>
<a class="link" href="mysql-cluster-programs-ndb-mgmd.html#option_ndb_mgmd_config-file">
<code class="option">
--config-file
</code>
</a>
.
</p>
<p>
Use of TLS connections is also supported in NDB Cluster API
applications in NDB 8.3 and later. For information about MGM
API support, see
<a class="ulink" href="/doc/ndbapi/en/mgm-functions-tls.html" target="_top">
TLS Functions
</a>
. The NDB
API
<a class="ulink" href="/doc/ndbapi/en/ndb-ndb-cluster-connection.html" target="_top">
<code class="literal">
Ndb_cluster_connection
</code>
</a>
class adds
<a class="ulink" href="/doc/ndbapi/en/ndb-ndb-cluster-connection.html#ndb-ndb-cluster-connection-configure-tls" target="_top">
<code class="literal">
configure_tls()
</code>
</a>
<a class="ulink" href="/doc/ndbapi/en/ndb-ndb-cluster-connection.html#ndb-ndb-cluster-connection-get-tls-certificate-path" target="_top">
<code class="literal">
get_tls_certificate_path()
</code>
</a>
methods for setting up TLS connections by clients.
</p>
<p>
For more information, see
<a class="xref" href="mysql-cluster-tls.html" title="25.6.15 TLS Link Encryption for NDB Cluster">
Section 25.6.15, “TLS Link Encryption for NDB Cluster”
</a>
,
as well as
<a class="xref" href="mysql-cluster-programs-ndb-sign-keys.html" title="25.5.28 ndb_sign_keys — Create, Sign, and Manage TLS Keys and Certificates for NDB Cluster">
Section 25.5.28, “ndb_sign_keys — Create, Sign, and Manage TLS Keys and Certificates for NDB
Cluster”
</a>
.
</p>
</li>
<li class="listitem">
<p>
<b>
Binary log injector memory allocation.
</b>
In previous versions of NDB Cluster, when the
<code class="literal">
NDB
</code>
binary log injector was engaged in
handling schema changes and tracking the state of the binary
log, the choice of arena for allocation of memory for these
purposes was forced by changing thread local pointers, thus
attempting to try and catch all allocations performed during
epoch processing. At the end of the epoch, those pointers
were reset, arena memory was released, and the arena
structures discarded; this released the memory, but also
required setting it up again for the next epoch. The thread
local pointer changes also introduced the risk of memory
being allocated wrongly when activating functionality in
different subsystems. MySQL NDB Cluster 8.3 makes the
following improvements to this functionality:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
Changes to thread local pointers are removed, and replaced
by explicit arguments to provide the arena used for
allocation during the epoch.
</p>
</li>
<li class="listitem">
<p>
Re-use of the arena for next epoch, thus avoiding the need
to set it up repeatedly.
</p>
</li>
</ul>
</div>
<p>
These changes are internal only but should provide a
noticeable improvememnt by saving on memory release and
re-allocation over successive epochs.
</p>
</li>
<li class="listitem">
<p>
<b>
NDB API primary key updates.
</b>
Previously, when using any other mechanism than
<a class="ulink" href="/doc/ndbapi/en/ndb-ndbrecord.html" target="_top">
<code class="literal">
NdbRecord
</code>
</a>
in an attempt to
update a primary key value, the NDB API returned error 4202
<span class="errortext">
Set value on tuple key attribute is not
allowed
</span>
, even setting a value identical to the
existing one. In NDB 8.1 and later, checking when performing
updates by other means is handed off to the data nodes, as
it was already when using
<code class="literal">
NdbRecord
</code>
to
perform the update.
</p>
<p>
This means that you can now perform primary key updates using
<a class="ulink" href="/doc/ndbapi/en/ndb-ndboperation.html#ndb-ndboperation-setvalue" target="_top">
<code class="literal">
NdbOperation::setValue()
</code>
</a>
,
<a class="ulink" href="/doc/ndbapi/en/ndb-ndbinterpretedcode.html#ndb-ndbinterpretedcode-write-attr" target="_top">
<code class="literal">
NdbInterpretedCode::write_attr()
</code>
</a>
,
and other methods of
<a class="ulink" href="/doc/ndbapi/en/ndb-ndboperation.html" target="_top">
<code class="literal">
NdbOperation
</code>
</a>
and
<a class="ulink" href="/doc/ndbapi/en/ndb-ndbinterpretedcode.html" target="_top">
<code class="literal">
NdbInterpretedCode
</code>
</a>
which set
column values (including the
<code class="literal">
NdbOperation
</code>
methods
<a class="ulink" href="/doc/ndbapi/en/ndb-ndboperation.html#ndb-ndboperation-incvalue" target="_top">
<code class="literal">
incValue()
</code>
</a>
,
<a class="ulink" href="/doc/ndbapi/en/ndb-ndboperation.html#ndb-ndboperation-subvalue" target="_top">
<code class="literal">
subValue()
</code>
</a>
, the
<code class="literal">
NdbInterpretedCode
</code>
methods
<a class="ulink" href="/doc/ndbapi/en/ndb-ndbinterpretedcode.html#ndb-ndbinterpretedcode-add-val" target="_top">
<code class="literal">
add_val()
</code>
</a>
,
<a class="ulink" href="/doc/ndbapi/en/ndb-ndbinterpretedcode.html#ndb-ndbinterpretedcode-sub-val" target="_top">
<code class="literal">
sub_val()
</code>
</a>
,
and so on). This also applies to the
<a class="ulink" href="/doc/ndbapi/en/ndb-ndboperation.html" target="_top">
<code class="literal">
NdbOperation
</code>
</a>
interface's
<code class="literal">
OperationOptions::OO_SETVALUE
</code>
extension.
</p>
</li>
<li class="listitem">
<p>
<b>
Improved warnings.
</b>
Made the following improvements in warning output:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
The maximum time allowed without any progress is now also
printed in addition to local checkpoint (LCP) elapsed
time.
</p>
</li>
<li class="listitem">
<p>
When an LCP reaches
<code class="literal">
WAIT_END_LCP
</code>
state,
table IDs and fragment IDs are undefined and so no longer
relevant; for this reason, we no longer attempt to print
them at that point.
</p>
</li>
<li class="listitem">
<p>
Removed duplicated information printed when the maximum
limit was reached (the same information was shown as both
warning and crash information).
</p>
</li>
</ul>
</div>
<p>
In addition, we no longer print the message
<span class="errortext">
Validating excluded objects
</span>
to the SQL
node's error log every
<a class="link" href="mysql-cluster-options-variables.html#sysvar_ndb_metadata_check_interval">
<code class="literal">
ndb_metadata_check_interval
</code>
</a>
(default 60) seconds when
<a class="link" href="server-system-variables.html#sysvar_log_error_verbosity">
<code class="literal">
log_error_verbosity
</code>
</a>
is
greater than or equal to 3 (INFO level), due ot the fact that
such messages tended to flood the error log, making it
difficult to examine, and using excess disk space, while not
providing any additional benefit to the user.
</p>
</li>
<li class="listitem">
<p>
Pushdown joins between queries featuring very large and
possibly overlapping
<a class="link" href="comparison-operators.html#operator_in">
<code class="literal">
IN()
</code>
</a>
and
<code class="literal">
NOT IN()
</code>
lists are now handled in a correct
and safe manner.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
ndbcluster
</code>
plugin log messages now use
<code class="literal">
SYSTEM
</code>
as the log level and
<code class="literal">
NDB
</code>
as the subsystem for logging. This
means that informational messages from the
<code class="literal">
ndbcluster
</code>
plugin are always printed; their
verbosity can be controlled by using
<a class="link" href="mysql-cluster-options-variables.html#sysvar_ndb_extra_logging">
<code class="option">
--ndb_extra_logging
</code>
</a>
.
</p>
</li>
</ul>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/audit-log-installation.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="audit-log-installation">
</a>
8.4.5.2 Installing or Uninstalling MySQL Enterprise Audit
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045238596512">
</a>
<a class="indexterm" name="idm46045238595056">
</a>
<p>
This section describes how to install or uninstall MySQL Enterprise Audit,
which is implemented using the audit log plugin and related
elements described in
<a class="xref" href="audit-log-elements.html" title="8.4.5.1 Elements of MySQL Enterprise Audit">
Section 8.4.5.1, “Elements of MySQL Enterprise Audit”
</a>
. For
general information about installing plugins, see
<a class="xref" href="plugin-loading.html" title="7.6.1 Installing and Uninstalling Plugins">
Section 7.6.1, “Installing and Uninstalling Plugins”
</a>
.
</p>
<p>
Plugin upgrades are not automatic when you upgrade a MySQL
installation and some plugin loadable functions must be loaded
manually (see
<a class="xref" href="function-loading.html#loadable-function-installing" title="Installing Loadable Functions">
Installing Loadable Functions
</a>
).
Alternatively, you can reinstall the plugin after upgrading
MySQL to load new functions.
</p>
<div class="important" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Important
</div>
<p>
Read this entire section before following its instructions.
Parts of the procedure differ depending on your environment.
</p>
</div>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
If installed, the
<code class="literal">
audit_log
</code>
plugin involves
some minimal overhead even when disabled. To avoid this
overhead, do not install MySQL Enterprise Audit unless you plan to use it.
</p>
</div>
<p>
To be usable by the server, the plugin library file must be
located in the MySQL plugin directory (the directory named by
the
<a class="link" href="server-system-variables.html#sysvar_plugin_dir">
<code class="literal">
plugin_dir
</code>
</a>
system
variable). If necessary, configure the plugin directory location
by setting the value of
<a class="link" href="server-system-variables.html#sysvar_plugin_dir">
<code class="literal">
plugin_dir
</code>
</a>
at server startup.
</p>
<p>
To install MySQL Enterprise Audit, look in the
<code class="filename">
share
</code>
directory of your MySQL installation and choose the script that
is appropriate for your platform. The available scripts differ
in the file name used to refer to the script:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<code class="filename">
audit_log_filter_win_install.sql
</code>
</p>
</li>
<li class="listitem">
<p>
<code class="filename">
audit_log_filter_linux_install.sql
</code>
</p>
</li>
</ul>
</div>
<p>
Run the script as follows. The example here uses the Linux
installation script and the default
<code class="literal">
mysql
</code>
system database. Make the appropriate substitution for your
system.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-terminal"><div class="docs-select-all right" id="sa44341574"><div class="copy-help left">Press ⌘+C to 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> <span class="token property">-D</span> mysql < audit_log_filter_linux_install<span class="token punctuation">.</span>sql
Enter password<span class="token punctuation">:</span> <span class="token punctuation"></span><em class="replaceable"><span class="token punctuation">(</span>enter root password here<span class="token punctuation">)</span></em><span class="token punctuation"></span></code></pre>
</div>
<p>
It is possible to specify a custom database for storing JSON
filter tables when you run the installation script. Create the
database first; its name should not exceed 64 characters. For
example:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa13536271"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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> <span class="token keyword">IF</span> <span class="token operator">NOT</span> <span class="token keyword">EXISTS</span> <span class="token keyword"></span><em class="replaceable"><span class="token keyword">database</span><span class="token operator">-</span><span class="token keyword">name</span></em><span class="token keyword"></span><span class="token punctuation">;</span></code></pre>
</div>
<p>
Next, run the script using the alternative database name.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-terminal"><div class="docs-select-all right" id="sa20561140"><div class="copy-help left">Press ⌘+C to 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> <span class="token property">-D</span> <em class="replaceable">database-name</em> < audit_log_filter_linux_install<span class="token punctuation">.</span>sql
Enter password<span class="token punctuation">:</span> <span class="token punctuation"></span><em class="replaceable"><span class="token punctuation">(</span>enter root password here<span class="token punctuation">)</span></em><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>
Some MySQL versions have introduced changes to the structure
of the MySQL Enterprise Audit tables. To ensure that your tables are up to
date for upgrades from earlier versions of MySQL, perform the
MySQL upgrade procedure, making sure to use the option that
forces an update (see
<a class="xref" href="upgrading.html" title="Chapter 3 Upgrading MySQL">
Chapter 3,
<i>
Upgrading MySQL
</i>
</a>
). If you
prefer to run the update statements only for the MySQL Enterprise Audit
tables, see the following discussion.
</p>
<p>
For new MySQL installations, the
<code class="literal">
USER
</code>
and
<code class="literal">
HOST
</code>
columns in the
<code class="literal">
audit_log_user
</code>
table used by MySQL Enterprise Audit have
definitions that better correspond to the definitions of the
<code class="literal">
User
</code>
and
<code class="literal">
Host
</code>
columns in
the
<code class="literal">
mysql.user
</code>
system table. For upgrades
to an installation for which MySQL Enterprise Audit is already installed,
it is recommended that you alter the table definitions as
follows:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa70075997"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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> mysql<span class="token punctuation">.</span>audit_log_user
<span class="token keyword">DROP</span> <span class="token keyword">FOREIGN</span> <span class="token keyword">KEY</span> audit_log_user_ibfk_1<span class="token punctuation">;</span>
<span class="token keyword">ALTER</span> <span class="token keyword">TABLE</span> mysql<span class="token punctuation">.</span>audit_log_filter
CONVERT <span class="token keyword">TO</span> <span class="token keyword">CHARACTER</span> <span class="token keyword">SET</span> utf8mb4 <span class="token keyword">COLLATE</span> utf8mb4_0900_as_ci<span class="token punctuation">;</span>
<span class="token keyword">ALTER</span> <span class="token keyword">TABLE</span> mysql<span class="token punctuation">.</span>audit_log_user
CONVERT <span class="token keyword">TO</span> <span class="token keyword">CHARACTER</span> <span class="token keyword">SET</span> utf8mb4 <span class="token keyword">COLLATE</span> utf8mb4_0900_as_ci<span class="token punctuation">;</span>
<span class="token keyword">ALTER</span> <span class="token keyword">TABLE</span> mysql<span class="token punctuation">.</span>audit_log_user
<span class="token keyword">MODIFY</span> <span class="token keyword">COLUMN</span> <span class="token keyword">USER</span> <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>
<span class="token keyword">ALTER</span> <span class="token keyword">TABLE</span> mysql<span class="token punctuation">.</span>audit_log_user
<span class="token keyword">ADD</span> <span class="token keyword">FOREIGN</span> <span class="token keyword">KEY</span> <span class="token punctuation">(</span>FILTERNAME<span class="token punctuation">)</span> <span class="token keyword">REFERENCES</span> mysql<span class="token punctuation">.</span>audit_log_filter<span class="token punctuation">(</span><span class="token keyword">NAME</span><span class="token punctuation">)</span><span class="token punctuation">;</span></code></pre>
</div>
</div>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
To use MySQL Enterprise Audit in the context of source/replica replication,
Group Replication, or InnoDB Cluster, you must prepare the
replica nodes prior to running the installation script on the
source node. This is necessary because the
<a class="link" href="install-plugin.html" title="15.7.4.4 INSTALL PLUGIN Statement">
<code class="literal">
INSTALL PLUGIN
</code>
</a>
statement in the
script is not replicated.
</p>
<div class="orderedlist">
<ol class="orderedlist" type="1">
<li class="listitem">
<p>
On each replica node, extract the
<a class="link" href="install-plugin.html" title="15.7.4.4 INSTALL PLUGIN Statement">
<code class="literal">
INSTALL PLUGIN
</code>
</a>
statement
from the installation script and execute it manually.
</p>
</li>
<li class="listitem">
<p>
On the source node, run the installation script as
described previously.
</p>
</li>
</ol>
</div>
</div>
<p>
To verify plugin installation, examine the Information Schema
<a class="link" href="information-schema-plugins-table.html" title="28.3.22 The INFORMATION_SCHEMA PLUGINS Table">
<code class="literal">
PLUGINS
</code>
</a>
table or use the
<a class="link" href="show-plugins.html" title="15.7.7.27 SHOW PLUGINS Statement">
<code class="literal">
SHOW PLUGINS
</code>
</a>
statement (see
<a class="xref" href="obtaining-plugin-information.html" title="7.6.2 Obtaining Server Plugin Information">
Section 7.6.2, “Obtaining Server Plugin Information”
</a>
). For example:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa78236489"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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> PLUGIN_NAME<span class="token punctuation">,</span> PLUGIN_STATUS
<span class="token keyword">FROM</span> INFORMATION_SCHEMA<span class="token punctuation">.</span><span class="token keyword">PLUGINS</span>
<span class="token keyword">WHERE</span> PLUGIN_NAME <span class="token operator">LIKE</span> <span class="token string">'audit%'</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>
<span class="token output"><span class="token punctuation">|</span> PLUGIN_NAME <span class="token punctuation">|</span> PLUGIN_STATUS <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 output"><span class="token punctuation">|</span> audit_log <span class="token punctuation">|</span> ACTIVE <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></code></pre>
</div>
<p>
If the plugin fails to initialize, check the server error log
for diagnostic messages.
</p>
<p>
After MySQL Enterprise Audit is installed, you can use the
<a class="link" href="audit-log-reference.html#option_mysqld_audit-log">
<code class="option">
--audit-log
</code>
</a>
option for subsequent
server startups to control
<code class="literal">
audit_log
</code>
plugin
activation. For example, to prevent the plugin from being
removed at runtime, use this option:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-ini"><div class="docs-select-all right" id="sa93303557"><div class="copy-help left">Press ⌘+C to 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">audit-log</span><span class="token attr-value"><span class="token punctuation">=</span>FORCE_PLUS_PERMANENT</span></code></pre>
</div>
<p>
If it is desired to prevent the server from running without the
audit plugin, use
<a class="link" href="audit-log-reference.html#option_mysqld_audit-log">
<code class="option">
--audit-log
</code>
</a>
with a value of
<code class="literal">
FORCE
</code>
or
<code class="literal">
FORCE_PLUS_PERMANENT
</code>
to force server startup
to fail if the plugin does not initialize successfully.
</p>
<div class="important" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Important
</div>
<p>
By default, rule-based audit log filtering logs no auditable
events for any users. This differs from legacy audit log
behavior, which logs all auditable events for all users (see
<a class="xref" href="audit-log-legacy-filtering.html" title="8.4.5.10 Legacy Mode Audit Log Filtering">
Section 8.4.5.10, “Legacy Mode Audit Log Filtering”
</a>
). Should you wish
to produce log-everything behavior with rule-based filtering,
create a simple filter to enable logging and assign it to the
default account:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa99525951"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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> audit_log_filter_set_filter<span class="token punctuation">(</span><span class="token string">'log_all'</span><span class="token punctuation">,</span> <span class="token string">'{ "filter": { "log": true } }'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token keyword">SELECT</span> audit_log_filter_set_user<span class="token punctuation">(</span><span class="token string">'%'</span><span class="token punctuation">,</span> <span class="token string">'log_all'</span><span class="token punctuation">)</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
The filter assigned to
<code class="literal">
%
</code>
is used for
connections from any account that has no explicitly assigned
filter (which initially is true for all accounts).
</p>
</div>
<p>
When installed as just described, MySQL Enterprise Audit remains installed
until uninstalled. To remove it, run the uninstall script
located in the
<code class="literal">
share
</code>
directory of your MySQL
installation. The example here specifies the default system
database,
<code class="literal">
mysql
</code>
. Make the appropriate
substitution for your system.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-terminal"><div class="docs-select-all right" id="sa83508001"><div class="copy-help left">Press ⌘+C to 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> <span class="token property">-D</span> mysql < audit_log_filter_uninstall<span class="token punctuation">.</span>sql
Enter password<span class="token punctuation">:</span> <span class="token punctuation"></span><em class="replaceable"><span class="token punctuation">(</span>enter root password here<span class="token punctuation">)</span></em><span class="token punctuation"></span></code></pre>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/keyring-metadata.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="keyring-metadata">
</a>
8.4.4.14 Keyring Metadata
</h4>
</div>
</div>
</div>
<p>
This section describes sources of information about keyring use.
</p>
<p>
To see whether a keyring plugin is loaded, check the Information
Schema
<a class="link" href="information-schema-plugins-table.html" title="28.3.22 The INFORMATION_SCHEMA PLUGINS Table">
<code class="literal">
PLUGINS
</code>
</a>
table or use the
<a class="link" href="show-plugins.html" title="15.7.7.27 SHOW PLUGINS Statement">
<code class="literal">
SHOW PLUGINS
</code>
</a>
statement (see
<a class="xref" href="obtaining-plugin-information.html" title="7.6.2 Obtaining Server Plugin Information">
Section 7.6.2, “Obtaining Server Plugin Information”
</a>
). For example:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa40236693"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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> PLUGIN_NAME<span class="token punctuation">,</span> PLUGIN_STATUS
<span class="token keyword">FROM</span> INFORMATION_SCHEMA<span class="token punctuation">.</span><span class="token keyword">PLUGINS</span>
<span class="token keyword">WHERE</span> PLUGIN_NAME <span class="token operator">LIKE</span> <span class="token string">'keyring%'</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>
<span class="token output"><span class="token punctuation">|</span> PLUGIN_NAME <span class="token punctuation">|</span> PLUGIN_STATUS <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 output"><span class="token punctuation">|</span> keyring_okv <span class="token punctuation">|</span> ACTIVE <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></code></pre>
</div>
<p>
To see which keys exist, check 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:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa79783206"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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>keyring_keys<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>
<span class="token output"><span class="token punctuation">|</span> KEY_ID <span class="token punctuation">|</span> KEY_OWNER <span class="token punctuation">|</span> BACKEND_KEY_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 class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><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<span class="token punctuation">-</span>20210322T130749<span class="token punctuation">-</span>1 <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> MyKey <span class="token punctuation">|</span> me@localhost <span class="token punctuation">|</span> <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> YourKey <span class="token punctuation">|</span> me@localhost <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 class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="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 see whether a keyring component is loaded, check 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. For
example:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa18862315"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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>keyring_component_status<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> STATUS_KEY <span class="token punctuation">|</span> STATUS_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 class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><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> Component_name <span class="token punctuation">|</span> component_keyring_file <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> Author <span class="token punctuation">|</span> Oracle Corporation <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> License <span class="token punctuation">|</span> GPL <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> Implementation_name <span class="token punctuation">|</span> component_keyring_file <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> Version <span class="token punctuation">|</span> 1.0 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> Component_status <span class="token punctuation">|</span> Active <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> Data_file <span class="token punctuation">|</span> /usr/local/mysql/keyring/component_keyring_file <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> Read_only <span class="token punctuation">|</span> No <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></code></pre>
</div>
<p>
A
<code class="literal">
Component_status
</code>
value of
<code class="literal">
Active
</code>
indicates that the component
initialized successfully. If the component loaded but failed to
initialize, the value is
<code class="literal">
Disabled
</code>
.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/mysql-cluster-management.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h2 class="title">
<a name="mysql-cluster-management">
</a>
25.6 Management of NDB Cluster
</h2>
</div>
</div>
</div>
<div class="toc">
<dl class="toc">
<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>
</div>
<a class="indexterm" name="idm46045094663792">
</a>
<a class="indexterm" name="idm46045094662304">
</a>
<p>
Managing an NDB Cluster involves a number of tasks, the first of
which is to configure and start NDB Cluster. This is covered in
<a class="xref" href="mysql-cluster-configuration.html" title="25.4 Configuration of NDB Cluster">
Section 25.4, “Configuration of NDB Cluster”
</a>
, and
<a class="xref" href="mysql-cluster-programs.html" title="25.5 NDB Cluster Programs">
Section 25.5, “NDB Cluster Programs”
</a>
.
</p>
<p>
The next few sections cover the management of a running NDB Cluster.
</p>
<p>
For information about security issues relating to management and
deployment of an NDB Cluster, see
<a class="xref" href="mysql-cluster-security.html" title="25.6.21 NDB Cluster Security Issues">
Section 25.6.21, “NDB Cluster Security Issues”
</a>
.
</p>
<p>
There are essentially two methods of actively managing a running NDB
Cluster. The first of these is through the use of commands entered
into the management client whereby cluster status can be checked,
log levels changed, backups started and stopped, and nodes stopped
and started. The second method involves studying the contents of the
cluster log
<code class="filename">
ndb_
<em class="replaceable">
<code>
node_id
</code>
</em>
_cluster.log
</code>
;
this is usually found in the management server's
<a class="link" href="mysql-cluster-mgm-definition.html#ndbparam-mgmd-datadir">
<code class="literal">
DataDir
</code>
</a>
directory, but this
location can be overridden using the
<a class="link" href="mysql-cluster-mgm-definition.html#ndbparam-mgmd-logdestination">
<code class="literal">
LogDestination
</code>
</a>
option.
(Recall that
<em class="replaceable">
<code>
node_id
</code>
</em>
represents the
unique identifier of the node whose activity is being logged.) The
cluster log contains event reports generated by
<a class="link" href="mysql-cluster-programs-ndbd.html" title="25.5.1 ndbd — The NDB Cluster Data Node Daemon">
<span class="command">
<strong>
ndbd
</strong>
</span>
</a>
. It is also possible to send cluster log
entries to a Unix system log.
</p>
<p>
Some aspects of the cluster's operation can be also be
monitored from an SQL node using the
<a class="link" href="show-engine.html" title="15.7.7.16 SHOW ENGINE Statement">
<code class="literal">
SHOW ENGINE NDB
STATUS
</code>
</a>
statement.
</p>
<p>
More detailed information about NDB Cluster operations is available
in real time through an SQL interface using the
<a class="link" href="mysql-cluster-ndbinfo.html" title="25.6.17 ndbinfo: The NDB Cluster Information Database">
<code class="literal">
ndbinfo
</code>
</a>
database. For more
information, see
<a class="xref" href="mysql-cluster-ndbinfo.html" title="25.6.17 ndbinfo: The NDB Cluster Information Database">
Section 25.6.17, “ndbinfo: The NDB Cluster Information Database”
</a>
.
</p>
<p>
NDB statistics counters provide improved monitoring 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. These counters, implemented in the
NDB kernel, relate to operations performed by or affecting
<a class="ulink" href="/doc/ndbapi/en/ndb-ndb.html" target="_top">
<code class="literal">
Ndb
</code>
</a>
objects, such as starting,
closing, and aborting transactions; primary key and unique key
operations; table, range, and pruned scans; blocked threads waiting
for various operations to complete; and data and events sent and
received by NDB Cluster. The counters are incremented by the NDB
kernel whenever NDB API calls are made or data is sent to or
received by the data nodes.
</p>
<p>
<a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
<span class="command">
<strong>
mysqld
</strong>
</span>
</a>
exposes the NDB API statistics counters as
system status variables, which can be identified from the prefix
common to all of their names (
<code class="literal">
Ndb_api_
</code>
). The
values of these variables can be read 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 from the output of a
<a class="link" href="show-status.html" title="15.7.7.37 SHOW STATUS Statement">
<code class="literal">
SHOW STATUS
</code>
</a>
statement, or by querying
either the Performance Schema
<a class="link" href="performance-schema-status-variable-tables.html" title="29.12.15 Performance Schema Status Variable Tables">
<code class="literal">
session_status
</code>
</a>
or
<a class="link" href="performance-schema-status-variable-tables.html" title="29.12.15 Performance Schema Status Variable Tables">
<code class="literal">
global_status
</code>
</a>
table. By comparing the
values of the status variables before and after the execution of an
SQL statement that acts on
<a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4">
<code class="literal">
NDB
</code>
</a>
tables,
you can observe the actions taken on the NDB API level that
correspond to this statement, which can be beneficial for monitoring
and performance tuning of NDB Cluster.
</p>
<p>
MySQL Cluster Manager provides an advanced command-line interface that simplifies
many otherwise complex NDB Cluster management tasks, such as
starting, stopping, or restarting an NDB Cluster with a large number
of nodes. The MySQL Cluster Manager client also supports commands for getting and
setting the values of most node configuration parameters as well as
<a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
<span class="command">
<strong>
mysqld
</strong>
</span>
</a>
server options and variables relating to
NDB Cluster. See
<a class="ulink" href="/doc/mysql-cluster-manager/8.4/en/" target="_top">
MySQL Cluster Manager 8.4.3 User Manual
</a>
, for more information.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/validate-password.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="validate-password">
</a>
8.4.3 The Password Validation Component
</h3>
</div>
</div>
</div>
<div class="toc">
<dl class="toc">
<dt>
<span class="section">
<a href="validate-password-installation.html">
8.4.3.1 Password Validation Component Installation and Uninstallation
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="validate-password-options-variables.html">
8.4.3.2 Password Validation Options and Variables
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="validate-password-transitioning.html">
8.4.3.3 Transitioning to the Password Validation Component
</a>
</span>
</dt>
</dl>
</div>
<a class="indexterm" name="idm46045241832688">
</a>
<a class="indexterm" name="idm46045241831632">
</a>
<a class="indexterm" name="idm46045241830544">
</a>
<a class="indexterm" name="idm46045241829472">
</a>
<p>
The
<code class="literal">
validate_password
</code>
component serves to
improve security by requiring account passwords and enabling
strength testing of potential passwords. This component exposes
system variables that enable you to configure password policy, and
status variables for component monitoring.
</p>
<p>
The
<code class="literal">
validate_password
</code>
component implements
these capabilities:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
For SQL statements that assign a password supplied as a
cleartext value,
<code class="literal">
validate_password
</code>
checks
the password against the current password policy and rejects
the password if it is weak (the statement returns an
<a class="ulink" href="/doc/mysql-errors/8.4/en/server-error-reference.html#error_er_not_valid_password" target="_top">
<code class="literal">
ER_NOT_VALID_PASSWORD
</code>
</a>
error).
This applies to the
<a class="link" href="alter-user.html" title="15.7.1.1 ALTER USER Statement">
<code class="literal">
ALTER USER
</code>
</a>
,
<a class="link" href="create-user.html" title="15.7.1.3 CREATE USER Statement">
<code class="literal">
CREATE 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>
statements.
</p>
</li>
<li class="listitem">
<p>
For
<a class="link" href="create-user.html" title="15.7.1.3 CREATE USER Statement">
<code class="literal">
CREATE USER
</code>
</a>
statements,
<code class="literal">
validate_password
</code>
requires that a password
be given, and that it satisfies the password policy. This is
true even if an account is locked initially because otherwise
unlocking the account later would cause it to become
accessible without a password that satisfies the policy.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
validate_password
</code>
implements a
<a class="link" href="encryption-functions.html#function_validate-password-strength">
<code class="literal">
VALIDATE_PASSWORD_STRENGTH()
</code>
</a>
SQL function that assesses the strength of potential
passwords. This function takes a password argument and returns
an integer from 0 (weak) to 100 (strong).
</p>
</li>
</ul>
</div>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
For statements that assign or modify account passwords
(
<a class="link" href="alter-user.html" title="15.7.1.1 ALTER USER Statement">
<code class="literal">
ALTER USER
</code>
</a>
,
<a class="link" href="create-user.html" title="15.7.1.3 CREATE USER Statement">
<code class="literal">
CREATE 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>
), the
<code class="literal">
validate_password
</code>
capabilities described here
apply only to accounts that use an authentication plugin that
stores credentials internally to MySQL. For accounts that use
plugins that perform authentication against a credentials system
external to MySQL, password management must be handled
externally against that system as well. For more information
about internal credentials storage, see
<a class="xref" href="password-management.html" title="8.2.15 Password Management">
Section 8.2.15, “Password Management”
</a>
.
</p>
<p>
The preceding restriction does not apply to use of the
<a class="link" href="encryption-functions.html#function_validate-password-strength">
<code class="literal">
VALIDATE_PASSWORD_STRENGTH()
</code>
</a>
function because it does not affect accounts directly.
</p>
</div>
<p>
Examples:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<code class="literal">
validate_password
</code>
checks the cleartext
password in the following statement. Under the default
password policy, which requires passwords to be at least 8
characters long, the password is weak and the statement
produces an error:
</p>
<a class="indexterm" name="idm46045241802240">
</a>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa99236394"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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">'abc'</span><span class="token punctuation">;</span>
<span class="token output">ERROR 1819 (HY000)<span class="token punctuation">:</span> Your password does not satisfy the current
policy requirements</span></code></pre>
</div>
</li>
<li class="listitem">
<p>
Passwords specified as hashed values are not checked because
the original password value is not available for checking:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa68291346"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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">'jeffrey'</span>@<span class="token string">'localhost'</span>
<span class="token keyword">IDENTIFIED</span> <span class="token keyword">WITH</span> mysql_native_password
<span class="token keyword">AS</span> <span class="token string">'*0D3CED9BEC10A777AEC23CCC353A8C08A633045E'</span><span class="token punctuation">;</span>
<span class="token output">Query OK, 0 rows affected (0.01 sec)</span></code></pre>
</div>
</li>
<li class="listitem">
<p>
This account-creation statement fails, even though the account
is locked initially, because it does not include a password
that satisfies the current password policy:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa56583164"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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">USER</span> <span class="token string">'juanita'</span>@<span class="token string">'localhost'</span> <span class="token keyword">ACCOUNT</span> <span class="token keyword">LOCK</span><span class="token punctuation">;</span>
<span class="token output">ERROR 1819 (HY000)<span class="token punctuation">:</span> Your password does not satisfy the current
policy requirements</span></code></pre>
</div>
</li>
<li class="listitem">
<p>
To check a password, use the
<a class="link" href="encryption-functions.html#function_validate-password-strength">
<code class="literal">
VALIDATE_PASSWORD_STRENGTH()
</code>
</a>
function:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa94743178"><div class="copy-help left">Press ⌘+C to copy</div> <div class="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">VALIDATE_PASSWORD_STRENGTH</span><span class="token punctuation">(</span><span class="token string">'weak'</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> VALIDATE_PASSWORD_STRENGTH('weak') <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> 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>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">VALIDATE_PASSWORD_STRENGTH</span><span class="token punctuation">(</span><span class="token string">'lessweak$_@123'</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>
<span class="token output"><span class="token punctuation">|</span> VALIDATE_PASSWORD_STRENGTH('lessweak$_@123') <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>
<span class="token output"><span class="token punctuation">|</span> 50 <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>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">VALIDATE_PASSWORD_STRENGTH</span><span class="token punctuation">(</span><span class="token string">'N0Tweak$_@123!'</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>
<span class="token output"><span class="token punctuation">|</span> VALIDATE_PASSWORD_STRENGTH('N0Tweak$_@123!') <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>
<span class="token output"><span class="token punctuation">|</span> 100 <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></code></pre>
</div>
</li>
</ul>
</div>
<p>
To configure password checking, modify the system variables having
names of the form
<code class="literal">
validate_password.
<em class="replaceable">
<code>
xxx
</code>
</em>
</code>
;
these are the parameters that control password policy. See
<a class="xref" href="validate-password-options-variables.html" title="8.4.3.2 Password Validation Options and Variables">
Section 8.4.3.2, “Password Validation Options and Variables”
</a>
.
</p>
<p>
If
<code class="literal">
validate_password
</code>
is not installed, the
<code class="literal">
validate_password.
<em class="replaceable">
<code>
xxx
</code>
</em>
</code>
system variables are not available, passwords in statements are
not checked, and the
<a class="link" href="encryption-functions.html#function_validate-password-strength">
<code class="literal">
VALIDATE_PASSWORD_STRENGTH()
</code>
</a>
function always returns 0. For example, without the plugin
installed, accounts can be assigned passwords shorter than 8
characters, or no password at all.
</p>
<p>
Assuming that
<code class="literal">
validate_password
</code>
is installed,
it implements three levels of password checking:
<code class="literal">
LOW
</code>
,
<code class="literal">
MEDIUM
</code>
, and
<code class="literal">
STRONG
</code>
. The default is
<code class="literal">
MEDIUM
</code>
; to change this, modify the value of
<a class="link" href="validate-password-options-variables.html#sysvar_validate_password.policy">
<code class="literal">
validate_password.policy
</code>
</a>
. The
policies implement increasingly strict password tests. The
following descriptions refer to default parameter values, which
can be modified by changing the appropriate system variables.
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<code class="literal">
LOW
</code>
policy tests password length only.
Passwords must be at least 8 characters long. To change this
length, modify
<a class="link" href="validate-password-options-variables.html#sysvar_validate_password.length">
<code class="literal">
validate_password.length
</code>
</a>
.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
MEDIUM
</code>
policy adds the conditions that
passwords must contain at least 1 numeric character, 1
lowercase character, 1 uppercase character, and 1 special
(nonalphanumeric) character. To change these values, modify
<a class="link" href="validate-password-options-variables.html#sysvar_validate_password.number_count">
<code class="literal">
validate_password.number_count
</code>
</a>
,
<a class="link" href="validate-password-options-variables.html#sysvar_validate_password.mixed_case_count">
<code class="literal">
validate_password.mixed_case_count
</code>
</a>
,
and
<a class="link" href="validate-password-options-variables.html#sysvar_validate_password.special_char_count">
<code class="literal">
validate_password.special_char_count
</code>
</a>
.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
STRONG
</code>
policy adds the condition that
password substrings of length 4 or longer must not match words
in the dictionary file, if one has been specified. To specify
the dictionary file, modify
<a class="link" href="validate-password-options-variables.html#sysvar_validate_password.dictionary_file">
<code class="literal">
validate_password.dictionary_file
</code>
</a>
.
</p>
</li>
</ul>
</div>
<p>
In addition,
<code class="literal">
validate_password
</code>
supports the
capability of rejecting passwords that match the user name part of
the effective user account for the current session, either forward
or in reverse. To provide control over this capability,
<code class="literal">
validate_password
</code>
exposes a
<a class="link" href="validate-password-options-variables.html#sysvar_validate_password.check_user_name">
<code class="literal">
validate_password.check_user_name
</code>
</a>
system variable, which is enabled by default.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/two-digit-years.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="two-digit-years">
</a>
13.2.9 2-Digit Years in Dates
</h3>
</div>
</div>
</div>
<p>
Date values with 2-digit years are ambiguous because the century
is unknown. Such values must be interpreted into 4-digit form
because MySQL stores years internally using 4 digits.
</p>
<p>
For
<a class="link" href="datetime.html" title="13.2.2 The DATE, DATETIME, and TIMESTAMP Types">
<code class="literal">
DATETIME
</code>
</a>
,
<a class="link" href="datetime.html" title="13.2.2 The DATE, DATETIME, and TIMESTAMP Types">
<code class="literal">
DATE
</code>
</a>
, and
<a class="link" href="datetime.html" title="13.2.2 The DATE, DATETIME, and TIMESTAMP Types">
<code class="literal">
TIMESTAMP
</code>
</a>
types, MySQL interprets
dates specified with ambiguous year values using these rules:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
Year values in the range
<code class="literal">
00-69
</code>
become
<code class="literal">
2000-2069
</code>
.
</p>
</li>
<li class="listitem">
<p>
Year values in the range
<code class="literal">
70-99
</code>
become
<code class="literal">
1970-1999
</code>
.
</p>
</li>
</ul>
</div>
<p>
For
<code class="literal">
YEAR
</code>
, the rules are the same, with this
exception: A numeric
<code class="literal">
00
</code>
inserted into
<code class="literal">
YEAR
</code>
results in
<code class="literal">
0000
</code>
rather than
<code class="literal">
2000
</code>
. To specify zero for
<code class="literal">
YEAR
</code>
and have it be interpreted as
<code class="literal">
2000
</code>
, specify it as a string
<code class="literal">
'0'
</code>
or
<code class="literal">
'00'
</code>
.
</p>
<p>
Remember that these rules are only heuristics that provide
reasonable guesses as to what your data values mean. If the
rules used by MySQL do not produce the values you require, you
must provide unambiguous input containing 4-digit year values.
</p>
<p>
<code class="literal">
ORDER BY
</code>
properly sorts
<a class="link" href="year.html" title="13.2.4 The YEAR Type">
<code class="literal">
YEAR
</code>
</a>
values that have 2-digit
years.
</p>
<p>
Some functions like
<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>
convert a
<a class="link" href="year.html" title="13.2.4 The YEAR Type">
<code class="literal">
YEAR
</code>
</a>
to a number. This means that
a value with a 2-digit year does not work properly with these
functions. The fix in this case is to convert the
<a class="link" href="year.html" title="13.2.4 The YEAR Type">
<code class="literal">
YEAR
</code>
</a>
to 4-digit year format.
</p>
</div>
<br/>
</div>
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