text: # mssql/base.py
  # Copyright (C) 2005-2019 the SQLAlchemy authors and contributors
  # <see AUTHORS file>
  #
  # This module is part of SQLAlchemy and is released under
  # the MIT License: http://www.opensource.org/licenses/mit-license.php
  """
  .. dialect:: mssql
      :name: Microsoft SQL Server
  
  
  .. _mssql_identity:
  
  Auto Increment Behavior / IDENTITY Columns
  ------------------------------------------
  
  SQL Server provides so-called "auto incrementing" behavior using the
  ``IDENTITY`` construct, which can be placed on any single integer column in a
  table. SQLAlchemy considers ``IDENTITY`` within its default "autoincrement"
  behavior for an integer primary key column, described at
  :paramref:`.Column.autoincrement`.  This means that by default, the first
  integer primary key column in a :class:`.Table` will be considered to be the
  identity column and will generate DDL as such::
  
      from sqlalchemy import Table, MetaData, Column, Integer
  
      m = MetaData()
      t = Table('t', m,
              Column('id', Integer, primary_key=True),
              Column('x', Integer))
      m.create_all(engine)
  
  The above example will generate DDL as:
  
  .. sourcecode:: sql
  
      CREATE TABLE t (
          id INTEGER NOT NULL IDENTITY(1,1),
          x INTEGER NULL,
          PRIMARY KEY (id)
      )
  
  For the case where this default generation of ``IDENTITY`` is not desired,
  specify ``False`` for the :paramref:`.Column.autoincrement` flag,
  on the first integer primary key column::
  
      m = MetaData()
      t = Table('t', m,
              Column('id', Integer, primary_key=True, autoincrement=False),
              Column('x', Integer))
      m.create_all(engine)
  
  To add the ``IDENTITY`` keyword to a non-primary key column, specify
  ``True`` for the :paramref:`.Column.autoincrement` flag on the desired
  :class:`.Column` object, and ensure that :paramref:`.Column.autoincrement`
  is set to ``False`` on any integer primary key column::
  
      m = MetaData()
      t = Table('t', m,
              Column('id', Integer, primary_key=True, autoincrement=False),
              Column('x', Integer, autoincrement=True))
      m.create_all(engine)
  
  .. versionchanged::  1.3   Added ``mssql_identity_start`` and
     ``mssql_identity_increment`` parameters to :class:`.Column`.  These replace
     the use of the :class:`.Sequence` object in order to specify these values.
  
  .. deprecated:: 1.3
  
     The use of :class:`.Sequence` to specify IDENTITY characteristics is
     deprecated and will be removed in a future release.   Please use
     the ``mssql_identity_start`` and ``mssql_identity_increment`` parameters
     documented at :ref:`mssql_identity`.
  
  .. note::
  
      There can only be one IDENTITY column on the table.  When using
      ``autoincrement=True`` to enable the IDENTITY keyword, SQLAlchemy does not
      guard against multiple columns specifying the option simultaneously.  The
      SQL Server database will instead reject the ``CREATE TABLE`` statement.
  
  .. note::
  
      An INSERT statement which attempts to provide a value for a column that is
      marked with IDENTITY will be rejected by SQL Server.   In order for the
      value to be accepted, a session-level option "SET IDENTITY_INSERT" must be
      enabled.   The SQLAlchemy SQL Server dialect will perform this operation
      automatically when using a core :class:`.Insert` construct; if the
      execution specifies a value for the IDENTITY column, the "IDENTITY_INSERT"
      option will be enabled for the span of that statement's invocation.However,
      this scenario is not high performing and should not be relied upon for
      normal use.   If a table doesn't actually require IDENTITY behavior in its
      integer primary key column, the keyword should be disabled when creating
      the table by ensuring that ``autoincrement=False`` is set.
  
  Controlling "Start" and "Increment"
  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  
  Specific control over the "start" and "increment" values for
  the ``IDENTITY`` generator are provided using the
  ``mssql_identity_start`` and ``mssql_identity_increment`` parameters
  passed to the :class:`.Column` object::
  
      from sqlalchemy import Table, Integer, Column
  
      test = Table(
          'test', metadata,
          Column(
              'id', Integer, primary_key=True, mssql_identity_start=100,
               mssql_identity_increment=10
          ),
          Column('name', String(20))
      )
  
  The CREATE TABLE for the above :class:`.Table` object would be:
  
  .. sourcecode:: sql
  
     CREATE TABLE test (
       id INTEGER NOT NULL IDENTITY(100,10) PRIMARY KEY,
       name VARCHAR(20) NULL,
       )
  
  .. versionchanged:: 1.3  The ``mssql_identity_start`` and
     ``mssql_identity_increment`` parameters are now used to affect the
     ``IDENTITY`` generator for a :class:`.Column` under  SQL Server.
     Previously, the :class:`.Sequence` object was used.  As SQL Server now
     supports real sequences as a separate construct, :class:`.Sequence` will be
     functional in the normal way in a future SQLAlchemy version.
  
  INSERT behavior
  ^^^^^^^^^^^^^^^^
  
  Handling of the ``IDENTITY`` column at INSERT time involves two key
  techniques. The most common is being able to fetch the "last inserted value"
  for a given ``IDENTITY`` column, a process which SQLAlchemy performs
  implicitly in many cases, most importantly within the ORM.
  
  The process for fetching this value has several variants:
  
  * In the vast majority of cases, RETURNING is used in conjunction with INSERT
    statements on SQL Server in order to get newly generated primary key values:
  
    .. sourcecode:: sql
  
      INSERT INTO t (x) OUTPUT inserted.id VALUES (?)
  
  * When RETURNING is not available or has been disabled via
    ``implicit_returning=False``, either the ``scope_identity()`` function or
    the ``@@identity`` variable is used; behavior varies by backend:
  
    * when using PyODBC, the phrase ``; select scope_identity()`` will be
      appended to the end of the INSERT statement; a second result set will be
      fetched in order to receive the value.  Given a table as::
  
          t = Table('t', m, Column('id', Integer, primary_key=True),
                  Column('x', Integer),
                  implicit_returning=False)
  
      an INSERT will look like:
  
      .. sourcecode:: sql
  
          INSERT INTO t (x) VALUES (?); select scope_identity()
  
    * Other dialects such as pymssql will call upon
      ``SELECT scope_identity() AS lastrowid`` subsequent to an INSERT
      statement. If the flag ``use_scope_identity=False`` is passed to
      :func:`.create_engine`, the statement ``SELECT @@identity AS lastrowid``
      is used instead.
  
  A table that contains an ``IDENTITY`` column will prohibit an INSERT statement
  that refers to the identity column explicitly.  The SQLAlchemy dialect will
  detect when an INSERT construct, created using a core :func:`.insert`
  construct (not a plain string SQL), refers to the identity column, and
  in this case will emit ``SET IDENTITY_INSERT ON`` prior to the insert
  statement proceeding, and ``SET IDENTITY_INSERT OFF`` subsequent to the
  execution.  Given this example::
  
      m = MetaData()
      t = Table('t', m, Column('id', Integer, primary_key=True),
                      Column('x', Integer))
      m.create_all(engine)
  
      engine.execute(t.insert(), {'id': 1, 'x':1}, {'id':2, 'x':2})
  
  The above column will be created with IDENTITY, however the INSERT statement
  we emit is specifying explicit values.  In the echo output we can see
  how SQLAlchemy handles this:
  
  .. sourcecode:: sql
  
      CREATE TABLE t (
          id INTEGER NOT NULL IDENTITY(1,1),
          x INTEGER NULL,
          PRIMARY KEY (id)
      )
  
      COMMIT
      SET IDENTITY_INSERT t ON
      INSERT INTO t (id, x) VALUES (?, ?)
      ((1, 1), (2, 2))
      SET IDENTITY_INSERT t OFF
      COMMIT
  
  
  
  This
  is an auxiliary use case suitable for testing and bulk insert scenarios.
  
  MAX on VARCHAR / NVARCHAR
  -------------------------
  
  SQL Server supports the special string "MAX" within the
  :class:`.sqltypes.VARCHAR` and :class:`.sqltypes.NVARCHAR` datatypes,
  to indicate "maximum length possible".   The dialect currently handles this as
  a length of "None" in the base type, rather than supplying a
  dialect-specific version of these types, so that a base type
  specified such as ``VARCHAR(None)`` can assume "unlengthed" behavior on
  more than one backend without using dialect-specific types.
  
  To build a SQL Server VARCHAR or NVARCHAR with MAX length, use None::
  
      my_table = Table(
          'my_table', metadata,
          Column('my_data', VARCHAR(None)),
          Column('my_n_data', NVARCHAR(None))
      )
  
  
  Collation Support
  -----------------
  
  Character collations are supported by the base string types,
  specified by the string argument "collation"::
  
      from sqlalchemy import VARCHAR
      Column('login', VARCHAR(32, collation='Latin1_General_CI_AS'))
  
  When such a column is associated with a :class:`.Table`, the
  CREATE TABLE statement for this column will yield::
  
      login VARCHAR(32) COLLATE Latin1_General_CI_AS NULL
  
  LIMIT/OFFSET Support
  --------------------
  
  MSSQL has no support for the LIMIT or OFFSET keywords. LIMIT is
  supported directly through the ``TOP`` Transact SQL keyword::
  
      select.limit
  
  will yield::
  
      SELECT TOP n
  
  If using SQL Server 2005 or above, LIMIT with OFFSET
  support is available through the ``ROW_NUMBER OVER`` construct.
  For versions below 2005, LIMIT with OFFSET usage will fail.
  
  .. _mssql_isolation_level:
  
  Transaction Isolation Level
  ---------------------------
  
  All SQL Server dialects support setting of transaction isolation level
  both via a dialect-specific parameter
  :paramref:`.create_engine.isolation_level`
  accepted by :func:`.create_engine`,
  as well as the :paramref:`.Connection.execution_options.isolation_level`
  argument as passed to
  :meth:`.Connection.execution_options`.  This feature works by issuing the
  command ``SET TRANSACTION ISOLATION LEVEL <level>`` for
  each new connection.
  
  To set isolation level using :func:`.create_engine`::
  
      engine = create_engine(
          "mssql+pyodbc://scott:tiger@ms_2008",
          isolation_level="REPEATABLE READ"
      )
  
  To set using per-connection execution options::
  
      connection = engine.connect()
      connection = connection.execution_options(
          isolation_level="READ COMMITTED"
      )
  
  Valid values for ``isolation_level`` include:
  
  * ``AUTOCOMMIT`` - pyodbc / pymssql-specific
  * ``READ COMMITTED``
  * ``READ UNCOMMITTED``
  * ``REPEATABLE READ``
  * ``SERIALIZABLE``
  * ``SNAPSHOT`` - specific to SQL Server
  
  .. versionadded:: 1.1 support for isolation level setting on Microsoft
     SQL Server.
  
  .. versionadded:: 1.2 added AUTOCOMMIT isolation level setting
  
  Nullability
  -----------
  MSSQL has support for three levels of column nullability. The default
  nullability allows nulls and is explicit in the CREATE TABLE
  construct::
  
      name VARCHAR(20) NULL
  
  If ``nullable=None`` is specified then no specification is made. In
  other words the database's configured default is used. This will
  render::
  
      name VARCHAR(20)
  
  If ``nullable`` is ``True`` or ``False`` then the column will be
  ``NULL`` or ``NOT NULL`` respectively.
  
  Date / Time Handling
  --------------------
  DATE and TIME are supported.   Bind parameters are converted
  to datetime.datetime() objects as required by most MSSQL drivers,
  and results are processed from strings if needed.
  The DATE and TIME types are not available for MSSQL 2005 and
  previous - if a server version below 2008 is detected, DDL
  for these types will be issued as DATETIME.
  
  .. _mssql_large_type_deprecation:
  
  Large Text/Binary Type Deprecation
  ----------------------------------
  
  Per
  `SQL Server 2012/2014 Documentation <http://technet.microsoft.com/en-us/library/ms187993.aspx>`_,
  the ``NTEXT``, ``TEXT`` and ``IMAGE`` datatypes are to be removed from SQL
  Server in a future release.   SQLAlchemy normally relates these types to the
  :class:`.UnicodeText`, :class:`.Text` and :class:`.LargeBinary` datatypes.
  
  In order to accommodate this change, a new flag ``deprecate_large_types``
  is added to the dialect, which will be automatically set based on detection
  of the server version in use, if not otherwise set by the user.  The
  behavior of this flag is as follows:
  
  * When this flag is ``True``, the :class:`.UnicodeText`, :class:`.Text` and
    :class:`.LargeBinary` datatypes, when used to render DDL, will render the
    types ``NVARCHAR(max)``, ``VARCHAR(max)``, and ``VARBINARY(max)``,
    respectively.  This is a new behavior as of the addition of this flag.
  
  * When this flag is ``False``, the :class:`.UnicodeText`, :class:`.Text` and
    :class:`.LargeBinary` datatypes, when used to render DDL, will render the
    types ``NTEXT``, ``TEXT``, and ``IMAGE``,
    respectively.  This is the long-standing behavior of these types.
  
  * The flag begins with the value ``None``, before a database connection is
    established.   If the dialect is used to render DDL without the flag being
    set, it is interpreted the same as ``False``.
  
  * On first connection, the dialect detects if SQL Server version 2012 or
    greater is in use; if the flag is still at ``None``, it sets it to ``True``
    or ``False`` based on whether 2012 or greater is detected.
  
  * The flag can be set to either ``True`` or ``False`` when the dialect
    is created, typically via :func:`.create_engine`::
  
          eng = create_engine("mssql+pymssql://user:pass@host/db",
                          deprecate_large_types=True)
  
  * Complete control over whether the "old" or "new" types are rendered is
    available in all SQLAlchemy versions by using the UPPERCASE type objects
    instead: :class:`.NVARCHAR`, :class:`.VARCHAR`, :class:`.types.VARBINARY`,
    :class:`.TEXT`, :class:`.mssql.NTEXT`, :class:`.mssql.IMAGE` will always
    remain fixed and always output exactly that type.
  
  .. versionadded:: 1.0.0
  
  .. _multipart_schema_names:
  
  Multipart Schema Names
  ----------------------
  
  SQL Server schemas sometimes require multiple parts to their "schema"
  qualifier, that is, including the database name and owner name as separate
  tokens, such as ``mydatabase.dbo.some_table``. These multipart names can be set
  at once using the :paramref:`.Table.schema` argument of :class:`.Table`::
  
      Table(
          "some_table", metadata,
          Column("q", String(50)),
          schema="mydatabase.dbo"
      )
  
  When performing operations such as table or component reflection, a schema
  argument that contains a dot will be split into separate
  "database" and "owner"  components in order to correctly query the SQL
  Server information schema tables, as these two values are stored separately.
  Additionally, when rendering the schema name for DDL or SQL, the two
  components will be quoted separately for case sensitive names and other
  special characters.   Given an argument as below::
  
      Table(
          "some_table", metadata,
          Column("q", String(50)),
          schema="MyDataBase.dbo"
      )
  
  The above schema would be rendered as ``[MyDataBase].dbo``, and also in
  reflection, would be reflected using "dbo" as the owner and "MyDataBase"
  as the database name.
  
  To control how the schema name is broken into database / owner,
  specify brackets (which in SQL Server are quoting characters) in the name.
  Below, the "owner" will be considered as ``MyDataBase.dbo`` and the
  "database" will be None::
  
      Table(
          "some_table", metadata,
          Column("q", String(50)),
          schema="[MyDataBase.dbo]"
      )
  
  To individually specify both database and owner name with special characters
  or embedded dots, use two sets of brackets::
  
      Table(
          "some_table", metadata,
          Column("q", String(50)),
          schema="[MyDataBase.Period].[MyOwner.Dot]"
      )
  
  
  .. versionchanged:: 1.2 the SQL Server dialect now treats brackets as
     identifier delimeters splitting the schema into separate database
     and owner tokens, to allow dots within either name itself.
  
  .. _legacy_schema_rendering:
  
  Legacy Schema Mode
  ------------------
  
  Very old versions of the MSSQL dialect introduced the behavior such that a
  schema-qualified table would be auto-aliased when used in a
  SELECT statement; given a table::
  
      account_table = Table(
          'account', metadata,
          Column('id', Integer, primary_key=True),
          Column('info', String(100)),
          schema="customer_schema"
      )
  
  this legacy mode of rendering would assume that "customer_schema.account"
  would not be accepted by all parts of the SQL statement, as illustrated
  below::
  
      >>> eng = create_engine("mssql+pymssql://mydsn", legacy_schema_aliasing=True)
      >>> print(account_table.select().compile(eng))
      SELECT account_1.id, account_1.info
      FROM customer_schema.account AS account_1
  
  This mode of behavior is now off by default, as it appears to have served
  no purpose; however in the case that legacy applications rely upon it,
  it is available using the ``legacy_schema_aliasing`` argument to
  :func:`.create_engine` as illustrated above.
  
  .. versionchanged:: 1.1 the ``legacy_schema_aliasing`` flag introduced
     in version 1.0.5 to allow disabling of legacy mode for schemas now
     defaults to False.
  
  
  .. _mssql_indexes:
  
  Clustered Index Support
  -----------------------
  
  The MSSQL dialect supports clustered indexes (and primary keys) via the
  ``mssql_clustered`` option.  This option is available to :class:`.Index`,
  :class:`.UniqueConstraint`. and :class:`.PrimaryKeyConstraint`.
  
  To generate a clustered index::
  
      Index("my_index", table.c.x, mssql_clustered=True)
  
  which renders the index as ``CREATE CLUSTERED INDEX my_index ON table (x)``.
  
  To generate a clustered primary key use::
  
      Table('my_table', metadata,
            Column('x', ...),
            Column('y', ...),
            PrimaryKeyConstraint("x", "y", mssql_clustered=True))
  
  which will render the table, for example, as::
  
    CREATE TABLE my_table (x INTEGER NOT NULL, y INTEGER NOT NULL,
                           PRIMARY KEY CLUSTERED (x, y))
  
  Similarly, we can generate a clustered unique constraint using::
  
      Table('my_table', metadata,
            Column('x', ...),
            Column('y', ...),
            PrimaryKeyConstraint("x"),
            UniqueConstraint("y", mssql_clustered=True),
            )
  
  To explicitly request a non-clustered primary key (for example, when
  a separate clustered index is desired), use::
  
      Table('my_table', metadata,
            Column('x', ...),
            Column('y', ...),
            PrimaryKeyConstraint("x", "y", mssql_clustered=False))
  
  which will render the table, for example, as::
  
    CREATE TABLE my_table (x INTEGER NOT NULL, y INTEGER NOT NULL,
                           PRIMARY KEY NONCLUSTERED (x, y))
  
  .. versionchanged:: 1.1 the ``mssql_clustered`` option now defaults
     to None, rather than False.  ``mssql_clustered=False`` now explicitly
     renders the NONCLUSTERED clause, whereas None omits the CLUSTERED
     clause entirely, allowing SQL Server defaults to take effect.
  
  
  MSSQL-Specific Index Options
  -----------------------------
  
  In addition to clustering, the MSSQL dialect supports other special options
  for :class:`.Index`.
  
  INCLUDE
  ^^^^^^^
  
  The ``mssql_include`` option renders INCLUDE(colname) for the given string
  names::
  
      Index("my_index", table.c.x, mssql_include=['y'])
  
  would render the index as ``CREATE INDEX my_index ON table (x) INCLUDE (y)``
  
  Index ordering
  ^^^^^^^^^^^^^^
  
  Index ordering is available via functional expressions, such as::
  
      Index("my_index", table.c.x.desc())
  
  would render the index as ``CREATE INDEX my_index ON table (x DESC)``
  
  .. seealso::
  
      :ref:`schema_indexes_functional`
  
  Compatibility Levels
  --------------------
  MSSQL supports the notion of setting compatibility levels at the
  database level. This allows, for instance, to run a database that
  is compatible with SQL2000 while running on a SQL2005 database
  server. ``server_version_info`` will always return the database
  server version information (in this case SQL2005) and not the
  compatibility level information. Because of this, if running under
  a backwards compatibility mode SQLAlchemy may attempt to use T-SQL
  statements that are unable to be parsed by the database server.
  
  Triggers
  --------
  
  SQLAlchemy by default uses OUTPUT INSERTED to get at newly
  generated primary key values via IDENTITY columns or other
  server side defaults.   MS-SQL does not
  allow the usage of OUTPUT INSERTED on tables that have triggers.
  To disable the usage of OUTPUT INSERTED on a per-table basis,
  specify ``implicit_returning=False`` for each :class:`.Table`
  which has triggers::
  
      Table('mytable', metadata,
          Column('id', Integer, primary_key=True),
          # ...,
          implicit_returning=False
      )
  
  Declarative form::
  
      class MyClass(Base):
          # ...
          __table_args__ = {'implicit_returning':False}
  
  
  This option can also be specified engine-wide using the
  ``implicit_returning=False`` argument on :func:`.create_engine`.
  
  .. _mssql_rowcount_versioning:
  
  Rowcount Support / ORM Versioning
  ---------------------------------
  
  The SQL Server drivers may have limited ability to return the number
  of rows updated from an UPDATE or DELETE statement.
  
  As of this writing, the PyODBC driver is not able to return a rowcount when
  OUTPUT INSERTED is used.  This impacts the SQLAlchemy ORM's versioning feature
  in many cases where server-side value generators are in use in that while the
  versioning operations can succeed, the ORM cannot always check that an UPDATE
  or DELETE statement matched the number of rows expected, which is how it
  verifies that the version identifier matched.   When this condition occurs, a
  warning will be emitted but the operation will proceed.
  
  The use of OUTPUT INSERTED can be disabled by setting the
  :paramref:`.Table.implicit_returning` flag to ``False`` on a particular
  :class:`.Table`, which in declarative looks like::
  
      class MyTable(Base):
          __tablename__ = 'mytable'
          id = Column(Integer, primary_key=True)
          stuff = Column(String(10))
          timestamp = Column(TIMESTAMP(), default=text('DEFAULT'))
          __mapper_args__ = {
              'version_id_col': timestamp,
              'version_id_generator': False,
          }
          __table_args__ = {
              'implicit_returning': False
          }
  
  Enabling Snapshot Isolation
  ---------------------------
  
  SQL Server has a default transaction
  isolation mode that locks entire tables, and causes even mildly concurrent
  applications to have long held locks and frequent deadlocks.
  Enabling snapshot isolation for the database as a whole is recommended
  for modern levels of concurrency support.  This is accomplished via the
  following ALTER DATABASE commands executed at the SQL prompt::
  
      ALTER DATABASE MyDatabase SET ALLOW_SNAPSHOT_ISOLATION ON
  
      ALTER DATABASE MyDatabase SET READ_COMMITTED_SNAPSHOT ON
  
  Background on SQL Server snapshot isolation is available at
  http://msdn.microsoft.com/en-us/library/ms175095.aspx.
  
  """  # noqa
  
  import codecs
  import datetime
  import operator
  import re
  
  from . import information_schema as ischema
  from ... import engine
  from ... import exc
  from ... import schema as sa_schema
  from ... import sql
  from ... import types as sqltypes
  from ... import util
  from ...engine import default
  from ...engine import reflection
  from ...sql import compiler
  from ...sql import expression
  from ...sql import quoted_name
  from ...sql import util as sql_util
  from ...types import BIGINT
  from ...types import BINARY
  from ...types import CHAR
  from ...types import DATE
  from ...types import DATETIME
  from ...types import DECIMAL
  from ...types import FLOAT
  from ...types import INTEGER
  from ...types import NCHAR
  from ...types import NUMERIC
  from ...types import NVARCHAR
  from ...types import SMALLINT
  from ...types import TEXT
  from ...types import VARCHAR
  from ...util import update_wrapper
  
  
  # http://sqlserverbuilds.blogspot.com/
  MS_2016_VERSION = (13,)
  MS_2014_VERSION = (12,)
  MS_2012_VERSION = (11,)
  MS_2008_VERSION = (10,)
  MS_2005_VERSION = (9,)
  MS_2000_VERSION = (8,)
  
  RESERVED_WORDS = set(
      [
          "add",
          "all",
          "alter",
          "and",
          "any",
          "as",
          "asc",
          "authorization",
          "backup",
          "begin",
          "between",
          "break",
          "browse",
          "bulk",
          "by",
          "cascade",
          "case",
          "check",
          "checkpoint",
          "close",
          "clustered",
          "coalesce",
          "collate",
          "column",
          "commit",
          "compute",
          "constraint",
          "contains",
          "containstable",
          "continue",
          "convert",
          "create",
          "cross",
          "current",
          "current_date",
          "current_time",
          "current_timestamp",
          "current_user",
          "cursor",
          "database",
          "dbcc",
          "deallocate",
          "declare",
          "default",
          "delete",
          "deny",
          "desc",
          "disk",
          "distinct",
          "distributed",
          "double",
          "drop",
          "dump",
          "else",
          "end",
          "errlvl",
          "escape",
          "except",
          "exec",
          "execute",
          "exists",
          "exit",
          "external",
          "fetch",
          "file",
          "fillfactor",
          "for",
          "foreign",
          "freetext",
          "freetexttable",
          "from",
          "full",
          "function",
          "goto",
          "grant",
          "group",
          "having",
          "holdlock",
          "identity",
          "identity_insert",
          "identitycol",
          "if",
          "in",
          "index",
          "inner",
          "insert",
          "intersect",
          "into",
          "is",
          "join",
          "key",
          "kill",
          "left",
          "like",
          "lineno",
          "load",
          "merge",
          "national",
          "nocheck",
          "nonclustered",
          "not",
          "null",
          "nullif",
          "of",
          "off",
          "offsets",
          "on",
          "open",
          "opendatasource",
          "openquery",
          "openrowset",
          "openxml",
          "option",
          "or",
          "order",
          "outer",
          "over",
          "percent",
          "pivot",
          "plan",
          "precision",
          "primary",
          "print",
          "proc",
          "procedure",
          "public",
          "raiserror",
          "read",
          "readtext",
          "reconfigure",
          "references",
          "replication",
          "restore",
          "restrict",
          "return",
          "revert",
          "revoke",
          "right",
          "rollback",
          "rowcount",
          "rowguidcol",
          "rule",
          "save",
          "schema",
          "securityaudit",
          "select",
          "session_user",
          "set",
          "setuser",
          "shutdown",
          "some",
          "statistics",
          "system_user",
          "table",
          "tablesample",
          "textsize",
          "then",
          "to",
          "top",
          "tran",
          "transaction",
          "trigger",
          "truncate",
          "tsequal",
          "union",
          "unique",
          "unpivot",
          "update",
          "updatetext",
          "use",
          "user",
          "values",
          "varying",
          "view",
          "waitfor",
          "when",
          "where",
          "while",
          "with",
          "writetext",
      ]
  )
  
  
  class REAL(sqltypes.REAL):
      __visit_name__ = "REAL"
  
      def __init__(self, **kw):
          # REAL is a synonym for FLOAT(24) on SQL server.
          # it is only accepted as the word "REAL" in DDL, the numeric
          # precision value is not allowed to be present
          kw.setdefault("precision", 24)
          super(REAL, self).__init__(**kw)
  
  
  class TINYINT(sqltypes.Integer):
      __visit_name__ = "TINYINT"
  
  
  # MSSQL DATE/TIME types have varied behavior, sometimes returning
  # strings.  MSDate/TIME check for everything, and always
  # filter bind parameters into datetime objects (required by pyodbc,
  # not sure about other dialects).
  
  
  class _MSDate(sqltypes.Date):
      def bind_processor(self, dialect):
          def process(value):
              if type(value) == datetime.date:
                  return datetime.datetime(value.year, value.month, value.day)
              else:
                  return value
  
          return process
  
      _reg = re.compile(r"(\d+)-(\d+)-(\d+)")
  
      def result_processor(self, dialect, coltype):
          def process(value):
              if isinstance(value, datetime.datetime):
                  return value.date()
              elif isinstance(value, util.string_types):
                  m = self._reg.match(value)
                  if not m:
                      raise ValueError(
                          "could not parse %r as a date value" % (value,)
                      )
                  return datetime.date(*[int(x or 0) for x in m.groups()])
              else:
                  return value
  
          return process
  
  
  class TIME(sqltypes.TIME):
      def __init__(self, precision=None, **kwargs):
          self.precision = precision
          super(TIME, self).__init__()
  
      __zero_date = datetime.date(1900, 1, 1)
  
      def bind_processor(self, dialect):
          def process(value):
              if isinstance(value, datetime.datetime):
                  value = datetime.datetime.combine(
                      self.__zero_date, value.time()
                  )
              elif isinstance(value, datetime.time):
                  value = datetime.datetime.combine(self.__zero_date, value)
              return value
  
          return process
  
      _reg = re.compile(r"(\d+):(\d+):(\d+)(?:\.(\d{0,6}))?")
  
      def result_processor(self, dialect, coltype):
          def process(value):
              if isinstance(value, datetime.datetime):
                  return value.time()
              elif isinstance(value, util.string_types):
                  m = self._reg.match(value)
                  if not m:
                      raise ValueError(
                          "could not parse %r as a time value" % (value,)
                      )
                  return datetime.time(*[int(x or 0) for x in m.groups()])
              else:
                  return value
  
          return process
  
  
  _MSTime = TIME
  
  
  class _DateTimeBase(object):
      def bind_processor(self, dialect):
          def process(value):
              if type(value) == datetime.date:
                  return datetime.datetime(value.year, value.month, value.day)
              else:
                  return value
  
          return process
  
  
  class _MSDateTime(_DateTimeBase, sqltypes.DateTime):
      pass
  
  
  class SMALLDATETIME(_DateTimeBase, sqltypes.DateTime):
      __visit_name__ = "SMALLDATETIME"
  
  
  class DATETIME2(_DateTimeBase, sqltypes.DateTime):
      __visit_name__ = "DATETIME2"
  
      def __init__(self, precision=None, **kw):
          super(DATETIME2, self).__init__(**kw)
          self.precision = precision
  
  
  # TODO: is this not an Interval ?
  class DATETIMEOFFSET(sqltypes.TypeEngine):
      __visit_name__ = "DATETIMEOFFSET"
  
      def __init__(self, precision=None, **kwargs):
          self.precision = precision
  
  
  class _UnicodeLiteral(object):
      def literal_processor(self, dialect):
          def process(value):
  
              value = value.replace("'", "''")
  
              if dialect.identifier_preparer._double_percents:
                  value = value.replace("%", "%%")
  
              return "N'%s'" % value
  
          return process
  
  
  class _MSUnicode(_UnicodeLiteral, sqltypes.Unicode):
      pass
  
  
  class _MSUnicodeText(_UnicodeLiteral, sqltypes.UnicodeText):
      pass
  
  
  class TIMESTAMP(sqltypes._Binary):
      """Implement the SQL Server TIMESTAMP type.
  
      Note this is **completely different** than the SQL Standard
      TIMESTAMP type, which is not supported by SQL Server.  It
      is a read-only datatype that does not support INSERT of values.
  
      .. versionadded:: 1.2
  
      .. seealso::
  
          :class:`.mssql.ROWVERSION`
  
      """
  
      __visit_name__ = "TIMESTAMP"
  
      # expected by _Binary to be present
      length = None
  
      def __init__(self, convert_int=False):
          """Construct a TIMESTAMP or ROWVERSION type.
  
          :param convert_int: if True, binary integer values will
           be converted to integers on read.
  
          .. versionadded:: 1.2
  
          """
          self.convert_int = convert_int
  
      def result_processor(self, dialect, coltype):
          super_ = super(TIMESTAMP, self).result_processor(dialect, coltype)
          if self.convert_int:
  
              def process(value):
                  value = super_(value)
                  if value is not None:
                      # https://stackoverflow.com/a/30403242/34549
                      value = int(codecs.encode(value, "hex"), 16)
                  return value
  
              return process
          else:
              return super_
  
  
  class ROWVERSION(TIMESTAMP):
      """Implement the SQL Server ROWVERSION type.
  
      The ROWVERSION datatype is a SQL Server synonym for the TIMESTAMP
      datatype, however current SQL Server documentation suggests using
      ROWVERSION for new datatypes going forward.
  
      The ROWVERSION datatype does **not** reflect (e.g. introspect) from the
      database as itself; the returned datatype will be
      :class:`.mssql.TIMESTAMP`.
  
      This is a read-only datatype that does not support INSERT of values.
  
      .. versionadded:: 1.2
  
      .. seealso::
  
          :class:`.mssql.TIMESTAMP`
  
      """
  
      __visit_name__ = "ROWVERSION"
  
  
  class NTEXT(sqltypes.UnicodeText):
  
      """MSSQL NTEXT type, for variable-length unicode text up to 2^30
      characters."""
  
      __visit_name__ = "NTEXT"
  
  
  class VARBINARY(sqltypes.VARBINARY, sqltypes.LargeBinary):
      """The MSSQL VARBINARY type.
  
      This type is present to support "deprecate_large_types" mode where
      either ``VARBINARY(max)`` or IMAGE is rendered.   Otherwise, this type
      object is redundant vs. :class:`.types.VARBINARY`.
  
      .. versionadded:: 1.0.0
  
      .. seealso::
  
          :ref:`mssql_large_type_deprecation`
  
  
  
      """
  
      __visit_name__ = "VARBINARY"
  
  
  class IMAGE(sqltypes.LargeBinary):
      __visit_name__ = "IMAGE"
  
  
  class XML(sqltypes.Text):
      """MSSQL XML type.
  
      This is a placeholder type for reflection purposes that does not include
      any Python-side datatype support.   It also does not currently support
      additional arguments, such as "CONTENT", "DOCUMENT",
      "xml_schema_collection".
  
      .. versionadded:: 1.1.11
  
      """
  
      __visit_name__ = "XML"
  
  
  class BIT(sqltypes.TypeEngine):
      __visit_name__ = "BIT"
  
  
  class MONEY(sqltypes.TypeEngine):
      __visit_name__ = "MONEY"
  
  
  class SMALLMONEY(sqltypes.TypeEngine):
      __visit_name__ = "SMALLMONEY"
  
  
  class UNIQUEIDENTIFIER(sqltypes.TypeEngine):
      __visit_name__ = "UNIQUEIDENTIFIER"
  
  
  class SQL_VARIANT(sqltypes.TypeEngine):
      __visit_name__ = "SQL_VARIANT"
  
  
  # old names.
  MSDateTime = _MSDateTime
  MSDate = _MSDate
  MSReal = REAL
  MSTinyInteger = TINYINT
  MSTime = TIME
  MSSmallDateTime = SMALLDATETIME
  MSDateTime2 = DATETIME2
  MSDateTimeOffset = DATETIMEOFFSET
  MSText = TEXT
  MSNText = NTEXT
  MSString = VARCHAR
  MSNVarchar = NVARCHAR
  MSChar = CHAR
  MSNChar = NCHAR
  MSBinary = BINARY
  MSVarBinary = VARBINARY
  MSImage = IMAGE
  MSBit = BIT
  MSMoney = MONEY
  MSSmallMoney = SMALLMONEY
  MSUniqueIdentifier = UNIQUEIDENTIFIER
  MSVariant = SQL_VARIANT
  
  ischema_names = {
      "int": INTEGER,
      "bigint": BIGINT,
      "smallint": SMALLINT,
      "tinyint": TINYINT,
      "varchar": VARCHAR,
      "nvarchar": NVARCHAR,
      "char": CHAR,
      "nchar": NCHAR,
      "text": TEXT,
      "ntext": NTEXT,
      "decimal": DECIMAL,
      "numeric": NUMERIC,
      "float": FLOAT,
      "datetime": DATETIME,
      "datetime2": DATETIME2,
      "datetimeoffset": DATETIMEOFFSET,
      "date": DATE,
      "time": TIME,
      "smalldatetime": SMALLDATETIME,
      "binary": BINARY,
      "varbinary": VARBINARY,
      "bit": BIT,
      "real": REAL,
      "image": IMAGE,
      "xml": XML,
      "timestamp": TIMESTAMP,
      "money": MONEY,
      "smallmoney": SMALLMONEY,
      "uniqueidentifier": UNIQUEIDENTIFIER,
      "sql_variant": SQL_VARIANT,
  }
  
  
  class MSTypeCompiler(compiler.GenericTypeCompiler):
      def _extend(self, spec, type_, length=None):
          """Extend a string-type declaration with standard SQL
          COLLATE annotations.
  
          """
  
          if getattr(type_, "collation", None):
              collation = "COLLATE %s" % type_.collation
          else:
              collation = None
  
          if not length:
              length = type_.length
  
          if length:
              spec = spec + "(%s)" % length
  
          return " ".join([c for c in (spec, collation) if c is not None])
  
      def visit_FLOAT(self, type_, **kw):
          precision = getattr(type_, "precision", None)
          if precision is None:
              return "FLOAT"
          else:
              return "FLOAT(%(precision)s)" % {"precision": precision}
  
      def visit_TINYINT(self, type_, **kw):
          return "TINYINT"
  
      def visit_DATETIMEOFFSET(self, type_, **kw):
          if type_.precision is not None:
              return "DATETIMEOFFSET(%s)" % type_.precision
          else:
              return "DATETIMEOFFSET"
  
      def visit_TIME(self, type_, **kw):
          precision = getattr(type_, "precision", None)
          if precision is not None:
              return "TIME(%s)" % precision
          else:
              return "TIME"
  
      def visit_TIMESTAMP(self, type_, **kw):
          return "TIMESTAMP"
  
      def visit_ROWVERSION(self, type_, **kw):
          return "ROWVERSION"
  
      def visit_DATETIME2(self, type_, **kw):
          precision = getattr(type_, "precision", None)
          if precision is not None:
              return "DATETIME2(%s)" % precision
          else:
              return "DATETIME2"
  
      def visit_SMALLDATETIME(self, type_, **kw):
          return "SMALLDATETIME"
  
      def visit_unicode(self, type_, **kw):
          return self.visit_NVARCHAR(type_, **kw)
  
      def visit_text(self, type_, **kw):
          if self.dialect.deprecate_large_types:
              return self.visit_VARCHAR(type_, **kw)
          else:
              return self.visit_TEXT(type_, **kw)
  
      def visit_unicode_text(self, type_, **kw):
          if self.dialect.deprecate_large_types:
              return self.visit_NVARCHAR(type_, **kw)
          else:
              return self.visit_NTEXT(type_, **kw)
  
      def visit_NTEXT(self, type_, **kw):
          return self._extend("NTEXT", type_)
  
      def visit_TEXT(self, type_, **kw):
          return self._extend("TEXT", type_)
  
      def visit_VARCHAR(self, type_, **kw):
          return self._extend("VARCHAR", type_, length=type_.length or "max")
  
      def visit_CHAR(self, type_, **kw):
          return self._extend("CHAR", type_)
  
      def visit_NCHAR(self, type_, **kw):
          return self._extend("NCHAR", type_)
  
      def visit_NVARCHAR(self, type_, **kw):
          return self._extend("NVARCHAR", type_, length=type_.length or "max")
  
      def visit_date(self, type_, **kw):
          if self.dialect.server_version_info < MS_2008_VERSION:
              return self.visit_DATETIME(type_, **kw)
          else:
              return self.visit_DATE(type_, **kw)
  
      def visit_time(self, type_, **kw):
          if self.dialect.server_version_info < MS_2008_VERSION:
              return self.visit_DATETIME(type_, **kw)
          else:
              return self.visit_TIME(type_, **kw)
  
      def visit_large_binary(self, type_, **kw):
          if self.dialect.deprecate_large_types:
              return self.visit_VARBINARY(type_, **kw)
          else:
              return self.visit_IMAGE(type_, **kw)
  
      def visit_IMAGE(self, type_, **kw):
          return "IMAGE"
  
      def visit_XML(self, type_, **kw):
          return "XML"
  
      def visit_VARBINARY(self, type_, **kw):
          return self._extend("VARBINARY", type_, length=type_.length or "max")
  
      def visit_boolean(self, type_, **kw):
          return self.visit_BIT(type_)
  
      def visit_BIT(self, type_, **kw):
          return "BIT"
  
      def visit_MONEY(self, type_, **kw):
          return "MONEY"
  
      def visit_SMALLMONEY(self, type_, **kw):
          return "SMALLMONEY"
  
      def visit_UNIQUEIDENTIFIER(self, type_, **kw):
          return "UNIQUEIDENTIFIER"
  
      def visit_SQL_VARIANT(self, type_, **kw):
          return "SQL_VARIANT"
  
  
  class MSExecutionContext(default.DefaultExecutionContext):
      _enable_identity_insert = False
      _select_lastrowid = False
      _result_proxy = None
      _lastrowid = None
  
      def _opt_encode(self, statement):
          if not self.dialect.supports_unicode_statements:
              return self.dialect._encoder(statement)[0]
          else:
              return statement
  
      def pre_exec(self):
          """Activate IDENTITY_INSERT if needed."""
  
          if self.isinsert:
              tbl = self.compiled.statement.table
              seq_column = tbl._autoincrement_column
              insert_has_sequence = seq_column is not None
  
              if insert_has_sequence:
                  self._enable_identity_insert = (
                      seq_column.key in self.compiled_parameters[0]
                  ) or (
                      self.compiled.statement.parameters
                      and (
                          (
                              self.compiled.statement._has_multi_parameters
                              and (
                                  seq_column.key
                                  in self.compiled.statement.parameters[0]
                                  or seq_column
                                  in self.compiled.statement.parameters[0]
                              )
                          )
                          or (
                              not self.compiled.statement._has_multi_parameters
                              and (
                                  seq_column.key
                                  in self.compiled.statement.parameters
                                  or seq_column
                                  in self.compiled.statement.parameters
                              )
                          )
                      )
                  )
              else:
                  self._enable_identity_insert = False
  
              self._select_lastrowid = (
                  not self.compiled.inline
                  and insert_has_sequence
                  and not self.compiled.returning
                  and not self._enable_identity_insert
                  and not self.executemany
              )
  
              if self._enable_identity_insert:
                  self.root_connection._cursor_execute(
                      self.cursor,
                      self._opt_encode(
                          "SET IDENTITY_INSERT %s ON"
                          % self.dialect.identifier_preparer.format_table(tbl)
                      ),
                      (),
                      self,
                  )
  
      def post_exec(self):
          """Disable IDENTITY_INSERT if enabled."""
  
          conn = self.root_connection
          if self._select_lastrowid:
              if self.dialect.use_scope_identity:
                  conn._cursor_execute(
                      self.cursor,
                      "SELECT scope_identity() AS lastrowid",
                      (),
                      self,
                  )
              else:
                  conn._cursor_execute(
                      self.cursor, "SELECT @@identity AS lastrowid", (), self
                  )
              # fetchall() ensures the cursor is consumed without closing it
              row = self.cursor.fetchall()[0]
              self._lastrowid = int(row[0])
  
          if (
              self.isinsert or self.isupdate or self.isdelete
          ) and self.compiled.returning:
              self._result_proxy = engine.FullyBufferedResultProxy(self)
  
          if self._enable_identity_insert:
              conn._cursor_execute(
                  self.cursor,
                  self._opt_encode(
                      "SET IDENTITY_INSERT %s OFF"
                      % self.dialect.identifier_preparer.format_table(
                          self.compiled.statement.table
                      )
                  ),
                  (),
                  self,
              )
  
      def get_lastrowid(self):
          return self._lastrowid
  
      def handle_dbapi_exception(self, e):
          if self._enable_identity_insert:
              try:
                  self.cursor.execute(
                      self._opt_encode(
                          "SET IDENTITY_INSERT %s OFF"
                          % self.dialect.identifier_preparer.format_table(
                              self.compiled.statement.table
                          )
                      )
                  )
              except Exception:
                  pass
  
      def get_result_proxy(self):
          if self._result_proxy:
              return self._result_proxy
          else:
              return engine.ResultProxy(self)
  
  
  class MSSQLCompiler(compiler.SQLCompiler):
      returning_precedes_values = True
  
      extract_map = util.update_copy(
          compiler.SQLCompiler.extract_map,
          {
              "doy": "dayofyear",
              "dow": "weekday",
              "milliseconds": "millisecond",
              "microseconds": "microsecond",
          },
      )
  
      def __init__(self, *args, **kwargs):
          self.tablealiases = {}
          super(MSSQLCompiler, self).__init__(*args, **kwargs)
  
      def _with_legacy_schema_aliasing(fn):
          def decorate(self, *arg, **kw):
              if self.dialect.legacy_schema_aliasing:
                  return fn(self, *arg, **kw)
              else:
                  super_ = getattr(super(MSSQLCompiler, self), fn.__name__)
                  return super_(*arg, **kw)
  
          return decorate
  
      def visit_now_func(self, fn, **kw):
          return "CURRENT_TIMESTAMP"
  
      def visit_current_date_func(self, fn, **kw):
          return "GETDATE()"
  
      def visit_length_func(self, fn, **kw):
          return "LEN%s" % self.function_argspec(fn, **kw)
  
      def visit_char_length_func(self, fn, **kw):
          return "LEN%s" % self.function_argspec(fn, **kw)
  
      def visit_concat_op_binary(self, binary, operator, **kw):
          return "%s + %s" % (
              self.process(binary.left, **kw),
              self.process(binary.right, **kw),
          )
  
      def visit_true(self, expr, **kw):
          return "1"
  
      def visit_false(self, expr, **kw):
          return "0"
  
      def visit_match_op_binary(self, binary, operator, **kw):
          return "CONTAINS (%s, %s)" % (
              self.process(binary.left, **kw),
              self.process(binary.right, **kw),
          )
  
      def get_select_precolumns(self, select, **kw):
          """ MS-SQL puts TOP, it's version of LIMIT here """
  
          s = ""
          if select._distinct:
              s += "DISTINCT "
  
          if select._simple_int_limit and not select._offset:
              # ODBC drivers and possibly others
              # don't support bind params in the SELECT clause on SQL Server.
              # so have to use literal here.
              s += "TOP %d " % select._limit
  
          if s:
              return s
          else:
              return compiler.SQLCompiler.get_select_precolumns(
                  self, select, **kw
              )
  
      def get_from_hint_text(self, table, text):
          return text
  
      def get_crud_hint_text(self, table, text):
          return text
  
      def limit_clause(self, select, **kw):
          # Limit in mssql is after the select keyword
          return ""
  
      def visit_select(self, select, **kwargs):
          """Look for ``LIMIT`` and OFFSET in a select statement, and if
          so tries to wrap it in a subquery with ``row_number()`` criterion.
  
          """
          if (
              (not select._simple_int_limit and select._limit_clause is not None)
              or (
                  select._offset_clause is not None
                  and not select._simple_int_offset
                  or select._offset
              )
          ) and not getattr(select, "_mssql_visit", None):
  
              # to use ROW_NUMBER(), an ORDER BY is required.
              if not select._order_by_clause.clauses:
                  raise exc.CompileError(
                      "MSSQL requires an order_by when "
                      "using an OFFSET or a non-simple "
                      "LIMIT clause"
                  )
  
              _order_by_clauses = [
                  sql_util.unwrap_label_reference(elem)
                  for elem in select._order_by_clause.clauses
              ]
  
              limit_clause = select._limit_clause
              offset_clause = select._offset_clause
              kwargs["select_wraps_for"] = select
              select = select._generate()
              select._mssql_visit = True
              select = (
                  select.column(
                      sql.func.ROW_NUMBER()
                      .over(order_by=_order_by_clauses)
                      .label("mssql_rn")
                  )
                  .order_by(None)
                  .alias()
              )
  
              mssql_rn = sql.column("mssql_rn")
              limitselect = sql.select(
                  [c for c in select.c if c.key != "mssql_rn"]
              )
              if offset_clause is not None:
                  limitselect.append_whereclause(mssql_rn > offset_clause)
                  if limit_clause is not None:
                      limitselect.append_whereclause(
                          mssql_rn <= (limit_clause + offset_clause)
                      )
              else:
                  limitselect.append_whereclause(mssql_rn <= (limit_clause))
              return self.process(limitselect, **kwargs)
          else:
              return compiler.SQLCompiler.visit_select(self, select, **kwargs)
  
      @_with_legacy_schema_aliasing
      def visit_table(self, table, mssql_aliased=False, iscrud=False, **kwargs):
          if mssql_aliased is table or iscrud:
              return super(MSSQLCompiler, self).visit_table(table, **kwargs)
  
          # alias schema-qualified tables
          alias = self._schema_aliased_table(table)
          if alias is not None:
              return self.process(alias, mssql_aliased=table, **kwargs)
          else:
              return super(MSSQLCompiler, self).visit_table(table, **kwargs)
  
      @_with_legacy_schema_aliasing
      def visit_alias(self, alias, **kw):
          # translate for schema-qualified table aliases
          kw["mssql_aliased"] = alias.original
          return super(MSSQLCompiler, self).visit_alias(alias, **kw)
  
      @_with_legacy_schema_aliasing
      def visit_column(self, column, add_to_result_map=None, **kw):
          if (
              column.table is not None
              and (not self.isupdate and not self.isdelete)
              or self.is_subquery()
          ):
              # translate for schema-qualified table aliases
              t = self._schema_aliased_table(column.table)
              if t is not None:
                  converted = expression._corresponding_column_or_error(
                      t, column
                  )
                  if add_to_result_map is not None:
                      add_to_result_map(
                          column.name,
                          column.name,
                          (column, column.name, column.key),
                          column.type,
                      )
  
                  return super(MSSQLCompiler, self).visit_column(converted, **kw)
  
          return super(MSSQLCompiler, self).visit_column(
              column, add_to_result_map=add_to_result_map, **kw
          )
  
      def _schema_aliased_table(self, table):
          if getattr(table, "schema", None) is not None:
              if table not in self.tablealiases:
                  self.tablealiases[table] = table.alias()
              return self.tablealiases[table]
          else:
              return None
  
      def visit_extract(self, extract, **kw):
          field = self.extract_map.get(extract.field, extract.field)
          return "DATEPART(%s, %s)" % (field, self.process(extract.expr, **kw))
  
      def visit_savepoint(self, savepoint_stmt):
          return "SAVE TRANSACTION %s" % self.preparer.format_savepoint(
              savepoint_stmt
          )
  
      def visit_rollback_to_savepoint(self, savepoint_stmt):
          return "ROLLBACK TRANSACTION %s" % self.preparer.format_savepoint(
              savepoint_stmt
          )
  
      def visit_binary(self, binary, **kwargs):
          """Move bind parameters to the right-hand side of an operator, where
          possible.
  
          """
          if (
              isinstance(binary.left, expression.BindParameter)
              and binary.operator == operator.eq
              and not isinstance(binary.right, expression.BindParameter)
          ):
              return self.process(
                  expression.BinaryExpression(
                      binary.right, binary.left, binary.operator
                  ),
                  **kwargs
              )
          return super(MSSQLCompiler, self).visit_binary(binary, **kwargs)
  
      def returning_clause(self, stmt, returning_cols):
  
          if self.isinsert or self.isupdate:
              target = stmt.table.alias("inserted")
          else:
              target = stmt.table.alias("deleted")
  
          adapter = sql_util.ClauseAdapter(target)
  
          columns = [
              self._label_select_column(
                  None, adapter.traverse(c), True, False, {}
              )
              for c in expression._select_iterables(returning_cols)
          ]
  
          return "OUTPUT " + ", ".join(columns)
  
      def get_cte_preamble(self, recursive):
          # SQL Server finds it too inconvenient to accept
          # an entirely optional, SQL standard specified,
          # "RECURSIVE" word with their "WITH",
          # so here we go
          return "WITH"
  
      def label_select_column(self, select, column, asfrom):
          if isinstance(column, expression.Function):
              return column.label(None)
          else:
              return super(MSSQLCompiler, self).label_select_column(
                  select, column, asfrom
              )
  
      def for_update_clause(self, select):
          # "FOR UPDATE" is only allowed on "DECLARE CURSOR" which
          # SQLAlchemy doesn't use
          return ""
  
      def order_by_clause(self, select, **kw):
          order_by = self.process(select._order_by_clause, **kw)
  
          # MSSQL only allows ORDER BY in subqueries if there is a LIMIT
          if order_by and (not self.is_subquery() or select._limit):
              return " ORDER BY " + order_by
          else:
              return ""
  
      def update_from_clause(
          self, update_stmt, from_table, extra_froms, from_hints, **kw
      ):
          """Render the UPDATE..FROM clause specific to MSSQL.
  
          In MSSQL, if the UPDATE statement involves an alias of the table to
          be updated, then the table itself must be added to the FROM list as
          well. Otherwise, it is optional. Here, we add it regardless.
  
          """
          return "FROM " + ", ".join(
              t._compiler_dispatch(self, asfrom=True, fromhints=from_hints, **kw)
              for t in [from_table] + extra_froms
          )
  
      def delete_table_clause(self, delete_stmt, from_table, extra_froms):
          """If we have extra froms make sure we render any alias as hint."""
          ashint = False
          if extra_froms:
              ashint = True
          return from_table._compiler_dispatch(
              self, asfrom=True, iscrud=True, ashint=ashint
          )
  
      def delete_extra_from_clause(
          self, delete_stmt, from_table, extra_froms, from_hints, **kw
      ):
          """Render the DELETE .. FROM clause specific to MSSQL.
  
          Yes, it has the FROM keyword twice.
  
          """
          return "FROM " + ", ".join(
              t._compiler_dispatch(self, asfrom=True, fromhints=from_hints, **kw)
              for t in [from_table] + extra_froms
          )
  
      def visit_empty_set_expr(self, type_):
          return "SELECT 1 WHERE 1!=1"
  
  
  class MSSQLStrictCompiler(MSSQLCompiler):
  
      """A subclass of MSSQLCompiler which disables the usage of bind
      parameters where not allowed natively by MS-SQL.
  
      A dialect may use this compiler on a platform where native
      binds are used.
  
      """
  
      ansi_bind_rules = True
  
      def visit_in_op_binary(self, binary, operator, **kw):
          kw["literal_binds"] = True
          return "%s IN %s" % (
              self.process(binary.left, **kw),
              self.process(binary.right, **kw),
          )
  
      def visit_notin_op_binary(self, binary, operator, **kw):
          kw["literal_binds"] = True
          return "%s NOT IN %s" % (
              self.process(binary.left, **kw),
              self.process(binary.right, **kw),
          )
  
      def render_literal_value(self, value, type_):
          """
          For date and datetime values, convert to a string
          format acceptable to MSSQL. That seems to be the
          so-called ODBC canonical date format which looks
          like this:
  
              yyyy-mm-dd hh:mi:ss.mmm(24h)
  
          For other data types, call the base class implementation.
          """
          # datetime and date are both subclasses of datetime.date
          if issubclass(type(value), datetime.date):
              # SQL Server wants single quotes around the date string.
              return "'" + str(value) + "'"
          else:
              return super(MSSQLStrictCompiler, self).render_literal_value(
                  value, type_
              )
  
  
  class MSDDLCompiler(compiler.DDLCompiler):
      def get_column_specification(self, column, **kwargs):
          colspec = (
              self.preparer.format_column(column)
              + " "
              + self.dialect.type_compiler.process(
                  column.type, type_expression=column
              )
          )
  
          if column.nullable is not None:
              if (
                  not column.nullable
                  or column.primary_key
                  or isinstance(column.default, sa_schema.Sequence)
                  or column.autoincrement is True
              ):
                  colspec += " NOT NULL"
              else:
                  colspec += " NULL"
  
          if column.table is None:
              raise exc.CompileError(
                  "mssql requires Table-bound columns "
                  "in order to generate DDL"
              )
  
          # install an IDENTITY Sequence if we either a sequence or an implicit
          # IDENTITY column
          if isinstance(column.default, sa_schema.Sequence):
  
              if (
                  column.default.start is not None
                  or column.default.increment is not None
                  or column is not column.table._autoincrement_column
              ):
                  util.warn_deprecated(
                      "Use of Sequence with SQL Server in order to affect the "
                      "parameters of the IDENTITY value is deprecated, as "
                      "Sequence "
                      "will correspond to an actual SQL Server "
                      "CREATE SEQUENCE in "
                      "a future release.  Please use the mssql_identity_start "
                      "and mssql_identity_increment parameters."
                  )
              if column.default.start == 0:
                  start = 0
              else:
                  start = column.default.start or 1
  
              colspec += " IDENTITY(%s,%s)" % (
                  start,
                  column.default.increment or 1,
              )
          elif (
              column is column.table._autoincrement_column
              or column.autoincrement is True
          ):
              start = column.dialect_options["mssql"]["identity_start"]
              increment = column.dialect_options["mssql"]["identity_increment"]
              colspec += " IDENTITY(%s,%s)" % (start, increment)
          else:
              default = self.get_column_default_string(column)
              if default is not None:
                  colspec += " DEFAULT " + default
  
          return colspec
  
      def visit_create_index(self, create, include_schema=False):
          index = create.element
          self._verify_index_table(index)
          preparer = self.preparer
          text = "CREATE "
          if index.unique:
              text += "UNIQUE "
  
          # handle clustering option
          clustered = index.dialect_options["mssql"]["clustered"]
          if clustered is not None:
              if clustered:
                  text += "CLUSTERED "
              else:
                  text += "NONCLUSTERED "
  
          text += "INDEX %s ON %s (%s)" % (
              self._prepared_index_name(index, include_schema=include_schema),
              preparer.format_table(index.table),
              ", ".join(
                  self.sql_compiler.process(
                      expr, include_table=False, literal_binds=True
                  )
                  for expr in index.expressions
              ),
          )
  
          # handle other included columns
          if index.dialect_options["mssql"]["include"]:
              inclusions = [
                  index.table.c[col]
                  if isinstance(col, util.string_types)
                  else col
                  for col in index.dialect_options["mssql"]["include"]
              ]
  
              text += " INCLUDE (%s)" % ", ".join(
                  [preparer.quote(c.name) for c in inclusions]
              )
  
          return text
  
      def visit_drop_index(self, drop):
          return "\nDROP INDEX %s ON %s" % (
              self._prepared_index_name(drop.element, include_schema=False),
              self.preparer.format_table(drop.element.table),
          )
  
      def visit_primary_key_constraint(self, constraint):
          if len(constraint) == 0:
              return ""
          text = ""
          if constraint.name is not None:
              text += "CONSTRAINT %s " % self.preparer.format_constraint(
                  constraint
              )
          text += "PRIMARY KEY "
  
          clustered = constraint.dialect_options["mssql"]["clustered"]
          if clustered is not None:
              if clustered:
                  text += "CLUSTERED "
              else:
                  text += "NONCLUSTERED "
  
          text += "(%s)" % ", ".join(
              self.preparer.quote(c.name) for c in constraint
          )
          text += self.define_constraint_deferrability(constraint)
          return text
  
      def visit_unique_constraint(self, constraint):
          if len(constraint) == 0:
              return ""
          text = ""
          if constraint.name is not None:
              text += "CONSTRAINT %s " % self.preparer.format_constraint(
                  constraint
              )
          text += "UNIQUE "
  
          clustered = constraint.dialect_options["mssql"]["clustered"]
          if clustered is not None:
              if clustered:
                  text += "CLUSTERED "
              else:
                  text += "NONCLUSTERED "
  
          text += "(%s)" % ", ".join(
              self.preparer.quote(c.name) for c in constraint
          )
          text += self.define_constraint_deferrability(constraint)
          return text
  
  
  class MSIdentifierPreparer(compiler.IdentifierPreparer):
      reserved_words = RESERVED_WORDS
  
      def __init__(self, dialect):
          super(MSIdentifierPreparer, self).__init__(
              dialect,
              initial_quote="[",
              final_quote="]",
              quote_case_sensitive_collations=False,
          )
  
      def _escape_identifier(self, value):
          return value
  
      def quote_schema(self, schema, force=None):
          """Prepare a quoted table and schema name."""
  
          # need to re-implement the deprecation warning entirely
          if force is not None:
              # not using the util.deprecated_params() decorator in this
              # case because of the additional function call overhead on this
              # very performance-critical spot.
              util.warn_deprecated(
                  "The IdentifierPreparer.quote_schema.force parameter is "
                  "deprecated and will be removed in a future release.  This "
                  "flag has no effect on the behavior of the "
                  "IdentifierPreparer.quote method; please refer to "
                  "quoted_name()."
              )
  
          dbname, owner = _schema_elements(schema)
          if dbname:
              result = "%s.%s" % (self.quote(dbname), self.quote(owner))
          elif owner:
              result = self.quote(owner)
          else:
              result = ""
          return result
  
  
  def _db_plus_owner_listing(fn):
      def wrap(dialect, connection, schema=None, **kw):
          dbname, owner = _owner_plus_db(dialect, schema)
          return _switch_db(
              dbname,
              connection,
              fn,
              dialect,
              connection,
              dbname,
              owner,
              schema,
              **kw
          )
  
      return update_wrapper(wrap, fn)
  
  
  def _db_plus_owner(fn):
      def wrap(dialect, connection, tablename, schema=None, **kw):
          dbname, owner = _owner_plus_db(dialect, schema)
          return _switch_db(
              dbname,
              connection,
              fn,
              dialect,
              connection,
              tablename,
              dbname,
              owner,
              schema,
              **kw
          )
  
      return update_wrapper(wrap, fn)
  
  
  def _switch_db(dbname, connection, fn, *arg, **kw):
      if dbname:
          current_db = connection.scalar("select db_name()")
          connection.execute("use %s" % dbname)
      try:
          return fn(*arg, **kw)
      finally:
          if dbname:
              connection.execute("use %s" % current_db)
  
  
  def _owner_plus_db(dialect, schema):
      if not schema:
          return None, dialect.default_schema_name
      elif "." in schema:
          return _schema_elements(schema)
      else:
          return None, schema
  
  
  def _schema_elements(schema):
      if isinstance(schema, quoted_name) and schema.quote:
          return None, schema
  
      push = []
      symbol = ""
      bracket = False
      for token in re.split(r"(\[|\]|\.)", schema):
          if not token:
              continue
          if token == "[":
              bracket = True
          elif token == "]":
              bracket = False
          elif not bracket and token == ".":
              push.append(symbol)
              symbol = ""
          else:
              symbol += token
      if symbol:
          push.append(symbol)
      if len(push) > 1:
          return push[0], "".join(push[1:])
      elif len(push):
          return None, push[0]
      else:
          return None, None
  
  
  class MSDialect(default.DefaultDialect):
      name = "mssql"
      supports_default_values = True
      supports_empty_insert = False
      execution_ctx_cls = MSExecutionContext
      use_scope_identity = True
      max_identifier_length = 128
      schema_name = "dbo"
  
      colspecs = {
          sqltypes.DateTime: _MSDateTime,
          sqltypes.Date: _MSDate,
          sqltypes.Time: TIME,
          sqltypes.Unicode: _MSUnicode,
          sqltypes.UnicodeText: _MSUnicodeText,
      }
  
      engine_config_types = default.DefaultDialect.engine_config_types.union(
          [("legacy_schema_aliasing", util.asbool)]
      )
  
      ischema_names = ischema_names
  
      supports_native_boolean = False
      non_native_boolean_check_constraint = False
      supports_unicode_binds = True
      postfetch_lastrowid = True
  
      server_version_info = ()
  
      statement_compiler = MSSQLCompiler
      ddl_compiler = MSDDLCompiler
      type_compiler = MSTypeCompiler
      preparer = MSIdentifierPreparer
  
      construct_arguments = [
          (sa_schema.PrimaryKeyConstraint, {"clustered": None}),
          (sa_schema.UniqueConstraint, {"clustered": None}),
          (sa_schema.Index, {"clustered": None, "include": None}),
          (sa_schema.Column, {"identity_start": 1, "identity_increment": 1}),
      ]
  
      def __init__(
          self,
          query_timeout=None,
          use_scope_identity=True,
          max_identifier_length=None,
          schema_name="dbo",
          isolation_level=None,
          deprecate_large_types=None,
          legacy_schema_aliasing=False,
          **opts
      ):
          self.query_timeout = int(query_timeout or 0)
          self.schema_name = schema_name
  
          self.use_scope_identity = use_scope_identity
          self.max_identifier_length = (
              int(max_identifier_length or 0) or self.max_identifier_length
          )
          self.deprecate_large_types = deprecate_large_types
          self.legacy_schema_aliasing = legacy_schema_aliasing
  
          super(MSDialect, self).__init__(**opts)
  
          self.isolation_level = isolation_level
  
      def do_savepoint(self, connection, name):
          # give the DBAPI a push
          connection.execute("IF @@TRANCOUNT = 0 BEGIN TRANSACTION")
          super(MSDialect, self).do_savepoint(connection, name)
  
      def do_release_savepoint(self, connection, name):
          # SQL Server does not support RELEASE SAVEPOINT
          pass
  
      _isolation_lookup = set(
          [
              "SERIALIZABLE",
              "READ UNCOMMITTED",
              "READ COMMITTED",
              "REPEATABLE READ",
              "SNAPSHOT",
          ]
      )
  
      def set_isolation_level(self, connection, level):
          level = level.replace("_", " ")
          if level not in self._isolation_lookup:
              raise exc.ArgumentError(
                  "Invalid value '%s' for isolation_level. "
                  "Valid isolation levels for %s are %s"
                  % (level, self.name, ", ".join(self._isolation_lookup))
              )
          cursor = connection.cursor()
          cursor.execute("SET TRANSACTION ISOLATION LEVEL %s" % level)
          cursor.close()
          if level == "SNAPSHOT":
              connection.commit()
  
      def get_isolation_level(self, connection):
          if self.server_version_info < MS_2005_VERSION:
              raise NotImplementedError(
                  "Can't fetch isolation level prior to SQL Server 2005"
              )
  
          last_error = None
  
          views = ("sys.dm_exec_sessions", "sys.dm_pdw_nodes_exec_sessions")
          for view in views:
              cursor = connection.cursor()
              try:
                  cursor.execute(
                      """
                    SELECT CASE transaction_isolation_level
                      WHEN 0 THEN NULL
                      WHEN 1 THEN 'READ UNCOMMITTED'
                      WHEN 2 THEN 'READ COMMITTED'
                      WHEN 3 THEN 'REPEATABLE READ'
                      WHEN 4 THEN 'SERIALIZABLE'
                      WHEN 5 THEN 'SNAPSHOT' END AS TRANSACTION_ISOLATION_LEVEL
                      FROM %s
                      where session_id = @@SPID
                    """
                      % view
                  )
                  val = cursor.fetchone()[0]
              except self.dbapi.Error as err:
                  # Python3 scoping rules
                  last_error = err
                  continue
              else:
                  return val.upper()
              finally:
                  cursor.close()
          else:
              util.warn(
                  "Could not fetch transaction isolation level, "
                  "tried views: %s; final error was: %s" % (views, last_error)
              )
  
              raise NotImplementedError(
                  "Can't fetch isolation level on this particular "
                  "SQL Server version"
              )
  
      def initialize(self, connection):
          super(MSDialect, self).initialize(connection)
          self._setup_version_attributes()
  
      def on_connect(self):
          if self.isolation_level is not None:
  
              def connect(conn):
                  self.set_isolation_level(conn, self.isolation_level)
  
              return connect
          else:
              return None
  
      def _setup_version_attributes(self):
          if self.server_version_info[0] not in list(range(8, 17)):
              util.warn(
                  "Unrecognized server version info '%s'.  Some SQL Server "
                  "features may not function properly."
                  % ".".join(str(x) for x in self.server_version_info)
              )
          if (
              self.server_version_info >= MS_2005_VERSION
              and "implicit_returning" not in self.__dict__
          ):
              self.implicit_returning = True
          if self.server_version_info >= MS_2008_VERSION:
              self.supports_multivalues_insert = True
          if self.deprecate_large_types is None:
              self.deprecate_large_types = (
                  self.server_version_info >= MS_2012_VERSION
              )
  
      def _get_default_schema_name(self, connection):
          if self.server_version_info < MS_2005_VERSION:
              return self.schema_name
          else:
              query = sql.text("SELECT schema_name()")
              default_schema_name = connection.scalar(query)
              if default_schema_name is not None:
                  return util.text_type(default_schema_name)
              else:
                  return self.schema_name
  
      @_db_plus_owner
      def has_table(self, connection, tablename, dbname, owner, schema):
          columns = ischema.columns
  
          whereclause = columns.c.table_name == tablename
  
          if owner:
              whereclause = sql.and_(
                  whereclause, columns.c.table_schema == owner
              )
          s = sql.select([columns], whereclause)
          c = connection.execute(s)
          return c.first() is not None
  
      @reflection.cache
      def get_schema_names(self, connection, **kw):
          s = sql.select(
              [ischema.schemata.c.schema_name],
              order_by=[ischema.schemata.c.schema_name],
          )
          schema_names = [r[0] for r in connection.execute(s)]
          return schema_names
  
      @reflection.cache
      @_db_plus_owner_listing
      def get_table_names(self, connection, dbname, owner, schema, **kw):
          tables = ischema.tables
          s = sql.select(
              [tables.c.table_name],
              sql.and_(
                  tables.c.table_schema == owner,
                  tables.c.table_type == "BASE TABLE",
              ),
              order_by=[tables.c.table_name],
          )
          table_names = [r[0] for r in connection.execute(s)]
          return table_names
  
      @reflection.cache
      @_db_plus_owner_listing
      def get_view_names(self, connection, dbname, owner, schema, **kw):
          tables = ischema.tables
          s = sql.select(
              [tables.c.table_name],
              sql.and_(
                  tables.c.table_schema == owner, tables.c.table_type == "VIEW"
              ),
              order_by=[tables.c.table_name],
          )
          view_names = [r[0] for r in connection.execute(s)]
          return view_names
  
      @reflection.cache
      @_db_plus_owner
      def get_indexes(self, connection, tablename, dbname, owner, schema, **kw):
          # using system catalogs, don't support index reflection
          # below MS 2005
          if self.server_version_info < MS_2005_VERSION:
              return []
  
          rp = connection.execute(
              sql.text(
                  "select ind.index_id, ind.is_unique, ind.name "
                  "from sys.indexes as ind join sys.tables as tab on "
                  "ind.object_id=tab.object_id "
                  "join sys.schemas as sch on sch.schema_id=tab.schema_id "
                  "where tab.name = :tabname "
                  "and sch.name=:schname "
                  "and ind.is_primary_key=0 and ind.type != 0"
              )
              .bindparams(
                  sql.bindparam("tabname", tablename, sqltypes.String()),
                  sql.bindparam("schname", owner, sqltypes.String()),
              )
              .columns(name=sqltypes.Unicode())
          )
          indexes = {}
          for row in rp:
              indexes[row["index_id"]] = {
                  "name": row["name"],
                  "unique": row["is_unique"] == 1,
                  "column_names": [],
              }
          rp = connection.execute(
              sql.text(
                  "select ind_col.index_id, ind_col.object_id, col.name "
                  "from sys.columns as col "
                  "join sys.tables as tab on tab.object_id=col.object_id "
                  "join sys.index_columns as ind_col on "
                  "(ind_col.column_id=col.column_id and "
                  "ind_col.object_id=tab.object_id) "
                  "join sys.schemas as sch on sch.schema_id=tab.schema_id "
                  "where tab.name=:tabname "
                  "and sch.name=:schname"
              )
              .bindparams(
                  sql.bindparam("tabname", tablename, sqltypes.String()),
                  sql.bindparam("schname", owner, sqltypes.String()),
              )
              .columns(name=sqltypes.Unicode())
          )
          for row in rp:
              if row["index_id"] in indexes:
                  indexes[row["index_id"]]["column_names"].append(row["name"])
  
          return list(indexes.values())
  
      @reflection.cache
      @_db_plus_owner
      def get_view_definition(
          self, connection, viewname, dbname, owner, schema, **kw
      ):
          rp = connection.execute(
              sql.text(
                  "select definition from sys.sql_modules as mod, "
                  "sys.views as views, "
                  "sys.schemas as sch"
                  " where "
                  "mod.object_id=views.object_id and "
                  "views.schema_id=sch.schema_id and "
                  "views.name=:viewname and sch.name=:schname"
              ).bindparams(
                  sql.bindparam("viewname", viewname, sqltypes.String()),
                  sql.bindparam("schname", owner, sqltypes.String()),
              )
          )
  
          if rp:
              view_def = rp.scalar()
              return view_def
  
      @reflection.cache
      @_db_plus_owner
      def get_columns(self, connection, tablename, dbname, owner, schema, **kw):
          # Get base columns
          columns = ischema.columns
          if owner:
              whereclause = sql.and_(
                  columns.c.table_name == tablename,
                  columns.c.table_schema == owner,
              )
          else:
              whereclause = columns.c.table_name == tablename
          s = sql.select(
              [columns], whereclause, order_by=[columns.c.ordinal_position]
          )
  
          c = connection.execute(s)
          cols = []
          while True:
              row = c.fetchone()
              if row is None:
                  break
              (
                  name,
                  type_,
                  nullable,
                  charlen,
                  numericprec,
                  numericscale,
                  default,
                  collation,
              ) = (
                  row[columns.c.column_name],
                  row[columns.c.data_type],
                  row[columns.c.is_nullable] == "YES",
                  row[columns.c.character_maximum_length],
                  row[columns.c.numeric_precision],
                  row[columns.c.numeric_scale],
                  row[columns.c.column_default],
                  row[columns.c.collation_name],
              )
              coltype = self.ischema_names.get(type_, None)
  
              kwargs = {}
              if coltype in (
                  MSString,
                  MSChar,
                  MSNVarchar,
                  MSNChar,
                  MSText,
                  MSNText,
                  MSBinary,
                  MSVarBinary,
                  sqltypes.LargeBinary,
              ):
                  if charlen == -1:
                      charlen = None
                  kwargs["length"] = charlen
                  if collation:
                      kwargs["collation"] = collation
  
              if coltype is None:
                  util.warn(
                      "Did not recognize type '%s' of column '%s'"
                      % (type_, name)
                  )
                  coltype = sqltypes.NULLTYPE
              else:
                  if issubclass(coltype, sqltypes.Numeric):
                      kwargs["precision"] = numericprec
  
                      if not issubclass(coltype, sqltypes.Float):
                          kwargs["scale"] = numericscale
  
                  coltype = coltype(**kwargs)
              cdict = {
                  "name": name,
                  "type": coltype,
                  "nullable": nullable,
                  "default": default,
                  "autoincrement": False,
              }
              cols.append(cdict)
          # autoincrement and identity
          colmap = {}
          for col in cols:
              colmap[col["name"]] = col
          # We also run an sp_columns to check for identity columns:
          cursor = connection.execute(
              "sp_columns @table_name = '%s', "
              "@table_owner = '%s'" % (tablename, owner)
          )
          ic = None
          while True:
              row = cursor.fetchone()
              if row is None:
                  break
              (col_name, type_name) = row[3], row[5]
              if type_name.endswith("identity") and col_name in colmap:
                  ic = col_name
                  colmap[col_name]["autoincrement"] = True
                  colmap[col_name]["dialect_options"] = {
                      "mssql_identity_start": 1,
                      "mssql_identity_increment": 1,
                  }
                  break
          cursor.close()
  
          if ic is not None and self.server_version_info >= MS_2005_VERSION:
              table_fullname = "%s.%s" % (owner, tablename)
              cursor = connection.execute(
                  "select ident_seed('%s'), ident_incr('%s')"
                  % (table_fullname, table_fullname)
              )
  
              row = cursor.first()
              if row is not None and row[0] is not None:
                  colmap[ic]["dialect_options"].update(
                      {
                          "mssql_identity_start": int(row[0]),
                          "mssql_identity_increment": int(row[1]),
                      }
                  )
          return cols
  
      @reflection.cache
      @_db_plus_owner
      def get_pk_constraint(
          self, connection, tablename, dbname, owner, schema, **kw
      ):
          pkeys = []
          TC = ischema.constraints
          C = ischema.key_constraints.alias("C")
  
          # Primary key constraints
          s = sql.select(
              [C.c.column_name, TC.c.constraint_type, C.c.constraint_name],
              sql.and_(
                  TC.c.constraint_name == C.c.constraint_name,
                  TC.c.table_schema == C.c.table_schema,
                  C.c.table_name == tablename,
                  C.c.table_schema == owner,
              ),
          )
          c = connection.execute(s)
          constraint_name = None
          for row in c:
              if "PRIMARY" in row[TC.c.constraint_type.name]:
                  pkeys.append(row[0])
                  if constraint_name is None:
                      constraint_name = row[C.c.constraint_name.name]
          return {"constrained_columns": pkeys, "name": constraint_name}
  
      @reflection.cache
      @_db_plus_owner
      def get_foreign_keys(
          self, connection, tablename, dbname, owner, schema, **kw
      ):
          RR = ischema.ref_constraints
          C = ischema.key_constraints.alias("C")
          R = ischema.key_constraints.alias("R")
  
          # Foreign key constraints
          s = sql.select(
              [
                  C.c.column_name,
                  R.c.table_schema,
                  R.c.table_name,
                  R.c.column_name,
                  RR.c.constraint_name,
                  RR.c.match_option,
                  RR.c.update_rule,
                  RR.c.delete_rule,
              ],
              sql.and_(
                  C.c.table_name == tablename,
                  C.c.table_schema == owner,
                  RR.c.constraint_schema == C.c.table_schema,
                  C.c.constraint_name == RR.c.constraint_name,
                  R.c.constraint_name == RR.c.unique_constraint_name,
                  R.c.constraint_schema == RR.c.unique_constraint_schema,
                  C.c.ordinal_position == R.c.ordinal_position,
              ),
              order_by=[RR.c.constraint_name, R.c.ordinal_position],
          )
  
          # group rows by constraint ID, to handle multi-column FKs
          fkeys = []
          fknm, scols, rcols = (None, [], [])
  
          def fkey_rec():
              return {
                  "name": None,
                  "constrained_columns": [],
                  "referred_schema": None,
                  "referred_table": None,
                  "referred_columns": [],
              }
  
          fkeys = util.defaultdict(fkey_rec)
  
          for r in connection.execute(s).fetchall():
              scol, rschema, rtbl, rcol, rfknm, fkmatch, fkuprule, fkdelrule = r
  
              rec = fkeys[rfknm]
              rec["name"] = rfknm
              if not rec["referred_table"]:
                  rec["referred_table"] = rtbl
                  if schema is not None or owner != rschema:
                      if dbname:
                          rschema = dbname + "." + rschema
                      rec["referred_schema"] = rschema
  
              local_cols, remote_cols = (
                  rec["constrained_columns"],
                  rec["referred_columns"],
              )
  
              local_cols.append(scol)
              remote_cols.append(rcol)
  
          return list(fkeys.values())
  