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authorxiubuzhe <xiubuzhe@sina.com>2023-10-08 20:59:00 +0800
committerxiubuzhe <xiubuzhe@sina.com>2023-10-08 20:59:00 +0800
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+# mssql/mxodbc.py
+# Copyright (C) 2005-2022 the SQLAlchemy authors and contributors
+# <see AUTHORS file>
+#
+# This module is part of SQLAlchemy and is released under
+# the MIT License: https://www.opensource.org/licenses/mit-license.php
+
+"""
+.. dialect:: mssql+mxodbc
+ :name: mxODBC
+ :dbapi: mxodbc
+ :connectstring: mssql+mxodbc://<username>:<password>@<dsnname>
+ :url: https://www.egenix.com/
+
+.. deprecated:: 1.4 The mxODBC DBAPI is deprecated and will be removed
+ in a future version. Please use one of the supported DBAPIs to
+ connect to mssql.
+
+Execution Modes
+---------------
+
+mxODBC features two styles of statement execution, using the
+``cursor.execute()`` and ``cursor.executedirect()`` methods (the second being
+an extension to the DBAPI specification). The former makes use of a particular
+API call specific to the SQL Server Native Client ODBC driver known
+SQLDescribeParam, while the latter does not.
+
+mxODBC apparently only makes repeated use of a single prepared statement
+when SQLDescribeParam is used. The advantage to prepared statement reuse is
+one of performance. The disadvantage is that SQLDescribeParam has a limited
+set of scenarios in which bind parameters are understood, including that they
+cannot be placed within the argument lists of function calls, anywhere outside
+the FROM, or even within subqueries within the FROM clause - making the usage
+of bind parameters within SELECT statements impossible for all but the most
+simplistic statements.
+
+For this reason, the mxODBC dialect uses the "native" mode by default only for
+INSERT, UPDATE, and DELETE statements, and uses the escaped string mode for
+all other statements.
+
+This behavior can be controlled via
+:meth:`~sqlalchemy.sql.expression.Executable.execution_options` using the
+``native_odbc_execute`` flag with a value of ``True`` or ``False``, where a
+value of ``True`` will unconditionally use native bind parameters and a value
+of ``False`` will unconditionally use string-escaped parameters.
+
+"""
+
+
+from .base import _MSDate
+from .base import _MSDateTime
+from .base import _MSTime
+from .base import MSDialect
+from .base import VARBINARY
+from .pyodbc import _MSNumeric_pyodbc
+from .pyodbc import MSExecutionContext_pyodbc
+from ... import types as sqltypes
+from ...connectors.mxodbc import MxODBCConnector
+
+
+class _MSNumeric_mxodbc(_MSNumeric_pyodbc):
+ """Include pyodbc's numeric processor."""
+
+
+class _MSDate_mxodbc(_MSDate):
+ def bind_processor(self, dialect):
+ def process(value):
+ if value is not None:
+ return "%s-%s-%s" % (value.year, value.month, value.day)
+ else:
+ return None
+
+ return process
+
+
+class _MSTime_mxodbc(_MSTime):
+ def bind_processor(self, dialect):
+ def process(value):
+ if value is not None:
+ return "%s:%s:%s" % (value.hour, value.minute, value.second)
+ else:
+ return None
+
+ return process
+
+
+class _VARBINARY_mxodbc(VARBINARY):
+
+ """
+ mxODBC Support for VARBINARY column types.
+
+ This handles the special case for null VARBINARY values,
+ which maps None values to the mx.ODBC.Manager.BinaryNull symbol.
+ """
+
+ def bind_processor(self, dialect):
+ if dialect.dbapi is None:
+ return None
+
+ DBAPIBinary = dialect.dbapi.Binary
+
+ def process(value):
+ if value is not None:
+ return DBAPIBinary(value)
+ else:
+ # should pull from mx.ODBC.Manager.BinaryNull
+ return dialect.dbapi.BinaryNull
+
+ return process
+
+
+class MSExecutionContext_mxodbc(MSExecutionContext_pyodbc):
+ """
+ The pyodbc execution context is useful for enabling
+ SELECT SCOPE_IDENTITY in cases where OUTPUT clause
+ does not work (tables with insert triggers).
+ """
+
+ # todo - investigate whether the pyodbc execution context
+ # is really only being used in cases where OUTPUT
+ # won't work.
+
+
+class MSDialect_mxodbc(MxODBCConnector, MSDialect):
+
+ # this is only needed if "native ODBC" mode is used,
+ # which is now disabled by default.
+ # statement_compiler = MSSQLStrictCompiler
+ supports_statement_cache = True
+
+ execution_ctx_cls = MSExecutionContext_mxodbc
+
+ # flag used by _MSNumeric_mxodbc
+ _need_decimal_fix = True
+
+ colspecs = {
+ sqltypes.Numeric: _MSNumeric_mxodbc,
+ sqltypes.DateTime: _MSDateTime,
+ sqltypes.Date: _MSDate_mxodbc,
+ sqltypes.Time: _MSTime_mxodbc,
+ VARBINARY: _VARBINARY_mxodbc,
+ sqltypes.LargeBinary: _VARBINARY_mxodbc,
+ }
+
+ def __init__(self, description_encoding=None, **params):
+ super(MSDialect_mxodbc, self).__init__(**params)
+ self.description_encoding = description_encoding
+
+
+dialect = MSDialect_mxodbc