:ticket:`3504`
+.. _change_3434:
+
+The legacy_schema_aliasing flag is now set to False
+---------------------------------------------------
+
+SQLAlchemy 1.0.5 introduced the ``legacy_schema_aliasing`` flag to the
+MSSQL dialect, allowing so-called "legacy mode" aliasing to be turned off.
+This aliasing attempts to turn schema-qualified tables into aliases;
+given a table such as::
+
+ account_table = Table(
+ 'account', metadata,
+ Column('id', Integer, primary_key=True),
+ Column('info', String(100)),
+ schema="customer_schema"
+ )
+
+The legacy mode of behavior will attempt to turn a schema-qualified table
+name into an alias::
+
+ >>> 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
+
+However, this aliasing has been shown to be unnecessary and in many cases
+produces incorrect SQL.
+
+In SQLAlchemy 1.1, the ``legacy_schema_aliasing`` flag now defaults to
+False, disabling this mode of behavior and allowing the MSSQL dialect to behave
+normally with schema-qualified tables. For applications which may rely
+on this behavior, set the flag back to True.
+
+
+:ticket:`3434`
+
Dialect Improvements and Changes - Oracle
=============================================
This
is an auxilliary use case suitable for testing and bulk insert scenarios.
-.. _legacy_schema_rendering:
-
-Rendering of SQL statements that include schema qualifiers
----------------------------------------------------------
-
-When using :class:`.Table` metadata that includes a "schema" qualifier,
-such as::
-
- account_table = Table(
- 'account', metadata,
- Column('id', Integer, primary_key=True),
- Column('info', String(100)),
- schema="customer_schema"
- )
-
-The SQL Server dialect has a long-standing behavior that it will attempt
-to turn a schema-qualified table name into an alias, such as::
-
- >>> eng = create_engine("mssql+pymssql://mydsn")
- >>> print(account_table.select().compile(eng))
- SELECT account_1.id, account_1.info
- FROM customer_schema.account AS account_1
-
-This behavior is legacy, does not function correctly for many forms
-of SQL statements, and will be disabled by default in the 1.1 series
-of SQLAlchemy. As of 1.0.5, the above statement will produce the following
-warning::
-
- SAWarning: legacy_schema_aliasing flag is defaulted to True;
- some schema-qualified queries may not function correctly.
- Consider setting this flag to False for modern SQL Server versions;
- this flag will default to False in version 1.1
-
-This warning encourages the :class:`.Engine` to be created as follows::
-
- >>> eng = create_engine("mssql+pymssql://mydsn", legacy_schema_aliasing=False)
-
-Where the above SELECT statement will produce::
-
- >>> print(account_table.select().compile(eng))
- SELECT customer_schema.account.id, customer_schema.account.info
- FROM customer_schema.account
-
-The warning will not emit if the ``legacy_schema_aliasing`` flag is set
-to either True or False.
-
-.. versionadded:: 1.0.5 - Added the ``legacy_schema_aliasing`` flag to disable
- the SQL Server dialect's legacy behavior with schema-qualified table
- names. This flag will default to False in version 1.1.
-
Collation Support
-----------------
.. versionadded:: 1.0.0
+.. _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
def _schema_aliased_table(self, table):
if getattr(table, 'schema', None) is not None:
- if self.dialect._warn_schema_aliasing and \
- table.schema.lower() != 'information_schema':
- util.warn(
- "legacy_schema_aliasing flag is defaulted to True; "
- "some schema-qualified queries may not function "
- "correctly. Consider setting this flag to False for "
- "modern SQL Server versions; this flag will default to "
- "False in version 1.1")
-
if table not in self.tablealiases:
self.tablealiases[table] = table.alias()
return self.tablealiases[table]
max_identifier_length=None,
schema_name="dbo",
deprecate_large_types=None,
- legacy_schema_aliasing=None, **opts):
+ legacy_schema_aliasing=False, **opts):
self.query_timeout = int(query_timeout or 0)
self.schema_name = schema_name
self.max_identifier_length = int(max_identifier_length or 0) or \
self.max_identifier_length
self.deprecate_large_types = deprecate_large_types
-
- if legacy_schema_aliasing is None:
- self.legacy_schema_aliasing = True
- self._warn_schema_aliasing = True
- else:
- self.legacy_schema_aliasing = legacy_schema_aliasing
- self._warn_schema_aliasing = False
+ self.legacy_schema_aliasing = legacy_schema_aliasing
super(MSDialect, self).__init__(**opts)
projects / thirdparty / sqlalchemy / sqlalchemy.git / commitdiff
