- Added a new dialect flag to the MSSQL dialect

``legacy_schema_aliasing`` which when set to False will disable a
very old and obsolete behavior, that of the compiler's
attempt to turn all schema-qualified table names into alias names,
to work around old and no longer locatable issues where SQL
server could not parse a multi-part identifier name in all
circumstances.   The behavior prevented more
sophisticated statements from working correctly, including those which
use hints, as well as CRUD statements that embed correlated SELECT
statements.  Rather than continue to repair the feature to work
with more complex statements, it's better to just disable it
as it should no longer be needed for any modern SQL server
version.  The flag defaults to True for the 1.0.x series, leaving
current behavior unchanged for this version series.  In the 1.1
series, it will default to False.  For the 1.0 series,
when not set to either value explicitly, a warning is emitted
when a schema-qualified table is first used in a statement, which
suggests that the flag be set to False for all modern SQL Server
versions.
fixes #3424
fixes #3430

1 files changed, 11 insertions, 0 deletions

diff --git a/lib/sqlalchemy/testing/provision.py b/lib/sqlalchemy/testing/provision.py
index c8f7fdf30..8469a0658 100644
--- a/lib/sqlalchemy/testing/provision.py
+++ b/lib/sqlalchemy/testing/provision.py
@@ -49,6 +49,7 @@ def configure_follower(follower_ident):
 def setup_config(db_url, db_opts, options, file_config, follower_ident):
     if follower_ident:
         db_url = _follower_url_from_main(db_url, follower_ident)
+    _update_db_opts(db_url, db_opts)
     eng = engines.testing_engine(db_url, db_opts)
     eng.connect().close()
     cfg = config.Config.register(eng, db_opts, options, file_config)
@@ -94,6 +95,11 @@ def _drop_db(cfg, eng, ident):
 
 
 @register.init
+def _update_db_opts(db_url, db_opts):
+    pass
+
+
+@register.init
 def _configure_follower(cfg, ident):
     pass
 
@@ -105,6 +111,11 @@ def _follower_url_from_main(url, ident):
     return url
 
 
+@_update_db_opts.for_db("mssql")
+def _mssql_update_db_opts(db_url, db_opts):
+    db_opts['legacy_schema_aliasing'] = False
+
+
 @_follower_url_from_main.for_db("sqlite")
 def _sqlite_follower_url_from_main(url, ident):
     url = sa_url.make_url(url)