Deprecate create_engine.implicit_returning

The :paramref:`_sa.create_engine.implicit_returning` parameter is
deprecated on the :func:`_sa.create_engine` function only; the parameter
remains available on the :class:`_schema.Table` object. This parameter was
originally intended to enable the "implicit returning" feature of
SQLAlchemy when it was first developed and was not enabled by default.
Under modern use, there's no reason this parameter should be disabled, and
it has been observed to cause confusion as it degrades performance and
makes it more difficult for the ORM to retrieve recently inserted server
defaults. The parameter remains available on :class:`_schema.Table` to
specifically suit database-level edge cases which make RETURNING
infeasible, the sole example currently being SQL Server's limitation that
INSERT RETURNING may not be used on a table that has INSERT triggers on it.

Also removed from the Oracle dialect some logic that would upgrade
an Oracle 8/8i server version to use implicit returning if the
parameter were explictly passed; these versions of Oracle
still support RETURNING so the feature is now enabled for all
Oracle versions.

Fixes: #6962
Change-Id: Ib338e300cd7c8026c3083043f645084a8211aed8

1 files changed, 5 insertions, 4 deletions

diff --git a/lib/sqlalchemy/engine/create.py b/lib/sqlalchemy/engine/create.py
index 6e5a07098..b10e72601 100644
--- a/lib/sqlalchemy/engine/create.py
+++ b/lib/sqlalchemy/engine/create.py
@@ -34,6 +34,11 @@ from ..sql import compiler
         'expressions, or an "empty set" SELECT, at statement execution'
         "time.",
     ),
+    implicit_returning=(
+        "2.0",
+        "The :paramref:`_sa.create_engine.implicit_returning` parameter "
+        "is deprecated and will be removed in a future release. ",
+    ),
 )
 def create_engine(url, **kwargs):
     """Create a new :class:`_engine.Engine` instance.
@@ -350,8 +355,6 @@ def create_engine(url, **kwargs):
 
             :paramref:`_engine.Connection.execution_options.logging_token`
 
-
-
     :param max_identifier_length: integer; override the max_identifier_length
         determined by the dialect.  if ``None`` or zero, has no effect.  This
         is the database's configured maximum number of characters that may be
@@ -411,13 +414,11 @@ def create_engine(url, **kwargs):
        "sqlalchemy.pool" logger. Defaults to a hexstring of the object's
        id.
 
-
        .. seealso::
 
             :ref:`dbengine_logging` - further detail on how to configure
             logging.
 
-
     :param pool_pre_ping: boolean, if True will enable the connection pool
         "pre-ping" feature that tests connections for liveness upon
         each checkout.