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, 6 insertions, 18 deletions

diff --git a/lib/sqlalchemy/testing/suite/test_insert.py b/lib/sqlalchemy/testing/suite/test_insert.py
index 3c22f50b2..080bb486e 100644
--- a/lib/sqlalchemy/testing/suite/test_insert.py
+++ b/lib/sqlalchemy/testing/suite/test_insert.py
@@ -1,5 +1,3 @@
-from .. import config
-from .. import engines
 from .. import fixtures
 from ..assertions import eq_
 from ..config import requirements
@@ -19,8 +17,6 @@ class LastrowidTest(fixtures.TablesTest):
 
     __requires__ = "implements_get_lastrowid", "autoincrement_insert"
 
-    __engine_options__ = {"implicit_returning": False}
-
     @classmethod
     def define_tables(cls, metadata):
         Table(
@@ -30,6 +26,7 @@ class LastrowidTest(fixtures.TablesTest):
                 "id", Integer, primary_key=True, test_needs_autoincrement=True
             ),
             Column("data", String(50)),
+            implicit_returning=False,
         )
 
         Table(
@@ -37,6 +34,7 @@ class LastrowidTest(fixtures.TablesTest):
             metadata,
             Column("id", Integer, primary_key=True, autoincrement=False),
             Column("data", String(50)),
+            implicit_returning=False,
         )
 
     def _assert_round_trip(self, table, conn):
@@ -110,18 +108,10 @@ class InsertBehaviorTest(fixtures.TablesTest):
         )
 
     @requirements.autoincrement_insert
-    def test_autoclose_on_insert(self):
-        if requirements.returning.enabled:
-            engine = engines.testing_engine(
-                options={"implicit_returning": False}
-            )
-        else:
-            engine = config.db
-
-        with engine.begin() as conn:
-            r = conn.execute(
-                self.tables.autoinc_pk.insert(), dict(data="some data")
-            )
+    def test_autoclose_on_insert(self, connection):
+        r = connection.execute(
+            self.tables.autoinc_pk.insert(), dict(data="some data")
+        )
         assert r._soft_closed
         assert not r.closed
         assert r.is_insert
@@ -306,8 +296,6 @@ class ReturningTest(fixtures.TablesTest):
     __requires__ = "returning", "autoincrement_insert"
     __backend__ = True
 
-    __engine_options__ = {"implicit_returning": True}
-
     def _assert_round_trip(self, table, conn):
         row = conn.execute(table.select()).first()
         eq_(