implement batched INSERT..VALUES () () for executemany

the feature is enabled for all built in backends
when RETURNING is used,
except for Oracle that doesn't need it,  and on
psycopg2 and mssql+pyodbc it is used for all INSERT statements,
not just those that use RETURNING.

third party dialects would need to opt in to the new feature
by setting use_insertmanyvalues to True.

Also adds dialect-level guards against using returning
with executemany where we dont have an implementation to
suit it.   execute single w/ returning still defers to the
server without us checking.

Fixes: #6047
Fixes: #7907
Change-Id: I3936d3c00003f02e322f2e43fb949d0e6e568304

1 files changed, 3 insertions, 3 deletions

diff --git a/lib/sqlalchemy/sql/schema.py b/lib/sqlalchemy/sql/schema.py
index 3320214a2..565537109 100644
--- a/lib/sqlalchemy/sql/schema.py
+++ b/lib/sqlalchemy/sql/schema.py
@@ -647,8 +647,9 @@ class Table(
             server side defaults, on those backends which support RETURNING.
 
             In modern SQLAlchemy there is generally no reason to alter this
-            setting, except in the case of some backends such as SQL Server
-            when INSERT triggers are used for that table.
+            setting, except for some backend specific cases
+            (see :ref:`mssql_triggers` in the SQL Server dialect documentation
+            for one such example).
 
         :param include_columns: A list of strings indicating a subset of
             columns to be loaded via the ``autoload`` operation; table columns who
@@ -3158,7 +3159,6 @@ class ScalarElementColumnDefault(ColumnDefault):
         )
 
 
-# _SQLExprDefault = Union["ColumnElement[Any]", "TextClause", "SelectBase"]
 _SQLExprDefault = Union["ColumnElement[Any]", "TextClause"]