ORM executemany returning

Build on #5401 to allow the ORM to take advanage
of executemany INSERT + RETURNING.

Implemented the feature

updated tests

to support INSERT DEFAULT VALUES, needed to come up with
a new syntax for compiler INSERT INTO table (anycol) VALUES (DEFAULT)
which can then be iterated out for executemany.

Added graceful degrade to plain executemany for PostgreSQL <= 8.2

Renamed EXECUTEMANY_DEFAULT to EXECUTEMANY_PLAIN

Fix issue where unicode identifiers or parameter names wouldn't
work with execute_values() under Py2K, because we have to
encode the statement and therefore have to encode the
insert_single_values_expr too.

Correct issue from #5401 to support executemany + return_defaults
for a PK that is explicitly pre-generated, meaning we aren't actually
getting RETURNING but need to return it from compiled_parameters.

Fixes: #5263
Change-Id: Id68e5c158c4f9ebc33b61c06a448907921c2a657

1 files changed, 6 insertions, 0 deletions

diff --git a/lib/sqlalchemy/sql/crud.py b/lib/sqlalchemy/sql/crud.py
index c80d95a2c..85112f850 100644
--- a/lib/sqlalchemy/sql/crud.py
+++ b/lib/sqlalchemy/sql/crud.py
@@ -157,6 +157,12 @@ def _get_crud_params(compiler, stmt, compile_state, **kw):
         values = _extend_values_for_multiparams(
             compiler, stmt, compile_state, values, kw
         )
+    elif not values and compiler.for_executemany:
+        # convert an "INSERT DEFAULT VALUES"
+        # into INSERT (firstcol) VALUES (DEFAULT) which can be turned
+        # into an in-place multi values.  This supports
+        # insert_executemany_returning mode :)
+        values = [(stmt.table.columns[0], "DEFAULT")]
 
     return values