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, 12 insertions, 0 deletions

diff --git a/lib/sqlalchemy/dialects/sqlite/base.py b/lib/sqlalchemy/dialects/sqlite/base.py
index 88c6dbe18..e57a84fe0 100644
--- a/lib/sqlalchemy/dialects/sqlite/base.py
+++ b/lib/sqlalchemy/dialects/sqlite/base.py
@@ -1936,6 +1936,7 @@ class SQLiteDialect(default.DefaultDialect):
     supports_empty_insert = False
     supports_cast = True
     supports_multivalues_insert = True
+    use_insertmanyvalues = True
     tuple_in_values = True
     supports_statement_cache = True
     insert_null_pk_still_autoincrements = True
@@ -1944,6 +1945,13 @@ class SQLiteDialect(default.DefaultDialect):
     delete_returning = True
     update_returning_multifrom = True
 
+    supports_default_metavalue = True
+    """dialect supports INSERT... VALUES (DEFAULT) syntax"""
+
+    default_metavalue_token = "NULL"
+    """for INSERT... VALUES (DEFAULT) syntax, the token to put in the
+    parenthesis."""
+
     default_paramstyle = "qmark"
     execution_ctx_cls = SQLiteExecutionContext
     statement_compiler = SQLiteCompiler
@@ -2055,6 +2063,10 @@ class SQLiteDialect(default.DefaultDialect):
                     self.delete_returning
                 ) = self.insert_returning = False
 
+            if self.dbapi.sqlite_version_info < (3, 32, 0):
+                # https://www.sqlite.org/limits.html
+                self.insertmanyvalues_max_parameters = 999
+
     _isolation_lookup = util.immutabledict(
         {"READ UNCOMMITTED": 1, "SERIALIZABLE": 0}
     )