Add sequence support for MariaDB 10.3+.

Added support for use of the :class:`.Sequence` construct with MariaDB 10.3
and greater, as this is now supported by this database.  The construct
integrates with the :class:`.Table` object in the same way that it does for
other databases like PostrgreSQL and Oracle; if is present on the integer
primary key "autoincrement" column, it is used to generate defaults.   For
backwards compatibility, to support a :class:`.Table` that has a
:class:`.Sequence` on it to support sequence only databases like Oracle,
while still not having the sequence fire off for MariaDB, the optional=True
flag should be set, which indicates the sequence should only be used to
generate the primary key if the target database offers no other option.

Fixes: #4976
Closes: #4996
Pull-request: https://github.com/sqlalchemy/sqlalchemy/pull/4996
Pull-request-sha: cb2e1426ea0b6bc6c93dbe8f033a11df9d8c4915

Change-Id: I507bc405eee6cae2c5991345d0eac53a37fe7512

1 files changed, 12 insertions, 5 deletions

diff --git a/test/engine/test_execute.py b/test/engine/test_execute.py
index 652cea3f3..b71eb8837 100644
--- a/test/engine/test_execute.py
+++ b/test/engine/test_execute.py
@@ -1761,16 +1761,23 @@ class EngineEventsTest(fixtures.TestBase):
             implicit_returning=False,
         )
         self.metadata.create_all(engine)
+
         with engine.begin() as conn:
             event.listen(
                 conn, "before_cursor_execute", tracker("cursor_execute")
             )
             conn.execute(t.insert())
-        # we see the sequence pre-executed in the first call
-        assert "t_id_seq" in canary[0][0]
-        assert "INSERT" in canary[1][0]
-        # same context
-        is_(canary[0][1], canary[1][1])
+
+        if testing.requires.supports_lastrowid.enabled:
+            # new MariaDB 10.3 supports sequences + lastrowid; only
+            # one statement
+            assert "INSERT" in canary[0][0]
+        else:
+            # we see the sequence pre-executed in the first call
+            assert "t_id_seq" in canary[0][0]
+            assert "INSERT" in canary[1][0]
+            # same context
+            is_(canary[0][1], canary[1][1])
 
     def test_transactional(self):
         canary = []