Add autocommit_block

Added new feature :meth:`.MigrationContext.autocommit_block`, a special
directive which will provide for a non-transactional block inside of a
migration script. The feature requres that: the database driver
(e.g. DBAPI) supports the AUTOCOMMIT isolation mode.  The directive
also necessarily needs to COMMIT the existing transaction in progress
in order to enter autocommit mode.

Change-Id: I107fe9772595db189b6ebeba6535ac8f275b3fe5
Fixes: #123

1 files changed, 18 insertions, 0 deletions

diff --git a/tests/test_postgresql.py b/tests/test_postgresql.py
index 28de487..abc43ea 100644
--- a/tests/test_postgresql.py
+++ b/tests/test_postgresql.py
@@ -269,6 +269,24 @@ class PostgresqlOpTest(TestBase):
         context.assert_("COMMENT ON TABLE foo.t2 IS NULL")
 
 
+class PGAutocommitBlockTest(TestBase):
+    def setUp(self):
+        self.conn = conn = config.db.connect()
+
+        with conn.begin():
+            conn.execute("CREATE TYPE mood AS ENUM ('sad', 'ok', 'happy');")
+
+    def tearDown(self):
+        with self.conn.begin():
+            self.conn.execute("DROP TYPE mood")
+
+    def test_alter_enum(self):
+        context = MigrationContext.configure(connection=self.conn)
+        with context.begin_transaction(_per_migration=True):
+            with context.autocommit_block():
+                context.execute("ALTER TYPE mood ADD VALUE 'soso'")
+
+
 class PGOfflineEnumTest(TestBase):
     def setUp(self):
         staging_env()