Fix: Create a transaction and a session when migrating a snapshot

Author: izeigerman

sqlmesh/core/snapshot/evaluator.py

@@ -911,39 +911,40 @@ def _migrate_snapshot(
         ):
             return
 
+        deployability_index = DeployabilityIndex.all_deployable()
+        render_kwargs: t.Dict[str, t.Any] = dict(
+            engine_adapter=adapter,
+            snapshots=parent_snapshots_by_name(snapshot, snapshots),
+            runtime_stage=RuntimeStage.CREATING,
+            deployability_index=deployability_index,
+        )
         target_table_name = snapshot.table_name()
-        if adapter.table_exists(target_table_name):
-            evaluation_strategy = _evaluation_strategy(snapshot, adapter)
-            tmp_table_name = snapshot.table_name(is_deployable=False)
-            logger.info(
-                "Migrating table schema from '%s' to '%s'",
-                tmp_table_name,
-                target_table_name,
-            )
-            evaluation_strategy.migrate(
-                target_table_name=target_table_name,
-                source_table_name=tmp_table_name,
-                snapshot=snapshot,
-                snapshots=parent_snapshots_by_name(snapshot, snapshots),
-                allow_destructive_snapshots=allow_destructive_snapshots,
-            )
-        else:
-            logger.info(
-                "Creating table '%s' for the snapshot of the forward-only model %s",
-                target_table_name,
-                snapshot.snapshot_id,
-            )
-            deployability_index = DeployabilityIndex.all_deployable()
-            render_kwargs: t.Dict[str, t.Any] = dict(
-                engine_adapter=adapter,
-                snapshots=parent_snapshots_by_name(snapshot, snapshots),
-                runtime_stage=RuntimeStage.CREATING,
-                deployability_index=deployability_index,
-            )
-            with (
-                adapter.transaction(),
-                adapter.session(snapshot.model.render_session_properties(**render_kwargs)),
-            ):
+
+        with (
+            adapter.transaction(),
+            adapter.session(snapshot.model.render_session_properties(**render_kwargs)),
+        ):
+            if adapter.table_exists(target_table_name):
+                evaluation_strategy = _evaluation_strategy(snapshot, adapter)
+                tmp_table_name = snapshot.table_name(is_deployable=False)
+                logger.info(
+                    "Migrating table schema from '%s' to '%s'",
+                    tmp_table_name,
+                    target_table_name,
+                )
+                evaluation_strategy.migrate(
+                    target_table_name=target_table_name,
+                    source_table_name=tmp_table_name,
+                    snapshot=snapshot,
+                    snapshots=parent_snapshots_by_name(snapshot, snapshots),
+                    allow_destructive_snapshots=allow_destructive_snapshots,
+                )
+            else:
+                logger.info(
+                    "Creating table '%s' for the snapshot of the forward-only model %s",
+                    target_table_name,
+                    snapshot.snapshot_id,
+                )
                 self._execute_create(
                     snapshot=snapshot,
                     table_name=target_table_name,

tests/core/test_snapshot_evaluator.py

@@ -92,13 +92,16 @@ def date_kwargs() -> t.Dict[str, str]:
 
 @pytest.fixture
 def adapter_mock(mocker: MockerFixture):
+    def mock_exit(self, exc_type, exc_value, traceback):
+        pass
+
     transaction_mock = mocker.Mock()
     transaction_mock.__enter__ = mocker.Mock()
-    transaction_mock.__exit__ = mocker.Mock()
+    transaction_mock.__exit__ = mock_exit
 
     session_mock = mocker.Mock()
     session_mock.__enter__ = mocker.Mock()
-    session_mock.__exit__ = mocker.Mock()
+    session_mock.__exit__ = mock_exit
 
     adapter_mock = mocker.Mock()
     adapter_mock.transaction.return_value = transaction_mock
@@ -1160,6 +1163,7 @@ def test_migrate(mocker: MockerFixture, make_snapshot):
     cursor_mock = mocker.Mock()
     connection_mock.cursor.return_value = cursor_mock
     adapter = EngineAdapter(lambda: connection_mock, "")
+    session_spy = mocker.spy(adapter, "session")
 
     current_table = "sqlmesh__test_schema.test_schema__test_model__1"
 
@@ -1201,6 +1205,8 @@ def columns(table_name):
         ]
     )
 
+    session_spy.assert_called_once()
+
 
 def test_migrate_missing_table(mocker: MockerFixture, make_snapshot):
     connection_mock = mocker.NonCallableMock()