Ensure existing mat view has data populated when definition isn't changed

If MATERIALIZED_VIEWS_CHECK_SQL_CHANGED is enabled and view definition has not changed,
and view does not have with_data = False, and somehow the view does not have data
populated, perform a refresh to make sure the data is there.

Author: mikicz

README.md

@@ -330,6 +330,9 @@ check the indexes on the table and delete any extra indexes and create any missi
 is done through the index name, so if you use custom names for your indexes, it might happen that it won't get updated
 on change of the content but not the name.
 
+With data is also respected: if the view definition did not change, but data is not populated and the view class says data should be populated,
+a refresh will happen to ensure the view is populated.
+
 #### Refreshing dependencies / dependants
 
 The `refresh` method on `MaterializedView` only refreshes the given view, not dependencies or dependants.

django_pgviews/management/operations/create_materialized.py

@@ -170,6 +170,18 @@ def create_materialized_view(
 
             if definitions[0] == definitions[1]:
                 _ensure_indexes(connection, cursor, view_cls, schema_name_log)
+
+                if view_cls.with_data:
+                    definitions_where, definitions_params = _make_where(schemaname=vschema, matviewname=[vname])
+                    cursor.execute(
+                        f"SELECT ispopulated FROM pg_catalog.pg_matviews WHERE {definitions_where}",
+                        definitions_params,
+                    )
+                    has_data = cursor.fetchone()[0]
+
+                    if not has_data:
+                        view_cls.refresh(concurrently=False)
+
                 return "EXISTS"
 
         if view_exists:

pyproject.toml

@@ -1,6 +1,6 @@
 [tool.poetry]
 name = "django-pgviews-redux"
-version = "1.0.1"
+version = "1.1.0"
 description = "Create and manage Postgres SQL Views in Django"
 authors = ["Mikuláš Poul <mikulas.poul@xelix.com>"]
 readme = "README.md"

tests/test_project/viewtest/test_views.py

@@ -324,6 +324,31 @@ def test_refresh_pgviews(self):
 
 @pytest.mark.django_db
 class TestMaterializedViewsCheckSQLSettings:
+    def test_migrate_materialized_views_check_sql_set_to_true_no_data(self, settings: SettingsWrapper) -> None:
+        settings.MATERIALIZED_VIEWS_CHECK_SQL_CHANGED = True
+
+        assert models.TestModel.objects.count() == 0
+        assert models.MaterializedRelatedView.objects.count() == 0
+
+        models.TestModel.objects.create(name="Test")
+        call_command("migrate")
+        assert models.MaterializedRelatedView.objects.count() == 0
+
+        # create it with no data
+        with connection.cursor() as cursor:
+            cursor.execute("DROP MATERIALIZED VIEW viewtest_materializedrelatedview CASCADE;")
+            cursor.execute(
+                """
+                CREATE MATERIALIZED VIEW viewtest_materializedrelatedview as
+                SELECT id AS model_id, id FROM viewtest_testmodel
+                WITH NO DATA
+                """
+            )
+
+        # view didn't change but it's not populated, but as it's configured to have data it got refreshed
+        call_command("migrate")
+        assert models.MaterializedRelatedView.objects.count() == 1
+
     def test_migrate_materialized_views_check_sql_set_to_true(self, settings: SettingsWrapper) -> None:
         settings.MATERIALIZED_VIEWS_CHECK_SQL_CHANGED = True