Improved support for accessing models when using multiple databases

Co-authored-by: ekaplan1 <[email protected]>
Co-authored-by: bckohan <[email protected]>
Co-authored-by: Copilot <[email protected]>

Author: 3 people

docs/changelog.rst

@@ -4,6 +4,7 @@ Changelog
 v4.3.0 (202X-XX-XX)
 -------------------
 
+* Fixed `Improved support for accessing models when using multiple databases <https://github.com/jazzband/django-polymorphic/pull/550>`_
 * Fixed `Caching in inheritance accessor functions <https://github.com/jazzband/django-polymorphic/pull/510>`_
 * Fixed `Foreign key resolves to parent class when using abstract models <https://github.com/jazzband/django-polymorphic/issues/437>`_
 * Fixed `Support Q expressions that contain subquery expressions <https://github.com/jazzband/django-polymorphic/pull/572>`_

src/polymorphic/models.py

@@ -207,7 +207,7 @@ def accessor_function(self):
                     rel_obj = field.get_cached_value(self)
                 except KeyError:
                     objects = getattr(model, "_base_objects", model.objects)
-                    rel_obj = objects.get(pk=self.pk)
+                    rel_obj = objects.using(self._state.db or DEFAULT_DB_ALIAS).get(pk=self.pk)
                     field.set_cached_value(self, rel_obj)
                 return rel_obj
 

src/polymorphic/tests/settings.py

@@ -137,3 +137,5 @@
 ALLOWED_HOSTS = ["*"]
 
 ROOT_URLCONF = "polymorphic.tests.urls"
+
+USE_TZ = False

src/polymorphic/tests/test_multidb.py

@@ -14,9 +14,17 @@
     ModelY,
     One2OneRelatingModel,
     RelatingModel,
+    RelationA,
+    RelationB,
+    RelationBase,
 )
 
 
+class AllowAllRelations:
+    def allow_relation(self, obj1, obj2, **hints):
+        return True
+
+
 class MultipleDatabasesTests(TestCase):
     databases = ["default", "secondary"]
 
@@ -118,3 +126,13 @@ def func():
 
         # Ensure no queries are made using the default database.
         self.assertNumQueries(0, func)
+
+    def test_deletion_cascade_on_non_default_db(self):
+        base_db1 = RelationA.objects.db_manager("secondary").create(field_a="Base DB1")
+        base_db2 = RelationB.objects.db_manager("secondary").create(
+            field_b="Base DB2", fk=base_db1
+        )
+
+        RelationBase.objects.db_manager("secondary").filter(pk=base_db2.pk).delete()
+
+        self.assertEqual(RelationB.objects.db_manager("secondary").count(), 0)