Fixed #28988 -- Fixed queries when a GenericRelation is used with multi-table inheritance.

django/contrib/contenttypes/fields.py

@@ -283,6 +283,8 @@ class GenericRelation(ForeignObject):
 
     rel_class = GenericRel
 
+    mti_inherited = False
+
     def __init__(self, to, object_id_field='object_id', content_type_field='content_type',
                  for_concrete_model=True, related_query_name=None, limit_choices_to=None, **kwargs):
         kwargs['rel'] = self.rel_class(
@@ -427,6 +429,12 @@ class GenericRelation(ForeignObject):
         kwargs['private_only'] = True
         super().contribute_to_class(cls, name, **kwargs)
         self.model = cls
+        # Disable the reverse relation for fields inherited by subclasses of a
+        # model in multi-table inheritance. The reverse relation points to the
+        # field of the base model.
+        if self.mti_inherited:
+            self.remote_field.related_name = '+'
+            self.remote_field.related_query_name = None
         setattr(cls, self.name, ReverseGenericManyToOneDescriptor(self.remote_field))
 
         # Add get_RELATED_order() and set_RELATED_order() to the model this

django/db/models/base.py

@@ -278,7 +278,9 @@ class ModelBase(type):
                             )
                         )
                 else:
-                    new_class.add_to_class(field.name, copy.deepcopy(field))
+                    field = copy.deepcopy(field)
+                    field.mti_inherited = True
+                    new_class.add_to_class(field.name, field)
 
         # Copy indexes so that index names are unique when models extend an
         # abstract model.

tests/generic_relations_regress/models.py

@@ -26,7 +26,7 @@ class LinkProxy(Link):
 
 class Place(models.Model):
     name = models.CharField(max_length=100)
-    links = GenericRelation(Link)
+    links = GenericRelation(Link, related_query_name='places')
     link_proxy = GenericRelation(LinkProxy)
 
     def __str__(self):

tests/generic_relations_regress/tests.py

@@ -263,3 +263,13 @@ class GenericRelationTests(TestCase):
         place = Place.objects.create()
         Link.objects.create(content_object=place)
         self.assertEqual(Place.objects.get(link_proxy__object_id=place.id), place)
+
+    def test_generic_reverse_relation_with_mti(self):
+        """
+        Filtering with a reverse generic relation, where the GenericRelation
+        comes from multi-table inheritance.
+        """
+        place = Place.objects.create(name='Test Place')
+        link = Link.objects.create(content_object=place)
+        result = Link.objects.filter(places=place)
+        self.assertCountEqual(result, [link])