def test_defer_inheritance_pk_chaining(self):
        s1 = Secondary.objects.create(first="x1", second="y1")
        bc = BigChild.objects.create(name="b1", value="foo", related=s1,
                                     other="bar")
        bc_deferred = BigChild.objects.only('name').get(pk=bc.pk)
        with self.assertNumQueries(0):
            bc_deferred.id
        self.assertEqual(bc_deferred.pk, bc_deferred.id)
When an inherited model is fetched from the DB, its PK is also fetched.
dataset/ETHPy150Open AppScale/appscale/AppServer/lib/django-1.5/tests/modeltests/defer/tests.py/DeferTests.test_defer_inheritance_pk_chaining