Fixed #33414 -- Fixed creating diamond-shaped MTI objects for common ancestor with primary key that has a default.

Co-authored-by: Simon Charette <charette.s@gmail.com>

tests/model_inheritance/tests.py

@@ -9,6 +9,7 @@ from django.test.utils import CaptureQueriesContext, isolate_apps
 from .models import (
     Base,
     Chef,
+    CommonChild,
     CommonInfo,
     CustomSupplier,
     GrandChild,
@@ -149,6 +150,14 @@ class ModelInheritanceTests(TestCase):
         # accidentally found).
         self.assertSequenceEqual(s.titles.all(), [])
 
+    def test_create_diamond_mti_default_pk(self):
+        # 1 INSERT for each base.
+        with self.assertNumQueries(4):
+            common_child = CommonChild.objects.create()
+        # 3 SELECTs for the parents, 1 UPDATE for the child.
+        with self.assertNumQueries(4):
+            common_child.save()
+
     def test_update_parent_filtering(self):
         """
         Updating a field of a model subclass doesn't issue an UPDATE