Fixed #29129 -- Skipped UPDATE when adding a model instance with inherited primary key that has a default.

tests/basic/models.py

@@ -46,3 +46,7 @@ class SelfRef(models.Model):
 
 class PrimaryKeyWithDefault(models.Model):
     uuid = models.UUIDField(primary_key=True, default=uuid.uuid4)
+
+
+class ChildPrimaryKeyWithDefault(PrimaryKeyWithDefault):
+    pass

tests/basic/tests.py

@@ -12,8 +12,8 @@ from django.test import (
 from django.utils.translation import gettext_lazy
 
 from .models import (
-    Article, ArticleSelectOnSave, FeaturedArticle, PrimaryKeyWithDefault,
-    SelfRef,
+    Article, ArticleSelectOnSave, ChildPrimaryKeyWithDefault, FeaturedArticle,
+    PrimaryKeyWithDefault, SelfRef,
 )
 
 
@@ -139,6 +139,12 @@ class ModelInstanceCreationTests(TestCase):
         with self.assertNumQueries(1):
             PrimaryKeyWithDefault().save()
 
+    def test_save_parent_primary_with_default(self):
+        # An UPDATE attempt is skipped when an inherited primary key has
+        # default.
+        with self.assertNumQueries(2):
+            ChildPrimaryKeyWithDefault().save()
+
 
 class ModelTest(TestCase):
     def test_objects_attribute_is_only_available_on_the_class_itself(self):