add performance tests and fix performance regression #781

Author: bckohan

docs/changelog.rst

@@ -1,6 +1,11 @@
 Changelog
 =========
 
+v4.3.1 (2026-01-01)
+-------------------
+
+* Fixed `Significant performance regression on polymorphic queryset iteration <https://github.com/jazzband/django-polymorphic/issues/781>`_
+
 v4.3.0 (2025-12-09)
 -------------------
 

pyproject.toml

@@ -4,7 +4,7 @@ build-backend = "hatchling.build"
 
 [project]
 name = "django-polymorphic"
-version = "4.3.0"
+version = "4.3.1"
 description = "Seamless polymorphic inheritance for Django models."
 readme = "README.md"
 license = "BSD-3-Clause"

src/polymorphic/__init__.py

@@ -19,7 +19,7 @@
 Seamless Polymorphic Inheritance for Django Models
 """
 
-VERSION = "4.3.0"
+VERSION = "4.3.1"
 
 __title__ = "Django Polymorphic"
 __version__ = VERSION  # version synonym for backwards compatibility

src/polymorphic/base.py

@@ -73,10 +73,8 @@ def __new__(self, model_name, bases, attrs, **kwargs):
         # for __init__ function of this class (monkeypatching inheritance accessors)
         new_class.polymorphic_super_sub_accessors_replaced = False
 
-        # determine the name of the primary key field and store it into the class variable
-        # polymorphic_primary_key_name (it is needed by query.py)
         if new_class._meta.pk:
-            new_class.polymorphic_primary_key_name = new_class._meta.pk.name
+            new_class.polymorphic_primary_key_name = new_class._meta.pk.attname
 
         return new_class
 

src/polymorphic/tests/test_orm.py

@@ -1529,7 +1529,7 @@ def test_subqueries(self):
     def test_one_to_one_primary_key(self):
         # check pk name resolution
         for mdl in [Account, SpecialAccount1, SpecialAccount1_1, SpecialAccount2]:
-            assert mdl.polymorphic_primary_key_name == mdl._meta.pk.name
+            assert mdl.polymorphic_primary_key_name == mdl._meta.pk.attname
 
         user1 = get_user_model().objects.create(
             username="user1", email="[email protected]", password="password"

src/polymorphic/tests/test_performance.py

@@ -0,0 +1,34 @@
+from django.test import TransactionTestCase
+from polymorphic.tests.models import (
+    Model2A,
+    Model2B,
+    Model2C,
+    Model2D,
+)
+
+
+class PerformanceTests(TransactionTestCase):
+    def test_baseline_number_of_queries(self):
+        """
+        Test that the number of queries for loading polymorphic models is within
+        expected limits.
+        """
+        for idx in range(100):
+            Model2A.objects.create(field1=f"A{idx}")
+            Model2B.objects.create(field1=f"A{idx}", field2=f"B{idx}")
+            Model2C.objects.create(field1=f"A{idx}", field2=f"B{idx}", field3=f"C{idx}")
+            Model2D.objects.create(
+                field1=f"A{idx}", field2=f"B{idx}", field3=f"C{idx}", field4=f"D{idx}"
+            )
+
+        with self.assertNumQueries(4):
+            list(Model2A.objects.all().order_by("pk"))
+
+        with self.assertNumQueries(3):
+            list(Model2B.objects.all().order_by("pk"))
+
+        with self.assertNumQueries(2):
+            list(Model2C.objects.all().order_by("pk"))
+
+        with self.assertNumQueries(1):
+            list(Model2D.objects.all().order_by("pk"))