id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
36373	select_related() doesn't work when targeting composite primary keys	Jacob Walls	Simon Charette	"The [https://docs.djangoproject.com/en/5.2/topics/composite-primary-key/#composite-primary-keys-and-relations suggested workaround] until #35956 implements foreign keys to models with composite primary keys is to use `ForeignObject`, but it causes failures in `select_related()`. (Of note: `prefetch_related()` works fine.)

{{{#!diff
diff --git a/tests/composite_pk/tests.py b/tests/composite_pk/tests.py
index 5dea23c9f2..068030bd18 100644
--- a/tests/composite_pk/tests.py
+++ b/tests/composite_pk/tests.py
@@ -184,6 +184,11 @@ class CompositePKTests(TestCase):
         with self.assertNumQueries(1):
             self.assertEqual(user.email, self.user.email)
 
+    def test_select_related(self):
+        with self.assertNumQueries(1):
+            for comment in Comment.objects.select_related():
+                comment.user
+
     def test_model_forms(self):
         fields = [""tenant"", ""id"", ""user_id"", ""text"", ""integer""]
         self.assertEqual(list(CommentForm.base_fields), fields)
}}}
{{{
======================================================================
ERROR: test_select_related (composite_pk.tests.CompositePKTests.test_select_related)
----------------------------------------------------------------------
Traceback (most recent call last):
  File ""/Users/.../django/tests/composite_pk/tests.py"", line 189, in test_select_related
    for comment in Comment.objects.select_related():
                   ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^
  File ""/Users/.../django/django/db/models/query.py"", line 403, in __iter__
    self._fetch_all()
    ~~~~~~~~~~~~~~~^^
  File ""/Users/.../django/django/db/models/query.py"", line 1966, in _fetch_all
    self._result_cache = list(self._iterable_class(self))
                         ~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File ""/Users/.../django/django/db/models/query.py"", line 107, in __iter__
    related_populators = get_related_populators(klass_info, select, db, fetch_mode)
  File ""/Users/.../django/django/db/models/query.py"", line 2742, in get_related_populators
    rel_cls = RelatedPopulator(rel_klass_info, select, db, fetch_mode)
  File ""/Users/.../django/django/db/models/query.py"", line 2710, in __init__
    self.pk_idx = self.init_list.index(self.model_cls._meta.pk.attname)
                  ~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
ValueError: 'pk' is not in list
}}}"	Bug	closed	Database layer (models, ORM)	5.2	Release blocker	fixed			Ready for checkin	1	0	0	0	0	0