id_list argument to in_bulk() does not account for composite primary keys when batching

[Jacob Walls]

The id_list argument to in_bulk() divides large lists into batches, but similar to #36118, it did not account for composite primary keys, leading to errors like this on SQLite:

django.db.utils.OperationalError: too many SQL variables

#36118 mentioned that other uses like this remained to be audited.

The id_list argument is tested, but the batching was ​not covered.

Failing test (I may adjust this in the PR to run faster by mocking a lower query param limit, but this shows the OperationalError):

tests/composite_pk/tests.py

@@ -147 +147 @@
         result = Comment.objects.in_bulk([self.comment.pk])
         self.assertEqual(result, {self.comment.pk: self.comment})
 
+    def test_in_bulk_batching(self):
+        num_requiring_batching = (connection.features.max_query_params // 2) + 1
+        comments = [
+            Comment(id=i, tenant=self.tenant)
+            for i in range(2, num_requiring_batching + 1)
+        ]
+        Comment.objects.bulk_create(comments)
+        id_list = list(Comment.objects.values_list("pk", flat=True))
+        with self.assertNumQueries(2):
+            comment_dict = Comment.objects.in_bulk(id_list=id_list)
+        self.assertQuerySetEqual(comment_dict, id_list)
+
     def test_iterator(self):
         """
         Test the .iterator() method of composite_pk models.

[Jacob Walls]

​PR