[1.6.x] Fixed #21787 -- regression in MTI .exclude() queries

Backpatch of 78a2617703bc1dada409f126db5c3db214913ff4 from master.

1 files changed, 18 insertions, 0 deletions

diff --git a/tests/queries/tests.py b/tests/queries/tests.py
index ec708c6a51..6d59df6b0e 100644
--- a/tests/queries/tests.py
+++ b/tests/queries/tests.py
@@ -3008,3 +3008,21 @@ class Ticket21203Tests(TestCase):
         qs = Ticket21203Child.objects.select_related('parent').defer('parent__created')
         self.assertQuerysetEqual(qs, [c], lambda x: x)
         self.assertIs(qs[0].parent.parent_bool, True)
+
+
+class ForeignKeyToBaseExcludeTests(TestCase):
+    def test_ticket_21787(self):
+        sc1 = SpecialCategory.objects.create(special_name='sc1', name='sc1')
+        sc2 = SpecialCategory.objects.create(special_name='sc2', name='sc2')
+        sc3 = SpecialCategory.objects.create(special_name='sc3', name='sc3')
+        c1 = CategoryItem.objects.create(category=sc1)
+        CategoryItem.objects.create(category=sc2)
+        self.assertQuerysetEqual(
+            SpecialCategory.objects.exclude(
+                categoryitem__id=c1.pk).order_by('name'),
+            [sc2, sc3], lambda x: x
+        )
+        self.assertQuerysetEqual(
+            SpecialCategory.objects.filter(categoryitem__id=c1.pk),
+            [sc1], lambda x: x
+        )