Refs #32433 -- Reallowed calling QuerySet.delete() after distinct().

While values(*field_excluding_pk).distinct() and
distinct(*field_excluding_pk) can reduce the number of resulting rows
in a way that makes subsequent delete() calls ambiguous standalone
.distinct() calls cannot.

Since delete() already disallows chain usages with values() the only
case that needs to be handled, as originally reported, is when
DISTINCT ON is used via distinct(*fields).

Refs #32682 which had to resort to subqueries to prevent duplicates in
the admin and caused significant performance regressions on MySQL
(refs #34639).

This partly reverts 6307c3f1a123f5975c73b231e8ac4f115fd72c0d.

1 files changed, 2 insertions, 4 deletions

diff --git a/tests/delete_regress/tests.py b/tests/delete_regress/tests.py
index 2540fd2802..71e3bcb405 100644
--- a/tests/delete_regress/tests.py
+++ b/tests/delete_regress/tests.py
@@ -396,10 +396,8 @@ class DeleteTests(TestCase):
 
 
 class DeleteDistinct(SimpleTestCase):
-    def test_disallowed_delete_distinct(self):
-        msg = "Cannot call delete() after .distinct()."
-        with self.assertRaisesMessage(TypeError, msg):
-            Book.objects.distinct().delete()
+    def test_disallowed_delete_distinct_on(self):
+        msg = "Cannot call delete() after .distinct(*fields)."
         with self.assertRaisesMessage(TypeError, msg):
             Book.objects.distinct("id").delete()