Fixed #36464 -- Fixed "__in" tuple lookup on backends lacking native support.

When native support for tuple lookups is missing in a DB backend, it can
be emulated with an EXISTS clause. This is controlled by the backend
feature flag "supports_tuple_lookups".

The mishandling of subquery right-hand side in `TupleIn` (added to
support `CompositePrimaryKey` in Refs #373) was likely missed because
the only core backend we test with the feature flag disabled
(Oracle < 23.4) supports it natively.

Thanks to Nandana Raol for the report, and to Sarah Boyce, Jacob Walls,
and Natalia Bidart for reviews.

1 files changed, 16 insertions, 0 deletions

diff --git a/tests/composite_pk/test_filter.py b/tests/composite_pk/test_filter.py
index c00b6660d8..03037d4d82 100644
--- a/tests/composite_pk/test_filter.py
+++ b/tests/composite_pk/test_filter.py
@@ -1,3 +1,6 @@
+from unittest.mock import patch
+
+from django.db import connection
 from django.db.models import (
     Case,
     F,
@@ -246,6 +249,10 @@ class CompositePKFilterTests(TestCase):
             Comment.objects.filter(user=self.user_1).contains(self.comment_1), True
         )
 
+    def test_filter_query_does_not_mutate(self):
+        queryset = User.objects.filter(comments__in=Comment.objects.all())
+        self.assertEqual(str(queryset.query), str(queryset.query))
+
     def test_filter_users_by_comments_in(self):
         c1, c2, c3, c4, c5 = (
             self.comment_1,
@@ -541,3 +548,12 @@ class CompositePKFilterTests(TestCase):
                 ).filter(filtered_tokens=(1, 1)),
                 [self.tenant_1],
             )
+
+
+@skipUnlessDBFeature("supports_tuple_lookups")
+class CompositePKFilterTupleLookupFallbackTests(CompositePKFilterTests):
+    def setUp(self):
+        feature_patch = patch.object(
+            connection.features, "supports_tuple_lookups", False
+        )
+        self.enterContext(feature_patch)