Fixed #30572 -- Prevented values()/values_list() on combined queryset from mutating the list of columns in querysets.

2 files changed, 4 insertions, 0 deletions

diff --git a/django/db/models/sql/compiler.py b/django/db/models/sql/compiler.py
index a44adfc760..a791908caf 100644
--- a/django/db/models/sql/compiler.py
+++ b/django/db/models/sql/compiler.py
@@ -426,6 +426,7 @@ class SQLCompiler:
                 # must have the same columns list. Set the selects defined on
                 # the query on all combined queries, if not already set.
                 if not compiler.query.values_select and self.query.values_select:
+                    compiler.query = compiler.query.clone()
                     compiler.query.set_values((
                         *self.query.extra_select,
                         *self.query.values_select,
diff --git a/tests/queries/test_qs_combinators.py b/tests/queries/test_qs_combinators.py
index 3902db59e2..227972e8c4 100644
--- a/tests/queries/test_qs_combinators.py
+++ b/tests/queries/test_qs_combinators.py
@@ -123,6 +123,9 @@ class QuerySetSetOperationTests(TestCase):
         self.assertEqual(reserved_name['order'], 2)
         reserved_name = qs1.union(qs1).values_list('name', 'order', 'id').get()
         self.assertEqual(reserved_name[:2], ('a', 2))
+        # List of columns can be changed.
+        reserved_name = qs1.union(qs1).values_list('order').get()
+        self.assertEqual(reserved_name, (2,))
 
     def test_union_with_two_annotated_values_list(self):
         qs1 = Number.objects.filter(num=1).annotate(