[1.8.x] Fixed #24835 -- Fixed QuerySet.exists() after an annotation with Count()

QuerySet.exists() incorrectly handled query.group_by = True
case (grouping by all select fields), causing GROUP BY
expressions to be wiped along with select fields.

Backport of 801a84ae329a24d9adf01b700429fe8f1285b2b8 from master

1 files changed, 4 insertions, 0 deletions

diff --git a/tests/annotations/tests.py b/tests/annotations/tests.py
index 9e647cd3f9..c08dd84d57 100644
--- a/tests/annotations/tests.py
+++ b/tests/annotations/tests.py
@@ -245,6 +245,10 @@ class NonAggregateAnnotationTestCase(TestCase):
             lambda a: (a['age'], a['age_count'])
         )
 
+    def test_annotate_exists(self):
+        authors = Author.objects.annotate(c=Count('id')).filter(c__gt=1)
+        self.assertFalse(authors.exists())
+
     def test_column_field_ordering(self):
         """
         Test that columns are aligned in the correct order for