[1.11.x] Fixed #28399 -- Fixed QuerySet.count() for union(), difference(), and intersection() queries.

Backport of adab280cefb15659c39558ac26ea392b0a1e456c from master

1 files changed, 21 insertions, 0 deletions

diff --git a/tests/queries/test_qs_combinators.py b/tests/queries/test_qs_combinators.py
index 2374bb2868..ef8c188c05 100644
--- a/tests/queries/test_qs_combinators.py
+++ b/tests/queries/test_qs_combinators.py
@@ -98,6 +98,27 @@ class QuerySetSetOperationTests(TestCase):
         qs2 = Number.objects.filter(num__gte=2, num__lte=3)
         self.assertNumbersEqual(qs1.union(qs2).order_by('-num'), [3, 2, 1, 0])
 
+    def test_count_union(self):
+        qs1 = Number.objects.filter(num__lte=1).values('num')
+        qs2 = Number.objects.filter(num__gte=2, num__lte=3).values('num')
+        self.assertEqual(qs1.union(qs2).count(), 4)
+
+    def test_count_union_empty_result(self):
+        qs = Number.objects.filter(pk__in=[])
+        self.assertEqual(qs.union(qs).count(), 0)
+
+    @skipUnlessDBFeature('supports_select_difference')
+    def test_count_difference(self):
+        qs1 = Number.objects.filter(num__lt=10)
+        qs2 = Number.objects.filter(num__lt=9)
+        self.assertEqual(qs1.difference(qs2).count(), 1)
+
+    @skipUnlessDBFeature('supports_select_intersection')
+    def test_count_intersection(self):
+        qs1 = Number.objects.filter(num__gte=5)
+        qs2 = Number.objects.filter(num__lte=5)
+        self.assertEqual(qs1.intersection(qs2).count(), 1)
+
     @skipUnlessDBFeature('supports_slicing_ordering_in_compound')
     def test_ordering_subqueries(self):
         qs1 = Number.objects.order_by('num')[:2]