[1.5.x] Fixed #20091 -- Oracle null promotion for empty strings

Backpatch of e17fa9e877e84e93b699c2bd13ea48dbbb86e451

1 files changed, 8 insertions, 1 deletions

diff --git a/tests/regressiontests/queries/tests.py b/tests/regressiontests/queries/tests.py
index a2f91e9964..33e5337f58 100644
--- a/tests/regressiontests/queries/tests.py
+++ b/tests/regressiontests/queries/tests.py
@@ -1533,7 +1533,6 @@ class Queries6Tests(TestCase):
 
         # Nested queries are possible (although should be used with care, since
         # they have performance problems on backends like MySQL.
-
         self.assertQuerysetEqual(
             Annotation.objects.filter(notes__in=Note.objects.filter(note="n1")),
             ['<Annotation: a1>']
@@ -2142,3 +2141,11 @@ class NullJoinPromotionOrTest(TestCase):
         # so we can use INNER JOIN for it. However, we can NOT use INNER JOIN
         # for the b->c join, as a->b is nullable.
         self.assertEqual(str(qset.query).count('INNER JOIN'), 1)
+
+class EmptyStringPromotionTests(TestCase):
+    def test_empty_string_promotion(self):
+        qs = RelatedObject.objects.filter(single__name='')
+        if connection.features.interprets_empty_strings_as_nulls:
+            self.assertIn('LEFT OUTER JOIN', str(qs.query))
+        else:
+            self.assertNotIn('LEFT OUTER JOIN', str(qs.query))