[1.8.x] Fixed #24751 -- Fixed HStoreField isnull lookup.

Backport of 3c8fe5dddf34533a419d2deed5208a28de32cb4a from master

3 files changed, 14 insertions, 1 deletions

diff --git a/django/contrib/postgres/fields/hstore.py b/django/contrib/postgres/fields/hstore.py
index 461fa047e2..b8e47edf17 100644
--- a/django/contrib/postgres/fields/hstore.py
+++ b/django/contrib/postgres/fields/hstore.py
@@ -78,7 +78,7 @@ class KeyTransform(Transform):
 
     def as_sql(self, compiler, connection):
         lhs, params = compiler.compile(self.lhs)
-        return "%s -> '%s'" % (lhs, self.key_name), params
+        return "(%s -> '%s')" % (lhs, self.key_name), params
 
 
 class KeyTransformFactory(object):
diff --git a/docs/releases/1.8.2.txt b/docs/releases/1.8.2.txt
index 457dac4034..23483c2a5e 100644
--- a/docs/releases/1.8.2.txt
+++ b/docs/releases/1.8.2.txt
@@ -25,3 +25,5 @@ Bugfixes
   pointing to :class:`~django.db.models.UUIDField` and inheritance on models
   with ``UUIDField`` primary keys work correctly (:ticket:`24698`,
   :ticket:`24712`).
+
+* Fixed ``isnull`` lookup for ``HStoreField`` (:ticket:`24751`).
diff --git a/tests/postgres_tests/test_hstore.py b/tests/postgres_tests/test_hstore.py
index 06544163f8..8b2cc883dc 100644
--- a/tests/postgres_tests/test_hstore.py
+++ b/tests/postgres_tests/test_hstore.py
@@ -110,6 +110,17 @@ class TestQuerying(TestCase):
             self.objs[:3]
         )
 
+    def test_key_isnull(self):
+        obj = HStoreModel.objects.create(field={'a': None})
+        self.assertSequenceEqual(
+            HStoreModel.objects.filter(field__a__isnull=True),
+            self.objs[2:5] + [obj]
+        )
+        self.assertSequenceEqual(
+            HStoreModel.objects.filter(field__a__isnull=False),
+            self.objs[:2]
+        )
+
 
 class TestSerialization(TestCase):
     test_data = '[{"fields": {"field": "{\\"a\\": \\"b\\"}"}, "model": "postgres_tests.hstoremodel", "pk": null}]'