From e1fc07c047f8e46c2cea0120f44011fc458f1e91 Mon Sep 17 00:00:00 2001
From: Ian Foote <ian@feete.org>
Date: Thu, 15 Nov 2018 14:43:58 +0000
Subject: [PATCH] Fixed #17930 -- Allowed ORing (|) with sliced QuerySets.

---
 django/db/models/query.py |  5 ++++-
 tests/queries/tests.py    | 31 +++++++++++++++++++++++++++++++
 2 files changed, 35 insertions(+), 1 deletion(-)

diff --git a/django/db/models/query.py b/django/db/models/query.py
index 1755bea1a8..b40c768f5c 100644
--- a/django/db/models/query.py
+++ b/django/db/models/query.py
@@ -327,8 +327,11 @@ class QuerySet:
             return other
         if isinstance(other, EmptyQuerySet):
             return self
-        combined = self._chain()
+        query = self if self.query.can_filter() else self.model._base_manager.filter(pk__in=self.values('pk'))
+        combined = query._chain()
         combined._merge_known_related_objects(other)
+        if not other.query.can_filter():
+            other = other.model._base_manager.filter(pk__in=other.values('pk'))
         combined.query.combine(other.query, sql.OR)
         return combined
 
diff --git a/tests/queries/tests.py b/tests/queries/tests.py
index 25e3b283ec..a30403a153 100644
--- a/tests/queries/tests.py
+++ b/tests/queries/tests.py
@@ -2140,6 +2140,37 @@ class SubqueryTests(TestCase):
         )
 
 
+@skipUnlessDBFeature('allow_sliced_subqueries_with_in')
+class QuerySetBitwiseOperationTests(TestCase):
+    @classmethod
+    def setUpTestData(cls):
+        school = School.objects.create()
+        cls.room_1 = Classroom.objects.create(school=school, has_blackboard=False, name='Room 1')
+        cls.room_2 = Classroom.objects.create(school=school, has_blackboard=True, name='Room 2')
+        cls.room_3 = Classroom.objects.create(school=school, has_blackboard=True, name='Room 3')
+        cls.room_4 = Classroom.objects.create(school=school, has_blackboard=False, name='Room 4')
+
+    def test_or_with_rhs_slice(self):
+        qs1 = Classroom.objects.filter(has_blackboard=True)
+        qs2 = Classroom.objects.filter(has_blackboard=False)[:1]
+        self.assertCountEqual(qs1 | qs2, [self.room_1, self.room_2, self.room_3])
+
+    def test_or_with_lhs_slice(self):
+        qs1 = Classroom.objects.filter(has_blackboard=True)[:1]
+        qs2 = Classroom.objects.filter(has_blackboard=False)
+        self.assertCountEqual(qs1 | qs2, [self.room_1, self.room_2, self.room_4])
+
+    def test_or_with_both_slice(self):
+        qs1 = Classroom.objects.filter(has_blackboard=False)[:1]
+        qs2 = Classroom.objects.filter(has_blackboard=True)[:1]
+        self.assertCountEqual(qs1 | qs2, [self.room_1, self.room_2])
+
+    def test_or_with_both_slice_and_ordering(self):
+        qs1 = Classroom.objects.filter(has_blackboard=False).order_by('-pk')[:1]
+        qs2 = Classroom.objects.filter(has_blackboard=True).order_by('-name')[:1]
+        self.assertCountEqual(qs1 | qs2, [self.room_3, self.room_4])
+
+
 class CloneTests(TestCase):
 
     def test_evaluated_queryset_as_argument(self):