[1.8.x] Fixed #24766 -- Added join promotion for Case expressions

Backport of be9d645346a20a6c394bf70d47b1b1d5c81ff530 from master

1 files changed, 6 insertions, 1 deletions

diff --git a/django/db/models/query_utils.py b/django/db/models/query_utils.py
index 10580f77a6..ac9405ec73 100644
--- a/django/db/models/query_utils.py
+++ b/django/db/models/query_utils.py
@@ -85,7 +85,12 @@ class Q(tree.Node):
         return clone
 
     def resolve_expression(self, query=None, allow_joins=True, reuse=None, summarize=False, for_save=False):
-        clause, _ = query._add_q(self, reuse, allow_joins=allow_joins)
+        # We must promote any new joins to left outer joins so that when Q is
+        # used as an expression, rows aren't filtered due to joins.
+        joins_before = query.tables[:]
+        clause, joins = query._add_q(self, reuse, allow_joins=allow_joins)
+        joins_to_promote = [j for j in joins if j not in joins_before]
+        query.promote_joins(joins_to_promote)
         return clause
 
     @classmethod