[1.8.x] Fixed #24525 -- Fixed AssertionError in some complex queries.

Thanks Anssi Kääriäinen for providing the solution.

Backport of 2dc9ec5616a942de3a0886a707f93988f56dd594 from master

1 files changed, 2 insertions, 1 deletions

diff --git a/django/db/models/sql/query.py b/django/db/models/sql/query.py
index 7a0fe8f892..40b6cc57a1 100644
--- a/django/db/models/sql/query.py
+++ b/django/db/models/sql/query.py
@@ -539,7 +539,8 @@ class Query(object):
             # distinct joins for the same connection in rhs query, then the
             # combined query must have two joins, too.
             reuse.discard(new_alias)
-            change_map[alias] = new_alias
+            if alias != new_alias:
+                change_map[alias] = new_alias
             if not rhs.alias_refcount[alias]:
                 # The alias was unused in the rhs query. Unref it so that it
                 # will be unused in the new query, too. We have to add and