From 8035cee92293f3319919c8248c7787ba43c05917 Mon Sep 17 00:00:00 2001
From: Simon Charette <charette.s@gmail.com>
Date: Sun, 13 Dec 2015 23:46:41 -0500
Subject: [PATCH] Fixed #25882 -- Prevented fast deletes matching no rows from
 crashing on MySQL.

Thanks to Trac aliases gerricom for the report, raphaelmerx for the
attempts to reproduce and Sergey Fedoseev and Tim for the review.

Refs #16891
---
 django/db/models/sql/subqueries.py |  2 +-
 docs/releases/1.9.1.txt            |  3 +++
 tests/delete/tests.py              | 12 ++++++++++++
 3 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/django/db/models/sql/subqueries.py b/django/db/models/sql/subqueries.py
index 35c814f903d..266b6a017cc 100644
--- a/django/db/models/sql/subqueries.py
+++ b/django/db/models/sql/subqueries.py
@@ -68,7 +68,7 @@ class DeleteQuery(Query):
                 # We can't do the delete using subquery.
                 values = list(query.values_list('pk', flat=True))
                 if not values:
-                    return
+                    return 0
                 return self.delete_batch(values, using)
             else:
                 innerq.clear_select_clause()
diff --git a/docs/releases/1.9.1.txt b/docs/releases/1.9.1.txt
index bc4a0be8adf..eee5a887377 100644
--- a/docs/releases/1.9.1.txt
+++ b/docs/releases/1.9.1.txt
@@ -34,3 +34,6 @@ Bugfixes
   created by ``startapp`` on Python 2 (:ticket:`25909`). Add this line to your
   own ``apps.py`` files created using Django 1.9 if you want your migrations
   to work on both Python 2 and Python 3.
+
+* Prevented ``QuerySet.delete()`` from crashing on MySQL when querying across
+  relations (:ticket`25882`).
diff --git a/tests/delete/tests.py b/tests/delete/tests.py
index 663a22791b2..1a8941904c2 100644
--- a/tests/delete/tests.py
+++ b/tests/delete/tests.py
@@ -503,3 +503,15 @@ class FastDeleteTests(TestCase):
         # that + fast delete of the related objs.
         self.assertNumQueries(2, a.delete)
         self.assertEqual(User.objects.count(), 0)
+
+    def test_fast_delete_empty_no_update_can_self_select(self):
+        """
+        #25932 - Fast deleting on backends that don't have the
+        `no_update_can_self_select` feature should work even if the specified
+        filter doesn't match any row.
+        """
+        with self.assertNumQueries(1):
+            self.assertEqual(
+                User.objects.filter(avatar__desc='missing').delete(),
+                (0, {'delete.User': 0})
+            )