From 7da37699e8d7124f5d0cfaba931772333c24ef83 Mon Sep 17 00:00:00 2001
From: Daniel Hillier <daniel.hillier@gmail.com>
Date: Wed, 14 Dec 2016 01:06:54 +1100
Subject: [PATCH] Fixed #27594 -- Fixed select_related() with reverse
 self-referential OneToOneField.

Fixed definition of `klass_info['from_parent']` so that two models aren't
considered from a parent class if the model classes are the same.
---
 django/db/models/sql/compiler.py        |  2 +-
 tests/select_related_onetoone/models.py |  9 +++++++++
 tests/select_related_onetoone/tests.py  | 12 ++++++++++--
 3 files changed, 20 insertions(+), 3 deletions(-)

diff --git a/django/db/models/sql/compiler.py b/django/db/models/sql/compiler.py
index c7455ecceb..3e61f8a925 100644
--- a/django/db/models/sql/compiler.py
+++ b/django/db/models/sql/compiler.py
@@ -713,7 +713,7 @@ class SQLCompiler(object):
 
                 _, _, _, joins, _ = self.query.setup_joins([related_field_name], opts, root_alias)
                 alias = joins[-1]
-                from_parent = issubclass(model, opts.model)
+                from_parent = issubclass(model, opts.model) and model is not opts.model
                 klass_info = {
                     'model': model,
                     'field': f,
diff --git a/tests/select_related_onetoone/models.py b/tests/select_related_onetoone/models.py
index cb9221ea1c..76c45659af 100644
--- a/tests/select_related_onetoone/models.py
+++ b/tests/select_related_onetoone/models.py
@@ -102,3 +102,12 @@ class Child3(Child2):
 
 class Child4(Child1):
     value4 = models.IntegerField()
+
+
+class LinkedList(models.Model):
+    name = models.CharField(max_length=50)
+    previous_item = models.OneToOneField(
+        'self', models.CASCADE,
+        related_name='next_item',
+        blank=True, null=True,
+    )
diff --git a/tests/select_related_onetoone/tests.py b/tests/select_related_onetoone/tests.py
index 3f45bba19c..a7d646e25d 100644
--- a/tests/select_related_onetoone/tests.py
+++ b/tests/select_related_onetoone/tests.py
@@ -4,8 +4,9 @@ from django.core.exceptions import FieldError
 from django.test import SimpleTestCase, TestCase
 
 from .models import (
-    AdvancedUserStat, Child1, Child2, Child3, Child4, Image, Parent1, Parent2,
-    Product, StatDetails, User, UserProfile, UserStat, UserStatResult,
+    AdvancedUserStat, Child1, Child2, Child3, Child4, Image, LinkedList,
+    Parent1, Parent2, Product, StatDetails, User, UserProfile, UserStat,
+    UserStatResult,
 )
 
 
@@ -207,6 +208,13 @@ class ReverseSelectRelatedTestCase(TestCase):
             self.assertEqual(p.child1.name1, 'n1')
             self.assertEqual(p.child1.child4.name1, 'n1')
 
+    def test_self_relation(self):
+        item1 = LinkedList.objects.create(name='item1')
+        LinkedList.objects.create(name='item2', previous_item=item1)
+        with self.assertNumQueries(1):
+            item1_db = LinkedList.objects.select_related('next_item').get(name='item1')
+            self.assertEqual(item1_db.next_item.name, 'item2')
+
 
 class ReverseSelectRelatedValidationTests(SimpleTestCase):
     """