From ddd53dafb5fa6ba3cd5075c8e7b3214556c73b50 Mon Sep 17 00:00:00 2001
From: Carl Meyer <carl@oddbird.net>
Date: Sat, 17 Mar 2012 01:24:39 +0000
Subject: [PATCH] Fixed #17918 - Handle proxy models correctly when sorting
 deletions for databases without deferred constraints. Thanks Nate Bragg for
 the report.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@17756 bcc190cf-cafb-0310-a4f2-bffc1f526a37
---
 django/db/models/deletion.py                  | 15 +++++++++---
 .../regressiontests/delete_regress/models.py  |  4 +++-
 tests/regressiontests/delete_regress/tests.py | 23 ++++++++++++++++++-
 3 files changed, 37 insertions(+), 5 deletions(-)

diff --git a/django/db/models/deletion.py b/django/db/models/deletion.py
index 7d6594afc0..730847ef21 100644
--- a/django/db/models/deletion.py
+++ b/django/db/models/deletion.py
@@ -76,6 +76,12 @@ class Collector(object):
         self.data = {}
         self.batches = {} # {model: {field: set([instances])}}
         self.field_updates = {} # {model: {(field, value): set([instances])}}
+
+        # Tracks deletion-order dependency for databases without transactions
+        # or ability to defer constraint checks. Only concrete model classes
+        # should be included, as the dependencies exist only between actual
+        # database tables; proxy models are represented here by their concrete
+        # parent.
         self.dependencies = {} # {model: set([models])}
 
     def add(self, objs, source=None, nullable=False, reverse_dependency=False):
@@ -101,7 +107,8 @@ class Collector(object):
         if source is not None and not nullable:
             if reverse_dependency:
                 source, model = model, source
-            self.dependencies.setdefault(source, set()).add(model)
+            self.dependencies.setdefault(
+                source._meta.concrete_model, set()).add(model._meta.concrete_model)
         return new_objs
 
     def add_batch(self, model, field, objs):
@@ -197,15 +204,17 @@ class Collector(object):
 
     def sort(self):
         sorted_models = []
+        concrete_models = set()
         models = self.data.keys()
         while len(sorted_models) < len(models):
             found = False
             for model in models:
                 if model in sorted_models:
                     continue
-                dependencies = self.dependencies.get(model)
-                if not (dependencies and dependencies.difference(sorted_models)):
+                dependencies = self.dependencies.get(model._meta.concrete_model)
+                if not (dependencies and dependencies.difference(concrete_models)):
                     sorted_models.append(model)
+                    concrete_models.add(model._meta.concrete_model)
                     found = True
             if not found:
                 return
diff --git a/tests/regressiontests/delete_regress/models.py b/tests/regressiontests/delete_regress/models.py
index 214452c97b..5db253f713 100644
--- a/tests/regressiontests/delete_regress/models.py
+++ b/tests/regressiontests/delete_regress/models.py
@@ -90,4 +90,6 @@ class FooFile(models.Model):
 class FooPhoto(models.Model):
     my_photo = models.ForeignKey(Photo)
 
-
+class FooFileProxy(FooFile):
+    class Meta:
+        proxy = True
diff --git a/tests/regressiontests/delete_regress/tests.py b/tests/regressiontests/delete_regress/tests.py
index 889fba81be..32feae2ded 100644
--- a/tests/regressiontests/delete_regress/tests.py
+++ b/tests/regressiontests/delete_regress/tests.py
@@ -8,7 +8,7 @@ from django.test import TestCase, TransactionTestCase, skipUnlessDBFeature
 
 from .models import (Book, Award, AwardNote, Person, Child, Toy, PlayedWith,
     PlayedWithNote, Email, Researcher, Food, Eaten, Policy, Version, Location,
-    Item, Image, File, Photo, FooFile, FooImage, FooPhoto)
+    Item, Image, File, Photo, FooFile, FooImage, FooPhoto, FooFileProxy)
 
 
 # Can't run this test under SQLite, because you can't
@@ -237,3 +237,24 @@ class ProxyDeleteTest(TestCase):
         # to it.
         self.assertEqual(len(FooFile.objects.all()), 0)
         self.assertEqual(len(FooImage.objects.all()), 0)
+
+
+    def test_delete_proxy_pair(self):
+        """
+        If a pair of proxy models are linked by an FK from one concrete parent
+        to the other, deleting one proxy model cascade-deletes the other, and
+        the deletion happens in the right order (not triggering an
+        IntegrityError on databases unable to defer integrity checks).
+
+        Refs #17918.
+
+        """
+        # Create an Image (proxy of File) and FooFileProxy (proxy of FooFile,
+        # which has an FK to File)
+        image = Image.objects.create()
+        as_file = File.objects.get(pk=image.pk)
+        FooFileProxy.objects.create(my_file=as_file)
+
+        Image.objects.all().delete()
+
+        self.assertEqual(len(FooFileProxy.objects.all()), 0)