[1.0.X] Fixed #10028 -- Fixed a problem when ordering by related models.

Some results were inadvertently being excluded if we were ordering across a
nullable relation which itself ordering by a non-nullable relation.

Backport of r9916 from trunk.

git-svn-id: http://code.djangoproject.com/svn/django/branches/releases/1.0.X@9917 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/db/models/sql/query.py

@@ -687,8 +687,9 @@ class BaseQuery(object):
             # the model.
             self.ref_alias(alias)
 
-        # Must use left outer joins for nullable fields.
-        self.promote_alias_chain(joins)
+        # Must use left outer joins for nullable fields and their relations.
+        self.promote_alias_chain(joins,
+                self.alias_map[joins[0]][JOIN_TYPE] == self.LOUTER)
 
         # If we get to this point and the field is a relation to another model,
         # append the default ordering for that model.

tests/regressiontests/queries/models.py

@@ -237,6 +237,32 @@ class PointerA(models.Model):
 class PointerB(models.Model):
     connection = models.ForeignKey(SharedConnection)
 
+# Multi-layer ordering
+class SingleObject(models.Model):
+    name = models.CharField(max_length=10)
+
+    class Meta:
+        ordering = ['name']
+
+    def __unicode__(self):
+        return self.name
+
+class RelatedObject(models.Model):
+    single = models.ForeignKey(SingleObject)
+
+    class Meta:
+        ordering = ['single']
+
+class Plaything(models.Model):
+    name = models.CharField(max_length=10)
+    others = models.ForeignKey(RelatedObject, null=True)
+
+    class Meta:
+        ordering = ['others']
+
+    def __unicode__(self):
+        return self.name
+
 
 __test__ = {'API_TESTS':"""
 >>> t1 = Tag.objects.create(name='t1')