Ticket #12240: django-select-related-join-chain.diff

django/db/models/sql/compiler.py

@@ -530 +530 @@
             avoid = avoid_set.copy()
             dupe_set = orig_dupe_set.copy()
             table = f.rel.to._meta.db_table
-            if nullable or f.null:
-                promote = True
-            else:
-                promote = False
+            promote = nullable or f.null
             if model:
                 int_opts = opts
                 alias = root_alias
@@ -584 +581 @@
                 next = requested.get(f.name, {})
             else:
                 next = False
-            if f.null is not None:
-                new_nullable = f.null
-            else:
-                new_nullable = None
+            new_nullable = f.null or promote
             for dupe_opts, dupe_col in dupe_set:
                 self.query.update_dupe_avoidance(dupe_opts, dupe_col, alias)
             self.fill_related_selections(f.rel.to._meta, alias, cur_depth + 1,

tests/regressiontests/null_fk/models.py

@@ -4 +4 @@
 
 from django.db import models
 
+class SystemDetails(models.Model):
+    details = models.TextField()
+
 class SystemInfo(models.Model):
+    system_details = models.ForeignKey(SystemDetails)
     system_name = models.CharField(max_length=32)
 
 class Forum(models.Model):
@@ -30 +34 @@
 
 __test__ = {'API_TESTS':"""
 
->>> s = SystemInfo.objects.create(system_name='First forum')
+>>> d = SystemDetails.objects.create(details='First details')
+>>> s = SystemInfo.objects.create(system_name='First forum', system_details=d)
 >>> f = Forum.objects.create(system_info=s, forum_name='First forum')
 >>> p = Post.objects.create(forum=f, title='First Post')
 >>> c1 = Comment.objects.create(post=p, comment_text='My first comment')
@@ -55 +60 @@
 >>> Comment.objects.select_related('post').filter(post__isnull=True)[0].post is None
 True
 
+>>> comments = Comment.objects.select_related('post__forum__system_info__system_details')
+>>> [(c.id, c.comment_text, c.post) for c in comments]
+[(1, u'My first comment', <Post: First Post>), (2, u'My second comment', None)]
+
 """}