prefetch_related does not cache results when the model is inherited

[idanzalz@…]

given the following models:

class ParentBase(models.Model): pass

class Parent(models.Model): pass

class ParentWithBase(ParentBase): pass

class Child(models.Model):
    parent = models.ForeignKey('Parent')
    parent_with_base = models.ForeignKey('ParentWithBase')

When I try to select a child model and prefetch the parents, the parent with the base performs another query which I am trying to avoid.
So my test code is:

# Create the child and parent objects
Child.objects.create(parent = Parent.objects.create(), parent_with_base = ParentWithBase.objects.create())
# Select the child and prefetch the parents
child = Child.objects.prefetch_related('parent','parent_with_base').all()[0]
with self.assertNumQueries(0):
    child.parent # This works just fine - no queries are emitted
with self.assertNumQueries(0):
    child.parent_with_base # TEST FAILS HERE - since one query is emitted

[Russell Keith-Magee]

I put your test models and test code into a test project, and it failed under 1.4, but passes under 1.5b2. It appears this bug has been fixed since the release of 1.4.

[anonymous]

Good to hear it works in 1.5, but worksforme is not the right resolution, since it is broken on 1.4 as reported.