Inconsistent behaviour in querying and creating objects

[DmitryRisenberg]

I have a strange behaviour for the following models:

from django.db import models

class Channel(models.Model):
    def createSubscription(self):
        subscription = Subscription.objects.create(channel = self)
        print Subscription.objects.filter(channel = self)
        return subscription

class FeedChannel(Channel):
    link = models.CharField(max_length = 200, primary_key = True)

class Subscription(models.Model):
    channel = models.ForeignKey(Channel)

This is what I get when I run ./manage.py shell with a newly created DB:

>>> from smth import models
>>> c = models.FeedChannel.objects.create()
>>> s = c.createSubscription()
[]
>>> print s.channel.id, c.channel_ptr.id
1 1
>>>
>>>

The filter query in createSubscription does not include the created object. I either expect the filter query to select the newly created Subscription object, because its channel field points to the correct Channel instance, or the create query to fail when it encounters an object of derived type instead of base.

Without the primary_key constraint on link field everything works just as expected.

I am using Django 1.1 and Python 2.5.

[Russell Keith-Magee]

By putting the primary_key flag on the link, channel=self is no longer able to roll out as channel=self.pk. Some additional checks will be required internally to make sure the right parent link/value is used.

[Aymeric Augustin]

Change UI/UX from NULL to False.

[Aymeric Augustin]

Change Easy pickings from NULL to False.

[Anssi Kääriäinen]

This seems to be fixed in master. I am somewhat confident that this one has been tested already so I won't add more tests for this).