select_related() does not work with Proxy models and multi-table inheritance

[Ara Anjargolian <ara818@…>]

Consider the following models

class TumbleItem(models.Model):
    tumblr_id = models.CharField(max_length=64, editable=False, null=True)
    pub_date = models.DateTimeField(default=datetime.datetime.now)
    format = models.CharField(max_length=10, choices=FORMAT_CHOICES, default='html')
    display_status = models.CharField(max_length=10, choices=DISPLAY_STATUS_CHOICES, default='public')
    tags = TaggableManager()

    # this is for magic later and makes doing lookups both easier and lazier.
    content_type = models.ForeignKey(ContentType, editable=False, null=True)
    object_id = models.PositiveIntegerField(db_index=True, editable=False, null=True)
    object = generic.GenericForeignKey(ct_field="content_type", fk_field="object_id")


class Regular(TumbleItem):
    title = models.CharField(max_length=250, blank=True)
    body = models.TextField()


class StoryItem(TumbleItem):
    class Meta:
        proxy = True
        
    def _slug(self):
        '''
        strip out extra punctuation and create a slug
        '''
        slug = ''
        if self.object.title != '':
            slug = base.get_base_term(self.object.title)
        return slug
    slug = property(_slug)

To access data stored in Regular efficiently, a select_related would be useful. While a select_related has the expected behavior when using TumbleItem, using the proxy model StoryItem it breaks. I would expect them to have the exact same behavior. See below

>>> print TumbleItem.objects.select_related('regular').query
SELECT `djumblr_tumbleitem`.`id`, `djumblr_tumbleitem`.`tumblr_id`, `djumblr_tumbleitem`.`pub_date`, `djumblr_tumbleitem`.`format`, `djumblr_tumbleitem`.`display_status`, `djumblr_tumbleitem`.`content_type_id`, `djumblr_tumbleitem`.`object_id`, `djumblr_regular`.`tumbleitem_ptr_id`, `djumblr_regular`.`title`, `djumblr_regular`.`body` FROM `djumblr_tumbleitem` LEFT OUTER JOIN `djumblr_regular` ON (`djumblr_tumbleitem`.`id` = `djumblr_regular`.`tumbleitem_ptr_id`) ORDER BY `djumblr_tumbleitem`.`pub_date` DESC

>>> print StoryItem.objects.select_related('regular').query
SELECT `djumblr_tumbleitem`.`id`, `djumblr_tumbleitem`.`tumblr_id`, `djumblr_tumbleitem`.`pub_date`, `djumblr_tumbleitem`.`format`, `djumblr_tumbleitem`.`display_status`, `djumblr_tumbleitem`.`content_type_id`, `djumblr_tumbleitem`.`object_id` FROM `djumblr_tumbleitem` ORDER BY `djumblr_tumbleitem`.`pub_date` DESC

[James Addison]

This would be a nice-to-have addition to existing functionality - marking as 'new feature'.

[Aymeric Augustin]

Change UI/UX from NULL to False.

[Aymeric Augustin]

Change Easy pickings from NULL to False.

[Tim Graham]

Duplicate of #18012. The patch proposed on that ticket fixes this issue.