id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
19149	Generic Relation not cascading with Multi table inheritance.	thomaspurchas		"Generic Relations don't cascade on delete if you are using the generic relation of a superclass in a subclass, then deleting the subclass does not result in the normal cascade behaviour.

For example using the following models:

 {{{#!python
class TaggedItem(models.Model):
    tag = models.SlugField()
    content_type = models.ForeignKey(ContentType)
    object_id = models.PositiveIntegerField()
    content_object = generic.GenericForeignKey('content_type', 'object_id')

    def __unicode__(self):
        return self.tag

class Post(models.Model):
    title = models.TextField(blank=True)

    relation = generic.GenericRelation(TaggedItem)

    def __unicode__(self):
        return self.title

class ParentPost(Post):

    description = models.TextField(blank=True)

    def __unicode__(self):
        return self.description  
}}}

If you create a `ParentPost` and a `TaggedItem` related using the GenericForeignKey:

{{{#!python
>>> p = ParentPost()
>>> p.title = ""This is a title""
>>> p.description = ""This is a description""
>>> p.save()

>>> t = TaggedItem(content_object=p, tag=""This is a tag"")
>>> t.save()
>>> TaggedItem.objects.all()
[<TaggedItem: Ypo>, <TaggedItem: This is a tag>]
}}}

and then delete the `ParentPost`, the `TaggedItem` is not also deleted, rather it just points to a `None` object.

{{{#!python
>>> p.delete()
>>> TaggedItem.objects.all()
[<TaggedItem: Ypo>, <TaggedItem: This is a tag>]
>>> print t.content_object
None
}}}

If you repeat the same procedure with the `Post` model you get the expected behaviour where the `TaggedItem` is deleted."	Bug	new	Database layer (models, ORM)	dev	Normal		multitable, inheritance, genericforeignkey	thomaspurchas michael@… michael@… sky.kok@…	Accepted	1	0	0	1	0	0