#15579: Please add support to delete specialization , while preserving base
class
instance (multi-table inheritance)
-------------------------------------+-------------------------------------
Reporter: zimnyx | Owner: nobody
Status: reopened | Milestone:
Component: Database | Version: SVN
layer (models, ORM) | Keywords:
Resolution: | Has patch: 0
Triage Stage: | Needs tests: 0
Unreviewed |
Needs documentation: 0 |
Patch needs improvement: 0 |
-------------------------------------+-------------------------------------
Changes (by zimnyx):
* status: closed => reopened
* resolution: wontfix =>
Comment:
It doesn't seem to work.
Please take a look on this sample code:
{{{
class List(models.Model):
name = models.CharField(max_length=10)
class SpecificList(List):
specific_name = models.CharField(max_length=10)
}}}
Let's create specialization instance
{{{
>>> s = SpecificList(name='bear', specific_name='sasquatch')
>>> s.save()
110315 11:48:35 21 Query INSERT INTO `list_list` (`name`) VALUES
('bear')
21 Query commit
21 Query SELECT ** FROM `list_specificlist` WHERE
`list_specificlist`.`list_ptr_id` = 3 LIMIT 1
21 Query INSERT INTO `list_specificlist`
(`list_ptr_id`, `specific_name`) VALUES (3, 'sasquatch')
21 Query commit
}}}
And now delete (upcast) it as you suggested:
{{{
>>> s.list_ptr = None
Traceback (most recent call last):
File "<console>", line 1, in <module>
File "/srv/django-bugi/nowa/mypro/django/db/models/fields/related.py",
line 327, in __set__
(instance._meta.object_name, self.field.name))
ValueError: Cannot assign None: "SpecificList.list_ptr" does not allow
null values.
}}}
I also tried setting *_ptr_id to None and then delete:
{{{
>>> s.list_ptr_id = None
>>> s.delete()
Traceback (most recent call last):
File "<console>", line 1, in <module>
File "/srv/django-bugi/nowa/mypro/django/db/models/base.py", line 577,
in delete
assert self._get_pk_val() is not None, "%s object can't be deleted
because its %s attribute is set to None." % (self._meta.object_name,
self._meta.pk.attname)
AssertionError: SpecificList object can't be deleted because its
list_ptr_id attribute is set to None.
}}}
This does not work either.
Do I misunderstood you or this feature just doesn't work?
--
Ticket URL: <http://code.djangoproject.com/ticket/15579#comment:2>
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