[Django] #34796: Deleting child table does not delete columns in parent table when using multi-table inheritance

[Django]

#34796: Deleting child table does not delete columns in parent table when using
multi-table inheritance
-------------------------------------+-------------------------------------
Reporter: Stephen | Owner: nobody
Finucane |
Type: Bug | Status: new
Component: Database | Version: 4.2
layer (models, ORM) |
Severity: Normal | Keywords:
Triage Stage: | Has patch: 0
Unreviewed |
Needs documentation: 0 | Needs tests: 0
Patch needs improvement: 0 | Easy pickings: 0
UI/UX: 0 |
-------------------------------------+-------------------------------------
I am aware that we don't use database-level cascades (ticket:21961) but I
expected this to be implemented by Django in Python, given the docs
(https://docs.djangoproject.com/en/4.2/topics/db/models/#multi-table-
inheritance) say that the automatically-created `OneToOneField` on the
child model will have `on_delete=models.CASCADE`.

{{{
place_ptr = models.OneToOneField(
Place,
on_delete=models.CASCADE,
parent_link=True,
primary_key=True,
)
}}}

I have produced a reproducer which I will provide a link to shortly. In
summary though, you simply need to create a table using multi-table
inheritance and then delete that table. While the child table will be
deleted, the corresponding rows in the parent table will remain,

--
Ticket URL: <https://code.djangoproject.com/ticket/34796>
Django <https://code.djangoproject.com/>
The Web framework for perfectionists with deadlines.

[Django]

#34796: Deleting child table does not delete columns in parent table when using
multi-table inheritance
-------------------------------------+-------------------------------------

Reporter: Stephen Finucane | Owner: nobody
Type: Bug | Status: new
Component: Database layer | Version: 4.2
(models, ORM) |
Severity: Normal | Resolution:
Keywords: | Triage Stage:
| Unreviewed
Has patch: 0 | Needs documentation: 0

Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------

Description changed by Stephen Finucane:

Old description:

> I am aware that we don't use database-level cascades (ticket:21961) but I
> expected this to be implemented by Django in Python, given the docs
> (https://docs.djangoproject.com/en/4.2/topics/db/models/#multi-table-
> inheritance) say that the automatically-created `OneToOneField` on the
> child model will have `on_delete=models.CASCADE`.
>
> {{{
> place_ptr = models.OneToOneField(
> Place,
> on_delete=models.CASCADE,
> parent_link=True,
> primary_key=True,
> )
> }}}
>
> I have produced a reproducer which I will provide a link to shortly. In
> summary though, you simply need to create a table using multi-table
> inheritance and then delete that table. While the child table will be
> deleted, the corresponding rows in the parent table will remain,

New description:

I am aware that we don't use database-level cascades (ticket:21961) but I
expected this to be implemented by Django in Python, given the docs
(https://docs.djangoproject.com/en/4.2/topics/db/models/#multi-table-
inheritance) say that the automatically-created `OneToOneField` on the
child model will have `on_delete=models.CASCADE`.

{{{
place_ptr = models.OneToOneField(
Place,
on_delete=models.CASCADE,
parent_link=True,
primary_key=True,
)
}}}

I have a minimal reproducer which can be found at
https://github.com/stephenfin/django-bug-34796. In summary though, you

simply need to create a table using multi-table inheritance and then
delete that table. While the child table will be deleted, the

corresponding rows in the parent table will remain.

--

--
Ticket URL: <https://code.djangoproject.com/ticket/34796#comment:1>