Opened 3 years ago

Closed 17 months ago

#21257 closed New feature (duplicate)

ForeignKey on_delete functionality should traverse (cascade, ha ha) to the DB backend

Reported by: gcbirzan Owned by: nobody
Component: Database layer (models, ORM) Version: master
Severity: Normal Keywords:
Cc: Triage Stage: Accepted
Has patch: no Needs documentation: no
Needs tests: no Patch needs improvement: no
Easy pickings: no UI/UX: no

Description

By default, django creates FKs without an explicit ON DELETE on the backend. This, if nothing else, should be configurable. If for no other reason that when using some transaction isolation modes, the error returned by the backend will be the wrong one during concurrent modifications:

Table b links to table a. You insert in table b a link to ID 1 in a, at the same time as you delete it from a.

With the default (at least in PostgreSQL), in REPEATABLE READ, the error is IntegrityError, which is wrong, since in fact you should just retry the transaction. In lower isolation levels, the FK is deleted (as expected), though, granted the on delete signals are not called.

Change History (5)

comment:1 Changed 3 years ago by Marc Tamlyn

This is likely related to the mailing list conversation https://docs.djangoproject.com/en/dev/ref/django-admin/#runserver-port-or-address-port and the ticket #21127. Basically the consensus seems to be that if we do push to the database it will be a new option to on_delete in the FK declaration. This is also likely to be bundled with the removal of a default behaviour for on_delete.

comment:2 Changed 3 years ago by Marc Tamlyn

Triage Stage: UnreviewedAccepted

comment:3 Changed 3 years ago by anonymous

I think the URL should be https://groups.google.com/forum/#!topic/django-developers/FJMoGgtYIX4

Anyway, it is, but this doesn't involve any default behaviour change, so it should be way easier.

comment:4 Changed 3 years ago by Tim Graham

Component: UncategorizedDatabase layer (models, ORM)

comment:5 Changed 17 months ago by Tim Graham

Resolution: duplicate
Status: newclosed

Duplicate of #21961

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