#18012: Propagate reverse foreign keys from proxy models to base class
-------------------------------------+-------------------------------------
Reporter: akaariai | Owner: charettes
Type: | Status: assigned
Cleanup/optimization |
Component: Database layer | Version: 1.4
(models, ORM) |
Severity: Normal | Resolution:
Keywords: | Triage Stage: Accepted
Has patch: 1 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
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Comment (by akaariai):
The place where "reverse relations to proxy models are only a Python
thing" breaks is deletion of models. Deletion of a model that points to a
proxy child of a concrete model will delete the concrete model, too.
Another way to think of this is that the foreign key in the database
representation is to the concrete model, hence the concrete model does
have the related model set.
Maybe we could either add a Meta method to get reverse relations from
proxy children, or just document how to do this properly. This way, if you
need to get the proxy children, there is some way to actually do that.
Still, a generic solution to this problem might be something along the
lines:
{{{
fk = models.ForeignKey(ConcreteModel,
reverse_queryset=ProxyModel.objects.all())
}}}
This is a new thing to learn. But reverse_queryset would have other uses,
too. You could for example use a custom queryset with custom methods, add
annotations, order_by and so on to it. If you filter in the
reverse_queryset, then there might be problems, but we could just document
that you shouldn't do that. This would also fix
Manager.use_for_related_fields flag issues (the flag doesn't work at all
consistently).
All this being said I don't feel at all strongly about this issue, and if
nobody else does, then we should default to not change existing behavior.
--
Ticket URL: <https://code.djangoproject.com/ticket/18012#comment:14>
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