Opened 9 years ago
Closed 9 years ago
#25505 closed Bug (fixed)
Incomplete relation_tree for inherited proxied Models.
| Reported by: | Jelko Arnds | Owned by: | nobody |
|---|---|---|---|
| Component: | Database layer (models, ORM) | Version: | 1.8 |
| Severity: | Normal | Keywords: | models, meta, deletion, relation, inheritance |
| Cc: | Simon Charette | Triage Stage: | Accepted |
| Has patch: | no | Needs documentation: | no |
| Needs tests: | no | Patch needs improvement: | no |
| Easy pickings: | no | UI/UX: | no |
Description
Options._populate_directed_relation_graph produces an incomplete Options._relation_tree for Models that have set Meta.Proxy = True.
Consider this setup:
BaseModel(models.Model) -> ProxyModel(BaseModel) [with Proxy = True] -> ChildModel(ProxyModel)
In this case the OneToOne relation from ProxyModel to ChildModel is not included in the proxymodel's _meta._relation_tree.
This is caused because Options._populate_directed_relation_graph collects the relations by calling model._meta._get_fields(reverse=False, include_parents=False). Therefore the parent, in this case the ProxyModel is not included.
This results in some unwanted situations. If you call delete() on a ProxyModel, the BaseModel gets deleted, but the ChildModel instance stays in the database and becomes orphaned.
Have a look at the attached models.py to replicate the setup. Compare the behavior of delete() for instances of ChipShop and IndianRestaurant, to see the problem.
Attachments (2)
Change History (7)
by , 9 years ago
comment:1 by , 9 years ago
comment:2 by , 9 years ago
| Cc: | added |
|---|---|
| Triage Stage: | Unreviewed → Accepted |
It looks like this is another can of worms.
The patch proposed for #18012 doesn't fix the reported issue which I managed to reproduce with the attached test case.
comment:3 by , 9 years ago
Note that the test case uses exists() instead of get() because the latter won't return any results and hide the issue because of deferred constraint checks in the transaction wrapping the test case.
Hi jelko,
Could have a look at the patch proposed for #18012 and see if that fixes the reported issue. I haven't tried it myself but from the description you provided it looks like the same scenario.