Opened 8 years ago

Closed 5 years ago

#19018 closed Bug (fixed)

m2m relationships with a through field don't respect types.

Reported by: Justin Lilly Owned by: nobody
Component: Database layer (models, ORM) Version: 1.4
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


I ran into an issue today in which an empty list was returned from a Queryset when it should have been a blatant failure.

Given the models in

The following returns an empty queryset:


Change History (7)

comment:1 Changed 8 years ago by Justin Lilly

Type: UncategorizedBug

comment:2 Changed 8 years ago by Alex Gaynor

Triage Stage: UnreviewedAccepted

comment:3 Changed 8 years ago by Carl Meyer

I don't believe this bug is specific to m2ms or through models at all. In general, currently you can pass any iterable of instances of any model to any __in query and the ORM will happily use the PKs of the models you give it, without checking whether they are an instance of the right model class (or a subclass, or raw PK values which is also supported).

comment:4 Changed 8 years ago by Carl Meyer

(Also not specific to __in queries, same is true of a simple __exact match on an FK field).

comment:5 Changed 8 years ago by Alex Gaynor

Everything you just said is correct, it's not just your belief :)

comment:6 Changed 8 years ago by Preston Holmes

So looking at this mostly for my own edification.

A higher level place this could be checked would be db.models.where.Constraint.process

otherwise: db.models.fields.related.RelatedField.get_db_prep_lookup and db.models.fields.related.RelatedField._pk_trace

seem like the best places to tackle this.

However unless a patch is pretty quick, it seems worth improving the docs, at least in the interim, to clarify that lookup values for model instances will always be converted to a simple pk value for database lookups.

comment:7 Changed 5 years ago by Marten Kenbeek

Resolution: fixed
Status: newclosed

Fixed as part of 34ba86706f0db33d9a0ab44e4abb78703e7262a9:

Fixed #14334 -- Query relation lookups now check object types.

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