`get_or_create` broken due to inconsistent behaviour between `create` and `filter` on Manager, RelatedManager, QuerySet, etc.

[Tai Lee]

When calling create, the value for a ForeignKey field must be an instance of the appropriate model, e.g. Model.objects.create(relatedfield=obj). To use a primary key as the value instead of a model instance, you must use the database field name as the keyword, e.g. Model.objects.create(relatedfield_id=N).

When calling filter (or get), you cannot use the database field name as the keyword, but you can use either a model instance or a primary key as the value, e.g. Model.objects.filter(relatedfield_id=N does not work, but Model.objects.filter(relatedfield=obj) and Model.objects.filter(relatedfield=N) both work.

This makes it impossible to use primary keys as values for ForeignKey fields with get_or_create, e.g. Model.objects.get_or_create(relatedfield_id=N, defaults={'otherfield': otherfield}) raises a FieldError exception.

[Tai Lee]

failing test case

[Tai Lee]

Patch has failing test case, but not a fix.

[Julian Bez]

Replying to mrmachine:

e.g. Model.objects.filter(relatedfield_id=N does not work, but Model.objects.filter(relatedfield=obj) and Model.objects.filter(relatedfield=N) both work.

How about Model.objects.filter(relatedfield__id=N)? That usually works. But yes, it does not work with get_or_create and creating new objects, because everything with __ gets stripped for the create query.

[Jacob]

Julian's right that Model.objects.get_or_create(related__id=N, defaults={'related': related_instance}) works and is an acceptable-if-ugly workaround.

However, there's no reason not to make the test given in the patch work, so I'm marking this accepted. If someone wants to work on it, the place to look is in the QuerySet implementation.

[aaron]

Patch with slightly altered test, but no documentation

[aaron]

Oops, not actually sure if this needs docs.

[Tai Lee]

Updated tests to apply cleanly against r14733.

[Tai Lee]

Patch looks good to me. Tests updated to apply against r14733, and pass locally on sqlite, postgresql and mysql.

[Andrew Godwin]

(In [15156]) Fixed #9029 -- Allow use of fieldname_id with get_or_create. Thanks to aaron and mrmachine.

[Andrew Godwin]

(In [15157]) [1.2.X] Fixed #9029 -- Allow use of fieldname_id with get_or_create. Thanks to aaron and mrmachine.

Backport of [15156] from trunk

[Jacob]

Milestone 1.3 deleted