#34570: QuerySet.defer() raises an AttributeError when the field is
ManyToManyField or GenericForeignKey
-------------------------------------+-------------------------------------
Reporter: Paco MartÃnez | Owner: Simon
| Charette
Type: Bug | Status: closed
Component: Database layer | Version: 4.2
(models, ORM) |
Severity: Release blocker | Resolution: fixed
Keywords: contenttypes, | Triage Stage: Ready for
defer, manytomanyfield, | checkin
genericforeignkey |
Has patch: 1 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------
Comment (by Paco MartÃnez):
Replying to [comment:2 Simon Charette]:
> > In version 4.1.9 it is working without any error, but in versions
4.2.0 and 4.2.1 raises the AttributeError
>
> Could you elaborate on that? Many-to-many fields and generic foreign
keys are not deferrable (they are virtual and do not map to columns) so
the previous code was simply swallowing invalid values passed to `defer`.
>
> I guess that raising a more detailed exception would still require a
deprecation period and that it would be better to perform this validation
at `defer`/`only` instead of compilation time anyway so our only option
here is to silence cases where `opts.get_field(field_name)` returns
something that doesn't have a `.field` property.
Well, the more I read about `defer()` and what it was for, the more I
wondered that we were deferring ''ManyToMany'' and ''GenericForeignKey''
fields. Thanks for confirming that it was useless and that it just
swallowed it without taking any action.
Thank you very much to both of you for your answers and for your quickness
in solving it.
--
Ticket URL: <https://code.djangoproject.com/ticket/34570#comment:7>
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