[Django] #34337: Documentation for custom related managers is contradictory
Django
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Reporter: Adam Alton | Owner: nobody
Type: Bug | Status: new
Component: Documentation | Version: 4.1
Severity: Normal | Keywords:
Triage Stage: Unreviewed | Has patch: 0
Needs documentation: 0 | Needs tests: 0
Patch needs improvement: 0 | Easy pickings: 0
UI/UX: 0 |
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In the [section of the "Managers" documenation about base
managers](https://docs.djangoproject.com/en/4.1/topics/db/managers/#django.db.models.Model._base_manager),
it says:
> By default, Django uses an instance of the Model._base_manager manager
class when accessing related objects
and then two paragraphs further down it says:
> Base managers aren’t used when querying on related models
What? So Django uses a base manager for related objects, but base managers
aren't used for related objects?! I checked with a colleague and they
couldn't make sense of it either.
It's unclear how to specify a custom manager which would be used for
related object lookups. The section above about default managers doesn't
give any clarifcation either.
I seem to remember that there used to be an attribute on the `Manager`
class called `use_for_related_objects`, but looking in the Django source
code I can't see any reference to that anymore.
I would open a pull request to update the docs, but I'm genuinely not sure
what the behaviour is!
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Ticket URL: <https://code.djangoproject.com/ticket/34337>
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Django
Reporter: Adam Alton | Owner: nobody
Component: Documentation | Version: 4.1
Severity: Normal | Resolution: duplicate
Keywords: | Triage Stage: Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
Changes (by Mariusz Felisiak):
* cc: Carlton Gibson (added)
* status: new => closed
* resolution: => duplicate
Comment:
> What? So Django uses a base manager for related objects, but base
managers aren't used for related objects?! I checked with a colleague and
they couldn't make sense of it either.
We have here two different things::
- accessing related fields e.g. `choice.question` where the
`Model._base_manager` manager class is used. This is because Django needs
to be able to retrieve the related object, even if it would otherwise be
filtered out (and hence be inaccessible) by the default manager (as
documented).
- filtering out related fields e.g.
`Choice.objects.filter(question__name__startswith='What')` where base
managers aren’t used.
Personally, I find the documentation quite clear, it contains examples
etc. I'm not sure how we could be clearer 🤔. Closing as a duplicate of
#31342.
Docs improvements are always welcome so feel-free to submit PR with a
concrete proposal and `Refs #31342 -- ...`.
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Ticket URL: <https://code.djangoproject.com/ticket/34337#comment:1>