#35317: Add the possibility to do prefetches for only a subset of instances
-------------------------------------+-------------------------------------
Reporter: Laurent Lyaudet | Owner: nobody
Type: New feature | Status: closed
Component: Database layer | Version: 5.0
(models, ORM) |
Severity: Normal | Resolution: wontfix
Keywords: | Triage Stage:
| Unreviewed
Has patch: 1 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
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Comment (by Laurent Lyaudet):
TLDR : Use https://pypi.org/project/django-monkey-patches/
Replying to [comment:4 Simon Charette]:
> I'm not convinced we should add a feature for that given
`prefetch_related_objects` is already
[https://docs.djangoproject.com/en/5.0/ref/models/querysets/#django.db.models.prefetch_related_objects
a documented public API] that allows for this feature to be built on top
of
> I'd be a bit more trickier when dealing with predicates for nested
prefetches but it's still doable.
What do you mean by a little bit trickier ?...
I'm using querysets with Django Rest Framework serializers.
I find it convenient to add a static method `enhance_queryset()` in each
model serializer that adds the needed prefetches.
Moreover, when I have nested model serializers,
I call recursively the methods `enhance_queryset()` of the nested model
serializers
in the method `enhance_queryset()` of the main model serializer.
If you use `prefetch_related_objects()` instead, either you do not inject
querysets in your serializers,
or you have to deal with all of this in the __init__() method of your
serializer.
Moreover, you have to gather the relevant objects by hand with nested
loops to put them in `prefetch_related_objects()`...
whilst it is already dealed with with nested prefetches using my patch...
I think my solution is superior, but I will not lose too much time
arguing.
> Just like any other non-trivial feature addition like this one I suggest
trying to gather consensus on a general need for
[https://docs.djangoproject.com/en/5.0/internals/contributing/bugs-and-
features/#requesting-features this feature] on the forum and / or
developer mailing list. From providing support over this channels in the
past years I don't remember anyone else running into a similar issue that
couldn't be solved with `prefetch_related_objects` directly.
Sorry, if I do that it will split the discussion in many places;
and frankly, I already know how are recieved most of the feature requests
on forums/mailing lists/whatever.
Bureaucracy is not for me.
Replying to [comment:5 Mariusz Felisiak]:
> I agree with Simon. The ORM is already packaged with features, so we
generally don't add new options for things that are already possible.
Especially for niche use cases.
>
> You can [https://docs.djangoproject.com/en/stable/internals/contributing
/triaging-tickets/#closing-tickets follow triaging guidelines with regards
to wontfix tickets] and take this to DevelopersMailingList, if you don't
agree.
Idem.
I don't see any way to upvote a feature request here. It would be a nice
way to know what dev using Django wants.
--
Ticket URL: <https://code.djangoproject.com/ticket/35317#comment:6>
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