#26780: Prefetch objects don't work with slices
-------------------------------------+-------------------------------------
Reporter: ludwik | Owner: nobody
Type: New feature | Status: new
Component: Database layer | Version: master
(models, ORM) |
Severity: Normal | Resolution:
Keywords: prefetch, slicing | Triage Stage: Accepted
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
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Comment (by asdator):
The only way to limit this Query (and to not load all the records into
memory) would be to is to do a `top-n-per-group` query which I don't think
the `ORM` is capable of.
What I can suggest is: Instead of limiting the `QuerySet`, find a way to
filter it.
For example, get only the `Posts` in the last day, week or a month (based
on the post-frequency).
{{{
Category.objects.prefetch_related(Prefetch(
'post_set',
queryset=Post.objects.filter(
date_published__gte=datetime.date.today()-timedelta(days=7)),
to_attr='example_posts',
))
}}}
This way you won't load all the Posts into Memory.
--
Ticket URL: <https://code.djangoproject.com/ticket/26780#comment:6>
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