#30842: Prefetch_related spends considerable time constructing querysets.
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Reporter: Alex Aktsipetrov | Owner: nobody
Type: | Status: new
Cleanup/optimization |
Component: Database layer | Version: master
(models, ORM) |
Severity: Normal | Resolution:
Keywords: prefetch_related | Triage Stage: Accepted
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 Alex Aktsipetrov):
Replying to [comment:3 Simon Charette]:
> Ideally only proxies to the original queryset would be created to defer
the creation of querysets to only if needed.
I think we can't really defer the creation, since such a proxy would have
to share lots of features with the QuerySet?
Although we probably can create a proxy to defer just filter calls.
But instead I've tried fumbling with QuerySet itself, see the PR. That
seems simpler from implementation perspective and also gives more control
of copying.
> I wonder if performing some form of local memoization per related
manager class to call `manager._apply_rel_filters` only once manager type
and using queryset cloning could speed up things a bit here. Happy to give
it a broad try if that can get you started Alex.
If you think this is a more promising approach, please do.
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Ticket URL: <https://code.djangoproject.com/ticket/30842#comment:6>
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