[Django] #33493: It's counter-intuitive how QuerySet.iterate() works with prefetch_related
Django
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Reporter: abetkin | Owner: nobody
Type: Uncategorized | Status: new
Component: Uncategorized | Version: dev
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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Hi django fellows!
I've stumbled upon this code in the main branch: (see screenshot)
The usecase is iterating through a queryset with prefetch_related lookups
specified.
Do I understand correctly that multiple database queries happen upon
fetching every chunk, and also that multiple database connections are
required?
If so, than I think it would be better just to prohibit the use of
prefetch_related with QuerySet.iterate
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Ticket URL: <https://code.djangoproject.com/ticket/33493>
Django <https://code.djangoproject.com/>
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Django
Reporter: abetkin | Owner: nobody
Type: Uncategorized | Status: new
Component: Uncategorized | Version: dev
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 abetkin):
* Attachment "methods_that.png" added.
Django
Reporter: abetkin | Owner: nobody
Type: Bug | Status: new
Component: Database layer | Version: dev
(models, ORM) |
Severity: Normal | Resolution:
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 abetkin):
* type: Uncategorized => Bug
* component: Uncategorized => Database layer (models, ORM)
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Ticket URL: <https://code.djangoproject.com/ticket/33493#comment:1>
Django
Reporter: abetkin | Owner: nobody
Type: Bug | Status: new
Component: Database layer | Version: dev
(models, ORM) |
Severity: Normal | Resolution:
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
Changes (by abetkin):
* stage: Unreviewed => Accepted
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Ticket URL: <https://code.djangoproject.com/ticket/33493#comment:2>
Django
Reporter: abetkin | Owner: nobody
Type: | Status: closed
Cleanup/optimization |
Component: Database layer | Version: dev
(models, ORM) |
Keywords: | Triage Stage: Accepted
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
Changes (by Mariusz Felisiak):
* status: new => closed
* type: Bug => Cleanup/optimization
* resolution: => wontfix
Comment:
Support for prefetching related objects with `QuerySet.iterator()` was
added in edbf930287cb72e9afab1f7208c24b1146b0c4ec, and yes an extra query
is necessary for each chunk, it's documented. You can check related
discussions in the ticket #29984, on the [https://groups.google.com/g
/django-developers/c/ADgUd6jRvdw/m/_ZnETNlcAAAJ mailing list], and in
[https://github.com/django/django/pull/15334 PR]. I don't see any reason
to remove this feature.
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Ticket URL: <https://code.djangoproject.com/ticket/33493#comment:3>