[Django] #34249: Custom RelatedManager documentation should have side tip on prefetch_related

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Jan 10, 2023, 1:03:42 PM1/10/23

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#34249: Custom RelatedManager documentation should have side tip on
prefetch_related
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Reporter: Vaughn | Owner: nobody
Koch |
Type: | Status: new
Cleanup/optimization |
Component: | Version: 4.1
Documentation | Keywords: documentation
Severity: Normal | relatedmanager custom
Triage Stage: | prefetch_related
Unreviewed | Has patch: 0
Needs documentation: 0 | Needs tests: 0
Patch needs improvement: 0 | Easy pickings: 1
UI/UX: 0 |
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This Django documentation shows how to use a custom manager for reverse
relations.

https://docs.djangoproject.com/en/4.1/topics/db/queries/#using-custom-
reverse-manager

In the given example, this works well as-is, but if you prefetch_related
the entries when you're querying Blog, Django will use the
prefetch_related cache and ignore the custom manager.

This behavior may/may not be desired, but the documentation could use a
side tip about this condition, maybe in a 'Good to know' infobox.

Also, separately: one flaw in the documented approach is that you have to
explicitly use the custom manager when making a query - there doesn't seem
to be a way to make the custom manager the default, which can cause issues
if you forget to add it to all your calls.

--
Ticket URL: <https://code.djangoproject.com/ticket/34249>
Django <https://code.djangoproject.com/>
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Django

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Jan 10, 2023, 11:49:46 PM1/10/23

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#34249: Custom RelatedManager documentation should have side tip on
prefetch_related
-------------------------------------+-------------------------------------

Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0

Easy pickings: 0 | UI/UX: 0
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Changes (by Mariusz Felisiak):