#29625: Expose RelatedManager._remove_prefetched_objects as public method
-------------------------------------+-------------------------------------
Reporter: Ming Qin | Owner: nobody
Type: | Status: new
Cleanup/optimization |
Component: Database layer | Version: master
(models, ORM) |
Severity: Normal | Resolution:
Keywords: prefetch_related, | Triage Stage: Accepted
_prefetched_objects_cache |
Has patch: 1 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 1 | UI/UX: 0
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Comment (by Simon Charette):
Replying to [comment:5 Ming Qin]:
> No, it doesn't work. Still hits the cache. Tested on `master`, `2.1rc1`,
and `2.1`.
> I'll be happy to fix `refresh_from_db`, instead of opening this new API.
>
> Does the following behavior sound good?
> 1. If `refresh_from_db()` is called without argument, it **won't** clear
prefetched cache.
> 2. If it's called specifically with an related field, and that field is
many-to-many or many-to-one field, the prefetched cache **will** be
cleared.
>
1. No, it should clear all fields prefetched cache like it does right now
with non-prefetched related manager cache.
2. I haven't investigated but it looks like `ManyToManyField.is_cached`
and `ManyToMany.delete_cached_value` might need to be redefined from
`Field` in order to take `instance._prefetched_objects_cache` into
consideration as well. It'd be interesting to test how prefetched foreign
keys and o2o behave here as well.
--
Ticket URL: <https://code.djangoproject.com/ticket/29625#comment:6>
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