Opened 5 years ago

Last modified 3 years ago

#31891 new Bug

Inconsistent related field cache invalidation — at Version 2

Reported by: Josh Owned by: nobody
Component: Database layer (models, ORM) Version: 3.1
Severity: Normal Keywords: orm, related, onetoone
Cc: Triage Stage: Accepted
Has patch: no Needs documentation: no
Needs tests: no Patch needs improvement: no
Easy pickings: no UI/UX: no
Pull Requests:How to create a pull request

Description (last modified by Josh)

Repro:

from django.db import models


class AppUser(models.Model):
    pass


class Profile(models.Model):
    user = models.OneToOneField(
        to=AppUser,
        on_delete=models.PROTECT,
    )


a = AppUser.objects.create()
b = AppUser.objects.create()
Profile.objects.create(user=a)

b.profile # Errors, since it has not been created yet

a.profile.user_id = b.id
a.profile.save()

# Works!
Profile.objects.get(user=b)
# <Profile: Profile object (1)>

b.profile # Errors, since it uses the cached value

I can fix it by using a.profile.user = b which does the cache invalidation as expected. Or using b.refresh_from_db(). However I think it makes sense to fix this within the ORM because it's a subtle bug that can cause issues.
This is a contrived example but the real use-case was cloning a model instance. And instead of erroring it just kept returning the cached value

According to the ticket's flags, the next step(s) to move this issue forward are:

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Change History (2)

comment:1 by Josh, 5 years ago

Description: modified (diff)

comment:2 by Josh, 5 years ago

Description: modified (diff)
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