Hello Jose, I wouldn't be surprised if this was caused by a Django bug with prefetches doing weird things when the same model is referenced through different relations[0].
Simon [0] https://code.djangoproject.com/ticket/26318 Le samedi 4 mars 2017 13:36:20 UTC-5, Jose Kilo a écrit : > > Hi all, > > I'm trying to use an annotated queryset inside a Prefetch object. For some > reason I'm not getting the expected result. > This is a simplified version of my models and query. > > > class User(models.Model): > > following = models.ManyToManyField('User', related_name='followers', > through='Follow') > > > class Follow(models.Model): > > following = models.ForeignKey(User, on_delete=models.CASCADE, > related_name='_followed') > followed = models.ForeignKey(User, on_delete=models.CASCADE, > related_name='_following') > > > def test(): > > User.objects.all().delete() > > user_1 = User.objects.create() > user_2 = User.objects.create() > > Follow.objects.create(following=user_1, followed=user_2) > > queryset = ( > User.objects.all() > .prefetch_related( > Prefetch( > 'followers', to_attr='prefetched_annotated_followers', > queryset=(User.objects.all().annotate( > followers_count=Count('followers', distinct=True), > )) > ), > Prefetch( > 'followers', to_attr='prefetched_followers', > queryset=User.objects.all() > ), > ) > ) > > user = queryset.last() > print(list(user.followers.all())) # [<User: User object>] > print(user.prefetched_followers) # [<User: User object>] > print(user.prefetched_annotated_followers) # [] > > return queryset > > > Why the last result is empty ? > > Just in case, I added 'prefetched_followers' to compare both results. If > I remove it, 'prefetched_annotated_followers' still doesn't get anything. > -- You received this message because you are subscribed to the Google Groups "Django users" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at https://groups.google.com/group/django-users. To view this discussion on the web visit https://groups.google.com/d/msgid/django-users/a79f26af-b4ef-4ba7-9c5a-353a900d891a%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
