prefetch_related works invalid!

[Artem Skoretskiy]

I found that getting GenericRelation related objects by prefetch_related gives false result!

Example:

from django.contrib.comments.models import Comment

class Media(models.Model):
    comments = generic.GenericRelation(Comment, object_id_field='object_pk')


>>> Media.objects.filter(pk=1731)[0].comments.all() # works as expected
[<Comment: admin: It is a new comment>]
>>> Media.objects.filter(pk=1731).prefetch_related('comments')[0].comments.all() # nothing found!
[]
>>> 

Thus ORM run proper SQL query:

SELECT *
FROM "django_comments"
WHERE ("django_comments"."object_pk" IN ('1731') AND "django_comments"."content_type_id" = 41 )

I may provide any information if needed. At the point I see no entry point to start digging.

[Claude Paroz]

Maybe the same issue as in #17991? Can you check?

[Artem Skoretskiy]

The fix suggested in #17991 also works for me so it seems to be the same bug.