id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
20242	Django queryset 'in' operator fails on first call	anonymous	svisser	"When using the 'in' operator on a queryset, the first time the call is made it fails. If 'prefetch_related' is removed and 'all' is used instead then the problem is gone.

{{{
from django.db import models


class Category(models.Model):
    name = models.CharField(max_length=100)


class Project(models.Model):
    categories = models.ManyToManyField(Category, related_name='projects')    


category_list = Category.objects.prefetch_related('projects')


print category_list # [<Category: Category object>, <Category: Category object>]
print category_list[0] in category_list # False
print category_list[0] in category_list # True
}}}"	Bug	closed	Database layer (models, ORM)	1.5	Normal	fixed		bmispelon@…	Accepted	1	0	0	0	0	0