maybe need read de docu https://docs.djangoproject.com/en/1.5/ref/models/querysets/#select-related
Cheers On Wed, Apr 10, 2013 at 7:26 AM, bradley griffiths < [email protected]> wrote: > Cross posted from: stack > overflow<http://stackoverflow.com/questions/15923809/django-queryset-in-operator-on-two-querysets-fails-on-first-call> > . > > When using the 'in' operator on two querysets, the first time the call is > made it fails. > > from django.db import models > class Category(models.Model): > name = models.CharField(max_length=100) > slug = models.SlugField(max_length=100, db_index=True, unique=True) > def __unicode__(self): > return self.name > class Director(models.Model): > name = models.CharField(max_length=100) > slug = models.SlugField(max_length=100, db_index=True, unique=True) > def __unicode__(self): > return self.name > class Project(models.Model): > title = models.CharField(max_length=100) > slug = models.SlugField(max_length=100, db_index=True, unique=True) > director = models.ForeignKey(Director, > related_name='projects_via_director') > categories = models.ManyToManyField(Category, > related_name='projects_via_category') > def __unicode__(self): > return self.title > > > category_list = Category.objects.prefetch_related('projects_via_category') > director_list = Director.objects.prefetch_related('projects_via_director') > other_cats = category_list.filter( > projects_via_category__director__slug='steven-spielberg') > print category_list # [<Category: Film>, <Category: Commercial>]print > other_cats # [<Category: Film>]print category_list[0] in other_cats # > Falseprint category_list[0] in other_cats # True > > > If I remove 'prefetch_related' and use 'all' instead then the problem is > gone, however this uses many more DB calls. > > How can I get the correct result first time using prefetch_related? > > -- > 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 http://groups.google.com/group/django-users?hl=en. > For more options, visit https://groups.google.com/groups/opt_out. > > > -- 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 http://groups.google.com/group/django-users?hl=en. For more options, visit https://groups.google.com/groups/opt_out.
