django - Cannot update a query once a slice has been taken

Question

I am trying to do this:

UserLog.objects.filter(user=user).filter(action='message').filter(timestamp__lt=now)[0:5].update(read=True)

but I am getting this error:

Cannot update a query once a slice has been taken.

(using django 1.2.1)

What am I doing wrong?

Answer 1

The documentation suggests that something like the following might be possible - I'm not sure if doing the limiting in an inner QuerySet bypasses the check around calling update() after slicing:

inner_q = UserLog.objects.filter(user=user,
                                 action='message',
                                 timestamp__lt=now).values('pk')[0:5]
UserLog.objects.filter(pk__in=inner_q).update(read=True)

Failing that, you could use the in field lookup like so:

ids = UserLog.objects.filter(user=user,
                             action='message',
                             timestamp__lt=now).values_list('pk', flat=True)[0:5]
UserLog.objects.filter(pk__in=list(ids)).update(read=True)