Ok. I thought it was more simple. I don't know the ORM in deep and forgot about the extra() method. Thanks for the explanation.
On Mar 23, 5:15 pm, James Bennett <ubernost...@gmail.com> wrote: > On Tue, Mar 23, 2010 at 10:21 AM, Vinicius Mendes | meiocodigo.com > > <vbmen...@gmail.com> wrote: > > integrated to the framework. I think the queryset should keep track of > > it self. It knows what is the filter, so why can't it negate this > > filter? > > Given an already-existing QuerySet which has already had all the > filters applied, there's really no way to do this. The reason is that > there's so much more that can be done to a QuerySet than just calls to > filter(); for example, calls to extra() may have added additional raw > SQL in the SELECT or WHERE clauses, and the ORM doesn't have any way > to work out how to negate arbitrary user-supplied SQL. > > The WHERE clause itself is represented on the Query object by an > instance of django.db.models.sql.where.WhereNode, which is actually a > tree structure with each node representing part of the WHERE clause. > Each node in that tree does know whether it's negated or not (and > hence whether to use a NOT on the constraint each node expresses), but > walking that tree and figuring out which nodes you'd want to negate > would be difficult to say the least, and still wouldn't work on a > QuerySet which had been affected by something like extra(). > > So about the only way to do this is to collect the filter arguments in > advance *without* applying them to the QuerySet, and then use either > exclude() or negated Q objects to ensure you get a "negated" query. > > -- > "Bureaucrat Conrad, you are technically correct -- the best kind of correct." -- You received this message because you are subscribed to the Google Groups "Django users" group. To post to this group, send email to django-us...@googlegroups.com. To unsubscribe from this group, send email to django-users+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/django-users?hl=en.
