Thank you for the detailed response. Russell Keith-Magee wrote: > > But if I AND them (here is the problem/question), nothing... > > ... > > So, is this a bug? Or am I doing something wrong? > > > It's not a bug - it's a slight misunderstanding on your part on how > filtering works.
Yep, I realized that even more after trying this by hand. > The correct way to compose your query would be to do the AND on the query > set, rather than in the filter; > > QueryTerm.objects.filter(classification=4) & QueryTerm.objects.filter > (classification=6) > > This gets two distinct sets of objects, and then determines the elements > that exist in both sets (in this case, just queryterm 1). Unfortunately, the > QuerySet intersection/union operations are the subject of a known bug > (ticket #1801), so while the syntax exists, this might not actually work in > your case. Yep, it doesn't work. Same result. :-( > So, other ways to solve the problem: > 1) Get the two QuerySets and perform the intersection yourself using Python > intersection operators. This requires two SQL operations and doesn't exploit > the capabilities of having your data in a relational database, so the code > will not be as efficient. At this point, I only care that it works. :-) But this is not going to be "clean Django", alas. > 2) Roll your own SQL; what you want can be achieved if you perform 2 joins > with the classification m2m table (rather than the single join that Django > uses) and add the right WHERE clauses. This isn't as pretty, but should be > faster at runtime. Alas, I am not a SQL guru. But I think this will still be easier than trying to shoehorn the current Django implemention into this. > You _might_ be able to acheive option 2 without dropping to raw SQL if you > write a custom Q object to force a second join; however, this approach is > not for beginners. Search the archives of this mailing list for others that > have attempted this approach (there have been a couple in the last 2 months) > and start spelunking through django/db/models/query.py if you feel enthused. Thanks again. I'll do some more digging. Ticket 1801 looks like a good start. --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Django users" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/django-users -~----------~----~----~----~------~----~------~--~---
