Hi Tony, On Fri, 2009-01-09 at 03:29 -0800, Tony wrote: > This is the reference: (not sure if I interpreted it right - sorry, > newb :) > > "If you use a multiple-table UPDATE statement involving InnoDB tables > for which there are foreign key constraints, the MySQL optimizer might > process tables in an order that differs from that of their parent/ > child relationship. In this case, the statement fails and rolls back. > Instead, update a single table and rely on the ON UPDATE capabilities > that InnoDB provides to cause the other tables to be modified > accordingly. See Section 13.5.5.4, “FOREIGN KEY Constraints”."
Django doesn't do any multi-table updates. They're a custom feature in MySQL and it wasn't really worth adding lots of extra code to exploit that feature in the relatively rare cases it could be used. I think you can rule that out as the cause of your problem. I must admit I haven't really looked at this problem report very much, beyond reading it and thinking there wasn't anything that was *obviously* wrong (so it's something that's subtle). Since you've managed to have a problem in the Model.delete() code and are using MySQL, you've hit two of my personal least favourite aspects in the ORM and I've unfortunately prioritised accordingly (I have a number of unpleasant Django things to work on, but some of them are just slightly less unpleasant than this one). To offer some assistance, though: if this was something I was seeing, I'd reach for the debugging print statements to try and see what we were telling the database. It's a little tricky to print out the SQL that is executed for delete statements, since you can't do the normal trick of printing "queryset.query.as_sql()", as delete() works immediately and doesn't return a queryset. However, look in django.db.models.sql.subqueries.DeleteQuery.do_query(). Just before the call to self.execute_sql(), you could print out self.as_sql() to see what we're trying to do for each call. That might provide some clues. You might also want to have a read through bug titles in the "database" component in Trac to see if any of them look similar to yours. I know there are a couple of delete-related ones in there. One day I hope to work up the enthusiasm to really attack Model.delete() with enthusiasm. It appears to be a little fragile in unpredictable ways (no obvious bugs, but people keep tripping over things and whether it's a code error on their part or a Django ORM error, the error messages are lots of not-fun to interpret). Actually, what I'd really like is for somebody else to attack Model.delete() with enthusiasm, but I'm not holding my breath. Regards, Malcolm --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Django users" group. To post to this group, send email to django-users@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 -~----------~----~----~----~------~----~------~--~---
