Hi, Le Tue, 22 Jan 2008 11:07:45 -0800 (PST), "[EMAIL PROTECTED]" <[EMAIL PROTECTED]> a écrit :
> Example: > Processes P1, P2, model instance m, with m.val > > - P1 grabs the object : m = MyModel.objects.filter(get the m i want) > [0] > - P2 grabs the object : m = MyModel.objects.filter(get the m i want) > [0] > - P1 m.val += 1 > - P2 m.val += 1 > - P1 m.save() > - P2 m.save() > > What happens normally? What happens with the transaction middleware? I guess the save() methods will set directly the new value, instead of sending a "val + 1" UPDATE to the database. So, if m.val == 0 when you load the object in both P1 and P2, it will result in : UPDATE mymodel SET val = 1 WHERE id = ? whereas you want : UPDATE mymodel SET val = val + 1 WHERE id = ? In the latter, the transaction will handle this (well, as Jeff Anderson said, the _database_ will handle this), and your "val" field will be +2. However, I'm pretty sure Django will do the former. It needs to be checked. But, I guess you can add a method (or override the save() method maybe), to send the correct SQL query. - Jonathan --~--~---------~--~----~------------~-------~--~----~ 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 [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/django-users?hl=en -~----------~----~----~----~------~----~------~--~---
