On 3/12/06, Glenn Tenney <[EMAIL PROTECTED]> wrote: > Although the docs say that _pre_save "is called just before an object > is saved to the database", that's not quite correct. _pre_save is > called long before the db is committed, and BEFORE the AutoField "id" > is set meaning that when _pre_save runs, id is null. > > So this leads me to several questions: > > Why not allow any integer fields to be autoincrementing (oops, that > may be basic sql ... I haven't checked)? > > How else can I get a field to be a class-unique autoincrementing value? > > Why have _pre_save hook in before the autoincrementing fields get > computed? Shouldn't _pre_save happen after the auto fields are set so > that you can write code to USE the computed "id"?
Hey Glenn, The auto-incrementing happens at the database level, after the INSERT statement is done. This happens at the database level on purpose -- Django doesn't do the auto-incrementing for you, because the database does a good enough job. :) For your particular problem, I'd suggest one of these techniques: * Rely on the database-level auto-incrementing and use _post_save() to compute your value. However, be aware that this technique would hit the database twice for every INSERT save(). * Bypass database-level auto-incrementing and handle that on your own, in _pre_save(). You'd have to manually calculate the next available ID in _pre_save(). Then compute your value based on that. * Write a trigger at the database level that automatically calculates the computed field whenever a record changes in the table. This would be entirely out of Django's control, handled purely at the database level. Hope this helps, Adrian -- Adrian Holovaty holovaty.com | djangoproject.com --~--~---------~--~----~------------~-------~--~----~ 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 -~----------~----~----~----~------~----~------~--~---
