On Sat, 2009-03-21 at 00:17 -0700, chefsmart wrote: [...] > After calling save() on the model, we see that "Now it has an ID". > > So Django is doing an SQL select query, something like last_insert_id, > if I'm not wrong?
That's correct. It varies for each database backend as to which SQL we execute, but that's the general idea. PostgreSQL (in one configuration) and Oracle can return the inserted ID directly from the insert query; we handle that, too. > > I have looked at the source code but it's not entirely clear to me how > Django gets the id for the object that has just been saved. The code in question is in django/db/models/sql/subqueries.py. Look at the InsertQuery.execute_sql() method. The path from public API to that method is: (1) Model.save() (django/db/models/base.py) calls (2) Manager._insert() (django/db/models/manager.py), which calls (3) insert_query() (django/db/models/query.py), which calls (4) InsertQuery.execute_sql() (django/db/models/sql/subqueries.py). There's also some interaction with the DatabaseFeatures and DatabaseOperations in the respective django/db/backends/*/base.py files. Does that answer your question? 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 -~----------~----~----~----~------~----~------~--~---
