On Feb 2, 2009, at 10:05 PM, Malcolm Tredinnick wrote: >> I always make my auto-inc fields primary as well, so no argument >> there. >> I tried using the AutoField when I noticed django didn't create the >> auto-incrementing fields correctly by itself in sqlite, but that >> didn't work either until I patched it. > > Then something else is going on and maybe SQLite doesn't need the > AUTOINCREMENT marker for some reason. Because automatic primary key > fields work fine with SQLite. If that ever broke, we'd hear about it > very quickly.
According to sqlite themselves, you can create a primary key without using the AUTOINCREMENT marker, and this key will _almost_ act as an autoinc field, but there is one important difference, and that is that without the use of AUTOINCREMENT, sqlite does not guarantee that a new ID is created for each insert. If you for example deleted the latest row in the table, sqlite would re-use the ID of the deleted row for the next insert. This is because without AUTOINCREMENT, the primary key becomes an alias for sqlite:s internal ROWID, that works this way. From their manual: The behavior implemented by the AUTOINCREMENT keyword is subtly different from the default behavior. With AUTOINCREMENT, rows with automatically selected ROWIDs are guaranteed to have ROWIDs that have never been used before by the same table in the same database. And the automatically generated ROWIDs are guaranteed to be monotonically increasing. These are important properties in certain applications. But if your application does not need these properties, you should probably stay with the default behavior since the use of AUTOINCREMENT requires additional work to be done as each row is inserted and thus causes INSERTs to run a little slower. http://www.sqlite.org/autoinc.html I think django should use the AUTOINCREMENT marker on the AutoField myself, makes sense to me. Still, sqlite does not behave as documented above for me. If I try to use just the ROWID as primary key, I end up not being able to insert any new rows because it will just tell me that the primary key may not be null (when leaving the field out of the insert query, like you would an auto-inc field). This is not djangos fault of course, just an oddity that I really don't understand. Alec --~--~---------~--~----~------------~-------~--~----~ 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 -~----------~----~----~----~------~----~------~--~---
