Is there any "standard" or "best practice" way of handling concurrent editing of data in tg2? I am referring not to "machine-scale" concurrency, which is nicely handled by database transactions, but rather "human-scale" concurrency -- such as in a CRUD application, when two users have a record open at the same time, and each makes changes. This is the classic "lost update" problem:
1. User A loads the record and starts editing it. 2. User B loads the record and starts editing it, before A saves his changes. 3. User A saves his changes. 4. User B saves his changes, overwriting user A's changes. Database transactions don't help you here unless you keep the transaction open during the user's entire session, not just during a request -- which is almost always a bad idea. The typical modern way of dealing with this on the web -- if you deal with it at all -- is opportunistic locking, where before you save changes you check to see if any updates were made since the data was originally presented to the user. This usually means having a timestamp and/or incrementing version column in each database table, which is sent along with the data in a hidden form field (or JSON data structure), and sent back on submit. If at that point the timestamp or version number has changed, you either (a) try to merge the changes, if possible, or (b) inform user B that they were editing a stale copy of the data, and make them start over or give them a way to merge the versions themselves. So my question is -- is any of this pre-built for me in TG2? Does Catwalk or tgext.crud.controller handle this, or if I use the stock Catwalk to edit my databases, am I vulnerable to the lost update problem? Anybody have some recipes for hooking these kinds of checks in at a low level, so I don't have to repeat the version handling code everywhere? --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "TurboGears" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/turbogears?hl=en -~----------~----~----~----~------~----~------~--~---
