Well, IMO the only 'real' solution is to have application level transactions, but with all the problems that brings, it's worse than 'not easy' :( All other solutions (versioning, row identity check, etc) are hacks that cannot guarantee consistency for all cases, especially once it escalates to multiple tables - and that's deadlock land...
On Oct 15, 5:07 pm, mdipierro <[EMAIL PROTECTED]> wrote: > I am not sure there is an easy catch all solution to this problem. > > On Oct 15, 8:48 am, achipa <[EMAIL PROTECTED]> wrote: > > > Upon further thought, wouldn't it be better to implement his in a > > playback fashion ? I mean, you would handle the first pages like an > > intentionally failed/rolled back transaction. The further the user > > goes in the process, the further you get with the queries (and you > > will notice any changes made by other users as then would influence > > the selects). That way you have no locks, and only the final input of > > the user does a commit, which is consistent, and requires no > > additional columns. Am I right if I say this is basically a special > > case of a multi-page form consistency problem ? > > > On Oct 15, 3:22 pm, mdipierro <[EMAIL PROTECTED]> wrote: > > > > I do not think belongs to web2py but it could be a next T2 feature. > > > > Massimo > > > > On Oct 15, 4:24 am, billf <[EMAIL PROTECTED]> wrote: > > > > > I would like to request the ability to include a column in every table > > > > to be used to avoid overlapping updates, i.e. where a record has been > > > > updated by user B between user A selecting a record and updating/ > > > > deleting it. When this occurs user B's updates are invisibly undone. > > > > > I know that this can be hand-coded but I believe it would be a useful > > > > and relatively minor addition to the core - as an option on > > > > define_table? version=False being the default? > > > > > The column could be either a version_number (simpler) or a > > > > last_action_timestamp (perhaps more useful but more complicated?) and > > > > would be used to prevent a record being updated/deleted if it had been > > > > changed since selected. This could be achieved in SQLFORM.accepts() > > > > by conditionally adding " and self.table.version==version" or similar > > > > to the update and delete statements. The version (or timestamp) would > > > > be handled in much the same way as 'id'. > > > > > I accept that the probability of overlapping updates is small but in a > > > > business situation it is important for web2py to be rigorous as > > > > possible and this approach has negligible overhead. > > > > > Do people think this is desirable, do-able or dumb? > > > > > Bill --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "web2py Web Framework" group. To post to this group, send email to web2py@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/web2py?hl=en -~----------~----~----~----~------~----~------~--~---
