Yarko, you also raise a very good point. And this makes me feel nervous, because all my previous web app are vulnerable to this "overwrite" issue. :-/
Besides the "locking" plugin, which is optional and not aware by everyone, do you think we can add some built-in, anti-overwrite protection inside DAL? For example, if the table contains a field named "__version__", then DAL is responsible for automatically perform version check before every update(). The idea is borrowed from PyDbLite (http://pypi.python.org/pypi/PyDbLite/2.3). And perhaps DAL can do more, by raise exception when concurrent modification is detected during crud.update(). Quoted from http://www.pydblite.net/en/PyDbLite.html - "another internal field called __version__ is also managed by the database engine. It is a integer which is set to 0 when the record is created, then incremented by 1 each time the record is updated. This is used to detect concurrency control, for instance in a web application where 2 users select the same record and want to update it at the same time" Regards, Iceberg On Apr2, 10:44pm, Yarko Tymciurak <resultsinsoftw...@gmail.com> wrote: > The first thing I thought of when I read your post was > this:http://web2py.com/plugins/default/locking > > and I wondered how you implemented your solution. > > I could imagine, if two users open a form, and both submit form.id 2, > one will "overwrite" the other's. > > (hope this is helpful) > Regards, > - Yarko > > On Apr 2, 5:00 am, Sven <svenstrin...@gmail.com> wrote: > > > > > Hi, > > > I programmed a psychological experiment in flash and store answers/ > > results in a sqlite database using web2py (behind nginx server + > > fastcgi) and pyamf. Everything seems to be all right when I test it, > > but with as few as 2 simultaneous users I (sometimes) run into > > trouble. A try with seven simultaneous users resulted in only 2 > > succesfully stored experimental data.sets > > I find it very hard to debug, since there are no tickets in web2py. > > Flash does sometimes produce a remoting error in that situation, but > > without too much information. > > > I seems to me there is some kind of concurrency problem, but I assumed > > web2py/sqlite would take care of that for me. Or should I explicitly > > deal with this? Explicitly commit, check if inserts and updates were > > successful and if not try again? > > > Any suggestions, comments ideas would be really appreciated. > > > Thanks. > > > Sven -- You received this message because you are subscribed to the Google Groups "web2py-users" group. To post to this group, send email to web...@googlegroups.com. To unsubscribe from this group, send email to web2py+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/web2py?hl=en.
