With these requirements you can't implement it just on database level because it doesn't fit into the standard savepoint/transaction paradigm of databases. Only committed data and finished transactions will be available after OS crash or to other processes. After transaction is committed it cannot be rollbacked - data is saved in database and DBMS cannot do anything with it until application says what exactly it should do. So what you need to do can be implemented only on application level. You can do some sort of logging of your actions and doing opposite actions and cleaning the log when you need it.
Pavel On Sun, Aug 23, 2009 at 6:46 AM, Chris Dew<cms...@googlemail.com> wrote: > Hi, thanks for your questions. > > 1. restarts or OS crashes should leave the data in a sane state - the > last savepoint would be fine. > 2. there's no requirement to revert to old savepoints set during a > previous application run. > 3. no need for more than one process to access the data, though > letting other processes see the data at the last save point would be > nice. > > Note: this is not for production code, just an experiment in keeping a > history of application 'state', allowing current state to be > recalculated if an historic input is received 'late'. See > http://www.finalcog.com/haskell-decoupling-time-from-physics for a > similar idea (implemented in Haskell). > > Regards, > > Chris. > > On Aug 19, 2:36 pm, Pavel Ivanov <paiva...@gmail.com> wrote: >> But how do you expect your application to deal with restarts and/or OS >> crashes? Do you want to still be able to revert to "marks" set in >> previous application run or not? And what about accessing to the data >> stored between "marks" from other processes? >> >> Pavel >> >> >> >> On Wed, Aug 19, 2009 at 4:07 AM, Chris Dew<cms...@googlemail.com> wrote: >> >http://www.sqlite.org/lang_savepoint.html >> > I'm looking for a datastore with the following properties: >> > * I need to 'mark' the state frequently (sub second interval). >> > * I need to be able to revert the datastore to a previous mark (with no >> > appreciable delay). >> > * I only need to keep the last few hundred 'marks'. (i.e. I never need to >> > revert to a datastore marked more than a few minutes ago.) >> >> > The savepoint functionality in sqlite looks to almost fit the bill, but its >> > savepoints seem to be nested - i.e. you cannot 'forget about' old >> > savepoints >> > while retaining recent savepoints. Is my understanding correct here? I'm >> > concerned that this would cause a performance issue when millions of nested >> > savepoints have accumulated. >> >> > Obviously I can roll my own data structure here, but is sqlite was >> > feasible, >> > it would be good. >> >> > Does anyone have any suggestions? >> >> > Thanks, >> >> > Chris. >> >> > -- >> >> >http://www.finalcog.com/ >> > _______________________________________________ >> > sqlite-users mailing list >> > sqlite-us...@sqlite.org >> >http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users >> >> _______________________________________________ >> sqlite-users mailing list >> sqlite-us...@sqlite.orghttp://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users > _______________________________________________ > sqlite-users mailing list > sqlite-users@sqlite.org > http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users > _______________________________________________ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
