> > > Paul wrote: > > > I can check whether user_version matches magic number without transaction. > > > > No. Executing "PRAGMA user_version" will start an automatic transaction > > if you didn't already start an explicit one. > > > > > Only when user_version does not match magic number I start transaction. > > > > This will never be faster than just starting a transaction explicitly > > and checking the version once. > > > > > The only thing I am worried about is whether > > > > > > pragma user_version=n; > > > > > > respects transactions and will be rolled back automatically in case > > > if something happens between that statement and COMMIT. > > > > Please have a look at this sentence, which you quoted in your mail: > > >> Please note that *all* accesses to the database file are done with > > >> transactions, including reading and writing the user_version value. > > > > I suspect that no, not all accesses to the database file are done using > transactions. > What about read-only databases? Moreover, what about read-only medium? > > I am actually worried not of transaction per se but of its impact on HDD. > My databases must be opened as fast as possilbe. > And in 95% of cases all executed queries are SELECTs. > I don't want sqlite to write anything to disk when, within single database > session, data is only extracted and no modifications to database are made. > > Correct me if I have a wrong model of transaction in mind. > Maybe sqlite does not write a byte to disk if inside a transaction > there are only selects? >
So, the answer to my question is: NO. SQLite does no writes, the begin of a transaction is simply an acquisition of write lock. Thank you all for help! _______________________________________________ sqlite-users mailing list [email protected] http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
