> The process experiment seems to confirm that very fast independent parallel > queries can be made on the same database, but clearly I would like the same > behaviour using multiple threads (and probably connections) in the same > process. Is this possible with some specific configuration of SQLite?
Do not use shared cache if you want completely independent connections in each thread. Otherwise each call to sqlite3_step() will block other threads trying to call sqlite3_step() on the same database. Without shared cache they will be completely independent and work as if they were executed in different processes (including amount of I/O involved and amount of memory consumed). Pavel On Thu, Mar 4, 2010 at 12:50 PM, Luke Evans <luk...@me.com> wrote: > Hi SQLiters, > > We're currently investigating SQLite in an application that needs to issue a > batch of queries (SELECTs) before doing some work with all the data returned. > > I have been trying to figure out the fastest way to get the results. Given > there are no writes involved, I figured there might be some advantages in > having the queries run on separate threads, with a connection each, but with > a shared cache and the read uncommitted flag set ON. This works fine, but > the cumulative time for all the queries is in the same ballpark as if the > queries were serialised, despite having SQLITE_CONFIG_MULTITHREAD set, > SQLLITE_CONFIG_MEMSTATUS off, with SQLITE_OPEN_SHAREDCACHE and > SQLITE_OPEN_NOMUTEX used on open. > > So, I'm not sure exactly how to configure (build and runtime) SQLite so it > allows database reads to be essentially independent and lock-free. > > As an experiment, I wrote a simple program to do the same kind of query and > ran several of these in parallel as processes (against the same database > file). In this case, I'm seeing very parallel behaviour, and all queries > complete in just over the time it would normally take for a single one. > > The process experiment seems to confirm that very fast independent parallel > queries can be made on the same database, but clearly I would like the same > behaviour using multiple threads (and probably connections) in the same > process. Is this possible with some specific configuration of SQLite? > > Cheers! > > -- Luke > > > _______________________________________________ > 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
