--- On Tue, 11/24/09, Nicolas Rivera <nicolas.riv...@ac4s.com> wrote:
> From: Nicolas Rivera <nicolas.riv...@ac4s.com> > Subject: [sqlite] multiple threads with shared cache mode > To: sqlite-users@sqlite.org > Date: Tuesday, November 24, 2009, 12:22 PM > Hi, > > It is my understanding, per > http://www.hwaci.com/sw/sqlite/sharedcache.html section > 2.1, that only > one write transaction may exist while in shared cache > mode. Is that > correct? Correct. > > If so, then I am trying to figure out what is the advantage > of having > table level locks in shared cache mode. If only one > write transaction > can be pending at a time, irrespective of the table, then > what advantage > is there to having table level locks? > > To put it another way, is there anything gained in terms of > concurrency > by using shared cached mode versus not using it? BTW, > I am not > interested in reading uncommitted data. Yes only one write transaction may occur at a time. But it is possible that a write be happening on two separate tables by two separate threads. Then once one of the threads needs to spill its "writes" to disk the locks are acquired and a journal is created. At this point if the other thread attempts to write it will encounter the SQLITE_BUSY error. So given this one must also take care not to introduce self dead locks. At least thats my understanding of it! _______________________________________________ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
