Hello Roger, Sorry to be so brain-dead but I am still confused. I have multiple threads, each with their own DB connection. I want to allow multiple readers accessing the DB at the same time since nothing is changing. However, if a writes is to take place, I want all readers to finish their reads and give the writer exclusive access. Once the writer is done, the readers can come back in.
I have all writes in transactions. If I deactivate my pthread_rwlock() that enforce the above, several writes fail with a "database locked" error (I assume it is returning SQLITE_BUSY). With my pthread_rwlock(), I have multiple threads reading the DB and my writes get the exclusive access they need. Now I could loop on the write until it gets in but that seems very wasteful. So how do I implement the equivalent of a pthread_rwlock() using SQLite mechinisms? Thanks, John --- On Tue, 5/24/11, Roger Binns <rog...@rogerbinns.com> wrote: > From: Roger Binns <rog...@rogerbinns.com> > Subject: Re: [sqlite] Multi-threading Common Problem > To: "General Discussion of SQLite Database" <sqlite-users@sqlite.org> > Date: Tuesday, May 24, 2011, 3:10 AM > -----BEGIN PGP SIGNED MESSAGE----- > Hash: SHA1 > > On 05/23/2011 09:12 PM, John Deal wrote: > > I guess I am lost on how to obtain a many reader or > one writer mutex in SQLite. > > You are confusing locks on the database and locks in the > library on a > sqlite3 pointer. The latter is what the mutex alloc > function you reference > is about and there there is no reader/writer > mechanism. Access has to be > serialized. > > > You are correct in the locking article referenced I > want a mutex that can have the lock states of shared, > pending, and exclusive. > > Those are locks on the database which you get through > regular operations and > transactions. > > Roger > -----BEGIN PGP SIGNATURE----- > Version: GnuPG v1.4.11 (GNU/Linux) > > iEYEARECAAYFAk3bWeIACgkQmOOfHg372QQf8QCgjlawQMJWJ1I3/6OqMkczXswk > VWQAmgLzGifXbh9UJpuEdUTTZl8e8xYp > =rXCY > -----END PGP SIGNATURE----- > _______________________________________________ > 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
