Hello Pavel, This makes sense but I have shared cache on.
Thanks. --- On Thu, 5/12/11, Pavel Ivanov <paiva...@gmail.com> wrote: > From: Pavel Ivanov <paiva...@gmail.com> > Subject: Re: [sqlite] Multi-threading Common Problem > To: "General Discussion of SQLite Database" <sqlite-users@sqlite.org> > Date: Thursday, May 12, 2011, 5:55 PM > > "After a BEGIN EXCLUSIVE, no > other database connection except for read_uncommitted > connections will be able to read the database and no other > connection without exception will be able to write the > database until the transaction is complete." > > > > This tells me that reads outside of a transaction > would be permitted while an exclusive transaction is taking > place. > > This works only when shared cache mode is turned on and > only within > the same process. Nothing uncommitted can be read between > processes or > between different connections in the same process when > shared cache is > turned off. > > > Pavel > > > On Thu, May 12, 2011 at 4:26 PM, John Deal <bassd...@yahoo.com> > wrote: > > Good question. Very possible my understanding is not > complete. > > > > I have basically read and write transactions, each > potentially with several accesses to the DB. I want to > ensure that if a write transaction is happening, no read > transactions are in progress since it would be possible to > have obtain incomplete data (mixture of some reads being > valid but other no longer valid because the write > transaction changed them). In other words, a read > "transaction" (I do not use a transaction for the reads) > consists of multiple pieces of data that makeup a set that I > want to ensure is valid as a set. > > > > It is my understanding that a transaction (which I do > use for the write transaction which is also a set) locks the > DB for writes but not reads. If a transaction does lock the > DB for exclusive access then you are correct, I do not need > the OS mutexes. Maybe I do not understand the following: > > > > "After a BEGIN EXCLUSIVE, no other database connection > except for read_uncommitted connections will be able to read > the database and no other connection without exception will > be able to write the database until the transaction is > complete." > > > > This tells me that reads outside of a transaction > would be permitted while an exclusive transaction is taking > place. > > > > If a write transaction is not taking place, I want to > allow multiple reads which the OS rwlock allows. > > > > Any enlightenment would be welcomed. > > > > Thanks. > > > > --- On Thu, 5/12/11, Roger Binns <rog...@rogerbinns.com> > wrote: > > > >> From: Roger Binns <rog...@rogerbinns.com> > >> Subject: Re: [sqlite] Multi-threading Common > Problem > >> To: sqlite-users@sqlite.org > >> Date: Thursday, May 12, 2011, 4:01 PM > >> -----BEGIN PGP SIGNED MESSAGE----- > >> Hash: SHA1 > >> > >> On 05/12/2011 09:38 AM, John Deal wrote: > >> > I have been working for weeks on this and I > feel there > >> must be something simple I am overlooking. > >> > >> Why are you discarding SQLite's builtin and tested > mutexes > >> and then > >> effectively reimplementing your own to get the > same > >> effect? > >> > >> Or bigger picture question what is it you are > trying to > >> achieve in the first > >> place? > >> > >> Roger > >> -----BEGIN PGP SIGNATURE----- > >> Version: GnuPG v1.4.11 (GNU/Linux) > >> > >> > iEYEARECAAYFAk3MPIkACgkQmOOfHg372QQzjgCg3106pWiiUMuOQay+2ONv3G0c > >> ZvQAnAvBFXI+A8ae8tV9yXRmz7IZgid6 > >> =jehy > >> -----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 > > > _______________________________________________ > 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
