Re: PG_DUMP and table locking in PG7.4

On Wed, Nov 16, 2005 at 09:27:55AM +0100, Yann Michel wrote:
> On Wed, Nov 16, 2005 at 08:28:31AM +0100, Martijn van Oosterhout wrote:
> > On Wed, Nov 16, 2005 at 08:09:31AM +0100, Yann Michel wrote:
> > > Well, thanks for all the answers. Are the locks then released once they
> > > are not needed any more like in 2PC?
> >
> > 2PC doesn't release any locks, it can't to maintain integrity.
>
> Aehm. sorry I meant 2PL ... all this accronyms... ;-)
> The normal 2PL releases the locks once they are not needed anymore but
> can not aquire new ones. Strict 2PL releases them all at one point.

Ah yes, PostgreSQL doesn't use 2PL, it uses MVCC. quick overview here:

http://linuxgazette.net/issue68/mitchell.html

> Thanks. BTW: Is there anything about locks and their meaning inside of
> the Docs? If not, wouldn't that be nice?

Check here:

http://www.postgresql.org/docs/8.0/interactive/mvcc.html

Under "Explicit Locking" it lists all the locks and what they're for.

Hope this helps,
--
Martijn van Oosterhout <kleptog(at)svana(dot)org> http://svana.org/kleptog/
> Patent. n. Genius is 5% inspiration and 95% perspiration. A patent is a
> tool for doing 5% of the work and then sitting around waiting for someone
> else to do the other 95% so you can sue them.