Andrew, thank you very much for reply ! I already update my bookmark for 8.3 which is my current version, http://www.postgresql.org/docs/8.3/static/explicit-locking.html, i see new things here, like a comparative table.
Yep, seems like ACCESS EXCLUSIVE is a bad idea, at least now :p ! i check your recommendation about to use SHARE mode, but in http://www.postgresql.org/docs/8.3/static/explicit-locking.html i see that SHARE mode doesn't lock against itself, so, another thread using the same mode will be able to access the tables for update ! or i'm reading bad *Table 13-2. Conflicting lock modes*. Meanwhile i understand well which mode to use in which case i reduce my lock level to EXCLUSIVE, which lock against itself but let SELECT to do his job ! Cheers, Alan Acosta On Mon, Feb 28, 2011 at 1:10 PM, Andrew Sullivan <a...@crankycanuck.ca>wrote: > On Mon, Feb 28, 2011 at 12:43:58PM -0500, Alan Acosta wrote: > > > I'm using lock with ACCESS EXCLUSIVE in several of my tables to assure > that > > only one process write in those tables at same time > > Why are you doing that? It sounds like a bad idea to me. > > But anyway, I believe that the SHARE lock (which is what CREATE INDEX > uses) ought to work. It should prevent any concurrent data > alterations in the table. > > Also, > > > May be a little newbie question, but i cannot find this answer in > > http://www.postgresql.org/docs/8.1/static/explicit-locking.html or > similar > > those are the docs for 8.1.x. Note that it was EOL'd last November: > > http://wiki.postgresql.org/wiki/PostgreSQL_Release_Support_Policy > > > pages, i really want to know if new rows inserted in an open transaction > > will be read it by another threads or this new rows are invisible no > matter > > the mode of the transaction. > > Rows inserted by an uncommitted transaction are invisible to everyone > else until the transaction commits. Postgres doesn't have dirty > reads. If you have an open transaction and you look at a table where > another transaction has committed, then you will or will not see the > resulting rows depending on whether you are in READ COMMITTED or > SERIALIZABLE isolation mode, respectively. > > A > > -- > Andrew Sullivan > a...@crankycanuck.ca > > -- > Sent via pgsql-general mailing list (pgsql-general@postgresql.org) > To make changes to your subscription: > http://www.postgresql.org/mailpref/pgsql-general >
