Martin Marques escribió: > On Sat, 22 Jul 2006, Alvaro Herrera wrote: > > >Martin Marques escribió: > >>Is it posible to get an exclusive (read/write) lock on certain rows? I > >>don't want to block the whole table, only certain rows, but I want it to > >>be a read/write lock. > > > >That's what SELECT FOR UPDATE does. > > Hi Alvaro, > > After the SELECT FOR UPDATE other transactions can still see the locked > rows. I want a read/write lock, so no one can access does rows.
SELECT FOR UPDATE acquires an exclusive lock, but other transactions must try to acquire a lock on the rows as well, or they won't be locked. You can try using SELECT FOR SHARE (new as of 8.1) if you want some transactions to hold shared (read) locks. IOW, SELECT FOR UPDATE blocks other SELECTs FOR UPDATE and SELECTs FOR SHARE, but it does not block plain SELECT. -- Alvaro Herrera http://www.CommandPrompt.com/ PostgreSQL Replication, Consulting, Custom Development, 24x7 support ---------------------------(end of broadcast)--------------------------- TIP 1: if posting/reading through Usenet, please send an appropriate subscribe-nomail command to [EMAIL PROTECTED] so that your message can get through to the mailing list cleanly
