On Tue, 2010-10-05 at 18:47 +0900, Fujii Masao wrote: > On Tue, Oct 5, 2010 at 5:49 PM, Heikki Linnakangas > <heikki.linnakan...@enterprisedb.com> wrote: > > On 04.10.2010 17:22, Fujii Masao wrote: > >> > >> If we make all the transactions wait until specified standbys have > >> connected to the master, how do we take a base backup from the > >> master for those standbys? We seem to be unable to do that because > >> pg_start_backup also waits forever. Is this right? > > > > Hmm, pg_start_backup() writes WAL, but it doesn't commit. Only a commit > > needs to wait for acknowledgment from the standby, so 'wait forever' > > behavior doesn't necessarily mean that you can't take a base backup. If you > > run it outside a transaction you get an implicit commit, though, which will > > wait, so you might need to do something odd like "begin; select > > pg_start_backup(); rollback". > > Yep. Similarly, we would need to enclose also pg_stop_backup with begin > and rollback.
Presumably we will have an option to *not* wait forever? So we would be able to set the option prior to running the base backup? So there isn't any need to do this rollback trick suggested. pg_start_backup() and pg_stop_backup() have two use cases: 1) ensuring both are sent through to the standby would make it very easy to allow backups from the standby. 2) make sure we don't wait, so we can take a base backup at any time So there's no argument here to prevent it being in a table. -- Simon Riggs www.2ndQuadrant.com PostgreSQL Development, 24x7 Support, Training and Services -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
