Andres Freund wrote: > On 2014-05-15 17:37:14 -0400, Alvaro Herrera wrote: > > Andres Freund wrote: > > > On 2014-05-15 15:40:06 -0400, Robert Haas wrote: > > > > On Thu, May 15, 2014 at 2:34 PM, Bruce Momjian <br...@momjian.us> wrote: > > > > > > If the larger clog size is a show-stopper (and I'm not sure I have an > > > > intelligent opinion on that just yet), one way to get around the > > > > problem would be to summarize CLOG entries after-the-fact. Once an > > > > XID precedes the xmin of every snapshot, we don't need to know the > > > > commit LSN any more. So we could read the old pg_clog files and write > > > > new summary files. Since we don't need to care about subcommitted > > > > transactions either, we could get by with just 1 bit per transaction, > > > > 1 = committed, 0 = aborted. Once we've written and fsync'd the > > > > summary files, we could throw away the original files. That might > > > > leave us with a smaller pg_clog than what we have today. > > > > > > I think the easiest way for now would be to have pg_clog with the same > > > format as today and a rangewise much smaller pg_csn storing the lsns > > > that are needed. That'll leave us with pg_upgrade'ability without > > > needing to rewrite pg_clog during the upgrade. > > > > Err, we're proposing a patch to add timestamps to each commit, > > http://www.postgresql.org/message-id/20131022221600.ge4...@eldon.alvh.no-ip.org > > which does so in precisely this way. > > I am not sure where my statements above conflict with committs?
I didn't say it did ... -- Álvaro Herrera http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
