On Fri, Jul 29, 2011 at 10:20 AM, Hannu Krosing <ha...@2ndquadrant.com> wrote: >> An additional point to think about: if we were willing to insist on >> streaming replication, we could send the commit sequence numbers via a >> side channel rather than writing them to WAL, which would be a lot >> cheaper. > > Why do you think that side channel is cheaper than main WAL ?
You don't have to flush it to disk, and you can use some other lock that isn't as highly contended as WALInsertLock to synchronize it. >> That might even be a reasonable thing to do, because if >> you're doing log shipping, this is all going to be super-not-real-time >> anyway. > > But perhaps you still may want to preserve visibility order to be able > to do PITR to exact transaction "commit", no ? Maybe. In practice, I suspect most people won't be willing to pay the price a feature like this would exact. -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
