I certainly would be interested to see if it improves performance. ---------------------------------------------------------------------------
Simon Riggs wrote: > In Read Committed transactions we take snapshots much more frequently > than transactions begin and commit. It would be help scalability if we > didn't need to re-take a snapshot. That's only helpful if the chances of > seeing the snapshot is relatively high. > > Now that we have virtual transactions we may more frequently find > ourselves taking identical snapshots. > > If we had a counter that incremented each time the main snapshot altered > in a meaningful way we could set that atomically. We could then read > this when we take a snapshot to see if it matches our existing snapshot; > if so then drop the lock quickly and continue with what we already have. > > I can see some downsides to this as well as potential benefits: > > * we ping the counter across CPUs - yes, we will, but that's probably > better than pinging the whole procarray > > * this relies upon the rate of change of snapshots - need to do the math > to see how often this might apply > > Not sure yet myself, but it seems worth recording in case it spurs an > idea from someone else. > > -- > Simon Riggs > 2ndQuadrant http://www.2ndQuadrant.com > > > ---------------------------(end of broadcast)--------------------------- > TIP 2: Don't 'kill -9' the postmaster -- Bruce Momjian <[EMAIL PROTECTED]> http://momjian.us EnterpriseDB http://postgres.enterprisedb.com + If your life is a hard drive, Christ can be your backup. + -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your Subscription: http://mail.postgresql.org/mj/mj_wwwusr?domain=postgresql.org&extra=pgsql-hackers