On Thu, Jun 20, 2013 at 10:35 AM, Andres Freund <and...@2ndquadrant.com> wrote: >> But I'm still on the fence about whether this is really a valid test. > > I think it shows that we need to be careful and do further performance > evaluations and/or alleviate the pain by making things cheaper (say, a > "ddl counter" in shared mem, allowing to cache snapshots for the > syscache). If that artificial test hadn't shown problems I'd have voted > for just going ahead and not worry further.
I tried a general snapshot counter that rolls over every time any transaction commits, but that doesn't help much. It's a small improvement on general workloads, but it's not effective against this kind of hammering. A DDL counter would be a bit more expensive because we'd have to insert an additional branch into GetSnapshotData() while ProcArrayLock is held, but it might be tolerable. Do you have code for this (or some portion of it) already? -- 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