On Fri, Jan 18, 2013 at 3:31 AM, Jeff Davis <pg...@j-davis.com> wrote: > So, I attached a new version of the patch that doesn't look at the VM > for tables with fewer than 32 pages. That's the only change.
That certainly seems worthwhile, but I still don't want to get rid of this code. I'm just not seeing a reason why that's something that desperately needs to be done. I don't think this is a barrier to anything else we want to do, and it might well be that the situations where this patch would hurt us are currently masked by other bottlenecks, but won't be always. Right now, the vast majority of heap updates don't need to pin the visibility map page; with this change, all of them do. Now, I accept that your test results show that that doesn't matter, but how can that not be an artifact of some kind? Can we really credit that accessing two pages costs no more than accessing one? To what countervailing factor could we plausibly attribute that? Now, even if it costs more in some narrow sense, the difference might not be enough to matter. But without some big gain on the other side, why tinker with it? -- 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
