On Tue, Nov 22, 2011 at 9:21 PM, Robert Haas <robertmh...@gmail.com> wrote: > On Tue, Nov 22, 2011 at 3:23 PM, Simon Riggs <si...@2ndquadrant.com> wrote: >> Some time ago, I changed GetOldestXmin() to ignore procs in other >> databases resulting in a potentially later xmin. >> >> GetSnapshotData() was not touched when that happened, even though the >> comments say "...This is the same computation done by >> GetOldestXmin(true, true)." The transam/README file says it stronger >> "GetSnapshotData also performs an oldest-xmin calculation (which had >> better >> match GetOldestXmin's)". Doh. >> >> As a result, VACUUM ignores procs in other databases, whereas HOT does >> not. That means we aren't cleaning up as much as we could do when >> running multiple databases. If its OK for VACUUM, then it must be OK >> for HOT cleanup also. >> >> Attached patch ignores procs in other databases during >> GetSnapshotData() when IsMVCCSnapshot(), using similar coding to >> GetOldestXmin(). >> >> Any doubters? > > I think this is unsafe for shared catalogs.
I think so too. Thats why it uses IsMVCCSnapshot() to confirm when it is safe to do so. -- Simon Riggs 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
