On Fri, Mar 9, 2012 at 2:59 PM, Simon Riggs <si...@2ndquadrant.com> wrote: > On Fri, Mar 9, 2012 at 3:46 AM, Robert Haas <robertmh...@gmail.com> wrote: >> On Wed, Mar 7, 2012 at 5:41 PM, Simon Riggs <si...@2ndquadrant.com> wrote: >>>> Case #2 is certainly a problem for FrozenXID as well, because anything >>>> that's marked with FrozenXID is going to look visible to everybody, >>>> including our older snapshots. And I gather you're saying it's also a >>>> problem for HEAP_XMIN_COMMITTED. >>> >>> The problem there is that later subtransactions often have xids that >>> are greater than xmax, so the xid shows as running when we do >>> XidInMVCCSnapshot(), which must then be altered for this one weird >>> case. I tried that and not happy with result. >> >> Altering XidInMVCCSnapshot() seems like a good thing to avoid, but I >> confess I don't quite follow what you're describing here otherwise. >> >>>> I had assumed that the way we were >>>> fixing this problem was to disable these optimizations for >>>> transactions that had more than one snapshot floating around. I'm not >>>> sure whether the patch does that or not, but I think it probably needs >>>> to >>> >>> It does. I thought you already read the patch? >> >> I glanced over it, but did not look through it in detail. I'll do a >> more careful look at your next version. > > I'm not confident about the restrictions this patch imposes and we > aren't close enough to a final version for me to honestly request this > be considered for this release. I think its time to close this door > for now.
OK, makes sense. I was trying to hold my nose, because I really would like to see this stuff work better than it does, but I had my doubts, too. -- 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
