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. -- 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
