On 9/21/07, Tom Lane <[EMAIL PROTECTED]> wrote: > > > > but control never gets that far because neither xmin nor xmax is > committed yet. We could fix that, probably, by considering the > xmin=xmax case in the xmin-in-progress case further up; but the > HEAP_UPDATED exclusion is still a problem. Still, it seems like this > is leaving some money on the table when you think about pruning a HOT > chain. Can we improve on it easily? > > May be we can, but it would get a bit tricky. There might be a transaction looking at the first tuple in the chain and waiting for this (inserting-deleting) transaction to finish. If the waiting transaction is running in READ COMMITTED mode, it would then follow the update chain. Removing any intermediate tuples without fixing the previous tuple's xmax/ctid (or redirected line pointer) would be tricky.
Thanks, Pavan -- Pavan Deolasee EnterpriseDB http://www.enterprisedb.com
