On Sun, 2009-11-15 at 16:07 +0200, Heikki Linnakangas wrote: > - When replaying b-tree deletions, we currently wait out/cancel all > running (read-only) transactions. We take the ultra-conservative > stance because we don't know how recent the tuples being deleted are. > If we could store a better estimate for latestRemovedXid in the WAL > record, we could make that less conservative.
I think I can improve on the way we do this somewhat. When we GetConflictingVirtualXIDs() with InvalidTransactionId we include all backends. If a query can only see currently-running xacts then it cannot see any data that is being cleaned up because its xmin > latestCompletedXid. Put another way, Assert(latestRemovedXid <= latestCompletedXid) -- Simon Riggs www.2ndQuadrant.com -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
