On Sun, 2009-11-15 at 19:36 +0200, Heikki Linnakangas wrote: > Simon Riggs wrote: > > On Sun, 2009-11-15 at 16:07 +0200, Heikki Linnakangas wrote: > > > >> The assumption that b-tree vacuum records don't need conflict > >> resolution because we did that with the additional cleanup-info record > >> works ATM, but it hinges on the fact that we don't delete any tuples > >> marked as killed while we do the vacuum. > > > >> That seems like a low-hanging > >> fruit that I'd actually like to do now that I spotted it, but will > >> then need to fix b-tree vacuum records accordingly. We'd probably need > >> to do something about the previous item first to keep performance > >> acceptable. > > > > We can optimise that by using the xlog pointer of the HeapInfo record. > > Any blocks cleaned that haven't been further updated can avoid > > generating further btree deletion records. > > Sorry, I don't understand that. (Remember that marking index tuples as > killed is not WAL-logged.)
Remember that blocks are marked with an LSN? When we insert a WAL record it has an LSN also. So we can tell which btree blocks might have had been written to after the HeapInfo record is generated. So if a block hasn't been recently updated or it doesn't have any killed tuples then we need not generate a record to handle a possible conflict. -- 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
