Satoshi Nagayasu <[EMAIL PROTECTED]> writes: > I've done a quick hack to implement PCTFREE on PostgreSQL. > ... > According to my experiments, pgbench score was improved 10% or more > with 1024 bytes free space.
I'm not very enthused about this. Enforcing 12.5% PCTFREE means that you pay 12.5% extra I/O costs across the board for INSERT and SELECT and then hope you can make it back (plus some more) on UPDATEs. pgbench is a completely UPDATE-dominated benchmark and thus it makes such a patch look much better than it would on other workloads. I think the reason Oracle offers this has to do with their overwrite-based storage management; it's not obvious that the tradeoff is as useful for us. There are some relevant threads in our archives here, here, and here: http://archives.postgresql.org/pgsql-patches/2005-04/msg00078.php http://archives.postgresql.org/pgsql-performance/2004-08/msg00402.php http://archives.postgresql.org/pgsql-performance/2003-10/msg00618.php regards, tom lane ---------------------------(end of broadcast)--------------------------- TIP 9: In versions below 8.0, the planner will ignore your desire to choose an index scan if your joining column's datatypes do not match
