Scott,
> Well, you can always use the trick of putting an on insert / delete
> trigger on the table that maintains a single row table with the current
> count. That way, whenever a row is added or removed, the count is
> updated. this will slow down inserts and deletes a little, but TANSTAAFL.
BTW, I tested this for a client. I found the performance penalty on inserts
and updates to be:
-- For a single stream of intermittent updates from a single connection
on an adequately powered server with moderate disk support (IDE Linux RAID)
(100 inserts/updates per minute, with VACUUM every 5 minutes)
PL/pgSQL Trigger: 20% penalty C Trigger: 9-11% penalty
-- For 5 streams of inserts and updates at high volume on an overloaded
server with moderate disk support (dual fast SCSI disks)
(1000 inserts/updates per minute, vacuum every 5 minutes)
PL/pgSQL Trigger: 65% penalty C Trigger: 40% penalty
Please note that the effective performance penalty on inserts and updates was
dramatically higher for large batches of updates than for small ones.
--
Josh Berkus
Aglio Database Solutions
San Francisco
