Re: Reduction in WAL for UPDATEs

Kenneth Marshall wrote:
> We use DSPAM as one of our anti-spam options. Its UPDATE pattern is to
> increment a spam counter or a not-spam counter while keeping the user and
> token information the same. This would benefit from this optimization.
> Currently we are forced to use MySQL with MyISM tables to support the
> update load, although PostgreSQL 8.2 performance is right at the I/O
> break-even point for switching databases. With HOT and more optimized
> UPDATE I/O, 8.3 would give us enough I/O headroom to switch to PostgreSQL.

Interesting. I've switched from MySQL to PostgreSQL for dspam, because
of concurrency issues with MyISAM which caused bad performance.

I am eager to see how much HOT speeds of my setup, though ;-)

BTW, the "COMMIT NOWAIT" feature Simon Riggs proposed should provide
a huge speedup too, since dspam runs one transaction for each token
it has to update.

greetings, Florian Pflug