Bill,
> The only one that seems practical (to me) is random_page_cost. The
> others are all configuration options that I (as a DBA) want to be able
> to decide for myself.
Actually, random_page_cost *should* be a constant "4.0" or "3.5", which
represents the approximate ratio of seek/scan speed which has been
relatively constant across 6 years of HDD technology. The only reason we
make it a configuration variable is that there's defects in our cost model
which cause users to want to tinker with it.
Mind you, that's gotten better in recent versions as well. Lately I mostly
tinker with effective_cache_size and the various cpu_* stats rather than
modifying random_page_cost.
--
--Josh
Josh Berkus
PostgreSQL @ Sun
San Francisco