On Fri, 22 Aug 2003 12:18:02 -0400, Jan Wieck <JanWieck@Yahoo.com>
wrote:
>Okay, my proposal would be to have a VACUUM mode where it tells the
>buffer manager to only return a page if it is already in memory
But how can it know? Yes, we know exactly what we have in PG shared
buffers. OTOH we keep telling people that they should configure
moderate values for shared_buffers because the OS is better at
caching. Your CACHEONLY VACUUM wouldn't catch those pages that are in
the OS cache but not in the shared buffers, although they are
retrievable at almost the same low cost.
We should not try to avoid _any_ physical disk access. It's good
enough to avoid useless reads. Hence my proposal for a reclaimable
space list ...
Servus
Manfred