> What is it about the buffer cache that makes it so unhappy being able
to
> hold everything? I don't want to be seen as a cache hit fascist, but
isn't
> it just better if the data is just *there*, available in the
postmaster's
> address space ready for each backend process to access it, rather than
> expecting the Linux cache mechanism, optimised as it may be, to have
to do
> the caching?
The disk cache on most operating systems is optimized. Plus, keeping
shared buffers low gives you more room to bump up the sort memory, which
will make your big queries run faster.
Merlin