Re: two memory-consuming postgres processes

On May 2, 2008, at 1:13 PM, Tom Lane wrote:
> I don't think you should figure on more than 1GB being
> usefully available to Postgres, and you can't give all or even most of
> that space to shared_buffers.

So how should I divide say a 512 MB between shared_buffers and, um,
what else? (new to pg tuning :)

I naively thought that if I have a 100,000,000 row table, of the form
(integer,integer,smallint,date), and add a real coumn to it, it will
scroll through the memory reasonably fast. Yet when I had
shared_buffers=128 MB, it was hanging there 8 hours before I killed
it, and now with 1500MB is paging again for several hours with no end
in sight. Why can't it just add a column to a row at a time and be
done with it soon enough? :) It takes inordinately long compared to a
FORTRAN or even python program and there's no index usage for this
table, a sequential scan, why all the paging?

Cheers,
Alexy