Tom wrote:
>
>I find it really really hard to believe that it's wise to run with
>sort_mem exceeding 2 gig ;-). Does that installation have so much
>RAM that it can afford to run multiple many-Gb sorts concurrently?
I don't do 2 gig... but I found 0.3 gig helped on a not-too-large system.
In a nightly load of a datawarehousing application I have
a number of places where I do:
set sort_mem=300000; create table new_whatevers as select distinct whatever from import_table; set sort_mem=10000;
and
set sort_mem=100000; select count(*),b from a group by b; set sort_mem=10000;
when the optimizer likes hash aggregates.
It significantly (8 hours -> 6 hours) reduces the nightly processing
of my log-file analysis database. If my modest system benefited
from 1/3 gig, it wouldn't surprise me if a large system benefits
from 2 gig.
If more info's useful, I'd be happy to provide some.
Ron
