Re: EXPLAIN ANALYZE printing logical and hardware I/O per-node

On Dec 16, 2007 1:03 AM, Heikki Linnakangas <heikki@enterprisedb.com> wrote:

> Gokulakannan Somasundaram wrote:
> > I was going to say that I'm really only interested in physical I/O.
> Logical
> >> I/O which is satisfied by the kernel cache is only marginally
> interesting
> >> and
> >> buffer fetches from Postgres's shared buffer is entirely uninteresting
> >> from
> >> the point of view of trying to figure out what is slowing down a query.
> >
> > Ok the Physical I/Os are already visible, if you enable
> log_statement_stats.
>
> I think you missed the point. What log_statement_stats shows are not
> physical I/Os, they're read() system calls. Unfortunately there's no
> direct way to tell if a read() is satisfied from OS cache or not. Greg's
> suggestion was about how to do that.
>

Oh OK. Thanks for clarifying..

-- 
Thanks,
Gokul.
CertoSQL Project,
Allied Solution Group.
(www.alliedgroups.com)