On Thu, 2006-06-08 at 10:27 -0400, Tom Lane wrote:
> Simon Riggs <simon@2ndquadrant.com> writes:
> > On Wed, 2006-06-07 at 17:28 -0400, Tom Lane wrote:
> >> The overhead seems to be on the order of a couple tens of percent usually.
> >> I don't see how that makes the difference between an EXPLAIN ANALYZE you
> >> can run and one you can't.
>
> > Well, thats not my experience and doesn't match others posted on
> > -hackers.
>
> > A simple test with pgbench shows the timing overhead of EXPLAIN ANALYZE
> > to be consistently above 500% (or more than +400%, depending upon how
> > you style those numbers).
>
> I think we ought to find out why your machine is so broken.
> I'm too lazy to pull up any of my other machines right now, but this is
> generally consistent with my experience ever since EXPLAIN ANALYZE was
> written.
Great. Well it isn't consistent with mine, or others who've posted to
this list.
> So: what's your platform exactly?
FC5, Intel laptop running cvstip, new in January.
But thats irrelevant. I'm not a user, I solve others problems, as you
know. Hence my interest in a usable tool to do that.
So far we have myself, Kevin, Martijn and Luke all saying there is a
distortion or a massive overhead caused by EXPLAIN ANALYZE.
http://archives.postgresql.org/pgsql-hackers/2006-03/msg00954.php
http://archives.postgresql.org/pgsql-patches/2006-05/msg00168.php
It's real. I won't press the point further.
-- Simon Riggs EnterpriseDB http://www.enterprisedb.com
