Date: Tue, 6 Jun 2006 11:29:49 -0400
From: Andrew Sullivan <ajs@crankycanuck.ca>
To: pgsql-performance@postgresql.org
Subject: Re: Some queries starting to hang
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On Tue, Jun 06, 2006 at 11:06:09AM -0400, Tom Lane wrote:
> > it was properly instrumented. That way, the OP might have been able to
> > discover the root cause himself...
> 
> I don't think that helps, as it just replaces one uncertainty by
> another: how far did the EXPLAIN really get towards completion of the
> plan?  You still don't have any hard data.

Well, you _might_ get something useful, if you're trying to work on a
maladjusted production system, because you get to the part that trips
the limit, and then you know, "Well, I gotta fix it that far,
anyway."

Often, when you're in real trouble, you can't or don't wait for the
full plan to come back from EXPLAIN ANALYSE, because a manager is
helpfully standing over your shoulder asking whether you're there
yet.  Being able to say, "Aha, we have the first symptom," might be
helpful to users.  Because the impatient simply won't wait for the
full report to come back, and therefore they'll end up flying blind
instead.  (Note that "the impatient" is not always the person logged
in and executing the commands.)

A

-- 
Andrew Sullivan  | ajs@crankycanuck.ca
I remember when computers were frustrating because they *did* exactly what 
you told them to.  That actually seems sort of quaint now.
		--J.D. Baldwin