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From: Scott Marlowe <smarlowe@g2switchworks.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Jim C. Nasby <jnasby@pervasive.com>
Cc: Craig A. James <cjames@modgraph-usa.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: Some queries starting to hang
Date: Tue, 06 Jun 2006 16:14:48 -0500
Message-ID: <1149628487.25526.228.camel@state.g2switchworks.com> (raw)
In-Reply-To: <23270.1149628274@sss.pgh.pa.us>
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On Tue, 2006-06-06 at 16:11, Tom Lane wrote:
> Scott Marlowe <smarlowe@g2switchworks.com> writes:
> > The cost of not aborting on the first sort is that you may never see
> > what the part of the plan is that's killing your query, since you never
> > get the actual plan.
> 
> Well, you can get the plan without waiting a long time; that's what
> plain EXPLAIN is for.  But I still disagree with the premise that you
> can extrapolate anything very useful from an unfinished EXPLAIN ANALYZE
> run.  As an example, if the plan involves setup steps such as sorting or
> loading a hashtable, cancelling after a minute might make it look like
> the setup step is the big problem, distracting you from the possibility
> that the *rest* of the plan would take weeks to run if you ever got to
> it.

Sure, but it would be nice to see it report the partial work.

i.e. I got to using a nested loop, thought there would be 20 rows,
processed 250,000 or so, timed out at 10 minutes, and gave up.

I would find that useful.



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