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Date: Tue, 6 Jun 2006 11:21:15 -0400 (EDT)
Subject: Re: Some queries starting to hang
From: "A.M." <agentm@themactionfaction.com>
To: pgsql-performance@postgresql.org
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Explain analyze could at least put an asterisk around actual time that
deviated by some factor from the estimated time.

On Tue, June 6, 2006 10:39 am, Simon Riggs wrote:

>
> This is a good example of a case where the inefficiency of EXPLAIN
> ANALYZE would be a contributory factor to it not actually being
> available for diagnosing a problem.
>
> Maybe we need something even more drastic than recent proposed changes
> to EXPLAIN ANALYZE?
>
> Perhaps we could annotate the query tree with individual limits. That
> way a node that was expecting to deal with 1 row would simply stop
> executing the EXPLAIN ANALYZE when it hit N times as many rows (default=no
> limit). That way, we would still be able to see a bad plan even without
> waiting for the whole query to execute - just stop at a point where the
> plan is far enough off track. That would give us what we need: pinpoint
> exactly which part of the plan is off-track and see how far off track it
> is. If the limits were configurable, we'd be able to opt for
> faster-but-less-accurate or slower-yet-100% accuracy behaviour. We
> wouldn't need to worry about timing overhead either then.
>
> e.g. EXPLAIN ANALYZE ERRLIMIT 10 SELECT ...
>
> --
> Simon Riggs
> EnterpriseDB   http://www.enterprisedb.com
>
>
>
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