Re: Extremely irregular query performance

From: Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>
To: Jean-Philippe Cote <jean-philippe(dot)cote(at)crt(dot)umontreal(dot)ca>
Cc: "'Kenneth Marshall'" <ktm(at)is(dot)rice(dot)edu>, "'Simon Riggs'" <simon(at)2ndquadrant(dot)com>, pgsql-performance(at)postgresql(dot)org
Subject: Re: Extremely irregular query performance
Date: 2006-01-14 04:23:33
Message-ID: 200601140423.k0E4NX019385@candle.pha.pa.us
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Jean-Philippe Cote wrote:
>
>
> Can I actully know whether a given plan is excuted with GEQO on ?
> In other words, if I launch 'explain <query>', I'll get a given plan, but if I re-launch
> the <query> (withtout the 'explain' keyword), could I get a different
> plan given that GEQO induces some randomness ?
>
> >Is it the plan that is different in the fastest case with GEQO or is it
> >the time needed to plan that is causing the GEQO to beat the exhaustive
> >search?

Yes, is it likely that when using GEQO you would get a different plan
each time, so running it with and without EXPLAIN would produce
different plans.

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