From: Tom Lane <tgl@sss.pgh.pa.us>
To: Stuart Bishop <stuart@stuartbishop.net>
cc: "pgsql-performance@postgresql.org" <pgsql-performance@postgresql.org>
Subject: Re: A pessimistic planner
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Comments: In-reply-to Stuart Bishop <stuart@stuartbishop.net>
 message dated "Fri, 21 Nov 2014 12:07:27 +0700"
Date: Fri, 21 Nov 2014 00:12:05 -0500
Message-ID: <21114.1416546725@sss.pgh.pa.us>
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Stuart Bishop <stuart@stuartbishop.net> writes:
> I was wondering if the planner should be much more pessimistic,
> trusting in Murphy's Law and assuming the worst case is the likely
> case? Would this give me a much more consistent system?

Well, it would give uniformly awful plans for cases where fast-start
plans are actually useful ... and there are plenty.

We do need to think of ways to account for risk, but I don't think
that jamming the tiller all the way over is likely to be a net
improvement.

			regards, tom lane


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