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Message-ID: <20061012214111.90031.qmail@web31807.mail.mud.yahoo.com>
Date: Thu, 12 Oct 2006 14:41:11 -0700 (PDT)
From: Richard Broersma Jr <rabroersma@yahoo.com>
Subject: Re: Hints proposal
To: Arjen van der Meijden <acmmailing@tweakers.net>,
	Jeff Davis <pgsql@j-davis.com>
Cc: Csaba Nagy <nagy@ecircle-ag.com>, "Jim C. Nasby" <jim@nasby.net>,
	postgres performance list <pgsql-performance@postgresql.org>
In-Reply-To: <452EAE80.5030501@tweakers.net>
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> By the way, wouldn't it be possible if the planner learned from a query 
> execution, so it would know if a choice for a specific plan or estimate 
> was actually correct or not for future reference? Or is that in the line 
> of DB2's complexity and a very hard problem and/or would it add too much 
> overhead?

Just thinking out-loud here...

Wow, a learning cost based planner sounds a-lot like problem for control & dynamical systems
theory.  As I understand it, much of the advice given for setting PostgreSQL's tune-able
parameters are from "RULES-OF-THUMB."  I am sure that effect on server performance from all of the
parameters could be modeled and an adaptive feed-back controller could be designed to tuned these
parameters as demand on the server changes.

Al-thought, I suppose that a controller like this would have limited success since some of the
most affective parameters are non-run-time tune-able.

In regards to query planning, I wonder if there is way to model a controller that could
adjust/alter query plans based on a comparison of expected and actual query execution times.


Regards,

Richard Broersma Jr.