From: Tom Lane <tgl@sss.pgh.pa.us>
To: Stefan Kaltenbrunner <stefan@kaltenbrunner.cc>
Cc: Julius Stroffek <Julius.Stroffek@Sun.COM>
Cc: pgsql-performance@postgresql.org
Cc: pgsql-hackers@postgresql.org
Subject: Re: [HACKERS] Proposal: Pluggable Optimizer Interface
Date: Mon, 13 Aug 2007 17:23:23 -0400
Message-ID: <22245.1187040203@sss.pgh.pa.us> (raw)
In-Reply-To: <46C0BD13.107@kaltenbrunner.cc>
References: <46C0B5E4.4020305@sun.com>
<46C0BD13.107@kaltenbrunner.cc>
Stefan Kaltenbrunner <stefan@kaltenbrunner.cc> writes:
> Julius Stroffek wrote:
>> There is a proposal attached to this mail about the interface
>> we would like to implement for switching between different
>> optimizers. Please review it and provide a feedback to us.
> hmm - how does is that proposal different from what got implemented with:
> http://archives.postgresql.org/pgsql-committers/2007-05/msg00315.php
Well, it's a very different level of abstraction. The planner_hook
would allow you to replace the *entire* planner, but if you only want to
replace GEQO (that is, only substitute some other heuristics for partial
search of a large join-order space), doing it from planner_hook will
probably require duplicating a great deal of code. A hook right at the
place where we currently choose "geqo or regular" would be a lot easier
to experiment with.
Replacing GEQO sounds like a fine area for investigation to me; I've
always been dubious about whether it's doing a good job. But I'd prefer
a simple hook function pointer designed in the same style as
planner_hook (ie, intended to be overridden by a loadable module).
The proposed addition of a system catalog and SQL-level management
commands sounds like a great way to waste a lot of effort on mere
decoration, before ever getting to the point of being able to
demonstrate that there's any value in it. Also, while we might accept
a small hook-function patch for 8.3, there's zero chance of any of that
other stuff making it into this release cycle.
regards, tom lane
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To: pgsql-performance@postgresql.org
Cc: tgl@sss.pgh.pa.us, stefan@kaltenbrunner.cc, Julius.Stroffek@Sun.COM, pgsql-hackers@postgresql.org
Subject: Re: [HACKERS] Proposal: Pluggable Optimizer Interface
In-Reply-To: <22245.1187040203@sss.pgh.pa.us>
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