From: Mark Kirkwood <markir@paradise.net.nz>
To: Craig A. James <cjames@modgraph-usa.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: Simple join optimized badly?
Date: Mon, 09 Oct 2006 16:38:34 +1300
Message-ID: <4529C43A.3050503@paradise.net.nz> (raw)
In-Reply-To: <4529B7E8.8080606@modgraph-usa.com>
References: <45274A77.7080005@modgraph-usa.com>
<18722.1160236300@sss.pgh.pa.us>
<5f820f750610071850o6ed0b19o162d65d1987b2a8c@mail.gmail.com>
<200610081605.03501.josh@agliodbs.com>
<4529A0CA.8000904@modgraph-usa.com>
<4529B6D0.2010206@paradise.net.nz>
<4529B7E8.8080606@modgraph-usa.com>
Craig A. James wrote:
>
> Perhaps you scanned past what I wrote a couple paragraphs farther down.
> I'm going to repeat it because it's the KEY POINT I'm trying to make:
>
> Craig James wrote:
>> Now you might argue that function-cost needs to be added to the
>> optimizer's arsenal of tricks. And I'd agree with you: That WOULD be
>> a better solution than hints. But I need my problem solved TODAY, not
>> next year. Hints can help solve problems NOW that can be brought to
>> the PG team's attention later, and in the mean time let me get my
>> application to work.
True enough - but (aside from the fact that hints might take just as
long to get into the development tree as cost-for-functions might take
to write and put in...) there is a nasty side effect to adding hints -
most of the raw material for optimizer improvement disappears (and hence
optimizer improvement stalls)- why? simply that everyone then hints
everything - welcome to the mess that Oracle are in (and seem to be
trying to get out of recently)!
I understand that it is frustrating to not have the feature you need now
- but you could perhaps view it as a necessary part of the community
development process - your need is the driver for optimizer improvement,
and it can take time.
Now ISTM that hints "solve" the problem by removing the need any further
optimizer improvement at all - by making *you* the optimizer. This is
bad for those of us in the DSS world, where most ad-hoc tools do not
provide the ability to add hints.
Cheers
Mark
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To: pgsql-performance@postgresql.org
Cc: markir@paradise.net.nz, cjames@modgraph-usa.com
Subject: Re: Simple join optimized badly?
In-Reply-To: <4529C43A.3050503@paradise.net.nz>
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