Date: Sat, 17 Dec 2005 10:11:19 +1300
From: Mark Kirkwood <markir@paradise.net.nz>
Subject: Re: Simple Join
In-reply-to: <Pine.LNX.4.62.0512152003460.2807@qnivq.ynat.uz>
To: David Lang <dlang@invendra.net>
Cc: Mitch Skinner <lists@arctur.us>, Kevin Brown <blargity@gmail.com>,
	pgsql-performance@postgresql.org
Message-id: <43A32D77.4020500@paradise.net.nz>
MIME-version: 1.0
Content-type: text/plain; format=flowed; charset=ISO-8859-1
Content-transfer-encoding: 7bit
User-Agent: Mozilla Thunderbird 1.0.6 (X11/20051106)
References: <200512141603.52583.blargity@gmail.com>
	<7484.1134600423@sss.pgh.pa.us> <1134629567.14248.27.camel@firebolt>
	<200512150148.16125.blargity@gmail.com>
	<1134644526.14248.60.camel@firebolt>
	<43A1C40D.8040006@paradise.net.nz>
	<Pine.LNX.4.62.0512152003460.2807@qnivq.ynat.uz>

David Lang wrote:
> On Fri, 16 Dec 2005, Mark Kirkwood wrote:
> 
>>
>> Right on. Some of these "coerced" plans may perform much better. If 
>> so, we can look at tweaking your runtime config: e.g.
>>
>> effective_cache_size
>> random_page_cost
>> default_statistics_target
>>
>> to see if said plans can be chosen "naturally".
> 
> 
> Mark, I've seen these config options listed as tweaking targets fairly 
> frequently, has anyone put any thought or effort into creating a test 
> program that could analyse the actual system and set the defaults based 
> on the measured performance?
> 

I am sure this has been discussed before, I found this thread -

http://archives.postgresql.org/pgsql-performance/2004-07/msg00189.php

but I seem to recall others (but offhand can't find any of them).


I think that the real difficultly here is that the construction of the 
test program is non trivial - for instance, the best test program for 
tuning *my* workload is my application with its collection of data, but 
it is probably not a good test program for *anyone else's* workload.

cheers

Mark