Date: Wed, 20 Jun 2007 02:24:03 -0400 (EDT)
From: Greg Smith <gsmith@gregsmith.com>
To: pgsql-performance@postgresql.org
Subject: Re: PostgreSQL Configuration Tool for Dummies
In-Reply-To: <200706191254.09777.josh@agliodbs.com>
Message-ID: <Pine.GSO.4.64.0706200155290.16657@westnet.com>
References: <A3AC4FA47DC0B1458C3E5396E685E63302395E63@SAB-DC1.sab.uiuc.edu>
	<Pine.LNX.4.64.0706191205320.25045@asgard.lang.hm>
	<200706191254.09777.josh@agliodbs.com>
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On Tue, 19 Jun 2007, Josh Berkus wrote:

> I don't think the "mostly reads / mostly writes" question covers anything,
> nor is it likely to produce accurate answers.  Instead, we need to ask the
> users to characterize what type of application they are running:
> T1) Please characterize the general type of workload you will be running on
> this database.  Choose one of the following four...

We've hashed through this area before, but for Lance's benefit I'll 
reiterate my dissenting position on this subject.  If you're building a 
"tool for dummies", my opinion is that you shouldn't ask any of this 
information.  I think there's an enormous benefit to providing something 
that takes basic sizing information and gives conservative guidelines 
based on that--as you say, "safe, middle-of-the-road values"--that are 
still way, way more useful than the default values.  The risk in trying to 
make a complicated tool that satisfies all the users Josh is aiming his 
more sophisticated effort at is that you'll lose the newbies.

Scan the archives of this mailing list for a bit.  If you look at what 
people discover they've being nailed by, it's rarely because they need to 
optimize something like random_page_cost.  It's usually because they have 
a brutally wrong value for one of the memory or vacuum parameters that are 
very easy to provide reasonable suggestions for without needing a lot of 
information about the server.

I wouldn't even bother asking how many CPUs somebody has for what Lance is 
building.  The kind of optimizations you'd do based on that are just too 
complicated to expect a tool to get them right and still be accessible to 
a novice.

--
* Greg Smith gsmith@gregsmith.com http://www.gregsmith.com Baltimore, MD