From: Josh Berkus <josh@agliodbs.com>
Organization: PostgreSQL @ Sun
To: pgsql-performance@postgresql.org
Subject: Re: PostgreSQL Configuration Tool for Dummies
Date: Wed, 27 Jun 2007 11:02:35 -0700
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Greg,

> I'd like to see people have a really simple set of questions to get them
> past the completely undersized initial configuration phase, then ship them
> toward resources to help educate about the parts that could be problematic
> for them based on what they do or don't know.  I don't see an
> inconsistancy that I'd expect people to have a reasonable guess for
> max_connections, while also telling them that setting sort_mem is
> important, a middle value has been assigned, but a really correct setting
> isn't something they can expect the simple config tool to figure out for
> them; here's a pointer to the appropriate documentation to learn more.

I disagree that this is acceptable, especially when we could set a better 
value using an easy-to-understand question. It's also been my experience (in 
3 years of professional performance tuning) that most users *don't* have an 
accurate guess for max_connections.

I'm really not clear on why you think "what flavor of application do you 
have?" is a difficult question.  It's certainly one that my clients were able 
to answer easily.  Overall, it seems like you're shooting for a conf tool 
which only really works for web apps, which isn't my personal goal or I think 
a good use of our time.

> I'm still of the opinion that recommendations for settings like
> max_fsm_pages and maintenance_work_mem should come out of a different type
> of tool that connects to the database.

Well, there's several steps to this:

1) Run conf tool when installing PG;
2) Run conf tool++ after application is first up and running;
3) Run conf tool++ after application has been in production

The (1) tool should at least provide a configuration which isn't going to lead 
to long term issues.  For example, dramatically underallocating fsm_pages can 
result in having to run VACUUM FULL and the associated downtime, so it's 
something we want to avoid at the outset.

-- 
Josh Berkus
PostgreSQL @ Sun
San Francisco