From: "Josh Berkus" <josh@agliodbs.com>
Subject: Re: Optimizing
To: "Jeff Sack" <sackj@alum.rpi.edu>, <pgsql-sql@postgresql.org>
Date: Fri, 09 Nov 2001 07:54:05 -0800
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Jeff,

> Hello all.  I have an academic project that I'm working on and, as
> I'm
> relatively new to optimization techniques and database design, I'm
> wondering if some of you can give me some pointers. 

See the PostgreSQL book review page:
http:\\techdocs.postgresql.org\bookreviews.php
There, you will find reviews of several good books on database design.

> There are several interesting queries that I've been constructing
> just
> to get a feel for this schema, and given that some of these tables
> contain 100,000-200,000 tuples, some queries are taking a good 5-10
> seconds to execute.  I'm just wondering if this is simply the fault
> of
> my schema or are these queries poorly constructed? 

That entirely depends.  If you're doing this on a 3-year-old laptop,
5-10 seconds is a *good* time.  But not on a Proliant 9000.

Here's the rules of indexing:
1. All JOIN columns should be indexed.
2. All criteria (WHERE) columns should be indexed, except 
        those that have a very limited range of values (e.g. BOOLEAN).
3. All ORDER BY columns should be indexed, with the same exception.
4. Multi-column indexes are seldom useful for queries.
5. VACUUM should be performed regularly.
6. If SELECT is very fast and INSERT is very slow, try removing a few
indexes.

Also, you can muck around with runtime settings to you heart's content,
and moving the log files (pgsql/data/xlog) to a seperate drive improves
performance.  There are no quick answers once you've taken the basic
steps.

-Josh


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