Correcting Hash Join Estimates

From: mark(dot)lubratt(at)indeq(dot)com
To: pgsql-performance(at)postgresql(dot)org
Subject: Correcting Hash Join Estimates
Date: 2005-04-04 05:08:03
Message-ID: 20050404050803.7175.qmail@webmail10.mesa1.secureserver.net
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Hello!

I posted a similar question to this one about a month ago; but, for some
reason, it never seemed to be broadcast eventhough it ended up in the
archives. So, since I'm still struggling with this, I thought I'd
repost...

I'm trying to optimize a query and the EXPLAIN ANALYZE (see link below)
shows that some hash join row estimates are wrong by a factor of 2-3,
and upwards of 7-8. There is a corresponding mis-estimation of the
amount of time taken for these steps. The database is vacuum analyzed
nightly by a cron job. How would I go about tightening up these
errors? I suspect that I need to SET STATISTIC on some columns, but
how can I tell which columns?

Any help would be appreciated.

WinXP (dual Xeon 1.2GB RAM) PgSQL 8.0.1
Explain Analyze: <http://www.indeq.com/EA.txt>
View Definition: <http://www.indeq.com/VGAUA.txt>

The largest table contains about 10,000 rows. All tables have indexes
on their foreign keys.

Thanks!
Mark

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