Query tuning help

From: CS DBA <cs_dba(at)consistentstate(dot)com>
To: "pgsql-performance(at)postgresql(dot)org" <pgsql-performance(at)postgresql(dot)org>
Subject: Query tuning help
Date: 2011-10-11 17:52:35
Message-ID: 4E948263.8040305@consistentstate.com
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Hi all ;

I'm trying to tune a difficult query.

I have 2 tables:
cust_acct (9million rows)
cust_orders (200,000 rows)

Here's the query:

SELECT
a.account_id, a.customer_id, a.order_id, a.primary_contact_id,
a.status, a.customer_location_id, a.added_date,
o.agent_id, p.order_location_id_id,
COALESCE(a.customer_location_id, p.order_location_id) AS
order_location_id
FROM
cust_acct a JOIN
cust_orders o
ON a.order_id = p.order_id;

I can't get it to run much faster that about 13 seconds, in most cases
it's more like 30 seconds.
We have a box with 8 2.5GZ cores and 28GB of ram, shared_buffers is at 8GB

I've tried separating the queries as filtering queries & joining the
results, disabling seq scans, upping work_mem and half a dozen other
approaches. Here's the explain plan:

Hash Join (cost=151.05..684860.30 rows=9783130 width=100)
Hash Cond: (a.order_id = o.order_id)
-> Seq Scan on cust_acct a (cost=0.00..537962.30 rows=9783130
width=92)
-> Hash (cost=122.69..122.69 rows=2269 width=12)
-> Seq Scan on cust_orders o (cost=0.00..122.69 rows=2269
width=12)

Thanks in advance for any help, tips, etc...

--
---------------------------------------------
Kevin Kempter - Constent State
A PostgreSQL Professional Services Company
www.consistentstate.com
---------------------------------------------

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