[PERFORM] Query tuning help

[CS DBA]

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...












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