Thanks for your reply.

Now understanding the optimizer decides to use index or table scan
depending the selectivity of the query, my next question is 'how can I 
increase table scan speed'.

My query is:
SELECT i_id, a_lname FROM item, author WHERE i_a_id=a_id and i_title
LIKE '%BABABABA%'order by i_title asc

I am having difficulty pinpointing why it is slow. At some point, I see
about 16 locks on table item, but all of them are 'row_share' and in
'consistent' state. Is it the lock contention that slows down the query?
If so, how can I remove it?

Due to the wildcard in LIKE condition, the execution plan is 'table
scan'. If 'table scan' is the bottleneck, can you give me some
suggestions about how to improve it? Can I pin the table in memory?

Thanks in advance for your help
Jenny
-- 
Jenny Zhang
Open Source Development Lab Inc 
15275 SW Koll Parkway - Suite H
Beaverton, OR 97006
(503)626-2455 ext 31

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