| From: | Michael Engelhart <mengelhart(at)mac(dot)com> | 
|---|---|
| To: | pgsql-performance(at)postgresql(dot)org | 
| Subject: | sequential scan performance | 
| Date: | 2005-05-29 13:27:26 | 
| Message-ID: | D520F8B3-20D6-4272-A6D6-8B690871DE73@mac.com | 
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| Lists: | pgsql-performance | 
Hi -
I have a table of about 3 million rows of city "aliases" that I need  
to query using LIKE - for example:
select * from city_alias where city_name like '%FRANCISCO'
When I do an EXPLAIN ANALYZE on the above query, the result is:
  Seq Scan on city_alias  (cost=0.00..59282.31 rows=2 width=42)  
(actual time=73.369..3330.281 rows=407 loops=1)
    Filter: ((name)::text ~~ '%FRANCISCO'::text)
Total runtime: 3330.524 ms
(3 rows)
this is a query that our system needs to do a LOT.   Is there any way  
to improve the performance on this either with changes to our query  
or by configuring the database deployment?   We have an index on  
city_name but when using the % operator on the front of the query  
string postgresql can't use the index .
Thanks for any help.
Mike
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