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Subject: Re: please help on query
From: Hannu Krosing <hannu@tm.ee>
To: Luis Alberto Amigo Navarro <lamigo@atc.unican.es>
Cc: pgsql-hackers@postgresql.org
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On Thu, 2002-07-11 at 17:22, Luis Alberto Amigo Navarro wrote:
> I can't improve performance on this query:


This _may_ work.

SELECT
    supplier.name,
    supplier.address
  FROM
    supplier,
    nation,
 WHERE supplier.suppkey IN (
    SELECT part.partkey
      FROM part
     WHERE part.name like 'forest%'
     INNER JOIN partsupp ON part.partkey=partsupp.partkey
     INNER JOIN (
         SELECT 0.5*(sum(lineitem.quantity)::FLOAT) as halfsum
           FROM lineitem
          WHERE lineitem.partkey=partsupp.partkey
            AND shipdate >= '1994-01-01'
            AND shipdate <  '1995-01-01'
     ) li ON partsupp.availqty > halfsum
  )
  AND supplier.nationkey=nation.nationkey
  AND nation.name='CANADA'
ORDER BY supplier.name;

---------------
Hannu