Slow query

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От Oleg Lebedev
Тема Slow query
Дата
Msg-id 993DBE5B4D02194382EC8DF8554A5273113E5A@postoffice.waterford.org
обсуждение исходный текст
Ответы Re: Slow query  (Josh Berkus <josh@agliodbs.com>)
Re: Slow query  (Stephan Szabo <sszabo@megazone23.bigpanda.com>)
Re: Slow query  (Josh Berkus <josh@agliodbs.com>)
Re: Slow query  (Tom Lane <tgl@sss.pgh.pa.us>)
Список pgsql-performance
Please help me speed up the following query. It used to run in 2-5 sec., but now it takes 2-3 mins!
I ran VACUUM FULL ANALYZE and REINDEX.
SELECT * FROM media m
WHERE m.mediatype = (SELECT objectid FROM mediatype WHERE medianame='Audio')
AND EXISTS
        (SELECT * FROM
                (SELECT objectid AS mediaid
                FROM media
                WHERE activity='347667'
                UNION
                SELECT ism.media AS mediaid
                FROM intsetmedia ism, set s
                WHERE ism.set = s.objectid
                AND s.activity='347667' ) AS a1
        WHERE a1.mediaid = m.objectid
        LIMIT 1)
ORDER BY medianame ASC, status DESC
 
Basically it tries to find all Audios that are either explicitly attached to the given activity, or attached to the given activity via a many-to-many relationship intsetmedia which links records in table Interaction, Set, and Media.
I attached the output of EXPLAIN and schemas and indexes on the tables involved. Most of the fields are not relevant to the query, but I listed them anyways. I discarded trigger information, though.
Thanks for your help.
 
Oleg

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