From: Kevin Grittner <Kevin.Grittner@wicourts.gov>
To: Bryce Nesbitt <bryce2@obviously.com>
To: pgsql-performance@postgresql.org
Subject: Re: 512,600ms query becomes 7500ms... but why? Postgres 8.3 query planner quirk?
Date: Fri, 12 Feb 2010 09:09:41 -0600
Message-ID: <4B751AD5020000250002F248@gw.wicourts.gov> (raw)
In-Reply-To: <4B723042.7090406@obviously.com>
References: <4B723042.7090406@obviously.com>
Bryce Nesbitt <bryce2@obviously.com> wrote:
> I've got a very slow query, which I can make faster by doing
> something seemingly trivial.
Out of curiosity, what kind of performance do you get with?:
EXPLAIN ANALYZE
SELECT contexts.context_key
FROM contexts
JOIN articles ON (articles.context_key = contexts.context_key)
JOIN matview_82034 ON (matview_82034.context_key =
contexts.context_key)
WHERE EXISTS
(
SELECT *
FROM article_words
JOIN words using (word_key)
WHERE context_key = contexts.context_key
AND word = 'insider'
)
AND EXISTS
(
SELECT *
FROM article_words
JOIN words using (word_key)
WHERE context_key = contexts.context_key
AND word = 'trading'
)
AND EXISTS
(
SELECT *
FROM virtual_ancestors a
JOIN bp_categories ON (bp_categories.context_key =
a.ancestor_key)
WHERE a.context_key = contexts.context_key
AND lower(bp_categories.category) = 'law'
)
AND articles.indexed
;
(You may have to add some table aliases in the subqueries.)
If you are able to make a copy on 8.4 and test the various forms,
that would also be interesting. I suspect that the above might do
pretty well in 8.4.
-Kevin
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To: pgsql-performance@postgresql.org
Cc: Kevin.Grittner@wicourts.gov, bryce2@obviously.com
Subject: Re: 512,600ms query becomes 7500ms... but why? Postgres 8.3 query planner quirk?
In-Reply-To: <4B751AD5020000250002F248@gw.wicourts.gov>
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