Re: 512,600ms query becomes 7500ms... but why? Postgres 8.3 query planner quirk?

From: Kevin Grittner
Subject: Re: 512,600ms query becomes 7500ms... but why? Postgres 8.3 query planner quirk?
Date: ,
Msg-id: 4B751AD5020000250002F248@gw.wicourts.gov
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In response to: 512,600ms query becomes 7500ms... but why? Postgres 8.3 query planner quirk?  (Bryce Nesbitt)
Responses: Re: 512,600ms query becomes 7500ms... but why? Postgres 8.3 query planner quirk?  (Karl Denninger)
Re: 512,600ms query becomes 7500ms... but why? Postgres 8.3 query planner quirk?  (Bryce Nesbitt)
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512,600ms query becomes 7500ms... but why? Postgres 8.3 query planner quirk?  (Bryce Nesbitt, )
 Re: 512,600ms query becomes 7500ms... but why? Postgres 8.3 query planner quirk?  (Bryce Nesbitt, )
  Re: Re: 512,600ms query becomes 7500ms... but why? Postgres 8.3 query planner quirk?  (Pavel Stehule, )
  Re: Re: 512,600ms query becomes 7500ms... but why? Postgres 8.3 query planner quirk?  (Robert Haas, )
   Re: Re: 512,600ms query becomes 7500ms... but why? Postgres 8.3 query planner quirk?  ("Jorge Montero", )
   Re: Re: 512,600ms query becomes 7500ms... but why? Postgres 8.3 query planner quirk?  (Bryce Nesbitt, )
    Re: Re: 512,600ms query becomes 7500ms... but why? Postgres 8.3 query planner quirk?  (Tom Lane, )
     Re: Re: 512,600ms query becomes 7500ms... but why? Postgres 8.3 query planner quirk?  (Bryce Nesbitt, )
     Re: Re: 512,600ms query becomes 7500ms... but why? Postgres 8.3 query planner quirk?  (Bryce Nesbitt, )
    Re: Re: 512,600ms query becomes 7500ms... but why? Postgres 8.3 query planner quirk?  (Robert Haas, )
 Re: 512,600ms query becomes 7500ms... but why? Postgres 8.3 query planner quirk?  ("Kevin Grittner", )
  Re: 512,600ms query becomes 7500ms... but why? Postgres 8.3 query planner quirk?  (Karl Denninger, )
   Re: 512,600ms query becomes 7500ms... but why? Postgres 8.3 query planner quirk?  ("Kevin Grittner", )
    Re: 512,600ms query becomes 7500ms... but why? Postgres 8.3 query planner quirk?  (Karl Denninger, )
     Re: 512,600ms query becomes 7500ms... but why? Postgres 8.3 query planner quirk?  ("Kevin Grittner", )
     Re: 512,600ms query becomes 7500ms... but why? Postgres 8.3 query planner quirk?  (Tom Lane, )
      Re: 512,600ms query becomes 7500ms... but why? Postgres 8.3 query planner quirk?  (Bryce Nesbitt, )
       Re: 512,600ms query becomes 7500ms... but why? Postgres 8.3 query planner quirk?  (Pierre Frédéric Caillaud<>, )
       Re: 512,600ms query becomes 7500ms... but why? Postgres 8.3 query planner quirk?  (Robert Haas, )
  Re: 512,600ms query becomes 7500ms... but why? Postgres 8.3 query planner quirk?  (Bryce Nesbitt, )

Bryce Nesbitt <> 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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