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

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