On Fri, 5 Oct 2007, Tom Lane wrote:
Benjamin Arai <benjamin@xxxxxxxxxxxx> writes:# explain analyze select * FROM fulltext_article, to_tsquery ('simple','dog') AS q WHERE idxfti @@ q ORDER BY rank(idxfti, q) DESC;QUERY PLAN ------------------------------------------------------------------------ ------------------------------------------------------------------------ ------------ Sort (cost=6576.74..6579.07 rows=933 width=774) (actual time=12969.237..12970.490 rows=5119 loops=1) Sort Key: rank(fulltext_article.idxfti, q.q) -> Nested Loop (cost=3069.79..6530.71 rows=933 width=774) (actual time=209.513..12955.498 rows=5119 loops=1) -> Function Scan on q (cost=0.00..0.01 rows=1 width=32) (actual time=0.005..0.006 rows=1 loops=1) -> Bitmap Heap Scan on fulltext_article (cost=3069.79..6516.70 rows=933 width=742) (actual time=209.322..234.390 rows=5119 loops=1) Recheck Cond: (fulltext_article.idxfti @@ q.q) -> Bitmap Index Scan on fulltext_article_idxfti_idx (cost=0.00..3069.56 rows=933 width=0) (actual time=208.373..208.373 rows=5119 loops=1) Index Cond: (fulltext_article.idxfti @@ q.q) Total runtime: 12973.035 ms (9 rows)The time seems all spent at the join step, which is odd because it really hasn't got much to do. AFAICS all it has to do is compute the rank() values that the sort step will use. Is it possible that rank() is really slow?
can you try rank_cd() instead ?
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