PostgreSQL Full Text Search: why search is sooo slow? -


i have small postgresql database (~~3,000 rows).

i'm trying set full text search on 1 of it's text fields ('body').

the problem query extremely slow (35+ seconds!!!).

i suppose problem comes fact db chooses sequential scan mode...

this query:

    select         ts_rank_cd(to_tsvector('italian', body), query),         ts_headline('italian', body, to_tsquery('torino')),         title,         location,         id_author             fulltextsearch.documents, to_tsquery('torino') query             (body_tsvector @@ query)     offset         0

this explain analyze:

                                      query plan                                     ---------------------------------------------------------------------------------------------------------------------------- limit  (cost=0.00..1129.81 rows=19 width=468) (actual time=74.059..13630.114 rows=863 loops=1) ->  nested loop  (cost=0.00..1129.81 rows=19 width=468) (actual time=74.056..13629.342 rows=863 loops=1)      join filter: (documents.body_tsvector @@ query.query)      ->  function scan on to_tsquery query  (cost=0.00..0.01 rows=1 width=32) (actual time=4.606..4.608 rows=1 loops=1)      ->  seq scan on documents  (cost=0.00..1082.09 rows=3809 width=591) (actual time=0.045..48.072 rows=3809 loops=1) total runtime: 13630.720 ms

this table:

mydb=# \d+ fulltextsearch.documents;                                               table "fulltextsearch.documents"     column     |       type        |                               modifiers                               | storage  | description ---------------+-------------------+-----------------------------------------------------------------------+----------+-------------  id            | integer           | not null default nextval('fulltextsearch.documents_id_seq'::regclass) | plain    |  id_author     | integer           |                                                                       | plain    |  body          | character varying |                                                                       | extended |  title         | character varying |                                                                       | extended |  location      | character varying |                                                                       | extended |  date_creation | date              |                                                                       | plain    |  body_tsvector | tsvector          |                                                                       | extended | indexes:     "fulltextsearch_documents_tsvector_idx" gin (to_tsvector('italian'::regconfig,     coalesce(body, ''::character varying)::text))     "id_idx" btree (id) triggers:     body_tsvectorupdate before insert or update on fulltextsearch.documents each row execute procedure tsvector_update_trigger('body_tsvector', 'pg_catalog.italian', 'body') has oids: no

i'm sure i'm missing obvious....

any clues?

.

.

.

=== update =======================================================================

thanks suggestions, came (better) query:

select     ts_rank(body_tsvector, query),     ts_headline('italian', body, query),     title,     location     fulltextsearch.documents, to_tsquery('italian', 'torino') query     to_tsvector('italian', coalesce(body,'')) @@ query

which quite better, slow (13+ seconds...).

i notice commenting out "ts_headline()" row query lightning-fast.

this explain analyze, uses index, doesn't me much...:

explain analyze select clock_timestamp() - statement_timestamp() elapsed_time,     ts_rank(body_tsvector, query),     ts_headline('italian', body, query),     title,     location     fulltextsearch.documents, to_tsquery('italian', 'torino') query     to_tsvector('italian', coalesce(body,'')) @@ query   nested loop  (cost=16.15..85.04 rows=19 width=605) (actual time=102.290..13392.161 rows=863 loops=1)    ->  function scan on query  (cost=0.00..0.01 rows=1 width=32) (actual time=0.008..0.009 rows=1 loops=1)    ->  bitmap heap scan on documents  (cost=16.15..84.65 rows=19 width=573) (actual time=0.381..4.236 rows=863 loops=1)          recheck cond: (to_tsvector('italian'::regconfig, (coalesce(body, ''::character varying))::text) @@ query.query)          ->  bitmap index scan on fulltextsearch_documents_tsvector_idx  (cost=0.00..16.15 rows=19 width=0) (actual time=0.312..0.312 rows=863 loops=1)                index cond: (to_tsvector('italian'::regconfig, (coalesce(body, ''::character varying))::text) @@ query.query)  total runtime: 13392.717 ms

you're missing 2 (reasonably obvious) things:

1 you've set 'italian' in to_tsvector() aren't specifying in to_tsquery()

keep both consistent.

2 you've indexed coalesce(body, ...) isn't you're searching against.

the planner isn't magic - can use index if that's you're searching against.


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