Did you test with ILIKE instead of lower LIKE lower ? -----Original Message----- From: pgsql-performance-owner@xxxxxxxxxxxxxx [mailto:pgsql-performance-owner@xxxxxxxxxxxxxx] On Behalf Of sdfasdfas sdfasdfs Sent: mercredi 24 novembre 2004 18:37 To: pgsql-performance@xxxxxxxxxxxxxx Subject: "Group By " index usage I have a table with this index: create index ARTISTS_NAME on ARTISTS ( lower(AR_NAME) ); Te index is over a colum with this definition: AR_NAME VARCHAR(256) null, I want to optimize this query: select * from artists where lower(ar_name) like lower('a%') order by lower(ar_name) limit 20; I think the planner should use the index i have. But the result of the explain command is: explain analyze select * from artists where lower(ar_name) like lower('a%') order by lower(ar_name) limit 20; QUERY PLAN ---------------------------------------------------------------------------- --------------------------------------------------------------------- Limit (cost=20420.09..20420.14 rows=20 width=360) (actual time=2094.13..2094.19 rows=20 loops=1) -> Sort (cost=20420.09..20433.52 rows=5374 width=360) (actual time=2094.13..2094.16 rows=21 loops=1) Sort Key: lower((ar_name)::text) -> Index Scan using artists_name on artists (cost=0.00..19567.09 rows=5374 width=360) (actual time=0.11..1391.97 rows=59047 loops=1) Index Cond: ((lower((ar_name)::text) >= 'a'::text) AND (lower((ar_name)::text) < 'b'::text)) Filter: (lower((ar_name)::text) ~~ 'a%'::text) Total runtime: 2098.62 msec (7 rows) The "ORDER BY" clause is not using the index!. I don't know why. I have the locale configured to C, and the index works well with the "like" operator. ¿Could you help me? I am really lost. ______________________________________________ Renovamos el Correo Yahoo!: ¡100 MB GRATIS! Nuevos servicios, más seguridad http://correo.yahoo.es ---------------------------(end of broadcast)--------------------------- TIP 8: explain analyze is your friend
