If I have this table, function and index in Postgres 7.3.6 ... """ CREATE TABLE news_stories ( id serial primary key NOT NULL, pub_date timestamp with time zone NOT NULL, ... ) CREATE OR REPLACE FUNCTION get_year_trunc(timestamp with time zone) returns timestamp with time zone AS 'SELECT date_trunc(\'year\',$1);' LANGUAGE 'SQL' IMMUTABLE; CREATE INDEX news_stories_pub_date_year_trunc ON news_stories( get_year_trunc(pub_date) ); """ ...why does this query not use the index? db=# EXPLAIN SELECT DISTINCT get_year_trunc(pub_date) FROM news_stories; QUERY PLAN --------------------------------------------------------------------------------- Unique (cost=59597.31..61311.13 rows=3768 width=8) -> Sort (cost=59597.31..60454.22 rows=342764 width=8) Sort Key: date_trunc('year'::text, pub_date) -> Seq Scan on news_stories (cost=0.00..23390.55 rows=342764 width=8) (4 rows)
The query is noticably slow (2 seconds) on a database with 150,000+ records. How can I speed it up? Thanks, Adrian ---------------------------(end of broadcast)--------------------------- TIP 3: if posting/reading through Usenet, please send an appropriate subscribe-nomail command to [EMAIL PROTECTED] so that your message can get through to the mailing list cleanly