SELECT DISTINCT(user_id) FROM blocks JOIN seen_its USING (user_id) WHERE seen_its.created BETWEEN (now()::date - interval '8 days')::timestamp AND now()::date::timestamp
to
SELECT DISTINCT(user_id) FROM seen_its WHERE created BETWEEN (now()::date - interval '8 days')::timestamp AND now()::date::timestamp
the difference is 100x.
Here are my tables:
CREATE TABLE seen_its (
user_id character(24) NOT NULL,
moment_id character(24) NOT NULL,
created timestamp without time zone,
inserted timestamp without time zone DEFAULT now(),
CONSTRAINT seen_its_pkey PRIMARY KEY (user_id , moment_id )
) WITH ( OIDS=FALSE );
CREATE INDEX seen_its_created_idx ON seen_its USING btree (created );
CREATE INDEX seen_its_user_id_idx ON seen_its USING btree (user_id );
CREATE TABLE blocks (
block_id character(24) NOT NULL,
user_id character(24) NOT NULL,
created timestamp with time zone,
locale character varying,
shared boolean,
private boolean,
moment_type character varying NOT NULL,
user_agent character varying,
inserted timestamp without time zone NOT NULL DEFAULT now(),
networks character varying[],
lnglat point,
timezone character varying,
geohash character varying(20),
CONSTRAINT blocks_pkey PRIMARY KEY (block_id )
) WITH ( OIDS=FALSE );
CREATE INDEX blocks_created_at_timezone_idx ON blocks USING btree (timezone(timezone::text, created) );
CREATE INDEX blocks_created_idx ON blocks USING btree (created DESC NULLS LAST);
CREATE INDEX blocks_geohash_idx ON blocks USING btree (geohash );
CREATE INDEX blocks_timezone_idx ON blocks USING btree (timezone );
CREATE INDEX blocks_user_id_idx ON blocks USING btree (user_id );
My blocks table has about 17M rows in it. My seen_its table has 1.9M rows in it (though that is expected to grow into the billions).
Here is the EXPLAIN: http://explain.depesz.com/s/ley
I'm using PostgreSQL 9.0.6 on i486-pc-linux-gnu, compiled by GCC gcc-4.4.real (Ubuntu 4.4.3-4ubuntu5) 4.4.3, 32-bit
My random_page_cost is 2 and yet it still insists on using Seq Scan on blocks.
Whenever I use my blocks table, this seems to happen. I'm not sure what's wrong.
Any help would be much appreciated.
Thank you,
-Alessandro
