Re: Optimizing query

Do something like:

CREATE OR REPLACE FUNCTION my_date_part( timestamp) RETURNS DOUBLE precision AS '
DECLARE
mydate ALIAS FOR $1;
BEGIN
return date_part( ''day'', mydate );
END;' LANGUAGE 'plpgsql' IMMUTABLE;

create index idx_tmp on stat_views( my_date_part( created ) );

or add an extra date_part column to your table which pre-calculates date_part('day', created) and put an index on this.

Cheers
Matthew
--

----- Original Message -----
From: Uros
To: pgsql-general(at)postgresql(dot)org
Sent: Wednesday, November 19, 2003 10:41 AM
Subject: [GENERAL] Optimizing query

Hello!

I have some trouble getting good results from my query.

here is structure

stat_views
id | integer
id_zone | integer
created | timestamp

I have btree index on created and also id and there is 1633832 records in
that table

First of all I have to manualy set seq_scan to OFF because I always get
seq_scan. When i set it to off my explain show:

explain SELECT count(*) as views FROM stat_views WHERE id = 12;
QUERY PLAN
----------------------------------------------------------------------------------------------------
Aggregate (cost=122734.86..122734.86 rows=1 width=0)
-> Index Scan using stat_views_id_idx on stat_views (cost=0.00..122632.60 rows=40904 width=0)
Index Cond: (id = 12)

But what I need is to count views for some day, so I use

explain SELECT count(*) as views FROM stat_views WHERE date_part('day', created) = 18;

QUERY PLAN
------------------------------------------------------------------------------------
Aggregate (cost=100101618.08..100101618.08 rows=1 width=0)
-> Seq Scan on stat_views (cost=100000000.00..100101565.62 rows=20984 width=0)
Filter: (date_part('day'::text, created) = 18::double precision)

How can I make this to use index and speed the query. Now it takes about 12
seconds.

--
Best regards,
Uros mailto:uros(at)sir-mag(dot)com

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