RE: [GENERAL] Optimal indicies

try:
EXPLAIN SELECT pos_id, rating
 FROM pos_rating pr
 WHERE date_i = current_date AND city_id = 2  AND 
 EXISTS (SELECT DISTINCT pos_id FROM positions p WHERE subsec_id = 1 AND
status = 'A' AND pr.pos_id=p.pos_id)
ORDER BY rating;

Index date_i and city_id only.
	-DEJ

> -----Original Message-----
> From:	Oleg Broytmann [SMTP:phd@sun.med.ru]
> Sent:	Friday, April 16, 1999 8:05 AM
> To:	PostgreSQL
> Subject:	[GENERAL] Optimal indicies
> 
> Hello!
> 
>    It is definitely FAQ, but I haven't found an answer in docs or mailing
> list.
>    How do I create indicies? (No, no, I know CREATE INDEX syntax :) But
> how
> do I plan my indicies that optimizer will use? I expected a topic in
> postgres guides, but there is no one. Any general advice?
> 
>    For example, here is a table (I am not showing here other tables, I
> think they are not important):
> 
> -- Position's rating for today for every city
> CREATE TABLE pos_rating (
>    pos_id int4 not null references positions (pos_id),
>    date_i date default current_date,
>    city_id int2 not null references cities (city_id),
>    rating float default 5 check (rating >= 1 and rating <= 10),
>    primary key (pos_id, date_i, city_id)
> );
> 
>    Currently, there is only one index for primary key.
> 
>    And here is a query cost. Index is not used. What index I need to add?
> Do I need to rewrite queries (using EXIST instaed of IN, as it once
> suggested)?
> 
> EXPLAIN SELECT pos_id, rating FROM pos_rating
>    WHERE pos_id IN
>       (SELECT pos_id FROM positions WHERE subsec_id = 1 AND status = 'A')
>    AND date_i = current_date AND city_id = 2
> ORDER BY rating ;
> 
> NOTICE:  QUERY PLAN:
> 
> Sort  (cost=236.43 size=0 width=0)
>   ->  Seq Scan on pos_rating  (cost=236.43 size=5 width=12)
>         SubPlan
>           ->  Seq Scan on positions  (cost=3.11 size=3 width=4)
> 
> Oleg.
> ---- 
>     Oleg Broytmann     http://members.xoom.com/phd2/
> phd2@earthling.net
>            Programmers don't die, they just GOSUB without RETURN.
> 
>