From: | "Alexander M(dot) Pravking" <fduch(at)antar(dot)bryansk(dot)ru> |
---|---|
To: | Anton <anton200(at)gmail(dot)com> |
Cc: | Sergey Suleymanov <solt(at)eatpbank(dot)ru>, pgsql-ru-general(at)postgresql(dot)org |
Subject: | Re: SELECT ... WHERE ... IN (SELECT ...) -> |
Date: | 2006-12-05 07:37:41 |
Message-ID: | 20061205073741.GB12175@dyatel.antar.bryansk.ru |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-ru-general |
On Tue, 2006-12-05 at 12:01 +0500, Anton wrote:
> > А если таки явно нарисовать join ?
> то ничего не меняется, т.к. оно как раз это вроде бы само-то и делает.
>
> =# explain analyze
> billing-# SELECT n_traffic.collect_time
> billing-# FROM n_logins
> billing-# JOIN n_traffic ON (n_traffic.login_id = n_logins.login_id
> AND
> billing(# n_traffic.collect_time >
> '1970-01-01 00:00:00')
> billing-# WHERE n_logins.account_id = '1655'
> billing-# ORDER BY n_traffic.collect_time, n_traffic.login_id LIMIT 1;
> ---------------------------------------
> Limit (cost=0.00..2029.81 rows=1 width=12) (actual
> time=5473.602..5473.602 rows=0 loops=1)
> -> Nested Loop (cost=0.00..876879.12 rows=432 width=12) (actual
> time=5473.595..5473.595 rows=0 loops=1)
> -> Index Scan using n_traffic_collect_time_login_id on
> n_traffic (cost=0.00..11094.75 rows=273472 width=12) (actual
> time=0.036..1130.476 rows=273486 loops=1)
> Index Cond: (collect_time > '1970-01-01
> 00:00:00'::timestamp without time zone)
IMHO, этот индекс вообще лишний. Можно попробовать снести, и у
оптимизатора не останется ничего другого, кроме как использовать индекс
по login_id.
> -> Index Scan using n_logins_pkey on n_logins
> (cost=0.00..3.15 rows=1 width=4) (actual time=0.011..0.011 rows=0
> loops=273486)
> Index Cond: ("outer".login_id = n_logins.login_id)
> Filter: (account_id = 1655)
> Total runtime: 5473.843 ms
> (8 rows)
--
Fduch M. Pravking
From | Date | Subject | |
---|---|---|---|
Next Message | Sergey Suleymanov | 2006-12-05 07:59:47 | Re: SELECT ... WHERE ... IN (SELECT ...) -> |
Previous Message | Alexander M. Pravking | 2006-12-05 07:34:07 | Re: SELECT ... WHERE ... IN (SELECT ...) -> SELECT ... WHERE (... OR ... ) |