strange query plan
От | Mario Weilguni |
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Тема | strange query plan |
Дата | |
Msg-id | 01040810350000.00637@wotan обсуждение исходный текст |
Ответы |
Re: strange query plan
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Список | pgsql-general |
I've a table containing some sort of logs, the table layout ist: Attribute | Type | Modifier -----------+--------------------------+--------------------------------------- id | integer | not null default nextval('ids'::text) serverid | integer | not null ts | timestamp with time zone | default now() log | character varying(400) | not null Indices: i1, log_pkey primary key is id, and there is an additional index on serverid. The table contains ~ 1.4 mio of rows, I've used "vacuum analyze". Now when I type: explain select min(id)from log; NOTICE: QUERY PLAN: Aggregate (cost=45702.20..45702.20 rows=1 width=4) -> Seq Scan on log (cost=0.00..41978.36 rows=1489536 width=4) I don't understand why the index log_pkey is not used here. I guess it would be much cheaper to consult the index to get min(), max(), sum() and avg() instead of sequentially scanning ~500MB of data. Any idea? Thanks Best regards, Mario Weilguni -- =================================================== Mario Weilguni KPNQwest Austria GmbH Senior Engineer Web Solutions Nikolaiplatz 4 tel: +43-316-813824 8020 graz, austria fax: +43-316-813824-26 http://www.kpnqwest.at e-mail: mario.weilguni@kpnqwest.com ===================================================
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