From: Mario Weilguni <mweilguni@sime.com>
To: pgsql-general@postgresql.org
Subject: strange query plan
Date: Sun, 8 Apr 2001 10:35:00 +0200
Message-ID: <01040810350000.00637@wotan> (raw)
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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Cc: mweilguni@sime.com, pgsql-general@postgresql.org
Subject: Re: strange query plan
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