From: Pedro Jiménez <p.jimenez@ismsolar.com>
To: pgsql-performance@postgresql.org
Subject: limit order by performance issue
Date: Mon, 15 Oct 2012 19:44:46 +0200
Message-ID: <507C4B8E.3010806@ismsolar.com> (raw)
Hello,
I'm trying to do a simple SQL query over Postgresl 9.0 running on Ubuntu.
I have a large table (over 100 million records) with three fields,
id_signal (bigint), time_stamp (timestamp) and var_value (float).
My query looks like this:
select var_value from ism_floatvalues where id_signal = 29660 order by
time_stamp desc limit 1;
So I want to select the last value from a determinated ID (is_signal).
This query runs FOREVER, while if I delete "limit 1" it runs instantly....
Any help?
Regards.
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To: pgsql-performance@postgresql.org
Cc: p.jimenez@ismsolar.com
Subject: Re: limit order by performance issue
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