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Re: Too slow querying a table of 15 million records

From: Tobias Brox <tobias(at)nordicbet(dot)com>
To: kjelle(at)bingon(dot)no
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: Too slow querying a table of 15 million records
Date: 2005-06-28 06:03:33
Message-ID: 20050628060333.GH7652@tobias.exoweb.net (view raw or flat)
Thread:
Lists: pgsql-performance
[kjelle(at)bingon(dot)no - Tue at 08:33:58PM +0200]
> I use FreeBSD 4.11 with PostGreSQL 7.3.8.
(...)
> database=> explain select date_trunc('hour', time),count(*) as total from
> test where p1=53 and time > now() - interval '24 hours' group by
> date_trunc order by date_trunc ;

I haven't looked through all your email yet, but this phenomena have been up
at the list a couple of times.  Try replacing "now() - interval '24 hours'"
with a fixed time stamp, and see if it helps.

pg7 will plan the query without knowledge of what "now() - interval '24
hours'" will compute to.  This should be fixed in pg8.

-- 
Tobias Brox, +86-13521622905
Nordicbet, IT dept

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