From: Tom Lane <tgl@sss.pgh.pa.us>
To: Yves Vindevogel <yves.vindevogel@implements.be>
Cc: pgsql-performance@postgresql.org
Subject: Re: Limit clause not using index
Date: Tue, 21 Jun 2005 10:42:53 -0400
Message-ID: <3415.1119364973@sss.pgh.pa.us> (raw)
In-Reply-To: <d0da86521cd54473cac40df63bb14546@implements.be>
References: <d0da86521cd54473cac40df63bb14546@implements.be>
Yves Vindevogel <yves.vindevogel@implements.be> writes:
> Can anyone explain me this ?
> rvponp=# explain select * from tblprintjobs order by loginuser,
> desceventdate, desceventtime offset 25 limit 25 ;
> QUERY PLAN
> ------------------------------------------------------------------------
> -----------
> Limit (cost=349860.62..349860.68 rows=25 width=206)
> -> Sort (cost=349860.56..351416.15 rows=622236 width=206)
> Sort Key: loginuser, desceventdate, desceventtime
> -> Seq Scan on tblprintjobs (cost=0.00..25589.36 rows=622236 width=206)
> (4 rows)
Do you have an index matching that sort key? I'd certainly expect the
above to use it if it were there. For the full table case it's not so
clear --- an indexscan isn't always better.
regards, tom lane
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To: pgsql-performance@postgresql.org
Cc: tgl@sss.pgh.pa.us, yves.vindevogel@implements.be
Subject: Re: Limit clause not using index
In-Reply-To: <3415.1119364973@sss.pgh.pa.us>
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