From: Jan Wieck <JanWieck@Yahoo.com>
To: Bruce Momjian <pgman@candle.pha.pa.us>
Cc: Wei Weng <wweng@kencast.com>
Cc: pgsql-sql@postgresql.org
Subject: Re: Which one is faster?
Date: Thu, 20 Jun 2002 08:23:10 -0400
Message-ID: <3D11C92E.F05D0E80@Yahoo.com> (raw)
References: <200206192034.g5JKYn616099@candle.pha.pa.us>
Bruce Momjian wrote:
>
> Wei Weng wrote:
> > Between Using Limit P, S or using a cursor to start from FETCH ABSOLUTE
> > S and FETCH NEXT for P times, which one is faster?
>
> LIMIT is faster because it doesn't need to generate all the result, in
> some cases.
Neither does using a cursor need to generate all the results first. It's
a portal, which is an executor state on hold, and FETCH is implemented
as ExecutorRun() with the number of wanted result rows as limitation.
Since LIMIT generates internally one more result row than really wanted,
I don't think LIMIT would be much faster, but it's for sure less
portable.
Jan
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To: pgsql-sql@postgresql.org
Cc: JanWieck@Yahoo.com, pgman@candle.pha.pa.us, wweng@kencast.com
Subject: Re: Which one is faster?
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