From: Bruce Momjian <pgman@candle.pha.pa.us>
Message-Id: <200206201610.g5KGAm507411@candle.pha.pa.us>
Subject: Re: Which one is faster?
In-Reply-To: <3D11C92E.F05D0E80@Yahoo.com>
To: Jan Wieck <JanWieck@Yahoo.com>
Date: Thu, 20 Jun 2002 12:10:48 -0400 (EDT)
Cc: Wei Weng <wweng@kencast.com>, pgsql-sql@postgresql.org
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Jan Wieck wrote:
> 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.

Oh, I thought the portal had to be materialized before returning a row. 
Thanks.

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