Horton

Re: 2 Selects 1 is faster, why?

Masaru Sugawara <rk73@sea.plala.or.jp>

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From: Masaru Sugawara <rk73@sea.plala.or.jp>
To: Alvar Freude <alvar@a-blast.org>
Cc: pgsql-sql@postgresql.org
Date: 2002-06-27T15:04:07Z
Lists: pgsql-sql 
On Wed, 26 Jun 2002 17:34:47 +0200
Alvar Freude <alvar@a-blast.org> wrote:


> Hi,
> 
> -- Eric <emayo@pozicom.net> wrote:
> 
> > If I perform the following 2 selects, the first one is EXTREMELY slow
> > where the 2nd one is very fast.
> 
> [...] 
> 
> > Why would 2 be so much faster?  I have ran the EXPLAIN on this and index
> > scans are being used.
> 
> I guess, the first query has to search for all ol.orderid the equivalent
> o.orderid; the second variant only has to search for '1234' in each
> ?.orderid, which is much faster.


 You are right. And this type of optimising are not yet implemented.
 Tom said it in the prior discussions. 



Regards,
Masaru Sugawara