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Date: Thu, 22 Dec 2005 14:06:20 +0000 (GMT)
From: Carlos Benkendorf <carlosbenkendorf@yahoo.com.br>
Subject: Re: ORDER BY costs 
To: Tom Lane <tgl@sss.pgh.pa.us>, pgsql-performance@postgresql.org
In-Reply-To: <15455.1135193975@sss.pgh.pa.us>
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I´m not sure but I think the extra runtime of the select statement that has the ORDER BY clause is because the planner decided to sort the result set.
   
  Is the sort really necessary? Why not only scanning the primary key index pages and retrieving the rows like the select without the order by clause?
   
  Aren´t not the rows retrieved from the index in a odered form?
   
  Thanks in advance!
   
  Benkendorf
   
   
   

		
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<DIV id=RTEContent>I´m not sure but I think the extra runtime of the select statement that has the ORDER BY clause is because the planner decided to sort the result set.</DIV>  <DIV>&nbsp;</DIV>  <DIV>Is the sort&nbsp;really necessary? Why not only scanning the primary key&nbsp;index pages and retrieving the rows like the select without the order by clause?</DIV>  <DIV>&nbsp;</DIV>  <DIV>Aren´t not the rows retrieved from the index in a odered form?</DIV>  <DIV>&nbsp;</DIV>  <DIV>Thanks in advance!</DIV>  <DIV>&nbsp;</DIV>  <DIV>Benkendorf</DIV>  <DIV>&nbsp;</DIV>  <DIV>&nbsp;</DIV>  <DIV>&nbsp;</DIV><p>
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