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	Fri, 28 Apr 2006 04:30:59 PDT
Date: Fri, 28 Apr 2006 04:30:59 -0700 (PDT)
From: gulsah <gulsah_129@yahoo.com>
Subject: query performance question
To: pgsql-performance@postgresql.org
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Hi,
 
 I have a performance problem with Postgresql version 8.1 installed on a Fedora Core release 4 (Stentz) with kernel version 2.6.11.
 
 The machine I am working on has 512MB of RAM and Pentium III 800 MHz CPU.
 
 I have only one table in the database which consists of 256 columns and 10000 rows. Each column is of float type and each row corresponds to a vector in my application. What I want to do is to compute the distance between a predefined vector in hand and the ones in the database.
 
 The computation proceeds according to the following pseudocode:
 
         for(i=1; i<=256 ; i++){
                 distance += abs(x1_i - x2_i);
         }
 
 where x1_i denotes the vector in hand's i coordinate and x2_i denotes the i
 coordinate of the vector in the database.
 
 The distance computation have to be done for all the vectors in the database
 by means of a query and the result set should be sorted in terms of the
 computed distances.
 
 When I implement the query and measure the time spent for it in an application
 I see that the query is handled in more than 8 seconds which is undesirable in
 my application.
 
 Here what I want to ask you all is that, is it a normal performance for a
 computer with the properties that I have mentioned above? Is there any solution
 in your mind to increase the performance of my query?
 
 To make it more undestandable, I should give the query for vectors with size
 3, but in my case their size is 256.
 
 select
 id as vectorid,
 abs(40.9546-x2_1)+abs(-72.9964-x2_2)+abs(53.5348-x2_3) as distance
 from vectordb
 order by distance
 
 Thank you all for your help.
 
 
 -
 gulsah
 
		
---------------------------------
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Hi,<br> <br> I have a performance problem with Postgresql version 8.1 installed on a Fedora Core release 4 (Stentz) with kernel version 2.6.11.<br> <br> The machine I am working on has 512MB of RAM and Pentium III 800 MHz CPU.<br> <br> I have only one table in the database which consists of 256 columns and 10000 rows. Each column is of float type and each row corresponds to a vector in my application. What I want to do is to compute the distance between a predefined vector in hand and the ones in the database.<br> <br> The computation proceeds according to the following pseudocode:<br> <br> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; for(i=1; i&lt;=256 ; i++){<br> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; distance += abs(x1_i - x2_i);<br> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; }<br> <br> where x1_i denotes the vector in hand's i coordinate and x2_i denotes the i<br> coordinate of the vector in the database.<br> <br> The
 distance computation have to be done for all the vectors in the database<br> by means of a query and the result set should be sorted in terms of the<br> computed distances.<br> <br> When I implement the query and measure the time spent for it in an application<br> I see that the query is handled in more than 8 seconds which is undesirable in<br> my application.<br> <br> Here what I want to ask you all is that, is it a normal performance for a<br> computer with the properties that I have mentioned above? Is there any solution<br> in your mind to increase the performance of my query?<br> <br> To make it more undestandable, I should give the query for vectors with size<br> 3, but in my case their size is 256.<br> <br> select<br> id as vectorid,<br> abs(40.9546-x2_1)+abs(-72.9964-x2_2)+abs(53.5348-x2_3) as distance<br> from vectordb<br> order by distance<br> <br> Thank you all for your help.<br> <br> <br> -<br> gulsah<br> <p>
		<hr size=1>Talk is cheap. Use Yahoo! Messenger to make PC-to-Phone calls. <a href="http://us.rd.yahoo.com/mail_us/taglines/postman7/*http://us.rd.yahoo.com/evt=39666/*http://messenger.yahoo.com"> Great rates starting at 1&cent;/min.
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