49 lines
3.2 KiB
HTML
49 lines
3.2 KiB
HTML
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<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE html
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PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<html lang="en-us" xml:lang="en-us">
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
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<meta name="security" content="public" />
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<meta name="Robots" content="index,follow" />
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<meta http-equiv="PICS-Label" content='(PICS-1.1 "http://www.icra.org/ratingsv02.html" l gen true r (cz 1 lz 1 nz 1 oz 1 vz 1) "http://www.rsac.org/ratingsv01.html" l gen true r (n 0 s 0 v 0 l 0) "http://www.classify.org/safesurf/" l gen true r (SS~~000 1))' />
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<meta name="DC.Type" content="concept" />
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<meta name="DC.Title" content="Partitioning keys over join fields with DB2 Multisystem" />
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<meta name="abstract" content="From the preceding sections on the types of joins, you can see that data movement is required for all distributed join types except a collocated join." />
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<meta name="description" content="From the preceding sections on the types of joins, you can see that data movement is required for all distributed join types except a collocated join." />
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<meta name="DC.subject" content="partitioning key, over join fields, join field, over partitioning keys" />
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<meta name="keywords" content="partitioning key, over join fields, join field, over partitioning keys" />
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<meta name="DC.Relation" scheme="URI" content="joinopt.htm" />
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<meta name="copyright" content="(C) Copyright IBM Corporation 1998, 2006" />
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<meta name="DC.Rights.Owner" content="(C) Copyright IBM Corporation 1998, 2006" />
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<meta name="DC.Format" content="XHTML" />
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<meta name="DC.Identifier" content="partkeysjoin" />
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<meta name="DC.Language" content="en-us" />
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<!-- All rights reserved. Licensed Materials Property of IBM -->
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<!-- Use, duplication or disclosure restricted by -->
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<!-- GSA ADP Schedule Contract with IBM Corp. -->
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<link rel="stylesheet" type="text/css" href="./ibmdita.css" />
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<link rel="stylesheet" type="text/css" href="./ic.css" />
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<title>Partitioning keys over join fields with DB2 Multisystem</title>
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</head>
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<body id="partkeysjoin"><a name="partkeysjoin"><!-- --></a>
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<!-- Java sync-link --><script language="Javascript" src="../rzahg/synch.js" type="text/javascript"></script>
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<h1 class="topictitle1">Partitioning keys over join fields with DB2<sup>®</sup> Multisystem</h1>
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<div><p>From the preceding sections on the types of joins, you can see
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that data movement is required for all distributed join types except a collocated
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join.</p>
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<p>To eliminate the need for data movement and to maximize performance, all
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queries should be written so that a collocated join is possible. In other
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words, the partitioning keys of the distributed files should match the fields
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used to join the files together. For queries that are run frequently, it is
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more important to have the partitioning keys match the join fields than it
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is to match the ordering or the grouping criteria.</p>
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</div>
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<div>
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<div class="familylinks">
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<div class="parentlink"><strong>Parent topic:</strong> <a href="joinopt.htm" title="The distributed query optimizer generates a plan to join distributed files.">Join optimization with DB2 Multisystem</a></div>
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</div>
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</div>
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</body>
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</html>
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