49 lines
3.2 KiB
HTML
49 lines
3.2 KiB
HTML
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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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<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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