76 lines
5.0 KiB
HTML
76 lines
5.0 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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<meta name="DC.Title" content="Temporary sorted list" />
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<meta name="abstract" content="The temporary sorted list is a temporary object that allows the optimizer to sequence rows based upon a column or set of columns. The sorted list can be either scanned or probed by the optimizer to satisfy different operations of the query." />
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<meta name="description" content="The temporary sorted list is a temporary object that allows the optimizer to sequence rows based upon a column or set of columns. The sorted list can be either scanned or probed by the optimizer to satisfy different operations of the query." />
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<meta name="DC.subject" content="definitions, temporary sorted list access method, temporary sorted list, access method" />
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<meta name="keywords" content="definitions, temporary sorted list access method, temporary sorted list, access method" />
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<meta name="DC.Relation" scheme="URI" content="rzajqtempobj.htm" />
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<meta name="DC.Relation" scheme="URI" content="rzajqslistscan.htm" />
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<meta name="DC.Relation" scheme="URI" content="rzajqslistprobe.htm" />
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<meta name="copyright" content="(C) Copyright IBM Corporation 1998, 2006" />
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<link rel="stylesheet" type="text/css" href="./ic.css" />
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<title>Temporary sorted list</title>
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</head>
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<body id="rzajqtempslist"><a name="rzajqtempslist"><!-- --></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">Temporary sorted list</h1>
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<div><p>The temporary sorted list is a temporary object that allows the
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optimizer to sequence rows based upon a column or set of columns. The sorted
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list can be either scanned or probed by the optimizer to satisfy different
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operations of the query.</p>
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<div class="section"><p>A temporary sorted list is a data structure where the rows are
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organized for quick and easy retrieval after population has occurred. During
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population, the rows are copied into the temporary object and then a second
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pass is made through the temporary object to perform the sort. In order to
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optimize the creation of this temporary object, minimal data movement is performed
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while the sort is processed. It is generally not as efficient to probe a temporary
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sorted list as it is to probe a temporary hash table.</p>
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</div>
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<div class="section"><p>Additionally, the sorted list can be populated with all of the
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necessary columns to satisfy any further processing, avoiding any random I/Os
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associated with a Table Probe operation. However, the optimizer does have
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the ability to selectively include columns in the sorted list when the calculated
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size will exceed the memory pool storage available for this query. In those
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cases, a Table Probe operation is required to recollect the missing columns
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from the sorted list before the selected rows can be processed.</p>
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</div>
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<div class="section"><p>A temporary sorted list is an internal data structure and can
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only be created by the database manager.</p>
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</div>
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<div class="section"><p>Visual explain icon:</p>
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</div>
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<div class="section"><p><img src="rzajq518.gif" alt="Temporary sorted list icon" /></p>
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</div>
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</div>
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<div>
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<ul class="ullinks">
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<li class="ulchildlink"><strong><a href="rzajqslistscan.htm">Sorted list scan</a></strong><br />
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During a sorted list scan operation, the entire temporary sorted list is scanned and all of the entries contained within the sorted list will be processed.</li>
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<li class="ulchildlink"><strong><a href="rzajqslistprobe.htm">Sorted list probe</a></strong><br />
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A sorted list probe operation is used to retrieve rows from a temporary sorted list based upon a probe lookup operation.</li>
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</ul>
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<div class="familylinks">
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<div class="parentlink"><strong>Parent topic:</strong> <a href="rzajqtempobj.htm" title="Temporary objects are created by the optimizer in order to process a query. In general, these temporary objects are internal objects and cannot be accessed by a user.">Temporary objects and access methods</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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