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31 lines
2.1 KiB
HTML
<!--$Id: h_ffactor.so,v 10.11 2000/03/18 21:43:08 bostic Exp $-->
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<!--Copyright 1997, 1998, 1999, 2000 by Sleepycat Software, Inc.-->
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<!--All rights reserved.-->
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<html>
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<head>
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<title>Berkeley DB Reference Guide: Page fill factor</title>
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<meta name="description" content="Berkeley DB: An embedded database programmatic toolkit.">
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<meta name="keywords" content="embedded,database,programmatic,toolkit,b+tree,btree,hash,hashing,transaction,transactions,locking,logging,access method,access methods,java,C,C++">
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</head>
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<body bgcolor=white>
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<a name="2"><!--meow--></a>
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<table><tr valign=top>
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<td><h3><dl><dt>Berkeley DB Reference Guide:<dd>Access Methods</dl></h3></td>
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<td width="1%"><a href="../../ref/am_conf/bt_recnum.html"><img src="../../images/prev.gif" alt="Prev"></a><a href="../../ref/toc.html"><img src="../../images/ref.gif" alt="Ref"></a><a href="../../ref/am_conf/h_hash.html"><img src="../../images/next.gif" alt="Next"></a>
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</td></tr></table>
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<p>
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<h1 align=center>Page fill factor</h1>
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<p>The density, or page fill factor, is an approximation of the number of
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keys allowed to accumulate in any one bucket, determining when the hash
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table grows or shrinks. If you know the average sizes of the keys and
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data in your dataset, setting the fill factor can enhance performance.
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A reasonable rule to use to compute fill factor is:
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<p><blockquote><pre>(pagesize - 32) / (average_key_size + average_data_size + 8)</pre></blockquote>
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<p>The desired density within the hash table can be specified by calling
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the <a href="../../api_c/db_set_h_ffactor.html">DB->set_h_ffactor</a> function. If no density is specified, one will
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be selected dynamically as pages are filled.
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<table><tr><td><br></td><td width="1%"><a href="../../ref/am_conf/bt_recnum.html"><img src="../../images/prev.gif" alt="Prev"></a><a href="../../ref/toc.html"><img src="../../images/ref.gif" alt="Ref"></a><a href="../../ref/am_conf/h_hash.html"><img src="../../images/next.gif" alt="Next"></a>
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</td></tr></table>
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<p><font size=1><a href="http://www.sleepycat.com">Copyright Sleepycat Software</a></font>
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