2011-09-13 17:44:24 +00:00
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<title>DB->set_h_ffactor()</title>
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<p>Library Version 11.2.5.2</p>
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<table width="100%" summary="Navigation header">
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<th colspan="3" align="center">DB->set_h_ffactor()</th>
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</tr>
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<tr>
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<td width="20%" align="left"><a accesskey="p" href="dbset_h_compare.html">Prev</a> </td>
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<th width="60%" align="center">Chapter 2.
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The DB Handle
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</th>
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<td width="20%" align="right"> <a accesskey="n" href="dbset_h_hash.html">Next</a></td>
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<div class="titlepage">
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<div>
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<h2 class="title" style="clear: both"><a id="dbset_h_ffactor"></a>DB->set_h_ffactor()</h2>
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</div>
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</div>
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</div>
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<pre class="programlisting">#include <db.h>
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int
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DB->set_h_ffactor(DB *db, u_int32_t h_ffactor); </pre>
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<p>
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Set the desired density within the hash table. If no value is
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specified, the fill factor will be selected dynamically as pages
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are filled.
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</p>
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<p>
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The density is an approximation of the number of keys allowed to
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accumulate in any one bucket, determining when the hash table grows or
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shrinks. If you know the average sizes of the keys and data in your
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data set, setting the fill factor can enhance performance. A reasonable
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rule computing fill factor is to set it to the following:
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</p>
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<pre class="programlisting"> (pagesize - 32) / (average_key_size + average_data_size + 8) </pre>
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<p>
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The <code class="methodname">DB->set_h_ffactor()</code> method configures a database, not only
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operations performed using the specified
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<a class="link" href="db.html" title="Chapter 2. The DB Handle">DB</a> handle.
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</p>
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<p>
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The <code class="methodname">DB->set_h_ffactor()</code> method may not be called after the
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<a class="xref" href="dbopen.html" title="DB->open()">DB->open()</a> method is called. If
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the database already exists when <a class="xref" href="dbopen.html" title="DB->open()">DB->open()</a>
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is called, the information specified to <code class="methodname">DB->set_h_ffactor()</code> will be ignored.
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</p>
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<p>
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The <code class="methodname">DB->set_h_ffactor()</code> <span>
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<span>
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method returns a non-zero error value on failure and 0 on success.
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</span>
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</span>
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</p>
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<div class="sect2" lang="en" xml:lang="en">
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<div class="titlepage">
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<div>
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<div>
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2011-12-20 00:07:10 +00:00
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<h3 class="title"><a id="id3688351"></a>Parameters</h3>
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2011-09-13 17:44:24 +00:00
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</div>
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</div>
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</div>
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<div class="sect3" lang="en" xml:lang="en">
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<div class="titlepage">
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<div>
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<div>
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2011-12-20 00:07:10 +00:00
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<h4 class="title"><a id="id3689761"></a>h_ffactor</h4>
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2011-09-13 17:44:24 +00:00
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</div>
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</div>
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</div>
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<p>
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The <span class="bold"><strong>h_ffactor</strong></span> parameter is the
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desired density within the hash table.
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</p>
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</div>
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</div>
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<div class="sect2" lang="en" xml:lang="en">
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<div class="titlepage">
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<div>
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<div>
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2011-12-20 00:07:10 +00:00
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<h3 class="title"><a id="id3689755"></a>Errors</h3>
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2011-09-13 17:44:24 +00:00
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</div>
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</div>
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</div>
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<p>
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The <code class="methodname">DB->set_h_ffactor()</code> <span>
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<span>
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method may fail and return one of the following non-zero errors:
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</span>
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</span>
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</p>
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<div class="sect3" lang="en" xml:lang="en">
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<div class="titlepage">
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<div>
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<div>
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2011-12-20 00:07:10 +00:00
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<h4 class="title"><a id="id3689892"></a>EINVAL</h4>
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2011-09-13 17:44:24 +00:00
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</div>
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</div>
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</div>
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<p>
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If the method was called after <a class="xref" href="dbopen.html" title="DB->open()">DB->open()</a>
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was called; or if an invalid flag value or parameter was specified.
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</p>
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</div>
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</div>
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<div class="sect2" lang="en" xml:lang="en">
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<div class="titlepage">
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<div>
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<div>
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2011-12-20 00:07:10 +00:00
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<h3 class="title"><a id="id3689874"></a>Class</h3>
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2011-09-13 17:44:24 +00:00
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</div>
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</div>
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</div>
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<p>
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<a class="link" href="db.html" title="Chapter 2. The DB Handle">DB</a>
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</p>
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</div>
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<div class="sect2" lang="en" xml:lang="en">
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<div class="titlepage">
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<div>
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<div>
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2011-12-20 00:07:10 +00:00
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<h3 class="title"><a id="id3689929"></a>See Also</h3>
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2011-09-13 17:44:24 +00:00
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</div>
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</div>
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</div>
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<p>
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<a class="xref" href="db.html#dblist" title="Database and Related Methods">Database and Related Methods</a>
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</p>
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<td width="40%" align="left" valign="top">DB->set_h_compare() </td>
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<td width="40%" align="right" valign="top"> DB->set_h_hash()</td>
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