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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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<pre class="programlisting">#include <db_cxx.h>
int
Db::set_h_ffactor(u_int32_t h_ffactor); </pre>
<p>
Set the desired density within the hash table. If no value is
specified, the fill factor will be selected dynamically as pages
are filled.
</p>
<p>
The density is an approximation of the number of keys allowed to
accumulate in any one bucket, determining when the hash table grows or
shrinks. If you know the average sizes of the keys and data in your
data set, setting the fill factor can enhance performance. A reasonable
rule computing fill factor is to set it to the following:
</p>
<pre class="programlisting"> (pagesize - 32) / (average_key_size + average_data_size + 8) </pre>
<p>
The <code class="methodname">Db::set_h_ffactor()</code> method configures a database, not only
operations performed using the specified
<a class="link" href="db.html" title="Chapter 2. The Db Handle">Db</a> handle.
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<p>
The <code class="methodname">Db::set_h_ffactor()</code> method may not be called after the
<a class="xref" href="dbopen.html" title="Db::open()">Db::open()</a> method is called. If
the database already exists when <a class="xref" href="dbopen.html" title="Db::open()">Db::open()</a>
is called, the information specified to <code class="methodname">Db::set_h_ffactor()</code> will be ignored.
</p>
<p>
The <code class="methodname">Db::set_h_ffactor()</code> <span>
<span>
method either returns a non-zero error value or throws an
exception that encapsulates a non-zero error value on
failure, and returns 0 on success.
</span>
</span>
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<h3 class="title"><a id="id1648404"></a>Parameters</h3>
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<h4 class="title"><a id="id1648523"></a>h_ffactor</h4>
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<p>
The <span class="bold"><strong>h_ffactor</strong></span> parameter is the
desired density within the hash table.
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<h3 class="title"><a id="id1648619"></a>Errors</h3>
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<p>
The <code class="methodname">Db::set_h_ffactor()</code> <span>
<span>
method may fail and throw a <a class="link" href="dbexception.html" title="Chapter 6. The DbException Class">DbException</a>
exception, encapsulating one of the following non-zero errors, or return one
of the following non-zero errors:
</span>
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<h4 class="title"><a id="id1648473"></a>EINVAL</h4>
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If the method was called after <a class="xref" href="dbopen.html" title="Db::open()">Db::open()</a>
was called; or if an invalid flag value or parameter was specified.
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<h3 class="title"><a id="id1648423"></a>Class</h3>
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<a class="link" href="db.html" title="Chapter 2. The Db Handle">Db</a>
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<h3 class="title"><a id="id1648399"></a>See Also</h3>
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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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