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4.6 KiB
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<!--$Id: db_set_h_ffactor.so,v 10.15 2000/05/01 21:57:43 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: Db::set_h_ffactor</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>
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<h1>Db::set_h_ffactor</h1>
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</td>
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<td width="1%">
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<a href="../api_cxx/cxx_index.html"><img src="../images/api.gif" alt="API"></a><a href="../ref/toc.html"><img src="../images/ref.gif" alt="Ref"></a>
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</td></tr></table>
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<hr size=1 noshade>
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<tt>
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<h3><pre>
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#include <db_cxx.h>
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<p>
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int
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Db::set_h_ffactor(u_int32_t h_ffactor);
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</pre></h3>
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<h1>Description</h1>
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<p>Set the desired density within the hash table.
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<p>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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dataset, setting the fill factor can enhance performance. A reasonable
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rule computing fill factor is to set it to:
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<p><blockquote><pre>(pagesize - 32) / (average_key_size + average_data_size + 8)</pre></blockquote>
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<p>If no value is specified, the fill factor will be selected dynamically as
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pages are filled.
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<p>The Db::set_h_ffactor interface may only be used to configure Berkeley DB before
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the <a href="../api_cxx/db_open.html">Db::open</a> interface is called.
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<p>The Db::set_h_ffactor method either returns a non-zero error value or throws an exception that
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encapsulates a non-zero error value on failure, and returns 0 on success.
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<h1>Errors</h1>
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<p><dl compact>
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<p><dt>EINVAL<dd>An invalid flag value or parameter was specified.
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<p>Called after <a href="../api_cxx/db_open.html">Db::open</a> was called.
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</dl>
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<h3>Class</h3>
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<a href="../api_cxx/db_class.html">Db</a>
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<h1>See Also</h1>
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<a href="../api_cxx/db_close.html">Db::close</a>,
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<a href="../api_cxx/db_cursor.html">Db::cursor</a>,
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<a href="../api_cxx/db_del.html">Db::del</a>,
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<a href="../api_cxx/db_err.html">Db::err</a>,
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<a href="../api_cxx/db_fd.html">Db::fd</a>,
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<a href="../api_cxx/db_get.html">Db::get</a>,
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<a href="../api_cxx/db_get_byteswapped.html">Db::get_byteswapped</a>,
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<a href="../api_cxx/db_get_type.html">Db::get_type</a>,
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<a href="../api_cxx/db_join.html">Db::join</a>,
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<a href="../api_cxx/db_key_range.html">Db::key_range</a>,
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<a href="../api_cxx/db_open.html">Db::open</a>,
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<a href="../api_cxx/db_put.html">Db::put</a>,
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<a href="../api_cxx/db_remove.html">Db::remove</a>,
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<a href="../api_cxx/db_set_bt_compare.html">Db::set_bt_compare</a>,
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<a href="../api_cxx/db_set_bt_minkey.html">Db::set_bt_minkey</a>,
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<a href="../api_cxx/db_set_bt_prefix.html">Db::set_bt_prefix</a>,
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<a href="../api_cxx/db_set_cachesize.html">Db::set_cachesize</a>,
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<a href="../api_cxx/db_set_dup_compare.html">Db::set_dup_compare</a>,
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<a href="../api_cxx/db_set_errcall.html">Db::set_errcall</a>,
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<a href="../api_cxx/db_set_errfile.html">Db::set_errfile</a>,
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<a href="../api_cxx/db_set_errpfx.html">Db::set_errpfx</a>,
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<a href="../api_cxx/db_set_flags.html">Db::set_flags</a>,
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<a href="../api_cxx/db_set_h_ffactor.html">Db::set_h_ffactor</a>,
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<a href="../api_cxx/db_set_h_hash.html">Db::set_h_hash</a>,
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<a href="../api_cxx/db_set_h_nelem.html">Db::set_h_nelem</a>,
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<a href="../api_cxx/db_set_lorder.html">Db::set_lorder</a>,
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<a href="../api_cxx/db_set_malloc.html">Db::set_malloc</a>,
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<a href="../api_cxx/db_set_pagesize.html">Db::set_pagesize</a>,
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<a href="../api_cxx/db_set_paniccall.html">Db::set_paniccall</a>,
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<a href="../api_cxx/db_set_q_extentsize.html">Db::set_q_extentsize</a>,
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<a href="../api_cxx/db_set_realloc.html">Db::set_realloc</a>,
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<a href="../api_cxx/db_set_re_delim.html">Db::set_re_delim</a>,
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<a href="../api_cxx/db_set_re_len.html">Db::set_re_len</a>,
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<a href="../api_cxx/db_set_re_pad.html">Db::set_re_pad</a>,
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<a href="../api_cxx/db_set_re_source.html">Db::set_re_source</a>,
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<a href="../api_cxx/db_stat.html">Db::stat</a>,
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<a href="../api_cxx/db_sync.html">Db::sync</a>,
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<a href="../api_cxx/db_upgrade.html">Db::upgrade</a>
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and
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<a href="../api_cxx/db_verify.html">Db::verify</a>.
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</tt>
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<table><tr><td><br></td><td width="1%">
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<a href="../api_cxx/cxx_index.html"><img src="../images/api.gif" alt="API"></a><a href="../ref/toc.html"><img src="../images/ref.gif" alt="Ref"></a>
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