85 lines
3.4 KiB
HTML
85 lines
3.4 KiB
HTML
<!--$Id: db_set_h_nelem.html 63573 2008-05-23 21:43:21Z trent.nelson $-->
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<!--Copyright (c) 1997,2008 Oracle. All rights reserved.-->
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<!--See the file LICENSE for redistribution information.-->
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<html>
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<head>
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<title>Berkeley DB: DB->set_h_nelem</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,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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<table width="100%"><tr valign=top>
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<td>
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<b>DB->set_h_nelem</b>
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</td>
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<td align=right>
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<a href="../api_c/api_core.html"><img src="../images/api.gif" alt="API"></a>
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<a href="../ref/toc.html"><img src="../images/ref.gif" alt="Ref"></a></td>
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</tr></table>
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<hr size=1 noshade>
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<tt>
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<b><pre>
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#include <db.h>
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<p>
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int
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DB->set_h_nelem(DB *db, u_int32_t h_nelem);
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<p>
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int
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DB->get_h_nelem(DB *db, u_int32_t *h_nelemp);
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</pre></b>
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<hr size=1 noshade>
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<b>Description: DB->set_h_nelem</b>
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<p>Set an estimate of the final size of the hash table.</p>
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<p>In order for the estimate to be used when creating the database, the
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<a href="../api_c/db_set_h_ffactor.html">DB->set_h_ffactor</a> method must also be called. If the estimate
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or fill factor are not set or are set too low, hash tables will still
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expand gracefully as keys are entered, although a slight performance
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degradation may be noticed.</p>
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<p>The DB->set_h_nelem method configures a database, not only operations performed
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using the specified <a href="../api_c/db_class.html">DB</a> handle.</p>
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<p>The DB->set_h_nelem method may not be called after the <a href="../api_c/db_open.html">DB->open</a> method is called.
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If the database already exists when
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<a href="../api_c/db_open.html">DB->open</a> is called, the information specified to DB->set_h_nelem will
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be ignored.
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</p>
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<p>The DB->set_h_nelem method
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returns a non-zero error value on failure
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and 0 on success.
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</p>
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<b>Parameters</b> <br>
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<b>h_nelem</b><ul compact><li>The <b>h_nelem</b> parameter is an estimate of the final size of the
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hash table.</ul>
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<br>
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<br><b>Errors</b>
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<p>The DB->set_h_nelem method
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may fail and return one of the following non-zero errors:</p>
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<br>
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<b>EINVAL</b><ul compact><li>If the method was called after <a href="../api_c/db_open.html">DB->open</a> was called; or if an
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invalid flag value or parameter was specified.</ul>
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<br>
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<hr size=1 noshade>
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<b>Description: DB->get_h_nelem</b>
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<p>The DB->get_h_nelem method returns the estimate of the final size of the hash table.</p>
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<p>The DB->get_h_nelem method may be called at any time during the life of the
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application.</p>
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<p>The DB->get_h_nelem method
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returns a non-zero error value on failure
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and 0 on success.
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</p>
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<b>Parameters</b> <br>
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<b>h_nelemp</b><ul compact><li>The DB->get_h_nelem method returns the
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estimate of the final size of the hash table in <b>h_nelemp</b>.</ul>
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<br>
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<hr size=1 noshade>
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<br><b>Class</b>
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<a href="../api_c/db_class.html">DB</a>
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<br><b>See Also</b>
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<a href="../api_c/db_list.html">Databases and Related Methods</a>
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</tt>
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<table width="100%"><tr><td><br></td><td align=right>
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<a href="../api_c/api_core.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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<p><font size=1>Copyright (c) 1996,2008 Oracle. All rights reserved.</font>
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</body>
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</html>
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