1<!--$Id: db_set_h_nelem.so,v 10.36 2004/09/28 15:04:19 bostic Exp $--> 2<!--Copyright (c) 1997,2008 Oracle. All rights reserved.--> 3<!--See the file LICENSE for redistribution information.--> 4<html> 5<head> 6<title>Berkeley DB: DB->set_h_nelem</title> 7<meta name="description" content="Berkeley DB: An embedded database programmatic toolkit."> 8<meta name="keywords" content="embedded,database,programmatic,toolkit,btree,hash,hashing,transaction,transactions,locking,logging,access method,access methods,Java,C,C++"> 9</head> 10<body bgcolor=white> 11<table width="100%"><tr valign=top> 12<td> 13<b>DB->set_h_nelem</b> 14</td> 15<td align=right> 16<a href="/api_c/api_core.html"><img src="/images/api.gif" alt="API"></a> 17<a href="/ref/toc.html"><img src="/images/ref.gif" alt="Ref"></a></td> 18</tr></table> 19<hr size=1 noshade> 20<tt> 21<b><pre> 22#include <db.h> 23<p> 24int 25DB->set_h_nelem(DB *db, u_int32_t h_nelem); 26<p> 27int 28DB->get_h_nelem(DB *db, u_int32_t *h_nelemp); 29</pre></b> 30<hr size=1 noshade> 31<b>Description: DB->set_h_nelem</b> 32<p>Set an estimate of the final size of the hash table.</p> 33<p>In order for the estimate to be used when creating the database, the 34<a href="/api_c/db_set_h_ffactor.html">DB->set_h_ffactor</a> method must also be called. If the estimate 35or fill factor are not set or are set too low, hash tables will still 36expand gracefully as keys are entered, although a slight performance 37degradation may be noticed.</p> 38<p>The DB->set_h_nelem method configures a database, not only operations performed 39using the specified <a href="/api_c/db_class.html">DB</a> handle.</p> 40<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. 41If the database already exists when 42<a href="/api_c/db_open.html">DB->open</a> is called, the information specified to DB->set_h_nelem will 43be ignored. 44</p> 45<p>The DB->set_h_nelem method 46returns a non-zero error value on failure 47and 0 on success. 48</p> 49<b>Parameters</b> <br> 50 <b>h_nelem</b><ul compact><li>The <b>h_nelem</b> parameter is an estimate of the final size of the 51hash table.</ul> 52<br> 53<br><b>Errors</b> 54<p>The DB->set_h_nelem method 55may fail and return one of the following non-zero errors:</p> 56<br> 57<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 58invalid flag value or parameter was specified.</ul> 59<br> 60<hr size=1 noshade> 61<b>Description: DB->get_h_nelem</b> 62<p>The DB->get_h_nelem method returns the estimate of the final size of the hash table.</p> 63<p>The DB->get_h_nelem method may be called at any time during the life of the 64application.</p> 65<p>The DB->get_h_nelem method 66returns a non-zero error value on failure 67and 0 on success. 68</p> 69<b>Parameters</b> <br> 70 <b>h_nelemp</b><ul compact><li>The DB->get_h_nelem method returns the 71estimate of the final size of the hash table in <b>h_nelemp</b>.</ul> 72<br> 73<hr size=1 noshade> 74<br><b>Class</b> 75<a href="/api_c/db_class.html">DB</a> 76<br><b>See Also</b> 77<a href="/api_c/db_list.html">Databases and Related Methods</a> 78</tt> 79<table width="100%"><tr><td><br></td><td align=right> 80<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> 81</td></tr></table> 82<p><font size=1>Copyright (c) 1996,2008 Oracle. All rights reserved.</font> 83</body> 84</html> 85
