<!--$Id: db_key_range.html,v 1.1 2003/02/15 04:55:50 zarzycki Exp $--> <!--Copyright 1997-2002 by Sleepycat Software, Inc.--> <!--All rights reserved.--> <!--See the file LICENSE for redistribution information.--> <html> <head> <title>Berkeley DB: Db.key_range</title> <meta name="description" content="Berkeley DB: An embedded database programmatic toolkit."> <meta name="keywords" content="embedded,database,programmatic,toolkit,b+tree,btree,hash,hashing,transaction,transactions,locking,logging,access method,access methods,java,C,C++"> </head> <body bgcolor=white> <a name="2"><!--meow--></a> <table width="100%"><tr valign=top> <td> <h1>Db.key_range</h1> </td> <td align=right> <a href="../api_java/c_index.html"><img src="../images/api.gif" alt="API"></a><a href="../reftoc.html"><img src="../images/ref.gif" alt="Ref"></a> </td></tr></table> <hr size=1 noshade> <tt> <h3><pre> import com.sleepycat.db.*; <p> public void key_range(DbTxn txnid Dbt key, DbKeyRange key_range, int flags) throws DbException; </pre></h3> <h1>Description</h1> <p>The Db.key_range method returns an estimate of the proportion of keys that are less than, equal to, and greater than the specified key. The underlying database must be of type Btree. <p>The information is returned in the <b>key_range</b> argument, which contains three elements of type double: <b>less</b>, <b>equal</b>, and <b>greater</b>. Values are in the range of 0 to 1; for example, if the field <b>less</b> is 0.05, 5% of the keys in the database are less than the key argument. The value for <b>equal</b> will be zero if there is no matching key, and will be non-zero otherwise. <p>If the operation is to be transaction-protected, the <b>txnid</b> parameter is a transaction handle returned from <a href="../api_java/txn_begin.html">DbEnv.txn_begin</a>; otherwise, null. The Db.key_range method does not retain the locks it acquires for the life of the transaction, so estimates may not be repeatable. <p>The <b>flags</b> parameter is currently unused, and must be set to 0. <p>The Db.key_range method throws an exception that encapsulates a non-zero error value on failure. <h1>Errors</h1> <p>The Db.key_range method may fail and throw an exception encapsulating a non-zero error for the following conditions: <p><dl compact> <p><dt>EINVAL<dd>An invalid flag value or parameter was specified. <p>The underlying database was not of type Btree. </dl> <p>If the operation was selected to resolve a deadlock, the Db.key_range method will fail and throw a <a href="../api_java/deadlock_class.html">DbDeadlockException</a> exception. <p>The Db.key_range method may fail and throw an exception for errors specified for other Berkeley DB and C library or system methods. If a catastrophic error has occurred, the Db.key_range method may fail and throw a <a href="../api_java/runrec_class.html">DbRunRecoveryException</a>, in which case all subsequent Berkeley DB calls will fail in the same way. <h1>Class</h1> <a href="../api_java/db_class.html">Db</a> <h1>See Also</h1> <a href="../api_java/db_list.html">Databases and Related Methods</a> </tt> <table width="100%"><tr><td><br></td><td align=right> <a href="../api_java/c_index.html"><img src="../images/api.gif" alt="API"></a><a href="../reftoc.html"><img src="../images/ref.gif" alt="Ref"></a> </td></tr></table> <p><font size=1><a href="http://www.sleepycat.com">Copyright Sleepycat Software</a></font> </body> </html>