<!--$Id: db_set_bt_compare.so,v 10.24 2000/10/26 15:20:40 bostic Exp $--> <!--Copyright 1997, 1998, 1999, 2000 by Sleepycat Software, Inc.--> <!--All rights reserved.--> <html> <head> <title>Berkeley DB: Db.set_bt_compare</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><tr valign=top> <td> <h1>Db.set_bt_compare</h1> </td> <td width="1%"> <a href="../api_java/java_index.html"><img src="../images/api.gif" alt="API"></a><a href="../ref/toc.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 interface DbBtreeCompare { public abstract int bt_compare(Db db, Dbt dbt1, Dbt dbt2); } public class Db { public void set_bt_compare(DbBtreeCompare bt_compare) throws DbException; ... } </pre></h3> <h1>Description</h1> <p>Set the Btree key comparison function. The comparison function is called when it is necessary to compare a key specified by the application with a key currently stored in the tree. The first argument to the comparison function is the <a href="../api_java/dbt_class.html">Dbt</a> representing the application supplied key, the second is the current tree's key. <p>The comparison function must return an integer value less than, equal to, or greater than zero if the first key argument is considered to be respectively less than, equal to, or greater than the second key argument. In addition, the comparison function must cause the keys in the database to be <i>well-ordered</i>. The comparison function must correctly handle any key values used by the application (possibly including zero-length keys). In addition, when Btree key prefix comparison is being performed (see <a href="../api_java/db_set_bt_prefix.html">Db.set_bt_prefix</a> for more information), the comparison routine may be passed a prefix of any database key. The <b>data</b> and <b>size</b> fields of the <a href="../api_java/dbt_class.html">Dbt</a> are the only fields that may be used for the purposes of this comparison. <p>If no comparison function is specified, the keys are compared lexically, with shorter keys collating before longer keys. The same comparison method must be used each time a particular Btree is opened. <p>The Db.set_bt_compare interface may only be used to configure Berkeley DB before the <a href="../api_java/db_open.html">Db.open</a> interface is called. <p>The Db.set_bt_compare method throws an exception that encapsulates a non-zero error value on failure. <h1>Errors</h1> <p><dl compact> <p><dt>EINVAL<dd>An invalid flag value or parameter was specified. <p>Called after <a href="../api_java/db_open.html">Db.open</a> was called. </dl> <h3>Class</h3> <a href="../api_java/db_class.html">Db</a> <h1>See Also</h1> <a href="../api_java/db_close.html">Db.close</a>, <a href="../api_java/db_cursor.html">Db.cursor</a>, <a href="../api_java/db_del.html">Db.del</a>, <a href="../api_java/db_fd.html">Db.fd</a>, <a href="../api_java/db_get.html">Db.get</a>, <a href="../api_java/db_get_byteswapped.html">Db.get_byteswapped</a>, <a href="../api_java/db_get_type.html">Db.get_type</a>, <a href="../api_java/db_join.html">Db.join</a>, <a href="../api_java/db_key_range.html">Db.key_range</a>, <a href="../api_java/db_open.html">Db.open</a>, <a href="../api_java/db_put.html">Db.put</a>, <a href="../api_java/db_remove.html">Db.remove</a>, <a href="../api_java/db_set_bt_minkey.html">Db.set_bt_minkey</a>, <a href="../api_java/db_set_cachesize.html">Db.set_cachesize</a>, <a href="../api_java/db_set_errcall.html">Db.set_errcall</a>, <a href="../api_java/db_set_errpfx.html">Db.set_errpfx</a>, <a href="../api_java/db_set_flags.html">Db.set_flags</a>, <a href="../api_java/db_set_h_ffactor.html">Db.set_h_ffactor</a>, <a href="../api_java/db_set_h_nelem.html">Db.set_h_nelem</a>, <a href="../api_java/db_set_lorder.html">Db.set_lorder</a>, <a href="../api_java/db_set_pagesize.html">Db.set_pagesize</a>, <a href="../api_java/db_set_q_extentsize.html">Db.set_q_extentsize</a>, <a href="../api_java/db_set_re_delim.html">Db.set_re_delim</a>, <a href="../api_java/db_set_re_len.html">Db.set_re_len</a>, <a href="../api_java/db_set_re_pad.html">Db.set_re_pad</a>, <a href="../api_java/db_set_re_source.html">Db.set_re_source</a>, <a href="../api_java/db_stat.html">Db.stat</a>, <a href="../api_java/db_sync.html">Db.sync</a>, <a href="../api_java/db_upgrade.html">Db.upgrade</a> and <a href="../api_java/db_verify.html">Db.verify</a>. </tt> <table><tr><td><br></td><td width="1%"> <a href="../api_java/java_index.html"><img src="../images/api.gif" alt="API"></a><a href="../ref/toc.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>