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100 lines
4.9 KiB
HTML
<!--$Id: db_key_range.so,v 10.5 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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<html>
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<head>
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<title>Berkeley DB: Db.key_range</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.key_range</h1>
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</td>
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<td width="1%">
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<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>
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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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import com.sleepycat.db.*;
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<p>
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public void key_range(DbTxn txnid
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Dbt key, DbKeyRange key_range, int flags)
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throws DbException;
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</pre></h3>
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<h1>Description</h1>
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<p>The Db.key_range method returns an estimate of the proportion of keys
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that are less than, equal to and greater than the specified key. The
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underlying database must be of type Btree.
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<p>The information is returned in the <b>key_range</b> argument, which
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contains three elements of type double, <b>less</b>, <b>equal</b> and
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<b>greater</b>. Values are in the range of 0 to 1, e.g., if the field
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<b>less</b> is 0.05, that indicates that 5% of the keys in the database
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are less than the key argument. The value for <b>equal</b> will be zero
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if there is no matching key and non-zero otherwise.
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<p>If the file is being accessed under transaction protection, the
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<b>txnid</b> parameter is a transaction ID returned from
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<a href="../api_java/txn_begin.html">DbEnv.txn_begin</a>, otherwise, NULL.
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The Db.key_range method does not retain the locks it acquires for the
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life of the transaction, so estimates may not be repeatable.
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<p>The <b>flags</b> parameter is currently unused, and must be set to 0.
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<p>The Db.key_range method throws an exception that encapsulates a non-zero error value on
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failure.
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<h1>Errors</h1>
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<p>The Db.key_range method may fail and throw an exception encapsulating a non-zero error for the following conditions:
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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>The underlying database was not of type Btree.
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</dl>
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<p>If the operation was selected to resolve a deadlock, the
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Db.key_range method will fail and
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throw a <a href="../api_java/deadlock_class.html">DbDeadlockException</a> exception.
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<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.
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If a catastrophic error has occurred, the Db.key_range method may fail and throw
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a <a href="../api_java/runrec_class.html">DbRunRecoveryException</a>, in which case all subsequent Berkeley DB calls
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will fail in the same way.
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<h3>Class</h3>
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<a href="../api_java/db_class.html">Db</a>
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<h1>See Also</h1>
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<a href="../api_java/db_close.html">Db.close</a>,
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<a href="../api_java/db_cursor.html">Db.cursor</a>,
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<a href="../api_java/db_del.html">Db.del</a>,
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<a href="../api_java/db_fd.html">Db.fd</a>,
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<a href="../api_java/db_get.html">Db.get</a>,
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<a href="../api_java/db_get_byteswapped.html">Db.get_byteswapped</a>,
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<a href="../api_java/db_get_type.html">Db.get_type</a>,
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<a href="../api_java/db_join.html">Db.join</a>,
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<a href="../api_java/db_key_range.html">Db.key_range</a>,
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<a href="../api_java/db_open.html">Db.open</a>,
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<a href="../api_java/db_put.html">Db.put</a>,
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<a href="../api_java/db_remove.html">Db.remove</a>,
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<a href="../api_java/db_set_bt_minkey.html">Db.set_bt_minkey</a>,
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<a href="../api_java/db_set_cachesize.html">Db.set_cachesize</a>,
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<a href="../api_java/db_set_errcall.html">Db.set_errcall</a>,
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<a href="../api_java/db_set_errpfx.html">Db.set_errpfx</a>,
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<a href="../api_java/db_set_flags.html">Db.set_flags</a>,
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<a href="../api_java/db_set_h_ffactor.html">Db.set_h_ffactor</a>,
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<a href="../api_java/db_set_h_nelem.html">Db.set_h_nelem</a>,
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<a href="../api_java/db_set_lorder.html">Db.set_lorder</a>,
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<a href="../api_java/db_set_pagesize.html">Db.set_pagesize</a>,
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<a href="../api_java/db_set_q_extentsize.html">Db.set_q_extentsize</a>,
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<a href="../api_java/db_set_re_delim.html">Db.set_re_delim</a>,
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<a href="../api_java/db_set_re_len.html">Db.set_re_len</a>,
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<a href="../api_java/db_set_re_pad.html">Db.set_re_pad</a>,
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<a href="../api_java/db_set_re_source.html">Db.set_re_source</a>,
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<a href="../api_java/db_stat.html">Db.stat</a>,
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<a href="../api_java/db_sync.html">Db.sync</a>,
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<a href="../api_java/db_upgrade.html">Db.upgrade</a>
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and
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<a href="../api_java/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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