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<!--$Id: put.so,v 1.8 2000/07/25 16:59:37 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 Reference Guide: Release 3.1: DB->put</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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<body bgcolor=white>
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<table><tr valign=top>
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<td><h3><dl><dt>Berkeley DB Reference Guide:<dd>Upgrading Berkeley DB Applications</dl></h3></td>
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<td width="1%"><a href="../../ref/upgrade.3.1/set_paniccall.html"><img src="../../images/prev.gif" alt="Prev"></a><a href="../../ref/toc.html"><img src="../../images/ref.gif" alt="Ref"></a><a href="../../ref/upgrade.3.1/dup.html"><img src="../../images/next.gif" alt="Next"></a>
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</td></tr></table>
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<p>
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<h1 align=center>Release 3.1: DB->put</h1>
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<p>For the Queue and Recno access methods, when the <a href="../../api_c/db_put.html#DB_APPEND">DB_APPEND</a> flag
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is specified to the <a href="../../api_c/db_put.html">DB->put</a> interface, the allocated record number
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is returned to the application in the <b>key</b> <a href="../../api_c/dbt.html">DBT</a> argument.
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In previous releases of Berkeley DB, this <a href="../../api_c/dbt.html">DBT</a> structure did not follow
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the usual <a href="../../api_c/dbt.html">DBT</a> conventions, e.g., it was not possible to cause
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Berkeley DB to allocate space for the returned record number. Rather, it was
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always assumed that the <b>data</b> field of the <b>key</b> structure
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referenced memory that could be used as storage for a db_recno_t type.
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<p>As of the Berkeley DB 3.1.0 release, the <b>key</b> structure behaves as
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described in the <a href="../../api_c/dbt.html">DBT</a> C++/Java class or C structure documentation.
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<p>Applications which are using the <a href="../../api_c/db_put.html#DB_APPEND">DB_APPEND</a> flag for Queue and
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Recno access method databases will require a change to upgrade to the
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Berkeley DB 3.1 releases. The simplest change is likely to be to add the
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<a href="../../api_c/dbt.html#DB_DBT_USERMEM">DB_DBT_USERMEM</a> flag to the <b>key</b> structure. For example,
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code that appears as follows:
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<p><blockquote><pre>DBT key;
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db_recno_t recno;
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<p>
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memset(&key, 0, sizeof(DBT));
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key.data = &recno;
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key.size = sizeof(recno);
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DB->put(DB, NULL, &key, &data, DB_APPEND);
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printf("new record number is %lu\n", (u_long)recno);</pre></blockquote>
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<p>would be changed to:
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<p><blockquote><pre>DBT key;
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db_recno_t recno;
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<p>
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memset(&key, 0, sizeof(DBT));
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key.data = &recno;
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key.ulen = sizeof(recno);
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key.flags = DB_DBT_USERMEM;
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DB->put(DB, NULL, &key, &data, DB_APPEND);
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printf("new record number is %lu\n", (u_long)recno);</pre></blockquote>
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<p>Note that the <b>ulen</b> field is now set as well as the flag value.
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An alternative change would be:
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<p><blockquote><pre>DBT key;
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db_recno_t recno;
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<p>
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memset(&key, 0, sizeof(DBT));
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DB->put(DB, NULL, &key, &data, DB_APPEND);
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recno = *(db_recno_t *)key->data;
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printf("new record number is %lu\n", (u_long)recno);</pre></blockquote>
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<table><tr><td><br></td><td width="1%"><a href="../../ref/upgrade.3.1/set_paniccall.html"><img src="../../images/prev.gif" alt="Prev"></a><a href="../../ref/toc.html"><img src="../../images/ref.gif" alt="Ref"></a><a href="../../ref/upgrade.3.1/dup.html"><img src="../../images/next.gif" alt="Next"></a>
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</td></tr></table>
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