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HTML
104 lines
5.2 KiB
HTML
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<?xml version="1.0" encoding="UTF-8" standalone="no"?>
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<html xmlns="http://www.w3.org/1999/xhtml">
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
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<title>DB->put</title>
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<link rel="stylesheet" href="gettingStarted.css" type="text/css" />
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<meta name="generator" content="DocBook XSL Stylesheets V1.73.2" />
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<link rel="start" href="index.html" title="Berkeley DB Upgrade Guide" />
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<link rel="up" href="upgrade_3_1_toc.html" title="Chapter 13. Upgrading Berkeley DB 3.0 applications to Berkeley DB 3.1" />
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<link rel="prev" href="upgrade_3_1_set_paniccall.html" title="DB_ENV->set_paniccall, DB->set_paniccall" />
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<link rel="next" href="upgrade_3_1_dup.html" title="identical duplicate data items" />
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</head>
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<body>
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<div xmlns="" class="navheader">
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<div class="libver">
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<p>Library Version 11.2.5.2</p>
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</div>
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<table width="100%" summary="Navigation header">
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<tr>
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<th colspan="3" align="center">DB->put</th>
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</tr>
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<tr>
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<td width="20%" align="left"><a accesskey="p" href="upgrade_3_1_set_paniccall.html">Prev</a> </td>
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<th width="60%" align="center">Chapter 13. Upgrading Berkeley DB 3.0 applications to Berkeley DB 3.1</th>
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<td width="20%" align="right"> <a accesskey="n" href="upgrade_3_1_dup.html">Next</a></td>
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</tr>
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</table>
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<hr />
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</div>
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<div class="sect1" lang="en" xml:lang="en">
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<div class="titlepage">
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<div>
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<div>
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<h2 class="title" style="clear: both"><a id="upgrade_3_1_put"></a>DB->put</h2>
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</div>
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</div>
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</div>
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<p>For the Queue and Recno access methods, when the <a href="../api_reference/C/dbput.html#dbput_DB_APPEND" class="olink">DB_APPEND</a> flag
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is specified to the <a href="../api_reference/C/dbput.html" class="olink">DB->put()</a> method, the allocated record number is
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returned to the application in the <span class="bold"><strong>key</strong></span> <a href="../api_reference/C/dbt.html" class="olink">DBT</a> argument. In
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previous releases of Berkeley DB, this <a href="../api_reference/C/dbt.html" class="olink">DBT</a> structure did not follow
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the usual <a href="../api_reference/C/dbt.html" class="olink">DBT</a> conventions. For example, it was not possible to
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cause Berkeley DB to allocate space for the returned record number. Rather,
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it was always assumed that the <span class="bold"><strong>data</strong></span> field of the <span class="bold"><strong>key</strong></span>
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structure referred to memory that could be used as storage for a
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db_recno_t type.</p>
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<p>As of the Berkeley DB 3.1.0 release, the <span class="bold"><strong>key</strong></span> structure behaves as
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described in the <a href="../api_reference/C/dbt.html" class="olink">DBT</a> C++/Java class or C structure documentation.</p>
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<p>Applications which are using the <a href="../api_reference/C/dbput.html#dbput_DB_APPEND" class="olink">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_reference/C/dbt.html#dbt_DB_DBT_USERMEM" class="olink">DB_DBT_USERMEM</a> flag to the <span class="bold"><strong>key</strong></span> structure. For example,
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code that appears as follows:</p>
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<pre class="programlisting">DBT key;
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db_recno_t recno;
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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>
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<p>would be changed to:</p>
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<pre class="programlisting">DBT key;
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db_recno_t recno;
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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>
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<p>Note that the <span class="bold"><strong>ulen</strong></span> field is now set as well as the flag value.
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An alternative change would be:</p>
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<pre class="programlisting">DBT key;
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db_recno_t recno;
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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>
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</div>
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<div class="navfooter">
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<hr />
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<table width="100%" summary="Navigation footer">
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<tr>
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<td width="40%" align="left"><a accesskey="p" href="upgrade_3_1_set_paniccall.html">Prev</a> </td>
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<td width="20%" align="center">
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<a accesskey="u" href="upgrade_3_1_toc.html">Up</a>
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</td>
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<td width="40%" align="right"> <a accesskey="n" href="upgrade_3_1_dup.html">Next</a></td>
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</tr>
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<tr>
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<td width="40%" align="left" valign="top">DB_ENV->set_paniccall, DB->set_paniccall </td>
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<td width="20%" align="center">
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<a accesskey="h" href="index.html">Home</a>
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</td>
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<td width="40%" align="right" valign="top"> identical duplicate data items</td>
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</tr>
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</table>
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</div>
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</body>
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</html>
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