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346 lines
14 KiB
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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::associate_foreign()</title>
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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 C++ API Reference" />
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<link rel="up" href="db.html" title="Chapter 2. The Db Handle" />
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<link rel="prev" href="dbassociate.html" title="Db::associate()" />
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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::associate_foreign()</th>
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</tr>
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<tr>
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<td width="20%" align="left"><a accesskey="p" href="dbassociate.html">Prev</a> </td>
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<th width="60%" align="center">Chapter 2.
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The Db Handle
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</th>
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<td width="20%" align="right"> <a accesskey="n" href="dbclose.html">Next</a></td>
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</tr>
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</table>
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<hr />
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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="dbassociate_foreign"></a>Db::associate_foreign()</h2>
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</div>
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</div>
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</div>
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<pre class="programlisting">#include <db_cxx.h>
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int
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DB::associate_foreign(Db *secondary,,
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int (*callback)(Db *secondary,
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const Dbt *key, Dbt *data, const Dbt *foreignkey, int *changed),
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u_int32_t flags); </pre>
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<p>
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The <code class="methodname">Db::associate_foreign()</code> function is used to declare one database a
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foreign constraint for a secondary database. The
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<a class="link" href="db.html" title="Chapter 2. The Db Handle">Db</a> handle that you call the
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<code class="methodname">associate_foreign()</code> method from is the foreign
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database.
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</p>
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<p>
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After a foreign database has been "associated" with a secondary
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database, all keys inserted into the secondary must exist in the
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foreign database. Attempting to add a record with a foreign key
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that does not exist in the foreign database will cause the put
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method to fail and return <code class="literal">DB_FOREIGN_CONFLICT</code>.
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</p>
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<p>
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Deletions in the foreign database affect the secondary in a manner
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defined by the flags parameter. See
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<a href="../../programmer_reference/am_foreign.html" class="olink">Foreign Indices</a>
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in the <em class="citetitle">Berkeley DB Programmer's Reference Guide</em> for more information.
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</p>
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<p>
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The <code class="methodname">Db::associate_foreign()</code> <span>
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<span>
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method either returns a non-zero error value or throws an
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exception that encapsulates a non-zero error value on
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failure, and returns 0 on success.
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</span>
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</span>
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</p>
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<div class="sect2" 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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<h3 class="title"><a id="id3578280"></a>Parameters</h3>
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</div>
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</div>
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</div>
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<div class="sect3" 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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<h4 class="title"><a id="id3578052"></a>secondary</h4>
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</div>
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</div>
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</div>
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<p>
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The <span class="bold"><strong>secondary</strong></span> parameter should be an
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open database handle of a database that contains a secondary index who's
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keys also exist in the <span class="bold"><strong>foreign</strong></span> database.
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</p>
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</div>
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<div class="sect3" 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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<h4 class="title"><a id="id3578096"></a>callback</h4>
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</div>
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</div>
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</div>
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<p>
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The <span class="bold"><strong>callback</strong></span> parameter is a callback
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function that nullifies the foreign key portion of a data <a class="link" href="dbt.html" title="Chapter 4. The Dbt Handle">Dbt</a>.
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</p>
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<p>
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The callback parameter must be NULL if either DB_FOREIGN_ABORT or DB_FOREIGN_CASCADE is set.
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</p>
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<p>
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The callback takes four arguments:
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</p>
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<div class="itemizedlist">
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<ul type="disc">
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<li>
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<p>
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<code class="literal">secondary</code>
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</p>
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<p>
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The <span class="bold"><strong>secondary</strong></span> parameter is the
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database handle for the secondary.
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</p>
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</li>
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<li>
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<p>
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<code class="literal">key</code>
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</p>
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<p>
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The <span class="bold"><strong>key</strong></span> parameter is a
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<a class="link" href="dbt.html" title="Chapter 4. The Dbt Handle">Dbt</a> referencing the primary key.
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</p>
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</li>
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<li>
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<p>
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<code class="literal">data</code>
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</p>
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<p>
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The <span class="bold"><strong>data</strong></span> parameter is a
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<a class="link" href="dbt.html" title="Chapter 4. The Dbt Handle">Dbt</a> referencing the primary data
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item to be updated.
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</p>
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</li>
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<li>
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<p>
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<code class="literal">foreignkey</code>
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</p>
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<p>
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The <span class="bold"><strong>foreignkey</strong></span> parameter is a
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<a class="link" href="dbt.html" title="Chapter 4. The Dbt Handle">Dbt</a> referencing the foreign
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key which is being deleted.
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</p>
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</li>
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<li>
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<p>
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<code class="literal">changed</code>
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</p>
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<p>
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The <span class="bold"><strong>changed</strong></span> parameter is a
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pointer to a boolean value, indicated whether <span class="bold"><strong>data</strong></span>
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has changed.
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</p>
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</li>
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</ul>
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</div>
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<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
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<h3 class="title">Note</h3>
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<p>
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Berkeley DB is not re-entrant. Callback functions should not
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attempt to make library calls (for example, to release locks or
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close open handles). Re-entering Berkeley DB is not guaranteed
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to work correctly, and the results are undefined.
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</p>
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</div>
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</div>
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<div class="sect3" 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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<h4 class="title"><a id="id3578788"></a>flags</h4>
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</div>
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</div>
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</div>
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<p>
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The <span class="bold"><strong>flags</strong></span> parameter must be set to
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one of the following values:
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</p>
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<div class="itemizedlist">
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<ul type="disc">
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<li>
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<p><a id="associate_foreign_DB_FOREIGN_ABORT"></a>
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<code class="literal">DB_FOREIGN_ABORT</code>
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</p>
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<p>
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Abort the deletion of a key in the foreign database and return DB_FOREIGN_CONFLICT
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if that key exists in the secondary database. The deletion should be protected by
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a transaction to ensure database integrity after the aborted delete.
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</p>
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</li>
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<li>
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<p><a id="associate_foreign_DB_FOREIGN_CASCADE"></a>
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<code class="literal">DB_FOREIGN_CASCADE</code>
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</p>
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<p>
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The deletion of a key in the foreign database will also delete that key from the
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secondary database (and the corresponding entry in the secondary's primary database.)
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</p>
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</li>
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<li>
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<p><a id="associate_foreign_DB_FOREIGN_NULLIFY"></a>
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<code class="literal">DB_FOREIGN_NULLIFY</code>
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</p>
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<p>
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The deletion of a key in the foreign database will call the nullification function
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passed to associate_foreign and update the secondary database with the changed data.
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</p>
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</li>
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</ul>
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</div>
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</div>
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</div>
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<div class="sect2" 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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<h3 class="title"><a id="id3578143"></a>Errors</h3>
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</div>
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</div>
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</div>
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<p>
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The <code class="methodname">Db::associate_foreign()</code> <span>
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<span>
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method may fail and throw a <a class="link" href="dbexception.html" title="Chapter 6. The DbException Class">DbException</a>
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exception, encapsulating one of the following non-zero errors, or return one
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of the following non-zero errors:
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</span>
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</span>
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</p>
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<div class="sect3" 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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<h4 class="title"><a id="id3578836"></a> <span>DbRepHandleDeadException or</span> DB_REP_HANDLE_DEAD</h4>
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</div>
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</div>
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</div>
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<p>
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When a client synchronizes with the master, it is possible for committed
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transactions to be rolled back. This invalidates all the database and cursor
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handles opened in the replication environment. Once this occurs, an attempt to use
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such a handle will
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<span>
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throw a <a class="xref" href="dbrephandledead.html" title="DbRepHandleDeadException">DbRepHandleDeadException</a> (if
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your application is configured to throw exceptions), or
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</span>
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return <code class="literal">DB_REP_HANDLE_DEAD</code>.
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The application will need to discard the handle and open a new one in order to
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continue processing.
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</p>
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</div>
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<div class="sect3" 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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<h4 class="title"><a id="id3578809"></a><span>DbDeadlockException or </span>DB_REP_LOCKOUT</h4>
|
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</div>
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</div>
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</div>
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<p>
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The operation was blocked by client/master synchronization.
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</p>
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<p>
|
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<a class="xref" href="dbdeadlock.html" title="DbDeadlockException">DbDeadlockException</a> is thrown if
|
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your Berkeley DB API is configured to throw exceptions.
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Otherwise, <code class="literal">DB_REP_LOCKOUT</code> is returned.
|
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</p>
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</div>
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<div class="sect3" 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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|
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<h4 class="title"><a id="id3578884"></a>EINVAL</h4>
|
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</div>
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</div>
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</div>
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<p>
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If the foreign database handle is a secondary index; the foreign
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|||
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database handle has been configured to allow duplicates; the foreign
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|||
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database handle is a renumbering recno database; callback is
|
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configured and DB_FOREIGN_NULLIFY is not; DB_FOREIGN_NULLIFY is
|
|||
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configured and callback is not.
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</p>
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</div>
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</div>
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<div class="sect2" lang="en" xml:lang="en">
|
|||
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<div class="titlepage">
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|||
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<div>
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<div>
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<h3 class="title"><a id="id3578890"></a>Class</h3>
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</div>
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</div>
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</div>
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<p>
|
|||
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<a class="link" href="db.html" title="Chapter 2. The Db Handle">Db</a>
|
|||
|
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</p>
|
|||
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</div>
|
|||
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<div class="sect2" 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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<h3 class="title"><a id="id3577209"></a>See Also</h3>
|
|||
|
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</div>
|
|||
|
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</div>
|
|||
|
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</div>
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<p>
|
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<a class="xref" href="db.html#dblist" title="Database and Related Methods">Database and Related Methods</a>
|
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</p>
|
|||
|
|
</div>
|
|||
|
|
</div>
|
|||
|
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<div class="navfooter">
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|||
|
|
<hr />
|
|||
|
|
<table width="100%" summary="Navigation footer">
|
|||
|
|
<tr>
|
|||
|
|
<td width="40%" align="left"><a accesskey="p" href="dbassociate.html">Prev</a> </td>
|
|||
|
|
<td width="20%" align="center">
|
|||
|
|
<a accesskey="u" href="db.html">Up</a>
|
|||
|
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</td>
|
|||
|
|
<td width="40%" align="right"> <a accesskey="n" href="dbclose.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::associate() </td>
|
|||
|
|
<td width="20%" align="center">
|
|||
|
|
<a accesskey="h" href="index.html">Home</a>
|
|||
|
|
</td>
|
|||
|
|
<td width="40%" align="right" valign="top"> Db::close()</td>
|
|||
|
|
</tr>
|
|||
|
|
</table>
|
|||
|
|
</div>
|
|||
|
|
</body>
|
|||
|
|
</html>
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