<?xml version="1.0" encoding="UTF-8" standalone="no"?> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /> <title>DB->associate_foreign()</title> <link rel="stylesheet" href="apiReference.css" type="text/css" /> <meta name="generator" content="DocBook XSL Stylesheets V1.73.2" /> <link rel="start" href="index.html" title="Berkeley DB C API Reference" /> <link rel="up" href="db.html" title="Chapter 2. The DB Handle" /> <link rel="prev" href="dbassociate.html" title="DB->associate()" /> <link rel="next" href="dbclose.html" title="DB->close()" /> </head> <body> <div class="navheader"> <table width="100%" summary="Navigation header"> <tr> <th colspan="3" align="center">DB->associate_foreign()</th> </tr> <tr> <td width="20%" align="left"><a accesskey="p" href="dbassociate.html">Prev</a> </td> <th width="60%" align="center">Chapter 2. The DB Handle </th> <td width="20%" align="right"> <a accesskey="n" href="dbclose.html">Next</a></td> </tr> </table> <hr /> </div> <div class="sect1" lang="en" xml:lang="en"> <div class="titlepage"> <div> <div> <h2 class="title" style="clear: both"><a id="dbassociate_foreign"></a>DB->associate_foreign()</h2> </div> </div> </div> <pre class="programlisting">#include <db.h> int DB->associate_foreign(DB *foreign, DB *secondary,, int (*callback)(DB *secondary, const DBT *key, DBT *data, const DBT *foreignkey, int *changed), u_int32_t flags); </pre> <p> The <code class="methodname">DB->associate_foreign()</code> function is used to declare one database a foreign constraint for a secondary database. The <a class="link" href="db.html" title="Chapter 2. The DB Handle">DB</a> handle that you call the <code class="methodname">associate_foreign()</code> method from is the foreign database. </p> <p> After a foreign database has been "associated" with a secondary database, all keys inserted into the secondary must exist in the foreign database. Attempting to add a record with a foreign key that does not exist in the foreign database will cause the put method to fail and return <code class="literal">DB_FOREIGN_CONFLICT</code>. </p> <p> Deletions in the foreign database affect the secondary in a manner defined by the flags parameter. See <a href="../../programmer_reference/am_foreign.html" class="olink">Foreign Indices</a> in the <em class="citetitle">Berkeley DB Programmer's Reference Guide</em> for more information. </p> <p> The <code class="methodname">DB->associate_foreign()</code> <span> <span> method returns a non-zero error value on failure and 0 on success. </span> </span> </p> <div class="sect2" lang="en" xml:lang="en"> <div class="titlepage"> <div> <div> <h3 class="title"><a id="id1631161"></a>Parameters</h3> </div> </div> </div> <div class="sect3" lang="en" xml:lang="en"> <div class="titlepage"> <div> <div> <h4 class="title"><a id="id1630956"></a>callback</h4> </div> </div> </div> <p> The <span class="bold"><strong>callback</strong></span> parameter is a callback function that nullifies the foreign key portion of a data <a class="link" href="dbt.html" title="Chapter 4. The DBT Handle">DBT</a>. </p> <p> The callback parameter must be NULL if either DB_FOREIGN_ABORT or DB_FOREIGN_CASCADE is set. </p> <p> The callback takes four arguments: </p> <div class="itemizedlist"> <ul type="disc"> <li> <p> <code class="literal">secondary</code> </p> <p> The <span class="bold"><strong>secondary</strong></span> parameter is the database handle for the secondary. </p> </li> <li> <p> <code class="literal">key</code> </p> <p> The <span class="bold"><strong>key</strong></span> parameter is a <a class="link" href="dbt.html" title="Chapter 4. The DBT Handle">DBT</a> referencing the primary key. </p> </li> <li> <p> <code class="literal">data</code> </p> <p> The <span class="bold"><strong>data</strong></span> parameter is a <a class="link" href="dbt.html" title="Chapter 4. The DBT Handle">DBT</a> referencing the primary data item to be updated. </p> </li> <li> <p> <code class="literal">foreignkey</code> </p> <p> The <span class="bold"><strong>foreignkey</strong></span> parameter is a <a class="link" href="dbt.html" title="Chapter 4. The DBT Handle">DBT</a> referencing the foreign key which is being deleted. </p> </li> <li> <p> <code class="literal">changed</code> </p> <p> The <span class="bold"><strong>changed</strong></span> parameter is a pointer to a boolean value, indicated whether <span class="bold"><strong>data</strong></span> has changed. </p> </li> </ul> </div> <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"> <h3 class="title">Note</h3> <p> Berkeley DB is not re-entrant. Callback functions should not attempt to make library calls (for example, to release locks or close open handles). Re-entering Berkeley DB is not guaranteed to work correctly, and the results are undefined. </p> </div> </div> <div class="sect3" lang="en" xml:lang="en"> <div class="titlepage"> <div> <div> <h4 class="title"><a id="id1632271"></a>flags</h4> </div> </div> </div> <p> The <span class="bold"><strong>flags</strong></span> parameter must be set to one of the following values: </p> <div class="itemizedlist"> <ul type="disc"> <li> <p><a id="associate_foreign_DB_FOREIGN_ABORT"></a> <code class="literal">DB_FOREIGN_ABORT</code> </p> <p> Abort the deletion of a key in the foreign database and return DB_FOREIGN_CONFLICT if that key exists in the secondary database. The deletion should be protected by a transaction to ensure database integrity after the aborted delete. </p> </li> <li> <p><a id="associate_foreign_DB_FOREIGN_CASCADE"></a> <code class="literal">DB_FOREIGN_CASCADE</code> </p> <p> The deletion of a key in the foreign database will also delete that key from the secondary database (and the corresponding entry in the secondary's primary database.) </p> </li> <li> <p><a id="associate_foreign_DB_FOREIGN_NULLIFY"></a> <code class="literal">DB_FOREIGN_NULLIFY</code> </p> <p> The deletion of a key in the foreign database will call the nullification function passed to associate_foreign and update the secondary database with the changed data. </p> </li> </ul> </div> </div> <div class="sect3" lang="en" xml:lang="en"> <div class="titlepage"> <div> <div> <h4 class="title"><a id="id1632009"></a>foreign</h4> </div> </div> </div> <p> The <span class="bold"><strong>foreign</strong></span> parameter should be a database handle for the foreign database. </p> </div> <div class="sect3" lang="en" xml:lang="en"> <div class="titlepage"> <div> <div> <h4 class="title"><a id="id1631694"></a>secondary</h4> </div> </div> </div> <p> The <span class="bold"><strong>secondary</strong></span> parameter should be an open database handle of a database that contains a secondary index who's keys also exist in the <span class="bold"><strong>foreign</strong></span> database. </p> </div> </div> <div class="sect2" lang="en" xml:lang="en"> <div class="titlepage"> <div> <div> <h3 class="title"><a id="id1631353"></a>Errors</h3> </div> </div> </div> <p> The <code class="methodname">DB->associate_foreign()</code> <span> <span> method may fail and return one of the following non-zero errors: </span> </span> </p> <div class="sect3" lang="en" xml:lang="en"> <div class="titlepage"> <div> <div> <h4 class="title"><a id="id1631714"></a> DB_REP_HANDLE_DEAD</h4> </div> </div> </div> <p> When a client synchronizes with the master, it is possible for committed transactions to be rolled back. This invalidates all the database and cursor handles opened in the replication environment. Once this occurs, an attempt to use such a handle will return <code class="literal">DB_REP_HANDLE_DEAD</code>. The application will need to discard the handle and open a new one in order to continue processing. </p> </div> <div class="sect3" lang="en" xml:lang="en"> <div class="titlepage"> <div> <div> <h4 class="title"><a id="id1631807"></a>DB_REP_LOCKOUT</h4> </div> </div> </div> <p> The operation was blocked by client/master synchronization. </p> </div> <div class="sect3" lang="en" xml:lang="en"> <div class="titlepage"> <div> <div> <h4 class="title"><a id="id1632034"></a>EINVAL</h4> </div> </div> </div> <p> If the foreign database handle is a secondary index; the foreign database handle has been configured to allow duplicates; the foreign database handle is a renumbering recno database; callback is configured and DB_FOREIGN_NULLIFY is not; DB_FOREIGN_NULLIFY is configured and callback is not. </p> </div> </div> <div class="sect2" lang="en" xml:lang="en"> <div class="titlepage"> <div> <div> <h3 class="title"><a id="id1631953"></a>Class</h3> </div> </div> </div> <p> <a class="link" href="db.html" title="Chapter 2. The DB Handle">DB</a> </p> </div> <div class="sect2" lang="en" xml:lang="en"> <div class="titlepage"> <div> <div> <h3 class="title"><a id="id1630442"></a>See Also</h3> </div> </div> </div> <p> <a class="xref" href="db.html#dblist" title="Database and Related Methods">Database and Related Methods</a> </p> </div> </div> <div class="navfooter"> <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> </td> <td width="40%" align="right"> <a accesskey="n" href="dbclose.html">Next</a></td> </tr> <tr> <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>