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<h2 title="Interface ForeignKeyNullifier" class="title">Interface ForeignKeyNullifier</h2>
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<dt>All Known Implementing Classes:</dt>
<dd><a href="../../../com/sleepycat/bind/serial/SerialSerialKeyCreator.html" title="class in com.sleepycat.bind.serial">SerialSerialKeyCreator</a>, <a href="../../../com/sleepycat/bind/serial/TupleSerialKeyCreator.html" title="class in com.sleepycat.bind.serial">TupleSerialKeyCreator</a>, <a href="../../../com/sleepycat/bind/serial/TupleSerialMarshalledKeyCreator.html" title="class in com.sleepycat.bind.serial">TupleSerialMarshalledKeyCreator</a>, <a href="../../../com/sleepycat/bind/tuple/TupleTupleKeyCreator.html" title="class in com.sleepycat.bind.tuple">TupleTupleKeyCreator</a>, <a href="../../../com/sleepycat/bind/tuple/TupleTupleMarshalledKeyCreator.html" title="class in com.sleepycat.bind.tuple">TupleTupleMarshalledKeyCreator</a></dd>
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<pre>public interface <span class="strong">ForeignKeyNullifier</span></pre>
<div class="block">The interface implemented for setting single-valued foreign keys to null.
<p>A key nullifier is used with a secondary database that is configured to
have a foreign key integrity constraint and a delete action of <a href="../../../com/sleepycat/db/ForeignKeyDeleteAction.html#NULLIFY"><code>ForeignKeyDeleteAction.NULLIFY</code></a>. The key nullifier is specified by calling
<a href="../../../com/sleepycat/db/SecondaryConfig.html#setForeignKeyNullifier(com.sleepycat.db.ForeignKeyNullifier)"><code>SecondaryConfig.setForeignKeyNullifier(com.sleepycat.db.ForeignKeyNullifier)</code></a>.</p>
<p>When a referenced record in the foreign key database is deleted and the
foreign key delete action is <code>NULLIFY</code>, the <a href="../../../com/sleepycat/db/ForeignKeyNullifier.html#nullifyForeignKey(com.sleepycat.db.SecondaryDatabase,%20com.sleepycat.db.DatabaseEntry)"><code>nullifyForeignKey(com.sleepycat.db.SecondaryDatabase, com.sleepycat.db.DatabaseEntry)</code></a> method is called. This method sets
the foreign key reference to null in the datum of the primary database. The
primary database is then updated to contain the modified datum. The result
is that the secondary key is deleted.</p>
This interface may be used along with <a href="../../../com/sleepycat/db/SecondaryKeyCreator.html" title="interface in com.sleepycat.db"><code>SecondaryKeyCreator</code></a> for
many-to-one and one-to-one relationships. It may <em>not</em> be used with
<a href="../../../com/sleepycat/db/SecondaryMultiKeyCreator.html" title="interface in com.sleepycat.db"><code>SecondaryMultiKeyCreator</code></a> because the secondary key is not passed as
a parameter to the nullifyForeignKey method and this method would not know
which key to nullify. When using <a href="../../../com/sleepycat/db/SecondaryMultiKeyCreator.html" title="interface in com.sleepycat.db"><code>SecondaryMultiKeyCreator</code></a>, use
<a href="../../../com/sleepycat/db/ForeignMultiKeyNullifier.html" title="interface in com.sleepycat.db"><code>ForeignMultiKeyNullifier</code></a> instead.</div>
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<td class="colFirst"><code>boolean</code></td>
<td class="colLast"><code><strong><a href="../../../com/sleepycat/db/ForeignKeyNullifier.html#nullifyForeignKey(com.sleepycat.db.SecondaryDatabase,%20com.sleepycat.db.DatabaseEntry)">nullifyForeignKey</a></strong>(<a href="../../../com/sleepycat/db/SecondaryDatabase.html" title="class in com.sleepycat.db">SecondaryDatabase</a> secondary,
<a href="../../../com/sleepycat/db/DatabaseEntry.html" title="class in com.sleepycat.db">DatabaseEntry</a> data)</code>
<div class="block">Sets the foreign key reference to null in the datum of the primary
database.</div>
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<h4>nullifyForeignKey</h4>
<pre>boolean nullifyForeignKey(<a href="../../../com/sleepycat/db/SecondaryDatabase.html" title="class in com.sleepycat.db">SecondaryDatabase</a> secondary,
<a href="../../../com/sleepycat/db/DatabaseEntry.html" title="class in com.sleepycat.db">DatabaseEntry</a> data)
throws <a href="../../../com/sleepycat/db/DatabaseException.html" title="class in com.sleepycat.db">DatabaseException</a></pre>
<div class="block">Sets the foreign key reference to null in the datum of the primary
database.</div>
<dl><dt><span class="strong">Parameters:</span></dt><dd><code>secondary</code> - the database in which the foreign key integrity
constraint is defined. This parameter is passed for informational
purposes but is not commonly used.</dd><dd><code>data</code> - the existing primary datum in which the foreign key
reference should be set to null. This parameter should be updated by
this method if it returns true.</dd>
<dt><span class="strong">Returns:</span></dt><dd>true if the datum was modified, or false to indicate that the
key is not present.</dd>
<dt><span class="strong">Throws:</span></dt>
<dd><code><a href="../../../com/sleepycat/db/DatabaseException.html" title="class in com.sleepycat.db">DatabaseException</a></code> - if an error occurs attempting to clear the key
reference.</dd></dl>
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