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/*-
* See the file LICENSE for redistribution information.
*
* Copyright (c) 2008, 2015 Oracle and/or its affiliates. All rights reserved.
*
* $Id$
*/
package com.sleepycat.db;
/**
* The interface implemented for setting multi-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 {@link
* ForeignKeyDeleteAction#NULLIFY}. The key nullifier is specified by calling
* {@link SecondaryConfig#setForeignMultiKeyNullifier}.</p>
*
* <p>When a referenced record in the foreign key database is deleted and the
* foreign key delete action is <code>NULLIFY</code>, the {@link
* ForeignMultiKeyNullifier#nullifyForeignKey} 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 {@link SecondaryKeyCreator} or {@link
* SecondaryMultiKeyCreator} for many-to-many, one-to-many, many-to-one and
* one-to-one relationships.
*/
public interface ForeignMultiKeyNullifier {
/**
* Sets the foreign key reference to null in the datum of the primary
* database.
*
* @param secondary the database in which the foreign key integrity
* constraint is defined. This parameter is passed for informational
* purposes but is not commonly used.
*
* @param key the existing primary key. This parameter is passed for
* informational purposes but is not commonly used.
*
* @param data 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.
*
* @param secKey the secondary key to be nullified. This parameter is
* needed for knowing which key to nullify when multiple keys are present,
* as when {@link SecondaryMultiKeyCreator} is used.
*
* @return true if the datum was modified, or false to indicate that the
* key is not present.
*
* @throws DatabaseException if an error occurs attempting to clear the key
* reference.
*/
boolean nullifyForeignKey(SecondaryDatabase secondary, DatabaseEntry key, DatabaseEntry data, DatabaseEntry secKey)
throws DatabaseException;
}
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