com.sleepycat.client

Interface SForeignKeyNullifier

All Superinterfaces:

SForeignMultiKeyNullifier

public interface SForeignKeyNullifier
extends SForeignMultiKeyNullifier

The interface implemented for setting single-valued foreign keys to null.

A key nullifier is used with a secondary database that is configured to have a foreign key integrity constraint and a delete action of SForeignKeyDeleteAction.NULLIFY. The key nullifier is specified by calling SSecondaryConfig.setForeignKeyNullifier(com.sleepycat.client.SForeignKeyNullifier).

When a referenced record in the foreign key database is deleted and the foreign key delete action is NULLIFY, the nullifyForeignKey(com.sleepycat.client.SSecondaryDatabase, com.sleepycat.client.SDatabaseEntry) 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.

This interface may be used along with SSecondaryKeyCreator for many-to-one and one-to-one relationships. It may not be used with SSecondaryMultiKeyCreator 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 SSecondaryMultiKeyCreator, use SForeignMultiKeyNullifier instead.

Method Summary

Modifier and Type	Method and Description
boolean	nullifyForeignKey(SSecondaryDatabase secondary, SDatabaseEntry data) Sets the foreign key reference to null in the datum of the primary database.
default boolean	nullifyForeignKey(SSecondaryDatabase secondary, SDatabaseEntry key, SDatabaseEntry data, SDatabaseEntry secKey) Sets the foreign key reference to null in the datum of the primary database.

Method Detail

nullifyForeignKey

boolean nullifyForeignKey(SSecondaryDatabase secondary,
                          SDatabaseEntry data)
                   throws SDatabaseException

Sets the foreign key reference to null in the datum of the primary database.

Parameters:

secondary - the database in which the foreign key integrity constraint is defined. This parameter is passed for informational purposes but is not commonly used.

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.

Returns:

true if the datum was modified, or false to indicate that the key is not present.

Throws:

SDatabaseException - if an error occurs attempting to clear the key reference.

nullifyForeignKey

default boolean nullifyForeignKey(SSecondaryDatabase secondary,
                                  SDatabaseEntry key,
                                  SDatabaseEntry data,
                                  SDatabaseEntry secKey)
                           throws SDatabaseException

Description copied from interface: SForeignMultiKeyNullifier

Sets the foreign key reference to null in the datum of the primary database.

Specified by:

nullifyForeignKey in interface SForeignMultiKeyNullifier

Parameters:

secondary - the database in which the foreign key integrity constraint is defined. This parameter is passed for informational purposes but is not commonly used.

key - the existing primary key. This parameter is passed for informational purposes but is not commonly used.

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.

secKey - the secondary key to be nullified. This parameter is needed for knowing which key to nullify when multiple keys are present, as when SSecondaryMultiKeyCreator is used.

Returns:

true if the datum was modified, or false to indicate that the key is not present.

Throws:

SDatabaseException - if an error occurs attempting to clear the key reference.