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public interface ForeignKeyNullifier
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 ForeignKeyDeleteAction.NULLIFY
. The key nullifier is specified by calling
SecondaryConfig.setForeignKeyNullifier(com.sleepycat.je.ForeignKeyNullifier)
.
When a referenced record in the foreign key database is deleted and the
foreign key delete action is NULLIFY
, the nullifyForeignKey(com.sleepycat.je.SecondaryDatabase, com.sleepycat.je.DatabaseEntry)
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 SecondaryKeyCreator
for
many-to-one and one-to-one relationships. It may not be used with
SecondaryMultiKeyCreator
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 SecondaryMultiKeyCreator
, use ForeignMultiKeyNullifier
instead.
Method Summary | |
---|---|
boolean |
nullifyForeignKey(SecondaryDatabase secondary,
DatabaseEntry data)
Sets the foreign key reference to null in the datum of the primary database. |
Method Detail |
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boolean nullifyForeignKey(SecondaryDatabase secondary, DatabaseEntry data) throws DatabaseException
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.
DatabaseException
- if an error occurs attempting to clear the
key reference.
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