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## com.sleepycat.bdb
Class ForeignKeyIndex

    java.lang.Object
      |
      +--com.sleepycat.bdb.DataIndex
            |
            +--com.sleepycat.bdb.ForeignKeyIndex

public class ForeignKeyIndex
extends DataIndex

Represents a Berkeley DB secondary index where the index key is the primary key of another data store. An index is always attached to a single `DataStore` when it is constructed. An index is typically accessed by passing it to the constructor of one of the collection classes in the com.sleepycat.bdb.collection package. For example:

     Db db = new Db(env, 0);
     db.setFlags(Db.DB_DUPSORT);
     db.open(null, "index.db", null, Db.DB_BTREE, dbOpenFlags, 0);
     ForeignKeyIndex index = new ForeignKeyIndex(store, db, keyExtractor,
                                                 foreignStore, deleteAction);
     StoredMap map = new StoredMap(index, keyBinding, valueBinding, writeAllowed);

All access methods may be used with BDB. However, some access methods may only be used with certain types of collection views, and some access methods impose restrictions on the way collection views are used.

Field Summary
`static int` | `ON_DELETE_ABORT` When the foreign key is deleted, throw an exception.
`static int` | `ON_DELETE_CASCADE` When the foreign key is deleted, delete the index key.
`static int` | `ON_DELETE_CLEAR` When the foreign key is deleted, clear the index key.

Constructor Summary
`ForeignKeyIndex(DataStore store, Db db, KeyExtractor keyExtractor, DataStore foreignStore, int deleteAction)` Creates a foreign key index from a previously opened Db object.

Method Summary
`int` | `getDeleteAction()` Returns a value indicating what action occurs when the foreign key is deleted.
`DataStore` | `getForeignStore()` Returns the foreign store which has the primary key which matches the index key of this store.

Methods inherited from class com.sleepycat.bdb.DataIndex
`getKeyExtractor, getKeyFormat, getStore, toString`

Methods inherited from class java.lang.Object
`equals, getClass, hashCode, notify, notifyAll, wait, wait, wait`

Field Detail

### ON_DELETE_ABORT

    public static final int ON_DELETE_ABORT

  When the foreign key is deleted, throw an exception.

  See Also:
    Constant Field Values

### ON_DELETE_CASCADE

    public static final int ON_DELETE_CASCADE

  When the foreign key is deleted, delete the index key.

  See Also:
    Constant Field Values

### ON_DELETE_CLEAR

    public static final int ON_DELETE_CLEAR

  When the foreign key is deleted, clear the index key.

  See Also:
    Constant Field Values

Constructor Detail

### ForeignKeyIndex

    public ForeignKeyIndex(DataStore store,
                           Db db,
                           KeyExtractor keyExtractor,
                           DataStore foreignStore,
                           int deleteAction)

  Creates a foreign key index from a previously opened Db object.

Parameters:
  `store` - the store to be indexed and also specifies the environment that was used to create the Db object.
  `db` - the previously opened Db object.
  `keyExtractor` - an object for extracting the index key from primary key and/or value buffers, and for clearing the index key in a value buffer.
  `foreignStore` - is the store in which the index key for this store is a primary key.
  `deleteAction` - determines what action occurs when the foreign key is deleted. It must be one of the ON_DELETE_ constants.
Throws:
  `IllegalArgumentException` - if a format mismatch is detected between the index and the store, or if unsorted duplicates were specified for the index Db.

Method Detail

### getForeignStore

    public final DataStore getForeignStore()

  Returns the foreign store which has the primary key which matches the index key of this store.

### getDeleteAction

    public final int getDeleteAction()

  Returns a value indicating what action occurs when the foreign key is deleted. It must be one of the ON_DELETE_ constants.

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Copyright (c) 1996-2003 Sleepycat Software, Inc. - All rights reserved.