com.coyotegulch.jisp

Class HashIndex

java.lang.Object

com.coyotegulch.jisp.HashIndex

All Implemented Interfaces:

ObjectIndex

Deprecated.

As of Jisp versioon 2.5.0, the HashIndex class is deprecated; it will be replaced in Jisp 3.0 by a more efficient and simpler hash-based index.

public class HashIndex
extends java.lang.Object
implements ObjectIndex

HashIndex associates a key value with a reference to persistent data, using a disk-based hash table. The index assumes that the position of a serializable object is constant, regardless of the actual meaning of the long position. In general, the position represents the location (file pointer) of a Serializable object in an IndexedObjectDatabase.

Use the IndexedObjectDatabase.attachIndex method to attach a BTreeIndex to a database. A database updates all attached indexes when it writes or removes objects from its file.

This class should not be used in new code. It was originally design to illustrate algorithms, and it suffers from a number of performance problems. A better, more efficient hash-bvased index will be introduced in version 3.0 of Jisp.

See Also:

ObjectIndex

Constructor Summary

Constructors

Constructor and Description
HashIndex(java.lang.String name) Deprecated. Opens a file as a HashIndex.
HashIndex(java.lang.String name, int numBuckets, int maxRecords, KeyObject nullKey) Deprecated. Creates the file as a HashIndex.

Method Summary

Modifier and Type	Method and Description
void	close() Deprecated.
long	findKey(KeyObject key) Deprecated. Find the position of the object associated with a given key.
void	insertKey(KeyObject key, long pos) Deprecated. Insert a key into the database, associating a record position with the given key.
void	optimize() Deprecated. Improves the performance of this HashIndex by optimizing the index contents.
void	removeKey(KeyObject key) Deprecated. Removes the given key from the index.
void	replaceKey(KeyObject key, long pos) Deprecated. Replace the reference pos for the given key.
void	storeKey(KeyObject key, long pos) Deprecated. If the key already exists, replace the reference pos for the given key.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

HashIndex

public HashIndex(java.lang.String name,
                 int numBuckets,
                 int maxRecords,
                 KeyObject nullKey)
          throws java.io.IOException,
                 java.lang.ClassNotFoundException

Deprecated.

Creates the file as a HashIndex. The initial length of each list is based on numBuckets and macRecords. The null key is a "blank" key; obtain a null key for any KeyObject type by calling the KeyObject.makeNullKey method.

Parameters:

name - The name of the external index file to be opened.

numBuckets - The number of lists in the hash table; this is also known as the "hash factor." Use prime numbers to limit the number of collisions and increase the efficiency of the index.

maxRecords - The expected number of records to be indexed. This is not a limit on the index size; the index will expand to handle up to 2 billion records. However, the best performance is obtained by setting maxRecords to a value that reflects the expected size of the database.

nullKey - The null key serves two purposes: to identify a blank table entry, and to perform type-checking on new keys added to the index. All keys added to the index must have the same type as nullkey.

Throws:

java.io.IOException - when an I/O exception is thrown by an underlying java.io.* class

java.lang.ClassNotFoundException - for a casting error, usually when a persistent object or index does match the expected type

See Also:

KeyObject

HashIndex

public HashIndex(java.lang.String name)
          throws java.io.IOException,
                 java.lang.ClassNotFoundException

Deprecated.

Opens a file as a HashIndex.

Parameters:

name - The name of the external index file to be opened.

Throws:

java.io.IOException - when an I/O exception is thrown by an underlying java.io.* class

java.lang.ClassNotFoundException - for a casting error, usually when a persistent object or index does match the expected type

Method Detail

insertKey

public void insertKey(KeyObject key,
                      long pos)
               throws java.io.IOException,
                      DuplicateKey,
                      java.lang.ClassNotFoundException

Deprecated.

Insert a key into the database, associating a record position with the given key.

Specified by:

insertKey in interface ObjectIndex

Parameters:

key - A key identifying the record to be read.

pos - File position of record associated with key

Throws:

java.io.IOException - when an I/O exception is thrown by an underlying java.io.* class

java.lang.ClassNotFoundException - for a casting error, usually when a persistent object or index does match the expected type

DuplicateKey - when inserting a duplicate key into an index that does not support duplicates

See Also:

DuplicateKey, KeyObject

replaceKey

public void replaceKey(KeyObject key,
                       long pos)
                throws java.io.IOException,
                       java.lang.ClassNotFoundException

Deprecated.

Replace the reference pos for the given key.

Specified by:

replaceKey in interface ObjectIndex

Parameters:

key - A key identifying the record to be read.

pos - File position of record associated with key

Throws:

java.io.IOException - when an I/O exception is thrown by an underlying java.io.* class

java.lang.ClassNotFoundException - for a casting error, usually when a persistent object or index does match the expected type

KeyNotFound - when the specified key can not be found in the index

See Also:

KeyNotFound, KeyObject

storeKey

public void storeKey(KeyObject key,
                     long pos)
              throws java.io.IOException,
                     java.lang.ClassNotFoundException

Deprecated.

If the key already exists, replace the reference pos for the given key. Otherwise, insert a key into the database, associating a record position with the given key.

Specified by:

storeKey in interface ObjectIndex

Parameters:

key - A key identifying the record to be read.

pos - File position of record associated with key

Throws:

java.io.IOException - when an I/O exception is thrown by an underlying java.io.* class

java.lang.ClassNotFoundException - for a casting error, usually when a persistent object or index does match the expected type

See Also:

KeyObject

findKey

public long findKey(KeyObject key)
             throws KeyNotFound,
                    java.io.IOException,
                    java.lang.ClassNotFoundException

Deprecated.

Find the position of the object associated with a given key.

Specified by:

findKey in interface ObjectIndex

Parameters:

key - A key identifying the record to be read.

Returns:

The position of the record associated with key.

Throws:

java.io.IOException - when an I/O exception is thrown by an underlying java.io.* class

java.lang.ClassNotFoundException - for a casting error, usually when a persistent object or index does match the expected type

KeyNotFound - when the specified key can not be found in the index

See Also:

KeyNotFound, KeyObject

removeKey

public void removeKey(KeyObject key)
               throws java.io.IOException,
                      java.lang.ClassNotFoundException

Deprecated.

Removes the given key from the index.

Specified by:

removeKey in interface ObjectIndex

Parameters:

key - A key identifying the record to be read.

Throws:

java.io.IOException - when an I/O exception is thrown by an underlying java.io.* class

java.lang.ClassNotFoundException - for a casting error, usually when a persistent object or index does match the expected type

KeyNotFound - when the specified key can not be found in the index

See Also:

KeyNotFound, KeyObject

optimize

public void optimize()
              throws java.io.IOException,
                     java.lang.ClassNotFoundException

Deprecated.

Improves the performance of this HashIndex by optimizing the index contents.

Throws:

java.io.IOException

java.lang.ClassNotFoundException

close

public void close()
           throws java.io.IOException

Deprecated.

Throws:

java.io.IOException