org.compass.core.engine.subindex
Class ModuloSubIndexHash

java.lang.Object
  org.compass.core.engine.subindex.ModuloSubIndexHash

All Implemented Interfaces:

CompassConfigurable, SubIndexHash

public class ModuloSubIndexHash
extends Object
implements SubIndexHash, CompassConfigurable

Uses a hash function based on hash code computation of alias and ids, and using the modulo operation against the configured size.

The sub index name is prefix_(hashCode % size).

If using configuration, expects prefix as the setting name, and size as the modulo right hand side operation.

Author:

kimchy

Constructor Summary

ModuloSubIndexHash()
Constructs a new instance, will have to be configured.

ModuloSubIndexHash(String prefix, int size)
Constructs a new instance, using the given prefix and size.

Method Summary

void	configure(CompassSettings settings) Using configuration, expects prefix as the setting name, and size as the modulo right hand side operation.
String[]	getSubIndexes() Returns all the sub indexes possible, basically in the form of prefix_(0..size) (not including size).
String	mapSubIndex(String alias, Property[] ids) Computes the hash code of alias and all the ids, and then modulo it by size.
String	toString()

Methods inherited from class java.lang.Object

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

Constructor Detail

ModuloSubIndexHash

public ModuloSubIndexHash()

Constructs a new instance, will have to be configured.

ModuloSubIndexHash

public ModuloSubIndexHash(String prefix,
                          int size)

Constructs a new instance, using the given prefix and size.

Parameters:

prefix - The prefix sed for the sub index prefix name

size - The size the modulo will be used

Method Detail

configure

public void configure(CompassSettings settings)
               throws CompassException

Using configuration, expects prefix as the setting name, and size as the modulo right hand side operation.

Specified by:

configure in interface CompassConfigurable

Parameters:

settings - The setting to configure by

Throws:

CompassException

getSubIndexes

public String[] getSubIndexes()

Returns all the sub indexes possible, basically in the form of prefix_(0..size) (not including size).

Specified by:

getSubIndexes in interface SubIndexHash

mapSubIndex

public String mapSubIndex(String alias,
                          Property[] ids)
                   throws SearchEngineException

Computes the hash code of alias and all the ids, and then modulo it by size. The prefix is prepended (with an underscore), and the sub index is constructed. The formula is: prefix_(hashCode % size).

Specified by:

mapSubIndex in interface SubIndexHash

Parameters:

alias - The alias to compute the sub index by (optional)

ids - The set of ids to compute the sub index by (optional)

Returns:

The hashed sub index

Throws:

SearchEngineException

toString

public String toString()

Overrides:

toString in class Object