org.hibernate.id.enhanced

Class HiLoOptimizer

java.lang.Object

org.hibernate.id.enhanced.AbstractOptimizer

org.hibernate.id.enhanced.HiLoOptimizer

All Implemented Interfaces:

Optimizer

public class HiLoOptimizer
extends AbstractOptimizer

Optimizer which applies a 'hilo' algorithm in memory to achieve optimization.

A 'hilo' algorithm is simply a means for a single value stored in the database to represent a "bucket" of possible, contiguous values. The database value identifies which particular bucket we are on.

This database value must be paired with another value that defines the size of the bucket; the number of possible values available. The incrementSize serves this purpose. The naming here is meant more for consistency in that this value serves the same purpose as the increment supplied to the PooledOptimizer.

The general algorithms used to determine the bucket are:

1. upperLimit = (databaseValue * incrementSize) + 1
2. lowerLimit = upperLimit - incrementSize

As an example, consider a case with incrementSize of 20. Initially the database holds 1:

1. upperLimit = (1 * 20) + 1 = 21
2. lowerLimit = 21 - 20 = 1

From there we increment the value from lowerLimit until we reach the upperLimit, at which point we would define a new bucket. The database now contains 2, though incrementSize remains unchanged:

1. upperLimit = (2 * 20) + 1 = 41
2. lowerLimit = 41 - 20 = 21

And so on...

Note, 'value' always (after init) holds the next value to return

Author:

Steve Ebersole

Field Summary

Fields inherited from class org.hibernate.id.enhanced.AbstractOptimizer

incrementSize, returnClass

Constructor Summary

Constructors

Constructor and Description
HiLoOptimizer(Class returnClass, int incrementSize) Constructs a HiLoOptimizer

Method Summary

Modifier and Type	Method and Description
boolean	applyIncrementSizeToSourceValues() Are increments to be applied to the values stored in the underlying value source?
Serializable	generate(AccessCallback callback) Generate an identifier value accounting for this specific optimization.
IntegralDataTypeHolder	getHiValue() Getter for property 'upperLimit'.
IntegralDataTypeHolder	getLastSourceValue() A common means to access the last value obtained from the underlying source.
IntegralDataTypeHolder	getLastValue() Getter for property 'lastValue'.

Methods inherited from class org.hibernate.id.enhanced.AbstractOptimizer

getIncrementSize, getReturnClass

Methods inherited from class java.lang.Object

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

Constructor Detail

HiLoOptimizer

public HiLoOptimizer(Class returnClass,
                     int incrementSize)

Constructs a HiLoOptimizer

Parameters:

returnClass - The Java type of the values to be generated

incrementSize - The increment size.

Method Detail

generate

public Serializable generate(AccessCallback callback)

Description copied from interface: Optimizer

Generate an identifier value accounting for this specific optimization. All known implementors are synchronized. Consider carefully if a new implementation could drop this requirement.

Parameters:

callback - Callback to access the underlying value source.

Returns:

The generated identifier value.

getLastSourceValue

public IntegralDataTypeHolder getLastSourceValue()

Description copied from interface: Optimizer

A common means to access the last value obtained from the underlying source. This is intended for testing purposes, since accessing the underlying database source directly is much more difficult.

Returns:

The last value we obtained from the underlying source; null indicates we have not yet consulted with the source.

applyIncrementSizeToSourceValues

public boolean applyIncrementSizeToSourceValues()

Description copied from interface: Optimizer

Are increments to be applied to the values stored in the underlying value source?

Returns:

True if the values in the source are to be incremented according to the defined increment size; false otherwise, in which case the increment is totally an in memory construct.

getLastValue

public IntegralDataTypeHolder getLastValue()

Getter for property 'lastValue'.

Exposure intended for testing purposes.

Returns:

Value for property 'lastValue'.

getHiValue

public IntegralDataTypeHolder getHiValue()

Getter for property 'upperLimit'.

Exposure intended for testing purposes.

Returns:

Value for property 'upperLimit'.