Class HiLoOptimizer
- java.lang.Object
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- org.hibernate.id.enhanced.AbstractOptimizer
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- org.hibernate.id.enhanced.HiLoOptimizer
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- 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 thePooledOptimizer
.The general algorithms used to determine the bucket is:
upperLimit = (databaseValue * incrementSize) + 1
lowerLimit = upperLimit - incrementSize
As an example, consider a case with incrementSize of 20. Initially, the database holds 1:
upperLimit = (1 * 20) + 1 = 21
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:
upperLimit = (2 * 20) + 1 = 41
lowerLimit = 41 - 20 = 21
Note, 'value' always (after init) holds the next value to return
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Field Summary
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Fields inherited from class org.hibernate.id.enhanced.AbstractOptimizer
incrementSize, returnClass
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Constructor Summary
Constructors Constructor Description HiLoOptimizer(Class<?> returnClass, int incrementSize)
Constructs aHiLoOptimizer
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method 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
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Constructor Detail
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HiLoOptimizer
public HiLoOptimizer(Class<?> returnClass, int incrementSize)
Constructs aHiLoOptimizer
- Parameters:
returnClass
- The Java type of the values to be generatedincrementSize
- The increment size.
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Method Detail
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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.
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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.
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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.
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getLastValue
public IntegralDataTypeHolder getLastValue()
Getter for property 'lastValue'.Exposure intended for testing purposes.
- Returns:
- Value for property 'lastValue'.
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getHiValue
public IntegralDataTypeHolder getHiValue()
Getter for property 'upperLimit'.Exposure intended for testing purposes.
- Returns:
- Value for property 'upperLimit'.
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