cascading.operation.filter

Class Sample

java.lang.Object

cascading.operation.BaseOperation<java.util.Random>

cascading.operation.filter.Sample

All Implemented Interfaces:

DeclaresResults, Filter<java.util.Random>, Operation<java.util.Random>, Traceable, java.io.Serializable

public class Sample
extends BaseOperation<java.util.Random>
implements Filter<java.util.Random>

Class Sample is a Filter that only allows the given fraction of Tuple instances to pass.

Where fraction is between 1 and zero, inclusive. Thus to sample 50% of the tuples in a stream, use the fraction 0.5.

By default, the seed is created at random on the constructor. This implies every branch using the Sample filter will return the same random stream based on that seed. So if this Sample instance is distributed into multiple systems against the same data, the result will be the same tuple stream. The alternative would be to make this Operation "not safe". See Operation.isSafe().

Conversely, if the same stream of random data is require across application executions, set the seed manually.

The seed is generated from the following code:

System.identityHashCode(this) * 2654435761L ^ System.currentTimeMillis()

Override makeSeed() to customize.

See Also:

Serialized Form

Field Summary

Fields inherited from class cascading.operation.BaseOperation

fieldDeclaration, numArgs, trace

Fields inherited from interface cascading.operation.Operation

ANY

Constructor Summary

Constructors

Constructor and Description
Sample(double fraction) Creates a new Sample that permits percent Tuples to pass.
Sample(long seed, double fraction) Creates a new Sample that permits percent Tuples to pass.

Method Summary

Methods

Modifier and Type	Method and Description
boolean	equals(java.lang.Object object)
double	getFraction()
long	getSeed()
int	hashCode()
boolean	isRemove(FlowProcess flowProcess, FilterCall<java.util.Random> filterCall) Method isRemove returns true if input should be removed from the tuple stream.
protected long	makeSeed()
void	prepare(FlowProcess flowProcess, OperationCall<java.util.Random> operationCall) Method prepare does nothing, and may safely be overridden.

Methods inherited from class cascading.operation.BaseOperation

cleanup, flush, getFieldDeclaration, getNumArgs, getTrace, isSafe, printOperationInternal, toString, toStringInternal

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface cascading.operation.Operation

cleanup, flush, getFieldDeclaration, getNumArgs, isSafe

Constructor Detail

Sample

@ConstructorProperties(value="fraction")
public Sample(double fraction)

Creates a new Sample that permits percent Tuples to pass.

Parameters:

fraction - of type double

Sample

@ConstructorProperties(value={"seed","fraction"})
public Sample(long seed,
                            double fraction)

Creates a new Sample that permits percent Tuples to pass. The given seed value seeds the random number generator.

Parameters:

seed - of type long

fraction - of type double

Method Detail

getSeed

public long getSeed()

getFraction

public double getFraction()

makeSeed

protected long makeSeed()

prepare

public void prepare(FlowProcess flowProcess,
           OperationCall<java.util.Random> operationCall)

Description copied from class: BaseOperation

Method prepare does nothing, and may safely be overridden.

Specified by:

prepare in interface Operation<java.util.Random>

Overrides:

prepare in class BaseOperation<java.util.Random>

isRemove

public boolean isRemove(FlowProcess flowProcess,
               FilterCall<java.util.Random> filterCall)

Description copied from interface: Filter

Method isRemove returns true if input should be removed from the tuple stream.

Specified by:

isRemove in interface Filter<java.util.Random>

Parameters:

flowProcess - of type FlowProcess

filterCall - of type FilterCall

Returns:

boolean

equals

public boolean equals(java.lang.Object object)

Overrides:

equals in class BaseOperation<java.util.Random>

hashCode

public int hashCode()

Overrides:

hashCode in class BaseOperation<java.util.Random>