org.apache.hadoop.mapreduce.lib.aggregate

Class UniqValueCount

java.lang.Object

org.apache.hadoop.mapreduce.lib.aggregate.UniqValueCount

All Implemented Interfaces:

ValueAggregator<Object>

Direct Known Subclasses:

UniqValueCount

@InterfaceAudience.Public
@InterfaceStability.Stable
public class UniqValueCount
extends Object
implements ValueAggregator<Object>

This class implements a value aggregator that dedupes a sequence of objects.

Field Summary

Fields

Modifier and Type	Field and Description
static String	MAX_NUM_UNIQUE_VALUES

Constructor Summary

Constructors

Constructor and Description
UniqValueCount() the default constructor
UniqValueCount(long maxNum) constructor

Method Summary

Methods

Modifier and Type	Method and Description
void	addNextValue(Object val) add a value to the aggregator
ArrayList<Object>	getCombinerOutput()
String	getReport()
Set<Object>	getUniqueItems()
void	reset() reset the aggregator
long	setMaxItems(long n) Set the limit on the number of unique values

Methods inherited from class java.lang.Object

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

Field Detail

MAX_NUM_UNIQUE_VALUES

public static final String MAX_NUM_UNIQUE_VALUES

See Also:

Constant Field Values

Constructor Detail

UniqValueCount

public UniqValueCount()

the default constructor

UniqValueCount

public UniqValueCount(long maxNum)

constructor

Parameters:

maxNum - the limit in the number of unique values to keep.

Method Detail

setMaxItems

public long setMaxItems(long n)

Set the limit on the number of unique values

Parameters:

n - the desired limit on the number of unique values

Returns:

the new limit on the number of unique values

addNextValue

public void addNextValue(Object val)

add a value to the aggregator

Specified by:

addNextValue in interface ValueAggregator<Object>

Parameters:

val - an object.

getReport

public String getReport()

Specified by:

getReport in interface ValueAggregator<Object>

Returns:

return the number of unique objects aggregated

getUniqueItems

public Set<Object> getUniqueItems()

Returns:

the set of the unique objects

reset

public void reset()

reset the aggregator

Specified by:

reset in interface ValueAggregator<Object>

getCombinerOutput

public ArrayList<Object> getCombinerOutput()

Specified by:

getCombinerOutput in interface ValueAggregator<Object>

Returns:

return an array of the unique objects. The return value is expected to be used by the a combiner.