eu.stratosphere.arraymodel.functions

Class ReduceWithKeyFunction

java.lang.Object

eu.stratosphere.api.common.functions.AbstractFunction

eu.stratosphere.arraymodel.functions.AbstractArrayModelFunction

eu.stratosphere.arraymodel.functions.ReduceWithKeyFunction

All Implemented Interfaces:

Function, GenericReducer<Value[],Value[]>

public abstract class ReduceWithKeyFunction
extends AbstractArrayModelFunction
implements GenericReducer<Value[],Value[]>

The ReduceFunction must be extended to provide a reducer implementation which is called by a Reduce PACT. By definition, the Reduce PACT calls the reduce implementation once for each distinct key and all records that come with that key. For details on the Reduce PACT read the documentation of the PACT programming model.

The ReduceFunction extension must be parameterized with the types of its input keys.

For a reduce implementation, the reduce() method must be implemented.

Field Summary

Fields

Modifier and Type	Field and Description
static String	KEY_INDEX_PARAM_KEY
static String	KEY_TYPE_PARAM_KEY

Constructor Summary

Constructors

Constructor and Description
ReduceWithKeyFunction()

Method Summary

Methods

Modifier and Type	Method and Description
void	combine(Iterator<Value[]> records, Collector<Value[]> out)
void	combine(Value key, Iterator<Value[]> records, Collector<Value[]> out)
Method	getUDFMethod()
void	open(Configuration parameters)
void	reduce(Iterator<Value[]> records, Collector<Value[]> out)
abstract void	reduce(Value key, Iterator<Value[]> records, Collector<Value[]> out)

Methods inherited from class eu.stratosphere.arraymodel.functions.AbstractArrayModelFunction

getDataTypes

Methods inherited from class eu.stratosphere.api.common.functions.AbstractFunction

close, getIterationRuntimeContext, getRuntimeContext, setRuntimeContext

Methods inherited from class java.lang.Object

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

Methods inherited from interface eu.stratosphere.api.common.functions.Function

close, getRuntimeContext, setRuntimeContext

Field Detail

KEY_INDEX_PARAM_KEY

public static final String KEY_INDEX_PARAM_KEY

See Also:

Constant Field Values

KEY_TYPE_PARAM_KEY

public static final String KEY_TYPE_PARAM_KEY

See Also:

Constant Field Values

Constructor Detail

ReduceWithKeyFunction

public ReduceWithKeyFunction()

Method Detail

reduce

public abstract void reduce(Value key,
          Iterator<Value[]> records,
          Collector<Value[]> out)

combine

public void combine(Value key,
           Iterator<Value[]> records,
           Collector<Value[]> out)

reduce

public final void reduce(Iterator<Value[]> records,
          Collector<Value[]> out)
                  throws Exception

Specified by:

reduce in interface GenericReducer<Value[],Value[]>

Throws:

Exception

combine

public final void combine(Iterator<Value[]> records,
           Collector<Value[]> out)
                   throws Exception

Specified by:

combine in interface GenericReducer<Value[],Value[]>

Throws:

Exception

open

public void open(Configuration parameters)
          throws Exception

Specified by:

open in interface Function

Overrides:

open in class AbstractFunction

Throws:

Exception

getUDFMethod

public final Method getUDFMethod()

Specified by:

getUDFMethod in class AbstractArrayModelFunction