eu.stratosphere.arraymodel.functions

Class CoGroupFunction

java.lang.Object

eu.stratosphere.api.common.functions.AbstractFunction

eu.stratosphere.arraymodel.functions.AbstractArrayModelFunction

eu.stratosphere.arraymodel.functions.CoGroupFunction

All Implemented Interfaces:

Function, GenericCoGrouper<Value[],Value[],Value[]>

public abstract class CoGroupFunction
extends AbstractArrayModelFunction
implements GenericCoGrouper<Value[],Value[],Value[]>

The CoGroupFunction must be extended to provide a co-grouper implementation which is called by a CoGroup PACT. By definition, a CoGroup PACT has two input sets of records. It calls the co-grouper implementation once for each distinct key in its inputs. Together with the key, two iterators over the records containing that key from both inputs are handed to the coGroup() method. For details on the CoGroup PACT read the documentation of the PACT programming model.

The CoGroupFunction extension must be parameterized with the type of the key of its input.

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

Constructor Summary

Constructors

Constructor and Description
CoGroupFunction()

Method Summary

Methods

Modifier and Type	Method and Description
abstract void	coGroup(Iterator<Value[]> records1, Iterator<Value[]> records2, Collector<Value[]> out) This method must be implemented to provide a user implementation of a matcher.
Method	getUDFMethod()

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

getDataTypes

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

close, getIterationRuntimeContext, getRuntimeContext, open, 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.GenericCoGrouper

combineFirst, combineSecond

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

close, getRuntimeContext, open, setRuntimeContext

Constructor Detail

CoGroupFunction

public CoGroupFunction()

Method Detail

coGroup

public abstract void coGroup(Iterator<Value[]> records1,
           Iterator<Value[]> records2,
           Collector<Value[]> out)

This method must be implemented to provide a user implementation of a matcher. It is called for each two key-value pairs that share the same key and come from different inputs.

Specified by:

coGroup in interface GenericCoGrouper<Value[],Value[],Value[]>

Parameters:

records1 - The records from the first input which were paired with the key.

records2 - The records from the second input which were paired with the key.

out - A collector that collects all output pairs.

Throws:

Exception - Implementations may forward exceptions, which are caught by the runtime. When the runtime catches an exception, it aborts the task and lets the fail-over logic decide whether to retry the task execution.

getUDFMethod

public Method getUDFMethod()

Specified by:

getUDFMethod in class AbstractArrayModelFunction