Package org.apache.tinkerpop.gremlin.process.computer

Class GraphComputerTest.MapReduceB

java.lang.Object

org.apache.tinkerpop.gremlin.process.computer.util.StaticMapReduce<Integer,Integer,Integer,Integer,List<Integer>>

org.apache.tinkerpop.gremlin.process.computer.GraphComputerTest.MapReduceB

All Implemented Interfaces:

Cloneable, MapReduce<Integer,Integer,Integer,Integer,List<Integer>>

Enclosing class:

GraphComputerTest

public static class GraphComputerTest.MapReduceB
extends StaticMapReduce<Integer,Integer,Integer,Integer,List<Integer>>

Nested Class Summary

Nested classes/interfaces inherited from interface org.apache.tinkerpop.gremlin.process.computer.MapReduce

MapReduce.MapEmitter<K,V>, MapReduce.NullObject, MapReduce.ReduceEmitter<OK,OV>, MapReduce.Stage

Field Summary

Fields inherited from interface org.apache.tinkerpop.gremlin.process.computer.MapReduce

MAP_REDUCE

Constructor Summary

Constructors

Constructor	Description
MapReduceB()

Method Summary

Modifier and Type	Method	Description
boolean	doStage(MapReduce.Stage stage)	A MapReduce job can be map-only, map-reduce-only, or map-combine-reduce.
List<Integer>	generateFinalResult(Iterator<KeyValue<Integer,Integer>> keyValues)	The key/value pairs emitted by reduce() (or map() in a map-only job) can be iterated to generate a local JVM Java object.
String	getMemoryKey()	The results of the MapReduce job are associated with a memory-key to ultimately be stored in Memory.
Optional<Comparator<Integer>>	getReduceKeySort()	If a Comparator is provided, then all pairs leaving the MapReduce.ReduceEmitter are sorted.
void	map(Vertex vertex, MapReduce.MapEmitter<Integer,Integer> emitter)	The map() method is logically executed at all vertices in the graph in parallel.
void	reduce(Integer key, Iterator<Integer> values, MapReduce.ReduceEmitter<Integer,Integer> emitter)	The reduce() method is logically on the "machine" the respective key hashes to.

Methods inherited from class org.apache.tinkerpop.gremlin.process.computer.util.StaticMapReduce

clone, equals, hashCode, storeState, toString

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.apache.tinkerpop.gremlin.process.computer.MapReduce

addResultToMemory, combine, getMapKeySort, loadState, workerEnd, workerStart

Constructor Detail

MapReduceB

public MapReduceB()

Method Detail

doStage

public boolean doStage(MapReduce.Stage stage)

Description copied from interface: MapReduce

A MapReduce job can be map-only, map-reduce-only, or map-combine-reduce. Before executing the particular stage, this method is called to determine if the respective stage is defined. This method should return true if the respective stage as a non-default method implementation.

Parameters:

stage - the stage to check for definition.

Returns:

whether that stage should be executed.

map

public void map(Vertex vertex,
                MapReduce.MapEmitter<Integer,Integer> emitter)

Description copied from interface: MapReduce

The map() method is logically executed at all vertices in the graph in parallel. The map() method emits key/value pairs given some analysis of the data in the vertices (and/or its incident edges). All MapReduce classes must at least provide an implementation of MapReduce#map(Vertex, MapEmitter).

Parameters:

vertex - the current vertex being map() processed.

emitter - the component that allows for key/value pairs to be emitted to the next stage.

reduce

public void reduce(Integer key,
                   Iterator<Integer> values,
                   MapReduce.ReduceEmitter<Integer,Integer> emitter)

Description copied from interface: MapReduce

The reduce() method is logically on the "machine" the respective key hashes to. The reduce() method combines all the values associated with the key and emits key/value pairs.

Parameters:

key - the key that has aggregated values

values - the aggregated values associated with the key

emitter - the component that allows for key/value pairs to be emitted as the final result.

getReduceKeySort

public Optional<Comparator<Integer>> getReduceKeySort()

Description copied from interface: MapReduce

If a Comparator is provided, then all pairs leaving the MapReduce.ReduceEmitter are sorted. If sorting is not required, then Optional.empty() should be returned as sorting is computationally expensive. The default implementation returns Optional.empty().

Returns:

an Optional of a comparator for sorting the reduce output.

getMemoryKey

public String getMemoryKey()

Description copied from interface: MapReduce

The results of the MapReduce job are associated with a memory-key to ultimately be stored in Memory.

Returns:

the memory key of the generated result object.

generateFinalResult

public List<Integer> generateFinalResult(Iterator<KeyValue<Integer,Integer>> keyValues)

Description copied from interface: MapReduce

The key/value pairs emitted by reduce() (or map() in a map-only job) can be iterated to generate a local JVM Java object.

Parameters:

keyValues - the key/value pairs that were emitted from reduce() (or map() in a map-only job)

Returns:

the resultant object formed from the emitted key/values.