org.apache.crunch.lib

Class Shard

java.lang.Object

org.apache.crunch.lib.Shard

public class Shard
extends Object

Utilities for controlling how the data in a PCollection is balanced across reducers and output files.

Constructor Summary

Constructors

Constructor and Description
Shard()

Method Summary

Methods

Modifier and Type	Method and Description
static <T> PCollection<T>	shard(PCollection<T> pc, int numPartitions) Creates a PCollection<T> that has the same contents as its input argument but will be written to a fixed number of output files.

Methods inherited from class java.lang.Object

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

Constructor Detail

Shard

public Shard()

Method Detail

shard

public static <T> PCollection<T> shard(PCollection<T> pc,
                       int numPartitions)

Creates a PCollection<T> that has the same contents as its input argument but will be written to a fixed number of output files. This is useful for map-only jobs that process lots of input files but only write out a small amount of input per task.

Parameters:

pc - The PCollection<T> to rebalance

numPartitions - The number of output partitions to create

Returns:

A rebalanced PCollection<T> with the same contents as the input