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org.apache.crunch.lib.join
Class MapsideJoinStrategy<K,U,V>

java.lang.Object
  org.apache.crunch.lib.join.MapsideJoinStrategy<K,U,V>

All Implemented Interfaces:

Serializable, JoinStrategy<K,U,V>

public class MapsideJoinStrategy<K,U,V>
extends Object
implements JoinStrategy<K,U,V>

Utility for doing map side joins on a common key between two PTables.

A map side join is an optimized join which doesn't use a reducer; instead, the right side of the join is loaded into memory and the join is performed in a mapper. This style of join has the important implication that the output of the join is not sorted, which is the case with a conventional (reducer-based) join.

See Also:

Serialized Form

Constructor Summary

MapsideJoinStrategy()

Method Summary

PTable<K,Pair<U,V>>

join(PTable<K,U> left, PTable<K,V> right, JoinType joinType) Join two tables with the given join type.

Methods inherited from class java.lang.Object

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

Constructor Detail

MapsideJoinStrategy

public MapsideJoinStrategy()

Method Detail

join

public PTable<K,Pair<U,V>> join(PTable<K,U> left,
                                PTable<K,V> right,
                                JoinType joinType)

Description copied from interface: JoinStrategy

Join two tables with the given join type.

Specified by:

join in interface JoinStrategy<K,U,V>

Parameters:

left - left table to be joined

right - right table to be joined

joinType - type of join to perform

Returns:

joined tables