cascading.pipe.joiner

Interface Joiner

All Superinterfaces:

java.io.Serializable

All Known Implementing Classes:

BaseJoiner, BufferJoin, InnerJoin, LeftJoin, MixedJoin, OuterJoin, RightJoin

public interface Joiner
extends java.io.Serializable

Interface Joiner allows for custom join strategies against a CoGroup.

Joins perform based on the equality of the join keys. In the case of null values, Java treats two null values as equivalent. SQL does not treat null values as equal. To produce SQL like results in a given join, a new Comparator will need to be used on the joined values to prevent null from equaling null. As a convenience, see the NullNotEquivalentComparator class.

Method Summary

Methods

Modifier and Type	Method and Description
java.util.Iterator<Tuple>	getIterator(JoinerClosure closure) Returns an iterator that joins the given CoGroupClosure co-groups.
int	numJoins() Returns the number of joins this instance can handle.

Method Detail

getIterator

java.util.Iterator<Tuple> getIterator(JoinerClosure closure)

Returns an iterator that joins the given CoGroupClosure co-groups.

Parameters:

closure - of type GroupClosure

Returns:

an iterator

numJoins

int numJoins()

Returns the number of joins this instance can handle. A value of -1 denotes there is no limit.

Returns:

an int