org.apache.cassandra.utils
Class MergeIterator.Reducer<In,Out>

java.lang.Object
  org.apache.cassandra.utils.MergeIterator.Reducer<In,Out>

Direct Known Subclasses:

CompactionIterable.Reducer

Enclosing class:

MergeIterator<In,Out>

public abstract static class MergeIterator.Reducer<In,Out>
extends java.lang.Object

Accumulator that collects values of type A, and outputs a value of type B.

Constructor Summary

MergeIterator.Reducer()

Method Summary

void	close() May be overridden by implementations that require cleaning up after use
protected abstract Out	getReduced()
protected void	onKeyChange() Called at the begining of each new key, before any reduce is called.
abstract void	reduce(In current) combine this object with the previous ones.
boolean	trivialReduceIsTrivial()

Methods inherited from class java.lang.Object

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

Constructor Detail

MergeIterator.Reducer

public MergeIterator.Reducer()

Method Detail

trivialReduceIsTrivial

public boolean trivialReduceIsTrivial()

Returns:

true if Out is the same as In for the case of a single source iterator

reduce

public abstract void reduce(In current)

combine this object with the previous ones. intermediate state is up to your implementation.

getReduced

protected abstract Out getReduced()

Returns:

The last object computed by reduce

onKeyChange

protected void onKeyChange()

Called at the begining of each new key, before any reduce is called. To be overriden by implementing classes.

close

public void close()

May be overridden by implementations that require cleaning up after use