Package org.apache.cassandra.utils

Class MergeIterator.Reducer<In,Out>

java.lang.Object

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

Enclosing class:

MergeIterator<In,Out>

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

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

Constructor Summary

Constructors

Constructor	Description
Reducer()

Method Summary

Modifier and Type	Method	Description
void	close()	May be overridden by implementations that require cleaning up after use
protected abstract Out	getReduced()
protected void	onKeyChange()	Called at the beginning of each new key, before any reduce is called.
abstract void	reduce(int idx, 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 Details

Reducer

public Reducer()

Method Details

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(int idx,
 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 beginning of each new key, before any reduce is called. To be overridden by implementing classes.

close

public void close()

May be overridden by implementations that require cleaning up after use