Package org.apache.hadoop.mapred.lib.aggregate

Interface ValueAggregatorDescriptor

All Superinterfaces:

ValueAggregatorDescriptor

All Known Implementing Classes:

UserDefinedValueAggregatorDescriptor, ValueAggregatorBaseDescriptor

@Public
@Stable
public interface ValueAggregatorDescriptor
extends ValueAggregatorDescriptor

This interface defines the contract a value aggregator descriptor must support. Such a descriptor can be configured with a JobConf object. Its main function is to generate a list of aggregation-id/value pairs. An aggregation id encodes an aggregation type which is used to guide the way to aggregate the value in the reduce/combiner phrase of an Aggregate based job.The mapper in an Aggregate based map/reduce job may create one or more of ValueAggregatorDescriptor objects at configuration time. For each input key/value pair, the mapper will use those objects to create aggregation id/value pairs.

Field Summary

Fields

Modifier and Type	Field	Description
static final Text	ONE
static final String	TYPE_SEPARATOR

Method Summary

Modifier and Type	Method	Description
void	configure(JobConf job)	Configure the object

Methods inherited from interface org.apache.hadoop.mapreduce.lib.aggregate.ValueAggregatorDescriptor

configure, generateKeyValPairs

Field Details

TYPE_SEPARATOR

static final String TYPE_SEPARATOR

See Also:

• Constant Field Values

ONE

static final Text ONE

Method Details

configure

void configure(JobConf job)

Configure the object

Parameters:

job - a JobConf object that may contain the information that can be used to configure the object.