org.apache.hadoop.mapred.lib.aggregate
Interface ValueAggregatorDescriptor

All Superinterfaces:
ValueAggregatorDescriptor

@InterfaceAudience.Public
@InterfaceStability.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
static Text ONE
           
static String TYPE_SEPARATOR
           
 
Method Summary
 void configure(JobConf job)
          Configure the object
 
Methods inherited from interface org.apache.hadoop.mapreduce.lib.aggregate.ValueAggregatorDescriptor
configure, generateKeyValPairs
 

Field Detail

TYPE_SEPARATOR

static final String TYPE_SEPARATOR
See Also:
Constant Field Values

ONE

static final Text ONE
Method Detail

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.


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