- すべてのスーパーインタフェース:
- 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.