001/**
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements.  See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership.  The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License.  You may obtain a copy of the License at
009 *
010 *     http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing, software
013 * distributed under the License is distributed on an "AS IS" BASIS,
014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015 * See the License for the specific language governing permissions and
016 * limitations under the License.
017 */
018
019package org.apache.hadoop.mapred.lib.aggregate;
020
021import org.apache.hadoop.classification.InterfaceAudience;
022import org.apache.hadoop.classification.InterfaceStability;
023import org.apache.hadoop.io.Text;
024import org.apache.hadoop.mapred.JobConf;
025
026/**
027 * This interface defines the contract a value aggregator descriptor must
028 * support. Such a descriptor can be configured with a JobConf object. Its main
029 * function is to generate a list of aggregation-id/value pairs. An aggregation
030 * id encodes an aggregation type which is used to guide the way to aggregate
031 * the value in the reduce/combiner phrase of an Aggregate based job.The mapper in
032 * an Aggregate based map/reduce job may create one or more of
033 * ValueAggregatorDescriptor objects at configuration time. For each input
034 * key/value pair, the mapper will use those objects to create aggregation
035 * id/value pairs.
036 */
037@InterfaceAudience.Public
038@InterfaceStability.Stable
039public interface ValueAggregatorDescriptor extends 
040    org.apache.hadoop.mapreduce.lib.aggregate.ValueAggregatorDescriptor {
041
042  public static final String TYPE_SEPARATOR = org.apache.hadoop.mapreduce.
043      lib.aggregate.ValueAggregatorDescriptor.TYPE_SEPARATOR;
044
045  public static final Text ONE = org.apache.hadoop.mapreduce.
046      lib.aggregate.ValueAggregatorDescriptor.ONE;
047
048  /**
049   * Configure the object
050   * 
051   * @param job
052   *          a JobConf object that may contain the information that can be used
053   *          to configure the object.
054   */
055  public void configure(JobConf job);
056}