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    
019    package org.apache.hadoop.mapred.lib.aggregate;
020    
021    import org.apache.hadoop.classification.InterfaceAudience;
022    import org.apache.hadoop.classification.InterfaceStability;
023    import org.apache.hadoop.io.Text;
024    import 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
039    public 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    }