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 java.io.IOException;
022    import java.util.Iterator;
023    
024    import org.apache.hadoop.classification.InterfaceAudience;
025    import org.apache.hadoop.classification.InterfaceStability;
026    import org.apache.hadoop.io.Text;
027    import org.apache.hadoop.io.Writable;
028    import org.apache.hadoop.io.WritableComparable;
029    import org.apache.hadoop.mapred.OutputCollector;
030    import org.apache.hadoop.mapred.Reporter;
031    
032    /**
033     * This class implements the generic reducer of Aggregate.
034     * 
035     * @deprecated Use 
036     * {@link org.apache.hadoop.mapreduce.lib.aggregate.ValueAggregatorReducer}
037     * instead
038     */
039    @Deprecated
040    @InterfaceAudience.Public
041    @InterfaceStability.Stable
042    public class ValueAggregatorReducer<K1 extends WritableComparable,
043                                        V1 extends Writable>
044      extends ValueAggregatorJobBase<K1, V1> {
045    
046      /**
047       * @param key
048       *          the key is expected to be a Text object, whose prefix indicates
049       *          the type of aggregation to aggregate the values. In effect, data
050       *          driven computing is achieved. It is assumed that each aggregator's
051       *          getReport method emits appropriate output for the aggregator. This
052       *          may be further customiized.
053       * @value the values to be aggregated
054       */
055      public void reduce(Text key, Iterator<Text> values,
056                         OutputCollector<Text, Text> output, Reporter reporter) throws IOException {
057        String keyStr = key.toString();
058        int pos = keyStr.indexOf(ValueAggregatorDescriptor.TYPE_SEPARATOR);
059        String type = keyStr.substring(0, pos);
060        keyStr = keyStr.substring(pos
061                                  + ValueAggregatorDescriptor.TYPE_SEPARATOR.length());
062    
063        ValueAggregator aggregator = ValueAggregatorBaseDescriptor
064          .generateValueAggregator(type);
065        while (values.hasNext()) {
066          aggregator.addNextValue(values.next());
067        }
068    
069        String val = aggregator.getReport();
070        key = new Text(keyStr);
071        output.collect(key, new Text(val));
072      }
073    
074      /**
075       * Do nothing. Should not be called
076       */
077      public void map(K1 arg0, V1 arg1, OutputCollector<Text, Text> arg2,
078                      Reporter arg3) throws IOException {
079        throw new IOException ("should not be called\n");
080      }
081    }