| /** |
| * Licensed to the Apache Software Foundation (ASF) under one |
| * or more contributor license agreements. See the NOTICE file |
| * distributed with this work for additional information |
| * regarding copyright ownership. The ASF licenses this file |
| * to you under the Apache License, Version 2.0 (the |
| * "License"); you may not use this file except in compliance |
| * with the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| package org.apache.hadoop.mapreduce.lib.aggregate; |
| |
| import java.io.IOException; |
| |
| import org.apache.hadoop.classification.InterfaceAudience; |
| import org.apache.hadoop.classification.InterfaceStability; |
| import org.apache.hadoop.io.Text; |
| import org.apache.hadoop.io.Writable; |
| import org.apache.hadoop.io.WritableComparable; |
| import org.apache.hadoop.mapreduce.Reducer; |
| |
| /** |
| * This class implements the generic reducer of Aggregate. |
| */ |
| @InterfaceAudience.Public |
| @InterfaceStability.Stable |
| public class ValueAggregatorReducer<K1 extends WritableComparable<?>, |
| V1 extends Writable> |
| extends Reducer<Text, Text, Text, Text> { |
| |
| public void setup(Context context) |
| throws IOException, InterruptedException { |
| ValueAggregatorJobBase.setup(context.getConfiguration()); |
| } |
| |
| /** |
| * @param key |
| * the key is expected to be a Text object, whose prefix indicates |
| * the type of aggregation to aggregate the values. In effect, data |
| * driven computing is achieved. It is assumed that each aggregator's |
| * getReport method emits appropriate output for the aggregator. This |
| * may be further customized. |
| * @param values the values to be aggregated |
| * @param context |
| */ |
| public void reduce(Text key, Iterable<Text> values, |
| Context context) throws IOException, InterruptedException { |
| String keyStr = key.toString(); |
| int pos = keyStr.indexOf(ValueAggregatorDescriptor.TYPE_SEPARATOR); |
| String type = keyStr.substring(0, pos); |
| keyStr = keyStr.substring(pos + |
| ValueAggregatorDescriptor.TYPE_SEPARATOR.length()); |
| long uniqCount = context.getConfiguration(). |
| getLong(UniqValueCount.MAX_NUM_UNIQUE_VALUES, Long.MAX_VALUE); |
| ValueAggregator aggregator = ValueAggregatorBaseDescriptor |
| .generateValueAggregator(type, uniqCount); |
| for (Text value : values) { |
| aggregator.addNextValue(value); |
| } |
| |
| String val = aggregator.getReport(); |
| key = new Text(keyStr); |
| context.write(key, new Text(val)); |
| } |
| } |