/**
* 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.mapred.lib.aggregate;
import java.io.IOException;
import java.util.Iterator;
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.mapred.JobConf;
import org.apache.hadoop.mapred.OutputCollector;
import org.apache.hadoop.mapred.Reporter;
/**
* This class implements the generic combiner of Aggregate.
*/
@InterfaceAudience.Public
@InterfaceStability.Stable
public class ValueAggregatorCombiner<K1 extends WritableComparable,
V1 extends Writable>
extends ValueAggregatorJobBase<K1, V1> {
/**
* Combiner does not need to configure.
*/
public void configure(JobConf job) {
}
/** Combines values for a given key.
* @param key the key is expected to be a Text object, whose prefix indicates
* the type of aggregation to aggregate the values.
* @param values the values to combine
* @param output to collect combined values
*/
public void reduce(Text key, Iterator<Text> values,
OutputCollector<Text, Text> output, Reporter reporter) throws IOException {
String keyStr = key.toString();
int pos = keyStr.indexOf(ValueAggregatorDescriptor.TYPE_SEPARATOR);
String type = keyStr.substring(0, pos);
ValueAggregator aggregator = ValueAggregatorBaseDescriptor
.generateValueAggregator(type);
while (values.hasNext()) {
aggregator.addNextValue(values.next());
}
Iterator outputs = aggregator.getCombinerOutput().iterator();
while (outputs.hasNext()) {
Object v = outputs.next();
if (v instanceof Text) {
output.collect(key, (Text)v);
} else {
output.collect(key, new Text(v.toString()));
}
}
}
/**
* Do nothing.
*
*/
public void close() throws IOException {
}
/**
* Do nothing. Should not be called.
*
*/
public void map(K1 arg0, V1 arg1, OutputCollector<Text, Text> arg2,
Reporter arg3) throws IOException {
throw new IOException ("should not be called\n");
}
}