org.apache.avro.mapred.HadoopCombiner Maven / Gradle / Ivy
/**
* 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.avro.mapred;
import java.io.IOException;
import org.apache.hadoop.mapred.JobConf;
import org.apache.hadoop.mapred.OutputCollector;
import org.apache.hadoop.util.ReflectionUtils;
/** Bridge between a {@link org.apache.hadoop.mapred.Reducer} and an {@link
* AvroReducer} used when combining. When combining, map output pairs must be
* split before they're collected. */
class HadoopCombiner
extends HadoopReducerBase,AvroKey,AvroValue> {
@Override @SuppressWarnings("unchecked")
protected AvroReducer> getReducer(JobConf conf) {
return ReflectionUtils.newInstance
(conf.getClass(AvroJob.COMBINER, AvroReducer.class, AvroReducer.class),
conf);
}
private class PairCollector extends AvroCollector> {
private final AvroKey keyWrapper = new AvroKey(null);
private final AvroValue valueWrapper = new AvroValue(null);
private OutputCollector,AvroValue> collector;
public PairCollector(OutputCollector,AvroValue> collector) {
this.collector = collector;
}
public void collect(Pair datum) throws IOException {
keyWrapper.datum(datum.key()); // split the Pair
valueWrapper.datum(datum.value());
collector.collect(keyWrapper, valueWrapper);
}
}
@Override
protected AvroCollector>
getCollector(OutputCollector,AvroValue> collector) {
return new PairCollector(collector);
}
}