org.apache.avro.mapred.HadoopCombiner Maven / Gradle / Ivy
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* Licensed to the Apache Software Foundation (ASF) under one
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* distributed with this work for additional information
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* 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
*
* https://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,
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* See the License for the specific language governing permissions and
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*/
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;
}
@Override
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);
}
}