org.apache.avro.mapred.AvroReducer 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
*
* 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,
* 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.Closeable;
import java.io.IOException;
import org.apache.hadoop.conf.Configured;
import org.apache.hadoop.mapred.JobConf;
import org.apache.hadoop.mapred.JobConfigurable;
import org.apache.hadoop.mapred.Reporter;
/**
* A reducer for Avro data.
*
*
* Applications should subclass this class and pass their subclass to
* {@link AvroJob#setReducerClass(JobConf, Class)} and perhaps
* {@link AvroJob#setCombinerClass(JobConf, Class)}. Subclasses override
* {@link #reduce(Object, Iterable, AvroCollector, Reporter)}.
*/
public class AvroReducer extends Configured implements JobConfigurable, Closeable {
private Pair outputPair;
/**
* Called with all map output values with a given key. By default, pairs key
* with each value, collecting {@link Pair} instances.
*/
@SuppressWarnings("unchecked")
public void reduce(K key, Iterable values, AvroCollector collector, Reporter reporter) throws IOException {
if (outputPair == null)
outputPair = new Pair<>(AvroJob.getOutputSchema(getConf()));
for (V value : values) {
outputPair.set(key, value);
collector.collect((OUT) outputPair);
}
}
/** Subclasses can override this as desired. */
@Override
public void close() throws IOException {
// no op
}
/** Subclasses can override this as desired. */
@Override
public void configure(JobConf jobConf) {
// no op
}
}