| /* |
| * 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.pig.backend.hadoop.executionengine.mapReduceLayer; |
| |
| import java.io.IOException; |
| import java.util.Iterator; |
| |
| import org.apache.commons.logging.Log; |
| import org.apache.commons.logging.LogFactory; |
| import org.apache.hadoop.conf.Configuration; |
| import org.apache.hadoop.io.Writable; |
| import org.apache.hadoop.mapreduce.Reducer; |
| import org.apache.pig.impl.io.NullableTuple; |
| import org.apache.pig.impl.io.PigNullableWritable; |
| |
| /** |
| * A special implementation of combiner used only for distinct. This combiner |
| * does not even parse out the records. It just throws away duplicate values |
| * in the key in order to minimize the data being sent to the reduce. |
| */ |
| public class DistinctCombiner { |
| |
| public static class Combine |
| extends Reducer<PigNullableWritable, NullableTuple, PigNullableWritable, Writable> { |
| |
| private final Log log = LogFactory.getLog(getClass()); |
| |
| private static boolean firstTime = true; |
| |
| //@StaticDataCleanup |
| public static void staticDataCleanup() { |
| firstTime = true; |
| } |
| |
| @Override |
| protected void setup(Context context) throws IOException, InterruptedException { |
| super.setup(context); |
| Configuration jConf = context.getConfiguration(); |
| // Avoid log spamming |
| if (firstTime) { |
| log.info("Aliases being processed per job phase (AliasName[line,offset]): " + jConf.get("pig.alias.location")); |
| firstTime = false; |
| } |
| } |
| |
| /** |
| * The reduce function which removes values. |
| */ |
| @Override |
| protected void reduce(PigNullableWritable key, Iterable<NullableTuple> tupIter, Context context) |
| throws IOException, InterruptedException { |
| |
| // Take the first value and the key and collect |
| // just that. |
| Iterator<NullableTuple> iter = tupIter.iterator(); |
| NullableTuple val = iter.next(); |
| context.write(key, val); |
| } |
| |
| } |
| |
| } |