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* 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.partitioners;
import java.util.Map;
import org.apache.hadoop.conf.Configurable;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.io.Writable;
import org.apache.hadoop.mapreduce.Partitioner;
import org.apache.pig.backend.executionengine.ExecException;
import org.apache.pig.backend.hadoop.executionengine.mapReduceLayer.PigMapReduce;
import org.apache.pig.backend.hadoop.executionengine.util.MapRedUtil;
import org.apache.pig.data.DataType;
import org.apache.pig.data.Tuple;
import org.apache.pig.data.TupleFactory;
import org.apache.pig.impl.io.NullablePartitionWritable;
import org.apache.pig.impl.io.NullableTuple;
import org.apache.pig.impl.io.PigNullableWritable;
import org.apache.pig.impl.util.Pair;
import com.google.common.collect.Maps;
/**
* This class is used by skewed join. For the partitioned table, the skewedpartitioner reads the key
* distribution data from the sampler file and returns the reducer index in a round robin fashion.
* For ex: if the key distribution file contains (k1, 5, 3) as an entry, reducers from 5 to 3 are returned
* in a round robin manner.
*/
public class SkewedPartitioner extends Partitioner<PigNullableWritable, Writable> implements Configurable {
protected static final TupleFactory tf = TupleFactory.getInstance();
protected Map<Tuple, Pair<Integer, Integer>> reducerMap = Maps.newHashMap();
protected Integer totalReducers = -1;
protected boolean inited = false;
private Map<Tuple, Integer> currentIndexMap = Maps.newHashMap();
private Configuration conf;
@Override
public int getPartition(PigNullableWritable wrappedKey, Writable value, int numPartitions) {
if (!inited) {
init();
}
// for streaming tables, return the partition index blindly
if (wrappedKey instanceof NullablePartitionWritable &&
(((NullablePartitionWritable)wrappedKey).getPartition()) != -1) {
return ((NullablePartitionWritable)wrappedKey).getPartition();
}
// for partition table, compute the index based on the sampler output
Pair <Integer, Integer> indexes;
Integer curIndex = -1;
Tuple keyTuple = tf.newTuple(1);
// extract the key from nullablepartitionwritable
PigNullableWritable key = ((NullablePartitionWritable) wrappedKey).getKey();
try {
keyTuple.set(0, key.getValueAsPigType());
} catch (ExecException e) {
return -1;
}
// if the key is not null and key
if (key instanceof NullableTuple && key.getValueAsPigType() != null) {
keyTuple = (Tuple)key.getValueAsPigType();
}
// if the partition file is empty, use numPartitions
totalReducers = (totalReducers > 0) ? totalReducers : numPartitions;
indexes = reducerMap.get(keyTuple);
// if the reducerMap does not contain the key, do the default hash based partitioning
if (indexes == null) {
return (Math.abs(keyTuple.hashCode() % totalReducers));
}
if (currentIndexMap.containsKey(keyTuple)) {
curIndex = currentIndexMap.get(keyTuple);
}
if (curIndex >= (indexes.first + indexes.second) || curIndex == -1) {
curIndex = indexes.first;
} else {
curIndex++;
}
// set it in the map
currentIndexMap.put(keyTuple, curIndex);
return (curIndex % totalReducers);
}
@Override
public void setConf(Configuration job) {
conf = job;
PigMapReduce.sJobConfInternal.set(conf);
PigMapReduce.sJobConf = conf;
}
@Override
public Configuration getConf() {
return conf;
}
protected void init() {
String keyDistFile = conf.get("pig.keyDistFile", "");
if (keyDistFile.length() == 0) {
throw new RuntimeException(this.getClass().getSimpleName() +
" used but no key distribution found");
}
try {
Integer [] redCnt = new Integer[1];
reducerMap = MapRedUtil.loadPartitionFileFromLocalCache(
keyDistFile, redCnt, DataType.TUPLE, conf);
// check if the partition file is empty
totalReducers = (redCnt[0] == null) ? -1 : redCnt[0];
} catch (Exception e) {
throw new RuntimeException(e);
}
inited = true;
}
}