/** | |
* 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.hadoop.contrib.index.example; | |
import org.apache.hadoop.contrib.index.mapred.DocumentID; | |
import org.apache.hadoop.contrib.index.mapred.IDistributionPolicy; | |
import org.apache.hadoop.contrib.index.mapred.Shard; | |
/** | |
* Choose a shard for each insert or delete based on document id hashing. Do | |
* NOT use this distribution policy when the number of shards changes. | |
*/ | |
public class HashingDistributionPolicy implements IDistributionPolicy { | |
private int numShards; | |
/* (non-Javadoc) | |
* @see org.apache.hadoop.contrib.index.mapred.IDistributionPolicy#init(org.apache.hadoop.contrib.index.mapred.Shard[]) | |
*/ | |
public void init(Shard[] shards) { | |
numShards = shards.length; | |
} | |
/* (non-Javadoc) | |
* @see org.apache.hadoop.contrib.index.mapred.IDistributionPolicy#chooseShardForInsert(org.apache.hadoop.contrib.index.mapred.DocumentID) | |
*/ | |
public int chooseShardForInsert(DocumentID key) { | |
int hashCode = key.hashCode(); | |
return hashCode >= 0 ? hashCode % numShards : (-hashCode) % numShards; | |
} | |
/* (non-Javadoc) | |
* @see org.apache.hadoop.contrib.index.mapred.IDistributionPolicy#chooseShardForDelete(org.apache.hadoop.contrib.index.mapred.DocumentID) | |
*/ | |
public int chooseShardForDelete(DocumentID key) { | |
int hashCode = key.hashCode(); | |
return hashCode >= 0 ? hashCode % numShards : (-hashCode) % numShards; | |
} | |
} |