1 | /** |
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2 | * Licensed to the Apache Software Foundation (ASF) under one |
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3 | * or more contributor license agreements. See the NOTICE file |
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4 | * distributed with this work for additional information |
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5 | * regarding copyright ownership. The ASF licenses this file |
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6 | * to you under the Apache License, Version 2.0 (the |
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7 | * "License"); you may not use this file except in compliance |
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8 | * with the License. You may obtain a copy of the License at |
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9 | * |
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10 | * http://www.apache.org/licenses/LICENSE-2.0 |
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11 | * |
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12 | * Unless required by applicable law or agreed to in writing, software |
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13 | * distributed under the License is distributed on an "AS IS" BASIS, |
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14 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
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15 | * See the License for the specific language governing permissions and |
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16 | * limitations under the License. |
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17 | */ |
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18 | |
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19 | package org.apache.hadoop.mapreduce.lib.partition; |
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20 | |
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21 | import org.apache.hadoop.mapreduce.Partitioner; |
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22 | |
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23 | /** Partition keys by their {@link Object#hashCode()}. */ |
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24 | public class HashPartitioner<K, V> extends Partitioner<K, V> { |
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25 | |
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26 | /** Use {@link Object#hashCode()} to partition. */ |
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27 | public int getPartition(K key, V value, |
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28 | int numReduceTasks) { |
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29 | return (key.hashCode() & Integer.MAX_VALUE) % numReduceTasks; |
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30 | } |
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31 | |
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32 | } |
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