HashingDistributionPolicy.java
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上传日期:2018-01-08
资源大小:41811k
文件大小:2k
源码类别:
网格计算
开发平台:
Java
- /**
- * 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;
- }
- }