| /** |
| * 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.utils.join; |
| |
| import java.io.IOException; |
| import java.util.Iterator; |
| |
| import org.apache.hadoop.io.Text; |
| import org.apache.hadoop.mapred.JobConf; |
| import org.apache.hadoop.mapred.OutputCollector; |
| import org.apache.hadoop.mapred.Reporter; |
| import org.apache.hadoop.mapreduce.MRJobConfig; |
| |
| /** |
| * This abstract class serves as the base class for the mapper class of a data |
| * join job. This class expects its subclasses to implement methods for the |
| * following functionalities: |
| * |
| * 1. Compute the source tag of input values 2. Compute the map output value |
| * object 3. Compute the map output key object |
| * |
| * The source tag will be used by the reducer to determine from which source |
| * (which table in SQL terminology) a value comes. Computing the map output |
| * value object amounts to performing projecting/filtering work in a SQL |
| * statement (through the select/where clauses). Computing the map output key |
| * amounts to choosing the join key. This class provides the appropriate plugin |
| * points for the user defined subclasses to implement the appropriate logic. |
| * |
| */ |
| public abstract class DataJoinMapperBase extends JobBase { |
| |
| protected String inputFile = null; |
| |
| protected JobConf job = null; |
| |
| protected Text inputTag = null; |
| |
| protected Reporter reporter = null; |
| |
| public void configure(JobConf job) { |
| super.configure(job); |
| this.job = job; |
| this.inputFile = job.get(MRJobConfig.MAP_INPUT_FILE); |
| this.inputTag = generateInputTag(this.inputFile); |
| } |
| |
| /** |
| * Determine the source tag based on the input file name. |
| * |
| * @param inputFile |
| * @return the source tag computed from the given file name. |
| */ |
| protected abstract Text generateInputTag(String inputFile); |
| |
| /** |
| * Generate a tagged map output value. The user code can also perform |
| * projection/filtering. If it decides to discard the input record when |
| * certain conditions are met,it can simply return a null. |
| * |
| * @param value |
| * @return an object of TaggedMapOutput computed from the given value. |
| */ |
| protected abstract TaggedMapOutput generateTaggedMapOutput(Object value); |
| |
| /** |
| * Generate a map output key. The user code can compute the key |
| * programmatically, not just selecting the values of some fields. In this |
| * sense, it is more general than the joining capabilities of SQL. |
| * |
| * @param aRecord |
| * @return the group key for the given record |
| */ |
| protected abstract Text generateGroupKey(TaggedMapOutput aRecord); |
| |
| public void map(Object key, Object value, |
| OutputCollector output, Reporter reporter) throws IOException { |
| if (this.reporter == null) { |
| this.reporter = reporter; |
| } |
| addLongValue("totalCount", 1); |
| TaggedMapOutput aRecord = generateTaggedMapOutput(value); |
| if (aRecord == null) { |
| addLongValue("discardedCount", 1); |
| return; |
| } |
| Text groupKey = generateGroupKey(aRecord); |
| if (groupKey == null) { |
| addLongValue("nullGroupKeyCount", 1); |
| return; |
| } |
| output.collect(groupKey, aRecord); |
| addLongValue("collectedCount", 1); |
| } |
| |
| public void close() throws IOException { |
| if (this.reporter != null) { |
| this.reporter.setStatus(super.getReport()); |
| } |
| } |
| |
| public void reduce(Object arg0, Iterator arg1, |
| OutputCollector arg2, Reporter arg3) throws IOException { |
| // TODO Auto-generated method stub |
| |
| } |
| } |