| /** |
| * 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 org.apache.hadoop.io.Text; |
| |
| import org.apache.hadoop.contrib.utils.join.DataJoinReducerBase; |
| import org.apache.hadoop.contrib.utils.join.TaggedMapOutput; |
| |
| /** |
| * This is a subclass of DataJoinReducerBase that is used to |
| * demonstrate the functionality of INNER JOIN between 2 data |
| * sources (TAB separated text files) based on the first column. |
| */ |
| public class SampleDataJoinReducer extends DataJoinReducerBase { |
| |
| /** |
| * |
| * @param tags |
| * a list of source tags |
| * @param values |
| * a value per source |
| * @return combined value derived from values of the sources |
| */ |
| protected TaggedMapOutput combine(Object[] tags, Object[] values) { |
| // eliminate rows which didnot match in one of the two tables (for INNER JOIN) |
| if (tags.length < 2) |
| return null; |
| String joinedStr = ""; |
| for (int i=0; i<tags.length; i++) { |
| if (i > 0) |
| joinedStr += "\t"; |
| // strip first column as it is the key on which we joined |
| String line = ((Text) (((TaggedMapOutput) values[i]).getData())).toString(); |
| String[] tokens = line.split("\\t", 2); |
| joinedStr += tokens[1]; |
| } |
| TaggedMapOutput retv = new SampleTaggedMapOutput(new Text(joinedStr)); |
| retv.setTag((Text) tags[0]); |
| return retv; |
| } |
| } |