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1   /**
2    * Copyright 2007 The Apache Software Foundation
3    *
4    * Licensed to the Apache Software Foundation (ASF) under one
5    * or more contributor license agreements.  See the NOTICE file
6    * distributed with this work for additional information
7    * regarding copyright ownership.  The ASF licenses this file
8    * to you under the Apache License, Version 2.0 (the
9    * "License"); you may not use this file except in compliance
10   * with the License.  You may obtain a copy of the License at
11   *
12   *     http://www.apache.org/licenses/LICENSE-2.0
13   *
14   * Unless required by applicable law or agreed to in writing, software
15   * distributed under the License is distributed on an "AS IS" BASIS,
16   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
17   * See the License for the specific language governing permissions and
18   * limitations under the License.
19   */
20  package org.apache.hadoop.hbase.mapreduce;
21  
22  import java.io.IOException;
23  import java.io.UnsupportedEncodingException;
24  import java.util.ArrayList;
25  
26  import org.apache.hadoop.conf.Configurable;
27  import org.apache.hadoop.conf.Configuration;
28  import org.apache.hadoop.hbase.KeyValue;
29  import org.apache.hadoop.hbase.HConstants;
30  import org.apache.hadoop.hbase.client.Result;
31  import org.apache.hadoop.hbase.client.Scan;
32  import org.apache.hadoop.hbase.io.ImmutableBytesWritable;
33  import org.apache.hadoop.hbase.util.Bytes;
34  import org.apache.hadoop.mapreduce.Job;
35  
36  /**
37   * Extract grouping columns from input record.
38   */
39  public class GroupingTableMapper
40  extends TableMapper<ImmutableBytesWritable,Result> implements Configurable {
41  
42    /**
43     * JobConf parameter to specify the columns used to produce the key passed to
44     * collect from the map phase.
45     */
46    public static final String GROUP_COLUMNS =
47      "hbase.mapred.groupingtablemap.columns";
48  
49    /** The grouping columns. */
50    protected byte [][] columns;
51    /** The current configuration. */
52    private Configuration conf = null;
53  
54    /**
55     * Use this before submitting a TableMap job. It will appropriately set up
56     * the job.
57     *
58     * @param table The table to be processed.
59     * @param scan  The scan with the columns etc.
60     * @param groupColumns  A space separated list of columns used to form the
61     * key used in collect.
62     * @param mapper  The mapper class.
63     * @param job  The current job.
64     * @throws IOException When setting up the job fails.
65     */
66    @SuppressWarnings("unchecked")
67    public static void initJob(String table, Scan scan, String groupColumns,
68      Class<? extends TableMapper> mapper, Job job) throws IOException {
69      TableMapReduceUtil.initTableMapperJob(table, scan, mapper,
70          ImmutableBytesWritable.class, Result.class, job);
71      job.getConfiguration().set(GROUP_COLUMNS, groupColumns);
72    }
73  
74    /**
75     * Extract the grouping columns from value to construct a new key. Pass the
76     * new key and value to reduce. If any of the grouping columns are not found
77     * in the value, the record is skipped.
78     *
79     * @param key  The current key.
80     * @param value  The current value.
81     * @param context  The current context.
82     * @throws IOException When writing the record fails.
83     * @throws InterruptedException When the job is aborted.
84     */
85    @Override
86    public void map(ImmutableBytesWritable key, Result value, Context context)
87    throws IOException, InterruptedException {
88      byte[][] keyVals = extractKeyValues(value);
89      if(keyVals != null) {
90        ImmutableBytesWritable tKey = createGroupKey(keyVals);
91        context.write(tKey, value);
92      }
93    }
94  
95    /**
96     * Extract columns values from the current record. This method returns
97     * null if any of the columns are not found.
98     * <p>
99     * Override this method if you want to deal with nulls differently.
100    *
101    * @param r  The current values.
102    * @return Array of byte values.
103    */
104   protected byte[][] extractKeyValues(Result r) {
105     byte[][] keyVals = null;
106     ArrayList<byte[]> foundList = new ArrayList<byte[]>();
107     int numCols = columns.length;
108     if (numCols > 0) {
109       for (KeyValue value: r.list()) {
110         byte [] column = KeyValue.makeColumn(value.getFamily(),
111             value.getQualifier());
112         for (int i = 0; i < numCols; i++) {
113           if (Bytes.equals(column, columns[i])) {
114             foundList.add(value.getValue());
115             break;
116           }
117         }
118       }
119       if(foundList.size() == numCols) {
120         keyVals = foundList.toArray(new byte[numCols][]);
121       }
122     }
123     return keyVals;
124   }
125 
126   /**
127    * Create a key by concatenating multiple column values.
128    * <p>
129    * Override this function in order to produce different types of keys.
130    *
131    * @param vals  The current key/values.
132    * @return A key generated by concatenating multiple column values.
133    */
134   protected ImmutableBytesWritable createGroupKey(byte[][] vals) {
135     if(vals == null) {
136       return null;
137     }
138     StringBuilder sb =  new StringBuilder();
139     for(int i = 0; i < vals.length; i++) {
140       if(i > 0) {
141         sb.append(" ");
142       }
143       try {
144         sb.append(new String(vals[i], HConstants.UTF8_ENCODING));
145       } catch (UnsupportedEncodingException e) {
146         throw new RuntimeException(e);
147       }
148     }
149     return new ImmutableBytesWritable(Bytes.toBytes(sb.toString()));
150   }
151 
152   /**
153    * Returns the current configuration.
154    *
155    * @return The current configuration.
156    * @see org.apache.hadoop.conf.Configurable#getConf()
157    */
158   @Override
159   public Configuration getConf() {
160     return conf;
161   }
162 
163   /**
164    * Sets the configuration. This is used to set up the grouping details.
165    *
166    * @param configuration  The configuration to set.
167    * @see org.apache.hadoop.conf.Configurable#setConf(
168    *   org.apache.hadoop.conf.Configuration)
169    */
170   @Override
171   public void setConf(Configuration configuration) {
172     this.conf = configuration;
173     String[] cols = conf.get(GROUP_COLUMNS, "").split(" ");
174     columns = new byte[cols.length][];
175     for(int i = 0; i < cols.length; i++) {
176       columns[i] = Bytes.toBytes(cols[i]);
177     }
178   }
179 
180 }