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1   /**
2    * Copyright 2010 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  
24  import org.apache.hadoop.hbase.client.HTable;
25  import org.apache.hadoop.hbase.client.Result;
26  import org.apache.hadoop.hbase.client.Scan;
27  import org.apache.hadoop.hbase.io.ImmutableBytesWritable;
28  import org.apache.hadoop.mapreduce.InputSplit;
29  import org.apache.hadoop.mapreduce.RecordReader;
30  import org.apache.hadoop.mapreduce.TaskAttemptContext;
31  
32  /**
33   * Iterate over an HBase table data, return (ImmutableBytesWritable, Result)
34   * pairs.
35   */
36  public class TableRecordReader
37  extends RecordReader<ImmutableBytesWritable, Result> {
38  
39    private TableRecordReaderImpl recordReaderImpl = new TableRecordReaderImpl();
40  
41    /**
42     * Restart from survivable exceptions by creating a new scanner.
43     *
44     * @param firstRow  The first row to start at.
45     * @throws IOException When restarting fails.
46     */
47    public void restart(byte[] firstRow) throws IOException {
48      this.recordReaderImpl.restart(firstRow);
49    }
50  
51    /**
52     * Build the scanner. Not done in constructor to allow for extension.
53     *
54     * @throws IOException When restarting the scan fails.
55     */
56    public void init() throws IOException {
57      this.recordReaderImpl.init();
58    }
59  
60    /**
61     * Sets the HBase table.
62     *
63     * @param htable  The {@link HTable} to scan.
64     */
65    public void setHTable(HTable htable) {
66      this.recordReaderImpl.setHTable(htable);
67    }
68  
69    /**
70     * Sets the scan defining the actual details like columns etc.
71     *
72     * @param scan  The scan to set.
73     */
74    public void setScan(Scan scan) {
75      this.recordReaderImpl.setScan(scan);
76    }
77  
78    /**
79     * Closes the split.
80     *
81     * @see org.apache.hadoop.mapreduce.RecordReader#close()
82     */
83    @Override
84    public void close() {
85      this.recordReaderImpl.close();
86    }
87  
88    /**
89     * Returns the current key.
90     *
91     * @return The current key.
92     * @throws IOException
93     * @throws InterruptedException When the job is aborted.
94     * @see org.apache.hadoop.mapreduce.RecordReader#getCurrentKey()
95     */
96    @Override
97    public ImmutableBytesWritable getCurrentKey() throws IOException,
98        InterruptedException {
99      return this.recordReaderImpl.getCurrentKey();
100   }
101 
102   /**
103    * Returns the current value.
104    *
105    * @return The current value.
106    * @throws IOException When the value is faulty.
107    * @throws InterruptedException When the job is aborted.
108    * @see org.apache.hadoop.mapreduce.RecordReader#getCurrentValue()
109    */
110   @Override
111   public Result getCurrentValue() throws IOException, InterruptedException {
112     return this.recordReaderImpl.getCurrentValue();
113   }
114 
115   /**
116    * Initializes the reader.
117    *
118    * @param inputsplit  The split to work with.
119    * @param context  The current task context.
120    * @throws IOException When setting up the reader fails.
121    * @throws InterruptedException When the job is aborted.
122    * @see org.apache.hadoop.mapreduce.RecordReader#initialize(
123    *   org.apache.hadoop.mapreduce.InputSplit,
124    *   org.apache.hadoop.mapreduce.TaskAttemptContext)
125    */
126   @Override
127   public void initialize(InputSplit inputsplit,
128       TaskAttemptContext context) throws IOException,
129       InterruptedException {
130   }
131 
132   /**
133    * Positions the record reader to the next record.
134    *
135    * @return <code>true</code> if there was another record.
136    * @throws IOException When reading the record failed.
137    * @throws InterruptedException When the job was aborted.
138    * @see org.apache.hadoop.mapreduce.RecordReader#nextKeyValue()
139    */
140   @Override
141   public boolean nextKeyValue() throws IOException, InterruptedException {
142     return this.recordReaderImpl.nextKeyValue();
143   }
144 
145   /**
146    * The current progress of the record reader through its data.
147    *
148    * @return A number between 0.0 and 1.0, the fraction of the data read.
149    * @see org.apache.hadoop.mapreduce.RecordReader#getProgress()
150    */
151   @Override
152   public float getProgress() {
153     return this.recordReaderImpl.getProgress();
154   }
155 }