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1   /**
2    * Licensed to the Apache Software Foundation (ASF) under one
3    * or more contributor license agreements.  See the NOTICE file
4    * distributed with this work for additional information
5    * regarding copyright ownership.  The ASF licenses this file
6    * to you under the Apache License, Version 2.0 (the
7    * "License"); you may not use this file except in compliance
8    * with the License.  You may obtain a copy of the License at
9    *
10   *     http://www.apache.org/licenses/LICENSE-2.0
11   *
12   * Unless required by applicable law or agreed to in writing, software
13   * distributed under the License is distributed on an "AS IS" BASIS,
14   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
15   * See the License for the specific language governing permissions and
16   * limitations under the License.
17   */
18  
19  package org.apache.hadoop.hbase.client;
20  
21  import java.io.IOException;
22  import java.util.ArrayList;
23  import java.util.List;
24  
25  import org.apache.hadoop.hbase.classification.InterfaceAudience;
26  import org.apache.hadoop.conf.Configuration;
27  import org.apache.hadoop.fs.FileSystem;
28  import org.apache.hadoop.fs.Path;
29  import org.apache.hadoop.hbase.Cell;
30  import org.apache.hadoop.hbase.CellUtil;
31  import org.apache.hadoop.hbase.HRegionInfo;
32  import org.apache.hadoop.hbase.HTableDescriptor;
33  import org.apache.hadoop.hbase.client.metrics.ScanMetrics;
34  import org.apache.hadoop.hbase.regionserver.HRegion;
35  import org.apache.hadoop.hbase.regionserver.RegionScanner;
36  import org.mortbay.log.Log;
37  
38  /**
39   * A client scanner for a region opened for read-only on the client side. Assumes region data
40   * is not changing.
41   */
42  @InterfaceAudience.Private
43  public class ClientSideRegionScanner extends AbstractClientScanner {
44  
45    private HRegion region;
46    RegionScanner scanner;
47    List<Cell> values;
48  
49    public ClientSideRegionScanner(Configuration conf, FileSystem fs,
50        Path rootDir, HTableDescriptor htd, HRegionInfo hri, Scan scan, ScanMetrics scanMetrics)
51            throws IOException {
52  
53      // region is immutable, set isolation level
54      scan.setIsolationLevel(IsolationLevel.READ_UNCOMMITTED);
55  
56      // open region from the snapshot directory
57      this.region = HRegion.openHRegion(conf, fs, rootDir, hri, htd, null, null, null);
58  
59      // create an internal region scanner
60      this.scanner = region.getScanner(scan);
61      values = new ArrayList<Cell>();
62  
63      if (scanMetrics == null) {
64        initScanMetrics(scan);
65      } else {
66        this.scanMetrics = scanMetrics;
67      }
68      region.startRegionOperation();
69    }
70  
71    @Override
72    public Result next() throws IOException {
73      values.clear();
74  
75      scanner.nextRaw(values, -1); // pass -1 as limit so that we see the whole row.
76      if (values.isEmpty()) {
77        //we are done
78        return null;
79      }
80  
81      Result result = Result.create(values);
82      if (this.scanMetrics != null) {
83        long resultSize = 0;
84        for (Cell cell : values) {
85          resultSize += CellUtil.estimatedSerializedSizeOf(cell);
86        }
87        this.scanMetrics.countOfBytesInResults.addAndGet(resultSize);
88      }
89  
90      return result;
91    }
92  
93    @Override
94    public void close() {
95      if (this.scanner != null) {
96        try {
97          this.scanner.close();
98          this.scanner = null;
99        } catch (IOException ex) {
100         Log.warn("Exception while closing scanner", ex);
101       }
102     }
103     if (this.region != null) {
104       try {
105         this.region.closeRegionOperation();
106         this.region.close(true);
107         this.region = null;
108       } catch (IOException ex) {
109         Log.warn("Exception while closing region", ex);
110       }
111     }
112   }
113 }