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1   /*
2    *
3    * Licensed to the Apache Software Foundation (ASF) under one
4    * or more contributor license agreements.  See the NOTICE file
5    * distributed with this work for additional information
6    * regarding copyright ownership.  The ASF licenses this file
7    * to you under the Apache License, Version 2.0 (the
8    * "License"); you may not use this file except in compliance
9    * with the License.  You may obtain a copy of the License at
10   *
11   *     http://www.apache.org/licenses/LICENSE-2.0
12   *
13   * Unless required by applicable law or agreed to in writing, software
14   * distributed under the License is distributed on an "AS IS" BASIS,
15   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
16   * See the License for the specific language governing permissions and
17   * limitations under the License.
18   */
19  package org.apache.hadoop.hbase.regionserver;
20  
21  import java.io.IOException;
22  
23  import org.apache.commons.lang.NotImplementedException;
24  import org.apache.hadoop.hbase.classification.InterfaceAudience;
25  import org.apache.hadoop.hbase.Cell;
26  import org.apache.hadoop.hbase.client.Scan;
27  
28  /**
29   * A "non-lazy" scanner which always does a real seek operation. Most scanners
30   * are inherited from this class.
31   */
32  @InterfaceAudience.Private
33  public abstract class NonLazyKeyValueScanner implements KeyValueScanner {
34  
35    @Override
36    public boolean requestSeek(Cell kv, boolean forward, boolean useBloom)
37        throws IOException {
38      return doRealSeek(this, kv, forward);
39    }
40  
41    @Override
42    public boolean realSeekDone() {
43      return true;
44    }
45  
46    @Override
47    public void enforceSeek() throws IOException {
48      throw new NotImplementedException("enforceSeek must not be called on a " +
49          "non-lazy scanner");
50    }
51  
52    public static boolean doRealSeek(KeyValueScanner scanner,
53        Cell kv, boolean forward) throws IOException {
54      return forward ? scanner.reseek(kv) : scanner.seek(kv);
55    }
56  
57    @Override
58    public boolean shouldUseScanner(Scan scan, Store store, long oldestUnexpiredTS) {
59      // No optimizations implemented by default.
60      return true;
61    }
62  
63    @Override
64    public boolean isFileScanner() {
65      // Not a file by default.
66      return false;
67    }
68    @Override
69    public Cell getNextIndexedKey() {
70      return null;
71    }
72  
73    @Override
74    public void shipped() throws IOException {
75      // do nothing
76    }
77  }