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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  import java.util.SortedSet;
23  
24  import org.apache.commons.lang.NotImplementedException;
25  import org.apache.hadoop.hbase.classification.InterfaceAudience;
26  import org.apache.hadoop.hbase.Cell;
27  import org.apache.hadoop.hbase.client.Scan;
28  
29  /**
30   * A "non-lazy" scanner which always does a real seek operation. Most scanners
31   * are inherited from this class.
32   */
33  @InterfaceAudience.Private
34  public abstract class NonLazyKeyValueScanner implements KeyValueScanner {
35  
36    @Override
37    public boolean requestSeek(Cell kv, boolean forward, boolean useBloom)
38        throws IOException {
39      return doRealSeek(this, kv, forward);
40    }
41  
42    @Override
43    public boolean realSeekDone() {
44      return true;
45    }
46  
47    @Override
48    public void enforceSeek() throws IOException {
49      throw new NotImplementedException("enforceSeek must not be called on a " +
50          "non-lazy scanner");
51    }
52  
53    public static boolean doRealSeek(KeyValueScanner scanner,
54        Cell kv, boolean forward) throws IOException {
55      return forward ? scanner.reseek(kv) : scanner.seek(kv);
56    }
57  
58    @Override
59    public boolean shouldUseScanner(Scan scan, SortedSet<byte[]> columns,
60        long oldestUnexpiredTS) {
61      // No optimizations implemented by default.
62      return true;
63    }
64  
65    @Override
66    public boolean isFileScanner() {
67      // Not a file by default.
68      return false;
69    }
70  }