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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.filter;
21  
22  import java.io.DataInput;
23  import java.io.DataOutput;
24  import java.io.IOException;
25  import org.apache.hadoop.hbase.KeyValue;
26  import org.apache.hadoop.hbase.util.Bytes;
27  
28  /**
29   * A filter that will only return the key component of each KV (the value will
30   * be rewritten as empty).
31   * <p>
32   * This filter can be used to grab all of the keys without having to also grab
33   * the values.
34   */
35  public class KeyOnlyFilter extends FilterBase {
36  
37    boolean lenAsVal;
38    public KeyOnlyFilter() { this(false); }
39    public KeyOnlyFilter(boolean lenAsVal) { this.lenAsVal = lenAsVal; }
40  
41    @Override
42    public ReturnCode filterKeyValue(KeyValue kv) {
43      kv.convertToKeyOnly(this.lenAsVal);
44      return ReturnCode.INCLUDE;
45    }
46  
47    public void write(DataOutput out) throws IOException {
48      out.writeBoolean(this.lenAsVal);
49    }
50  
51    public void readFields(DataInput in) throws IOException {
52      this.lenAsVal = in.readBoolean();
53    }
54  }