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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  import java.util.ArrayList;
29  
30  import com.google.common.base.Preconditions;
31  
32  /**
33   * A filter that will only return the key component of each KV (the value will
34   * be rewritten as empty).
35   * <p>
36   * This filter can be used to grab all of the keys without having to also grab
37   * the values.
38   */
39  public class KeyOnlyFilter extends FilterBase {
40  
41    boolean lenAsVal;
42    public KeyOnlyFilter() { this(false); }
43    public KeyOnlyFilter(boolean lenAsVal) { this.lenAsVal = lenAsVal; }
44  
45    @Override
46    public KeyValue transform(KeyValue kv) {
47      return kv.createKeyOnly(this.lenAsVal);
48    }
49  
50    public static Filter createFilterFromArguments(ArrayList<byte []> filterArguments) {
51      Preconditions.checkArgument((filterArguments.size() == 0 || filterArguments.size() == 1),
52                                  "Expected: 0 or 1 but got: %s", filterArguments.size());
53      KeyOnlyFilter filter = new KeyOnlyFilter();
54      if (filterArguments.size() == 1) {
55        filter.lenAsVal = ParseFilter.convertByteArrayToBoolean(filterArguments.get(0));
56      }
57      return filter;
58    }
59  
60    public void write(DataOutput out) throws IOException {
61      out.writeBoolean(this.lenAsVal);
62    }
63  
64    public void readFields(DataInput in) throws IOException {
65      this.lenAsVal = in.readBoolean();
66    }
67  }