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,
52 "Expected: 0 but got: %s", filterArguments.size());
53 return new KeyOnlyFilter();
54 }
55
56 public void write(DataOutput out) throws IOException {
57 out.writeBoolean(this.lenAsVal);
58 }
59
60 public void readFields(DataInput in) throws IOException {
61 this.lenAsVal = in.readBoolean();
62 }
63 }