View Javadoc

1   /*
2    * Licensed to the Apache Software Foundation (ASF) under one
3    * or more contributor license agreements.  See the NOTICE file
4    * distributed with this work for additional information
5    * regarding copyright ownership.  The ASF licenses this file
6    * to you under the Apache License, Version 2.0 (the
7    * "License"); you may not use this file except in compliance
8    * with the License.  You may obtain a copy of the License at
9    *
10   *     http://www.apache.org/licenses/LICENSE-2.0
11   *
12   * Unless required by applicable law or agreed to in writing, software
13   * distributed under the License is distributed on an "AS IS" BASIS,
14   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
15   * See the License for the specific language governing permissions and
16   * limitations under the License.
17   */
18  package org.apache.hadoop.hbase.filter;
19  
20  import org.apache.hadoop.hbase.KeyValue;
21  import org.apache.hadoop.hbase.util.Bytes;
22  
23  import java.io.DataOutput;
24  import java.io.IOException;
25  import java.io.DataInput;
26  import java.util.Arrays;
27  import java.util.Comparator;
28  import java.util.TreeSet;
29  import java.util.ArrayList;
30  
31  /**
32   * This filter is used for selecting only those keys with columns that matches
33   * a particular prefix. For example, if prefix is 'an', it will pass keys will
34   * columns like 'and', 'anti' but not keys with columns like 'ball', 'act'.
35   */
36  public class MultipleColumnPrefixFilter extends FilterBase {
37    protected byte [] hint = null;
38    protected TreeSet<byte []> sortedPrefixes = createTreeSet();
39  
40    public MultipleColumnPrefixFilter() {
41      super();
42    }
43  
44    public MultipleColumnPrefixFilter(final byte [][] prefixes) {
45      if (prefixes != null) {
46        for (int i = 0; i < prefixes.length; i++) {
47          if (!sortedPrefixes.add(prefixes[i]))
48            throw new IllegalArgumentException ("prefixes must be distinct");
49        }
50      }
51    }
52  
53    public byte [][] getPrefix() {
54      int count = 0;
55      byte [][] temp = new byte [sortedPrefixes.size()][];
56      for (byte [] prefixes : sortedPrefixes) {
57        temp [count++] = prefixes;
58      }
59      return temp;
60    }
61  
62    @Override
63    public ReturnCode filterKeyValue(KeyValue kv) {
64      if (sortedPrefixes.size() == 0 || kv.getBuffer() == null) {
65        return ReturnCode.INCLUDE;
66      } else {
67        return filterColumn(kv.getBuffer(), kv.getQualifierOffset(), kv.getQualifierLength());
68      }
69    }
70  
71    public ReturnCode filterColumn(byte[] buffer, int qualifierOffset, int qualifierLength) {
72      byte [] qualifier = Arrays.copyOfRange(buffer, qualifierOffset,
73                                             qualifierLength + qualifierOffset);
74      TreeSet<byte []> lesserOrEqualPrefixes =
75        (TreeSet<byte []>) sortedPrefixes.headSet(qualifier, true);
76  
77      if (lesserOrEqualPrefixes.size() != 0) {
78        byte [] largestPrefixSmallerThanQualifier = lesserOrEqualPrefixes.last();
79        
80        if (Bytes.startsWith(qualifier, largestPrefixSmallerThanQualifier)) {
81          return ReturnCode.INCLUDE;
82        }
83        
84        if (lesserOrEqualPrefixes.size() == sortedPrefixes.size()) {
85          return ReturnCode.NEXT_ROW;
86        } else {
87          hint = sortedPrefixes.higher(largestPrefixSmallerThanQualifier);
88          return ReturnCode.SEEK_NEXT_USING_HINT;
89        }
90      } else {
91        hint = sortedPrefixes.first();
92        return ReturnCode.SEEK_NEXT_USING_HINT;
93      }
94    }
95  
96    public static Filter createFilterFromArguments(ArrayList<byte []> filterArguments) {
97      byte [][] prefixes = new byte [filterArguments.size()][];
98      for (int i = 0 ; i < filterArguments.size(); i++) {
99        byte [] columnPrefix = ParseFilter.removeQuotesFromByteArray(filterArguments.get(i));
100       prefixes[i] = columnPrefix;
101     }
102     return new MultipleColumnPrefixFilter(prefixes);
103   }
104 
105   public void write(DataOutput out) throws IOException {
106     out.writeInt(sortedPrefixes.size());
107     for (byte [] element : sortedPrefixes) {
108       Bytes.writeByteArray(out, element);
109     }
110   }
111 
112   public void readFields(DataInput in) throws IOException {
113     int x = in.readInt();
114     this.sortedPrefixes = createTreeSet();
115     for (int j = 0; j < x; j++) {
116       sortedPrefixes.add(Bytes.readByteArray(in));
117     }
118   }
119 
120   public KeyValue getNextKeyHint(KeyValue kv) {
121     return KeyValue.createFirstOnRow(
122       kv.getBuffer(), kv.getRowOffset(), kv.getRowLength(), kv.getBuffer(),
123       kv.getFamilyOffset(), kv.getFamilyLength(), hint, 0, hint.length);
124   }
125 
126   public TreeSet<byte []> createTreeSet() {
127     return new TreeSet<byte []>(new Comparator<Object>() {
128         @Override
129           public int compare (Object o1, Object o2) {
130           if (o1 == null || o2 == null)
131             throw new IllegalArgumentException ("prefixes can't be null");
132 
133           byte [] b1 = (byte []) o1;
134           byte [] b2 = (byte []) o2;
135           return Bytes.compareTo (b1, 0, b1.length, b2, 0, b2.length);
136         }
137       });
138   }
139 }