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
19 package org.apache.hadoop.hbase.regionserver;
20
21 import java.util.Arrays;
22
23 import org.apache.commons.logging.Log;
24 import org.apache.commons.logging.LogFactory;
25 import org.apache.hadoop.hbase.classification.InterfaceAudience;
26 import org.apache.hadoop.hbase.util.Bytes;
27
28 /**
29 * A custom RegionSplitPolicy implementing a SplitPolicy that groups
30 * rows by a prefix of the row-key with a delimiter. Only the first delimiter
31 * for the row key will define the prefix of the row key that is used for grouping.
32 *
33 * This ensures that a region is not split "inside" a prefix of a row key.
34 * I.e. rows can be co-located in a region by their prefix.
35 *
36 * As an example, if you have row keys delimited with <code>_</code>, like
37 * <code>userid_eventtype_eventid</code>, and use prefix delimiter _, this split policy
38 * ensures that all rows starting with the same userid, belongs to the same region.
39 * @see KeyPrefixRegionSplitPolicy
40 */
41 @InterfaceAudience.Private
42 public class DelimitedKeyPrefixRegionSplitPolicy extends IncreasingToUpperBoundRegionSplitPolicy {
43
44 private static final Log LOG = LogFactory
45 .getLog(DelimitedKeyPrefixRegionSplitPolicy.class);
46 public static final String DELIMITER_KEY = "DelimitedKeyPrefixRegionSplitPolicy.delimiter";
47
48 private byte[] delimiter = null;
49
50 @Override
51 protected void configureForRegion(HRegion region) {
52 super.configureForRegion(region);
53 // read the prefix length from the table descriptor
54 String delimiterString = region.getTableDesc().getValue(DELIMITER_KEY);
55 if (delimiterString == null || delimiterString.length() == 0) {
56 LOG.error(DELIMITER_KEY + " not specified for table " + region.getTableDesc().getTableName() +
57 ". Using default RegionSplitPolicy");
58 return;
59 }
60 delimiter = Bytes.toBytes(delimiterString);
61 }
62
63 @Override
64 protected byte[] getSplitPoint() {
65 byte[] splitPoint = super.getSplitPoint();
66 if (splitPoint != null && delimiter != null) {
67
68 //find the first occurrence of delimiter in split point
69 int index = com.google.common.primitives.Bytes.indexOf(splitPoint, delimiter);
70 if (index < 0) {
71 LOG.warn("Delimiter " + Bytes.toString(delimiter) + " not found for split key "
72 + Bytes.toString(splitPoint));
73 return splitPoint;
74 }
75
76 // group split keys by a prefix
77 return Arrays.copyOf(splitPoint, Math.min(index, splitPoint.length));
78 } else {
79 return splitPoint;
80 }
81 }
82 }