1 /**
2 *
3 * Licensed to the Apache Software Foundation (ASF) under one
4 * or more contributor license agreements. See the NOTICE file
5 * distributed with this work for additional information
6 * regarding copyright ownership. The ASF licenses this file
7 * to you under the Apache License, Version 2.0 (the
8 * "License"); you may not use this file except in compliance
9 * with the License. You may obtain a copy of the License at
10 *
11 * http://www.apache.org/licenses/LICENSE-2.0
12 *
13 * Unless required by applicable law or agreed to in writing, software
14 * distributed under the License is distributed on an "AS IS" BASIS,
15 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
16 * See the License for the specific language governing permissions and
17 * limitations under the License.
18 */
19 package org.apache.hadoop.hbase.regionserver;
20
21 import java.io.IOException;
22 import java.util.List;
23
24 import org.apache.hadoop.classification.InterfaceAudience;
25 import org.apache.hadoop.hbase.HRegionInfo;
26 import org.apache.hadoop.hbase.KeyValue;
27 import org.apache.hadoop.hbase.client.Scan;
28
29 /**
30 * RegionScanner describes iterators over rows in an HRegion.
31 */
32 @InterfaceAudience.Private
33 public interface RegionScanner extends InternalScanner {
34 /**
35 * @return The RegionInfo for this scanner.
36 */
37 HRegionInfo getRegionInfo();
38
39 /**
40 * @return True if a filter indicates that this scanner will return no further rows.
41 * @throws IOException in case of I/O failure on a filter.
42 */
43 boolean isFilterDone() throws IOException;
44
45 /**
46 * Do a reseek to the required row. Should not be used to seek to a key which
47 * may come before the current position. Always seeks to the beginning of a
48 * row boundary.
49 *
50 * @throws IOException
51 * @throws IllegalArgumentException
52 * if row is null
53 *
54 */
55 boolean reseek(byte[] row) throws IOException;
56
57 /**
58 * @return The preferred max buffersize. See {@link Scan#setMaxResultSize(long)}
59 */
60 long getMaxResultSize();
61
62 /**
63 * @return The Scanner's MVCC readPt see {@link MultiVersionConsistencyControl}
64 */
65 long getMvccReadPoint();
66
67 /**
68 * Grab the next row's worth of values with the default limit on the number of values
69 * to return.
70 * This is a special internal method to be called from coprocessor hooks to avoid expensive setup.
71 * Caller must set the thread's readpoint, start and close a region operation, an synchronize on the scanner object.
72 * See {@link #nextRaw(List, int)}
73 * @param result return output array
74 * @return true if more rows exist after this one, false if scanner is done
75 * @throws IOException e
76 */
77 boolean nextRaw(List<KeyValue> result) throws IOException;
78
79 /**
80 * Grab the next row's worth of values with a limit on the number of values
81 * to return.
82 * This is a special internal method to be called from coprocessor hooks to avoid expensive setup.
83 * Caller must set the thread's readpoint, start and close a region operation, an synchronize on the scanner object.
84 * Example:
85 * <code><pre>
86 * HRegion region = ...;
87 * RegionScanner scanner = ...
88 * MultiVersionConsistencyControl.setThreadReadPoint(scanner.getMvccReadPoint());
89 * region.startRegionOperation();
90 * try {
91 * synchronized(scanner) {
92 * ...
93 * boolean moreRows = scanner.nextRaw(values);
94 * ...
95 * }
96 * } finally {
97 * region.closeRegionOperation();
98 * }
99 * </pre></code>
100 * @param result return output array
101 * @param limit limit on row count to get
102 * @return true if more rows exist after this one, false if scanner is done
103 * @throws IOException e
104 */
105 boolean nextRaw(List<KeyValue> result, int limit) throws IOException;
106 }