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.codec.prefixtree.scanner;
20
21 import org.apache.hadoop.classification.InterfaceAudience;
22 import org.apache.hadoop.classification.InterfaceStability;
23
24 /**
25 * An indicator of the state of the scanner after an operation such as nextCell() or
26 * positionAt(..). For example:
27 * <ul>
28 * <li>In a DataBlockScanner, the AFTER_LAST position indicates to the parent StoreFileScanner that
29 * it should load the next block.</li>
30 * <li>In a StoreFileScanner, the AFTER_LAST position indicates that the file has been exhausted.
31 * </li>
32 * <li>In a RegionScanner, the AFTER_LAST position indicates that the scanner should move to the
33 * next region.</li>
34 * </ul>
35 */
36 @InterfaceAudience.Public
37 @InterfaceStability.Evolving
38 public enum CellScannerPosition {
39
40 /**
41 * getCurrentCell() will NOT return a valid cell. Calling nextCell() will advance to the first
42 * cell.
43 */
44 BEFORE_FIRST,
45
46 /**
47 * getCurrentCell() will return a valid cell, but it is not the cell requested by positionAt(..),
48 * rather it is the nearest cell before the requested cell.
49 */
50 BEFORE,
51
52 /**
53 * getCurrentCell() will return a valid cell, and it is exactly the cell that was requested by
54 * positionAt(..).
55 */
56 AT,
57
58 /**
59 * getCurrentCell() will return a valid cell, but it is not the cell requested by positionAt(..),
60 * rather it is the nearest cell after the requested cell.
61 */
62 AFTER,
63
64 /**
65 * getCurrentCell() will NOT return a valid cell. Calling nextCell() will have no effect.
66 */
67 AFTER_LAST
68
69 }