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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 org.apache.hadoop.classification.InterfaceAudience;
22  import org.apache.hadoop.hbase.Cell;
23  
24  /**
25   * This interface is used for the tracking and enforcement of Deletes
26   * during the course of a Get or Scan operation.
27   * <p>
28   * This class is utilized through three methods:
29   * <ul><li>{@link #add} when encountering a Delete
30   * <li>{@link #isDeleted} when checking if a Put KeyValue has been deleted
31   * <li>{@link #update} when reaching the end of a StoreFile
32   */
33  @InterfaceAudience.Private
34  public interface DeleteTracker {
35  
36    /**
37     * Add the specified cell to the list of deletes to check against for
38     * this row operation.
39     * <p>
40     * This is called when a Delete is encountered in a StoreFile.
41     * @param cell - the delete cell
42     */
43    void add(Cell cell);
44  
45    /**
46     * Check if the specified cell buffer has been deleted by a previously
47     * seen delete.
48     * @param cell - current cell to check if deleted by a previously seen delete
49     * @return deleteResult The result tells whether the KeyValue is deleted and why
50     */
51    DeleteResult isDeleted(Cell cell);
52  
53    /**
54     * @return true if there are no current delete, false otherwise
55     */
56    boolean isEmpty();
57  
58    /**
59     * Called at the end of every StoreFile.
60     * <p>
61     * Many optimized implementations of Trackers will require an update at
62     * when the end of each StoreFile is reached.
63     */
64    void update();
65  
66    /**
67     * Called between rows.
68     * <p>
69     * This clears everything as if a new DeleteTracker was instantiated.
70     */
71    void reset();
72  
73  
74    /**
75     * Return codes for comparison of two Deletes.
76     * <p>
77     * The codes tell the merging function what to do.
78     * <p>
79     * INCLUDE means add the specified Delete to the merged list.
80     * NEXT means move to the next element in the specified list(s).
81     */
82    enum DeleteCompare {
83      INCLUDE_OLD_NEXT_OLD,
84      INCLUDE_OLD_NEXT_BOTH,
85      INCLUDE_NEW_NEXT_NEW,
86      INCLUDE_NEW_NEXT_BOTH,
87      NEXT_OLD,
88      NEXT_NEW
89    }
90  
91    /**
92     * Returns codes for delete result.
93     * The codes tell the ScanQueryMatcher whether the kv is deleted and why.
94     * Based on the delete result, the ScanQueryMatcher will decide the next
95     * operation
96     */
97    enum DeleteResult {
98      FAMILY_DELETED, // The KeyValue is deleted by a delete family.
99      FAMILY_VERSION_DELETED, // The KeyValue is deleted by a delete family version.
100     COLUMN_DELETED, // The KeyValue is deleted by a delete column.
101     VERSION_DELETED, // The KeyValue is deleted by a version delete.
102     NOT_DELETED
103   }
104 
105 }