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
23 import org.apache.hadoop.classification.InterfaceAudience;
24 import org.apache.hadoop.hbase.regionserver.ScanQueryMatcher.MatchCode;
25
26 /**
27 * Implementing classes of this interface will be used for the tracking
28 * and enforcement of columns and numbers of versions and timeToLive during
29 * the course of a Get or Scan operation.
30 * <p>
31 * Currently there are two different types of Store/Family-level queries.
32 * <ul><li>{@link ExplicitColumnTracker} is used when the query specifies
33 * one or more column qualifiers to return in the family.
34 * <p>
35 * This class is utilized by {@link ScanQueryMatcher} through two methods:
36 * <ul><li>{@link #checkColumn} is called when a Put satisfies all other
37 * conditions of the query. This method returns a {@link org.apache.hadoop.hbase.regionserver.ScanQueryMatcher.MatchCode} to define
38 * what action should be taken.
39 * <li>{@link #update} is called at the end of every StoreFile or memstore.
40 * <p>
41 * This class is NOT thread-safe as queries are never multi-threaded
42 */
43 @InterfaceAudience.Private
44 public interface ColumnTracker {
45 /**
46 * Keeps track of the number of versions for the columns asked for
47 * @param bytes
48 * @param offset
49 * @param length
50 * @param ttl The timeToLive to enforce.
51 * @param type The type of the KeyValue
52 * @param ignoreCount indicates if the KV needs to be excluded while counting
53 * (used during compactions. We only count KV's that are older than all the
54 * scanners' read points.)
55 * @return The match code instance.
56 * @throws IOException in case there is an internal consistency problem
57 * caused by a data corruption.
58 */
59 public ScanQueryMatcher.MatchCode checkColumn(byte[] bytes, int offset,
60 int length, long ttl, byte type, boolean ignoreCount)
61 throws IOException;
62
63 /**
64 * Updates internal variables in between files
65 */
66 public void update();
67
68 /**
69 * Resets the Matcher
70 */
71 public void reset();
72
73 /**
74 *
75 * @return <code>true</code> when done.
76 */
77 public boolean done();
78
79 /**
80 * Used by matcher and scan/get to get a hint of the next column
81 * to seek to after checkColumn() returns SKIP. Returns the next interesting
82 * column we want, or NULL there is none (wildcard scanner).
83 *
84 * Implementations aren't required to return anything useful unless the most recent
85 * call was to checkColumn() and the return code was SKIP. This is pretty implementation
86 * detail-y, but optimizations are like that.
87 *
88 * @return null, or a ColumnCount that we should seek to
89 */
90 public ColumnCount getColumnHint();
91
92 /**
93 * Retrieve the MatchCode for the next row or column
94 */
95 public MatchCode getNextRowOrNextColumn(byte[] bytes, int offset,
96 int qualLength);
97
98 /**
99 * Give the tracker a chance to declare it's done based on only the timestamp
100 * to allow an early out.
101 *
102 * @param timestamp
103 * @return <code>true</code> to early out based on timestamp.
104 */
105 public boolean isDone(long timestamp);
106 }