/Users/deen/code/yugabyte-db/src/yb/rocksdb/slice_transform.h
Line | Count | Source (jump to first uncovered line) |
1 | | // Copyright (c) 2011-present, Facebook, Inc. All rights reserved. |
2 | | // This source code is licensed under the BSD-style license found in the |
3 | | // LICENSE file in the root directory of this source tree. An additional grant |
4 | | // of patent rights can be found in the PATENTS file in the same directory. |
5 | | // Copyright (c) 2012 The LevelDB Authors. All rights reserved. |
6 | | // Use of this source code is governed by a BSD-style license that can be |
7 | | // found in the LICENSE file. See the AUTHORS file for names of contributors. |
8 | | // |
9 | | // The following only applies to changes made to this file as part of YugaByte development. |
10 | | // |
11 | | // Portions Copyright (c) YugaByte, Inc. |
12 | | // |
13 | | // Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except |
14 | | // in compliance with the License. You may obtain a copy of the License at |
15 | | // |
16 | | // http://www.apache.org/licenses/LICENSE-2.0 |
17 | | // |
18 | | // Unless required by applicable law or agreed to in writing, software distributed under the License |
19 | | // is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express |
20 | | // or implied. See the License for the specific language governing permissions and limitations |
21 | | // under the License. |
22 | | // |
23 | | // Class for specifying user-defined functions which perform a |
24 | | // transformation on a slice. It is not required that every slice |
25 | | // belong to the domain and/or range of a function. Subclasses should |
26 | | // define InDomain and InRange to determine which slices are in either |
27 | | // of these sets respectively. |
28 | | |
29 | | #ifndef ROCKSDB_INCLUDE_ROCKSDB_SLICE_TRANSFORM_H |
30 | | #define ROCKSDB_INCLUDE_ROCKSDB_SLICE_TRANSFORM_H |
31 | | |
32 | | #include <string> |
33 | | |
34 | | #include "yb/util/slice.h" |
35 | | |
36 | | namespace rocksdb { |
37 | | |
38 | | class SliceTransform { |
39 | | public: |
40 | 70.6k | virtual ~SliceTransform() {} |
41 | | |
42 | | // Return the name of this transformation. |
43 | | virtual const char* Name() const = 0; |
44 | | |
45 | | // transform a src in domain to a dst in the range |
46 | | virtual Slice Transform(const Slice& src) const = 0; |
47 | | |
48 | | // determine whether this is a valid src upon the function applies |
49 | | virtual bool InDomain(const Slice& src) const = 0; |
50 | | |
51 | | // determine whether dst=Transform(src) for some src |
52 | | virtual bool InRange(const Slice& dst) const = 0; |
53 | | |
54 | | // Transform(s)=Transform(`prefix`) for any s with `prefix` as a prefix. |
55 | | // |
56 | | // This function is not used by RocksDB, but for users. If users pass |
57 | | // Options by string to RocksDB, they might not know what prefix extractor |
58 | | // they are using. This function is to help users can determine: |
59 | | // if they want to iterate all keys prefixing `prefix`, whetherit is |
60 | | // safe to use prefix bloom filter and seek to key `prefix`. |
61 | | // If this function returns true, this means a user can Seek() to a prefix |
62 | | // using the bloom filter. Otherwise, user needs to skip the bloom filter |
63 | | // by setting ReadOptions.total_order_seek = true. |
64 | | // |
65 | | // Here is an example: Suppose we implement a slice transform that returns |
66 | | // the first part of the string after spliting it using deimiter ",": |
67 | | // 1. SameResultWhenAppended("abc,") should return true. If aplying prefix |
68 | | // bloom filter using it, all slices matching "abc:.*" will be extracted |
69 | | // to "abc,", so any SST file or memtable containing any of those key |
70 | | // will not be filtered out. |
71 | | // 2. SameResultWhenAppended("abc") should return false. A user will not |
72 | | // guaranteed to see all the keys matching "abc.*" if a user seek to "abc" |
73 | | // against a DB with the same setting. If one SST file only contains |
74 | | // "abcd,e", the file can be filtered out and the key will be invisible. |
75 | | // |
76 | | // i.e., an implementation always returning false is safe. |
77 | 0 | virtual bool SameResultWhenAppended(const Slice& prefix) const { |
78 | 0 | return false; |
79 | 0 | } |
80 | | }; |
81 | | |
82 | | extern const SliceTransform* NewFixedPrefixTransform(size_t prefix_len); |
83 | | |
84 | | extern const SliceTransform* NewCappedPrefixTransform(size_t cap_len); |
85 | | |
86 | | extern const SliceTransform* NewNoopTransform(); |
87 | | |
88 | | } // namespace rocksdb |
89 | | |
90 | | #endif // ROCKSDB_INCLUDE_ROCKSDB_SLICE_TRANSFORM_H |