1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
|
/**
* Copyright (C) 2022-present MongoDB, Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the Server Side Public License, version 1,
* as published by MongoDB, Inc.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* Server Side Public License for more details.
*
* You should have received a copy of the Server Side Public License
* along with this program. If not, see
* <http://www.mongodb.com/licensing/server-side-public-license>.
*
* As a special exception, the copyright holders give permission to link the
* code of portions of this program with the OpenSSL library under certain
* conditions as described in each individual source file and distribute
* linked combinations including the program with the OpenSSL library. You
* must comply with the Server Side Public License in all respects for
* all of the code used other than as permitted herein. If you modify file(s)
* with this exception, you may extend this exception to your version of the
* file(s), but you are not obligated to do so. If you do not wish to do so,
* delete this exception statement from your version. If you delete this
* exception statement from all source files in the program, then also delete
* it in the license file.
*/
#pragma once
#include "mongo/db/pipeline/field_path.h"
namespace mongo::monotonic {
enum class State { NonMonotonic, Constant, Increasing, Decreasing };
/**
* Given monotonic states of function f(x), returns monotonic state of -f(x). If function is
* constant or non monotonic, it will remain the same. If it is increasing, it will become
* decreasing, and vice versa.
*/
State opposite(State state);
/**
* Given monotonic states of functions f(x) and g(x), returns monotonic state of f(x)+g(x). Plus
* operator can be replaced with any operation that preserves monotonic behavior.
*
* If any argument is non monotonic, then the whole function is non monotonic.
* If one of the arguments is a constant, then the whole function has the same monotonic state as
* the other argument. If all arguments have the the same monotonic state, then the whole function
* has the same monotonic state. Otherwise, the result is NonMonotonic.
*/
State combine(State lhs, State rhs);
template <typename ExpressionsContainer>
State combineExpressions(const FieldPath& sortedFieldPath, const ExpressionsContainer& container) {
return std::accumulate(container.begin(),
container.end(),
State::Constant,
[&](State state, const auto& expression) {
if (expression == nullptr) {
return state;
}
return combine(state,
expression->getMonotonicState(sortedFieldPath));
});
}
} // namespace mongo::monotonic
|