1 
2 /**
3  *    Copyright (C) 2018-present MongoDB, Inc.
4  *
5  *    This program is free software: you can redistribute it and/or modify
6  *    it under the terms of the Server Side Public License, version 1,
7  *    as published by MongoDB, Inc.
8  *
9  *    This program is distributed in the hope that it will be useful,
10  *    but WITHOUT ANY WARRANTY; without even the implied warranty of
11  *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
12  *    Server Side Public License for more details.
13  *
14  *    You should have received a copy of the Server Side Public License
15  *    along with this program. If not, see
16  *    <http://www.mongodb.com/licensing/server-side-public-license>.
17  *
18  *    As a special exception, the copyright holders give permission to link the
19  *    code of portions of this program with the OpenSSL library under certain
20  *    conditions as described in each individual source file and distribute
21  *    linked combinations including the program with the OpenSSL library. You
22  *    must comply with the Server Side Public License in all respects for
23  *    all of the code used other than as permitted herein. If you modify file(s)
24  *    with this exception, you may extend this exception to your version of the
25  *    file(s), but you are not obligated to do so. If you do not wish to do so,
26  *    delete this exception statement from your version. If you delete this
27  *    exception statement from all source files in the program, then also delete
28  *    it in the license file.
29  */
30 
31 #pragma once
32 
33 #include "mongo/db/update/modifier_node.h"
34 #include "mongo/stdx/memory.h"
35 
36 namespace mongo {
37 
38 /**
39  * Represents the application of $max or $min to the value at the end of a path.
40  */
41 class CompareNode : public ModifierNode {
42 public:
43     enum class CompareMode { kMax, kMin };
44 
CompareNode(CompareMode mode)45     explicit CompareNode(CompareMode mode) : _mode(mode) {}
46 
47     Status init(BSONElement modExpr, const boost::intrusive_ptr<ExpressionContext>& expCtx) final;
48 
clone()49     std::unique_ptr<UpdateNode> clone() const final {
50         return stdx::make_unique<CompareNode>(*this);
51     }
52 
53     void setCollator(const CollatorInterface* collator) final;
54 
55 protected:
56     ModifyResult updateExistingElement(mutablebson::Element* element,
57                                        std::shared_ptr<FieldRef> elementPath) const final;
58     void setValueForNewElement(mutablebson::Element* element) const final;
59 
allowCreation()60     bool allowCreation() const final {
61         return true;
62     }
63 
canSetObjectValue()64     bool canSetObjectValue() const final {
65         return true;
66     }
67 
68 private:
69     CompareMode _mode;
70     BSONElement _val;
71     const CollatorInterface* _collator = nullptr;
72 };
73 
74 }  // namespace mongo
75