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
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
|
/**
* Copyright (C) 2021-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/document_source.h"
#include "mongo/db/pipeline/document_source_change_stream.h"
namespace mongo {
/**
* Part of the change stream API machinery used to look up the pre-image of a document.
*
* After a document that should have its pre-image included is transformed from the oplog,
* its "fullDocumentBeforeChange" field shall be the optime of the noop oplog entry containing the
* pre-image. This stage replaces that field with the actual pre-image document.
*/
class DocumentSourceChangeStreamAddPreImage final : public DocumentSource {
public:
static constexpr StringData kStageName = "$_internalChangeStreamAddPreImage"_sd;
static constexpr StringData kFullDocumentBeforeChangeFieldName =
DocumentSourceChangeStream::kFullDocumentBeforeChangeField;
static constexpr StringData kPreImageIdFieldName = DocumentSourceChangeStream::kPreImageIdField;
/**
* Creates a DocumentSourceChangeStreamAddPreImage stage.
*/
static boost::intrusive_ptr<DocumentSourceChangeStreamAddPreImage> create(
const boost::intrusive_ptr<ExpressionContext>& expCtx,
const DocumentSourceChangeStreamSpec& spec);
static boost::intrusive_ptr<DocumentSourceChangeStreamAddPreImage> createFromBson(
BSONElement elem, const boost::intrusive_ptr<ExpressionContext>& expCtx);
// Retrieves the pre-image document given the specified 'preImageId'. Returns boost::none if no
// such pre-image is available.
static boost::optional<Document> lookupPreImage(boost::intrusive_ptr<ExpressionContext> pExpCtx,
const Document& preImageId);
DocumentSourceChangeStreamAddPreImage(const boost::intrusive_ptr<ExpressionContext>& expCtx,
FullDocumentBeforeChangeModeEnum mode)
: DocumentSource(kStageName, expCtx), _fullDocumentBeforeChangeMode(mode) {
// This stage should never be created with FullDocumentBeforeChangeMode::kOff.
invariant(_fullDocumentBeforeChangeMode != FullDocumentBeforeChangeModeEnum::kOff);
}
/**
* Only modifies: "fullDocumentBeforeChange" and "preImageId".
*/
GetModPathsReturn getModifiedPaths() const final {
return {GetModPathsReturn::Type::kFiniteSet,
{kFullDocumentBeforeChangeFieldName.toString(), kPreImageIdFieldName.toString()},
{}};
}
StageConstraints constraints(Pipeline::SplitState pipeState) const final {
invariant(pipeState != Pipeline::SplitState::kSplitForShards);
StageConstraints constraints(StreamType::kStreaming,
PositionRequirement::kNone,
HostTypeRequirement::kAnyShard,
DiskUseRequirement::kNoDiskUse,
FacetRequirement::kNotAllowed,
TransactionRequirement::kNotAllowed,
LookupRequirement::kNotAllowed,
UnionRequirement::kNotAllowed,
ChangeStreamRequirement::kChangeStreamStage);
constraints.canSwapWithMatch = true;
return constraints;
}
// Conceptually, this stage must always run on the shards part of the pipeline. At
// present, however, pre-image retrieval is not supported in a sharded cluster, and
// so the distributed plan logic will not be used.
boost::optional<DistributedPlanLogic> distributedPlanLogic() final {
return DistributedPlanLogic{this, nullptr, boost::none};
}
DepsTracker::State getDependencies(DepsTracker* deps) const {
deps->fields.insert(DocumentSourceChangeStream::kPreImageIdField.toString());
// This stage does not restrict the output fields to a finite set, and has no impact on
// whether metadata is available or needed.
return DepsTracker::State::SEE_NEXT;
}
Value serialize(boost::optional<ExplainOptions::Verbosity> explain = boost::none) const final;
const char* getSourceName() const final {
return kStageName.rawData();
}
private:
/**
* Performs the lookup to retrieve the full pre-image document for applicable operations.
*/
GetNextResult doGetNext() final;
// Determines whether pre-images are strictly required or may be included only when available.
FullDocumentBeforeChangeModeEnum _fullDocumentBeforeChangeMode =
FullDocumentBeforeChangeModeEnum::kOff;
};
} // namespace mongo
|
