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
|
/**
* Copyright (C) 2019-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 <deque>
#include "mongo/db/pipeline/document_source.h"
namespace mongo {
/**
* A DocumentSource which re-spools a queue of documents loaded into it. This stage does not
* retrieve any input from an earlier stage. It can be useful to adapt the usual pull-based model of
* a pipeline to more of a push-based model by pushing documents to feed through the pipeline into
* this queue stage.
*/
class DocumentSourceQueue : public DocumentSource {
public:
static constexpr StringData kStageName = "$queue"_sd;
static boost::intrusive_ptr<DocumentSourceQueue> create(
const boost::intrusive_ptr<ExpressionContext>& expCtx,
boost::optional<StringData> aliasStageName = boost::none);
DocumentSourceQueue(std::deque<GetNextResult> results,
const boost::intrusive_ptr<ExpressionContext>& expCtx,
boost::optional<StringData> aliasStageName = boost::none);
~DocumentSourceQueue() override = default;
const char* getSourceName() const override;
Value serialize(boost::optional<ExplainOptions::Verbosity> explain) const override;
StageConstraints constraints(Pipeline::SplitState pipeState) const override {
StageConstraints constraints{StreamType::kStreaming,
PositionRequirement::kFirst,
HostTypeRequirement::kLocalOnly,
DiskUseRequirement::kNoDiskUse,
FacetRequirement::kNotAllowed,
TransactionRequirement::kAllowed,
LookupRequirement::kAllowed,
UnionRequirement::kAllowed};
constraints.requiresInputDocSource = false;
constraints.isIndependentOfAnyCollection = true;
return constraints;
}
/**
* This stage does not modify anything.
*/
GetModPathsReturn getModifiedPaths() const override {
return {GetModPathsReturn::Type::kFiniteSet, std::set<std::string>{}, {}};
}
/**
* This stage does not depend on anything.
*/
DepsTracker::State getDependencies(DepsTracker* deps) const override {
return DepsTracker::SEE_NEXT;
}
boost::optional<DistributedPlanLogic> distributedPlanLogic() override {
return boost::none;
}
template <class... Args>
GetNextResult& emplace_back(Args&&... args) {
return _queue.emplace_back(std::forward<Args>(args)...);
}
void push_back(GetNextResult&& result) {
_queue.push_back(std::move(result));
}
void push_back(const GetNextResult& result) {
_queue.push_back(result);
}
static boost::intrusive_ptr<DocumentSource> createFromBson(
BSONElement elem, const boost::intrusive_ptr<ExpressionContext>& expCtx);
protected:
GetNextResult doGetNext() override;
// Return documents from front of queue.
std::deque<GetNextResult> _queue;
// An optional alias name is provided for cases like $documents where we want an error message
// to indicate the name the user provided, not the internal $queue name.
boost::optional<StringData> _aliasStageName = boost::none;
};
} // namespace mongo
|
