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
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
|
/**
* Copyright (C) 2018-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.
*/
#include "mongo/platform/basic.h"
#include "mongo/db/pipeline/document_source_sequential_document_cache.h"
#include "mongo/db/pipeline/document_source_match.h"
namespace mongo {
constexpr StringData DocumentSourceSequentialDocumentCache::kStageName;
DocumentSourceSequentialDocumentCache::DocumentSourceSequentialDocumentCache(
const boost::intrusive_ptr<ExpressionContext>& expCtx, SequentialDocumentCache* cache)
: DocumentSource(kStageName, expCtx), _cache(cache) {
invariant(_cache);
invariant(!_cache->isAbandoned());
if (_cache->isServing()) {
_cache->restartIteration();
}
}
DocumentSource::GetNextResult DocumentSourceSequentialDocumentCache::doGetNext() {
// Either we're reading from the cache, or we have an input source to build the cache from.
invariant(pSource || _cache->isServing());
if (_cacheIsEOF) {
return GetNextResult::makeEOF();
}
if (_cache->isServing()) {
auto nextDoc = _cache->getNext();
if (nextDoc) {
return std::move(*nextDoc);
}
_cacheIsEOF = true;
return GetNextResult::makeEOF();
}
auto nextResult = pSource->getNext();
if (!_cache->isAbandoned()) {
if (nextResult.isEOF()) {
_cache->freeze();
_cacheIsEOF = true;
} else {
_cache->add(nextResult.getDocument());
}
}
return nextResult;
}
Pipeline::SourceContainer::iterator DocumentSourceSequentialDocumentCache::doOptimizeAt(
Pipeline::SourceContainer::iterator itr, Pipeline::SourceContainer* container) {
// The DocumentSourceSequentialDocumentCache should always be the last stage in the pipeline
// pre-optimization. By the time optimization reaches this point, all preceding stages are in
// the final positions which they would have occupied if no cache stage was present.
invariant(_hasOptimizedPos || std::next(itr) == container->end());
invariant((*itr).get() == this);
// If we have already optimized our position, stay where we are.
if (_hasOptimizedPos) {
return std::next(itr);
}
// Mark this stage as having optimized itself.
_hasOptimizedPos = true;
// If the cache is the only stage in the pipeline, return immediately.
if (itr == container->begin() && std::next(itr) == container->end()) {
return container->end();
}
// Pop the cache stage off the back of the pipeline.
auto cacheStage = std::move(*itr);
container->erase(itr);
// Get all variable IDs defined in this scope.
auto varIDs = pExpCtx->variablesParseState.getDefinedVariableIDs();
auto prefixSplit = container->begin();
// In the context of this optimization, we are only interested in figuring out
// which external variables are referenced in the pipeline. We are not attempting
// to enforce that any referenced metadata are in fact unavailable, this is done
// elsewhere. So without knowledge of what metadata is in fact unavailable, here
// we "lie" and say that all metadata is available to avoid tripping any
// assertions.
DepsTracker deps(DepsTracker::kNoMetadata);
// Iterate through the pipeline stages until we find one which cannot be cached.
// A stage cannot be cached if it either:
// 1. does not support dependency tracking, and may thus require the full object and metadata.
// 2. depends on a variable defined in this scope, or
// 3. generates random numbers.
DocumentSource* lastPtr = nullptr;
std::set<Variables::Id> prefixVarRefs;
for (; prefixSplit != container->end(); ++prefixSplit) {
(*prefixSplit)->addVariableRefs(&prefixVarRefs);
if (((*prefixSplit)->getDependencies(&deps) == DepsTracker::State::NOT_SUPPORTED) ||
Variables::hasVariableReferenceTo(prefixVarRefs, varIDs) || deps.needRandomGenerator) {
break;
}
lastPtr = prefixSplit->get();
}
// The 'prefixSplit' iterator is now pointing to the first stage of the correlated suffix. If
// the split point is the first stage, then the entire pipeline is correlated and we should not
// attempt to perform any caching. Abandon the cache and return.
if (prefixSplit == container->begin()) {
_cache->abandon();
return container->end();
}
// If the cache has been populated and is serving results, remove the non-correlated prefix.
if (_cache->isServing()) {
// Need to dispose last stage to be removed.
Pipeline::stitch(container);
lastPtr->dispose();
container->erase(container->begin(), prefixSplit);
}
container->insert(prefixSplit, std::move(cacheStage));
return container->end();
}
Value DocumentSourceSequentialDocumentCache::serialize(SerializationOptions opts) const {
if (opts.verbosity) {
return Value(Document{
{kStageName,
Document{{"maxSizeBytes"_sd,
opts.serializeLiteralValue(static_cast<long long>(_cache->maxSizeBytes()))},
{"status"_sd,
_cache->isBuilding() ? "kBuilding"_sd
: _cache->isServing() ? "kServing"_sd
: "kAbandoned"_sd}}}});
}
return Value();
}
} // namespace mongo
|
