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Diffstat (limited to 'src/mongo/db/pipeline/document_source_sequential_document_cache.h')
-rw-r--r-- | src/mongo/db/pipeline/document_source_sequential_document_cache.h | 85 |
1 files changed, 85 insertions, 0 deletions
diff --git a/src/mongo/db/pipeline/document_source_sequential_document_cache.h b/src/mongo/db/pipeline/document_source_sequential_document_cache.h new file mode 100644 index 00000000000..af96ae8e2ab --- /dev/null +++ b/src/mongo/db/pipeline/document_source_sequential_document_cache.h @@ -0,0 +1,85 @@ +/** + * Copyright (C) 2017 MongoDB Inc. + * + * This program is free software: you can redistribute it and/or modify + * it under the terms of the GNU Affero General Public License, version 3, + * as published by the Free Software Foundation. + * + * 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 + * GNU Affero General Public License for more details. + * + * You should have received a copy of the GNU Affero General Public License + * along with this program. If not, see <http://www.gnu.org/licenses/>. + * + * 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 GNU Affero General 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/sequential_document_cache.h" + +namespace mongo { + +/** + * A DocumentSourceSequentialDocumentCache manages an underlying SequentialDocumentCache. If the + * cache's status is 'kBuilding', DocumentSourceSequentialDocumentCache will retrieve documents from + * the preceding pipeline stage, add them to the cache, and pass them through to the following + * pipeline stage. If the cache is in 'kServing' mode, DocumentSourceSequentialDocumentCache will + * return results directly from the cache rather than from a preceding stage. It does not have a + * registered parser and cannot be created from BSON. + */ +class DocumentSourceSequentialDocumentCache final : public DocumentSource { +public: + static constexpr StringData kStageName = "$sequentialCache"_sd; + + const char* getSourceName() const final { + return kStageName.rawData(); + } + + StageConstraints constraints() const { + StageConstraints constraints; + + if (_cache->isServing()) { + constraints.requiredPosition = PositionRequirement::kFirst; + constraints.requiresInputDocSource = false; + } + + return constraints; + } + + GetNextResult getNext() final; + + static boost::intrusive_ptr<DocumentSourceSequentialDocumentCache> create( + const boost::intrusive_ptr<ExpressionContext>& pExpCtx, SequentialDocumentCache* cache) { + return new DocumentSourceSequentialDocumentCache(pExpCtx, cache); + } + +protected: + Pipeline::SourceContainer::iterator doOptimizeAt(Pipeline::SourceContainer::iterator itr, + Pipeline::SourceContainer* container) final; + +private: + DocumentSourceSequentialDocumentCache(const boost::intrusive_ptr<ExpressionContext>& expCtx, + SequentialDocumentCache* cache); + + Value serialize(boost::optional<ExplainOptions::Verbosity> explain = boost::none) const final; + + SequentialDocumentCache* _cache; + + bool _hasOptimizedPos = false; +}; + +} // namesace mongo |