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author | Charlie Swanson <charlie.swanson@mongodb.com> | 2016-10-21 17:06:31 -0400 |
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committer | Charlie Swanson <charlie.swanson@mongodb.com> | 2016-10-24 11:47:57 -0400 |
commit | 4fb763d868070414ca0af76b84ff8937b3773832 (patch) | |
tree | 54b3e49dc04a483759dd7042bda1d4e97cec581f /src/mongo/db/pipeline/document_source_limit.h | |
parent | 7f4670f708361c6da29ba5503e000964a035fe6f (diff) | |
download | mongo-4fb763d868070414ca0af76b84ff8937b3773832.tar.gz |
SERVER-22632 Split up document_source.h into one header per stage.
Diffstat (limited to 'src/mongo/db/pipeline/document_source_limit.h')
-rw-r--r-- | src/mongo/db/pipeline/document_source_limit.h | 102 |
1 files changed, 102 insertions, 0 deletions
diff --git a/src/mongo/db/pipeline/document_source_limit.h b/src/mongo/db/pipeline/document_source_limit.h new file mode 100644 index 00000000000..9c04213045d --- /dev/null +++ b/src/mongo/db/pipeline/document_source_limit.h @@ -0,0 +1,102 @@ +/** + * Copyright (C) 2016 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" + +namespace mongo { + +class DocumentSourceLimit final : public DocumentSource, public SplittableDocumentSource { +public: + // virtuals from DocumentSource + GetNextResult getNext() final; + const char* getSourceName() const final; + BSONObjSet getOutputSorts() final { + return pSource ? pSource->getOutputSorts() + : SimpleBSONObjComparator::kInstance.makeBSONObjSet(); + } + + /** + * Attempts to combine with a subsequent $limit stage, setting 'limit' appropriately. + */ + Pipeline::SourceContainer::iterator doOptimizeAt(Pipeline::SourceContainer::iterator itr, + Pipeline::SourceContainer* container) final; + Value serialize(bool explain = false) const final; + + GetDepsReturn getDependencies(DepsTracker* deps) const final { + return SEE_NEXT; // This doesn't affect needed fields + } + + /** + Create a new limiting DocumentSource. + + @param pExpCtx the expression context for the pipeline + @returns the DocumentSource + */ + static boost::intrusive_ptr<DocumentSourceLimit> create( + const boost::intrusive_ptr<ExpressionContext>& pExpCtx, long long limit); + + // Virtuals for SplittableDocumentSource + // Need to run on rounter. Running on shard as well is an optimization. + boost::intrusive_ptr<DocumentSource> getShardSource() final { + return this; + } + boost::intrusive_ptr<DocumentSource> getMergeSource() final { + return this; + } + + long long getLimit() const { + return _limit; + } + void setLimit(long long newLimit) { + _limit = newLimit; + } + + /** + Create a limiting DocumentSource from BSON. + + This is a convenience method that uses the above, and operates on + a BSONElement that has been deteremined to be an Object with an + element named $limit. + + @param pBsonElement the BSONELement that defines the limit + @param pExpCtx the expression context + @returns the grouping DocumentSource + */ + static boost::intrusive_ptr<DocumentSource> createFromBson( + BSONElement elem, const boost::intrusive_ptr<ExpressionContext>& pExpCtx); + +private: + DocumentSourceLimit(const boost::intrusive_ptr<ExpressionContext>& pExpCtx, long long limit); + + long long _limit; + long long _nReturned = 0; +}; + +} // namespace mongo |