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/**
* 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.
*/
#pragma once
#include <type_traits>
#include "mongo/db/pipeline/document_source.h"
#include "mongo/db/pipeline/transformer_interface.h"
namespace mongo {
/**
* This class is for DocumentSources that take in and return one document at a time, in a 1:1
* transformation. It should only be used via an alias that passes the transformation logic through
* a ParsedSingleDocumentTransformation. It is not a registered DocumentSource, and it cannot be
* created from BSON.
*/
class DocumentSourceSingleDocumentTransformation final : public DocumentSource {
public:
virtual boost::intrusive_ptr<DocumentSource> clone() const {
auto list = DocumentSource::parse(pExpCtx, serialize().getDocument().toBson());
invariant(list.size() == 1);
return list.front();
}
DocumentSourceSingleDocumentTransformation(
const boost::intrusive_ptr<ExpressionContext>& pExpCtx,
std::unique_ptr<TransformerInterface> parsedTransform,
const StringData name,
bool independentOfAnyCollection);
// virtuals from DocumentSource
const char* getSourceName() const final;
boost::intrusive_ptr<DocumentSource> optimize() final;
Value serialize(boost::optional<ExplainOptions::Verbosity> explain = boost::none) const final;
DepsTracker::State getDependencies(DepsTracker* deps) const final;
GetModPathsReturn getModifiedPaths() const final;
StageConstraints constraints(Pipeline::SplitState pipeState) const final {
StageConstraints constraints(StreamType::kStreaming,
PositionRequirement::kNone,
HostTypeRequirement::kNone,
DiskUseRequirement::kNoDiskUse,
FacetRequirement::kAllowed,
TransactionRequirement::kAllowed,
LookupRequirement::kAllowed,
UnionRequirement::kAllowed,
ChangeStreamRequirement::kAllowlist);
constraints.canSwapWithMatch = true;
constraints.canSwapWithSkippingOrLimitingStage = true;
constraints.isAllowedWithinUpdatePipeline = true;
// This transformation could be part of a 'collectionless' change stream on an entire
// database or cluster, mark as independent of any collection if so.
constraints.isIndependentOfAnyCollection = _isIndependentOfAnyCollection;
return constraints;
}
boost::optional<DistributedPlanLogic> distributedPlanLogic() final {
return boost::none;
}
TransformerInterface::TransformerType getType() const {
return _parsedTransform->getType();
}
const auto& getTransformer() const {
return *_parsedTransform;
}
/**
* Extract computed projection(s) depending on the 'oldName' argument if the transformation is
* of type inclusion projection or computed projection. Extraction is not allowed if the name of
* the projection is in the 'reservedNames' set. The function returns a pair of <BSONObj, bool>.
* The BSONObj contains the computed projections in which the 'oldName' is substituted for the
* 'newName'. The boolean flag is true if the original projection has become empty after the
* extraction and can be deleted by the caller.
*
* For transformation of type inclusion projection the computed projections are replaced with a
* projected field or an identity projection depending on their position in the order of
* additional fields.
* For transformation of type computed projection the extracted computed projections are
* removed.
*
* The function has no effect for exclusion projections, or if there are no computed
* projections, or the computed expression depends on other fields than the oldName.
*/
std::pair<BSONObj, bool> extractComputedProjections(const StringData& oldName,
const StringData& newName,
const std::set<StringData>& reservedNames) {
return _parsedTransform->extractComputedProjections(oldName, newName, reservedNames);
}
/**
* If this transformation is a project, removes and returns a BSONObj representing the part of
* this project that depends only on 'oldName'. Also returns a bool indicating whether this
* entire project is extracted. In the extracted $project, 'oldName' is renamed to 'newName'.
* 'oldName' should not be dotted.
*/
std::pair<BSONObj, bool> extractProjectOnFieldAndRename(const StringData& oldName,
const StringData& newName) {
return _parsedTransform->extractProjectOnFieldAndRename(oldName, newName);
}
protected:
GetNextResult doGetNext() final;
void doDispose() final;
Pipeline::SourceContainer::iterator doOptimizeAt(Pipeline::SourceContainer::iterator itr,
Pipeline::SourceContainer* container) final;
private:
// Stores transformation logic.
std::unique_ptr<TransformerInterface> _parsedTransform;
// Specific name of the transformation.
std::string _name;
// Set to true if this transformation stage can be run on the collectionless namespace.
bool _isIndependentOfAnyCollection;
// Cached stage options in case this DocumentSource is disposed before serialized (e.g. explain
// with a sort which will auto-dispose of the pipeline).
Document _cachedStageOptions;
};
} // namespace mongo
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