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/**
* 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 {
/**
* 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:
/**
* This class defines the minimal interface that every parser wishing to take advantage of
* DocumentSourceSingleDocumentTransformation must implement.
*
* This interface ensures that DocumentSourceSingleDocumentTransformations are passed parsed
* objects that can execute the transformation and provide additional features like
* serialization and reporting and returning dependencies. The parser must also provide
* implementations for optimizing and adding the expression context, even if those functions do
* nothing.
*/
class TransformerInterface {
public:
enum class TransformerType {
kExclusionProjection,
kInclusionProjection,
kComputedProjection,
kReplaceRoot,
kChangeStreamTransformation,
};
virtual ~TransformerInterface() = default;
virtual Document applyTransformation(const Document& input) = 0;
virtual TransformerType getType() const = 0;
virtual void optimize() = 0;
virtual DocumentSource::GetDepsReturn addDependencies(DepsTracker* deps) const = 0;
virtual GetModPathsReturn getModifiedPaths() const = 0;
/**
* Returns the document describing this stage, not including the stage name. For example,
* should return just {_id: 0, x: 1} for the stage parsed from {$project: {_id: 0, x: 1}}.
*/
virtual Document serializeStageOptions(
boost::optional<ExplainOptions::Verbosity> explain) const = 0;
/**
* Returns true if this transformer is an inclusion projection and is a subset of
* 'proj', which must be a valid projection specification. For example, if this
* TransformerInterface represents the inclusion projection
*
* {a: 1, b: 1, c: 1}
*
* then it is a subset of the projection {a: 1, c: 1}, and this function returns
* true.
*/
virtual bool isSubsetOfProjection(const BSONObj& proj) const {
return false;
}
};
DocumentSourceSingleDocumentTransformation(
const boost::intrusive_ptr<ExpressionContext>& pExpCtx,
std::unique_ptr<TransformerInterface> parsedTransform,
std::string name);
// virtuals from DocumentSource
const char* getSourceName() const final;
GetNextResult getNext() final;
boost::intrusive_ptr<DocumentSource> optimize() final;
Value serialize(boost::optional<ExplainOptions::Verbosity> explain = boost::none) const final;
DocumentSource::GetDepsReturn getDependencies(DepsTracker* deps) const final;
GetModPathsReturn getModifiedPaths() const final;
StageConstraints constraints() const final {
StageConstraints constraints;
constraints.canSwapWithMatch = true;
return constraints;
}
TransformerInterface::TransformerType getType() const {
return _parsedTransform->getType();
}
bool isSubsetOfProjection(const BSONObj& proj) const {
return _parsedTransform->isSubsetOfProjection(proj);
}
protected:
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;
};
} // namespace mongo
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