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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 "mongo/db/exec/plan_stage.h"
#include "mongo/db/exec/projection_executor.h"
#include "mongo/db/jsobj.h"
#include "mongo/db/matcher/expression.h"
#include "mongo/db/query/projection_ast.h"
#include "mongo/db/record_id.h"
namespace mongo {
/**
* This stage computes a projection. This is an abstract base class for various projection
* implementations.
*/
class ProjectionStage : public PlanStage {
protected:
ProjectionStage(ExpressionContext* expCtx,
const BSONObj& projObj,
WorkingSet* ws,
std::unique_ptr<PlanStage> child,
const char* stageType);
public:
bool isEOF() final;
StageState doWork(WorkingSetID* out) final;
std::unique_ptr<PlanStageStats> getStats() final;
const SpecificStats* getSpecificStats() const final {
return &_specificStats;
}
protected:
using FieldSet = StringSet;
// The raw BSON projection used to populate projection stats. Optional, since it is required
// only in explain mode.
boost::optional<BSONObj> _projObj;
private:
/**
* Runs either the default complete implementation or a fast path depending on how this was
* constructed.
*/
virtual void transform(WorkingSetMember* member) const = 0;
// Used to retrieve a WorkingSetMember as part of 'doWork()'.
WorkingSet& _ws;
// Populated by 'getStats()'.
ProjectionStats _specificStats;
};
/**
* The default case. Can handle every projection.
*/
class ProjectionStageDefault final : public ProjectionStage {
public:
/**
* ProjectionNodeDefault should use this for construction.
*/
ProjectionStageDefault(boost::intrusive_ptr<ExpressionContext> expCtx,
const BSONObj& projObj,
const projection_ast::Projection* projection,
WorkingSet* ws,
std::unique_ptr<PlanStage> child);
StageType stageType() const final {
return STAGE_PROJECTION_DEFAULT;
}
private:
void transform(WorkingSetMember* member) const final;
// Represents all metadata used in the projection.
const QueryMetadataBitSet _requestedMetadata;
const projection_ast::ProjectType _projectType;
std::unique_ptr<projection_executor::ProjectionExecutor> _executor;
};
/**
* This class is used when the projection is totally covered by one index and the following rules
* are met: the projection consists only of inclusions e.g. '{field: 1}', it has no $meta
* projections, it is not a returnKey projection and it has no dotted fields.
*/
class ProjectionStageCovered final : public ProjectionStage {
public:
/**
* ProjectionNodeCovered should obtain a fast-path object through this constructor.
*/
ProjectionStageCovered(ExpressionContext* expCtx,
const BSONObj& projObj,
const projection_ast::Projection* projection,
WorkingSet* ws,
std::unique_ptr<PlanStage> child,
const BSONObj& coveredKeyObj);
StageType stageType() const final {
return STAGE_PROJECTION_COVERED;
}
private:
void transform(WorkingSetMember* member) const final;
// Field names present in the simple projection.
FieldSet _includedFields;
// This is the key pattern we're extracting covered data from. It is maintained here since
// strings derived from it depend on its lifetime.
BSONObj _coveredKeyObj;
// Field names can be empty in 2.4 and before so we can't use them as a sentinel value.
// If the i-th entry is true we include the i-th field in the key.
std::vector<bool> _includeKey;
// If the i-th entry of _includeKey is true this is the field name for the i-th key field.
std::vector<StringData> _keyFieldNames;
};
/**
* This class is used when we expect an object and the following rules are met: it has no $meta
* projections, it is not a returnKey projection and it has no dotted fields.
*/
class ProjectionStageSimple final : public ProjectionStage {
public:
/**
* ProjectionNodeSimple should obtain a fast-path object through this constructor.
*/
ProjectionStageSimple(ExpressionContext* expCtx,
const BSONObj& projObj,
const projection_ast::Projection* projection,
WorkingSet* ws,
std::unique_ptr<PlanStage> child);
StageType stageType() const final {
return STAGE_PROJECTION_SIMPLE;
}
private:
void transform(WorkingSetMember* member) const final;
const projection_ast::ProjectType _projectType;
FieldSet _fields;
};
} // namespace mongo
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