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/**
* Copyright (C) 2013 10gen 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/exec/plan_stage.h"
#include "mongo/db/exec/projection_exec.h"
#include "mongo/db/jsobj.h"
#include "mongo/db/matcher/expression.h"
#include "mongo/db/record_id.h"
namespace mongo {
class CollatorInterface;
class ExtensionsCallback;
struct ProjectionStageParams {
enum ProjectionImplementation {
// The default case. Will handle every projection.
NO_FAST_PATH,
// The projection is simple inclusion and is totally covered by one index.
COVERED_ONE_INDEX,
// The projection is simple inclusion and we expect an object.
SIMPLE_DOC
};
ProjectionStageParams(const ExtensionsCallback& wc) : extensionsCallback(&wc) {}
ProjectionImplementation projImpl = NO_FAST_PATH;
// The projection object. We lack a ProjectionExpression or similar so we use a BSONObj.
BSONObj projObj;
// If we have a positional or elemMatch projection we need a MatchExpression to pull out the
// right data.
// Not owned here, we do not take ownership.
const MatchExpression* fullExpression = nullptr;
// If (COVERED_ONE_INDEX == projObj) this is the key pattern we're extracting covered data
// from. Otherwise, this field is ignored.
BSONObj coveredKeyObj;
// Used for creating context for the match extensions processing. Not owned.
const ExtensionsCallback* extensionsCallback;
// The collator this operation should use to compare strings. If null, the collation is a simple
// binary compare.
const CollatorInterface* collator = nullptr;
};
/**
* This stage computes a projection.
*/
class ProjectionStage final : public PlanStage {
public:
ProjectionStage(OperationContext* opCtx,
const ProjectionStageParams& params,
WorkingSet* ws,
PlanStage* child);
bool isEOF() final;
StageState doWork(WorkingSetID* out) final;
StageType stageType() const final {
return STAGE_PROJECTION;
}
std::unique_ptr<PlanStageStats> getStats();
const SpecificStats* getSpecificStats() const final;
using FieldSet = StringMap<bool>; // Value is unused.
/**
* Given the projection spec for a simple inclusion projection,
* 'projObj', populates 'includedFields' with the set of field
* names to be included.
*/
static void getSimpleInclusionFields(const BSONObj& projObj, FieldSet* includedFields);
/**
* Applies a simple inclusion projection to 'in', including
* only the fields specified by 'includedFields'.
*
* The resulting document is constructed using 'bob'.
*/
static void transformSimpleInclusion(const BSONObj& in,
const FieldSet& includedFields,
BSONObjBuilder& bob);
static const char* kStageType;
private:
Status transform(WorkingSetMember* member);
std::unique_ptr<ProjectionExec> _exec;
// _ws is not owned by us.
WorkingSet* _ws;
// Stats
ProjectionStats _specificStats;
// Fast paths:
ProjectionStageParams::ProjectionImplementation _projImpl;
// Used by all projection implementations.
BSONObj _projObj;
// Data used for both SIMPLE_DOC and COVERED_ONE_INDEX paths.
// Has the field names present in the simple projection.
FieldSet _includedFields;
//
// Used for the COVERED_ONE_INDEX path.
//
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;
};
} // namespace mongo
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