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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/diskloc.h"
#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"
namespace mongo {
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 MatchExpressionParser::WhereCallback& wc)
: projImpl(NO_FAST_PATH), fullExpression(NULL), whereCallback(&wc) { }
ProjectionImplementation projImpl;
// 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;
// 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 $where clause processing. Not owned.
const MatchExpressionParser::WhereCallback* whereCallback;
};
/**
* This stage computes a projection.
*/
class ProjectionStage : public PlanStage {
public:
ProjectionStage(const ProjectionStageParams& params,
WorkingSet* ws,
PlanStage* child);
virtual ~ProjectionStage();
virtual bool isEOF();
virtual StageState work(WorkingSetID* out);
virtual void prepareToYield();
virtual void recoverFromYield(OperationContext* opCtx);
virtual void invalidate(const DiskLoc& dl, InvalidationType type);
virtual std::vector<PlanStage*> getChildren() const;
virtual StageType stageType() const { return STAGE_PROJECTION; }
PlanStageStats* getStats();
virtual const CommonStats* getCommonStats();
virtual const SpecificStats* getSpecificStats();
typedef unordered_set<StringData, StringData::Hasher> FieldSet;
/**
* 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);
scoped_ptr<ProjectionExec> _exec;
// _ws is not owned by us.
WorkingSet* _ws;
scoped_ptr<PlanStage> _child;
// Stats
CommonStats _commonStats;
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.
unordered_set<StringData, StringData::Hasher> _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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