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/**
* Copyright (C) 2013-2014 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 <memory>
#include "mongo/db/catalog/collection.h"
#include "mongo/db/exec/plan_stage.h"
#include "mongo/db/query/canonical_query.h"
#include "mongo/db/record_id.h"
namespace mongo {
class RecordCursor;
/**
* A standalone stage implementing the fast path for key-value retrievals
* via the _id index.
*/
class IDHackStage : public PlanStage {
public:
/** Takes ownership of all the arguments -collection. */
IDHackStage(OperationContext* txn,
const Collection* collection,
CanonicalQuery* query,
WorkingSet* ws);
IDHackStage(OperationContext* txn, Collection* collection, const BSONObj& key, WorkingSet* ws);
virtual ~IDHackStage();
virtual bool isEOF();
virtual StageState work(WorkingSetID* out);
virtual void saveState();
virtual void restoreState(OperationContext* opCtx);
virtual void invalidate(OperationContext* txn, const RecordId& dl, InvalidationType type);
/**
* ID Hack has a very strict criteria for the queries it supports.
*/
static bool supportsQuery(const CanonicalQuery& query);
virtual std::vector<PlanStage*> getChildren() const;
virtual StageType stageType() const {
return STAGE_IDHACK;
}
PlanStageStats* getStats();
virtual const CommonStats* getCommonStats() const;
virtual const SpecificStats* getSpecificStats() const;
static const char* kStageType;
private:
/**
* Marks this stage as done, optionally adds key metadata, and returns PlanStage::ADVANCED.
*
* Called whenever we have a WSM containing the matching obj.
*/
StageState advance(WorkingSetID id, WorkingSetMember* member, WorkingSetID* out);
// transactional context for read locks. Not owned by us
OperationContext* _txn;
// Not owned here.
const Collection* _collection;
std::unique_ptr<RecordCursor> _recordCursor;
// The WorkingSet we annotate with results. Not owned by us.
WorkingSet* _workingSet;
// The value to match against the _id field.
BSONObj _key;
// Have we returned our one document?
bool _done;
// Do we need to add index key metadata for $returnKey?
bool _addKeyMetadata;
// If we want to return a RecordId and it points to something that's not in memory,
// we return a "please page this in" result. We add a RecordFetcher given back to us by the
// storage engine to the WSM. The RecordFetcher is used by the PlanExecutor when it handles
// the fetch request.
WorkingSetID _idBeingPagedIn;
CommonStats _commonStats;
IDHackStats _specificStats;
};
} // namespace mongo
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