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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 <memory>
#include "mongo/db/exec/requires_index_stage.h"
#include "mongo/db/query/canonical_query.h"
#include "mongo/db/record_id.h"
namespace mongo {
class IndexAccessMethod;
class RecordCursor;
/**
* A standalone stage implementing the fast path for key-value retrievals via the _id index. Since
* the _id index always has the collection default collation, the IDHackStage can only be used when
* the query's collation is equal to the collection default.
*/
class IDHackStage final : public RequiresIndexStage {
public:
/** Takes ownership of all the arguments -collection. */
IDHackStage(OperationContext* opCtx,
CanonicalQuery* query,
WorkingSet* ws,
const IndexDescriptor* descriptor);
IDHackStage(OperationContext* opCtx,
const BSONObj& key,
WorkingSet* ws,
const IndexDescriptor* descriptor);
~IDHackStage();
bool isEOF() final;
StageState doWork(WorkingSetID* out) final;
void doDetachFromOperationContext() final;
void doReattachToOperationContext() final;
/**
* ID Hack has a very strict criteria for the queries it supports.
*/
static bool supportsQuery(Collection* collection, const CanonicalQuery& query);
StageType stageType() const final {
return STAGE_IDHACK;
}
std::unique_ptr<PlanStageStats> getStats();
const SpecificStats* getSpecificStats() const final;
static const char* kStageType;
protected:
void doSaveStateRequiresIndex() final;
void doRestoreStateRequiresIndex() final;
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);
std::unique_ptr<SeekableRecordCursor> _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 = false;
// Do we need to add index key metadata for returnKey?
bool _addKeyMetadata = false;
IDHackStats _specificStats;
};
} // namespace mongo
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