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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/catalog/collection.h"
#include "mongo/db/catalog/database.h"
#include "mongo/db/catalog/database_holder.h"
#include "mongo/db/exec/plan_stage.h"
#include "mongo/util/uuid.h"
namespace mongo {
/**
* A base class for plan stages which access a collection. In addition to providing derived classes
* access to the Collection pointer, the primary purpose of this class is to assume responsibility
* for checking that the collection is still valid (e.g. has not been dropped) when recovering from
* yield.
*
* Subclasses must implement doSaveStateRequiresCollection() and doRestoreStateRequiresCollection()
* in order to supply custom yield preparation or yield recovery logic.
*
* Templated on 'CollectionT', which may be instantiated using either Collection* or const
* Collection*. This abstracts the implementation of this base class for use by derived classes
* which read (e.g. COLLSCAN and MULTI_ITERATOR) and derived classes that write (e.g. UPDATE and
* DELETE). Derived classes should use the 'RequiresCollectionStage' or
* 'RequiresMutableCollectionStage' aliases provided below.
*/
template <typename CollectionT>
class RequiresCollectionStageBase : public PlanStage {
public:
RequiresCollectionStageBase(const char* stageType, OperationContext* opCtx, CollectionT coll)
: PlanStage(stageType, opCtx),
_collection(coll),
_collectionUUID(_collection->uuid()),
_databaseEpoch(getDatabaseEpoch(_collection)),
_nss(_collection->ns()) {
invariant(_collection);
}
virtual ~RequiresCollectionStageBase() = default;
protected:
void doSaveState() final;
void doRestoreState() final;
/**
* Performs yield preparation specific to a stage which subclasses from RequiresCollectionStage.
*/
virtual void doSaveStateRequiresCollection() = 0;
/**
* Performs yield recovery specific to a stage which subclasses from RequiresCollectionStage.
*/
virtual void doRestoreStateRequiresCollection() = 0;
CollectionT collection() const {
return _collection;
}
UUID uuid() const {
return _collectionUUID;
}
private:
// This can only be called when the plan stage is attached to an operation context. The
// collection pointer 'coll' must be non-null and must point to a valid collection.
uint64_t getDatabaseEpoch(CollectionT coll) const {
invariant(coll);
auto databaseHolder = DatabaseHolder::get(getOpCtx());
auto db = databaseHolder->getDb(getOpCtx(), coll->ns().ns());
invariant(db);
return db->epoch();
}
CollectionT _collection;
const UUID _collectionUUID;
const uint64_t _databaseEpoch;
// TODO SERVER-31695: The namespace will no longer be needed once queries can survive collection
// renames.
const NamespaceString _nss;
};
// Type alias for use by PlanStages that read a Collection.
using RequiresCollectionStage = RequiresCollectionStageBase<const Collection*>;
// Type alias for use by PlanStages that write to a Collection.
using RequiresMutableCollectionStage = RequiresCollectionStageBase<Collection*>;
} // namespace mongo
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