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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/collection_catalog.h"
#include "mongo/db/exec/plan_stage.h"
#include "mongo/util/uuid.h"
namespace mongo {
/**
* A 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.
*/
class RequiresCollectionStage : public PlanStage {
public:
RequiresCollectionStage(const char* stageType,
ExpressionContext* expCtx,
const CollectionPtr& coll)
: PlanStage(stageType, expCtx),
_collection(&coll),
_collectionUUID(coll->uuid()),
_catalogEpoch(getCatalogEpoch()),
_nss(coll->ns()) {}
virtual ~RequiresCollectionStage() = default;
protected:
void doSaveState() final;
void doRestoreState(const RestoreContext& context) 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;
const CollectionPtr& 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.
uint64_t getCatalogEpoch() const {
return CollectionCatalog::get(opCtx())->getEpoch();
}
// Pointer to a CollectionPtr that is stored at a high level in a AutoGetCollection or other
// helper. It needs to stay valid until the PlanExecutor saves its state. To avoid this pointer
// from dangling it needs to be reset when doRestoreState() is called and it is reset to a
// different CollectionPtr.
const CollectionPtr* _collection;
const UUID _collectionUUID;
const uint64_t _catalogEpoch;
// 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 write to a Collection.
using RequiresMutableCollectionStage = RequiresCollectionStage;
} // namespace mongo
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