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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/base/string_data.h"
#include "mongo/db/catalog/collection.h"
#include "mongo/db/catalog/database.h"
#include "mongo/db/concurrency/d_concurrency.h"
#include "mongo/db/namespace_string.h"
#include "mongo/db/operation_context.h"
#include "mongo/db/views/view.h"
namespace mongo {
/**
* RAII-style class, which acquires a lock on the specified database in the requested mode and
* obtains a reference to the database. Used as a shortcut for calls to
* DatabaseHolder::get(opCtx)->get().
*
* Use this when you want to do a database-level operation, like read a list of all collections, or
* drop a collection.
*
* It is guaranteed that the lock will be released when this object goes out of scope, therefore
* the database reference returned by this class should not be retained.
*/
class AutoGetDb {
AutoGetDb(const AutoGetDb&) = delete;
AutoGetDb& operator=(const AutoGetDb&) = delete;
public:
AutoGetDb(OperationContext* opCtx,
StringData dbName,
LockMode mode,
Date_t deadline = Date_t::max());
/**
* Returns nullptr if the database didn't exist.
*/
Database* getDb() const {
return _db;
}
private:
const Lock::DBLock _dbLock;
Database* const _db;
};
/**
* RAII-style class, which acquires global, database, and collection locks according to the chart
* below.
*
* | modeColl | Global Lock Result | DB Lock Result | Collection Lock Result |
* |----------+--------------------+----------------+------------------------|
* | MODE_IX | MODE_IX | MODE_IX | MODE_IX |
* | MODE_X | MODE_IX | MODE_IX | MODE_X |
* | MODE_IS | MODE_IS | MODE_IS | MODE_IS |
* | MODE_S | MODE_IS | MODE_IS | MODE_S |
*
* NOTE: Throws NamespaceNotFound if the collection UUID cannot be resolved to a name.
*
* Any acquired locks may be released when this object goes out of scope, therefore the database
* and the collection references returned by this class should not be retained.
*/
class AutoGetCollection {
AutoGetCollection(const AutoGetCollection&) = delete;
AutoGetCollection& operator=(const AutoGetCollection&) = delete;
public:
enum ViewMode { kViewsPermitted, kViewsForbidden };
AutoGetCollection(OperationContext* opCtx,
const NamespaceStringOrUUID& nsOrUUID,
LockMode modeColl,
ViewMode viewMode = kViewsForbidden,
Date_t deadline = Date_t::max());
/**
* Returns nullptr if the database didn't exist.
*/
Database* getDb() const {
return _autoDb.getDb();
}
/**
* Returns nullptr if the collection didn't exist.
*/
Collection* getCollection() const {
return _coll;
}
/**
* Returns nullptr if the view didn't exist.
*/
ViewDefinition* getView() const {
return _view.get();
}
/**
* Returns the resolved namespace of the collection or view.
*/
const NamespaceString& getNss() const {
return _resolvedNss;
}
private:
AutoGetDb _autoDb;
// If the object was instantiated with a UUID, contains the resolved namespace, otherwise it is
// the same as the input namespace string
NamespaceString _resolvedNss;
// This field is boost::optional, because in the case of lookup by UUID, the collection lock
// might need to be relocked for the correct namespace
boost::optional<Lock::CollectionLock> _collLock;
Collection* _coll = nullptr;
std::shared_ptr<ViewDefinition> _view;
};
/**
* RAII-style class, which acquires a lock on the specified database in the requested mode and
* obtains a reference to the database, creating it was non-existing. Used as a shortcut for
* calls to DatabaseHolder::get(opCtx)->openDb(), taking care of locking details. The
* requested mode must be MODE_IX or MODE_X.
*
* Use this when you are about to perform a write, and want to create the database if it doesn't
* already exist.
*
* It is guaranteed that locks will be released when this object goes out of scope, therefore
* the database reference returned by this class should not be retained.
*/
class AutoGetOrCreateDb {
AutoGetOrCreateDb(const AutoGetOrCreateDb&) = delete;
AutoGetOrCreateDb& operator=(const AutoGetOrCreateDb&) = delete;
public:
AutoGetOrCreateDb(OperationContext* opCtx,
StringData dbName,
LockMode mode,
Date_t deadline = Date_t::max());
Database* getDb() const {
return _db;
}
bool justCreated() const {
return _justCreated;
}
private:
AutoGetDb _autoDb;
Database* _db;
bool _justCreated{false};
};
/**
* RAII-style class. Hides changes to the CollectionCatalog for the life of the object, so that
* calls to CollectionCatalog::lookupNSSByUUID will return results as before the RAII object was
* instantiated.
*
* The caller must hold the global exclusive lock for the life of the instance.
*/
class ConcealCollectionCatalogChangesBlock {
ConcealCollectionCatalogChangesBlock(const ConcealCollectionCatalogChangesBlock&) = delete;
ConcealCollectionCatalogChangesBlock& operator=(const ConcealCollectionCatalogChangesBlock&) =
delete;
public:
/**
* Conceals future CollectionCatalog changes and stashes a pointer to the opCtx for the
* destructor to use.
*/
ConcealCollectionCatalogChangesBlock(OperationContext* opCtx);
/**
* Reveals CollectionCatalog changes.
*/
~ConcealCollectionCatalogChangesBlock();
private:
// Needed for the destructor to access the CollectionCatalog in order to call onOpenCatalog.
OperationContext* _opCtx;
};
/**
* RAII type to set and restore the timestamp read source on the recovery unit.
*
* Snapshot is abandoned in constructor and destructor, so it can only be used before
* the recovery unit becomes active or when the existing snapshot is no longer needed.
*/
class ReadSourceScope {
public:
ReadSourceScope(OperationContext* opCtx,
RecoveryUnit::ReadSource readSource = RecoveryUnit::ReadSource::kUnset,
boost::optional<Timestamp> provided = boost::none);
~ReadSourceScope();
private:
OperationContext* _opCtx;
RecoveryUnit::ReadSource _originalReadSource;
Timestamp _originalReadTimestamp;
};
} // namespace mongo
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