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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 <boost/optional.hpp>
#include <wiredtiger.h>
#include "mongo/bson/timestamp.h"
#include "mongo/db/storage/snapshot_manager.h"
#include "mongo/db/storage/wiredtiger/wiredtiger_begin_transaction_block.h"
#include "mongo/platform/mutex.h"
namespace mongo {
using RoundUpPreparedTimestamps = WiredTigerBeginTxnBlock::RoundUpPreparedTimestamps;
class WiredTigerOplogManager;
class WiredTigerSnapshotManager final : public SnapshotManager {
WiredTigerSnapshotManager(const WiredTigerSnapshotManager&) = delete;
WiredTigerSnapshotManager& operator=(const WiredTigerSnapshotManager&) = delete;
public:
WiredTigerSnapshotManager() = default;
void setCommittedSnapshot(const Timestamp& timestamp) final;
void setLocalSnapshot(const Timestamp& timestamp) final;
boost::optional<Timestamp> getLocalSnapshot() final;
void dropAllSnapshots() final;
//
// WT-specific methods
//
/**
* Starts a transaction and returns the SnapshotName used.
*
* Throws if there is currently no committed snapshot.
*/
Timestamp beginTransactionOnCommittedSnapshot(
WT_SESSION* session,
PrepareConflictBehavior prepareConflictBehavior,
RoundUpPreparedTimestamps roundUpPreparedTimestamps) const;
/**
* Starts a transaction on the last stable local timestamp, set by setLocalSnapshot.
*
* Throws if no local snapshot has been set.
*/
Timestamp beginTransactionOnLocalSnapshot(
WT_SESSION* session,
PrepareConflictBehavior prepareConflictBehavior,
RoundUpPreparedTimestamps roundUpPreparedTimestamps) const;
/**
* Returns lowest SnapshotName that could possibly be used by a future call to
* beginTransactionOnCommittedSnapshot, or boost::none if there is currently no committed
* snapshot.
*
* This should not be used for starting a transaction on this SnapshotName since the named
* snapshot may be deleted by the time you start the transaction.
*/
boost::optional<Timestamp> getMinSnapshotForNextCommittedRead() const;
private:
// Snapshot to use for reads at a commit timestamp.
mutable Mutex _committedSnapshotMutex = // Guards _committedSnapshot.
MONGO_MAKE_LATCH("WiredTigerSnapshotManager::_committedSnapshotMutex");
boost::optional<Timestamp> _committedSnapshot;
// Snapshot to use for reads at a local stable timestamp.
mutable Mutex _localSnapshotMutex = // Guards _localSnapshot.
MONGO_MAKE_LATCH("WiredTigerSnapshotManager::_localSnapshotMutex");
boost::optional<Timestamp> _localSnapshot;
};
} // namespace mongo
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