wiredtiger_snapshot_manager.h

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#pragma once

#include <boost/optional.hpp>
#include <wiredtiger.h>

#include "mongo/base/disallow_copying.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/stdx/mutex.h"

namespace mongo {

class WiredTigerOplogManager;

class WiredTigerSnapshotManager final : public SnapshotManager {
    MONGO_DISALLOW_COPYING(WiredTigerSnapshotManager);

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
    //

    Timestamp beginTransactionOnCommittedSnapshot(WT_SESSION* session) const;

    Timestamp beginTransactionOnLocalSnapshot(
        WT_SESSION* session, WiredTigerBeginTxnBlock::IgnorePrepared ignorePrepared) const;

    boost::optional<Timestamp> getMinSnapshotForNextCommittedRead() const;

private:
    // Snapshot to use for reads at a commit timestamp.
    mutable stdx::mutex _committedSnapshotMutex;  // Guards _committedSnapshot.
    boost::optional<Timestamp> _committedSnapshot;

    // Snapshot to use for reads at a local stable timestamp.
    mutable stdx::mutex _localSnapshotMutex;  // Guards _localSnapshot.
    boost::optional<Timestamp> _localSnapshot;
};
}