Ordinary database engine is deprecated but there is no simple mean to change database engine to Atomic for existing databases.

Possible options:
- ALTER DATABASE MODIFY ENGINE query.
- Flag that triggers migration at ClickHouse startup.

The latter should be easier to implement. 

String part_id, const String & table_uuid, const String & part_name,
        const String & replica_name_, std::string disk_type, zkutil::ZooKeeperPtr zookeeper_ptr, const MergeTreeSettings & settings,
        Poco::Logger * logger, const String & zookeeper_path_old)
{
    boost::replace_all(part_id, "/", "_");
    Strings zc_zookeeper_paths = getZeroCopyPartPath(settings, disk_type, table_uuid, part_name, zookeeper_path_old);
    bool part_has_no_more_locks = true;
    NameSet files_not_to_remove;
    for (const auto & zc_zookeeper_path : zc_zookeeper_paths)
    {
        String files_not_to_remove_str;
        zookeeper_ptr->tryGet(zc_zookeeper_path, files_not_to_remove_str);
        files_not_to_remove.clear();
        if (!files_not_to_remove_str.empty())
            boost::split(files_not_to_remove, files_not_to_remove_str, boost::is_any_of("\n "));
        String zookeeper_part_uniq_node = fs::path(zc_zookeeper_path) / part_id;
        
        String zookeeper_part_replica_node = fs::path(zookeeper_part_uniq_node) / replica_name_;
        LOG_TRACE(logger, "Remove zookeeper lock {} for part {}", zookeeper_part_replica_node, part_name);
        if (auto ec = zookeeper_ptr->tryRemove(zookeeper_part_replica_node); ec != Coordination::Error::ZOK && ec != Coordination::Error::ZNONODE)
        {
            throw zkutil::KeeperException(ec, zookeeper_part_replica_node);
        }