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. 

Strings children;
        zookeeper_ptr->tryGetChildren(zookeeper_part_uniq_node, children);
        if (!children.empty())
        {
            LOG_TRACE(logger, "Found {} ({}) zookeper locks for {}", zookeeper_part_uniq_node, children.size(), fmt::join(children, ", "));
            part_has_no_more_locks = false;
            continue;
        }
        auto error_code = zookeeper_ptr->tryRemove(zookeeper_part_uniq_node);
        if (error_code == Coordination::Error::ZOK)
        {
            LOG_TRACE(logger, "Removed last parent zookeeper lock {} for part {} with id {}", zookeeper_part_uniq_node, part_name, part_id);
        }
        else if (error_code == Coordination::Error::ZNOTEMPTY)
        {
            LOG_TRACE(logger, "Cannot remove last parent zookeeper lock {} for part {} with id {}, another replica locked part concurrently", zookeeper_part_uniq_node, part_name, part_id);
        }
        else if (error_code == Coordination::Error::ZNONODE)
        {
            LOG_TRACE(logger, "Node with parent zookeeper lock {} for part {} with id {} doesn't exist", zookeeper_part_uniq_node, part_name, part_id);
        }
        else
        {
            throw zkutil::KeeperException(error_code, zookeeper_part_uniq_node);
        }
        
        children.clear();
        String zookeeper_part_node = fs::path(zookeeper_part_uniq_node).parent_path();
        zookeeper_ptr->tryGetChildren(zookeeper_part_node, children);