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. 

{
    checkTableCanBeRenamed(new_table_id);
    MergeTreeData::rename(new_path_to_table_data, new_table_id);
    
    if (!is_readonly)
    {
        
        
        try
        {
            auto zookeeper = getZooKeeper();
            zookeeper->set(fs::path(replica_path) / "host", getReplicatedMergeTreeAddress().toString());
        }
        catch (Coordination::Exception & e)
        {
            LOG_WARNING(log, "Cannot update the value of 'host' node (replica address) in ZooKeeper: {}", e.displayText());
        }
    }
    
}
bool StorageReplicatedMergeTree::existsNodeCached(const std::string & path) const