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. 

if (!deserialize_states.contains(name))
    {
        settings.getter = create_stream_getter(true);
        serialization->deserializeBinaryBulkStatePrefix(settings, deserialize_states[name]);
    }
    settings.getter = create_stream_getter(false);
    serialization->deserializeBinaryBulkWithMultipleStreams(column, max_rows_to_read, settings, deserialize_states[name], &cache);
}
bool LogSource::isFinished()
{
    if (is_finished)
        return true;
    
    if (rows_read == rows_limit)
    {
        is_finished = true;
        return true;
    }
    if (limited_by_file_sizes)
    {
        
        if (!streams.empty() && streams.begin()->second.compressed->eof())
        {
            is_finished = true;
            return true;
        }
    }
    return false;
}
class LogSink final : public SinkToStorage