And waits for them. That's pointless.
size_t index_,
            const String & src_part_name_,
            const String & new_part_name_,
            const String & checksum_hex_,
            MergeTreeDataFormatVersion format_version)
            : index(index_)
            , src_part_name(src_part_name_)
            , src_part_info(MergeTreePartInfo::fromPartName(src_part_name_, format_version))
            , new_part_name(new_part_name_)
            , new_part_info(MergeTreePartInfo::fromPartName(new_part_name_, format_version))
            , checksum_hex(checksum_hex_)
        {
        }
        size_t index; 
        String src_part_name;
        MergeTreePartInfo src_part_info;
        String new_part_name;
        MergeTreePartInfo new_part_info;
        String checksum_hex;
        
        MutableDataPartPtr res_part;
        
        MergeTreePartInfo found_new_part_info;