And waits for them. That's pointless.
PartDescriptions final_parts;
    Strings final_part_names;
    {
        final_part_names = adding_parts_active_set.getParts();
        for (const String & final_part_name : final_part_names)
        {
            auto part_desc = part_name_to_desc[final_part_name];
            if (!part_desc)
                throw Exception("There is no final part " + final_part_name + ". This is a bug", ErrorCodes::LOGICAL_ERROR);
            final_parts.emplace_back(part_desc);
            if (final_parts.size() > 1)
            {
                auto & prev = *final_parts[final_parts.size() - 2];
                auto & curr = *final_parts[final_parts.size() - 1];
                if (!prev.found_new_part_info.isDisjoint(curr.found_new_part_info))
                {
                    throw Exception("Intersected final parts detected: " + prev.found_new_part_name
                        + " and " + curr.found_new_part_name + ". It should be investigated.", ErrorCodes::LOGICAL_ERROR);
                }
            }
        }
    }
    static const String TMP_PREFIX = "tmp_replace_from_";
    auto obtain_part = [&] (PartDescriptionPtr & part_desc)
    {
        if (part_desc->src_table_part)
        {
            if (part_desc->checksum_hex != part_desc->src_table_part->checksums.getTotalChecksumHex())
                throw Exception("Checksums of " + part_desc->src_table_part->name + " is suddenly changed", ErrorCodes::UNFINISHED);
            part_desc->res_part = cloneAndLoadDataPartOnSameDisk(