If they are defined, they can override table-level settings.
{
    return std::chrono::duration_cast<std::chrono::microseconds>(timepoint.time_since_epoch()).count();
}
inline UInt64 time_in_seconds(std::chrono::time_point<std::chrono::system_clock> timepoint)
{
    return std::chrono::duration_cast<std::chrono::seconds>(timepoint.time_since_epoch()).count();
}
MergeTreeData::MergeTreeData(