Statistics
https://play.clickhouse.com/play?user=play#c2VsZWN0IAp0b1N0YXJ0T2ZIb3VyKGNoZWNrX3N0YXJ0X3RpbWUpIGFzIGQsCmNvdW50KCksICBncm91cFVuaXFBcnJheShwdWxsX3JlcXVlc3RfbnVtYmVyKSwgIGFueShyZXBvcnRfdXJsKQpmcm9tIGNoZWNrcyB3aGVyZSAnMjAyMi0wNi0wMScgPD0gY2hlY2tfc3RhcnRfdGltZSBhbmQgdGVzdF9uYW1lIGxpa2UgJyUwMjQ5MV9wYXJ0X2xvZ19oYXNfdGFibGVfdXVpZCUnIGFuZCB0ZXN0X3N0YXR1cyBpbiAoJ0ZBSUwnLCAnRkxBS1knKSBncm91cCBieSBkIG9yZGVyIGJ5IGQgZGVzYw==

Some times there are not output from requests.
std::vector<std::vector<std::pair<String, DiskPtr>>> threads_parts(num_threads);
    std::set<size_t> remaining_thread_parts;
    std::queue<size_t> threads_queue;
    for (size_t i = 0; i < num_threads; ++i)
    {
        remaining_thread_parts.insert(i);
        threads_queue.push(i);
    }
    while (!parts_queue.empty())
    {
        assert(!threads_queue.empty());
        size_t i = threads_queue.front();
        auto & need_parts = parts_per_thread[i];
        assert(need_parts > 0);
        auto & thread_parts = threads_parts[i];
        auto & current_parts = parts_queue.front();
        assert(!current_parts.empty());
        auto parts_to_grab = std::min(need_parts, current_parts.size());
        thread_parts.insert(thread_parts.end(), current_parts.end() - parts_to_grab, current_parts.end());
        current_parts.resize(current_parts.size() - parts_to_grab);
        need_parts -= parts_to_grab;
        
        
        
        
        if (!current_parts.empty())
            parts_queue.push(std::move(current_parts));
        parts_queue.pop();
        
        if (need_parts > 0)