**How to reproduce**
Clickhouse server 20.13.1.5273
```
CREATE TABLE default.test
(
`key` UInt32,
`ts` DateTime CODEC(DoubleDelta, LZ4),
`db_time` DateTime DEFAULT now() COMMENT 'spout-ignore' CODEC(DoubleDelta, LZ4)
)
ENGINE = MergeTree
PARTITION BY toStartOfTenMinutes(db_time)
ORDER BY (key, ts)
TTL db_time + toIntervalHour(3)
SETTINGS index_granularity = 8192, merge_with_ttl_timeout = 3600, min_rows_for_compact_part = 1000000, min_bytes_for_compact_part = 200000000, in_memory_parts_enable_wal = 0;


INSERT INTO test(key, ts) SELECT number % 1000, now() + intDiv(number,1000) FROM numbers(500);

SELECT * FROM test;
500 rows in set. Elapsed: 0.003 sec.

DETACH TABLE test;

ATTACH TABLE test;

SELECT * FROM test;

0 rows in set. Elapsed: 0.002 sec.
```

**Expected behavior**
Clickhouse would flush parts on disk.
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)
            threads_queue.push(i);
        threads_queue.pop();