https://clickhouse-test-reports.s3.yandex.net/17375/99073c26ee2692f8efe2ab14b2d8ae0fd813b80e/fuzzer/fuzzer.log

```
SELECT
    k,
    topK(v)
FROM 
(
    SELECT
        number % 7 AS k,
        arrayMap(x -> arrayMap(x -> if(x = 0, NULL, toString(x)), range(x)), range(intDiv(number, 1))) AS v
    FROM system.numbers
    LIMIT 257
)
GROUP BY k
ORDER BY k ASC
```
{
        std::vector<Counter> res;
        for (auto counter : counter_list)
        {
            res.push_back(*counter);
            if (res.size() == k)
                break;
        }
        return res;
    }
    void write(WriteBuffer & wb) const
    {
        writeVarUInt(size(), wb);
        for (auto counter : counter_list)
            counter->write(wb);
        writeVarUInt(alpha_map.size(), wb);
        for (auto alpha : alpha_map)
            writeVarUInt(alpha, wb);
    }
    void read(ReadBuffer & rb)