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
```
{
    public:
        Reader(DB::ReadBuffer & in_)
            : in(in_)
        {
        }
        Reader(const Reader &) = delete;
        Reader & operator=(const Reader &) = delete;
        bool next()
        {
            if (!is_initialized)
            {
                Cell::State::read(in);
                DB::readVarUInt(size, in);
                is_initialized = true;
            }
            if (read_count == size)
            {
                is_eof = true;
                return false;
            }
            cell.read(in);
            ++read_count;
            return true;
        }
        inline const value_type & get() const