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
```
{
        destroyElements();
        size_t count = 0;
        readVarUInt(count, rb);
        for (size_t i = 0; i < count; ++i)
        {
            auto counter = new Counter();
            counter->read(rb);
            counter->hash = counter_map.hash(counter->key);
            push(counter);
        }
        readAlphaMap(rb);
    }
    void readAlphaMap(ReadBuffer & rb)
    {
        size_t alpha_size = 0;
        readVarUInt(alpha_size, rb);
        for (size_t i = 0; i < alpha_size; ++i)
        {
            UInt64 alpha = 0;
            readVarUInt(alpha, rb);
            alpha_map.push_back(alpha);
        }
    }
protected:
    void push(Counter * counter)