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
```
{
        for (auto counter : counter_list)
        {
            arena.free(counter->key);
            delete counter;
        }
        counter_map.clear();
        counter_list.clear();
        alpha_map.clear();
    }
    void destroyLastElement()
    {
        auto last_element = counter_list.back();
        arena.free(last_element->key);
        delete last_element;
        counter_list.pop_back();
        ++removed_keys;
        if (removed_keys * 2 > counter_map.size())
            rebuildCounterMap();
    }
    Counter * findCounter(const TKey & key, size_t hash)