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
```
{
        auto it = counter_map.find(key, hash);
        if (!it)
            return nullptr;
        return it->getMapped();
    }
    void rebuildCounterMap()
    {
        removed_keys = 0;
        counter_map.clear();
        for (auto counter : counter_list)
            counter_map[counter->key] = counter;
    }
    using CounterMap = HashMapWithStackMemory<TKey, Counter *, Hash, 4>;
    CounterMap counter_map;
    std::vector<Counter *> counter_list;
    std::vector<UInt64> alpha_map;
    SpaceSavingArena<TKey> arena;
    size_t m_capacity;
    size_t removed_keys = 0;
};
}