Found in stress test: https://gist.github.com/alesapin/5cd6b8901488a1f170d5ef389900a534
Report: https://s3.amazonaws.com/clickhouse-test-reports/31158/7fb9a42b119b6c3eba1784caaabde51c1ded3384/stress_tests__debug__actions_.html
if (all_inputs_finished)
    {
        
        while (!chunks_map.empty())
            if (try_push_by_iter(chunks_map.begin()))
                return true;
    }
    else
    {
        for (; next_bucket_to_push < current_bucket; ++next_bucket_to_push)
            if (try_push_by_iter(chunks_map.find(next_bucket_to_push)))
                return true;
    }
    return false;
}
bool GroupingAggregatedTransform::tryPushSingleLevelData()
{
    if (single_level_chunks.empty())
        return false;
    pushData(std::move(single_level_chunks), -1, false);
    return true;
}
bool GroupingAggregatedTransform::tryPushOverflowData()
{
    if (overflow_chunks.empty())
        return false;
    pushData(std::move(overflow_chunks), -1, true);
    return true;
}
IProcessor::Status GroupingAggregatedTransform::prepare()