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
{
    
    auto & output = outputs.front();
    if (output.isFinished())
    {
        for (auto & input : inputs)
            input.close();
        chunks_map.clear();
        last_bucket_number.clear();
        return Status::Finished;
    }
    
    if (!read_from_all_inputs)
    {
        readFromAllInputs();
        if (!read_from_all_inputs)
            return Status::NeedData;
    }
    
    if (has_two_level && !single_level_chunks.empty())
        return Status::Ready;
    
    if (!output.canPush())
    {
        for (auto & input : inputs)
            input.setNotNeeded();
        return Status::PortFull;
    }
    bool pushed_to_output = false;