Method prepare

src/Processors/Transforms/IntersectOrExceptTransform.cpp:24–75

IntersectOrExceptTransform::Status IntersectOrExceptTransform::prepare()
{
    auto & output = outputs.front();

    if (output.isFinished())
    {
        for (auto & in : inputs)
            in.close();

        return Status::Finished;
    }

    if (!output.canPush())
    {
        for (auto & input : inputs)
            input.setNotNeeded();

        return Status::PortFull;
    }

    if (current_output_chunk)
    {
        output.push(std::move(current_output_chunk));
    }

    if (finished_second_input)
    {
        if (inputs.front().isFinished())
        {
            output.finish();
            return Status::Finished;
        }
    }
    else if (inputs.back().isFinished())
    {
        finished_second_input = true;
    }

    if (!has_input)
    {
        InputPort & input = finished_second_input ? inputs.front() : inputs.back();

        input.setNeeded();
        if (!input.hasData())
            return Status::NeedData;

        current_input_chunk = input.pull();
        has_input = true;
    }

    return Status::Ready;
}


void IntersectOrExceptTransform::work()