Method prepare

src/Processors/Transforms/ExplainAnalyzeTransform.cpp:135–195

}

ISimpleTransform::Status ExplainAnalyzeTransform::prepare()
{
    /// Check can output.

    if (output.isFinished())
    {
        input.close();
        return Status::Finished;
    }

    if (!output.canPush())
    {
        input.setNotNeeded();
        return Status::PortFull;
    }

    /// Output if has data.
    if (has_output)
    {
        output.pushData(std::move(output_data));
        has_output = false;

        if (!no_more_data_needed)
            return Status::PortFull;
    }

    /// Stop if don't need more data.
    if (no_more_data_needed)
    {
        input.close();
        output.finish();
        return Status::Finished;
    }

    /// Check can input.
    if (!has_input)
    {
        if (input.isFinished())
        {
            if (has_final_transform)
                return Status::Ready;
            output.finish();
            return Status::Finished;
        }

        input.setNeeded();

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

        input_data = input.pullData(set_input_not_needed_after_read);
        has_input = true;

        if (input_data.exception)
            /// No more data needed. Exception will be thrown (or swallowed) later.
            input.setNotNeeded();
    }