Method explainPlan

src/Processors/QueryPlan/QueryPlan.cpp:332–389

}

JSONBuilder::ItemPtr QueryPlan::explainPlan(const ExplainPlanOptions & options) const
{
    checkInitialized();

    struct Frame
    {
        Node * node = {};
        size_t next_child = 0;
        std::unique_ptr<JSONBuilder::JSONMap> node_map = {};
        std::unique_ptr<JSONBuilder::JSONArray> children_array = {};
    };

    std::stack<Frame> stack;
    stack.push(Frame{.node = root});

    std::unique_ptr<JSONBuilder::JSONMap> tree;

    while (!stack.empty())
    {
        auto & frame = stack.top();

        if (frame.next_child == 0)
        {
            if (!frame.node->children.empty())
                frame.children_array = std::make_unique<JSONBuilder::JSONArray>();

            frame.node_map = std::make_unique<JSONBuilder::JSONMap>();
            explainStep(*frame.node->step, *frame.node_map, options);
        }

        if (frame.next_child < frame.node->children.size())
        {
            stack.push(Frame{frame.node->children[frame.next_child]});
            ++frame.next_child;
        }
        else
        {
            auto child_plans = frame.node->step->getChildPlans();

            if (!frame.children_array && !child_plans.empty())
                frame.children_array = std::make_unique<JSONBuilder::JSONArray>();

            for (const auto & child_plan : child_plans)
                frame.children_array->add(child_plan->explainPlan(options));

            if (frame.children_array)
                frame.node_map->add("Plans", std::move(frame.children_array));

            tree.swap(frame.node_map);
            stack.pop();

            if (!stack.empty())
                stack.top().children_array->add(std::move(tree));
        }
    }

    return tree;
}