Method cloneInplace

src/Processors/QueryPlan/QueryPlan.cpp:1102–1139

}

void QueryPlan::cloneInplace(Node * node_to_replace, Node * subplan_root)
{
    if (!subplan_root)
        throw Exception(ErrorCodes::LOGICAL_ERROR, "Cannot clone subplan in place because subplan root is null");

    struct Frame
    {
        Node * node;
        Node * clone;
        std::vector<Node *> children = {};
    };

    std::vector<Frame> nodes_to_process{ Frame{ .node = subplan_root, .clone = node_to_replace } };

    while (!nodes_to_process.empty())
    {
        auto & frame = nodes_to_process.back();
        if (frame.children.size() == frame.node->children.size())
        {
            frame.clone->step = frame.node->step->clone();
            frame.clone->children = std::move(frame.children);
            nodes_to_process.pop_back();
        }
        else
        {
            size_t next_child = frame.children.size();
            auto * child = frame.node->children[next_child];

            nodes.emplace_back(Node{ .step = {} });
            nodes.back().children.reserve(child->children.size());
            auto * child_clone = &nodes.back();

            frame.children.push_back(child_clone);

            nodes_to_process.push_back(Frame{ .node = child, .clone = child_clone });
        }
    }
}

QueryPlan QueryPlan::clone() const
{