Method compileFunctions

src/Interpreters/ExpressionJIT.cpp:497–649

}

void ActionsDAG::compileFunctions(size_t min_count_to_compile_expression, const std::unordered_set<const ActionsDAG::Node *> & lazy_executed_nodes)
{
    struct Data
    {
        bool is_compilable_in_isolation = false;
        bool all_parents_compilable = true;
        size_t compilable_children_size = 0;
        size_t children_size = 0;
    };

    std::unordered_map<const Node *, Data> node_to_data;

    /// Check which nodes can be compiled in isolation

    for (const auto & node : nodes)
    {
        bool node_is_compilable_in_isolation = isCompilableFunction(node, lazy_executed_nodes) && !isCompilableConstant(node);
        node_to_data[&node].is_compilable_in_isolation = node_is_compilable_in_isolation;
    }

    struct Frame
    {
        const Node * node;
        size_t next_child_to_visit = 0;
    };

    std::stack<Frame> stack;
    std::unordered_set<const Node *> visited_nodes;

    /** Algorithm is to iterate over each node in ActionsDAG, and update node compilable_children_size.
      * After this procedure data for each node is initialized.
      */

    for (auto & node : nodes)
    {
        if (visited_nodes.contains(&node))
            continue;

        stack.emplace(Frame{.node = &node});

        while (!stack.empty())
        {
            auto & current_frame = stack.top();
            auto & current_node = current_frame.node;

            while (current_frame.next_child_to_visit < current_node->children.size())
            {
                const auto & child = current_node->children[current_frame.next_child_to_visit];

                if (visited_nodes.contains(child))
                {
                    ++current_frame.next_child_to_visit;
                    continue;
                }

                stack.emplace(Frame{.node=child});
                break;
            }