Iterate tree in mongoDB

Question

I have a dataset like this (for example):

{
    name : "john" ,
    _id : "0"
},
{
    name : "Richard" ,
    parent_id : "0" ,
    _id : "1"
},
{
    name : "Kevin" ,
    parent_id : "0" ,
    _id : "2"
},
{
    name : "William" ,
    parent_id : "1" ,
    _id : "3"
},
{
    name : "George" ,
    parent_id : "3" ,
    _id : "4"
}

I am trying to write a function to receive _idand return all children to any depth of this node, for example, for _id = 0I need something like this:

[
    {
        name : "Richard" ,
        parent_id : "0" ,
        depth : "1" ,
        _id : "1"
    },
    {
        name : "Kevin" ,
        parent_id : "0" ,
        depth : "1" ,
        _id : "2"
    },
    {
        name : "William" ,
        parent_id : "1" ,
        depth : "2" ,
        _id : "3"
    },
    {
        name : "George" ,
        parent_id : "3" ,
        depth : "3" ,
        _id : "4"
    }
]

I am writing several recursive functions to iterate in my mongodb docs, but the main problem is that I cannot handle callbacks (asynchronous) and don’t know when and how I can finish the recursive function.

How can I do this using mongodb and node.js? Any idea could be helpful, thanks.

Answer 1

2 ,
 BFS ( ) DFS ( ).
BFS , DFS, O (logn) DFS, , O (n), , node js, .
BFS, while, while mongo, javascript, BFS , node js php!!!
, while, BFS

function asyncLoop(iterations, func, callback ,foo) {
        var done = false;
        var loop = {
            next: function() {
                if (done) {
                    return;
                }

                if (iterations) {
                    func(loop);

                } else {
                    done = true;
                    if(callback) callback(foo);
                }
            },

            isEnd : function(){
                return done ;
            } ,

            refresh : function(it){
                iterations = it ;
            },

            break: function() {
                done = true;
                callback();
            }
        };
        loop.next();
        return loop;
    }

BFS node js code:

function bfs (_id ,callback){
    _id = String(_id);
    var q = [] ,res = [] ;

    db.tasks.findOne({ _id : _id }).lean().exec(function(err,root){
        root.depth = 0 ;
        q.push(root);

        asyncLoop(q.length ,function(loop){
            res.push(q[0]);
            db.tasks.find({ _parent : q[0]._id }).lean().exec(function(err,new_nodes){
                if(err) console.log(err);
                else {
                    var d = q[0].depth ;
                    q.shift();
                    loop.refresh(new_nodes.length + q.length);
                    if(new_nodes.length > 0){
                        new_nodes.forEach(function(new_node){
                            new_node.depth = d+1 ;
                            q.push(new_node);
                        });
                    }
                    loop.next();
                }
            });

        },function(){ callback(res) });
    });
}

. , , .