How to execute a stored function from mongodb-native/node.js

Question

I'm trying to execute a stored function from mongodb-native/node.js environment.

I have several functions inside db.system.js.

It seems Db.executeCommand() is the function but I have no idea how can I pass the function name and the arguments.

I tried db.eval() as suggested but I got the following.

> db.eval('getValue()', {}, function(er,doc) {console.log(er);console.log(doc);});
{ stack: [Getter/Setter], arguments: [ 'send', undefined ], type: 'non_object_property_call', message: [Getter/Setter] }
null

getValue is a simple function that returns an integer.

Anyone has an idea? Thanks.

cjohn · Accepted Answer · 2011-08-26 14:43:34Z

4

Assuming db is your open database handler:

db.eval("myFunction(param, param_n)", function(error, result) { });

Looks like you can pass the parameters in separately, too. https://github.com/christkv/node-mongodb-native/blob/master/lib/mongodb/db.js

answered Aug 26, 2011 at 14:43

cjohn

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3 Comments

MinJae Hwang Over a year ago

could you give me an example? i am still having a problem with db.eval()

cjohn Over a year ago

@MinJaeHwang: If I use something like db.system.js.save({_id:"addNumbers", value:function(x, y){ return x + y; }}); to get the stored procedure addNumbers into my database from the js command line, the node.js command: db.eval("addNumbers(4, 5)", function(error, result) { console.log(result); }); will output 9 to the console. Does that help?

MinJae Hwang Over a year ago

It just returns null. db.eval('addNumbers(4,5)'); at mongo shell returns 9, though.

Gautam · Accepted Answer · 2017-05-09 09:35:41Z

There you go:

function testDB(req,res) {
        MongoClient.connect(url, function(err, db) {
            if (err) {
                console.log(err);
                res.send('connection failed');
            } else {
               db.eval("testFunction()", function(err, output) {
                    if(err){
                        console.log("ERROR: "+err);
                        res.send(err);
                        return;
                    }else{
                        res.send(output);
                        return; 
                    }
                });
                db.close();
            }
        });
    }

I am assuming that you call it for a rest API. You can change the function params based on your need. Also I assume your URL has enough permissions to call the function. If not, use a mongo tool like RoboMongo and change the permission to the user.

Omkar Dusane · Accepted Answer · 2016-04-19 15:37:39Z

0

It's because you are thinking it will return value , This is asynchronous call , you must pass a callback function with (err,doc) to get the return value

db.eval('addNumbers(4,5)',function(er,doc){
   console.log(doc);
})

answered Apr 19, 2016 at 15:37

Omkar Dusane

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