Stefan Stefan - 23 days ago 13
Node.js Question

aggregate returns empty array - mongoose

I have the following two simple queries:

Comment.aggregate([{$match: { _id: req.params.id }}])
.exec(function(err, result) {
// result is empty
});

Comment.find({ _id: req.params.id })
.exec(function (err, result) {
// correct result returned
});


My problem is, that the aggregate-Function returns an empty array. Aren't they supposed to return the same result?

Answer

Yes, but you need to cast the id (which is a string) to an objectID :)

let idToSearch = mongoose.Types.ObjectId(req.params.id)
Comment.aggregate([{$match: { _id: idToSearch }}])
.exec(function(err, result) {
    // result is now correct :)
});