Mongodb concat int and string

Question

I\'m trying to project FileName and FileSize for all my files in my collection with a size of 50 mb and greater, but I cannot concat a the type FileSize as it has a type of

Answer 1

It is possible now in MongoDB v4.0 using $toString operator which converts a value to a string:

db.col.aggregate([
    {
        $project: {
            FileSize: { $concat: [ { $toString: "$FileSize" }, " MB" ] }
        }
    }
])