Executing mongodb scripts via mongoid Rails

Question

I have a mongo db script in a js file:

query.js

//conn = new Mongo();
//db = conn.getDB("dbName");
functionFoo = function (arg){
    //----process arg
}

also I have an array of args known as args_array, (that I fetch from database using mongoid) for which I want to do something like this:

args_array.each do |arg|
   //some how call functionFoo(arg) from the query.js file
end

is this possible in rails?

I am able to execute the file from terminal but I want to wrap it in my application so that I can use it from rails console.

Answer 1

I know this old question but in case you still need answer or any one else. This answer works with gem mongo ~> 2.3.

The key to answer you do not need mongoid in this case - in my case I use it for rails model, so I use mongoid (5.1.0) only to get DB connection db = Mongoid.default_client.database - or you can get/create database using mongo gem.

To execute javascript on database you need to call command method db.command({ eval: 'js' }) or db.command({ eval: 'function(n){return db.projects.find({name: n}).toArray();}', args: ['beskhai'], nolock: true })

To get the result you can call .documents db.command(...).documents, The return is a hash {retval: it will be return of you script, ok: is 1 if success} the return object of command call is [Mongo::Operation::Result] https://github.com/mongodb/mongo-ruby-driver/blob/master/lib/mongo/operation/result.rb.

Answer 2

I'm using MongoID 6.0.1, and it easy to query everything you want like that:

    db ||= Mongoid.default_client.database
    f = """
    functionFoo = function (arg){
    //----process arg
    }
    """
    result = db.command({:$eval => f, args: [arg1, arg2, ...arg_n], nolock: true})
    @result_data = result.first['retval']

It not only a function, just every thing you want to do with command. My example is:

db ||= Mongoid.default_client.database
f = """
var collectionNames = db.getCollectionNames(), stats = [];
collectionNames.forEach(function (n) { stats.push(db[n].stats()); });
stats = stats.sort(function(a, b) { return b['size'] - a['size']; });
return stats;
"""
result = db.command({:$eval => f, args: [], nolock: true})
@result_data = result.first['retval']