Server Side Sorting using Mongoose (mongodb + node.js)

Question

I am trying to sort based on a function. I am currently doing the following, and it works.

var _criteria = ... some search criteria
var _pageNumber = ... the page num I want to see
var _nPerPage = ... the number of documents per page
var _sort = {};
_sort.name = ... the column name I am sorting on
_sort.order = ... asc or desc sort

Collection.find(_criteria)
    .skip((_pageNumber-1)*_nPerPage)
    .limit(_nPerPage)
    .sort(_sort.name,_sort.order)
    .execFind(function (err, docs) {
...
});

Now I would like to sort based on some function that takes in a user input:

var sortFunc = function(x){ return (x - doc.score); }; 
// where doc.score is an attribute of the document I am searching on
//   and x is a user provided value

and I can't find a way to do this. I tried to eval this function as follows:

var mongoose = require('mongoose');
var mdb = mongoose.connect(uri);
var myfunc = function(x){ return x; };
mdb.connection.db.eval( myfunc, "asdf", function (err, retval) {
    console.log('err: '+err);
    console.log('retval: '+retval);
});

but I get the following error:

err: Error: eval failed: db assertion failure
retval: null

Any help on this would be awesome. Thanks a lot

Answer 1

I think you need do like this:

var mongoose = require('mongoose');
mongoose.connect(uri);
mongoose.connection.on("open", function(err){
  mongoose.connection.db.eval("function(x){ return x; }", "asdf", function (err, retval) {
      console.log('err: '+err);
      console.log('retval: '+retval);
  });
});

This can work on my PC. You must ensure that the connection is available.