How to search in sub doc - node.js

Question

I have an angular-fullstack app generated from angular-fullstack yeoman generator and I have a Query Model as follows:
'use strict';
var mongoose = require('mongoose'),
Schema = mongoose.Schema;
/**
* Discussion Question Schema
*/
var QuerySchema = new Schema({
date: {
type: Date,
default: Date
},
tags: [{
type: Schema.ObjectId,
ref: 'Tag'
}]
});
module.exports = mongoose.model('Query', QuerySchema);
var deepPopulate = require('mongoose-deep-populate')(mongoose);
and Tag has a field text. Now in my query controller I have to deep populate some other fields and paginate them so, I am trying something like this in the controller function:
exports.index = function(req, res) {
var escapeRegExpChars = function (text) {
return text.replace(/[-[\]{}()*+?.,\\^$|#\s]/g, "\\$&");
};
require('paginate-for-mongoose');
var limit,page;
if(req.query.limit != undefined) limit = req.query.limit;
else limit = 10;
if(req.query.page != undefined) page = req.query.page;
else page = 1;
var queryObj = {};
if(req.query.searchText != undefined && req.query.searchText != '')
queryObj['title']= new RegExp(escapeRegExpChars(req.query.searchText), 'i');
var options = {
perPage:limit,
delta:2,
page:page
};
if(req.query.fold !=undefined && req.query.fold != '') queryObj["tags.text"] = req.query.fold;
var query = Query.find(queryObj).populate('tags','text').deepPopulate('user class user.class');
query.paginate(options,function(err, resp){
if(err) { return handleError(res, err); }
if(req.query.fold) console.log(resp.results);
return res.status(200).json(resp.results);
});
};
How do I search queries with tags.text value exactly as the req.query.fold value?

Answer 1

MongoDB doesn't support joins so to search on a linked doc you have to do it in two steps:
// First look up the _id of the tag
Tags.findOne({text: req.query.fold}, function(err, tag) {
if (tag) {
// Add a match in the doc's tags array to the tag's _id
queryObj.tags = tag._id;
var query = Query.find(queryObj)...
...
}
});