Moongoose sort by parseFloat(String)? - node.js

Question

I want to sort my query result by the Float value. But the value stored in MongoDB is type String, Can I parse the String to Float and sort it dynamically? Just like complex sort.
The following are parts of my schema and sort code:
Schema:
var ScenicSpotSchema = new Schema({
...
detail_info: {
...
overall_rating: String,
...
},
});
Sort function:
ScenicSpot.find({'name': new RegExp(req.query.keyword)}, )
.sort('-detail_info.overall_rating')
.skip(pageSize * pageNumber)
.limit(pageSize)
.exec(function (err, scenicSpots) {
if (err) {
callback(err);
} else {
callback(null, scenicSpots);
}
});
Any kind of help and advice is appreciated. :)

Answer 1

.sort mongoose do not support converting data type. see: http://mongoosejs.com/docs/api.html#query_Query-sort
It only accept column names and order.
There are two path to acheive your goal:
use mapreduce in mongo, first convert type, and the sort
retrieve all data from database, and sort it in your node.js program.
But both are terrible and ugly
if you wanna sort a String column but parse it as Float. This action would scan all data in that collection, and can not use index. It's very very slow action.
So I think the fastest and correct operation is convert the String column to Float in your mongodb database. And then you can use normal .sort('-detail_info.overall_rating') to get things done.

Answer 2

user collation after sort query it will sort string float number in ascending and descending order both correctly.
cenicSpot.find({'name': new RegExp(req.query.keyword)}, )
.sort('-detail_info.overall_rating')
.collation({ locale: "en-US", numericOrdering: true })
.skip(pageSize * pageNumber)
.limit(pageSize)
.exec(function (err, scenicSpots) {
if (err) {
callback(err);
} else {
callback(null, scenicSpots);
}
});