mongoose/mongodb query multiple sort

Question

i'm quite new to mongodb. i manage to get a basic idea of a simple sort based only 1 parameter. what if there are more than 2 sort parameters. for instance, in a database made up of woodworking projects that have attributes totalCuttingTime and favorited.

Is the following a correct mongoose/mongodb function to find a list of projects that have the least totalCuttingTime and order in according to highest favoriteCounts to lowest.

var ProjectModel= mongoose.model('Project', schema);

exports.getMinCuttingTime = function(number, callback){ 
    var leastCutTimeResult = ProjectModel.find().sort({totalCuttingTime: 1}).select({_id: 1}).limit(number).exec(
            function(err, projects) {
                callback(null, projects)
            }
        );

    var result = leastCutTimeResult.find().sort({favoriteCount: -1}).select({_id: 1}).limit(number).exec(
            function(err, projects) {
                callback(null, projects)
            }
        ); 

    return result;
}

it is correct. Sort by two fields in Mongo is the same as doing order by A, B in SQL query. — Asya Kamsky
– Asya Kamsky, Commented Nov 26, 2012 at 16:10
@AsyaKamsky and is the syntax correct? where ProjectModel comes from mongoose.model('Project, schema) — bouncingHippo
– bouncingHippo, Commented Nov 26, 2012 at 16:17
sorry, can't tell you - I was commenting on the approach being correct - selecting the smallest value for totalCuttingTime and then selecting and sorting by another value all documents which have that totalCuttingTime. — Asya Kamsky
– Asya Kamsky, Commented Nov 26, 2012 at 20:05

JohnnyHK · Accepted Answer · 2015-08-03 14:36:14Z

81

You need to put both sort terms into one object:

exports.getMinCuttingTime = function(number, callback){ 
    ProjectModel.find()
        .sort({totalCuttingTime: 1, favoriteCount: -1})
        .select({_id: 1})
        .limit(number)
        .exec(
            function(err, projects) {
                callback(null, projects)
            }
        );
};

It's worth noting that the ECMA-262 standard on which Node.js is based doesn't specify that an object's property order is maintained, and it's only a de facto standard to match insertion order. To eliminate any doubt, you can use an array instead:

.sort([['totalCuttingTime', 1], ['favoriteCount', -1]])

edited Aug 3, 2015 at 14:36

answered Nov 27, 2012 at 15:20

JohnnyHK

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5 Comments

Tamlyn Over a year ago

Given that object keys in JavaScript are technically unordered, is this guaranteed to sort by totalCuttingTime first, followed by favouriteCount?

pravin Over a year ago

@JohnnyHK I have been looking for a documentation on sort Mongoose and MongoDb, both define sort(<Object, String>) Mongoose Query#sort. Any link defining the sort with array definition ?

JohnnyHK Over a year ago

@pravin The native driver docs for Cursor#sort include the array style.

pravin Over a year ago

This being a nodejs specific feature should have been included in the mongoose docs.. Not sure why its not included.. anyways thank you

will_durant Over a year ago

Apparently sorting by array is no longer possible; either an object or string is required. Not clear if order is preserved when passing an object, but seems to be when passing a string: mongoosejs.com/docs/api.html#query_Query-sort

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