Sort by field in nested array with Mongoose.js

Question

Given the data structure (based on my model) below how would I go about sorting the collection by cars.year in desc order with mongoose? So that first I find the max year in the cars array and then sort the collection by that.

{ "_id" : 1234,
  "dealershipName": "Eric’s Mongo Cars",
  "cars": [
           {"year": 2013,
            "make": "10gen",
            "model": "MongoCar",},
           {"year": 1985,
            "make": "DeLorean",
            "model": "DMC-12",}
  ]
},
{ "_id" : 1235,
  "dealershipName": "Eric’s Mongo Cars",
  "cars": [
           {"year": 2015,
            "make": "10gen",
            "model": "MongoCar",},
           {"year": 12001,
            "make": "DeLorean",
            "model": "DMC-12",}
  ]
}

I tried something like this with the aggregation function, but $unwind duplicates my results for each element in the cars array.

MyModel
    .aggregate([{
        $unwind: "$cars"
    }, {
        $project: {
            ...
            year: '$cars.year',
        }
    }, {
        $sort: {
            year: -1
        }
    }])
    .exec(function ...)

Is there a better or more efficient way to go about doing this?

Thanks in advance for your help.

JohnnyHK · Accepted Answer · 2015-01-16 22:57:47Z

2

What you're looking for is the standard behavior when sorting by a field in an array.

MyModel.find().sort('-cars.year').exec(function(err, docs) {...});

This will sort the docs descending using the maximum value of year in the elements of cars from each doc.

When sorting ascending, the minimum value is used.

answered Jan 16, 2015 at 22:57

JohnnyHK

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1 Comment

JohnnyHK Over a year ago

@AryehArmon What doesn't work about it for you? Keep in mind that it sorts the documents, not the cars arrays within each document.

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