Get And Sort In Array Mongodb

Question

I have document like this

{
    "id": "1",
    "myarray": [
        {
            "_id": "4",
            "name": "d",
            "order": 4
        },
        {
            "_id": "1",
            "name": "a",
            "order": 1
        },
        {
            "_id": "2",
            "name": "b",
            "order": 2
        }
    ]
}

i want to see sort data in array by order when get from db i am trying some query like below but it seems not OK and nothing changed

 db.collection.aggregate([{$unwind: "$myarray"},{$project: {orders:"$myarray.order"}},{$group: {_id:"$_id",min:{$min: "$orders"}}},{$sort: {min:1}}])

db.myarray.find({},{$sort:{"myarray.order":-1}})
db.collection.find({"_id":"1"}).sort({"myarray.order":1})

what is correct query?

I need something like this

db.collection.find({"_id":"1"}).sort({"myarray.order":1})

The Aggregation Framework works well for such queries, why don't you try db.collection.aggregate({ $unwind: '$myarray' }, { $sort: {'myarray.order': -1 }})? — chridam
– chridam, Commented Mar 16, 2015 at 12:11

Sede · Accepted Answer · 2015-03-16 12:20:06Z

3

You can use aggregation pipelines

db.collection.aggregate([
    { "$unwind": "$myarray" }, 
    { "$sort": { "myarray.order": 1 }}, 
    { "$group": { "_id": "$_id", "myarray": { "$push": "$myarray" }}}
])

answered Mar 16, 2015 at 12:20

Sede

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Comments

Neil Lunn · Accepted Answer · 2015-03-16 13:05:42Z

1

To sort in a response and not permanently:

db.collection.aggregate([
    { "$match": { "_id": 1 } },
    { "$unwind": "$myarray" },
    { "$sort": { "myarray.order": 1 } },
    { "$group": {
        "_id": "$_id",
        "myarray": { "$push": "$myarray" }
    }}
])

To alter permanently:

db.collection.update(
    { "_id": 1 }, 
    { "$push": { "myarray": { "$each": [], "sort": { "order": 1 } } }},
    { "multi": true }
)

If this is what you generally want then your best option is generally to $sort the array as you $push a new element or elements via $each as another modifier.

Of course if you $pull elements from the array the "current" syntax requires another query to be issued in order to sort the array just as is already shown.

It's generally better to keep your results in the order you expect, rather than order them in post processing, as the latter will always come at a cost that is greater than the former approach.

edited Mar 16, 2015 at 13:05

answered Mar 16, 2015 at 12:20

Neil Lunn

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2 Comments

Ali Kianinejad Over a year ago

it is ok but i need to get document with _id 1 and sort it's array data

Neil Lunn Over a year ago

@user298582 That is not a problem, see the edited information. The real issue as I see it is making the decision to either keep the arrays sorted or do it on request. Unless you change the sorting pattern all the time the former makes sense.

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