mongodb sorting using array field

Question

This is my mongodb document

{
    "_id" : "a3s6HzG9swNB3bQ78",
    "comments" : [ 
        {
            "cmt_text" : "opp",
            "vCount" : 2,

        }, 
        {
            "cmt_text" : "o2",

            "vCount" : 5,

        }, 
        {
            "cmt_text" : "o3",

            "vCount" : 3,

        }
    ],

    "question" : "test ques 3"
}

i want to sort the result using the vCount field how to achieve this

i tried the following but seems to be not working

Coll.findOne( {_id:this._id},{sort:{ "comments.vCount" : 1 }});

Coll.findOne( {_id:this._id},{sort:{ "comments.$.vCount" : 1 }});

anyone have idea about this???

EDIT

we are returning only one document and i want to display that document comment array values according to the vCount. my code

{{#each all_comments.comments}}

    <br>{{cmt_text}}</p>
{{/each}}

i want to display like below

o2
o3
opp

EDIT

this is working fine in shell

db.testCol.aggregate([
                    { $unwind: "$comments" },
                    { $group: { _id: { id:"$_id", vcount:"$comments.vCount"} } },
                    { $sort: { "_id.vcount":1 }}
                  ])

why is it not working in my meteor app it says

error:object has no method aggregate

score 3 · Answer 1 · edited May 23 '17 at 11:59

3

This is correct:

Coll.findOne( { _id: this._id }, { sort: { 'comments.vCount' : 1 } } );

No $ in front of sort.

EDIT:

If you want to sort the nested array, look here.

edited May 23 '17 at 11:59

Community

1
1

answered Feb 19 '14 at 17:07

heinob

19,127
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it is showing error `uncaught exception: error: { "$err" : "Unsupported projection option: comments.vCount", "code" : 13097 }` – Sasikanth Feb 19 '14 at 17:15

score 2 · Accepted Answer · answered Feb 19 '14 at 19:26

aggregate isn't currently available on the client. You can just do a findOne, extract the comments array, and return a sorted version to the template. For example:

Template.allComments.helpers({
  comments: function() {
    var coll = Coll.findOne(this._id);
    return _.sortBy(coll.comments, function(comment) {
      return -comment.vcount;
    });
  }
});

<template name="allComments">
  {{#each comments}}
    <br>{{cmt_text}}</p>
  {{/each}}
</template>

score 1 · Answer 3 · answered Feb 19 '14 at 17:46

You should learn aggregation for dealing with subdocuments, arrays and also with subdocuments in arrays. For your sort question this could work.

db.testCol.aggregate([
                    { $unwind: "$comments" },
                    { $group: { _id: { id:"$_id", vcount:"$comments.vCount"} } },
                    { $sort: { "_id.vcount":1 }}
                  ])

EDIT: In according to your edit you could add $project operator like;

db.testCol.aggregate([
                        { $unwind: "$comments" },
                        { $group: { _id: { id:"$_id", vcount:"$comments.vCount", text:"$comments.cmt_text"} } },
                        { $sort: { "_id.vcount":1 }},
                        { $project: { text: "$_id.text", _id:0}}
                      ])

Error:Object [object Object] has no method 'aggregate' working fine in mongoshell but not in my program — Sasikanth, Feb 19 '14 at 18:28

mongodb sorting using array field

3 Answers3