How to sort Arrays of Object using aggregation in mongoDB

Question

How can I sort dueDate using aggregate?

todos: [
    {
        task: {
            type: String,
            trim: true,
            required: 'Please Enter your Task',
        },
        dueDate: Date,
        dueTime: String,
    },
],

I tried these things but it didn't work.

db.server.aggregate(
    { $unwind: '$todos' },
    { $sort: { 'todos.dueDate': -1 } },
    { $group: { _id: '$_id', todos: { $push: '$todos' } } },
    { $project: { 'todos.dueDate': '$dueDate' } }
);

And

db.server.aggregate(
    { $unwind: '$todos' },
    { $sort: { 'todos.dueDate': -1 } },
    { $group: { "_id": "$_id", todos: { $push: '$todos' } } },
);

I am not able to understand what I am doing wrong in the aggregation.

Example:-

Sample Input

{
  _id: 603ba275cc571e2404e0dd1b,
  task: 'task 1',
  dueDate: 2021-02-27T18:30:00.000Z,
  dueTime: ''
},{
  _id: 603ba285cc571e2404e0dd1c,
  task: 'task 2',
  dueDate: 2021-03-30T18:30:00.000Z,
  dueTime: '07:32 PM'
},{
  _id: 603ba290cc571e2404e0dd1d,
  task: 'task 3',
  dueDate: 2021-03-08T18:30:00.000Z,
  dueTime: '07:32 PM'
},{
  _id: 603ba3a7fea412537c295056,
  task: 'task4',
  dueDate: 2021-03-01T18:30:00.000Z,
  dueTime: '07:37 PM'
}

Sample Output


{
  _id: 603ba275cc571e2404e0dd1b,
  task: 'task 1',
  dueDate: 2021-02-27T18:30:00.000Z,
  dueTime: ''
},{
  _id: 603ba3a7fea412537c295056,
  task: 'task4',
  dueDate: 2021-03-01T18:30:00.000Z,
  dueTime: '07:37 PM'
},{
  _id: 603ba290cc571e2404e0dd1d,
  task: 'task 3',
  dueDate: 2021-03-08T18:30:00.000Z,
  dueTime: '07:32 PM'
},{
  _id: 603ba285cc571e2404e0dd1c,
  task: 'task 2',
  dueDate: 2021-03-30T18:30:00.000Z,
  dueTime: '07:32 PM'
}

the dates are store in this format Tue Mar 09 2021 00:00:00 GMT+0530 (India Standard Time) — Arpit Falcon
– Arpit Falcon, Commented Feb 28, 2021 at 15:20

eol · Accepted Answer · 2021-02-28 15:31:20Z

1

If your goal is to group the tasks elements into separate groups by their dueDate and then sort those groups, here's what you can do:

db.collection.aggregate([
  {
    "$unwind": "$todos"
  },
  {
    $group: {
      _id: "$todos.dueDate",
      todos: {
        $push: "$$ROOT"
      }
    }
  },
  {
    $sort: {
      "_id": -1
    }
  },
  
])

Here's a working example on mongoplayground: https://mongoplayground.net/p/n3cfrLvR2WM

After OP edited the question and clarified what the expceted result is, this can be simplified to:

db.collection.aggregate([
  {
    "$unwind": "$todos"
  },
  {
    $sort: {
      "todos.dueDate": 1
    }
  }
])

Mongoplayground: https://mongoplayground.net/p/YVCAiXrJJPv

edited Feb 28, 2021 at 15:31

answered Feb 28, 2021 at 15:09

eol

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6 Comments

eol Over a year ago

See edit .. note that you should always include expected results to your question to make it easier to help you ..

Arpit Falcon Over a year ago

I dont know why but it is still now working

eol Over a year ago

Well, it works as expected on the mongoplayground, right? Or is this not what you want?

Arpit Falcon Over a year ago

Ya, it was working on the mongoplayground but it is not working in my project :(

eol Over a year ago

Note that you need to use "todos.dueDate": 1 if you want the record to be sorted ascending. Is that the problem?

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