My User have a "notifications" field, that is an array

I'm trying to get it's notifications that haven't been read, so i've written this query:

await User.aggregate([
        { $unwind: '$notifications' },
        { $match: { 'notifications.read': false } },
        { $project: { "notifications": 1 } }
    ])

I've expected it to return something like:

[
    {
        "_id": "6201a79305489c2ae98b2753",
        "notifications": [
            {
                "_id": "62473e2f76b38858303b41d8",
                "text": "A tarefa tarefa 2 foi atualizada pela sua equipe!",
                "read": false,
                "date": "2022-04-01T18:02:23.813Z"
            },
            {
                "_id": "62473c4776b38858303b41a6",
                "text": "A tarefa finalizei foi atualizada pela sua equipe!",
                "read": false,
                "date": "2022-04-01T17:54:15.142Z"
            },
            {
                "_id": "62473e2f76b38858303b41d9",
                "text": "A tarefa tarefa 2 foi atualizada pela sua equipe!",
                "read": false,
                "date": "2022-04-01T18:02:23.814Z"
            }
        }
    ]
]

But it returned: [

    {
        "_id": "6201a79305489c2ae98b2753",
        "notifications": {
            "_id": "62473e2f76b38858303b41d8",
            "text": "A tarefa tarefa 2 foi atualizada pela sua equipe!",
            "read": false,
            "date": "2022-04-01T18:02:23.813Z"
        }
    },
    {
        "_id": "6227b07b04cd1196302dba06",
        "notifications": {
            "_id": "62473c4776b38858303b41a6",
            "text": "A tarefa finalizei foi atualizada pela sua equipe!",
            "read": false,
            "date": "2022-04-01T17:54:15.142Z"
        }
    },
    {
        "_id": "6227b07b04cd1196302dba06",
        "notifications": {
            "_id": "62473e2f76b38858303b41d9",
            "text": "A tarefa tarefa 2 foi atualizada pela sua equipe!",
            "read": false,
            "date": "2022-04-01T18:02:23.814Z"
        }
    }
]

How can i filter my user notifications by read:false and return it in the same array?

CodePudding user response：

I would ratter use $filter for this task like this:

db.collection.aggregate([
 { $match: { 'notifications.read': false } },
 {
   "$addFields": {
    "notifications": {
      "$filter": {
        "input": "$notifications",
        "as": "n",
        "cond": {
         $eq: [
            "$$n.read",
             false
         ]
      }
     }
    }
   }
  }
])

Explained:

1. match all documents having notifications.read:false
2. filter only notifications that have the read:false

playground