mongodb select nested array with status field [duplicate]

Question

I have the object below in MongoDB and my back end is using nodeJS. to retrieve the data from DB. the "_id" field is provided in the API body.

questions = [
    {
        "_id": "idq1"
        "questiontext": "some question",
        "author": "auth2",
        "Answers": []
    },
    {
        "_id": "idq2"
        "questiontext": "some question",
        "author": "auth1",
        "Answers": [
            {
                "author": "auth1",
                "comments" [...],
                "status" : "1"
            },
            {
                "author": "auth2",
                "comments" [...],
                "status" : "0"
            },
            {
                "author": "auth3",
                "comments" [...],
                "status" : "1"
            }
        ]
    }
    ]

Expected result:

I want to get an object where the status is equal to "1" my expected result is given below :

    result = {
    "_id": "idq2"
    "questiontext": "some question",
    "author": "auth1",
    "Answers": [
        {
            "author": "auth1",
            "comments" [...],
            "status" : "1"
        },
        {
            "author": "auth3",
            "comments" [...],
            "status" : "1"
        }
    ]
}

Understanding the aggregation, it always return an array, so an array should be fine too.

Does this answer your question: stackoverflow.com/questions/61533627/… — mickl
– mickl, Commented May 25, 2020 at 17:04
Thank you so much! it was a big help, I change it a bit and it works good — Hosein Djadidi
– Hosein Djadidi, Commented May 25, 2020 at 17:15

Hosein Djadidi · Accepted Answer · 2020-05-25 17:17:24Z

0

I try the solution below and it work! Thanks to @mickl for his solution on this post: MongoDB filter objects array content based on object member

const question =  await Question.aggregate([

    { $match: {_id: ObjectId(req.params.id)}}
    ,{
      $addFields: {
        Answers: {
          $filter: {
            input: "$Answers",
            cond: {
              $eq: [
                "$$this.status",
                "1"
              ]
            }
          }
        }
      }
    }
  ])

answered May 25, 2020 at 17:17

Hosein Djadidi

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