how to group objects and display all expected fields in the query with MongoDB-CodePudding

I have the collection below, I need to make a query that group by confrontationId and display the results as expected, is there a way to do this with MongoDB, I need to group only the matches..

 {
    "rounds": {
        "matches": [{
                "id": "8cac353e-fb04-4a9a-b340-ed64e1094ff1",
                "confrontationId": "2f2c58c9-f1be-4914-8aee-03d00725a0be",
                "arena": "Tacoma Dome",
                "status": "FINISHED"
            },
            {
                "id": "d8ff6322-824c-455c-b59d-d837d0188d93",
                "confrontationId": "41d85805-5571-42c6-a38e-e03fd8fcdc96",
                "arena": "Baku Crystal Hall",
                "status": "FINISHED"
            },
            {
                "id": "e23dc4ce-24de-4f7f-b5b0-9b124ec0e71a",
                "confrontationId": "2f2c58c9-f1be-4914-8aee-03d00725a0be",
                "arena": "Greensboro Coliseum",
                "status": "FINISHED"
            }
        ]
    }
}

Expected:

[
    [{
            "id": "8cac353e-fb04-4a9a-b340-ed64e1094ff1",
            "confrontationId": "2f2c58c9-f1be-4914-8aee-03d00725a0be",
            "arena": "Tacoma Dome",
            "status": "FINISHED"
        },
        {
            "id": "e23dc4ce-24de-4f7f-b5b0-9b124ec0e71a",
            "confrontationId": "2f2c58c9-f1be-4914-8aee-03d00725a0be",
            "arena": "Greensboro Coliseum",
            "status": "FINISHED"
        }
    ],
    [{
        "id": "d8ff6322-824c-455c-b59d-d837d0188d93",
        "confrontationId": "41d85805-5571-42c6-a38e-e03fd8fcdc96",
        "arena": "Baku Crystal Hall",
        "status": "FINISHED"
    }]
]

CodePudding user response：

$unwind unwind $rounds.matches
$group group by confrontationId and push root to item

db.collection.aggregate([
  {
    "$unwind": "$rounds.matches"
  },
  {
    "$group": {
      "_id": "$rounds.matches.confrontationId",
      "items": {
        $push: "$$ROOT"
      }
    }
  }
])

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