MongoDB - Convert response into array of object in query

Question

I wrote a simple query in MongoDB to get all data related to the product ID. Now I want to convert my response into an array of objects. Please see below.

Query:

db.collection.find({ "product_id": 1212 })

Getting response:

[
  {
    "product_id": 1212,
    "name": "sprit",
    "category_id": 1234,
    "category": "drink"
  },
  {
    "product_id": 1212,
    "name": "sprit",
    "category_id": 2122,
    "category": "soda"
  },
  {
    "product_id": 1212,
    "name": "sprit",
    "category_id": 2121,
    "category": "mocktail"
  },
  {
    "product_id": 1212,
    "name": "sprit",
    "category_id": 2121,
    "category": "mocktail"
  }
]

I want to convert the data in a different format by MongoDB query and remove duplicate category_id.

Required response:

[
  {
    "product_id": 1212,
    "name": "sprit",
    "categogies": [
      {
        "category_id": 1234,
        "category": "drink"
      },
      {
        "category_id": 2122,
        "category": "soda"
      },
      {
        "category_id": 2121,
        "category": "mocktail"
      }
    ]
  }
]

Answer 1

Group by product_id via $group and add distinct document into the categogies array via $addToSet.

db.collection.aggregate([
  {
    $match: {
      "product_id": 1212
    }
  },
  {
    $group: {
      _id: "$product_id",
      name: {
        $first: "$name"
      },
      categogies: {
        $addToSet: {
          "category_id": "$category_id",
          "category": "$category"
        }
      }
    }
  },
  {
    $project: {
      _id: 0,
      product_id: "$_id",
      name: "$name",
      categogies: "$categogies"
    }
  }
])

Demo @ Mongo Playground