Normalized Object and array in MongoDB

Question

[
  {
    "data": {
      "id": "123",
      "name": "delta1"
    },
    "property_data": [
      {
        "ser_name": "Insights",
        "ser_value": "10000"
      },
      {
        "ser_name": "plans",
        "ser_value": "50000"
      }
    ]
  }
]

Explanation : property_data is an array. data is an object. Need to transform Array into an object, but the problem is if I do $unwind on property_data I get multiple times data objects, which I needed only once. I want to convert my data structure, into multiple documents but data should not be repeated again and again

Expected Output

[
  {
    "property_data": {
     "id": "123",
      "name": "delta1"
    }
  },
  {
    "property_data": {
      "ser_name": "Insights",
      "ser_value": "10000"
    }
  },
  {
    "property_data": {
      "ser_name": "plans",
      "ser_value": "50000"
    }
  },
]

Tom Slabbaert · Accepted Answer · 2021-03-01 16:51:40Z

1

This can be achieved with some basic structure manipulation, like so:

db.collection.aggregate([
  {
    $project: {
      property_data: {
        "$concatArrays": [
          "$property_data",
          [
            "$data"
          ]
        ]
      }
    }
  },
  {
    $unwind: "$property_data"
  },
  {
    $replaceRoot: {
      newRoot: {
        property_data: "$property_data"
      }
    }
  }
])

Mongo Playground

answered Mar 1, 2021 at 16:51

Tom Slabbaert

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