MongoDB - Update data type for the nested documents

Question

I have this collection: (see the full collection here https://mongoplayground.net/p/_gH4Xq1Sk4g)

{
  "_id": "P-00",
  "nombre": "Woody",
  "costo": [
    {
      "tipo": "Cap",
      "detalle": "RAC",
      "monto_un": "7900 ",
      "unidades": "1",
      "total": "7900 "
    }
  ]
}

I tried a lot of ways to transform monto_un, unidades and total into int, but I always get an error. Neither of these works.

db.proyectos.updateMany({}, {'$set': {"costo.monto_un": {'$toInt': 'costo.$.monto_un'}}})

db.collection.update({},
[
  {
    $set: {
      costo: {
        monto_un: {
          $toInt: {
            costo: "$monto_un"
          }
        }
      }
    }
  }
],
{
  multi: true
})

MongoDB 5.0.9
Any suggestions?

Answer 1

1. $set - Update costo array.

   1.1. $map - Iterate each element in the costo array and return a new array.

   1.2. $mergeObjects - Merge current document with the document from 1.3.

   1.3. A document with the monto_un field. You need to trim space for the monto_un field in the current iterate document via $trim and next convert it to an integer via $toInt.

In case you are also required to convert the unidades and total as int, add those fields with the same operator/function logic as monto_un in 1.3. Those fields in the document (1.3) will override the existing value due to $mergeObjects behavior.

db.collection.update({},
[
  {
    $set: {
      costo: {
        $map: {
          input: "$costo",
          in: {
            $mergeObjects: [
              "$$this",
              {
                monto_un: {
                  $toInt: {
                    $trim: {
                      input: "$$this.monto_un"
                    }
                  }
                }
              }
            ]
          }
        }
      }
    }
  }
],
{
  multi: true
})

Sample Mongo Playground