MONGODB 如果字段存在或什么都不做则聚合转换

Question

I need convert a field in MONGODB but if the field/path doesn't exist, I don't want it to be created. I try using $$remove, $setfield, but without success in both. Please, someone with knowledge on MongoDB, help me.

Note: check the images please. I tried to use $$remove instead of "null" but still nothing

[{
        "$addFields": {
            "fieldExists": {
                "$cond": [{
                        "$ifNull": ["$documentoAlterado.nfeProc.NFe.infNFe.total.ICMSTot.vBC", null]
                    }, true, false]
            }
        }
    }, {
        "$addFields": {
            "convertResult": {
                "$cond": [{
                        "$eq": ["$fieldExists", true]
                    }, {
                        "$convert": {
                            "input": "$documentoAlterado.nfeProc.NFe.infNFe.total.ICMSTot.vBC",
                            "to": "decimal",
                            "onError": "$documentoAlterado.nfeProc.NFe.infNFe.total.ICMSTot.vBC",
                            "onNull": "$documentoAlterado.nfeProc.NFe.infNFe.total.ICMSTot.vBC"
                        }
                    }, null]
            }
        }
    }, {
        "$addFields": {
            "documentoAlterado.nfeProc.NFe.infNFe.total.ICMSTot.vBC": "$convertResult"
        }
    }
]

exists convert result replceRoot

ExistsMongoPlaygroud NotExistsMongoPLayground

Answer 1

Use $set to conditionally update the documentoAlterado object with the $convert result.

db.collection.aggregate([
  {
    "$addFields": {
      "documentoAlterado.nfeProc.NFe.infNFe.total.ICMSTot.vBC": {
        "$convert": {
          "input": "$documentoAlterado.nfeProc.NFe.infNFe.total.ICMSTot.vBC",
          "to": "decimal",
          "onError": "$$REMOVE",
          "onNull": "$$REMOVE"
        }
      }
    }
  },
  {
    "$set": {
      "documentoAlterado": {
        "$cond": {
          "if": {
            $eq: [
              {},
              "$documentoAlterado.nfeProc.NFe.infNFe.total.ICMSTot"
            ]
          },
          "then": {
            // keep the other fields you want
            "cteProc": "$documentoAlterado.cteProc"
          },
          "else": "$documentoAlterado"
        }
      }
    }
  }
])

Mongo Playground