Match with toObjectId in mongodb Aggregate-CodePudding

Really stuck with something that to me seems like it should be easy

I want to essentially do is convert the string of an objectId to an objectId and match on that, but I can't figure out how to do it...!

To be clear, I can't use { x: ObjectId(someObjectId) } because I'm wanting to serialise the query to JSON

Data:

[{
  "_id": {
    "$oid": "5f37eaaae4102600180078a8"
  },
  "Details": "Something A",
  "App": {
    "$oid": "5f37cec069106932d4710ea6"
  }
},{
  "_id": {
    "$oid": "5f3860f10a9db00018f2e2e3"
  },
  "Details": "Something B",
  "App": {
    "$oid": "5f37cec069106932d4710ea6"
  }
},{
  "_id": {
    "$oid": "5f3908a7db8fd70018b19942"
  },
  "Details": "Something C",
  "App": {
    "$oid": "5f37cec069106932d4710ea7"
  }
},{
  "_id": {
    "$oid": "5f390961db8fd70018b19945"
  },
  "Details": "Something D",
  "App": {
    "$oid": "5f37cec069106932d4710ea8"
  }
}
]

And query with something like:

[
  {
    '$match': {
      'App': {
        '$eq': {
          '$toObjectId': '5f37cec069106932d4710ea8'
        }
      }
    }
  }
]

the result obviously being:

{
  "_id": {
    "$oid": "5f390961db8fd70018b19945"
  },
  "Details": "Something D",
  "App": {
    "$oid": "5f37cec069106932d4710ea8"
  }
}

CodePudding user response：

You can do it like this:

db.collection.aggregate([
  {
    "$match": {
      "$expr": {
        "$eq": [
          "$App",
          {
            "$toObjectId": "5f37cec069106932d4710ea8"
          }
        ]
      }
    }
  }
])

Working example