I have schema name "comment".

Schema:

{
  "commentId": {
    "type": "String",
    "required": true,
    "unique": true
  },
  "from": {
    "type": "Object",
    "required": true
  },
  "createdTime": {
    "type": "Date"
  },
  "message": {
    "type": "String"
  }
}

Here from is a javascript Object which format is { "userId": "String", "name": "String" }. Now I need to query comment schema using "from.name". How can I do it?