MongoDB delete specific nested element in object array

Question

I want to remove this

"lightControl" : 75

from this

{
"_id" : "dfdfwef-fdfd-fd94284o-aafg",
"name" : "Testing",
"serialNumber" : "fhidfhd8ghfd",
"description" : "",
"point" : {
    "type" : "Point",
    "coordinates" : [
        10.875447277532754,
        20.940549069378634
    ]
},
"ancestors" : [ ],
"metadata" : {
    "measurement" : {
        "high" : "40000.0",
        "medium" : "25000.0"
    },
    "digitalTwin" : {
        
    },
    "emails" : [
        ""
    ],
    "lastMeasurementDate" : "2010-03-04T11:32:06.691Z",
    "lightControl" : 75
},
"tags" : [ ],
"createdAt" : ISODate("2019-12-07T15:22:10.988Z"),
"updatedAt" : ISODate("2020-03-08T15:38:21.736Z"),
"_class" : "com.test.demo.api.model.Device"
}

All I want is for this specific id, to completely delete the lightControl element from metadata. I have tried $pull, but I am probably missing something. Any ideas? Thank you in advance!

Answer 1

Your lightControl is not in array, for nested property, use the dot wrapped in doublequotes:

MongoDB shell:

db.getCollection('yourCollectionName').update({},{$unset:{
    "metadata.lightControl":""
}})

In case you have a list of objects with _id(s) instead of updating directly, assume Node.js client for MongoDB is used:

// import mongodb from "mongodb"; // ES6
const mongodb = require("mongodb");

var client = MongoClient(...);
var coll   = client["yourDbName"]["yourCollectionName"];
var objs   = []; // <-- The array with _id(s)

for (let i=0; i<objs.length; i++){
    let id = mongodb.ObjectID(objs[i]["_id"]);

    coll.update({ _id:id },{$unset:{ "metadata.lightControl":"" }});
}