Deleting an object inside another object in Mongodb and for GOlang

Question

I wanna delete a specific object inside an object, My object:

{
    "_id" : ObjectId("5f577f3cce031ee00f5e32c9"),
    "UserId" : 0,
    "firstname" : "user 1",
    "lastname" : "user 1",
    "finishedTrainings" : [
        {
            "itemId" : 3,
            "validationScore" : 1,
            "timestamps" : {
                "createdat" : ISODate("2020-09-09T12:57:31.275Z"),
                "createdby" : 0,
                "updatedat" : ISODate("0001-01-01T00:00:00Z"),
                "updatedby" : 0
            },
            "isValidated" : true
        },
        {
            "itemId" : 0,
            "validationScore" : 0.6666666666666666,
            "timestamps" : {
                "createdat" : ISODate("2020-09-09T12:59:04.268Z"),
                "createdby" : 0,
                "updatedat" : ISODate("0001-01-01T00:00:00Z"),
                "updatedby" : 0
            },
            "isValidated" : true
        }
    ],
    "biography" : ""
}

and I wanna delete the finishedTraining(id=3),what would be the syntax in mongodb

Answer 1

//code output from mongo shell 4.2, windows10

//data set as given in problem statement
> db.userTraining.find().pretty();
{
        "_id" : ObjectId("5f577f3cce031ee00f5e32c9"),
        "UserId" : 0,
        "firstname" : "user 1",
        "lastname" : "user 1",
        "finishedTrainings" : [
                {
                        "itemId" : 3,
                        "validationScore" : 1,
                        "timestamps" : {
                                "createdat" : ISODate("2020-09-09T12:57:31.275Z"),
                                "createdby" : 0,
                                "updatedat" : ISODate("0001-01-01T00:00:00Z"),
                                "updatedby" : 0
                        },
                        "isValidated" : true
                },
                {
                        "itemId" : 0,
                        "validationScore" : 0.6666666666666666,
                        "timestamps" : {
                                "createdat" : ISODate("2020-09-09T12:59:04.268Z"),
                                "createdby" : 0,
                                "updatedat" : ISODate("0001-01-01T00:00:00Z"),
                                "updatedby" : 0
                        },
                        "isValidated" : true
                }
        ],
        "biography" : ""
}
//assuming objectID is unique for the document, you can query your own business field
> db.userTraining.update(
... {_id:ObjectId("5f577f3cce031ee00f5e32c9")},
... {$pull:{"finishedTrainings":{itemId:3}}},
... false,
... true
... );
WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })
> db.userTraining.find().pretty();
{
        "_id" : ObjectId("5f577f3cce031ee00f5e32c9"),
        "UserId" : 0,
        "firstname" : "user 1",
        "lastname" : "user 1",
        "finishedTrainings" : [
                {
                        "itemId" : 0,
                        "validationScore" : 0.6666666666666666,
                        "timestamps" : {
                                "createdat" : ISODate("2020-09-09T12:59:04.268Z"),
                                "createdby" : 0,
                                "updatedat" : ISODate("0001-01-01T00:00:00Z"),
                                "updatedby" : 0
                        },
                        "isValidated" : true
                }
        ],
        "biography" : ""
}
>
//above id=3 is deleted object from the array, other document object remain intact by using "$pull" in the update statement