Deleting an object inside another object in Mongodb and for GOlang - mongodb

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