Change _id value from a number to ObjectId()?

Question

I have a collection (510 documents) where _id are numbers :

{    "_id" : "1",
    "name" : "eric" }

{    "_id" : "2",
    "name" : "tom" }
....

and I want to change their values to ObjectId() to be like this:

{    "_id" : ObjectId("53849e258bf3be07804a00d0"),
    "name" : "eric" }

{    "_id" : ObjectId("53849e388bf3be07804a00d1"),
    "name" : "tom" }
....

so I tried:

db.contacts.find().forEach(function(doc) {
    db.contacts.update(
        { "_id": doc._id },
        { "$set": { "_id": ObjectId()} }
    );
    })

but it doesn't work, I got like result:

Mod on _id not allowed

Thank you.

http://stackoverflow.com/questions/4012855/how-update-the-id-of-one-mongodb-document — Kiran Pagar, May 27 '14 at 15:53

score 4 · Accepted Answer · edited May 23 '17 at 12:11

You cannot change the _id of an Object in a collection once it is created (it is not allowed by mongodb at all). However you could copy the full content of the object execpt of the _id and add your new _id with the ObjectId and insert it into your collection. Afterwards you can remove all the Objects where the _id is a number. It's a bit more complicated but the result is the same (and it works).

Have a look here.

Change _id value from a number to ObjectId()?

1 Answers1