MongoDB new ObjectId over array giving me same Id for all

Question

I am trying to update items in an array with unique ObjectIds (meaning add an object ID to array object that are missing them)

If I have an array of shirt objects in my collection and I try this:

db.people.update({        
    $and : [
        _id: ObjectId('5eeb44c6a042791d28a8641f'),
        {
            $or: [
            { 'shirts._id': { $eq:null } },
            { 'shirts._id':{ $exists:false } }
            ]
        }           
    ]
},{ 
    $set: { 'shirts.$[]._id': new ObjectId() }
},{
    "multi" : true
}

);

It generates IDENTICAL ObjectsIDs for each array element, I would put an unique index on this however, the use case probably wont see more then 2-3 items in the array with edge cases hitting 5-6, which seems like an abuse of an index

How can I update multiple records or multiple array objects with a unique ObjectId?

score 0 · Answer 1 · answered Jan 15 '19 at 01:49

0

When you use $set you're telling mongo to set that value to all matching elements. If the elements in the array are already defined as schemas, mongo will issue new ObjectIds for each one of them automatically.

Alternatively, you can use forEach and iterate over each matching element creating a new ObjectId.

answered Jan 15 '19 at 01:49

rlecaro2

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can you give a forEach example – j-p Jan 15 '19 at 06:49
Seeing your updated query, why are you doing it? Mongo can populate _ids automatically if you let it know the nested objects are schemas. – rlecaro2 Jan 15 '19 at 14:06
there is data already existant - that I want to correct - those objects dont have IDs – j-p Jan 15 '19 at 14:58
This answer is very similar https://stackoverflow.com/a/22657219/978697 – rlecaro2 Jan 15 '19 at 15:54

MongoDB new ObjectId over array giving me same Id for all

1 Answers1