Hi,

I thought it would be a good idea to have the option to have an array automatically add an _id field with new ObjectId per element if its an array of object.

In our use cases, we mostly update/delete items by their _id.

In the case where we want to do a bulk $push or something similar, there are currently no way of generating the _id's except looping through our array and generating the ids beforehand which is not ideal.

Another option would be to be able to use an update operator to generate a new ObjectId.

For example:

updateMany({},{
    $push: {
        "myArray": {
             someField: "someValue",
             _id: "$ObjectId"  // this would generate a unique object id per element that is inserted in this update operation.
         }
    }  
});