node.js - Automatically remove referencing objects on deletion in MongoDB

Question

Let's suppose I have a schema like this:

var Person = new Schema({
    name: String
});

var Assignment = new Schema({
    name: String,
    person: ObjectID
});

If I delete a person, there can still be orphaned assignments left that reference a person that does not exist, which creates extraneous clutter in the database.

Is there a simple way to ensure that when a person is deleted, all corresponding references to that person will also be deleted?

Answer 1

You can add your own 'remove' Mongoose middleware on the Person schema to remove that person from all other documents that reference it. In your middleware function, this is the Person document that's being removed.

Person.pre('remove', function(next) {
    // Remove all the assignment docs that reference the removed person.
    this.model('Assignment').remove({ person: this._id }, next);
});