(Edited original issue)

Currently, has_many :models, :dependent => :nullify keeps the ID intact for its associated models. For example:

class User
  include Mongoid::Document
  has_many :comments

  # currently I need to do this, otherwise comment.user points to a deleted user ID
  before_destroy :orphan_comments
  protected
  def orphan_comments
    self.comments.each do |c|
      c.user = nil
      c.save
    end
  end

end

This is a pain when I want to write something like Comment.where(user: nil).

I'd propose to either auto-delete the associated model ID, or maybe provide a :dependent => :orphan feature which does this.

Using mongoid 3.0.17