Mongoid update_attributes not getting persisted

Here is a simple Model.

class Event
  include Mongoid::Document

  field :name, type: String
  field :schedule, type: String
  field :description, type: String
  field :active, type: Boolean, default: true
  key :name

end

1.We create and event

ruby-1.9.2-p0 > event = Event.ne开发者_Python百科w(:name => "event1")
 => #<Event _id: event1, _type: nil, _id: "event1", name: "event1", schedule: nil, description: nil, active: true> 
ruby-1.9.2-p0 > event.save!
 => true

2.Know lets find the event

ruby-1.9.2-p0 > event = Event.find("event1")
=> #<Event _id: event1, _type: nil, _id: "event1", name: "event1", schedule: nil, description: nil, active: true> 

3.So update event attributes

ruby-1.9.2-p0 > event.update_attributes!(:name => "new name")
 => true 

4.Lets try to find the event

ruby-1.9.2-p0 > event = Event.find("new name")
Mongoid::Errors::DocumentNotFound: Document not found for class Event with id(s) new name.

5.Ooops not found, but the old one is still persisted

ruby-1.9.2-p0 > event = Event.find("event1")
 => #<Event _id: event1, _type: nil, _id: "event1", name: "event1", schedule: nil, description: nil, active: true>

What I am doing wrong ? I hope this is not a bug.

I don't believe MongoDB lets you alter an _id field. When I try it using the standard mongo shell, I get this error (meaning it's not a Mongoid limitation, it's a limitation in the actual Mongo software):

Mod on _id not allowed

Whenever you need to alter the name field, you'll probably need to:

1. Copy it to a new record with the new name.
2. Delete the old record