validates_uniqueness_of before ActiveRecord::RecordNotUnique

Question

I have the following class in a Rails 3.1.1 app:

class User < ActiveRecord::Base  
  attr_accessible :email, :password, :password_confirmation, :remember_me, :username, :admin, :moderator, :bio
  validates_presence_of :username
  validates_uniqueness_of :username, :case_sensitive => false
  validates_uniqueness_of :email,  :case_sensitive => false

and in my migrations:

add_index :users, :email,                :unique => true
add_index :users, :username,             :unique => true

However, when I try to create two users with duplicate emails or usernames I get a DB level exception rather than a failing validation:

ActiveRecord::RecordNotUnique in RegistrationsController#create
PGError: ERROR:  duplicate key value violates unique constraint "index_users_on_username"

There are other validations that work perfectly, but why aren't the uniqueness validations being performed before the DB create?

Answer 1

Try something like this:

class User < ActiveRecord::Base
  attr_accessible :email, 
              :password, 
              :password_confirmation, 
              :remember_me, 
              :username, 
              :admin, 
              :moderator, 
              :bio
  validates :username, :uniqueness => { :case_sensitive => false }, :presence => true
  validates :email,    :uniqueness => { :case_sensitive => false }