Rails Scaffold destroy not working as expected - ruby-on-rails

Question

I was adding uniqueness validation to the model in charge of user registration. The username should be uniqueness.
I created a user when testing some days ago, lets call it "example-guy". Then I deleted him from the scaffolding user interface and now when trying to register a new user as "example-guy", it returns that the name has already been taken.
So how can I fix this from the DB without reverting to its "birth-state" and modify the controller to actually destroy the table entry?
Or maybe Rails is keeping track of what was writed to DB, even after destruction?
Im using omniauth-identity, the user model:
class User < ActiveRecord::Base
attr_accessible :name, :provider, :uid, :email
# This is a class method, callable from SessionsController
# hence the "User."
def User.create_with_omniauth(auth)
user = User.new()
user.provider = auth["provider"]
user.uid = auth["uid"]
user.name = auth["info"]["name"]
# ADD EMAIL
user.email = auth["info"]["email"]
user.save
return user
end
end
User controller's destroy function:
# DELETE /users/1
# DELETE /users/1.json
def destroy
#user = User.find(params[:id])
#user.destroy
respond_to do |format|
format.html { redirect_to users_url }
format.json { head :no_content }
end
end
end
Validations are made trought "Identity" model inherited from omniauth's active record:
class Identity < OmniAuth::Identity::Models::ActiveRecord
attr_accessible :email, :name, :password_digest, :password, :password_confirmation
#attr_accessible :email, :name, :password_digest :password, :password confirmation
validates_presence_of :name
validates_uniqueness_of :name
validates_length_of :name, :in => 6..24
validates_format_of :name, :with => /^[a-z]+$/
validate :name_blacklist
validates_uniqueness_of :email, :case_sensitive => false
validates_format_of :email,
:with => /\A([^#\s]+)#((?:[-a-z0-9]+\.)+[a-z]{2,})\Z/i,
:message => "doesn't look like a proper email address"
#validates_presence_of :password, on: :create
#validates_presence_of :password_confirmation
validates_length_of :password, :in => 6..24
def name_blacklist
unless self.name.blank? then
case self.name
when "user", "photo", "photos",
"application", "sessions",
"identities", "home"
self.errors.add(:name, "prohibited")
end
end
end
end
Identities controllar manage registration form sent to omniauth and calling new.html.erb:
class IdentitiesController < ApplicationController
def new
#identity = env['omniauth.identity']
end
end
Thanks in advance.

Answer 1

I'm not entirely sure what caused the problem, but I came across a similar problem but with email addresses with a Devise based user.
I was wanting to re-use the same email on a different user. I changed the original user to a different email, but when I then tried to update the second user with the "now unique" email, it failed the unique validation.
A query for users with that email returned nothing.
It seemed to be cache-related to the uniqueness constraint, as restarting the server, after deleting the email address, fixed the problem.