Environment

Ruby: 1.9.2-p136
Rails: 3.0.4

Situation

Create project with STI for Users and inherit one type of User (Support) to another types (Administrator, Employee)

Models

#app/models/user.rb
class User < ActiveRecord::Base
end

#app/models/support.rb
class Support < User
end

#app/models/administrator.rb
class Administrator < Support
end

#app/models/employee.rb
class Employee < Support
end

Migration

#db/migrate/20110225123900_create_users.rb
class CreateUsers < ActiveRecord::Migration
  def self.up
    create_table :users do |t|
      t.string :type
    end
  end

  def self.down
    drop_table :users
  end
end

Console

Create instances of Administrator and Employee:

> Administrator.create
> Employee.create

Now get them(Support's users) using Support.all.

> Support.all
=> [#<Administrator id: 1, type: "Administrator">, #<Employee id: 2, type: "Employee">]

Now we reload environment and check Support.all again. And get this bug!

> reload!
> Support.all
=> []

Difference in SQL command

Before reload!

SELECT `users`.* FROM `users` WHERE (((`users`.`type` = 'Support' OR `users`.`type` = 'Administrator') OR `users`.`type` = 'Employee')

After reload!

SELECT `users`.* FROM `users` WHERE (`users`.`type` = 'Support')

Workaround

We can temporary repair it by using before method #all for parent class User:

> User.all
=> [#<Administrator id: 1, type: "Administrator">, #<Employee id: 2, type: "Employee">]
> Support.all
=> [#<Administrator id: 1, type: "Administrator">, #<Employee id: 2, type: "Employee">]