help with join tables and has_and_belongs_to_many

Hi,

I have a user model and a privilege model. They have the
has_and_belongs_to_many relationship. Here are the model defs:

class User < ActiveRecord::Base
  belongs_to :status
  has_and_belongs_to_many :privileges
end

class Privilege < ActiveRecord::Base
  has_and_belongs_to_many :users
end

Now I have a migration script to create the join table and populate a
few users with some privileges...

class CreateAndInitPrivileges < ActiveRecord::Migration
  def self.up
    create_table :privileges_users do |t|
      t.column :user_id, :integer, :null => false
      t.column :privilege_id, :integer, :null =>false
    end

    admin_priv = Privilege.find_by_name('admin')
    user_priv = Privilege.find_by_name('user')

    admin_user = User.find_by_email('admin@blah.com')
    admin_user.privileges << admin_priv
    admin_user.privileges << user_priv

    anon_user = User.find_by_email('anon@blah.com')
    anon_user.privileges << user_priv # BOMB HERE

  end

  def self.down
    drop_table :privileges_users
  end
end

The line
anon_user.privileges << user_priv
bombs because Rails tries to insert a row into privileges_users table
with id of 1, but that id is already taken because of the previous
admin_user.privileges << admin_priv
admin_user.privileges << user_priv
calls.

What's going on? Why is Rails not using the next highest id?

Thanks for the help,
-- Christopher

I do not know the why of it, but I hit it myself a few days ago.
Unless you really need that id column in the privileges table, use

   create_table(:privileges_users, :id=>false) do |t|
     t.column :user_id, :integer, :null => false
     t.column :privilege_id, :integer, :null =>false
   end

The table will be created without the id column and your inserts will work.

Awesome, that worked perfectly! And to think I was about to turn in
for the night... :wink:

Thank you very much.