Rails HasAndBelongsToMany Association With Primary Key Error

When using has_and_belongs_to_many, I ran into this error,
ActiveRecord::HasAndBelongsToManyAssociationWithPrimaryKeyError

Primary key is not allowed in a has_and_belongs_to_many join table (articles_users).

So check the linked-table , articles_users in my case, if there is a pk set by default.

Solution

Put the :id => false to the migration create_table SQL.

create_table :articles_users, :id => false do |t|
  t.integer :article_id
  t.integer :user_id
end