ERROR: delete on table violates foreign key constraint. Key id is still referenced from table (many)

Question

I'm working with Rails and PostgreSQL and have a basic one-to-many relationship going on, one Auction has many Bids. However when I try and delete an auction (that has bids present) I get the following error:

ERROR: update or delete on table "auctions" violates foreign key constraint "fk_rails_43e9021cbf" on table "bids". DETAIL: Key(id)=(1) is still referenced from table "bids".

Deleting auctions with no bids gives no error.

The part that confuses me is that inside my Auction model, I have:

has_many :bids, dependent: :destroy

Since I have a dependent destroy clause, why am I still getting this error?

EDIT: I've tried dropping the whole DB, then recreating/re-migrating everything - still get the same error.

Answer 1

From Rails v4.2 you can do this:

Create a migration to update the foreign keys

20160321165946_update_foreign_key.rb

class UpdateForeignKey < ActiveRecord::Migration
  def change
    # remove the old foreign_key
    remove_foreign_key :posts, :users

    # add the new foreign_key
    add_foreign_key :posts, :users, on_delete: :cascade
  end
end