So this 'works', in a sense: it's doing the UPDATE but also doing an INSERT. Why is that? Screenshot of server log: https://imgur.com/a/8FCPN

relationship.rb

class Relationship < ApplicationRecord
  belongs_to :outage
  belongs_to :child

  validate :outage_changed, if: :outage_id_changed?

  private

  def outage_changed
    Relationship.where(child_id: self.child_id).update_all(outage_id: self.outage_id)
  end
end