record_not_unique_rescue.rb

class MyThing < ActiveRecord::Base
  private
  def create_or_update
    super
  rescue ActiveRecord::RecordNotUnique => e
    case e.message
    when /index_mytable_on_sku_unique/
      errors.add(:sku, :taken)
    else
      # This should not happen; we want to know if we forgot to handle some unique constraint
      raise e
    end
    false
  end
end