relation_for_destroy

# File activerecord/lib/active_record/persistence.rb, line 469
    def relation_for_destroy
      pk         = self.class.primary_key
      column     = self.class.columns_hash[pk]
      substitute = self.class.connection.substitute_at(column, 0)

      relation = self.class.unscoped.where(
        self.class.arel_table[pk].eq(substitute))

      relation.bind_values = [[column, id]]
      relation
    end