code: func (kv *KeyValue) Wipe() error {
  	if kv.Gate != nil {
  		kv.Gate.Start()
  		defer kv.Gate.Done()
  	}
  	_, err := kv.DB.Exec(kv.sql("DELETE FROM /*TPRE*/rows"))
  	return err
  }
docs: // TODO(mpl): implement Wipe for each of the SQLs, as it's done for MySQL, and
  // remove this one below.