query(sql, values, cb) {
    const query = Connection.createQuery(sql, values, cb, {});
    this.getConnection((err, conn) => {
      if (err) {
        if (typeof query.onResult === 'function') {
          query.onResult(err);
        } else {
          query.emit('error', err);
        }
        return;
      }
      try {
        conn.query(query).once('end', () => {
          conn.release();
        });
      } catch (e) {
        conn.release();
        throw e;
      }
    });
    return query;
  }
pool cluster query
@param {*} sql
@param {*} values
@param {*} cb
@returns query