code: func (pdb *BrokerCassa) GetValue(query sql.Expression, reqObj interface{}) (found bool, err error) {
  	it := pdb.ListValues(query)
  	stop := it.GetNext(reqObj)
  	return !stop, it.Close()
  }
docs: // GetValue - see the description in interface sql.Broker.GetValue()
  // GetValue just iterate once for ListValues()