code: @Override
  	public List<Metric> transform(QueryContext queryContext, List<Metric> metrics, List<String> constants) {
  		if (constants == null || constants.isEmpty()) {
  			return transform(queryContext, metrics);
  		}
  
  		if (constants.size() == 1) {
  			if (constants.get(0).toUpperCase().equals(FULLJOIN)){
  				fulljoinIndicator=true;
  				return transform(queryContext, metrics);
  			}else if(constants.get(0).toUpperCase().equals(INTERSECT)) {
  				fulljoinIndicator=false;
  				return transform(queryContext, metrics);
  			}
  		}
  		return mapping(metrics, constants);
  	}
docs: If constants is not null, apply mapping transform to metrics list. Otherwise, apply reduce transform to metrics list
  @param   metrics    list of metrics
  @param   constants  constants input
  
  @return  A list of metrics after mapping.