docs: protected void dumpExprColumns(String header){
          System.out.println("\n\n*********************************************");
          System.out.println(header);
          try {
              System.out.println(getSQL());
          } catch (Exception e) {
          }
          for (int i = 0; i < exprColumns.length; ++i) {
              if (i == 0)
                  System.out.println("Visible columns:");
              if (i == indexStartOrderBy)
                  System.out.println("start order by:");
              if (i == indexStartAggregates)
                  System.out.println("start aggregates:");
              if (i == indexLimitVisible)
                  System.out.println("After limit of visible columns:");
  
              System.out.println(i + ": " + exprColumns[i]);
          }
  
          System.out.println("\n\n");
      }