docs: private static String getType(Database db, VoltXMLElement elm) {
          final String type = elm.getStringAttribute("valuetype", "");
          if (! type.isEmpty()) {
              return type;
          } else if (elm.name.equals("columnref")) {
              final String tblName = elm.getStringAttribute("table", "");
              final int colIndex = elm.getIntAttribute("index", 0);
              return StreamSupport.stream(db.getTables().spliterator(), false)
                      .filter(tbl -> tbl.getTypeName().equals(tblName))
                      .findAny()
                      .flatMap(tbl ->
                              StreamSupport.stream(tbl.getColumns().spliterator(), false)
                                      .filter(col -> col.getIndex() == colIndex)
                                      .findAny())
                      .map(Column::getType)
                      .map(typ -> VoltType.get((byte) ((int)typ)).getName())
                      .orElse("");
          } else {
              return "";
          }
      }