public boolean isFieldSigned(int fieldOrdinal) {
   RelDataType type = getFieldType(fieldOrdinal);
   if (SqlTypeUtil.isNumeric(type)) {
     return true;
   } else {
     return false;
   }
 }
 public boolean isFieldCaseSensitive(int fieldOrdinal) {
   RelDataType type = getFieldType(fieldOrdinal);
   return SqlTypeUtil.inCharFamily(type);
 }