@Override
  public void onAddDefaultConstraint(AddDefaultConstraintEvent addDefaultConstraintEvent) throws MetaException {
    List<SQLDefaultConstraint> cols = addDefaultConstraintEvent.getDefaultConstraintCols();
    if (cols.size() > 0) {
      AddDefaultConstraintMessage colsInMsg = MessageBuilder.getInstance()
        .buildAddDefaultConstraintMessage(cols);
      NotificationEvent event =
        new NotificationEvent(0, now(), EventType.ADD_DEFAULTCONSTRAINT.toString(),
          msgEncoder.getSerializer().serialize(colsInMsg)
        );
      event.setCatName(cols.get(0).isSetCatName() ? cols.get(0).getCatName() : getDefaultCatalog(conf));
      event.setDbName(cols.get(0).getTable_db());
      event.setTableName(cols.get(0).getTable_name());
      process(event, addDefaultConstraintEvent);
    }
  }
@param addDefaultConstraintEvent add default constraint event
@throws MetaException
hcatalog/server-extensions/src/main/java/org/apache/hive/hcatalog/listener/DbNotificationListener.java