@Override
  public void onDropConstraint(DropConstraintEvent dropConstraintEvent) throws MetaException {
    String dbName = dropConstraintEvent.getDbName();
    String tableName = dropConstraintEvent.getTableName();
    String constraintName = dropConstraintEvent.getConstraintName();
    DropConstraintMessage msg = MessageBuilder.getInstance()
        .buildDropConstraintMessage(dbName, tableName, constraintName);
    NotificationEvent event =
        new NotificationEvent(0, now(), EventType.DROP_CONSTRAINT.toString(),
            msgEncoder.getSerializer().serialize(msg));
    event.setCatName(dropConstraintEvent.getCatName());
    event.setDbName(dbName);
    event.setTableName(tableName);
    process(event, dropConstraintEvent);
  }
@param dropConstraintEvent drop constraint event
@throws MetaException
hcatalog/server-extensions/src/main/java/org/apache/hive/hcatalog/listener/DbNotificationListener.java