@Override
  public void drop_constraint(DropConstraintRequest req)
      throws MetaException, InvalidObjectException {
    String catName = req.isSetCatName() ? req.getCatName() : getDefaultCatalog(conf);
    String dbName = req.getDbname();
    String tableName = req.getTablename();
    String constraintName = req.getConstraintname();
    startFunction("drop_constraint", ": " + constraintName);
    boolean success = false;
    Exception ex = null;
    RawStore ms = getMS();
    try {
      ms.openTransaction();
      ms.dropConstraint(catName, dbName, tableName, constraintName);
      if (transactionalListeners.size() > 0) {
        DropConstraintEvent dropConstraintEvent = new DropConstraintEvent(catName, dbName,
            tableName, constraintName, true, this);
        for (MetaStoreEventListener transactionalListener : transactionalListeners) {
          transactionalListener.onDropConstraint(dropConstraintEvent);
        }
      }
      success = ms.commitTransaction();
    } catch (Exception e) {
      ex = e;
      throw handleException(e).throwIfInstance(MetaException.class)
          .convertIfInstance(NoSuchObjectException.class, InvalidObjectException.class)
          .defaultMetaException();
    } finally {
      if (!success) {
        ms.rollbackTransaction();
      } else {
        for (MetaStoreEventListener listener : listeners) {
          DropConstraintEvent dropConstraintEvent = new DropConstraintEvent(catName, dbName,
              tableName, constraintName, true, this);
          listener.onDropConstraint(dropConstraintEvent);
        }
      }
      endFunction("drop_constraint", success, ex, constraintName);
    }
  }
Checks whether the repl.last.id is being updated.
@param oldDb the old db object
@param newDb the new db object
@return true if repl.last.id is being changed.
standalone-metastore/metastore-server/src/main/java/org/apache/hadoop/hive/metastore/HMSHandler.java