code: private boolean isNamespace(String database) {
      Collection<String> tables = getMetaStoreUtil().getAllTables(database);
      for (String name : tables) {
        if (isReadable(database, name)) {
          return true;
        }
      }
      return false;
    }
docs: Returns true if there is at least one table in the give database that can
  be read.
  
  @param database a Hive database name
  @return {@code true} if there is at least one readable table in database
  @see {@link #isReadable(String, String)}