public Set<String> getFunctionNames(String funcPatternStr) {
    lock.lock();
    try {
      return getFunctionNames(Pattern.compile(funcPatternStr));
    } catch (PatternSyntaxException e) {
      return Collections.emptySet();
    } finally {
      lock.unlock();
    }
  }
@param udfClass Function class.
@return True iff the fnExpr represents a hive built-in function.
ql/src/java/org/apache/hadoop/hive/ql/exec/Registry.java