# File xapian.rb, line 186
    def unique_terms(&block)
      # termfreq is not supported by TermIterators from Queries
      Xapian._safelyIterate(self._dangerous_unique_terms_begin(),
                            self._dangerous_unique_terms_end(),
                            lambda {
                              |item| Xapian::Term.new(item.term, item.wdf)
                            },
                            &block)
    end