code: private void modify(Set<Permission> permissions, IResource resource, String user, String op) throws RequestExecutionException
      {
          process(String.format("UPDATE %s.%s SET permissions = permissions %s {%s} WHERE username = '%s' AND resource = '%s'",
                                Auth.AUTH_KS,
                                PERMISSIONS_CF,
                                op,
                                "'" + StringUtils.join(permissions, "','") + "'",
                                escape(user),
                                escape(resource.getName())));
      }
docs: Adds or removes permissions from user's 'permissions' set (adds if op is "+", removes if op is "-")