private Set<String> loadRoles(String user) { try (HiveMetastoreClient client = clientProvider.createMetastoreClient()) { List<Role> roles = client.listRoles(user, USER); if (roles == null) { return ImmutableSet.of(); } return ImmutableSet.copyOf(roles.stream().map(Role::getRoleName).collect(toSet())); } catch (TException e) { throw new PrestoException(HIVE_METASTORE_ERROR, e); } }