private RowSet decode(final List<Object> rows, final RowSet rowSet) throws Exception {
    return (driver.isFetchingTable()) ? prepareFromRow(rows, rowSet) : decodeFromString(rows, rowSet);
  }
Returns the current UGI on the stack

@return UserGroupInformation

@throws HiveSQLException
service/src/java/org/apache/hive/service/cli/operation/SQLOperation.java