@Override
  public TableSchema getResultSetMetadata(OperationHandle opHandle)
      throws HiveSQLException {
    TableSchema tableSchema = sessionManager.getOperationManager()
        .getOperation(opHandle).getParentSession().getResultSetMetadata(opHandle);
    LOG.debug(opHandle + ": getResultSetMetadata()");
    return tableSchema;
  }
If this is a background operation run asynchronously,
we block for a duration determined by a step function, before we return
However, if the background operation is complete, we return immediately.
service/src/java/org/apache/hive/service/cli/CLIService.java