public boolean isUnknown() {
    return Double.isInfinite(getRowCount())
        || Double.isInfinite(getRate())
        || Double.isInfinite(getWindow());
  }
@Test
  public void testUnknownRel() {
    String sql = " select * from ORDER_DETAILS1 ";
    RelNode root = env.parseQuery(sql);
    RelNode unknown = new UnknownRel(root.getCluster(), null, null);
    NodeStats nodeStats =
        unknown
            .metadata(NodeStatsMetadata.class, unknown.getCluster().getMetadataQuery())
            .getNodeStats();
    Assert.assertTrue(nodeStats.isUnknown());
  }