private void walkTree(Collection<Node> rootOps) throws SemanticException {
    if (rootOps.isEmpty()) {
      return;
    }

    SemanticDispatcher disp = new DefaultRuleDispatcher(new OperatorHealthCheckerProcessor(), new HashMap<>(), null);
    SemanticGraphWalker ogw = new DefaultGraphWalker(disp);

    HashMap<Node, Object> nodeOutput = new HashMap<Node, Object>();
    ogw.startWalking(rootOps, nodeOutput);
  }
Checks some operator quality rules.

Checks whenever operator ids are not reused.
Checks some level of expression/schema consistency
Some sanity checks on SelectOperators
ql/src/java/org/apache/hadoop/hive/ql/hooks/OperatorHealthCheckerHook.java