@Override
public void visit(LOForEach foreach) throws FrontendException {
foreach.resetSchema();
OperatorPlan innerPlan = foreach.getInnerPlan();
PlanWalker newWalker = currentWalker.spawnChildWalker(innerPlan);
pushWalker(newWalker);
currentWalker.walk(this);
popWalker();
validate(foreach.getSchema());
}