@Override
public Iterator<Expression> visitEnter(ScalarFunction node) {
return node.preservesOrder() == OrderPreserving.NO
? Iterators.<Expression>emptyIterator()
: Iterators.singletonIterator(
node.getChildren().get(node.getKeyFormationTraversalIndex()));
}
@Override
public Info visitLeave(ScalarFunction node, List<Info> l) {
if (l.isEmpty()) {
return null;
}
Info info = l.get(0);
// Keep the minimum value between this function and the current value,
// so that we never increase OrderPreserving from NO or YES_IF_LAST.
OrderPreserving orderPreserving =
OrderPreserving.values()[
Math.min(node.preservesOrder().ordinal(), info.orderPreserving.ordinal())];
if (orderPreserving == info.orderPreserving) {
return info;
}
return new Info(info, orderPreserving);
}