N1QL:As of now there is no plan seen in explain clause of a query including subqueries

I see expression scan being used for queries having constants like:

explain SELECT p.x FROM {"p":[{"x":11},{"x":12}],"q":"abc","r":null}.p;

but cant find any subqueries on a bucket which show expression scan or any plan information for that subquery.
Example:

explain SELECT custId, id FROM orders WHERE "lunch" IN (SELECT RAW orderlines.productId FROM orders.orderlines);

After discussion with Sitaram, it seems there is no plan produced for subqueries and this can be an improvement.