Order indexes: used or not?

Dear all,

given a table definition and (explained) SQL query as follows:

CREATE TABLE foo (x INT,y INT); INSERT INTO foo VALUES (3,1), (2,2), (1,3); ALTER TABLE foo SET READ ONLY; CREATE ORDERED INDEX foo_x ON foo(x);

EXPLAIN SELECT * FROM foo ORDER BY x;

In the EXPLAIN output, am I supposed to see that the order index is indeed used? I currently do see an algebra.sort operation, of course, but do not see any reference to the foo_x index. I had expected to find an bat.getorderidx operation in the MAL program.

Can anyone shed light on this? I'd be grateful.

Cheers,

—Torsten