Evaluation of secondary sort key.

This seems like a place where there is room for improvement.

2011-04-09 15:18:08.016 testdb=# select id from test1 where id < 3 order 
by id; id
----  1  2
(2 rows)

Time: 0.328 ms
2011-04-09 15:18:11.936 testdb=# CREATE or Replace FUNCTION testsort(id 
integer) returns integer as $$ BEGIN perform pg_sleep(id); return id; 
END; $$ language plpgsql;
CREATE FUNCTION
Time: 12.349 ms
2011-04-09 15:18:22.138 testdb=# select id from test1 where id < 3 order 
by id,testsort(id); id
----  1  2
(2 rows)

Time: 3001.896 ms

It seems strange that there is a need to evaluate testsort(id) at all in 
this case.

-- 
Jesper