Re: Stable sort?

redhog wrote:
> Is sorting in PostgreSQL stable over subqueries, that is, is
>
> select * from (select * from A order by x) as B order by y;
>
> equivalent with
>
> select * from A order by y, x;

Seems as easy to try as to guess.

If I did this query right, it seems not.

select * from (select random()>0.5 as a, random()>0.5 as b from generate_series(1,10) order by a) as x order by b;
 a | b
---+---
 f | t
 f | f
 f | f
 f | f
 f | t
 f | f
 t | t
 t | t
 t | t
 t | f
(10 rows)

OTOH, HEY, why isn't that result ordered by 'b' instead of by 'a' (or am I misreading my query or the results)?