Can I DISTINCT by Multiple Columns?

[唐亮]

Hi pigs:
Can I distinct by multiple columns?

For example:
A = load ... as (a1:int, a2:int, a3:int);
B = DISTINCT A;  -- It's OK.


-- But can I distinct by a1 and a2?
C = DISTINCT A.a1, A.a2;  -- It's Not OK


-- And I know I can do it like this:
F = foreach A generate a1, a2;
D = DISTINCT F;

-- But, ...