sql: UPDATE should support RETURNING non-updated columns

[maddyblue]

test=# update table1 set column_b = '' returning column_a;
 column_a
----------
        1
(1 row)

UPDATE 1

[RaduBerinde]

Related:

INSERT INTO t (a) VALUES (1) RETURNING *;

This returns only column a. I think it should return all columns from the table. PG does:

INSERT INTO t (a) VALUES (1) RETURNING *;
 a | b 
---+---
 1 |  
(1 row)

[RaduBerinde]

I wonder if we should just use all visible table columns in returningHelper instead of passing the columns from insert/update.

Edit: never mind, it's not that simple, the rowVals have to match the columns we pass to rh.