sql: UPDATE with RETURNING should be able to return other columns

[RaduBerinde]

When doing an UPDATE, we should be able to use RETURNING on other columns:

DROP TABLE IF EXISTS t;
CREATE TABLE t (a INT, b INT);

INSERT INTO t VALUES (1);
UPDATE t SET b = 2 RETURNING a;

We get an error: pq: qualified name "a" not found.
Related to this, RETURNING * should return all columns in the table, not just the updated ones.

This works in pg;

UPDATE t SET b = 2 RETURNING a;
 a 

---
 1
(1 row)

UPDATE 1
UPDATE t SET b = 2 RETURNING *;
 a | b 
---+---
 1 | 2
(1 row)

Also related, there is this testcase for INSERT:

statement error pq: qualified name "b" not found
INSERT INTO return (a) VALUES (default) RETURNING b

I am not sure if this should work or not (I haven't checked what pg does).

@mjibson

[RaduBerinde]

Oops, this is a duplicate of #4368