Re: Virtual generated columns

please check attached.

BTW, I was curious about what happens if the replacement expression is
constant, so I tried running the query below.

CREATE TABLE t (a int, b int GENERATED ALWAYS AS (1 + 1));
INSERT INTO t VALUES (1);
INSERT INTO t VALUES (2);

# SELECT t2.a, t2.b FROM t t1 LEFT JOIN t t2 ON FALSE;
a | b
---+---
| 2
| 2
(2 rows)

Is this the expected behavior? I was expecting that t2.b should be
all NULLs.

SELECT t2.a, t2.b FROM t t1 LEFT JOIN t t2 ON FALSE;
should be same as
SELECT t2.a, 2 as b FROM t t1 LEFT JOIN t t2 ON FALSE;
so i think this is expected.