Re:Re: BUG #17036: generated column cann't modifyed auto when update

When i use the im_now(float8 default random()) dynamic parameter, it also not work for PG 14 within generated column.

```

postgres=# drop function im_now(anyelement) ;

DROP FUNCTION

postgres=# drop function im_now ;

DROP FUNCTION

postgres=# drop table t1;

DROP TABLE

postgres=#

postgres=# create or replace function im_now (float8 default random()) returns timestamptz as $$

postgres$# select now();

postgres$# $$ language sql strict immutable;

CREATE FUNCTION

postgres=#

postgres=# create table t1 (id int primary key, c1 int, info text, crt_time timestamp,

postgres(# mod_time timestamp GENERATED ALWAYS AS (im_now()) stored);

CREATE TABLE

postgres=# insert into t1 (id, c1, info, crt_time) values (1,1,'test', now());

INSERT 0 1

postgres=#

postgres=# select * from t1;

id | c1 | info | crt_time | mod_time

----+----+------+----------------------------+----------------------------

1 | 1 | test | 2021-05-27 10:43:32.278616 | 2021-05-27 10:43:32.278616

(1 row)

postgres=# update t1 set info='a' where id=1;

UPDATE 1

postgres=# select * from t1;

id | c1 | info | crt_time | mod_time

----+----+------+----------------------------+----------------------------

1 | 1 | a | 2021-05-27 10:43:32.278616 | 2021-05-27 10:43:32.278616

(1 row)

postgres=# update t1 set info='a' where id=1;

UPDATE 1

postgres=# select * from t1;

id | c1 | info | crt_time | mod_time

----+----+------+----------------------------+----------------------------

1 | 1 | a | 2021-05-27 10:43:32.278616 | 2021-05-27 10:43:32.278616

(1 row)

postgres=# select im_now();

im_now

-------------------------------

2021-05-27 10:44:03.749108+08

(1 row)

postgres=# select im_now();

im_now

-------------------------------

2021-05-27 10:44:04.509058+08

(1 row)

postgres=# select im_now();

im_now

-------------------------------

2021-05-27 10:44:06.781393+08

(1 row)

```

--

公益是一辈子的事,I'm Digoal,Just Do It.

在 2021-05-27 10:33:40，"David G. Johnston" <david(dot)g(dot)johnston(at)gmail(dot)com> 写道：

On Wednesday, May 26, 2021, 德哥 <digoal(at)126(dot)com> wrote:

And immutable function is stable when parameter not change, when parameter changed , the immutable function will recall and recompute.
but in PG 13 and PG 14 , it is also wrong.

```
create or replace function im_now (anyelement) returns timestamptz as $$
select now();
$$ language sql strict immutable;

create table t1 (id int primary key, c1 int, info text, crt_time timestamp,
mod_time timestamp GENERATED ALWAYS AS (im_now(t1)) stored);

This seems to be related to this already reported bug (the similar one I noted in my other reply).

https://www.postgresql.org/message-id/CAM_DEiWR2DPT6U4xb-Ehigozzd3n3G37ZB1%2B867zbsEVtYoJww%40mail.gmail.com

David J.