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

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От 德哥
Тема Re:Re: BUG #17036: generated column cann't modifyed auto when update
Дата
Msg-id 23824c32.12e8.179ab97fa8a.Coremail.digoal@126.com
обсуждение исходный текст
Ответ на Re: BUG #17036: generated column cann't modifyed auto when update  ("David G. Johnston" <david.g.johnston@gmail.com>)
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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); 

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


postgres=# select * from t1; 
 id | c1 | info |          crt_time          |          mod_time          
----+----+------+----------------------------+----------------------------
  1 |  1 | test | 2021-05-27 10:10:16.190408 | 2021-05-27 10:10:16.190408
(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 10:10:16.190408 | 2021-05-27 10:10:16.190408
(1 row)

postgres=# update t1 set info='abcd' where id=1;
UPDATE 1
postgres=# select * from t1;
 id | c1 | info |          crt_time          |          mod_time          
----+----+------+----------------------------+----------------------------
  1 |  1 | abcd | 2021-05-27 10:10:16.190408 | 2021-05-27 10:10:16.190408
(1 row)

```




--公益是一辈子的事,I'm Digoal,Just Do It.


在 2021-05-26 20:25:00，"David G. Johnston" <david.g.johnston@gmail.com> 写道：

On Wednesday, May 26, 2021, PG Bug reporting form <noreply@postgresql.org> wrote:
The following bug has been logged on the website:

Bug reference:      17036
Logged by:          Zhou Digoal
Email address:      digoal@126.com
PostgreSQL version: 14beta1
Operating system:   CentOS 7.7 x64
Description:       

postgres=> create or replace function im_now () returns timestamptz as $$   

                                                  select CURRENT_TIMESTAMP;


                   $$ language sql strict immutable;
CREATE FUNCTION

why mod_time cann't updated automatic?


Because that isn’t how this thing works...the lie you told it about being immutable is a dead giveaway,

David J.
 

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