Re: Fix tuple deformation with virtual generated NOT NULL columns - Mailing list pgsql-hackers

> On Jun 4, 2026, at 17:32, cca5507 <cca5507@qq.com> wrote:
>
>> While testing "Optimize tuple deformation”, I found a bug:
>> ```
>> evantest=# create table t (a int not null,
>> evantest(# g int generated always as (a+1) virtual not null,
>> evantest(# b int not null);
>> CREATE TABLE
>> evantest=# insert into t (a, b) values (10, 20);
>> INSERT 0 1
>> evantest=# select a, g, b from t;
>>  a  | g  | b
>> ----+----+---
>>  10 | 11 | 0
>> (1 row)
>> ```
>
> Nice catch! I can reproduce this bug on master. Some comments about the fix:
>
> I find that a virtual generated column is stored as a null in heap tuple, so I think
> we should stop setting 'attcacheoff' when we see a virtual generated column in
> TupleDescFinalize(), or we will set wrong 'attcacheoff' value. But it seems that
> we don't use these wrong value because we can only use 'attcacheoff' up until
> the first NULL.
>
> --
> Regards,
> ChangAo Chen

Hi ChangAo,

Thanks for your review. Please see v2 that addressed your comment.

Best regards,
--
Chao Li (Evan)
HighGo Software Co., Ltd.
https://www.highgo.com/