Re: collect_corrupt_items_vacuum.patch

Hi, Alexander!

On Tue, Nov 7, 2023 at 3:00 PM Alexander Lakhin <exclusion@gmail.com> wrote:
>
> 07.11.2023 14:38, Alexander Korotkov wrote:
> > Hi, Alexander.
> >
> > On Tue, Nov 7, 2023 at 1:00 PM Alexander Lakhin <exclusion@gmail.com> wrote:
> >> It looks like the v2 patch doesn't fix the original issue. Maybe I miss
> >> something, but with the patch applied, I see the failure immediately,
> >> though without the patch several iterations are needed to get it.
> >
> > That's a bug in the patch.  Thank you for cathing it.  It should start
> > calculation from latestCompletedXid + 1, not InvalidTransactionId.
> > Please, check the revised patch.
>
> Thanks for looking at this!
> Unfortunately, I still see the failure with the v3, but not on a first
> iteration:
> ...
> iteration 316
> Error condition in psql-8.log:
> create table vacuum_test as select 42 i;
> vacuum (disable_page_skipping) vacuum_test;
> select * from pg_check_visible('vacuum_test');
>   t_ctid
> --------
>   (0,1)
> (1 row)
>
> (I've double-checked that the patch is applied and get_strict_xid_horizon()
> is called.)

I managed to reproduce this on a Linux VM.  This problem should arise
because in extension I don't have access to ProcArrayStruct.  So, my
code is iterating the whole PGPROC's array.  I reimplemented the new
horizon calculation function in the core with usage of
ProcArrayStruct.  Now it doesn't fall for me.  Please, recheck.

------
Regards,
Alexander Korotkov