Re: relfrozenxid may disagree with row XIDs after 1ccc1e05ae

Hi,

On Thu, May 23, 2024 at 12:57 AM Melanie Plageman <melanieplageman(at)gmail(dot)com>
wrote:

> One option is to add the logic in fix_hang_15.patch to master as well
> (always remove tuples older than OldestXmin). This addresses your
> concern about gaining confidence in a single solution.
>
> However, I can see how removing more tuples could be concerning. In
> the case that the horizon moves backwards because of a standby
> reconnecting, I think the worst case is that removing that tuple
> causes a recovery conflict on the standby (depending on the value of
> max_standby_streaming_delay et al).
>

I'm confused about this part. The comment above OldestXmin says:
/*
* OldestXmin is the Xid below which tuples deleted by any xact (that
* committed) should be considered DEAD, not just RECENTLY_DEAD.
*/
With the fix_hang_15 patch, why is there a risk here when we use Oldestxmin
to judge whether a tuple could be moved?

I think the keypoint is: OldestXmin and VisTest, which one is more accurate
when we judge to remove the tuple.

--
Regards
Bowen Shi