Re: [HACKERS] make async slave to wait for lsn to be replayed - Mailing list pgsql-hackers

On Fri, Dec 8, 2023 at 11:20 AM Kartyshov Ivan
<i.kartyshov@postgrespro.ru> wrote:
>
> On 2023-11-27 03:08, Alexander Korotkov wrote:
> > I've retried my case with v6 and it doesn't fail anymore.  But I
> > wonder how safe it is to reset xmin within the user-visible function?
> > We have no guarantee that the function is not called inside the
> > complex query.  Then how will the rest of the query work with xmin
> > reset?  Separate utility statement still looks like more safe option
> > for me.
>
> As you mentioned, we can`t guarantee that the function is not called
> inside the complex query, but we can return the xmin after waiting.

Returning xmin back isn't safe.  Especially after potentially long
waiting.  The snapshot could be no longer valid, because the
corresponding tuples could be VACUUM'ed.

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Regards,
Alexander Korotkov