Re: Slot's restart_lsn may point to removed WAL segment after hard restart unexpectedly

On Tue, Jun 3, 2025 at 6:51 PM Alexander Korotkov <aekorotkov(at)gmail(dot)com> wrote:
>
> >
> > As per my understanding, for logical slots, effective_xmin is only set
> > during the initial copy phase (or say if one has to export a
> > snapshot), after that, its value won't change. Please read the
> > comments in CreateInitDecodingContext() where we set its value. If you
> > still have questions about it, we can discuss further.
>
> OK, thank you for the clarification. I've read the comments in
> CreateInitDecodingContext() as you suggested. All of above makes me
> think *_xmin fields are handled properly.
>

Yes, they handled properly for logical slots, but there is no similar
safety mechanism for physical slots.

One minor comment:
+
+ /* Latest restart_lsn that has been flushed to disk. For persistent slots
+ * the flushed LSN should be taken into account when calculating the oldest

This doesn't follow our practice for multi-line comments.

--
With Regards,
Amit Kapila.