Re: A new message seems missing a punctuation

On Mon, Feb 19, 2024 at 11:42 AM Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
>
> On Mon, Feb 19, 2024 at 11:04 AM Kyotaro Horiguchi
> <horikyota(dot)ntt(at)gmail(dot)com> wrote:
> > Or I thought the values could be moved to DETAILS: line.
>
> Yeah, I think that's likely to be the right approach here. The details
> aren't too clear to me.
>
> Does the primary error message really need to say "could not sync
> slot"? If it will be obvious from context that we were trying to sync
> a slot, then it would be fine to just say "ERROR: remote slot precedes
> local slot".
>

As this is a LOG message, I feel one may need some more information on
the context but it is not mandatory.

> But I also don't quite understand what problem this is trying to
> report. Is this slot-syncing code running on the primary or the
> standby? If it's running on the primary, then surely it's expected
> that the remote slot will precede the local one. And if it's running
> on the standby, then the comments in
> update_and_persist_local_synced_slot about waiting for the remote side
> to catch up seem quite confusing, because surely we're chasing the
> primary and not the other way around?
>

The local's restart_lsn could be ahead of than primary's for the very
first sync when the WAL corresponding to the remote's restart_lsn is
not available on standby (say due to a different wal related settings
the required WAL has been removed when we first time tried to sync the
slot). For more details, you can refer to comments atop slotsync.c
starting from "If the WAL corresponding to the remote's restart_lsn
..."

> But if we ignore all of that, then we could just do this:
>
> ERROR: could not sync slot information as remote slot precedes local slot
> DETAIL: Remote slot has LSN %X/%X and catalog xmin %u, but remote slot
> has LSN %X/%X and catalog xmin %u.
>

This looks good to me but instead of ERROR here we want to use LOG.

--
With Regards,
Amit Kapila.