Re: Synchronizing slots from primary to standby

On Thu, Apr 11, 2024 at 5:04 PM Zhijie Hou (Fujitsu)
<houzj.fnst@fujitsu.com> wrote:
>
> On Thursday, April 11, 2024 12:11 PM Amit Kapila <amit.kapila16@gmail.com> wrote:
>
> >
> > 2.
> > - if (remote_slot->restart_lsn < slot->data.restart_lsn)
> > + if (remote_slot->confirmed_lsn < slot->data.confirmed_flush)
> >   elog(ERROR,
> >   "cannot synchronize local slot \"%s\" LSN(%X/%X)"
> >
> > Can we be more specific in this message? How about splitting it into
> > error_message as "cannot synchronize local slot \"%s\"" and then errdetail as
> > "Local slot's start streaming location LSN(%X/%X) is ahead of remote slot's
> > LSN(%X/%X)"?
>
> Your version looks better. Since the above two messages all have errdetail, I
> used the style of ereport(ERROR, errmsg_internal(), errdetail_internal()... in
> the patch which is equal to the elog(ERROR but has an additional detail message.
>

makes sense.

> Here is V5 patch set.
>

I think we should move the check to not advance slot when one of
remote_slot's restart_lsn or catalog_xmin is lesser than the local
slot inside update_local_synced_slot() as we want to prevent updating
slot in those cases even during slot synchronization.

--
With Regards,
Amit Kapila.