Re: Synchronizing slots from primary to standby - Mailing list pgsql-hackers

On Thu, Nov 9, 2023 at 9:54 PM shveta malik <shveta.malik@gmail.com> wrote:
>
> PFA v32 patches which has below changes:
Testing with this patch, I see that if the failover enabled slot is
invalidated on the primary, then the corresponding synced slot is not
invalidated on the standby. Instead, I see that it continuously gets
the below error:
" WARNING:  not synchronizing slot sub; synchronization would move it backwards"

In the code, I see that:
        if (remote_slot->restart_lsn < MyReplicationSlot->data.restart_lsn)
        {
            ereport(WARNING,
                    errmsg("not synchronizing slot %s; synchronization
would move"
                           " it backwards", remote_slot->name));

            ReplicationSlotRelease();
            CommitTransactionCommand();
            return;
        }

If the restart_lsn of the remote slot is behind, then the
local_slot_update() function is never called to set the invalidation
status on the local slot. And for invalidated slots, restart_lsn is
always NULL.

regards,
Ajin Cherian
Fujitsu Australia