Re: [BUGS] Bug in Physical Replication Slots (at least 9.5)?

On Thu, Oct 26, 2017 at 3:05 AM, Kyotaro HORIGUCHI
<horiguchi(dot)kyotaro(at)lab(dot)ntt(dot)co(dot)jp> wrote:
> The largest obstacle to do that is that walreceiver is not
> utterly concerned to record internals. In other words, it doesn't
> know what a record is. Teaching that introduces much complexity
> and the complexity slows down the walreceiver.
>
> Addition to that, this "problem" occurs also on replication
> without a slot. The latest patch also help the case.

That's why replication slots have been introduced to begin with. The
WAL receiver gives no guarantee that a segment will be retained or not
based on the beginning of a record. That's sad that the WAL receiver
does not track properly restart LSN and instead just uses the flush
LSN. I am beginning to think that a new message type used to report
the restart LSN when a replication slot is in use would just be a
better and more stable solution. I haven't looked at the
implementation details yet though.
--
Michael