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

On Fri, Oct 27, 2017 at 3:13 AM, Michael Paquier
<michael.paquier@gmail.com> wrote:
> On Thu, Oct 26, 2017 at 3:05 AM, Kyotaro HORIGUCHI
> <horiguchi.kyotaro@lab.ntt.co.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.

Yeah, I am still on track with this idea. Splitting the flush LSN and
the restart LSN properly can allow for better handling on clients. For
now I am moving this patch to the next CF.
-- 
Michael