Re: State of pg_createsubscriber

On 18.06.24 05:59, Amit Kapila wrote:
>> 1. After promotion, the pre-existing replication objects should be
>> removed (either optionally or always), otherwise, it can lead to a new
>> subscriber not being able to restart or getting some unwarranted data.
>> [1][2].
>>
>> 2. Retaining synced slots on new subscribers can lead to unnecessary
>> WAL retention and dead rows [3].
>>
>> 3. We need to consider whether some of the messages displayed in
>> --dry-run mode are useful or not [4].
>>
> 
> The recent commits should silence BF failures and resolve point number
> 2. But we haven't done anything yet for 1 and 3. For 3, we have a
> patch in email [1] (v3-0005-Avoid*) which can be reviewed and
> committed but point number 1 needs discussion. Apart from that
> somewhat related to point 1, Kuroda-San has raised a point in an email
> [2] for replication slots. Shlok has presented a case in this thread
> [3] where the problem due to point 1 can cause ERRORs or can cause
> data inconsistency.
> 
> Now, the easiest way out here is that we accept the issues with the
> pre-existing subscriptions and replication slots cases and just
> document them for now with the intention to work on those in the next
> version. OTOH, if there are no major challenges, we can try to
> implement a patch for them as well as see how it goes.

This has gotten much too confusing to keep track of.

I suggest, if anyone has anything they want considered for 
pg_createsubscriber for PG17 at this point, they start a new thread, one 
for each topic, ideally with a subject like "pg_createsubscriber: 
Improve this thing", provide a self-contained description of the issue, 
and include a patch if one is available.