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.
