RE: speed up a logical replica setup

Dear Euler,

Thanks for making the follow-up patch! I was looking forward to your updates.
I think this patch set is the solution for the found buildfarm error. However,
there are remained claims raised by others. You should reply what you think for
them. At least:

1) There are some misleading messages [1]. I think v3-0005 patch set can solve
the issue.
2) pg_createsubscriber may fail If the primary has subscriptions [2]. IIUC
possible approaches are A)"keep subscriptions disabled at the end",
B)"by default drop the pre-existing subscriptions",
C) "do nothing, just document the risk".

> Before sending this email I realized that I did nothing about physical
> replication slots on the standby. I think we should also remove them too
> unconditionally.

I also considered around here, but it might be difficult to predict the
expectation by users. Can we surely say that it's not intentional one? Regarding
the failover slot, it is OK because that's meaningful only on the standby,
but not sure other slots. I personally think we can keep current spec, but
how do other think?

Below parts are comments for each patches.

0001
Basically LGTM. I was bit confused because the default timeout is not set, but
it seemed to follow the suggestion by Tomas [3].

0002
If you want to improve the commit message, please add that sync_replication_slots
is disabled during the conversion.

0003
Confirmed it followed the discussion [4].

0004
Basically LGTM.

Other minor comments are included by the attached diff file. It contains changes
to follow conventions and pgindent/pgperltidy.

[1]: https://www.postgresql.org/message-id/CAA4eK1J2fAvsJ2HihbWJ_GxETd6sdqSMrZdCVJEutRZRpm1MEQ%40mail.gmail.com
[2]: https://www.postgresql.org/message-id/CANhcyEWvimA1-f6hSrA%3D9qkfR5SonFb56b36M%2B%2BvT%3DLiFj%3D76g%40mail.gmail.com
[3]: https://www.postgresql.org/message-id/5d5dd4cd-6359-4109-88e8-c8e13035ae16%40enterprisedb.com
[4]: https://www.postgresql.org/message-id/CAA4eK1LZxYxcbeiOn3Q5hjXVtZKhJWj-fQtndAeTCvZrPev8BA%40mail.gmail.com

Best Regards,
Hayato Kuroda
FUJITSU LIMITED
https://www.fujitsu.com/global/