Re: Slow catchup of 2PC (twophase) transactions on replica in LR

Hi, here are my review comments for v19-0001.

======
doc/src/sgml/protocol.sgml

nitpick - Now there is >1 option. /The following option is supported:/The
following options are supported:/

======
src/backend/access/transam/twophase.c

TwoPhaseTransactionGid:
nitpick - renamed parameter /gid/gid_res/ to emphasize that this is
returned by reference

~~~

1.
IsTwoPhaseTransactionGidForSubid
+ /* Construct the format GID based on the got xid */
+ TwoPhaseTransactionGid(subid, xid, gid_generated, sizeof(gid));

I think the wrong size is being passed here. It should be the buffer size
-- e.g. sizeof(gid_generated).

~

nitpick - renamed a couple of vars for readability
nitpick - expanded some comments.

======
src/backend/commands/subscriptioncmds.c

2. AlterSubscription
+ /*
+ * slot_name and two_phase cannot be altered
+ * simultaneously. The latter part refers to the pre-set
+ * slot name and tries to modify the slot option, so
+ * changing both does not make sense.
+ */

I had given a v18-0002 nitpick suggestion to re-word all of this comment.
But, as I wrote before [1], that fix belongs here in patch 0001 where the
comment was first added.

======
[1]
https://www.postgresql.org/message-id/CAHut%2BPsqMRS3dcijo5jsTSbgV1-9So-YBC7PH7xg0%2BZ8hA7fDQ%40mail.gmail.com

Kind Regards,
Peter Smith.
Fujitsu Australia