Re: [PoC] pg_upgrade: allow to upgrade publisher node

Hi Kuroda-san. Here are my review comments for patch v36-0002.

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doc/src/sgml/ref/pgupgrade.sgml

1.
Configure the servers for log shipping. (You do not need to run
<function>pg_backup_start()</function> and
<function>pg_backup_stop()</function>
or take a file system backup as the standbys are still synchronized
- with the primary.) Replication slots are not copied and must
- be recreated.
+ with the primary.) Only logical slots on the primary are copied to the
+ new standby, and other other slots on the old standby must be recreated
+ as they are not copied.
</para>

IMO this text still needs some minor changes like shown below, Anyway,
there is a typo: /other other/

SUGGESTION
Only logical slots on the primary are copied to the new standby, but
other slots on the old standby are not copied so must be recreated
manually.

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src/bin/pg_upgrade/server.c

2.
+ *
+ * Use max_slot_wal_keep_size as -1 to prevent the WAL removal by the
+ * checkpointer process. If WALs required by logical replication slots are
+ * removed, the slots are unusable. The setting ensures that such WAL
+ * records have remained so that invalidation of slots would be avoided
+ * during the upgrade.

The comment already explained the reason for the setting is to prevent
removing the needed WAL records, so I felt there is no need for the
last sentence to repeat the same information.

BEFORE
The setting ensures that such WAL records have remained so that
invalidation of slots would be avoided during the upgrade.

SUGGESTION
This setting prevents the invalidation of slots during the upgrade.

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Kind Regards,
Peter Smith.
Fujitsu Australia