Horton

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

Hayato Kuroda (Fujitsu) <kuroda.hayato@fujitsu.com>

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From: "Hayato Kuroda (Fujitsu)" <kuroda.hayato@fujitsu.com>
To: "'Jonathan S. Katz'" <jkatz@postgresql.org>
Cc: PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>, Julien Rouhaud <rjuju123@gmail.com>, Amit Kapila <amit.kapila16@gmail.com>, vignesh C <vignesh21@gmail.com>
Date: 2023-08-02T03:31:27Z
Lists: pgsql-hackers 
Dear Jonathan,

Thank you for reading the thread!

> Can I take this a step further on the user interface and ask why the
> flag would be "--include-logical-replication-slots" vs. being enabled by
> default?
> 
> Are there reasons why we wouldn't enable this feature by default on
> pg_upgrade, and instead (if need be) have a flag that would be
> "--exclude-logical-replication-slots"? Right now, not having the ability
> to run pg_upgrade with logical replication slots enabled on the
> publisher is a a very big pain point for users, so I would strongly
> recommend against adding friction unless there is a very large challenge
> with such an implementation.

The main reason was that there were no major complaints till now. This decision
followed the related discussion, for upgrading the subscriber [1]. As mentioned
there, current style might have more flexibility. Of course we could change that
if there are more opinions around here.
(I believe that this feature is useful for everyone, but changing the default may
affect others...)

As for the implementation, I did not check so deeply but there is no challenge.
We cannot change the style pg_dump option due to the pg_resetwal ordering issue[2],
but it option is not visible from users. I will check deeper when we want to do...

How do you think?

[1]: https://www.postgresql.org/message-id/CAA4eK1KD-hZ3syruxJA6fK-JtSBzL6etkwToPuTmVkrCvT6ASw%40mail.gmail.com
[2]: https://www.postgresql.org/message-id/TYAPR01MB58668C61A3C6EE82AE436C07F539A%40TYAPR01MB5866.jpnprd01.prod.outlook.com

Best Regards,
Hayato Kuroda
FUJITSU LIMITED

Commits

  1. Fix issues in binary_upgrade_logical_slot_has_caught_up().

  2. Fix a random failure in 003_logical_slots.pl.

  3. Fix a test in 003_logical_slots.

  4. Fix uninitialized slot array access during the upgrade.

  5. Fix the test 003_logical_slots.

  6. Commit b195e6d482 forgot to update meson.build.

  7. Use shorter file names in the upgrade logical slots test.

  8. Migrate logical slots to the new node during an upgrade.

  9. Flush logical slots to disk during a shutdown checkpoint if required.

  10. Prevent possibility of panics during shutdown checkpoint.