Horton

RE: pg_upgrade and logical replication

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

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From: "Hayato Kuroda (Fujitsu)" <kuroda.hayato@fujitsu.com>
To: 'Michael Paquier' <michael@paquier.xyz>, vignesh C <vignesh21@gmail.com>
Cc: Julien Rouhaud <rjuju123@gmail.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>, Amit Kapila <amit.kapila16@gmail.com>
Date: 2023-09-25T05:35:18Z
Lists: pgsql-hackers 
Dear Michael,

> I'd like to propose a check
> for IsBinaryUpgrade into ApplyLauncherRegister() instead as it makes
> no real sense to start apply workers in this context.  That would be
> equivalent to max_logical_replication_workers = 0.

Personally, I prefer to change max_logical_replication_workers. Mainly there are
two reasons:

1. Your approach must be back-patched to older versions which support logical
   replication feature, but the oldest one (PG10) has already been unsupported.
   We should not modify such a branch.
2. Also, "max_logical_replication_workers = 0" approach would be consistent
   with what we are doing now and for upgrade of publisher patch.
   Please see the previous discussion [1].

[1]: https://www.postgresql.org/message-id/CAA4eK1%2BWBphnmvMpjrxceymzuoMuyV2_pMGaJq-zNODiJqAa7Q%40mail.gmail.com

Best Regards,
Hayato Kuroda
FUJITSU LIMITED

Commits

  1. pg_upgrade: Retrieve subscription count more efficiently.

  2. Fix random failure in 004_subscription.

  3. Fix 004_subscription.pl to allow its usage in --link mode.

  4. Allow upgrades to preserve the full subscription's state.

  5. Prevent startup of logical replication launcher during pg_upgrade