Horton

Re: archive modules

Nathan Bossart <nathandbossart@gmail.com>

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From: Nathan Bossart <nathandbossart@gmail.com>
To: Peter Eisentraut <peter.eisentraut@enterprisedb.com>
Cc: Tom Lane <tgl@sss.pgh.pa.us>, Benoit Lobréau <benoit.lobreau@gmail.com>, Alvaro Herrera <alvherre@alvh.no-ip.org>, Robert Haas <robertmhaas@gmail.com>, "Bossart, Nathan" <bossartn@amazon.com>, David Steele <david@pgmasters.net>, Fujii Masao <masao.fujii@oss.nttdata.com>, "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>, Michael Paquier <michael@paquier.xyz>, Magnus Hagander <magnus@hagander.net>, Stephen Frost <sfrost@snowman.net>
Date: 2022-09-14T20:03:05Z
Lists: pgsql-hackers 
On Wed, Sep 14, 2022 at 09:33:46PM +0200, Peter Eisentraut wrote:
> Another question on this feature: Currently, if archive_library is set,
> archive_command is ignored.  I think if both are set, it should be an error.
> Compare for example what happens if you set multiple recovery_target_xxx
> settings.  I don't think silently turning off one setting by setting another
> is a good behavior.

I originally did it this way, but changed it based on this feedback [0].  I
have no problem with the general idea, but the recovery_target_* logic does
have the following note:

	 * XXX this code is broken by design.  Throwing an error from a GUC assign
	 * hook breaks fundamental assumptions of guc.c.  So long as all the variables
	 * for which this can happen are PGC_POSTMASTER, the consequences are limited,
	 * since we'd just abort postmaster startup anyway.  Nonetheless it's likely
	 * that we have odd behaviors such as unexpected GUC ordering dependencies.

[0] https://postgr.es/m/CA%2BTgmoaf4Y7_U%2B_W%2BSg5DoAta_FMssr%3D52mx7-_tJnfaD1VubQ%40mail.gmail.com

-- 
Nathan Bossart
Amazon Web Services: https://aws.amazon.com

Commits

  1. Disallow setting archive_library and archive_command at the same time

  2. Restore archive_command documentation

  3. Doc: improve explanation of when custom GUCs appear in pg_settings.

  4. doc: Add note about re-archiving of same WAL files in docs.

  5. In basic_archive tests, insist on wal_level='replica'.

  6. Allow archiving via loadable modules.

  7. Move the code to archive files via the shell to a separate file.