Horton

Re: archive modules

Nathan Bossart <nathandbossart@gmail.com>

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From: Nathan Bossart <nathandbossart@gmail.com>
To: talk to ben <blo.talkto@gmail.com>
Cc: 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: 2022-07-06T16:41:05Z
Lists: pgsql-hackers 
On Wed, Jul 06, 2022 at 06:21:24PM +0200, talk to ben wrote:
> I am not sure why, but I can't find "basic_archive.archive_directory" in
> pg_settings the same way I would find for example :
> "pg_stat_statements.max".
> 
> [local]:5656 benoit@postgres=# SELECT count(*) FROM pg_settings WHERE name
> = 'basic_archive.archive_directory';
>  count
> -------
>      0
> (1 row)
> 
> show can find it if I use the complete name but tab completion can't find
> the guc:
> 
> [local]:5656 benoit@postgres=# show basic_archive.archive_directory;
>  basic_archive.archive_directory
> ---------------------------------
>  /home/benoit/tmp/tmp/archives
> (1 row)

I think the reason is that only the archiver process loads the library, so
the GUC isn't registered at startup like you'd normally see with
shared_preload_libraries.  IIUC the server will still create a placeholder
GUC during startup for custom parameters, which is why it shows up for SHOW
commands.

-- 
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.