From: Nathan Bossart <nathan@postgresql.org>
To: pgsql-committers@lists.postgresql.org
Subject: pgsql: Allow resetting unknown custom GUCs with reserved prefixes.
Date: Fri, 01 Aug 2025 21:55:42 +0000
Message-ID: <E1uhxj3-000Fyi-2d@gemulon.postgresql.org> (raw)
Allow resetting unknown custom GUCs with reserved prefixes.
Currently, ALTER DATABASE/ROLE/SYSTEM RESET [ALL] with an unknown
custom GUC with a prefix reserved by MarkGUCPrefixReserved() errors
(unless a superuser runs a RESET ALL variant). This is problematic
for cases such as an extension library upgrade that removes a GUC.
To fix, simply make sure the relevant code paths explicitly allow
it. Note that we require superuser or privileges on the parameter
to reset it. This is perhaps a bit more restrictive than is
necessary, but it's not clear whether further relaxing the
requirements is safe.
Oversight in commit 88103567cb. The ALTER SYSTEM fix is dependent
on commit 2d870b4aef, which first appeared in v17. Unfortunately,
back-patching that commit would introduce ABI breakage, and while
that breakage seems unlikely to bother anyone, it doesn't seem
worth the risk. Hence, the ALTER SYSTEM part of this commit is
omitted on v15 and v16.
Reported-by: Mert Alev <mert@futo.org>
Reviewed-by: Laurenz Albe <laurenz.albe@cybertec.at>
Discussion: https://postgr.es/m/18964-ba09dea8c98fccd6%40postgresql.org
Backpatch-through: 15
Branch
------
REL_17_STABLE
Details
-------
https://git.postgresql.org/pg/commitdiff/39ff056365e438b530498def7ef18d588129e8e0
Modified Files
--------------
contrib/auto_explain/Makefile | 2 ++
contrib/auto_explain/expected/alter_reset.out | 19 +++++++++++++++++++
contrib/auto_explain/meson.build | 5 +++++
contrib/auto_explain/sql/alter_reset.sql | 22 ++++++++++++++++++++++
src/backend/utils/misc/guc.c | 21 ++++++++++++++++-----
5 files changed, 64 insertions(+), 5 deletions(-)
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To: pgsql-committers@postgresql.org
Cc: nathan@postgresql.org, pgsql-committers@lists.postgresql.org
Subject: Re: pgsql: Allow resetting unknown custom GUCs with reserved prefixes.
In-Reply-To: <E1uhxj3-000Fyi-2d@gemulon.postgresql.org>
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