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Allow resetting unknown custom GUCs with reserved prefixes.

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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
This commit is contained in:
Nathan Bossart
2025-08-01 16:52:11 -05:00
parent 60121890f7
commit 7b9674a8b1
5 changed files with 64 additions and 5 deletions
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22
contrib/auto_explain/sql/alter_reset.sql Normal file
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--
-- This tests resetting unknown custom GUCs with reserved prefixes. There's
-- nothing specific to auto_explain; this is just a convenient place to put
-- this test.
--
SELECT current_database() AS datname \gset
CREATE ROLE regress_ae_role;
ALTER DATABASE :"datname" SET auto_explain.bogus = 1;
ALTER ROLE regress_ae_role SET auto_explain.bogus = 1;
ALTER ROLE regress_ae_role IN DATABASE :"datname" SET auto_explain.bogus = 1;
ALTER SYSTEM SET auto_explain.bogus = 1;
LOAD 'auto_explain';
ALTER DATABASE :"datname" RESET auto_explain.bogus;
ALTER ROLE regress_ae_role RESET auto_explain.bogus;
ALTER ROLE regress_ae_role IN DATABASE :"datname" RESET auto_explain.bogus;
ALTER SYSTEM RESET auto_explain.bogus;
DROP ROLE regress_ae_role;