Feedback-ID: i0fe9450f:Fastmail
Date: Fri, 10 Apr 2026 16:56:33 +0900
From: Michael Paquier <michael@paquier.xyz>
To: Chao Li <li.evan.chao@gmail.com>
Cc: PostgreSQL-development <pgsql-hackers@postgresql.org>
Subject: Re: Fix pgstat_database.c to honor passed database OIDs
Message-ID: <aditMVNDceHtvYj4@paquier.xyz>
References: <ABBD5026-506F-4006-A569-28F72C188693@gmail.com>
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On Fri, Apr 10, 2026 at 03:12:41PM +0900, Michael Paquier wrote:
> If we decide to expand pgstat_reset() in other contexts in the
> back-branches, we'd be silently trapped as well.
>=20
> The connect and disconnect calls are less critical, perhaps we could
> remove the argument altogether, but I cannot get excited about that
> either as some extensions may rely on these as currently designed.
>=20
> I cannot look at that today, will do so later..

-    dbref =3D pgstat_get_entry_ref_locked(PGSTAT_KIND_DATABASE, MyDatabase=
Id, InvalidOid,
+    if (!OidIsValid(dboid))
+        return;
+
+    dbref =3D pgstat_get_entry_ref_locked(PGSTAT_KIND_DATABASE, dboid, Inv=
alidOid,
                                         false);

This bypass of an invalid database OID is actually incorrect in the
patch.  There is a stats entry with a database OID of 0, documented as
such in [1] for shared objects.  There is one test in the main
regression test suite that triggers this case:
SELECT pg_stat_reset_single_table_counters('pg_shdescription'::regclass);

The short answer is to remove this check based on OidIsValid(), and
allow the timestamp be reset for this entry of 0 rather than ignore
the update.

[1]: https://www.postgresql.org/docs/devel/monitoring-stats.html#MONITORING=
-PG-STAT-DATABASE-VIEW
--
Michael

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