From: Chao Li <li.evan.chao@gmail.com>
Message-Id: <0777DBAC-9348-423A-AB51-5AAFDA445B95@gmail.com>
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Subject: Re: Fix a server crash problem from pg_get_database_ddl
Date: Mon, 27 Apr 2026 10:02:59 +0800
In-Reply-To: <13310e0b-e2b0-45a2-873d-e2b51a8ea3b4@dunslane.net>
Cc: SATYANARAYANA NARLAPURAM <satyanarlapuram@gmail.com>,
 Tom Lane <tgl@sss.pgh.pa.us>,
 PostgreSQL-development <pgsql-hackers@postgresql.org>,
 Japin Li <japinli@hotmail.com>
To: Andrew Dunstan <andrew@dunslane.net>
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> On Apr 26, 2026, at 22:50, Andrew Dunstan <andrew@dunslane.net> wrote:
>=20
>=20
> On 2026-04-23 Th 2:47 AM, SATYANARAYANA NARLAPURAM wrote:
>>=20
>>=20
>> Thanks for printing out that. Yes, they are similar.
>>=20
>> I agree with what Tom said in [2]:
>> ```
>> This is not a bug. This is a superuser intentionally breaking
>> the system by corrupting the catalogs. There are any number
>> of ways to cause trouble with ill-advised manual updates to a
>> catalog table. Try, eg, "DELETE FROM pg_proc" (... but not in
>> a database you care about).
>> ```
>>=20
>> So, let me take back this patch.
>>=20
>> [2] =
https://www.postgresql.org/message-id/1538113.1768921841@sss.pgh.pa.us=20=

>> In this case, it is a very corner case but not something superuser =
intentionally breaks.
>> For example, a concurrent tablespace drop + database ddl to assign a =
different tablespace or default.
>> We aren't acquiring Access Share lock on the DB in this function =
(intentional) so it is a good practice
>> to do the null checks. Of course, it makes more sense to add this =
comment while doing a code review.
>> I will let Tom and others chime in with their thoughts on fixing =
this.
>>=20
>> Attached an injection point test to show the race. Not intended to =
commit.
>>=20
>>=20
>=20
> I agree if there's a race condition we should protect against it. I =
don't much like the idea of silently ignoring it, though. Raising an =
error seems more like the right thing to do.
>=20
> cheers
>=20
> andrew
> --
> Andrew Dunstan
> EDB: https://www.enterprisedb.com
>=20

The v1 patch raises an error when the tablespace name is NULL.

PFA v2: removed hint from the error message, because I now consider the =
hint might not be necessary.

Best regards,
--
Chao Li (Evan)
HighGo Software Co., Ltd.
https://www.highgo.com/


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