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From: Zhenwei Shang <[email protected]>
To: Chao Li <[email protected]>
Cc: PostgreSQL Hackers <[email protected]>
Subject: Re: Fix wrong error message from pg_get_tablespace_ddl()
Date: Fri, 8 May 2026 17:16:21 +0800
Message-ID: <CABv9HU=rQeED3fiTA1Boyf2nLjX6TG=_18X8OM3LDZUqGO8LfA@mail.gmail.com> (raw)
In-Reply-To: <[email protected]>
References: <[email protected]>

Chao Li <[email protected]> 于2026年5月8日周五 16:15写道：

> Hi,
>
> I started testing pg_get_tablespace_ddl(). While tracing
> pg_get_tablespace_ddl_internal(), I noticed that this error report must be
> wrong:
> ```
>         /* User must have SELECT privilege on pg_tablespace. */
>         if (pg_class_aclcheck(TableSpaceRelationId, GetUserId(),
> ACL_SELECT) != ACLCHECK_OK)
>         {
>                 ReleaseSysCache(tuple);
>                 aclcheck_error(ACLCHECK_NO_PRIV, OBJECT_TABLESPACE,
> spcname);
>         }
> ```
>
> The comment clearly says that SELECT privilege on pg_tablespace is
> required, but the error is reported against the target tablespace instead.
>
> This is easy to reproduce:
> ```
> evantest=# set allow_in_place_tablespaces = true;
> SET
> evantest=# create role r1;
> CREATE ROLE
> evantest=# create tablespace ts1 location '';
> CREATE TABLESPACE
> evantest=# revoke select on pg_tablespace from r1;
> REVOKE
> evantest=# set role r1;
> SET
> evantest=> select * from pg_get_tablespace_ddl('ts1');
> ERROR:  permission denied for tablespace ts1
> ```
>
> Attached is a simple one-line fix. Attached is a simple one-line fix. I
> did not add a new test, as we usually try to avoid extending the test time
> for such a small fix. With the fix, the error message now looks like:
> ```
> evantest=> select * from pg_get_tablespace_ddl('ts1');
> ERROR:  permission denied for table pg_tablespace
> ```
>
> Oops, I was one of the reviewers of the original patch. Sorry for not
> finding this during review.
>
> Best regards,
> --
> Chao Li (Evan)
> HighGo Software Co., Ltd.
> https://www.highgo.com/
>
>
Thanks for the patch. I can reproduce the problem and the fix looks correct
to me.

Regards,
Zhenwei Shang

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