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References: <53D05145-CE87-424F-A492-BB22A09BBE11@gmail.com>
In-Reply-To: <53D05145-CE87-424F-A492-BB22A09BBE11@gmail.com>
From: Zhenwei Shang <a934172442@gmail.com>
Date: Fri, 8 May 2026 17:16:21 +0800
Message-ID: 
 <CABv9HU=rQeED3fiTA1Boyf2nLjX6TG=_18X8OM3LDZUqGO8LfA@mail.gmail.com>
Subject: Re: Fix wrong error message from pg_get_tablespace_ddl()
To: Chao Li <li.evan.chao@gmail.com>
Cc: PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
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Chao Li <li.evan.chao@gmail.com> =E4=BA=8E2026=E5=B9=B45=E6=9C=888=E6=97=A5=
=E5=91=A8=E4=BA=94 16:15=E5=86=99=E9=81=93=EF=BC=9A

> Hi,
>
> I started testing pg_get_tablespace_ddl(). While tracing
> pg_get_tablespace_ddl_internal(), I noticed that this error report must b=
e
> wrong:
> ```
>         /* User must have SELECT privilege on pg_tablespace. */
>         if (pg_class_aclcheck(TableSpaceRelationId, GetUserId(),
> ACL_SELECT) !=3D 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=3D# set allow_in_place_tablespaces =3D true;
> SET
> evantest=3D# create role r1;
> CREATE ROLE
> evantest=3D# create tablespace ts1 location '';
> CREATE TABLESPACE
> evantest=3D# revoke select on pg_tablespace from r1;
> REVOKE
> evantest=3D# set role r1;
> SET
> evantest=3D> 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 tim=
e
> for such a small fix. With the fix, the error message now looks like:
> ```
> evantest=3D> 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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<div dir=3D"ltr"><div dir=3D"ltr"><div dir=3D"ltr"><div dir=3D"ltr"><div di=
r=3D"ltr"><div dir=3D"ltr"><br></div><br><div class=3D"gmail_quote"><div di=
r=3D"ltr" class=3D"gmail_attr">Chao Li &lt;<a href=3D"mailto:li.evan.chao@g=
mail.com" target=3D"_blank">li.evan.chao@gmail.com</a>&gt; =E4=BA=8E2026=E5=
=B9=B45=E6=9C=888=E6=97=A5=E5=91=A8=E4=BA=94 16:15=E5=86=99=E9=81=93=EF=BC=
=9A<br></div><blockquote class=3D"gmail_quote" style=3D"margin:0px 0px 0px =
0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">Hi,<br>
<br>
I started testing pg_get_tablespace_ddl(). While tracing pg_get_tablespace_=
ddl_internal(), I noticed that this error report must be wrong:<br>
```<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 /* User must have SELECT privilege on pg_tables=
pace. */<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 if (pg_class_aclcheck(TableSpaceRelationId, Get=
UserId(), ACL_SELECT) !=3D ACLCHECK_OK)<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 {<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 ReleaseSysCache(tup=
le);<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 aclcheck_error(ACLC=
HECK_NO_PRIV, OBJECT_TABLESPACE, spcname);<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 }<br>
```<br>
<br>
The comment clearly says that SELECT privilege on pg_tablespace is required=
, but the error is reported against the target tablespace instead.<br>
<br>
This is easy to reproduce:<br>
```<br>
evantest=3D# set allow_in_place_tablespaces =3D true;<br>
SET<br>
evantest=3D# create role r1;<br>
CREATE ROLE<br>
evantest=3D# create tablespace ts1 location &#39;&#39;;<br>
CREATE TABLESPACE<br>
evantest=3D# revoke select on pg_tablespace from r1;<br>
REVOKE<br>
evantest=3D# set role r1;<br>
SET<br>
evantest=3D&gt; select * from pg_get_tablespace_ddl(&#39;ts1&#39;);<br>
ERROR:=C2=A0 permission denied for tablespace ts1<br>
```<br>
<br>
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:<br>
```<br>
evantest=3D&gt; select * from pg_get_tablespace_ddl(&#39;ts1&#39;);<br>
ERROR:=C2=A0 permission denied for table pg_tablespace<br>
```<br>
<br>
Oops, I was one of the reviewers of the original patch. Sorry for not findi=
ng this during review.<br>
<br>
Best regards,<br>
--<br>
Chao Li (Evan)<br>
HighGo Software Co., Ltd.<br>
<a href=3D"https://www.highgo.com/" rel=3D"noreferrer" target=3D"_blank">ht=
tps://www.highgo.com/</a><br><br></blockquote><div><br></div><div>Thanks fo=
r the patch. I can reproduce the problem and the fix looks correct to me.</=
div><div><br></div><div>Regards,<br>Zhenwei Shang</div></div></div>
</div>
</div>
</div>
</div>

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