From: Japin Li <japinli@hotmail.com>
To: Chao Li <li.evan.chao@gmail.com>
Cc: PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Subject: Re: Use SMgrRelation instead of SMgrRelationData * in
 pgaio_io_set_target_smgr()
In-Reply-To: <A5A6A4A1-1AB5-414E-81CF-6BC22DDA1473@gmail.com> (Chao Li's
	message of "Mon, 16 Mar 2026 08:50:55 +0800")
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Date: Mon, 16 Mar 2026 10:31:23 +0800
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On Mon, 16 Mar 2026 at 08:50, Chao Li <li.evan.chao@gmail.com> wrote:
>> On Mar 14, 2026, at 11:07, Japin Li <japinli@hotmail.com> wrote:
>>=20
>>=20
>> Hi, Chao
>>=20
>> On Fri, 13 Mar 2026 at 15:29, Chao Li <li.evan.chao@gmail.com> wrote:
>>>> On Mar 13, 2026, at 15:05, Japin Li <japinli@hotmail.com> wrote:
>>>>=20
>>>>=20
>>>> Hi, hackers
>>>>=20
>>>> While reading smgr.h, I noticed an inconsistent type usage in
>>>> pgaio_io_set_target_smgr(). Currently the function is declared as:
>>>>=20
>>>>   extern void pgaio_io_set_target_smgr(PgAioHandle *ioh,
>>>>                                        SMgrRelationData *smgr,
>>>>                                        ForkNumber forknum,
>>>>                                        BlockNumber blocknum,
>>>>                                        int nblocks,
>>>>=20
>>>> However, SMgrRelation is defined as "typedef SMgrRelationData * SMgrRe=
lation;",
>>>> and all other functions in the smgr subsystem use SMgrRelation as the =
parameter
>>>> type.
>>>>=20
>>>> To keep the code consistent with the rest of the smgr API, this patch =
changes
>>>> the parameter from SMgrRelationData * to SMgrRelation in both the defi=
nition
>>>> and declaration.
>>>>=20
>>>> This is purely a style/consistency cleanup with no functional change.
>>>>=20
>>>> Thoughts? Is this change acceptable?
>>>>=20
>>>> --=20
>>>> Regards,
>>>> Japin Li
>>>> ChengDu WenWu Information Technology Co., Ltd.
>>>>=20
>>>> <v1-0001-Use-SMgrRelation-instead-of-SMgrRelationData-in-p.patch>
>>>=20
>>> pgaio_io_set_target_smgr doesn=E2=80=99t update smgr, so, instead of =
=E2=80=9CSMgrRelation=E2=80=9D,  I think it=E2=80=99s better to change the =
type to "const SMgrRelationData *=E2=80=9D.
>>=20
>> Thanks for the review! Makes sense =E2=80=94 I've updated the patch to v=
2.
>>=20
>> --=20
>> Regards,
>> Japin Li
>> ChengDu WenWu Information Technology Co., Ltd.
>>=20
>> <v2-0001-Use-SMgrRelation-instead-of-SMgrRelationData-in-p.patch>
>
> =E2=80=9Cconst SMgrRelation *=E2=80=9D will not work as you expected, you=
 have to do =E2=80=9Cconst SMgrRelationData *=E2=80=9D. We want to protect =
the data the pointer pointing to from changing but the pointer itself.

Thanks for pointing that out!  I hadn't noticed the difference before.
Updated as you suggested.

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

--=20
Regards,
Japin Li
ChengDu WenWu Information Technology Co., Ltd.


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