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Subject: Re: Use SMgrRelation instead of SMgrRelationData * in
 pgaio_io_set_target_smgr()
From: Chao Li <li.evan.chao@gmail.com>
In-Reply-To: 
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Date: Mon, 16 Mar 2026 11:14:57 +0800
Cc: PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
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To: Japin Li <japinli@hotmail.com>
Archived-At: 
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> On Mar 16, 2026, at 10:31, Japin Li <japinli@hotmail.com> wrote:
>=20
> 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 * =
SMgrRelation;",
>>>>> 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 =
definition
>>>>> 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 v2.
>>>=20
>>> --=20
>>> Regards,
>>> Japin Li
>>> ChengDu WenWu Information Technology Co., Ltd.
>>>=20
>>> <v2-0001-Use-SMgrRelation-instead-of-SMgrRelationData-in-p.patch>
>>=20
>> =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.
>=20
> Thanks for pointing that out!  I hadn't noticed the difference before.
> Updated as you suggested.
>=20
>>=20
>> Best regards,
>> --
>> Chao Li (Evan)
>> HighGo Software Co., Ltd.
>> https://www.highgo.com/
>=20
> --=20
> Regards,
> Japin Li
> ChengDu WenWu Information Technology Co., Ltd.
>=20
> <v3-0001-Add-the-const-qualifier-to-the-SMgrRelationData-p.patch>

V3 LGTM.

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