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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 08:50:55 +0800
Cc: PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
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To: Japin Li <japinli@hotmail.com>
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> 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>

=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.

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