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From: Chao Li <[email protected]>
To: Japin Li <[email protected]>
Cc: PostgreSQL Hackers <[email protected]>
Subject: Re: Use SMgrRelation instead of SMgrRelationData * in pgaio_io_set_target_smgr()
Date: Mon, 16 Mar 2026 08:50:55 +0800
Message-ID: <[email protected]> (raw)
In-Reply-To: <SY7PR01MB10921122C8059E98C4923FE1CB642A@SY7PR01MB10921.ausprd01.prod.outlook.com>
References: <SY7PR01MB10921D0F6F3C2682570D6C31BB645A@SY7PR01MB10921.ausprd01.prod.outlook.com>
	<[email protected]>
	<SY7PR01MB10921122C8059E98C4923FE1CB642A@SY7PR01MB10921.ausprd01.prod.outlook.com>



> On Mar 14, 2026, at 11:07, Japin Li <[email protected]> wrote:
> 
> 
> Hi, Chao
> 
> On Fri, 13 Mar 2026 at 15:29, Chao Li <[email protected]> wrote:
>>> On Mar 13, 2026, at 15:05, Japin Li <[email protected]> wrote:
>>> 
>>> 
>>> Hi, hackers
>>> 
>>> While reading smgr.h, I noticed an inconsistent type usage in
>>> pgaio_io_set_target_smgr(). Currently the function is declared as:
>>> 
>>>   extern void pgaio_io_set_target_smgr(PgAioHandle *ioh,
>>>                                        SMgrRelationData *smgr,
>>>                                        ForkNumber forknum,
>>>                                        BlockNumber blocknum,
>>>                                        int nblocks,
>>> 
>>> However, SMgrRelation is defined as "typedef SMgrRelationData * SMgrRelation;",
>>> and all other functions in the smgr subsystem use SMgrRelation as the parameter
>>> type.
>>> 
>>> 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.
>>> 
>>> This is purely a style/consistency cleanup with no functional change.
>>> 
>>> Thoughts? Is this change acceptable?
>>> 
>>> -- 
>>> Regards,
>>> Japin Li
>>> ChengDu WenWu Information Technology Co., Ltd.
>>> 
>>> <v1-0001-Use-SMgrRelation-instead-of-SMgrRelationData-in-p.patch>
>> 
>> pgaio_io_set_target_smgr doesn’t update smgr, so, instead of “SMgrRelation”,  I think it’s better to change the type to "const SMgrRelationData *”.
> 
> Thanks for the review! Makes sense — I've updated the patch to v2.
> 
> -- 
> Regards,
> Japin Li
> ChengDu WenWu Information Technology Co., Ltd.
> 
> <v2-0001-Use-SMgrRelation-instead-of-SMgrRelationData-in-p.patch>

“const SMgrRelation *” will not work as you expected, you have to do “const SMgrRelationData *”. 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/

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