Re: [PATCH] Refactor: Extract XLogRecord info

Hi, Xiaoran,

I see. The code is checking if the bits other than rmgr bits,
XLR_SPECIAL_REL_UPDATE and XLR_CHECK_CONSISTENCY are used.

Thanks for the explanation.

Steven

Xiaoran Wang <fanfuxiaoran(at)gmail(dot)com> 于2025年6月11日周三 10:13写道：

>
>
> Steven Niu <niushiji(at)gmail(dot)com> 于2025年6月10日周二 17:56写道：
>
>> I'm confused by the code of XLR_RMGR_INFO_MASK and XLR_INFO_MASK.
>>
>> According to the definition of masks, the high 4 bits are for rmgr.
>>
>> /*
>> * The high 4 bits in xl_info may be used freely by rmgr. The
>> * XLR_SPECIAL_REL_UPDATE and XLR_CHECK_CONSISTENCY bits can be passed by
>> * XLogInsert caller. The rest are set internally by XLogInsert.
>> */
>> #define XLR_INFO_MASK 0x0F
>> #define XLR_RMGR_INFO_MASK 0xF0
>>
>>
>> However, in function XLogInsert(), there is code:
>>
>> /*
>> * The caller can set rmgr bits, XLR_SPECIAL_REL_UPDATE and
>> * XLR_CHECK_CONSISTENCY; the rest are reserved for use by me.
>> */
>> if ((info & ~(XLR_RMGR_INFO_MASK |
>> XLR_SPECIAL_REL_UPDATE |
>> XLR_CHECK_CONSISTENCY)) != 0)
>> elog(PANIC, "invalid xlog info mask %02X", info);
>>
>> XLogInsert only allows the rmgr ,XLR_SPECIAL_REL_UPDATE and
> XLR_CHECK_CONSISTENCY
> set in the info.
>
>> #define XLR_SPECIAL_REL_UPDATE 0x01
>> #define XLR_CHECK_CONSISTENCY 0x02
>>
>> As the XLR_SPECIAL_REL_UPDATE and XLR_CHECK_CONSISTENCY are of the low 4
>> bits,
>> the above code is indicating the low 4 bits are for rmgr too?
>>
>
> No, only the high 4 bits are used for RMGR, see the code under directory
> 'src/backend/access/rmgrdesc'
>
> 'XLR_SPECIAL_REL_UPDATE' and 'XLR_CHECK_CONSISTENCY' are not RMGR info,
> but they
> can be passed by XLogInsert caller.
>
>>
>>
>> Did I misunderstand something?
>>
>> Thanks，
>> Steven
>>
>
> --
> Best regards !
> Xiaoran Wang
>