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 explanation.

Steven

在 2025/6/11 10:13, Xiaoran Wang 写道:
>
>
> Steven Niu <niushiji(at)gmail(dot)com <mailto: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