Re: [PATCH] Refactor: Extract XLogRecord info - Mailing list pgsql-hackers

From Steven Niu
Subject Re: [PATCH] Refactor: Extract XLogRecord info
Date
Msg-id CABBtG=cAyq3Py+swRQ+5QDE_+yt+k-w5Bv-F8E2h9vHeGS91Ww@mail.gmail.com
Whole thread Raw
In response to Re: [PATCH] Refactor: Extract XLogRecord info  (wenhui qiu <qiuwenhuifx@gmail.com>)
Responses Re: [PATCH] Refactor: Extract XLogRecord info
List pgsql-hackers
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);

#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?

Did I misunderstand something? 

Thanks,
Steven

wenhui qiu <qiuwenhuifx@gmail.com> 于2025年6月10日周二 16:00写道:
HI 
> FWIW, I'm not sure what's the benefit of the proposal which comes down
> to the removal of a bitwise NOT, except more code conflicts with back
> branches.
Agree 

On Tue, Jun 10, 2025 at 3:37 PM Michael Paquier <michael@paquier.xyz> wrote:
On Mon, Jun 09, 2025 at 10:54:43PM -0300, Fabrízio de Royes Mello wrote:
> The refactoring LGTM but do we really need two patches? IMHO you can just
> merge everything into a single patch.

FWIW, I'm not sure what's the benefit of the proposal which comes down
to the removal of a bitwise NOT, except more code conflicts with back
branches.
--
Michael

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