Horton

Re: Fix lag columns in pg_stat_replication not advancing when replay LSN stalls

Fujii Masao <masao.fujii@gmail.com>

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From: Fujii Masao <masao.fujii@gmail.com>
To: Xuneng Zhou <xunengzhou@gmail.com>
Cc: Shinya Kato <shinya11.kato@gmail.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>, Chao Li <li.evan.chao@gmail.com>
Date: 2025-10-22T02:34:13Z
Lists: pgsql-hackers 
On Tue, Oct 21, 2025 at 11:52 PM Xuneng Zhou <xunengzhou@gmail.com> wrote:
> The patch LGTM.

Thanks for the review!
I've pushed the patch and backpatched it to all supported versions.


> I am wondering whether it is helpful to add some
> comments for this overflowed array

Yes, do you have any specific suggestions?


> and replacing literal zeros with the constant InvalidXLogRecPtr for
> better readability.
>
> /* InvalidXLogRecPtr means no overflow yet */
> if (lag_tracker->overflowed[i].lsn == InvalidXLogRecPtr)

I couldn't find any code like "lag_tracker->overflowed[i].lsn == 0",
so I'm not sure which part should be replaced with InvalidXLogRecPtr.
Could you point me to the exact location?

Regards,

-- 
Fujii Masao

Commits

  1. Add comments explaining overflow entries in the replication lag tracker.

  2. Fix stalled lag columns in pg_stat_replication when replay LSN stops advancing.