Feedback-ID: id4a34324:Fastmail
Date: Tue, 10 Mar 2026 13:11:09 -0400
From: Andres Freund <andres@anarazel.de>
To: Fujii Masao <masao.fujii@gmail.com>
Cc: Anthonin Bonnefoy <anthonin.bonnefoy@datadoghq.com>,
	Alexander Lakhin <exclusion@gmail.com>,
 PostgreSQL Hackers <pgsql-hackers@postgresql.org>
Subject: Re: Shutdown indefinitely stuck due to unflushed FPI_FOR_HINT record
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Hi,

On 2026-03-06 16:48:06 +0900, Fujii Masao wrote:
> On Fri, Mar 6, 2026 at 8:46 AM Fujii Masao <masao.fujii@gmail.com> wrote:
> >
> > On Thu, Mar 5, 2026 at 5:40 PM Anthonin Bonnefoy
> > <anthonin.bonnefoy@datadoghq.com> wrote:
> > > So it was relying on GetInsertRecPtr() instead of
> > > GetXLogInsertRecPtr(). As mentioned in the thread, GetInsertRecPtr()
> > > only returns the position of the last full xlog page, meaning it
> > > doesn't fix the issue we have where the last partial page contains a
> > > continuation record.
> > >
> > > Testing the XLogFlush(GetInsertRecPtr()) patch with my script, I still
> > > get the shutdown stuck issue.
> > >
> > > Using GetXLogInsertRecPtr() is required to make sure the last partial
> > > page is correctly flushed.
> >
> > Since GetXLogInsertRecPtr() returns a bogus LSN and XLogFlush() does
> > almost nothing during recovery, I added a !RecoveryInProgress() check
> > as follows. I've attached the latest version of the patch and updated
> > the commit message.
> >
> > - if (got_STOPPING)
> > - XLogBackgroundFlush();
> > + if (got_STOPPING && !RecoveryInProgress())
> > + XLogFlush(GetXLogInsertRecPtr());
> 
> I've pushed the patch. Thanks!

I'm pretty sure this is not correct as-is, it suffers from the same issue as
https://postgr.es/m/vf4hbwrotvhbgcnknrqmfbqlu75oyjkmausvy66ic7x7vuhafx%40e4rvwavtjswo
I.e. it is not safe to use GetXLogInsertRecPtr() to determine up to where to
flush to, due to page boundaries.

Greetings,

Andres Freund