Re: Changing the state of data checksums in a running cluster

Hi

On Tue, May 5, 2026 at 12:08 PM Daniel Gustafsson <daniel(at)yesql(dot)se> wrote:

> > On 5 May 2026, at 17:21, Ayush Tiwari <ayushtiwari(dot)slg01(at)gmail(dot)com>
> wrote:
>
> > I've a small concern in 0001. The new guard uses only
> RelationNeedsWAL(reln),
> > but ProcessSingleRelationByOid() iterates all forks. For unlogged
> relations,
> > the init fork is special, there are several existing call sites that
> preserve
> > WAL for INIT_FORKNUM, for example using
> >
> > RelationNeedsWAL(rel) || forknum == INIT_FORKNUM
> >
> > and catalog/storage.c notes that unlogged init forks need WAL and sync.
> >
> > So I think the condition in ProcessSingleRelationFork() should preserve
> the
> > init-fork case, e.g.
> >
> > if (RelationNeedsWAL(reln) || forkNum == INIT_FORKNUM)
> > log_newpage_buffer(buf, false);
>
> Which failure scenario are you thinking about here? When dealing with the
> catalog relation I can see the need but here we are reading, and writing,
> data
> pages. In which case would we need to issue an FPI for an unlogged
> relation
> init fork? I might be missing something obvious here.

Good catch,IIUC init page has valid checksum and when we set checksum on
primary I think we need to pass it to standby. Otherwise, after failover we
may see invalid checksum for unlogged relations. I haven’t validated it,
will test it and update the patch.