Re: Skipping logical replication transactions on subscriber side

On Thu, Jun 16, 2022 at 2:27 AM Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
>
> On Tue, Jun 14, 2022 at 3:54 AM Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> wrote:
> > > AFAICS, we could do that by:
> > >
> > > 1. De-supporting platforms that have this problem, or
> > > 2. Introducing new typalign values, as Noah proposed back on April 2, or
> > > 3. Somehow forcing values that are sometimes 4-byte aligned and
> > > sometimes 8-byte aligned to be 8-byte alignment on all platforms
> >
> > Introducing new typalign values seems a good idea to me as it's more
> > future-proof. Will this item be for PG16, right? The main concern
> > seems that what this test case enforces would be nuisance when
> > introducing a new system catalog or a new column to the existing
> > catalog but given we're in post PG15-beta1 it is unlikely to happen in
> > PG15.
>
> I agree that we're not likely to introduce a new typalign value any
> sooner than v16. There are a couple of things that bother me about
> that solution. One is that I don't know how many different behaviors
> exist out there in the wild. If we distinguish the alignment of double
> from the alignment of int8, is that good enough, or are there other
> data types whose properties aren't necessarily the same as either of
> those?

Yeah, there might be.

> The other is that 32-bit systems are already relatively rare
> and probably will become more rare until they disappear completely. It
> doesn't seem like a ton of fun to engineer solutions to problems that
> may go away by themselves with the passage of time.

IIUC the system affected by this problem is not necessarily 32-bit
system. For instance, the hoverfly on buildfarm is 64-bit system but
was affected by this problem. According to the XLC manual[1], there is
no difference between 32-bit systems and 64-bit systems in terms of
alignment for double. FWIW, looking at the manual, there might have
been a solution for AIX to specify -qalign=natural compiler option in
order to enforce the alignment of double to 8.

Regards,

[1] https://support.scinet.utoronto.ca/Manuals/xlC++-proguide.pdf;
Table 11 on page 10.

--
Masahiko Sawada
EDB: https://www.enterprisedb.com/