Re: WAL format changes

On Tue, Jun 19, 2012 at 4:14 AM, Heikki Linnakangas
<heikki(dot)linnakangas(at)enterprisedb(dot)com> wrote:
> Well, that was easier than I thought. Attached is a patch to make XLogRecPtr
> a uint64, on top of my other WAL format patches. I think we should go ahead
> with this.

+1.

> The LSNs on pages are still stored in the old format, to avoid changing the
> on-disk format and breaking pg_upgrade. The XLogRecPtrs stored the control
> file and WAL are changed, however, so an initdb (or at least pg_resetxlog)
> is required.

Seems fine.

> Should we keep the old representation in the replication protocol messages?
> That would make it simpler to write a client that works with different
> server versions (like pg_receivexlog). Or, while we're at it, perhaps we
> should mandate network-byte order for all the integer and XLogRecPtr fields
> in the replication protocol. That would make it easier to write a client
> that works across different architectures, in >= 9.3. The contents of the
> WAL would of course be architecture-dependent, but it would be nice if
> pg_receivexlog and similar tools could nevertheless be
> architecture-independent.

I share Andres' question about how we're doing this already. I think
if we're going to break this, I'd rather do it in 9.3 than 5 years
from now. At this point it's just a minor annoyance, but it'll
probably get worse as people write more tools that understand WAL.

> I kept the %X/%X representation in error messages etc. I'm quite used to
> that output, so reluctant to change it, although it's a bit silly now that
> it represents just 64-bit value. Using UINT64_FORMAT would also make the
> messages harder to translate.

I could go either way on this one, but I have no problem with the way
you did it.

--
Robert Haas
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