Re: pg_walfile_name_offset can return inconsistent values

On Thu, Nov 09, 2023 at 04:14:07PM -0500, Bruce Momjian wrote:
> Attached is the full patch that changes pg_walfile_name_offset() and
> pg_walfile_name().  There is no need for doc changes.  We need to
> document this as incompatible in case users are realying on the old
> behavior for WAL archiving purposes.  If they want the old behavior they
> need to check for an offset of zero and subtract one from the file name.

FWIW, I am not really convinced that there is a strong need to
backpatch any of that.  There's a risk that some queries relying on
the old behavior suddenly break after a minor release, and that's
always annoying.  A HEAD-only change seems like a safer bet to me.

> Can someone check that all other calls to XLByteToPrevSeg() are correct?

On a quick check, all the other calls use that for end record LSNs, so
that looks fine.
--
Michael