Re: pg_waldump: support decoding of WAL inside tarfile

Hi,

On Thu, 2 Apr 2026 at 21:48, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>
> FORMAT is one of the following:
> gnu GNU tar 1.13.x format
> oldgnu GNU format as per tar <= 1.12
> pax POSIX 1003.1-2001 (pax) format
> posix same as pax
> ustar POSIX 1003.1-1988 (ustar) format
> v7 old V7 tar format
> ...
> *This* tar defaults to:
> --format=posix -f- -b20 --quoting-style=escape --rmt-command=/usr/bin/rmt
> --rsh-command=/usr/bin/ssh
>
> So there you have it: pax format by default. This is unlike what
> I see on RHEL or Fedora:

It seems that the problem also applies to OpenBSD [1]:

-F format
Specify the output archive format, with the default format being
pax. tar currently supports the following formats:

OpenBSD CI tasks started to fail [2] after bc30c704ad with the errors:

```
Listing only the last 100 lines from a long log.
# at /home/postgres/postgres/src/bin/pg_waldump/t/001_basic.pl line 440.
# got: 'pg_waldump: error: pax extensions to tar format are
not supported

# Failed test 'corrupt backup fails verification: extra_file: matches'
# at /home/postgres/postgres/src/bin/pg_verifybackup/t/003_corruption.pl
line 198.
# 'pg_verifybackup: error: pax extensions to tar
format are not supported

Summary of Failures:
239/381 postgresql:pg_waldump / pg_waldump/001_basic
ERROR 18.58s exit status 84
225/381 postgresql:pg_verifybackup / pg_verifybackup/003_corruption
ERROR 45.12s exit status 8
```

I also tried Thomas'
"v2-0001-Improve-tar-portability-logic-from-ebba64c0" [3] but it
didn't fix the problem on OpenBSD [4].

[1] https://man.openbsd.org/tar#F
[2] https://cirrus-ci.com/task/5439721360326656
[3] https://postgr.es/m/CA%2BhUKGLMkv_fnGXzVRO8qbx5uHs-qMn151GTJYCfn9w1ZamGNg%40mail.gmail.com
[4] https://cirrus-ci.com/task/5602126958690304

--
Regards,
Nazir Bilal Yavuz
Microsoft