Re: Change checkpoint‑record‑missing PANIC to FATAL

> > That's a good point. I agree these new cases are very close to what we
> > already have on HEAD. I can rework this to avoid duplication by
> > grouping them with the existing tests.
>
> Thanks. I am not sure if I will be able to follow up the work of this
> thread for this commit fest, so I'll probably consider more
> improvements in this area once v20 opens for business around the end
> of June.

I went ahead and reworked this to avoid duplication by grouping the
new coverage into the existing tests that already carry most of the
setup.

For the missing-redo path, as discussed above, I added the
backup_label variant to t/050_redo_segment_missing.pl. 050 already has
the injection-point setup needed to split redo and checkpoint records
across WAL segments, so reusing it avoids duplicating that
orchestration elsewhere.

For the missing-checkpoint path, I added the backup_label variant to
t/042_low_level_backup.pl. 042 already owns the low-level-backup +
backup_label setup, so it seemed like the natural place. 052 remains
focused on the no-backup_label checkpoint-missing path.

So the intent was to keep each new case close to the existing test
that already has most of the required setup, and minimize duplication.

Kindly review and share your feedback.

Best Regards,
Nitin Jadhav
Azure Database for PostgreSQL
Microsoft