Re: pg_waldump: support decoding of WAL inside tarfile

Thomas Munro <thomas.munro@gmail.com> writes:
> It seems like the place we'd be looking for the file is in
> astreamer_tar_header(), so I added in some caveman debugging:

> XXXX [PaxHeader/000000010000000000000002] XXXX
> XXXX [GNUSparseFile.0/000000010000000000000002] XXXX

After a bit of research, I see the problem: your tar has decided to
store 000000010000000000000002 as a sparse file, and evidently it
inserts "GNUSparseFile.0/" into the file name when it does that.
Our tar-parsing logic will not recognize that name as being one
of the WAL files it wants; and even if it did, it doesn't know
how to de-sparse the file contents, so it would get the wrong
output.

I'm pretty disinclined to try to support sparse files here,
especially with ~10 days till feature freeze.

However ... I do not find any indication in the GNU tar docs
that it produces sparse files by default.  It looks like you
need to say -S/--sparse to make that happen.  Maybe you have
a version that's been hacked to make that the default?

            regards, tom lane