| From: | Thomas Munro <thomas(dot)munro(at)gmail(dot)com> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | Tomas Vondra <tomas(at)vondra(dot)me>, Andres Freund <andres(at)anarazel(dot)de>, Michael Paquier <michael(at)paquier(dot)xyz>, Andrew Dunstan <andrew(at)dunslane(dot)net>, Amul Sul <sulamul(at)gmail(dot)com>, Zsolt Parragi <zsolt(dot)parragi(at)percona(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, Chao Li <li(dot)evan(dot)chao(at)gmail(dot)com>, Anthonin Bonnefoy <anthonin(dot)bonnefoy(at)datadoghq(dot)com>, Fujii Masao <masao(dot)fujii(at)gmail(dot)com>, Jakub Wartak <jakub(dot)wartak(at)enterprisedb(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org> |
| Subject: | Re: pg_waldump: support decoding of WAL inside tarfile |
| Date: | 2026-03-28 23:15:39 |
| Message-ID: | CA+hUKGK-GaHRh5mO0WKWO6MiL-iJ=+j_vVg4f-3pQXATNfRC2Q@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Sun, Mar 29, 2026 at 11:37 AM Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> I wrote:
> > 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?
>
> Bleah. Digging in the man pages at freebsd.org, I read
>
> --read-sparse
> (c, r, u modes only) Read sparse file information from disk.
> This is the reverse of --no-read-sparse and the default behav-
> ior.
>
> It's apparently been there and been default since FreeBSD 13.1.
> This leads one to wonder how come BF member dikkop is managing
> to run this test successfully. I speculate that it's using a
> filesystem type that doesn't do sparse files (cc'ing Vondra
> for confirmation on that).
>
> It looks like to make this test stable on modern FreeBSD,
> we need to see if tar accepts --no-read-sparse and use that
> switch if so.
Yeah. Here's my attempt at perl.
I think your Mac probably has a similar tar program BTW... but apfs
probably doesn't go around making holes visible to lseek()
automatically or at least as eagerly as my ZFS system.
| Attachment | Content-Type | Size |
|---|---|---|
| 0001-Fix-pg_waldump-test-for-libarchive-tar.patch | text/x-patch | 1.8 KB |
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