Re: pg_waldump: support decoding of WAL inside tarfile

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Thomas Munro <thomas(dot)munro(at)gmail(dot)com>
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: 2026-03-29 22:23:31
Message-ID: 1873141.1774823011@sss.pgh.pa.us
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Thomas Munro <thomas(dot)munro(at)gmail(dot)com> writes:
> Anyway, given the defaults, GNU tar + ZFS/BTRFS users must be pretty
> unlikely to hit this in the wild, and the symptom is a confusing error
> in a maintenance tool, not corruption, so I don't think this is a big
> deal. I might still try teaching the astreamer code to understand PAX
> 1.0 when it sees it in the next cycle though, for the benefit of
> FreeBSD users.

I agree that this isn't too critical if the effects are confined to
pg_waldump. I believe that pg_basebackup and pg_verifybackup also use
astreamer_tar.c, but it's not clear to me if they'd ever be asked to
parse files made by tar(1) and not by our own sparseness-ignorant
tar-writing code. If they can be, that'd be a higher-priority reason
to fill in this gap.

regards, tom lane

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