Message-ID: <97a382c0-1f19-4ea0-951f-e37e6abc34a3@vondra.me>
Date: Sat, 28 Mar 2026 23:57:37 +0100
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Subject: Re: pg_waldump: support decoding of WAL inside tarfile
To: Tom Lane <tgl@sss.pgh.pa.us>, Thomas Munro <thomas.munro@gmail.com>
Cc: Andres Freund <andres@anarazel.de>, Michael Paquier
 <michael@paquier.xyz>, Andrew Dunstan <andrew@dunslane.net>,
 Amul Sul <sulamul@gmail.com>, Zsolt Parragi <zsolt.parragi@percona.com>,
 Robert Haas <robertmhaas@gmail.com>, Chao Li <li.evan.chao@gmail.com>,
 Anthonin Bonnefoy <anthonin.bonnefoy@datadoghq.com>,
 Fujii Masao <masao.fujii@gmail.com>,
 Jakub Wartak <jakub.wartak@enterprisedb.com>,
 PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
References: <2250061.1774104346@sss.pgh.pa.us>
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From: Tomas Vondra <tomas@vondra.me>
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On 3/28/26 23:36, Tom Lane 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's running on ufs. But I think the explanation is very simple. We had
a short power outage on Thursday, and the FreeBSD machine failed to boot
properly after the power was restored. IIUC this test is new, right?

I fixed the machine, it'll start running the tests in a couple minutes.


regards

-- 
Tomas Vondra