| From: | Andres Freund <andres(at)anarazel(dot)de> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | Robert Haas <robertmhaas(at)gmail(dot)com>, Daniel Gustafsson <daniel(at)yesql(dot)se>, Kyotaro Horiguchi <horikyota(dot)ntt(at)gmail(dot)com>, deniel1495(at)mail(dot)ru, Ibrar Ahmed <ibrar(dot)ahmad(at)gmail(dot)com>, tejeswarm(at)hotmail(dot)com, hlinnaka <hlinnaka(at)iki(dot)fi>, Masahiko Sawada <masahiko(dot)sawada(at)2ndquadrant(dot)com>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org>, Daniel Wood <hexexpert(at)comcast(dot)net> |
| Subject: | Re: Corruption during WAL replay |
| Date: | 2022-03-25 16:11:53 |
| Message-ID: | 20220325161153.7sh2xgcf2rqrtpaa@alap3.anarazel.de |
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| Lists: | pgsql-hackers |
Hi,
On 2022-03-25 11:50:48 -0400, Tom Lane wrote:
> Robert Haas <robertmhaas(at)gmail(dot)com> writes:
> > ... It's not
> > like a 16-bit checksum was state-of-the-art even when we introduced
> > it. We just did it because we had 2 bytes that we could repurpose
> > relatively painlessly, and not any larger number. And that's still the
> > case today, so at least in the short term we will have to choose some
> > other solution to this problem.
>
> Indeed. I propose the attached, which also fixes the unsafe use
> of seek() alongside syswrite(), directly contrary to what "man perlfunc"
> says to do.
That looks reasonable. Although I wonder if we loose something by not testing
the influence of the rest of the block - but I don't really see anything.
The same code also exists in src/bin/pg_basebackup/t/010_pg_basebackup.pl,
which presumably has the same collision risks. Perhaps we should put a
function into Cluster.pm and use it from both?
Greetings,
Andres Freund
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