| 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 04:54:38 |
| Message-ID: | 20220325045438.enwakjqhrafzq5f2@alap3.anarazel.de |
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| Lists: | pgsql-hackers |
Hi,
On 2022-03-25 00:08:20 -0400, Tom Lane wrote:
> Andres Freund <andres(at)anarazel(dot)de> writes:
> > The only thing I can really conclude here is that we apparently end up with
> > the same checksum for exactly the modifications we are doing? Just on those
> > two damn instances? Reliably?
>
> IIRC, the table's OID or relfilenode enters into the checksum.
> Could it be that assigning a specific OID to the table allows
> this to happen, and these two animals are somehow assigning
> that OID while others are using some slightly different OID?
It's just the block number that goes into it.
I do see that the LSN that ends up on the page is the same across a few runs
of the test on serinus. Which presumably differs between different
animals. Surprised that it's this predictable - but I guess the run is short
enough that there's no variation due to autovacuum, checkpoints etc.
If I add a 'SELECT txid_current()' before the CREATE TABLE in
check_relation_corruption(), the test doesn't fail anymore, because there's an
additional WAL record.
16bit checksums for the win.
Greetings,
Andres Freund
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