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From: Robert Haas <robertmhaas@gmail.com>
Date: Tue, 20 Dec 2022 15:39:26 -0500
Message-ID: 
 <CA+TgmoaOsoQuXEo6gMq0GP8SyvCaS=ptYqdYc0uzDMoeShf_nw@mail.gmail.com>
Subject: Re: Minimal logical decoding on standbys
To: Andres Freund <andres@anarazel.de>
Cc: "Drouvot, Bertrand" <bertranddrouvot.pg@gmail.com>,
 Alvaro Herrera <alvherre@2ndquadrant.com>,
	Ibrar Ahmed <ibrar.ahmad@gmail.com>, Amit Khandekar <amitdkhan.pg@gmail.com>,
 fabriziomello@gmail.com,
	tushar <tushar.ahuja@enterprisedb.com>,
 Rahila Syed <rahila.syed@2ndquadrant.com>,
	pgsql-hackers <pgsql-hackers@postgresql.org>
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On Tue, Dec 20, 2022 at 1:25 PM Robert Haas <robertmhaas@gmail.com> wrote:
> I'm going to go through all the record types one by one before
> commenting further.

OK, so xl_hash_vacuum_one_page, at least, is a live issue. To reproduce:

./configure <whatever your usual options are>
echo 'COPT=-fsanitize=alignment -fno-sanitize-recover=all' > src/Makefile.custom
make -j8
make install
initdb
postgres

Then in another window:

pg_basebackup -D pgstandby -R
# edit postgresql.conf, change port number
postgres -D pgstandby

Then in a third window, using the attached files:

pgbench -i -s 10
psql -f kpt_hash_setup.sql
pgbench -T 10 -c 4 -j 4 -f kpt_hash_pgbench.sql

With the patch, the standby falls over:

bufpage.c:1194:31: runtime error: load of misaligned address
0x7fa62f05d119 for type 'OffsetNumber' (aka 'unsigned short'), which
requires 2 byte alignment
0x7fa62f05d119: note: pointer points here
 00 00 00  00 e5 00 8f 00 00 00 00  87 00 ab 20 20 20 20 20  20 20 20
20 20 20 20 20  20 20 20 20 20
              ^

Without the patch, this doesn't occur.

I think this might be the only WAL record type where there's a
problem, but I haven't fully confirmed that yet.

-- 
Robert Haas
EDB: http://www.enterprisedb.com

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