Date: Thu, 20 Jan 2022 18:02:43 -0300
From: Alvaro Herrera <alvherre@alvh.no-ip.org>
To: Jaime Casanova <jcasanov@systemguards.com.ec>
Cc: Simon Riggs <simon.riggs@enterprisedb.com>,
	Tomas Vondra <tomas.vondra@enterprisedb.com>,
	Zhihong Yu <zyu@yugabyte.com>,
	Daniel Westermann <dwe@dbi-services.com>,
	Amit Langote <amitlangote09@gmail.com>,
	Justin Pryzby <pryzby@telsasoft.com>,
	Pg Hackers <pgsql-hackers@lists.postgresql.org>,
	Pavan Deolasee <pavan.deolasee@gmail.com>
Subject: Re: support for MERGE
Message-ID: <202201202102.5ta7rb3vyvkh@alvherre.pgsql>
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On 2022-Jan-12, Jaime Casanova wrote:

> I found two crashes, actually I found them on the original patch Álvaro
> sent on november but just checked that those already exists.
> 
> I configured with:
> 
> CFLAGS="-ggdb -Og -g3 -fno-omit-frame-pointer" ./configure --prefix=/opt/var/pgdg/15/merge --enable-debug --enable-depend --enable-cassert --with-llvm --enable-tap-tests --with-pgport=54315
> 
> And tested on the regression database.
> 
> Attached the SQL files for the crashes and its respective stacktraces.
> FWIW, the second crash doesn't appear to be caused by the MERGE patch
> but I cannot trigger it other way.

Thanks for this!  The problem in the first crash was that when
partitioned tables are being used and the topmost one has a tuple
descriptor different from the partitions, we were doing the projection
to the partition's slot using the root's tupledesc and a targetlist
written for the root.  The reason this crashed in such ugly way is that
in this case the parent has 3 columns (2 dropped) while the partitions
only have one, so the projection was trying to write to an attribute
that didn't exist.

I fixed it by making all NOT MATCHED actions use the root table's
descriptor and slot.

This change fixes both your reported crashes.  I didn't look closely to
see if the second one is caused by exactly the same issue.

-- 
Álvaro Herrera              Valdivia, Chile  —  https://www.EnterpriseDB.com/
Tom: There seems to be something broken here.
Teodor: I'm in sackcloth and ashes...  Fixed.
        http://archives.postgresql.org/message-id/482D1632.8010507@sigaev.ru