Date: Mon, 7 Mar 2022 09:54:22 -0800
From: Andres Freund <andres@anarazel.de>
To: hubert depesz lubaczewski <depesz@depesz.com>
Cc: Tom Lane <tgl@sss.pgh.pa.us>,
	PostgreSQL General <pgsql-general@lists.postgresql.org>
Subject: Re: Interesting fail when migrating Pg from Ubuntu Bionic to Focal
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Hi,

On 2022-03-07 16:11:28 +0100, hubert depesz lubaczewski wrote:
> On Sun, Mar 06, 2022 at 11:10:00AM -0500, Tom Lane wrote:
> > > I tore these boxes down, so can't check immediately, but I think
> > > I remember that you're right - single-row queries didn't use JIT.
> 
> Got focal box up. Loaded schema for Pg.
> 
> Initially select didn't break anything, but when I tuned down
> jit_above_cost so that it will kick in - got fails immediately.

Could you set jit_debugging_support=on and show a backtrace with that?


> > FWIW, I went to the trouble of installing Ubuntu Focal on my
> > raspberry pi to see if I could duplicate this, and I couldn't.
> > However, what you get from a fresh install now is
> > $ dpkg -l | grep libllvm                  
> > ii  libllvm10:arm64                1:10.0.0-4ubuntu1                     arm64        Modular compiler and toolchain technologies, runtime library
> > not 9.0.1.  I also found that Fedora 31/aarch64 is still downloadable, and
> > that does contain LLVM 9 ... and I could not reproduce it there either.
> 
> Soo... plot thickens.
> 
> Looks that pg 12 supplied by pgdg required libllvm9:

What are the libllvm package versions on which you can reproduce the crash?


> Newer pg12 (12.10) from pgdg also depends on llvm9. Perhaps changing the deb to
> use/depend-on llvm10 would solve the problem, for now I'm not sure how to do
> it. Reached to Christoph about it.

It'd require rebuilding.


It's possible that the problem is one of the patches applied by ubuntu to llvm
and that's why others can't reproduce so far. There's quite a few...

Greetings,

Andres Freund