Re: Add missing JIT inline pass for llvm>=17

From: Pierre Ducroquet <p(dot)psql(at)pinaraf(dot)info>
To: Álvaro Herrera <alvherre(at)kurilemu(dot)de>, pgsql-hackers(at)lists(dot)postgresql(dot)org
Cc: Andreas Karlsson <andreas(at)proxel(dot)se>, Anthonin Bonnefoy <anthonin(dot)bonnefoy(at)datadoghq(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org>, Michael Banck <mbanck(at)gmx(dot)net>
Subject: Re: Add missing JIT inline pass for llvm>=17
Date: 2026-01-19 10:52:51
Message-ID: 1820938.rQZk8KEl4X@peanuts2
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On Friday, January 16, 2026 10:29:59 AM Central European Standard Time Michael
Banck wrote:
> Hi,
>
> On Thu, Jan 15, 2026 at 12:26:23PM +0100, Álvaro Herrera wrote:
> > On 2026-Jan-15, Andreas Karlsson wrote:
> > > Great find! Sadly shows how little people actually use JIT.
> >
> > I disagree. Given that JIT is enabled by default, I think lots of
> > people use it.
>
> Well, not sure about that - all of the three major hyperscalers disable
> JIT in their managed Postgres offerings (or at least used to when I last
> checked), and those are a major chunk of usage these days. Also, both
> the RPM and (since recently) the Debian/Ubuntu community packages have
> factored out the LLVM/jit part into their own packages and AFAIK they do
> not get installed by default.
>
> So while the GUC is on by default, a lot of users might not use JIT
> these days and not know either way.
>
> > What they don't do, is realize that things are slower
> > than they could be -- much less try to figure out why.
>
> Right.

People have also seen blog articles saying «JIT is bad, switch it off» that are
right if you are in the wrong use cases for JIT. Which, to be fair, is not
easy to figure out.

Re. the topic, good catch, I was looking at the JITted assembly code a few
days ago and was left with that in the back of my mind, patch reviewed and +1

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