Feedback-ID: ia2694551:Fastmail
Date: Tue, 29 Nov 2022 09:36:15 +0100
From: Alvaro Herrera <alvherre@alvh.no-ip.org>
To: Mladen Gogala <gogala.mladen@gmail.com>
Cc: pgsql-performance@lists.postgresql.org
Subject: Re: Catching up with performance & PostgreSQL 15
Message-ID: <20221129083615.fseqfvd5svtjbrb6@alvherre.pgsql>
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On 2022-Nov-28, Mladen Gogala wrote:

> As for JIT, I've recently asked that question myself. I was told that
> PostgreSQL with LLVM enabled performs approximately 25% better than without
> it.

Hmm, actually, normally you're better off turning JIT off, because it's
very common to diagnose cases of queries that become much, much slower
because of it.  Some queries do become faster, but it's not a wide
margin, and it's not a lot.  There are rare cases where JIT is
beneficial, but those tend to be queries that take upwards of several
seconds already.

IMO it was a mistake to turn JIT on in the default config, so that's one
thing you'll likely want to change.

-- 
Álvaro Herrera               48°01'N 7°57'E  —  https://www.EnterpriseDB.com/
"Thou shalt not follow the NULL pointer, for chaos and madness await
thee at its end." (2nd Commandment for C programmers)