Date: Fri, 31 May 2019 18:38:23 -0500
From: Justin Pryzby <pryzby@telsasoft.com>
To: Andreas Joseph Krogh <andreas@visena.com>
Cc: Tobias Gierke <tobias.gierke@code-sourcery.de>,
	Andres Freund <andres@anarazel.de>,
	PostgreSQL mailing lists <pgsql-performance@postgresql.org>
Subject: Re: Sv: JIT in PostgreSQL 12 ?
Message-ID: <20190531233822.GR27382@telsasoft.com>
References: <b1705e1a-90dc-f614-74cb-2e003a457758@code-sourcery.de>
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On Wed, May 29, 2019 at 10:48:19AM +0200, Andreas Joseph Krogh wrote:
> På onsdag 29. mai 2019 kl. 10:02:50, skrev Tobias Gierke <tobias.gierke@code-sourcery.de>
> Hi,
> 
>  Browsing the PostgreSQL 12 release notes I noticed that JIT is now
>  enabled by default. Having not followed PostgreSQL development closely -
>  does this mean that compilation results are now getting cached and
>  compilation is no longer executed separately for each worker thread in a
>  parallel query ?

Thanks for starting the conversation.

> I don't know, but just want to chime in with my experience 
> with PG-12 and JIT: Execution-time is still way worse then JIT=off for your 
> queries so we'll turn JIT=off until we can mesure performance-gain.

That's also been my consistent experience and conclusion.

I gather the presumption has been that JIT will be enabled by default..
..but perhaps this is a "Decision to Recheck Mid-Beta" (?)

Justin