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Message-ID: <401ac59b-067f-28f2-547d-417ee5c49c39@gmail.com>
Date: Tue, 29 Nov 2022 09:17:48 -0500
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Subject: Re: Catching up with performance & PostgreSQL 15
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To: Alvaro Herrera <alvherre@alvh.no-ip.org>
Cc: pgsql-performance@lists.postgresql.org
References: <20221129083615.fseqfvd5svtjbrb6@alvherre.pgsql>
From: Mladen Gogala <gogala.mladen@gmail.com>
In-Reply-To: <20221129083615.fseqfvd5svtjbrb6@alvherre.pgsql>
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On 11/29/22 03:36, Alvaro Herrera wrote:
> 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.
>
Hmmm, I think I will run pgbench with and without JIT on and see the 
difference.

-- 
Mladen Gogala
Database Consultant
Tel: (347) 321-1217
https://dbwhisperer.wordpress.com

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    <div class="moz-cite-prefix">On 11/29/22 03:36, Alvaro Herrera
      wrote:<br>
    </div>
    <blockquote type="cite"
      cite="mid:20221129083615.fseqfvd5svtjbrb6@alvherre.pgsql">
      <pre class="moz-quote-pre" wrap="">On 2022-Nov-28, Mladen Gogala wrote:

</pre>
      <blockquote type="cite">
        <pre class="moz-quote-pre" wrap="">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.
</pre>
      </blockquote>
      <pre class="moz-quote-pre" wrap="">
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.

</pre>
    </blockquote>
    <p>Hmmm, I think I will run pgbench with and without JIT on and see
      the difference.<br>
    </p>
    <pre class="moz-signature" cols="72">-- 
Mladen Gogala
Database Consultant
Tel: (347) 321-1217
<a class="moz-txt-link-freetext" href="https://dbwhisperer.wordpress.com">https://dbwhisperer.wordpress.com</a>
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