From: Mladen Gogala <gogala.mladen@gmail.com>
To: Pavel Stehule <pavel.stehule@gmail.com>
Cc: Pgsql Performance <pgsql-performance@lists.postgresql.org>
Subject: Re: postgresql13-llvm jit-13.5-1PGDG.rhel8.x86_64
Date: Mon, 15 Nov 2021 08:56:54 -0500
Message-ID: <17b31073-a676-9133-0219-4b2e42c347a4@gmail.com> (raw)
In-Reply-To: <CAFj8pRBis=j4fLepacisTxVO=vW2JcquwZk8u98AHKkLRGMhcQ@mail.gmail.com>
References: <86fccf60-1281-b81b-4c42-5a1ef8b032ab@gmail.com>
<CAFj8pRBis=j4fLepacisTxVO=vW2JcquwZk8u98AHKkLRGMhcQ@mail.gmail.com>
On 11/15/21 00:04, Pavel Stehule wrote:
>
> Hi
>
>
> There is a CentOS8-stream version which solves the problem but I
> cannot
> use that in the office. I will probably have to wait for another
> month
> before OL8 has everything that I need in its repositories. Now, the
> question is what kind of an impact will running without llvm-jit
> have?
> According to the links below, llvm-jit effects are quite spectacular:
>
> https://llvm.org/devmtg/2016-09/slides/Melnik-PostgreSQLLLVM.pdf
>
> https://www.pgcon.org/2017/schedule/events/1092.en.html
>
>
> When JIT was used on very large query with a lot of CASE expr, then
> JIT has a positive effect about 50%. On usual large queries, the
> effect of JIT was about 20%. Unfortunately, JIT is sensitive to
> estimation, and the JIT sometimes increases seconds to queries,
> although without JIT this query is executed in ms. When you use a
> query that can be well calculated in parallel, then positive effect of
> JIT is less.
>
> Regards
>
> Pavel
Thanks Pavel, you answered my question. I'll wait with the upgrade.
Regards
--
Mladen Gogala
Database Consultant
Tel: (347) 321-1217
https://dbwhisperer.wordpress.com
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To: pgsql-performance@postgresql.org
Cc: gogala.mladen@gmail.com, pavel.stehule@gmail.com, pgsql-performance@lists.postgresql.org
Subject: Re: postgresql13-llvm jit-13.5-1PGDG.rhel8.x86_64
In-Reply-To: <17b31073-a676-9133-0219-4b2e42c347a4@gmail.com>
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