Re: postgresql13-llvm jit-13.5-1PGDG.rhel8.x86_64

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