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