On Mon, Nov 15, 2021 at 8:57 AM Mladen Gogala <gogala.mla...@gmail.com> wrote:
> > 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. > > > FWIW, there was a lively discussion on the postgresql subreddit over the weekend on JIT: https://www.reddit.com/r/PostgreSQL/comments/qtsif5/cascade_of_doom_jit_and_how_a_postgres_update_led/ (lively for that subreddit anyway)
