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
