Thread: postgresql13-llvm jit-13.5-1PGDG.rhel8.x86_64
I was trying to upgrade my test 13.4 instance on Oracle Linux 8.4 (x86_64) to 13.5. I can't upgrade postgresql13-llvm jit because Oracle's and Red Hat repositories still don't have the required version of llvm (12.1.0.2): root@postgres mgogala]# rpm -qa|grep llvm llvm-libs-11.0.1-2.0.1.module+el8.4.0+20397+f876858a.x86_64 llvm7.0-libs-7.0.1-7.el8.x86_64 llvm-test-11.0.1-2.0.1.module+el8.4.0+20397+f876858a.x86_64 llvm-11.0.1-2.0.1.module+el8.4.0+20397+f876858a.x86_64 llvm-static-11.0.1-2.0.1.module+el8.4.0+20397+f876858a.x86_64 llvm-devel-11.0.1-2.0.1.module+el8.4.0+20397+f876858a.x86_64 [root@postgres mgogala]# I am getting the following error: postgresql13-llvm jit-13.5-1PGDG.rhel8.x86_64 requires libLLVM-12.so()(64bit), but none of the providers can be installed. 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 Now, the question is whether anyone on this list can quantify the difference? What would be a better option? To wait for the repos to receive the necessary packages or to run without llvm-jit? In the office I have some rather large databases and CREATE INDEX CONCURRENTLY and REINDEX CONCURRENTLY fixes in 13.5 are highly desired but not at the cost of the overall application performance. Regards -- Mladen Gogala Database Consultant Tel: (347) 321-1217 https://dbwhisperer.wordpress.com
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
--
Mladen Gogala
Database Consultant
Tel: (347) 321-1217
https://dbwhisperer.wordpress.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.htmlWhen 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.RegardsPavel
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
On Mon, Nov 15, 2021 at 8:57 AM Mladen Gogala <gogala.mladen@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.htmlWhen 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.RegardsPavelThanks 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)