Re: is JIT available

> On Jul 25, 2020, at 8:21 AM, Pavel Stehule <pavel.stehule@gmail.com> wrote:
>
>
>
> so 25. 7. 2020 v 14:04 odesílatel Scott Ribe <scott_ribe@elevated-dev.com> napsal:
> > On Jul 24, 2020, at 9:55 PM, Pavel Stehule <pavel.stehule@gmail.com> wrote:
> >
> > SELECT * FROM pg_config;
>
> That doesn't tell me whether or not it can actually be used.
>
> It shows if Postgres was compiled with JIT support.
>
> When you run EXPLAIN ANALYZE SELECT ... then you can see info about JIT overhead. If you don't see notices about JIT
inEXPLAIN, then JIT was not used. 

I like Pavel’s 'EXPLAIN ANALYZE SELECT’ suggestion a lot. I think setting jit=on and jit_above_cost=1 and then running
'EXPLAINANALYZE SELECT’ is a very effective way to see whether jit is available in practice. 

On installations where jit isn’t available (like on my Mac or on AWS Aurora), you can still set jit=on in a session and
Postgresdoesn’t complain, but that doesn’t mean it’s actually enabled. 

Cheers
Philip