Re: is JIT available

> On Jul 25, 2020, at 8:21 AM, Pavel Stehule  wrote:
> 
> 
> 
> so 25. 7. 2020 v 14:04 odesílatel Scott Ribe  napsal:
> > On Jul 24, 2020, at 9:55 PM, Pavel Stehule  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 in EXPLAIN, 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 'EXPLAIN ANALYZE 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 Postgres doesn’t complain, but that doesn’t mean it’s actually enabled.

Cheers
Philip