Re: is JIT available

> On Jul 25, 2020, at 8:21 AM, Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com> wrote:
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> so 25. 7. 2020 v 14:04 odesílatel Scott Ribe <scott_ribe(at)elevated-dev(dot)com> napsal:
> > On Jul 24, 2020, at 9:55 PM, Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com> wrote:
> >
> > SELECT * FROM pg_config;
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> That doesn't tell me whether or not it can actually be used.
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> It shows if Postgres was compiled with JIT support.
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> 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