> On Jul 25, 2020, at 8:21 AM, Pavel Stehule <pavel.stehule@xxxxxxxxx> wrote: > > > > so 25. 7. 2020 v 14:04 odesílatel Scott Ribe <scott_ribe@xxxxxxxxxxxxxxxx> napsal: > > On Jul 24, 2020, at 9:55 PM, Pavel Stehule <pavel.stehule@xxxxxxxxx> 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
