Re: Query is over 2x slower with jit=on

> On Aug 22, 2018, at 2:58 PM, Andreas Joseph Krogh <andreas(at)visena(dot)com> wrote:
>
> På onsdag 22. august 2018 kl. 20:52:05, skrev Andres Freund <andres(at)anarazel(dot)de <mailto:andres(at)anarazel(dot)de>>:
> On 2018-08-22 19:51:12 +0200, Andreas Joseph Krogh wrote:
> > I thought JITing of prepared queries happended once (in "prepare")
>
> No, it happens when the first JITed function is executed.
>
>
> > so it didn't have to do the JITing every time the query is
> > executed. Isn't the previously generated bytecode usable for
> > subsequent queries?
>
> No, not currently. There's some reasons preventing that (primarily that
> we currently rely on addresses of certain things not to change during
> execution). There's ongoing work to change that, but that's certainly
> not going to be ready for v11.
>
> Greetings,
>
> Andres Freund
>
>
> Ok, thanks for clarifying.

Per earlier note[1] I was able to reproduce this issue with similar results to
Andreas while running 11 Beta 3.

jit = on
https://explain.depesz.com/s/vgzD <https://explain.depesz.com/s/vgzD>

Planning Time: 0.921 ms
JIT:
Functions: 193
Generation Time: 121.595 ms
Inlining: false
Inlining Time: 0.000 ms
Optimization: false
Optimization Time: 58.045 ms
Emission Time: 1201.100 ms
Execution Time: 1628.017 ms

jit = off
https://explain.depesz.com/s/AvZM <https://explain.depesz.com/s/AvZM>

Planning Time: 1.398 ms
Execution Time: 256.473 ms

I increased the the search range I used in the query by 3x, and got these numbers:

jit=on
Planning Time: 0.931 ms
JIT:
Functions: 184
Generation Time: 126.587 ms
Inlining: true
Inlining Time: 98.865 ms
Optimization: true
Optimization Time: 20518.982 ms
Emission Time: 7270.963 ms
Execution Time: 28772.576 ms

jit=off
Planning Time: 1.527 ms
Execution Time: 959.160 ms

So, I would +1 this for open items.

Jonathan

[1] https://www.postgresql.org/message-id/7F838324-064B-4A24-952C-2800CFBD39D6%40postgresql.org <https://www.postgresql.org/message-id/7F838324-064B-4A24-952C-2800CFBD39D6@postgresql.org>