RE: Expose JIT counters/timing in pg_stat_statements

On Mon, Mar 07, 2022 at 01:40:34PM +0100, Magnus Hagander wrote:
>
> I wonder if there might be an interesting middle ground, or if that is
> making it too much. That is, we could have an
> Option 3:
> jit_count
> total_jit_time - for sum of functions+inlining+optimization+emission time
> min_jit_time - for sum of functions+inlining+optimization+emission time
> max_jit_time - for sum of functions+inlining+optimization+emission time
> mean_jit_time - for sum of functions+inlining+optimization+emission time
> stddev_jit_time - for sum of functions+inlining+optimization+emission time
> jit_functions
> jit_generation_time
> jit_inlining_count
> jit_inlining_time
> jit_optimization_count
> jit_optimization_time
> jit_emission_count
> jit_emission_time
>
> That is, we'd get the more detailed timings across the total time, but
> not on the details. But that might be overkill.

I also thought about it but it seems overkill.  pg_stat_statements view is
already very big, and I think that the JIT time should be somewhat stable, at
least compared to how much a query execution time can vary depending on the
parameters.  This approach would also be a bit useless if you change the
costing of underlying JIT operation.

> But -- here's an updated patched based on Option 2.

Thanks!

Code-wide, the patch looks good.  For the doc, it seems that you documented
jit_inlining_count three times rather than documenting jit_optimization_count
and jit_emission_count.

I don't think we can add tests there, and having a test for every new counter
being >= 0 seems entirely useless, however there should be a new test added for
the "oldextversions" test to make sure that there's no issue with old SQL / new
shlib compatibility.  And looking at it I see that it was already missed for
version 1.9 :(

Indeed. Fixed here.

Michael had already applied a patch that took us to 1.10 and added that test, so I've just updated it here. I don't think we normally bump the version twice int he same day, so I just mergd the SQL script changes as well.

PFA a "final" version for the CI to run.