On Sat, Nov 21, 2020 at 10:26:00AM -0600, Justin Pryzby wrote:
> On Sat, Nov 21, 2020 at 08:39:11AM +0100, Peter Eisentraut wrote:
> > On 2020-11-20 17:16, Justin Pryzby wrote:
> > > It matters if it was planned with jit but executed without jit.
> > >
> > > postgres=# DEALLOCATE p; SET jit=on; SET jit_above_cost=0; prepare p as select from generate_series(1,9); explain(format yaml) execute p; SET jit=off; explain(format yaml) execute p;
> > >
> > > Patched shows this for both explains:
> > > JIT: +
> > > Functions: 3 +
> > >
> > > Unpatched shows only in the first case.
> >
> > In this context, I don't see the point of this change. If you set jit=off
> > explicitly, then there is no need to clutter the EXPLAIN output with a bunch
> > of zeroes about JIT.
>
> I think the idea is that someone should be able to parse the YAML/XML/other
> output by writing something like a['JIT']['Functions'] rather than something
> like a.get('JIT',{}).get('Functions',0)
>
> The standard seems to be that parameters that can change during execution
> should change the *values* in the non-text output, but the *keys* should not
> disappear just because (for example) parallel workers weren't available, or
> someone (else) turned off jit. We had discussion about this earlier in the
> year:
> https://www.postgresql.org/message-id/20200728033622.GC20393@telsasoft.com
>
> (Since it's machine-readable output, Key: 0 is Consistency and Completeness,
> not Clutter.)
If there's no interest or agreement in it, we should just close it.
I have no personal need for it, but noticed it in passing.