Re: WIP: Faster Expression Processing v4

Hi,m

On 2017-03-23 17:40:55 -0400, Tom Lane wrote:
> Stylistic thought ... I am wondering if it wouldn't be a good idea
> to replace EEOP_CASE_WHEN_STEP, EEOP_CASE_THEN_STEP, EEOP_COALESCE,
> and EEOP_ARRAYREF_CHECKINPUT with instructions defined in a less
> usage-dependent way as
>
> EEOP_JUMP unconditional jump
> EEOP_JUMP_IF_NULL jump if step result is null
> EEOP_JUMP_IF_NOT_NULL jump if step result isn't null
> EEOP_JUMP_IF_NOT_TRUE jump if step result isn't TRUE
>
> One could imagine later filling out this set with the other BoolTest
> condition types, but that seems to be all we need right now.

Hm, no arguments against, but I'm also not particularly excited about
the change.

> These are basically just renamings of the step types that exist now,
> although EEOP_ARRAYREF_CHECKINPUT would have to drop its not-very-
> necessary Assert(!op->d.arrayref.state->isassignment).

I won't shed a tear about that assert's removal.

> Well, I guess I should say that they're renamings of the semantics
> that I have for these steps in my working copy; for instance, I got
> rid of casewhen.value/casewhen.isnull in favor of letting CASE WHEN
> expressions evaluate into the CASE's final output variable.

That sounds like a sensible change (in the abstract, I obviously haven't
seen your working copy).

Greetings,

Andres Freund