Re: Defer selection of asynchronous subplans until the executor initialization stage

On Tue, Apr 19, 2022 at 2:01 AM Etsuro Fujita <etsuro(dot)fujita(at)gmail(dot)com>
wrote:

> Hi,
>
> On Sun, Apr 17, 2022 at 7:30 PM Zhihong Yu <zyu(at)yugabyte(dot)com> wrote:
> > On Sun, Apr 17, 2022 at 1:48 AM Etsuro Fujita <etsuro(dot)fujita(at)gmail(dot)com>
> wrote:
> >> I think we might support more cases in the switch statement in the
> >> future. My concern about your proposal is that it might make it hard
> >> to add new cases to the statement. I agree that what I proposed has a
> >> bit of redundant code, but writing code inside each case independently
> >> would make it easy to add them, making code consistent across branches
> >> and thus making back-patching easy.
>
> > When a new case arises where the plan is not a Result node, this func
> can be rewritten.
> > If there is only one such new case, the check at the beginning of the
> func can be tuned to exclude that case.
>
> Sorry, I don't agree with you.
>
> > I still think the check should be lifted to the beginning of the func
> (given the current cases).
>
> The given path isn't limited to SubqueryScanPath, ForeignPath and
> ProjectionPath, so another concern is extra cycles needed when the
> path is other path type that is projection-capable (e.g., Path for
> sequential scan, IndexPath, NestPath, ...). Assume that the given
> path is a Path (that doesn't contain pseudoconstant quals). In that
> case the given SeqScan plan node wouldn't contain a gating Result
> node, so if we put the if test at the top of the function, we need to
> execute not only the test but the switch statement for the given
> path/plan nodes. But if we put the if test inside each case block, we
> only need to execute the switch statement, without executing the test.
> In the latter case I think we can save cycles for normal cases.
>
> In short: I don't think it's a great idea to put the if test at the
> top of the function.
>
> Best regards,
> Etsuro Fujita
>
Hi,
It is okay to keep the formation in your patch.

Cheers