Re: Changed SRF in targetlist handling

On Mon, May 23, 2016 at 4:42 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:

> "David G. Johnston" <david(dot)g(dot)johnston(at)gmail(dot)com> writes:
> > On Mon, May 23, 2016 at 4:24 PM, Alvaro Herrera <
> alvherre(at)2ndquadrant(dot)com>
> > wrote:
> >> Ah, so that's what "pipeline results" mean! I hadn't gotten that. I
> >> agree; Abhijit had a patch or a plan for this, a long time ago ...
>
> > ​Is this sidebar strictly an implementation detail, not user visible?
>
> Hmm. It could be visible in the sense that the execution of multiple
> functions in one ROWS FROM() construct could be interleaved, while
> (I think) the current implementation runs each one to completion
> serially. But if you're writing code that assumes that, I think you
> should not be very surprised when we break it. In any case, that
> would not affect the proposed translation for SRFs-in-tlist, since
> those have that behavior today.
>

Thanks

​Sounds like "zipper results" would be a better term for it...but, yes, if
that's the general context it falls into implementation from my
perspective.​

​But then I don't get Joe's point - if its an implementation detail why
should it matter if rewriting the SRF-in-tlist to be laterals changes
execution from a serial to an interleaved​ implementation. Plus, Joe's
claim: "the capability to pipeline results is still only available in the
target list", and yours above are at odds since you claim the rewritten
behavior is the same today. Is there a disconnect in knowledge or are you
talking about different things?

​David J.​