Re: Tid scan improvements

On Sat, 20 Jul 2019 at 06:21, Andres Freund <andres@anarazel.de> wrote:
>
> Hi,
>
> On 2019-07-19 13:54:59 +1200, David Rowley wrote:
> > Did you imagined two additional callbacks, 1 to set the TID range,
> > then one to scan it?  Duplicating the logic in heapgettup_pagemode()
> > and heapgettup() looks pretty horrible, but I guess we could add a
> > wrapper around it that loops until it gets the first tuple and bails
> > once it scans beyond the final tuple.
> >
> > Is that what you had in mind?
>
> Yea, I was thinking of something like 2.  We already have a few extra
> types of scan nodes (bitmap heap and sample scan), it'd not be bad to
> add another. And as you say, they can just share most of the guts: For
> heap I'd just implement pagemode, and perhaps split heapgettup_pagemode
> into two parts (one to do the page processing, the other to determine
> the relevant page).
>
> You say that we'd need new fields in HeapScanDescData - not so sure
> about that, it seems feasible to just provide the boundaries in the
> call? But I think it'd also just be fine to have the additional fields.

Thanks for explaining.

I've set the CF entry for the patch back to waiting on author.

I think if we get this part the way Andres would like it, then we're
pretty close.

-- 
 David Rowley                   http://www.2ndQuadrant.com/
 PostgreSQL Development, 24x7 Support, Training & Services