Re: Tid scan improvements

On Thu, 4 Jul 2019 at 15:43, David Rowley <david(dot)rowley(at)2ndquadrant(dot)com> wrote:
> On Mon, 1 Jul 2019 at 23:29, Thomas Munro <thomas(dot)munro(at)gmail(dot)com> wrote:
> > The new CF is here. I'm going through poking threads for submissions
> > that don't apply, but it sounds like this needs more than a rebase?
> > Perhaps this belongs in the next CF?
>
> 0001 and 0004 of v7 got pushed in PG12. The CFbot will be trying to
> apply 0001 still, but on testing 0002, no joy there either.
>
> It would be good to see this back in PG13. For now, I'll mark it as
> waiting on author.

Hi,

I'm not really sure how to proceed. I started with a fairly pragmatic
solution to "WHERE ctid > ? AND ctid < ?" for tables, and then tableam
came along.

The options I see are:

A. Continue to target only heapam tables, making the bare minimum
changes necessary for the new tableam api.
B. Try to do something more general that works on all tableam
implementations for which it may be useful.

There may not be much different between them, but B. means a bit more
research into zheap, zstore and other possible tableams.

Next question, how will the executor access the table?

1. Continue to use the seqscan tableam methods, by setting limits.
2. Use the bitmap scan methods, for instance by faking a BitmapIteratorResuit.
3. Add new tableam methods specially for scanning a range of TIDs.

Any thoughts?