Re: Introduce new multi insert Table AM and improve performance of various SQL commands with it for Heap AM

On Mon, 2024-08-26 at 23:59 +0200, Matthias van de Meent wrote:
> Specifically, I'm having trouble seeing how this could be used to
> implement ```INSERT INTO ... SELECT ... RETURNING ctid``` as I see no
> returning output path for the newly inserted tuples' data, which is
> usually required for our execution nodes' output path. Is support for
> RETURN-clauses planned for this API? In a previous iteration, the
> flush operation was capable of returning a TTS, but that seems to
> have
> been dropped, and I can't quite figure out why.

I'm not sure where that was lost, but I suspect when we changed
flushing to use a callback. I didn't get to v23-0003 yet, but I think
you're right that the current flushing mechanism isn't right for
returning tuples. Thank you.

One solution: when the buffer is flushed, we can return an iterator
over the buffered tuples to the caller. The caller can then use the
iterator to insert into indexes, return a tuple to the executor, etc.,
and then release the iterator when done (freeing the buffer). That
control flow is less convenient for most callers, though, so perhaps
that should be optional?

Regards,
    Jeff Davis