Re: New Table Access Methods for Multi and Single Inserts

On Wed, 2024-03-27 at 01:19 +0530, Bharath Rupireddy wrote:
>
> Similarly, with this new AM, the onus lies on the table AM
> implementers to provide an implementation for these new AMs even if
> they just do single inserts.

Why not fall back to using the plain tuple_insert? Surely some table
AMs might be simple and limited, and we shouldn't break them just
because they don't implement the new APIs.

>
> table_multi_insert needs to be there for sure as COPY ... FROM uses
> it.

After we have these new APIs fully in place and used by COPY, what will
happen to those other APIs? Will they be deprecated or will there be a
reason to keep them?

> FWIW, I can try writing a test table AM that uses this new AM but
> just
> does single inserts, IOW, equivalent to table_tuple_insert().
> Thoughts?

More table AMs to test against would be great, but I also know that can
be a lot of work.

>
> Firstly, we are not storing CommandId and options in
> TableModifyState,
> because we expect CommandId to be changing (per Andres comment).

Trying to make this feature work across multiple commands poses a lot
of challenges: what happens when there are SELECTs and subtransactions
and non-deferrable constraints?

Regardless, if we care about multiple CIDs, they should be stored along
with the tuples, not supplied at the time of flushing.

> You mean, writes are not flushed to the disk? Can you please
> elaborate
> why it's different for INSERT INTO ... SELECT and not others? Can't
> the new flush AM be helpful here to implement any flush related
> things?

Not a major problem. We can discuss while working on IIS support.

I am concnerned that the flush callback is not a part of the API. We
will clearly need that to support index insertions for COPY/IIS, so as-
is the API feels incomplete. Thoughts?

Regards,
Jeff Davis