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

On Wed, Aug 28, 2024 at 3:14 AM Jeff Davis <pgsql@j-davis.com> wrote:
>
> On Mon, 2024-08-26 at 14:18 -0700, Jeff Davis wrote:
> > 0001 implementation issues:
> >
> > * We need default implementations for AMs that don't implement the
> > new
> > APIs, so that the AM will still function even if it only defines the
> > single-tuple APIs. If we need to make use of the AM's multi_insert
> > method (I'm not sure we do), then the default methods would need to
> > handle that as well. (I thought a previous version had these default
> > implementations -- is there a reason they were removed?)
>
> On second thought, it would be easier to just have the caller check
> whether the AM supports the multi-insert path; and if not, fall back to
> the single-tuple path. The single-tuple path is needed anyway for cases
> like before-row triggers.

Up until v21, the default implementation existed, see
https://www.postgresql.org/message-id/CALj2ACX90L5Mb5Vv%3DjsvhOdZ8BVsfpZf-CdCGhtm2N%2BbGUCSjg%40mail.gmail.com.
I then removed it in v22 to keep the code simple.

IMO, every caller branching out in the code like if (rel->rd_tableam->
tuple_modify_buffer_insert != NULL) then multi insert; else single
insert; doesn't look good. IMO, the default implementation approach
keeps things simple which eventually can be removed in *near* future.
Thoughts?

One change in the default implementation I would do from that of v21
is to assign the default AMs in GetTableAmRoutine() itself to avoid if
.. else if .. else in the table_modify_XXX().

--
Bharath Rupireddy
PostgreSQL Contributors Team
RDS Open Source Databases
Amazon Web Services: https://aws.amazon.com