Re: [v9.5] Custom Plan API

> > So it seems reasonable to have a way to define/declare what is
> > possible and what is not. But my take is that adding a new column to
> > pg_operator for every CustomJoin node is probably out of the question,
> > hence my suggestion to list the operators we know it can work with.
>
> It does seem like there should be some work done in this area, as Tom mentioned,
> to avoid needing to have more columns to track how equality can be done.
> I do wonder just how we'd deal with this when it comes to GPUs as, presumably,
> the code to implement the equality for various types would have to be written
> in CUDA-or-whatever.
>
GPU has workloads likes and dislikes. It is a reasonable idea to list up
operators (or something else) that have advantage to run on custom-path.
For example, numeric calculation on fixed-length variables has greate
advantage on GPU, but locale aware text matching is not a workload suitable
to GPUs.
It may be a good hint for planner to pick up candidate paths to be considered.

Thanks,
--
NEC OSS Promotion Center / PG-Strom Project
KaiGai Kohei <kaigai@ak.jp.nec.com>