Re: [v9.5] Custom Plan API

* Robert Haas (robertmhaas(at)gmail(dot)com) wrote:
> As Stephen notes downthread, Tom has already expressed opposition to
> this idea on other threads, and I tend to agree with him, at least to
> some degree. I think the drive to use foreign data wrappers for
> PGStrom, CitusDB, and other things that aren't really foreign data
> wrappers as originally conceived is a result of the fact that we've
> got only one interface in this area that looks remotely like something
> pluggable; and so everyone's trying to fit things into the constraints
> of that interface whether it's actually a good fit or not.

Agreed.

> Unfortunately, I think what CitusDB really wants is pluggable storage,
> and what PGStrom really wants is custom paths, and I don't think
> either of those things is the same as what FDWs provide.

I'm not entirely sure that PGStrom even really "wants" custom paths.. I
believe the goal there is to be able to use GPUs to do work for us and
custom paths/pluggable plan/execution are seen as the way to do that and
not depend on libraries which are under GPL, LGPL or other licenses which
we'd object to depending on from core.

Personally, I'd love to just see CUDA or whatever support in core as a
configure option and be able to detect at start-up when the right
libraries and hardware are available and enable the join types which
could make use of that gear.

I don't like that we're doing all of this because of licenses or
whatever and would still hope to figure out a way to address those
issues but I haven't had time to go research it myself and evidently
KaiGai and others see the issues there as insurmountable, so they're
trying to work around it by creating a pluggable interface where an
extension could provide those join types.

Thanks,

Stephen