Re: [v9.5] Custom Plan API

* Simon Riggs (simon(at)2ndQuadrant(dot)com) wrote:
> On 8 May 2014 14:40, Stephen Frost <sfrost(at)snowman(dot)net> wrote:
> > Allow me to re-state your suggestion here:
> >
> > An FDW is loaded which provides hook for join push-down (whatever those
> > end up being).
> >
> > A query is run which joins *local* table A to *local* table B. Standard
> > heaps, standard indexes, all local to this PG instance.
> >
> > The FDW which supports join push-down is then passed this join for
> > planning, with local sub-plans for the local tables.
>
> Yes that is correct; thank you for confirming your understanding with me.

I guess for my part, that doesn't look like an FDW any more.

> That also supports custom join of local to non-local table, or custom
> join of two non-local tables.

Well, we already support these, technically, but the FDW
doesn't actually implement the join, it's done in core.

> If we can use interfaces that already exist with efficiency, why
> invent a new one?

Perhaps once we have a proposal for FDW join push-down this will make
sense, but I'm not seeing it right now.

> >> Have we considered having an Optimizer and Executor plugin that does
> >> this without touching core at all?
> >
> > Uh, isn't that what we're talking about?
>
> No. I meant writing this as an extension rather than a patch on core.

KaiGai's patches have been some changes to core and then an extension
which uses those changes. The changes to core include exposing internal
functions for extensions to use, which will undoubtably end up being a
sore spot and fragile.

Thanks,

Stephen