Re: WIP: Upper planner pathification

On 2016-03-10 14:16:03 -0500, Tom Lane wrote:
> Andres Freund <andres@anarazel.de> writes:
> > In Citus' case a full PlannedStmt is generated on the master node, to
> > combine the data generated on worker nodes (where the bog standard
> > postgres planner is used).  It's not the only way to do things, but I
> > don't see why the approach would be entirely invalidated by the
> > pathification work.
> 
> I don't deny that you *could* continue to do things that way, but
> I dispute that it's a good idea.  Why can't you generate a Path tree
> and then ask create_plan() to convert it?

Primarily because create_plan(), and/or its children, have to know about
what you're doing; you can hide some, but not all, things below
CustomScan nodes. Secondarily, as an extension you will often have to
support several major versions.

ISTM, that there's good enough reasons to go either way; I don't see
what we're gaining by making these private. That just encourages
copy-paste coding.

Andres