Re: why partition pruning doesn't work?

Robert Haas <robertmhaas(at)gmail(dot)com> writes:
> On Thu, Jun 14, 2018 at 7:23 AM, David Rowley
> <david(dot)rowley(at)2ndquadrant(dot)com> wrote:
>> However, I only spent about 10 mins looking into this, there may be
>> some giant holes in the idea. It would need much more research.

> It kind of flies in the face of the idea that a RangeTblEntry is just
> a node that can be freely copied around, serialized and deserialized,
> etc.

And also the idea that the Plan tree is read-only to the executor,
which is not a good property to give up.

> I think it would be better to keep the pointer in the RelOptInfo in
> the planner and in the EState or PlanState in the executor. Those are
> things we don't think can be copied, serialized, etc.

Yeah, RelOptInfo seems like the natural place in the planner; we might
need index relcache links in IndexOptInfo, too.

I'm less sure what to do in the executor. We already do keep open
relation pointers in PlanStates; the problem is just that it's
node-type-specific (ss_currentRelation, iss_RelationDesc, etc). Perhaps
that's unavoidable and we should just add more such fields as needed.

regards, tom lane