Re: Read-only plan trees

Tom Lane wrote:
> Right at the moment I'm struggling a bit with terminology. We've got
> basically four categories of node types to deal with in this scheme:
>
> Plan steps Expressions
> (Scan, Sort, etc) (Var, Op, Func, etc)
>
> Planner output "Plan" "Expr"?
>
> Executor state "CommonState" ???
>
> The existing Plan-category nodes are all derived from nodetype Plan,
> so that seems reasonably well set. The existing executor state nodes
> for Plan nodes are all derived from CommonState, but that seems like
> a name that conveys hardly anything. The existing expression-category
> nodes do *not* have any common substructure, and don't seem to need any.
> I'm not thrilled about using Expr as a generic term for them, but am not
> sure what else to write. (I'm also finding it confusing whether "plan
> node" means "any node in a tree output by the planner" --- which would
> then include expression nodes --- or just nodes that correspond to major
> steps in the query pipeline --- which is the present usage.) And what
> about a generic term for execution state nodes for expression nodes?
>
> Any ideas about naming are welcome.

Maybe:
Plan steps Expressions
----------------- --------------------
Planner output "Plan" "Expr"
Executor state "PlanState" "ExprState"

I think "Plan node" should only refer to nodes literally derived from nodetype
Plan. Similarly with "PlanState nodes".

Joe