Copy path in Dynamic programming

Hi everybody

I am doing a modification to Dynamic programming algorithm in postgreSQL. I
want to re-use a plan of one " joinrels" for another of the same level.
For example,

if lev=5 , and let's say there are two combinations setA = {1,2,3,4,5} and
set B={6,7,8,9,10}.

I want to reuse the plan of {1.2,3,4,5} for {6,7,8,9,10}.

But for this I need to create a relation that holds all the paths for
{6,7,8,9,10}.

I cannot just copy the relation holding join paths from setA. I need to
create a new join relations using build_join_rel(). But I cannot do
add_paths_to_joinrel() because that is the default path creation procedure.
Instead I must be copying the paths of joinrel fo setA.

So what I am doing now is :
1) Access the join relation for setA = {1,2,3,4,5}.

2) Pathlist = pathlist of joinrel(A).

3) foreach path "p" in pathlist of joinrel(A){
create new path "new_p" from path "p".
left_child(new_p) = recursively copy from left child(p)
right_child(new_p) = recursively copy from right child(p).
}

4)But to do step 3 I need to know how to create pathkeys and I need to do
the copy recursively, as I am trying to copy the path tree from top to
bottom.

Errors I get in doing this:
ERROR: variable not found in subplan target lists

Please give some insight. And please discuss with me on how to go about
doing the path copy.

Thanks
Vamsi