ecxt_scantuple has wrong TupleDesc

Hi all,

I wonder why my ecxt_scantuple has a TupleDesc matching the subplan's tlist, not my plan's tlist. Basically, my question is what is x in

econtext->ecxt_scantuple = x ?

I have written a new executor node Foo, with corresponding ExecFoo and make_foo functions. I have also written a new Expr type called Bar, along with a ExecEvalBar.

In make_foo I append some Bar columns. When I try to evaluate the Bar columns in ExecFoo via ExecProject, I need the Bar columns to access each other.

But sadly, the ecxt_scantuple doesn't have any Bar columns because it has a TupleDesc from the subplan.

What are the steps I have to take to make sure I can access my Bar columns (which only exist in Foo) in ExecEvalBar? Where do I get a TupleTableSlot with the desired TupleDesc from?

I'll be happy to provide more information, if needed.

Regards
Peter