Analyze plan of foreign data wrapper

Hello!

I'am writing a foreign data wrapper. To avoid returning data for a column that is not used, I parse 'targetlist' and 'qual' of the Plan.

I'am able to find Var nodes but I can't figure out how i could now if this node is related to a column my foreign table.

I guess that the field 'location' is the solution but I don't understand how to use it to retrieve target table oid and column index.

I hope someone could help me.

Thanks in advance