View Explain Plan

[cilibar]

Hi,
I still do not entirely understand the explain plan of vertica and I was reading some documentations but still have some doubts.
First, is there a way to know the schemata of individual operations, i.e., which attributes an operation receives at its input and which sends to an output (considering that the operations can project-out existing and/or generate new attributes)?
How exactly materialize part functions? What implications this physically has? Also, in the plan for a query, are all the attributes used in the query eventually materialized?