Describe the enhancement requested

https://github.com/apache/arrow/pull/19706/files#r1073391100 pointed out that in creating the ScanNode, we're extracting field names from Expressions in order to pass them to C++, which then makes FieldRef Expressions again. We can probably eliminate that step. Doing so may mean we need to drop a following Project step (or not, we'll have to see), and if so that means our show_query() output would change too--but if the projection doesn't show up faithfully in the print method of the ScanNode, we may want to reconsider (or, better, improve the ScanNode print).

Component(s)

R