Add p_names field to ParseNamespaceItem
ParseNamespaceItem had a wired-in assumption that p_rte->eref
describes the table and column aliases exposed by the nsitem. This
relaxes this by creating a separate p_names field in an nsitem. This
is mainly preparation for a patch for JOIN USING aliases, but it saves
one indirection in common code paths, so it's possibly a win on its
own.
Author: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://www.postgresql.org/message-id/785329.
1616455091@sss.pgh.pa.us