Adding Key Information to Table

[bgribaudo]

Does it benefit downstream standard library functions if a table is annotated with key information?

Say my connector knows that the table it is returning has a primary key (and so unique) column. If it indicates this by calling the appropriate "add key" method, will this information potentially help standard library functions that later work with the table? Like maybe help a subsequent Table.Join decide to use a more efficient join algorithm, or help a Table.Distinct that's done over the entire table know that it is a no-op because each row contains a different key column value?

If a connector wants to provide key information, does it just need to be added to the type returned by handler GetType() but not on the table returned by GetRows()?