Should I expect this kind of completion?

Suppose it's a Rails 3 project and I am coding up a migration. I am in the self.up method and I do:
-     change_table :codes do |t|
      t.remove_col<Ctrl+Space>

and nothing happens. Should I expect RM to help complete it?

Interestingly, when I do Ctrl+Alt+Shift+N to search the "symbol" remove_column, the completion works and the candidates are shown in the popup.
Why not in the editor?

-Kedar