I'm pulling an id column in from the external table and renaming it in the flattened table. I would like to set this column as the sortkey and the primary key. However, when I try to select the sortkey and primary key, the only options are the original column names from the external table (not the alias I've set). I've tried using those original column names, but I get an error because Redshift is unable to find them in the flattened table (which makes sense, given that I've renamed them). Is this a bug or am I just doing something wrong?