ALTER TABLE ALTER COLUMN RENAME TO concurrently
It would be nice to be able to rename columns without breaking applications. Renaming is already a low overhead operation for the database however it's impossible to atomically update applications requiring users to jump through crazy hoops such as creating a new column and copying all the data over then changing the application, then dropping the old column.
It would be nice if you could do something like
ALTER TABLE ADD col ALIAS FOR old_col
which would allow either name to refer to the same column. Then after the application was updated
ALTER TABLE DROP old_col
would complete the normal rename without all the headaches.
or perhaps something like
ALTER TABLE ALTER col BEGIN RENAME TO new_col