Computed Column <str> in table <str> is invalid - drop cascade

  Explanation:  When you DROP an object and specify CASCADE, SQL
  drops or marks as invalid objects referencing it.  Any computed
  column in another table that references the dropped table, is
  now invalid.  This informational message indicates the column
  that was affected.

  User Action:  Rollback the DROP ...  CASCADE operation or
  redefined the missing object.