'Oracle refuses to change a column type from/to LOB to/from a regular
column. In Django, this shows up when the field is changed from/to
a TextField.
What we need to do instead is:
- Rename the original column
- Add the desired field as new
- Update the table to transfer values from old to new
- Drop old column'

def _alter_column_lob_workaround(self, table_name, name, field):

    renamed = self._generate_temp_name(name)
    self.rename_column(table_name, name, renamed)
    self.add_column(table_name, name, field, keep_default=False)
    self.execute(('UPDATE    %s    set    %s=%s' % (self.quote_name(table_name), self.quote_name(name), self.quote_name(renamed))))
    self.delete_column(table_name, renamed)
