def extract_columns(self, text):
        regex = (
            r'%(column_name)s %(data_type)s'
            r"(?: COMMENT '%(column_comment)s')?"
            r'[ss+]'
        ) % self.named_regexes
        for match in re.finditer(regex, text):
            yield {k: v for k, v in match.groupdict().items() if v is not None}