public function alterColumn($table, $column, $type)
    {
        // https://github.com/Zilfsoft/Zilf2/issues/4492
        // http://www.postgresql.org/docs/9.1/static/sql-altertable.html
        if (!preg_match('/^(DROP|SET|RESET)\s+/i', $type)) {
            $type = 'TYPE ' . $this->getColumnType($type);
        }

        return 'ALTER TABLE ' . $this->db->quoteTableName($table) . ' ALTER COLUMN '
            . $this->db->quoteColumnName($column) . ' ' . $type;
    }