Zend_Db_Table_Select::isReadOnly PHP Method

    public function isReadOnly()
    {
        $readOnly = false;
        $fields = $this->getPart(Zend_Db_Table_Select::COLUMNS);
        $cols = $this->_info[Zend_Db_Table_Abstract::COLS];
        if (!count($fields)) {
            return $readOnly;
        }
        foreach ($fields as $columnEntry) {
            $column = $columnEntry[1];
            $alias = $columnEntry[2];
            if ($alias !== null) {
                $column = $alias;
            }
            switch (true) {
                case $column == self::SQL_WILDCARD:
                    break;
                case $column instanceof Zend_Db_Expr:
                case !in_array($column, $cols):
                    $readOnly = true;
                    break 2;
            }
        }
        return $readOnly;
    }