protected function _updateConstraints($oldColumnName, $newColumnName)
    {
        $columnIndex = null;
        foreach ($this->_primaryKey as $index => $column) {
            if ($oldColumnName == $column->getName()) {
                $columnIndex = $index;
                break;
            }
        }
        if ($columnIndex !== null) {
            if ($newColumnName) {
                $this->_primaryKey[$columnIndex] = $this->_columns[$newColumnName];
            } else {
                unset($this->_primaryKey[$columnIndex]);
                $this->_primaryKey = array_values($this->_primaryKey);
            }
        }
    }