/**
  * Get resource data version
  *
  * @param string $resName
  * @return string | false
  */
 public function getDataVersion($resName)
 {
     if (!$this->_read) {
         return false;
     }
     if (is_null(self::$_dataVersions)) {
         $select = $this->_read->select()->from($this->_resTable, array('code', 'data_version'));
         self::$_dataVersions = $this->_read->fetchPairs($select);
     }
     return isset(self::$_dataVersions[$resName]) ? self::$_dataVersions[$resName] : false;
 }