相关源代码：
/**
* Builds a map of the columns contained in a result
*
* @param PDOStatement $results
* @return void
*/
public function resultSet($results) {
 $this->map = array();
 $numFields = $results->columnCount();
 $index = 0;
 
while ($numFields-- > 0) {
 $column = $results->getColumnMeta($index);
 if (empty($column['native_type'])) {
 $type = ($column['len'] == 1) ? 'boolean' : 'string';
 } else {
 $type = $column['native_type'];
 }
 if (!empty($column['table']) && strpos($column['name'], $this->virtualFieldSeparator) === false) {
 $this->map[$index++] = array($column['table'], $column['name'], $type);
 } else {
 $this->map[$index++] = array(0, $column['name'], $type);
 }
 }
}