public function getTableInfo($tableName = null)
{
$key = $tableName === null ? $this->getDbConnection()->getConnectionString() : $tableName;
if (!isset($this->_tableInfoCache[$key])) {
$class = $this->getTableInfoClass();
$tableInfo = $tableName === null ? new $class() : $this->createTableInfo($tableName);
$this->_tableInfoCache[$key] = $tableInfo;
}
return $this->_tableInfoCache[$key];
}