public function createIndex($indexName, $tableName, $columns)
    {
        
        $sql = 'CREATE INDEX ' . $indexName . ' ON ' . $tableName . ' (';
        $colsSql = array();
        foreach ($columns as $n => $l){
            // $n = name, $l = length
            if (!empty($l)){
                $colsSql[] =  $n . '(' . $l . ')';
            }
            else{
                $colsSql[] =  $n ;
            }
        }
    
        $colsSql = implode(',', $colsSql);
        $sql .= $colsSql . ')';
    
        $this->getDriver()->exec($sql);
        
    }