public function getTableColumns($tableName) {
        if (!$this->tableColumns){
            if (App::get()->cacheExists('mpf:PDOConnection:tableColumns')){
                $this->tableColumns = App::get()->cacheValue('mpf:PDOConnection:tableColumns');
            }
        }
        if (!isset($this->tableColumns[$tableName])) {
            $this->tableColumns[$tableName] = $this->queryAssoc("SHOW COLUMNS FROM `$tableName`");
            App::get()->cacheSet('mpf:PDOConnection:tableColumns', $this->tableColumns);
        }
        return $this->tableColumns[$tableName];
    }