```
val columnName=Seq("col1","col2",....."coln");

```

Is there a way to do dataframe.select operation to get dataframe containing only the column names specified . 
I know I can do `dataframe.select("col1","col2"...)`
but the `columnName`is generated at runtime.
I could do `dataframe.select()` repeatedly for each column name in a loop.Will it have any performance overheads?. Is there any other simpler way to accomplish this?