Spark - Sum of row values

Question

I have the following DataFrame:

January | February | March
-----------------------------
  10    |    10    |  10
  20    |    20    |  20
  50    |    50            


        

Answer 1

You were very close with this:

val newDf: DataFrame = df.select(colsToSum.map(col):_*).foreach ...

Instead, try this:

val newDf = df.select(colsToSum.map(col).reduce((c1, c2) => c1 + c2) as "sum")

I think this is the best of the the answers, because it is as fast as the answer with the hard-coded SQL query, and as convenient as the one that uses the UDF. It's the best of both worlds -- and I didn't even add a full line of code!