I am trying to take my input data:
A B C
--------------
4 blah 2
2 3
56 foo 3
And add a column to the end based on whether B is empty or not:
A B C D
--------------------
4 blah 2 1
2 3 0
56 foo 3 1
I can do this easily by registering the input dataframe as a temp table, then typing up a SQL query.
But I'd really like to know how to do this with just Scala methods and not having to type out a SQL query within Scala.
I've tried .withColumn
, but I can't get that to do what I want.
This question is related to
scala
apache-spark
apache-spark-sql
spark-dataframe
How about something like this?
val newDF = df.filter($"B" === "").take(1) match {
case Array() => df
case _ => df.withColumn("D", $"B" === "")
}
Using take(1)
should have a minimal hit
My bad, I had missed one part of the question.
Best, cleanest way is to use a UDF
.
Explanation within the code.
// create some example data...BY DataFrame
// note, third record has an empty string
case class Stuff(a:String,b:Int)
val d= sc.parallelize(Seq( ("a",1),("b",2),
("",3) ,("d",4)).map { x => Stuff(x._1,x._2) }).toDF
// now the good stuff.
import org.apache.spark.sql.functions.udf
// function that returns 0 is string empty
val func = udf( (s:String) => if(s.isEmpty) 0 else 1 )
// create new dataframe with added column named "notempty"
val r = d.select( $"a", $"b", func($"a").as("notempty") )
scala> r.show
+---+---+--------+
| a| b|notempty|
+---+---+--------+
| a| 1| 1111|
| b| 2| 1111|
| | 3| 0|
| d| 4| 1111|
+---+---+--------+
Source: Stackoverflow.com