Apache Spark, add an "CASE WHEN ... ELSE ..." calculated column to an existing DataFrame
I'm trying to add an "CASE WHEN ... ELSE ..." calculated column to an existing DataFrame, using Scala APIs. Starting dataframe:
color
Red
Green
Blue
Desired dataframe (SQL syntax: CASE WHEN color == Green THEN 1 ELSE 0 END AS bool):
color bool
Red 0
Green 1
Blue 0
How should I implement this logic?
In the upcoming SPARK 1.4.0 release (should be released in the next couple of days). You can use the when/otherwise syntax:
// Create the dataframe
val df = Seq("Red", "Green", "Blue").map(Tuple1.apply).toDF("color")
// Use when/otherwise syntax
val df1 = df.withColumn("Green_Ind", when($"color" === "Green", 1).otherwise(0))
If you are using SPARK 1.3.0 you can chose to use a UDF:
// Define the UDF
val isGreen = udf((color: String) => {
if (color == "Green") 1
else 0
})
val df2 = df.withColumn("Green_Ind", isGreen($"color"))
In Spark 1.5.0: you can also use the SQL syntax expr function
val df3 = df.withColumn("Green_Ind", expr("case when color = 'green' then 1 else 0 end"))
or plain spark-sql
df.registerTempTable("data")
val df4 = sql(""" select *, case when color = 'green' then 1 else 0 end as Green_ind from data """)
I found this:
https://issues.apache.org/jira/browse/SPARK-3813
Worked for me on spark 2.1.0:
import sqlContext._
val rdd = sc.parallelize((1 to 100).map(i => Record(i, s"val_$i")))
rdd.registerTempTable("records")
println("Result of SELECT *:")
sql("SELECT case key when '93' then 'ravi' else key end FROM records").collect()