Spark Dataframes : CASE statement while using Window PARTITION function Syntax

Question

I need to check a Condition whether if ReasonCode is "YES" , then use ProcessDate as one of the PARTITION column else do not.

The equivalent SQL query is below:

SELECT PNum, SUM(SIAmt) OVER (PARTITION BY PNum,
                                           ReasonCode , 
                                           CASE WHEN ReasonCode = 'YES' THEN ProcessDate ELSE NULL END 
                              ORDER BY ProcessDate RANGE BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW) SumAmt 
from TABLE1

I have tried so far the below query, but unable to incorporate the condition

"CASE WHEN ReasonCode = 'YES' THEN ProcessDate ELSE NULL END" in Spark Dataframes

val df = inputDF.select("PNum")
.withColumn("SumAmt", sum("SIAmt").over(Window.partitionBy("PNum","ReasonCode").orderBy("ProcessDate")))

Input Data:

---------------------------------------
Pnum    ReasonCode  ProcessDate SIAmt
---------------------------------------
1       No          1/01/2016   200
1       No          2/01/2016   300
1       Yes         3/01/2016   -200
1       Yes         4/01/2016   200
---------------------------------------

Expected Output:

---------------------------------------------
Pnum    ReasonCode  ProcessDate SIAmt  SumAmt
---------------------------------------------
1       No          1/01/2016   200     200 
1       No          2/01/2016   300     500
1       Yes         3/01/2016   -200    -200
1       Yes         4/01/2016   200      200
---------------------------------------------

Any Suggestion/help on Spark dataframe instead of spark-sql query ?

Answer 1

You can apply the same exact copy of SQL in api form as

import org.apache.spark.sql.functions._
import org.apache.spark.sql.expressions._
val df = inputDF
  .withColumn("SumAmt", sum("SIAmt").over(Window.partitionBy(col("PNum"),col("ReasonCode"), when(col("ReasonCode") === "Yes", col("ProcessDate")).otherwise(null)).orderBy("ProcessDate")))

You can add the .rowsBetween(Long.MinValue, 0) part too, which should give you

+----+----------+-----------+-----+------+
|Pnum|ReasonCode|ProcessDate|SIAmt|SumAmt|
+----+----------+-----------+-----+------+
|   1|       Yes|  4/01/2016|  200|   200|
|   1|        No|  1/01/2016|  200|   200|
|   1|        No|  2/01/2016|  300|   500|
|   1|       Yes|  3/01/2016| -200|  -200|
+----+----------+-----------+-----+------+