Spark Scala Window extend result until the end - scala

Question

I will expose my problem based on the initial dataframe and the one I want to achieve:
val df_997 = Seq [(Int, Int, Int, Int)]((1,1,7,10),(1,10,4,300),(1,3,14,50),(1,20,24,70),(1,30,12,90),(2,10,4,900),(2,25,30,40),(2,15,21,60),(2,5,10,80)).toDF("policyId","FECMVTO","aux","IND_DEF").orderBy(asc("policyId"), asc("FECMVTO"))
df_997.show
+--------+-------+---+-------+
|policyId|FECMVTO|aux|IND_DEF|
+--------+-------+---+-------+
| 1| 1| 7| 10|
| 1| 3| 14| 50|
| 1| 10| 4| 300|
| 1| 20| 24| 70|
| 1| 30| 12| 90|
| 2| 5| 10| 80|
| 2| 10| 4| 900|
| 2| 15| 21| 60|
| 2| 25| 30| 40|
+--------+-------+---+-------+
Imagine I have partitioned this DF by the column policyId and created the column row_num based on it to better see the Windows:
val win = Window.partitionBy("policyId").orderBy("FECMVTO")
val df_998 = df_997.withColumn("row_num",row_number().over(win))
df_998.show
+--------+-------+---+-------+-------+
|policyId|FECMVTO|aux|IND_DEF|row_num|
+--------+-------+---+-------+-------+
| 1| 1| 7| 10| 1|
| 1| 3| 14| 50| 2|
| 1| 10| 4| 300| 3|
| 1| 20| 24| 70| 4|
| 1| 30| 12| 90| 5|
| 2| 5| 10| 80| 1|
| 2| 10| 4| 900| 2|
| 2| 15| 21| 60| 3|
| 2| 25| 30| 40| 4|
+--------+-------+---+-------+-------+
Now, for each window, if the value of aux is 4, I want to set the value of IND_DEF column for that register to the column FEC_MVTO for this register on until the end of the window.
The resulting DF would be:
+--------+-------+---+-------+-------+
|policyId|FECMVTO|aux|IND_DEF|row_num|
+--------+-------+---+-------+-------+
| 1| 1| 7| 10| 1|
| 1| 3| 14| 50| 2|
| 1| 300| 4| 300| 3|
| 1| 300| 24| 70| 4|
| 1| 300| 12| 90| 5|
| 2| 5| 10| 80| 1|
| 2| 900| 4| 900| 2|
| 2| 900| 21| 60| 3|
| 2| 900| 30| 40| 4|
+--------+-------+---+-------+-------+
Thanks for your suggestions as I am very stuck in here...

Answer 1

Here's one approach: First left-join the DataFrame with its aux == 4 filtered version, followed by applying Window function first to backfill nulls with the wanted IND_DEF values per partition, and finally conditionally recreate column FECMVTO:
import org.apache.spark.sql.expressions.Window
import org.apache.spark.sql.functions._
import spark.implicits._
val df = Seq(
(1,1,7,10), (1,10,4,300), (1,3,14,50), (1,20,24,70), (1,30,12,90),
(2,10,4,900), (2,25,30,40), (2,15,21,60), (2,5,10,80)
).toDF("policyId","FECMVTO","aux","IND_DEF")
val win = Window.partitionBy("policyId").orderBy("FECMVTO").
rowsBetween(Window.unboundedPreceding, 0)
val df2 = df.
select($"policyId", $"aux", $"IND_DEF".as("IND_DEF2")).
where($"aux" === 4)
df.join(df2, Seq("policyId", "aux"), "left_outer").
withColumn("IND_DEF3", first($"IND_DEF2", ignoreNulls=true).over(win)).
withColumn("FECMVTO", coalesce($"IND_DEF3", $"FECMVTO")).
show
// +--------+---+-------+-------+--------+--------+
// |policyId|aux|FECMVTO|IND_DEF|IND_DEF2|IND_DEF3|
// +--------+---+-------+-------+--------+--------+
// | 1| 7| 1| 10| null| null|
// | 1| 14| 3| 50| null| null|
// | 1| 4| 300| 300| 300| 300|
// | 1| 24| 300| 70| null| 300|
// | 1| 12| 300| 90| null| 300|
// | 2| 10| 5| 80| null| null|
// | 2| 4| 900| 900| 900| 900|
// | 2| 21| 900| 60| null| 900|
// | 2| 30| 900| 40| null| 900|
// +--------+---+-------+-------+--------+--------+
Columns IND_DEF2, IND_DEF3 are kept only for illustration (and can certainly be dropped).

Answer 2

#I believe below can be solution for your issue
Considering input_df is your input dataframe
//Step#1 - Filter rows with IND_DEF = 4 from input_df
val only_FECMVTO_4_df1 = input_df.filter($"IND_DEF" === 4)
//Step#2 - Filling FECMVTO value from IND_DEF for the above result
val only_FECMVTO_4_df2 = only_FECMVTO_4_df1.withColumn("FECMVTO_NEW",$"IND_DEF").drop($"FECMVTO").withColumnRenamed("FECMVTO",$"FECMVTO_NEW")
//Step#3 - removing all the records from step#1 from input_df
val input_df_without_FECMVTO_4 = input_df.except(only_FECMVTO_4_df1)
//combining Step#2 output with output of Step#3
val final_df = input_df_without_FECMVTO_4.union(only_FECMVTO_4_df2)