Coalesce in spark scala

Question

I am trying to understand if there is a default method available in Spark - scala to include empty strings in coalesce.

Ex- I have the below DF with me -

 val df2=Seq(
 ("","1"),
 ("null","15_20")
 )toDF("c1","c2")

+----+-----+
|  c1|   c2|
+----+-----+
|    |    1|
|null|15_20|
+----+-----+

The below code will work only for NULL values. But I require the coalesce to work for empty strings as well.

df2.withColumn("FirstNonNullOrBlank",coalesce(col("c1"),col("c2")))show
+----+-----+-------------------+
|  c1|   c2|FirstNonNullOrBlank|
+----+-----+-------------------+
|    |    1|                   |
|null|15_20|              15_20|
+----+-----+-------------------+

Expected Output -

+----+-----+-------------------+
|  c1|   c2|FirstNonNullOrBlank|
+----+-----+-------------------+
|    |    1|              1    |
|null|15_20|              15_20|
+----+-----+-------------------+

What should be the best approach here ?

Answer 1

you need a helper function to "nullify" these records :

def nullify(c: Column) = when(not (c==="" or c==="null"),c)

df2
  .withColumn("FirstNonNullOrBlank", coalesce(
    nullify(col("c1")),
    nullify(col("c2")))
  )
  .show

+----+-----+-------------------+
|  c1|   c2|FirstNonNullOrBlank|
+----+-----+-------------------+
|    |    1|                  1|
|null|15_20|              15_20|
+----+-----+-------------------+