Error while exploding a struct column in Spark

Question

I have a dataframe whose schema looks like this:

event: struct (nullable = true)
|    | event_category: string (nullable = true)
|    | event_name: string (n         


        

Answer 1

as the error message says, you can only explode array or map types, not struct type columns.

You can just do

df_json.withColumn("event_properties", $"event.properties")

This will generate a new column event_properties, which is also of struct-type

If you want to convert every element of the struct to a new column, then you cannot use withColumn, you need to do a select with a wildcard *:

df_json.select($"event.properties.*")

Answer 2

You may use following to flatten the struct. Explode does not work for struct as error message states.

val explodeDF = parquetDF.explode($"event") { 
case Row(properties: Seq[Row]) => properties.map{ property =>
  val errorCode = property(0).asInstanceOf[String]
  val errorDescription = property(1).asInstanceOf[String]
  Event(errorCode, errorDescription, email, salary)
 }
}.cache()
display(explodeDF)

Answer 3

You can use explode in an array or map columns so you need to convert the properties struct to array and then apply the explode function as below

import org.apache.spark.sql.functions._
df_json.withColumn("event_properties", explode(array($"event.properties.*"))).show(false)

You should have your desired requirement