Объединение данных из нескольких RDD с помощью Java

У меня есть 3 файла CSV, как показано ниже, я пытаюсь создать RDD и объединить RDD в окончательный результат, к которому я могу применить фильтры. Я не уверен, с чего начать с этим. Любые предложения, пожалуйста?

JavaRDD<String> file1 = sc.textFile("D:\\tmp\\file1.csv");
JavaRDD<String> file2 = sc.textFile("D:\\tmp\\file2.csv");
JavaRDD<String> file3 = sc.textFile("D:\\tmp\\file3.csv");

JavaRDD<String> combRDD = file1.union(file2).union(file3); //doesn't give expected output

csv file1

"user","source_ip","action","type"
"abc","10.0.0.1","login","ONE"
"xyz","10.0.1.1","login","ONE"
"abc","10.0.0.1","playing","ONE"
"def","10.1.0.1","login","ONE"

csv file2

"user","url","type"
"abc","/test","TWO"
"xyz","/wonder","TWO"

csv file3

"user","total_time","type","status"
"abc","5min","THREE","true"
"xyz","2min","THREE","fail"

Окончательный ожидаемый результат

"user","source_ip","action","type","url","total_time","status"
"abc","10.0.0.1","login","ONE","","",""
"xyz","10.0.1.1","login","ONE","","",""
"abc","10.0.0.1","playing","ONE","","",""
"def","10.1.0.1","login","ONE","","",""
"abc","","","TWO","/test","",""
"xyz","","","TWO","/wonder","",""
"abc","","","THREE","","5min","true"
"xyz","","","THREE","","2min","fail"

Каждый из файлов csv генерируется каждый день в одном и том же формате, поэтому я хотел бы читать их из определенной папки с * .csv для создания RDD.