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Spark Dataframe Query not working

I have been trying to make the following Dataframe query work but its not giving me the results. Can someone please help?

Is there a reference guide to see all the syntax to create dataframe queries? Here this is what I want - My dataframe df has many cols among which 4 are -

  1. id
  2. deviceFlag
  3. device
  4. domain

For all rows, if deviceFlag is set to 1, then form a string "device#domain" and store that value in a new col "id". Else, just take the value in the "device" col and store it in the new "id" col without any transformation. So I am creating a new column with the .withColumn and setting value for each row depending upon the corresponding values of "device" and "deviceFlag" cols in that row.

DataFrame result= df.withColumn("id",
    ((Column) when(df.col("deviceFlag").$eq$eq$eq(1),
        concat(df.col("device"), lit("#"),
            df.col("domain")))).otherwise(df.col("device")).alias("id"));
12 REPLIES 12

I am getting a NPE as below

df is a dataframe that I have from previous joins with other dataframes

DataFrame df = df1.join(....)


// On doing tis I get the following NPE
df.withColumn("id",
        ((Column) when(df.col("deviceFlag").$eq$eq$eq(1),
            concat(df.col("device"), lit("#"),
            df.col("domain")))).otherwise(df.col("device")).alias("id")).show();

The line 235 in ApplDriver is 
df.col("domain")))).otherwise(df.col("device")).alias("id")).show();

I have checked some input values of domain and device and they are coming fine. NPE tells me its expecting some object? But cols are there, "id" is anyway a new col so its not defined earlier and df is ofcourse the resulting DF from prev steps..Then what can cause the NPE? Its not going forward because of the NPE.

17/02/07 15:39:18 ERROR ApplicationMaster: User class threw exception: java.lang.NullPointerException
java.lang.NullPointerException
	at com.Driver.ApplDriver.lambda$main$1acd672$1(ApplDriver.java:235)
	at org.apache.spark.streaming.api.java.JavaDStreamLike$$anonfun$foreachRDD$3.apply(JavaDStreamLike.scala:335)
	at org.apache.spark.streaming.api.java.JavaDStreamLike$$anonfun$foreachRDD$3.apply(JavaDStreamLike.scala:335)
	at org.apache.spark.streaming.dstream.DStream$$anonfun$foreachRDD$1$$anonfun$apply$mcV$sp$3.apply(DStream.scala:661)
	at org.apache.spark.streaming.dstream.DStream$$anonfun$foreachRDD$1$$anonfun$apply$mcV$sp$3.apply(DStream.scala:661)
	at org.apache.spark.streaming.dstream.ForEachDStream$$anonfun$1$$anonfun$apply$mcV$sp$1.apply$mcV$sp(ForEachDStream.scala:50)
	at org.apache.spark.streaming.dstream.ForEachDStream$$anonfun$1$$anonfun$apply$mcV$sp$1.apply(ForEachDStream.scala:50)
	at org.apache.spark.streaming.dstream.ForEachDStream$$anonfun$1$$anonfun$apply$mcV$sp$1.apply(ForEachDStream.scala:50)
	at org.apache.spark.streaming.dstream.DStream.createRDDWithLocalProperties(DStream.scala:426)
	at org.apache.spark.streaming.dstream.ForEachDStream$$anonfun$1.apply$mcV$sp(ForEachDStream.scala:49)
	at org.apache.spark.streaming.dstream.ForEachDStream$$anonfun$1.apply(ForEachDStream.scala:49)
	at org.apache.spark.streaming.dstream.ForEachDStream$$anonfun$1.apply(ForEachDStream.scala:49)
	at scala.util.Try$.apply(Try.scala:161)
	at org.apache.spark.streaming.scheduler.Job.run(Job.scala:39)
	at org.apache.spark.streaming.scheduler.JobScheduler$JobHandler$$anonfun$run$1.apply$mcV$sp(JobScheduler.scala:227)
	at org.apache.spark.streaming.scheduler.JobScheduler$JobHandler$$anonfun$run$1.apply(JobScheduler.scala:227)
	at org.apache.spark.streaming.scheduler.JobScheduler$JobHandler$$anonfun$run$1.apply(JobScheduler.scala:227)
	at scala.util.DynamicVariable.withValue(DynamicVariable.scala:57)
	at org.apache.spark.streaming.scheduler.JobScheduler$JobHandler.run(JobScheduler.scala:226)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
	at java.lang.Thread.run(Thread.java:745)

Some more testing showed that if I just add the new col with concat, it concats the values and shows up fine. But on using when() and otherwise() it is throwing an NPE

Thanks this worked. Somehow a when() function was declared in my class returning null and hence the NPE.