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https://issues.apache.org/jira/browse/SPARK-18251?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15677396#comment-15677396
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Cheng Lian commented on SPARK-18251:
------------------------------------
I'd prefer option 1 because of consistency of the semantics, and I don't think
this is really a bug since {{Option\[T\]}} shouldn't be used as top level
{{Dataset}} types anyway.
While doing schema inference, Catalyst always treats {{Option\[T\]}} as the
nullable version of {{T'}}, where {{T'}} is the inferred data type of {{T}}.
Take {{case class A(i: Option\[Int\])}} as an example, if we go for option 2,
then what should the inferred schema of {{A}} be? To keep the original
semantics, it should be
{noformat}
new StructType()
.add("i", IntegerType, nullable = true)
{noformat}
while option 2 requires
{noformat}
new StructType()
.add("i", new StructType()
.add("value", IntegerType, nullable = true), nullable = true)
{noformat}
since now {{Option\[T\]}} is treated as a single field struct.
Option 1 keeps the current semantics, which is pretty clear and easy to reason
about, while option 2 either introduce inconsistency or requires further
special casing schema inference for top level {{Dataset}} types.
> DataSet API | RuntimeException: Null value appeared in non-nullable field
> when holding Option Case Class
> --------------------------------------------------------------------------------------------------------
>
> Key: SPARK-18251
> URL: https://issues.apache.org/jira/browse/SPARK-18251
> Project: Spark
> Issue Type: Bug
> Components: Spark Core
> Affects Versions: 2.0.1
> Environment: OS X
> Reporter: Aniket Bhatnagar
>
> I am running into a runtime exception when a DataSet is holding an Empty
> object instance for an Option type that is holding non-nullable field. For
> instance, if we have the following case class:
> case class DataRow(id: Int, value: String)
> Then, DataSet[Option[DataRow]] can only hold Some(DataRow) objects and cannot
> hold Empty. If it does so, the following exception is thrown:
> {noformat}
> Exception in thread "main" org.apache.spark.SparkException: Job aborted due
> to stage failure: Task 6 in stage 0.0 failed 1 times, most recent failure:
> Lost task 6.0 in stage 0.0 (TID 6, localhost): java.lang.RuntimeException:
> Null value appeared in non-nullable field:
> - field (class: "scala.Int", name: "id")
> - option value class: "DataSetOptBug.DataRow"
> - root class: "scala.Option"
> If the schema is inferred from a Scala tuple/case class, or a Java bean,
> please try to use scala.Option[_] or other nullable types (e.g.
> java.lang.Integer instead of int/scala.Int).
> at
> org.apache.spark.sql.catalyst.expressions.GeneratedClass$GeneratedIterator.agg_doAggregateWithoutKey$(Unknown
> Source)
> at
> org.apache.spark.sql.catalyst.expressions.GeneratedClass$GeneratedIterator.processNext(Unknown
> Source)
> at
> org.apache.spark.sql.execution.BufferedRowIterator.hasNext(BufferedRowIterator.java:43)
> at
> org.apache.spark.sql.execution.WholeStageCodegenExec$$anonfun$8$$anon$1.hasNext(WholeStageCodegenExec.scala:370)
> at scala.collection.Iterator$$anon$11.hasNext(Iterator.scala:408)
> at
> org.apache.spark.shuffle.sort.BypassMergeSortShuffleWriter.write(BypassMergeSortShuffleWriter.java:125)
> at
> org.apache.spark.scheduler.ShuffleMapTask.runTask(ShuffleMapTask.scala:79)
> at
> org.apache.spark.scheduler.ShuffleMapTask.runTask(ShuffleMapTask.scala:47)
> at org.apache.spark.scheduler.Task.run(Task.scala:86)
> at org.apache.spark.executor.Executor$TaskRunner.run(Executor.scala:274)
> 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)
> {noformat}
> The bug can be reproduce by using the program:
> https://gist.github.com/aniketbhatnagar/2ed74613f70d2defe999c18afaa4816e
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