Github user kiszk commented on a diff in the pull request:
https://github.com/apache/spark/pull/17302#discussion_r106916774
--- Diff:
sql/core/src/main/scala/org/apache/spark/sql/execution/ExistingRDD.scala ---
@@ -70,7 +70,20 @@ object RDDConversions {
object ExternalRDD {
def apply[T: Encoder](rdd: RDD[T], session: SparkSession): LogicalPlan =
{
- val externalRdd = ExternalRDD(CatalystSerde.generateObjAttr[T],
rdd)(session)
+ val attr = {
+ val attr = CatalystSerde.generateObjAttr[T]
--- End diff --
When `ExternalRDD.apply` calls `CatalystSerde.generateObjAttr`,
`deserializer.nullable` has not been resolved yet. In other call path to
`CatalystSerde.generateObjAttr`, `deserializer.nullable` may be already
resolved.
I think that this problem depends on the calling context. If we fix
`CatalystSerde.generateObjAttr` by using a general approach, the following
approach is possible:
1. call `deserializer.nullable` in `CatalystSerde.generateObjAttr`
2. If an exception does not occurs, use a value of `deserializer.nullable`
3. If an unresolved exception occurs, infer `nullable` based on
`deserializer.dataType`
Is this OK with you instead of modifying `ExternalRDD.apply()`?
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