Github user marmbrus commented on a diff in the pull request:
https://github.com/apache/spark/pull/3109#discussion_r20688112
--- Diff: sql/hive/src/main/scala/org/apache/spark/sql/hive/hiveUdfs.scala
---
@@ -162,9 +161,8 @@ private[hive] case class
HiveGenericUdf(functionClassName: String, children: Seq
(udfType != null && udfType.deterministic())
}
- override def foldable = {
- isUDFDeterministic && children.foldLeft(true)((prev, n) => prev &&
n.foldable)
- }
+ override def foldable =
+ isUDFDeterministic &&
returnInspector.isInstanceOf[ConstantObjectInspector]
--- End diff --
I don't really understand all the contracts here, so please correct me if
I'm missing something, but why does the return type have to be a Constant? It
seems like if a UDF is deterministic it should be safe to fold as long as its
children are foldable too, independent of the type of inspector it returns.
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