Github user hvanhovell commented on a diff in the pull request:
https://github.com/apache/spark/pull/9819#discussion_r47407885
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/windowExpressions.scala
---
@@ -120,6 +121,19 @@ sealed trait FrameBoundary {
def notFollows(other: FrameBoundary): Boolean
}
+/**
+ * Extractor for making working with frame boundaries easier.
+ */
+object FrameBoundary {
+ def apply(boundary: FrameBoundary): Option[Int] = unapply(boundary)
+ def unapply(boundary: FrameBoundary): Option[Int] = boundary match {
+ case CurrentRow => Some(0)
+ case ValuePreceding(offset) => Some(-offset)
+ case ValueFollowing(offset) => Some(offset)
+ case _ => None
--- End diff --
I don't think there is any reason to have ```UnboundedPreceding``` and
```UnboundedFollowing``` in the first place. Their position in the frame
specification should implies whether it is ```Preceding``` or ```Following```.
I would like to factor this out in a followup PR.
To answer your question: I current don't care about here position, and I
assume they cannot be reversed. I don't think the Hive parser allows this (I'll
check later).
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