cloud-fan commented on a change in pull request #29800:
URL: https://github.com/apache/spark/pull/29800#discussion_r503154755
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File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/windowExpressions.scala
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@@ -347,18 +341,51 @@ abstract class OffsetWindowFunction
val default: Expression
/**
- * (Foldable) expression that contains the number of rows between the
current row and the row
- * where the input expression is evaluated.
+ * (Foldable) expression that contains the number of rows between the
starting row (current row
+ * if isRelative=true, or the first row of the window frame otherwise) and
the row where the
+ * input expression is evaluated.
*/
- val offset: Expression
+ val offsetExpr: Expression
/**
- * Direction of the number of rows between the current row and the row where
the input expression
- * is evaluated.
+ * Direction of the number of rows between the current row or the first row
of the entire
+ * window partition and the row where the input expression is evaluated.
*/
val direction: SortDirection
- override def children: Seq[Expression] = Seq(input, offset, default)
+ /**
+ * An optional specification that indicates the offset window function
should skip null values in
+ * the determination of which row to use.
+ */
+ val ignoreNulls: Boolean
+
+ /**
+ * Whether the offset is starts with the current row. If `isRelative` is
true, `offset` means
+ * the offset is start with the current row. otherwise, the offset is starts
with the first
+ * row of the entire window frame.
+ */
+ val isRelative: Boolean = true
+
+ lazy val boundary = direction match {
+ case Ascending => offsetExpr
+ case Descending => UnaryMinus(offsetExpr) match {
+ case e: Expression if e.foldable => Literal.create(e.eval(EmptyRow),
e.dataType)
+ case o => o
+ }
+ }
+
+ lazy val fakeFrame = SpecifiedWindowFrame(RowFrame, boundary, boundary)
Review comment:
why do we call it `fake`?
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