beliefer commented on a change in pull request #29800:
URL: https://github.com/apache/spark/pull/29800#discussion_r503782816
##########
File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/windowExpressions.scala
##########
@@ -327,38 +327,56 @@ object WindowFunctionType {
}
}
-
-/**
- * An offset window function is a window function that returns the value of
the input column offset
- * by a number of rows within the partition. For instance: an
OffsetWindowfunction for value x with
- * offset -2, will get the value of x 2 rows back in the partition.
- */
-abstract class OffsetWindowFunction
- extends Expression with WindowFunction with Unevaluable with
ImplicitCastInputTypes {
+trait OffsetWindowSpec extends Expression {
/**
* Input expression to evaluate against a row which a number of rows below
or above (depending on
- * the value and sign of the offset) the current row.
+ * the value and sign of the offset) the starting row (current row if
isRelative=true, or the
+ * first row of the window frame otherwise).
*/
val input: Expression
+ /**
+ * (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 inputOffset: Expression
+
/**
* Default result value for the function when the `offset`th row does not
exist.
*/
val default: Expression
/**
- * (Foldable) expression that contains the number of rows between the
current row and the row
- * where the input expression is evaluated.
+ * A new expression based on inputOffset, considering the direction of the
`offset`.
+ */
+ val offsetExpr: Expression
Review comment:
OK
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