beliefer commented on a change in pull request #29800:
URL: https://github.com/apache/spark/pull/29800#discussion_r509933808
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File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/windowExpressions.scala
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@@ -327,25 +327,14 @@ 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
- /**
- * Default result value for the function when the `offset`th row does not
exist.
- */
- val default: Expression
Review comment:
Because for `Lead` and` Lag`, `default` is the third parameter.
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