beliefer commented on a change in pull request #29604: URL: https://github.com/apache/spark/pull/29604#discussion_r489124118
########## File path: sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/windowExpressions.scala ########## @@ -549,6 +549,96 @@ case class CumeDist() extends RowNumberLike with SizeBasedWindowFunction { override def prettyName: String = "cume_dist" } +/** + * The NthValue function returns the value of `input` at the `offset`th row from beginning of the + * window frame. Offset starts at 1. When the value of `input` is null at the `offset`th row or + * there is no such an `offset`th row, null is returned. + */ +@ExpressionDescription( + usage = """ + _FUNC_(input[, offset]) - Returns the value of `input` at the row that is the `offset`th row + from beginning of the window frame. Offsets start at 1. If the value of `input` at the + `offset`th row is null, null is returned. If there is no such an offset row (e.g., when the + offset is 10, size of the window frame less than 10), null is returned. + """, + arguments = """ + Arguments: + * input - the target column or expression that the function operates on. + * offset - an int expression which determines the row number relative to the first row in Review comment: OK ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: us...@infra.apache.org --------------------------------------------------------------------- To unsubscribe, e-mail: reviews-unsubscr...@spark.apache.org For additional commands, e-mail: reviews-h...@spark.apache.org