Github user gatorsmile commented on a diff in the pull request:
https://github.com/apache/spark/pull/15513#discussion_r85061116
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/windowExpressions.scala
---
@@ -410,13 +418,21 @@ case class Lead(input: Expression, offset:
Expression, default: Expression)
* @param offset rows to jump back in the partition.
* @param default to use when the offset row does not exist.
*/
-@ExpressionDescription(usage =
- """_FUNC_(input, offset, default) - LAG returns the value of 'x' at the
'offset'th row
- before the current row in the window.
- The default value of 'offset' is 1 and the default value of 'default'
is null.
- If the value of 'x' at the 'offset'th row is null, null is returned.
- If there is no such offset row (e.g. when the offset is 1, the first
row of the window
- does not have any previous row), 'default' is returned.""")
+@ExpressionDescription(
+ usage = """
+ _FUNC_(input[, offset[, default]]) - Returns the value of 'x' at the
'offset'th row
+ before the current row in the window.
+ The default value of 'offset' is 1 and the default value of
'default' is null.
+ If the value of 'x' at the 'offset'th row is null, null is returned.
+ If there is no such offset row (e.g. when the offset is 1, the first
row of the window
+ does not have any previous row), 'default' is returned.
+ """,
+ extended = """
+ Arguments:
+ input - an expression of any type.
+ offset - a numeric expression. Default is 1.
+ default - an expression of any type. Defualt is NULL.
--- End diff --
Be consistent with the function description. `NULL` -> `null`
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