Github user highfei2011 commented on a diff in the pull request:
https://github.com/apache/spark/pull/18841#discussion_r131522381
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/mathExpressions.scala
---
@@ -170,29 +193,29 @@ case class Pi() extends LeafMathExpression(math.Pi,
"PI")
// scalastyle:off line.size.limit
@ExpressionDescription(
- usage = "_FUNC_(expr) - Returns the inverse cosine (a.k.a. arccosine) of
`expr` if -1<=`expr`<=1 or NaN otherwise.",
+ usage = "_FUNC_(expr) - Returns the inverse cosine (a.k.a. arccosine) of
`expr` if -1<=`expr`<=1 or NULL otherwise.",
extended = """
Examples:
> SELECT _FUNC_(1);
0.0
> SELECT _FUNC_(2);
- NaN
+ NULL
--- End diff --
NaN represents a variety of meanings, and Null is a special case, then we
need to modify?
Personally think that may not be necessary. @viirya do you think?
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