Github user wangyum commented on a diff in the pull request:
https://github.com/apache/spark/pull/18841#discussion_r131525404
--- 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 --
Spark handles some `NaN`:
https://github.com/apache/spark/blob/v2.2.0/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/mathExpressions.scala#L84
I think Spark keeps pace with the database as much as possible, otherwise
SQL migration is troublesome.
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