Github user cloud-fan commented on a diff in the pull request:
https://github.com/apache/spark/pull/18113#discussion_r153025148
--- Diff:
sql/core/src/main/scala/org/apache/spark/sql/execution/aggregate/typedaggregators.scala
---
@@ -99,3 +94,91 @@ class TypedAverage[IN](val f: IN => Double) extends
Aggregator[IN, (Double, Long
toColumn.asInstanceOf[TypedColumn[IN, java.lang.Double]]
}
}
+
+class TypedMinDouble[IN](val f: IN => Double) extends Aggregator[IN,
Double, Double] {
+ override def zero: Double = Double.PositiveInfinity
+ override def reduce(b: Double, a: IN): Double = math.min(b, f(a))
+ override def merge(b1: Double, b2: Double): Double = math.min(b1, b2)
+ override def finish(reduction: Double): Double = {
+ if (Double.PositiveInfinity == reduction) {
--- End diff --
Actually we have 3 choices for empty input here:
1. return null and the return type is java.lang.Long
2. return Long.MinValue and return type is primitive long
3. throw exception and return type is primitive long
cc @gatorsmile @HyukjinKwon @srowen
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