Github user cloud-fan commented on a diff in the pull request: https://github.com/apache/spark/pull/18113#discussion_r150083215 --- Diff: sql/core/src/main/scala/org/apache/spark/sql/execution/aggregate/typedaggregators.scala --- @@ -26,43 +26,64 @@ import org.apache.spark.sql.expressions.Aggregator // This file defines internal implementations for aggregators. //////////////////////////////////////////////////////////////////////////////////////////////////// +class TypedSumDouble[IN](val f: IN => Double) + extends Aggregator[IN, java.lang.Double, java.lang.Double] { + + override def zero: java.lang.Double = null + override def reduce(b: java.lang.Double, a: IN): java.lang.Double = + if (b == null) f(a) else b + f(a) + + override def merge(b1: java.lang.Double, b2: java.lang.Double): java.lang.Double = { + if (b1 == null) { + b2 + } else if (b2 == null) { + b1 + } else { + b1 + b2 + } + } + override def finish(reduction: java.lang.Double): java.lang.Double = reduction -class TypedSumDouble[IN](val f: IN => Double) extends Aggregator[IN, Double, Double] { - override def zero: Double = 0.0 --- End diff -- so we will return 0.0 for empty input, let's not change this behavior
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