in src/main/scala/org/apache/spark/sql/datasketches/theta/aggregate/ThetaSketchAggBuild.scala [149:157]
override def merge(wrapper: ThetaSketchWrapper, other: ThetaSketchWrapper): ThetaSketchWrapper = {
if (other.compactSketch.isDefined) {
if (wrapper.union.isEmpty) {
wrapper.union = Some(SetOperation.builder().setLogNominalEntries(lgK).setSeed(seed).setP(p).buildUnion())
}
wrapper.union.get.union(other.compactSketch.get)
}
wrapper
}