Github user viirya commented on a diff in the pull request: https://github.com/apache/spark/pull/10577#discussion_r49168529 --- Diff: sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/HiveTypeCoercion.scala --- @@ -200,41 +200,62 @@ object HiveTypeCoercion { */ object WidenSetOperationTypes extends Rule[LogicalPlan] { - private[this] def widenOutputTypes( + private def widenOutputTypes( planName: String, - left: LogicalPlan, - right: LogicalPlan): (LogicalPlan, LogicalPlan) = { - require(left.output.length == right.output.length) - - val castedTypes = left.output.zip(right.output).map { - case (lhs, rhs) if lhs.dataType != rhs.dataType => - findWiderTypeForTwo(lhs.dataType, rhs.dataType) - case other => None + children: Seq[LogicalPlan]): Seq[LogicalPlan] = { + require(children.forall(_.output.length == children.head.output.length)) + + // Get a sequence of data types, each of which is the widest type of this specific attribute + // in all the children + val castedTypes: Seq[Option[DataType]] = { + val initialTypeSeq = children.head.output.map(a => Option(a.dataType)) + children.tail.foldLeft(initialTypeSeq) { (currentOutputDataTypes, child) => + // Find the wider type if the data type of this child do not match with + // the casted data types of the already processed children + getCastedTypes(currentOutputDataTypes, child.output) + } } - def castOutput(plan: LogicalPlan): LogicalPlan = { - val casted = plan.output.zip(castedTypes).map { - case (e, Some(dt)) if e.dataType != dt => - Alias(Cast(e, dt), e.name)() - case (e, _) => e - } - Project(casted, plan) + // Add extra Project for type promotion if necessary + children.map(castOutput(_, castedTypes)) + } + + // Add Project if the data types do not match + private def castOutput( + plan: LogicalPlan, + castedTypes: Seq[Option[DataType]]): LogicalPlan = { + val casted = plan.output.zip(castedTypes).map { + case (e, Some(dt)) if e.dataType != dt => + Alias(Cast(e, dt), e.name)() + case (e, _) => e } + if (casted.exists(_.isInstanceOf[Alias])) Project(casted, plan) else plan + } - if (castedTypes.exists(_.isDefined)) { - (castOutput(left), castOutput(right)) - } else { - (left, right) + private def getCastedTypes( + typeSeq: Seq[Option[DataType]], + attrSeq: Seq[Attribute]): Seq[Option[DataType]] = { + typeSeq.zip(attrSeq).map { + case (Some(dt), ar) if dt != ar.dataType => + findWiderTypeForTwo(dt, ar.dataType) + case (Some(dt), ar) if dt == ar.dataType => Option(dt) --- End diff -- Do we need this case?
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