Github user yhuai commented on a diff in the pull request:
https://github.com/apache/spark/pull/7841#discussion_r44500352
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/Analyzer.scala
---
@@ -248,6 +253,38 @@ class Analyzer(
}
}
+ object ResolvePivot extends Rule[LogicalPlan] {
+ def apply(plan: LogicalPlan): LogicalPlan = plan transform {
+ case p: Pivot if !p.childrenResolved => p
+ case Pivot(groupByExprs, pivotColumn, pivotValues, aggregates,
child) =>
+ val singleAgg = aggregates.size == 1
+ val pivotAggregates: Seq[NamedExpression] = pivotValues.flatMap{
value =>
+ aggregates.map{ aggregate =>
+ val filteredAggregate = aggregate.transformDown{
+ case u: UnaryExpression if
u.isInstanceOf[AggregateExpression] =>
+ u.withNewChildren(Seq(
+ If(EqualTo(pivotColumn, Literal(value)), u.child,
Literal(null))
+ ))
+ case other: AggregateExpression =>
+ throw new AnalysisException(
+ s"Pivot does not support non unary aggregate
expressions, found $other")
+ }
+ if (filteredAggregate.fastEquals(aggregate)) {
+ throw new AnalysisException(
+ s"Unary aggregate expression required for pivot, found
'$aggregate'")
+ }
--- End diff --
It is not super obvious why we may hit here. Can we add an example?
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