zml1206 commented on code in PR #44145:
URL: https://github.com/apache/spark/pull/44145#discussion_r1418275721
##########
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/InferWindowGroupLimit.scala:
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@@ -68,10 +71,56 @@ object InferWindowGroupLimit extends Rule[LogicalPlan] with
PredicateHelper {
case _ => false
}
+ /**
+ * All window expressions should not have SizeBasedWindowFunction, all
lower/upper of
+ * specifiedWindowFrame is UnboundedPreceding/CurrentRow, and window
orderSpec is not foldable,
+ * so that we can safely do the early stop.
+ */
+ private def limitSupport(limit: Int, window: Window): Boolean =
+ limit <= conf.windowGroupLimitThreshold && window.child.maxRows.forall(_ >
limit) &&
+ !window.child.isInstanceOf[WindowGroupLimit] &&
+ window.orderSpec.exists(!_.foldable) &&
+
!LimitPushDownThroughWindow.supportsPushdownThroughWindow(window.windowExpressions)
&&
+ window.windowExpressions.forall {
+ case Alias(WindowExpression(windowFunction, WindowSpecDefinition(_, _,
+ SpecifiedWindowFrame(_, UnboundedPreceding, CurrentRow))), _)
+ if !windowFunction.isInstanceOf[SizeBasedWindowFunction] => true
+ case _ => false
+ }
+
+ private def isRowFrame(windowExpression: NamedExpression): Boolean =
windowExpression match {
+ case Alias(WindowExpression(_, WindowSpecDefinition(_, _,
+ SpecifiedWindowFrame(RowFrame, UnboundedPreceding, CurrentRow))), _) =>
true
+ case _ => false
+ }
+
+ private def rankLikeFunction(windowExpressions: Seq[NamedExpression]):
Expression =
+ // If windowExpressions all are RowFrame, choose SimpleLimitIterator,
+ // else RankLimitIterator to obtain enough rows for ensure data accuracy.
+ if (windowExpressions.forall(isRowFrame)) {
+ new RowNumber
+ } else {
+ new Rank
Review Comment:
They are two window.
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