morrySnow commented on code in PR #63379:
URL: https://github.com/apache/doris/pull/63379#discussion_r3379396278
##########
fe/fe-core/src/main/java/org/apache/doris/nereids/trees/plans/logical/LogicalWindow.java:
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@@ -349,9 +350,18 @@ && child(0).child(0) instanceof LogicalPartitionTopN)) {
*/
public Plan pushPartitionLimitThroughWindow(WindowExpression windowFunc,
long partitionLimit, boolean hasGlobalLimit) {
- LogicalWindow<?> window = (LogicalWindow<?>) withChildren(new
LogicalPartitionTopN<>(windowFunc, hasGlobalLimit,
- partitionLimit, child(0)));
- return window;
+ // Prune order keys that repeat a partition key from the generated
PartitionTopN: they are constant within
+ // each partition, so BE does not need to sort by them. The window
above is pruned independently by the
+ // EliminateOrderByKey rule (which also benefits windows that never
become a PartitionTopN); doing the
+ // PartitionTopN side here makes it robust to rewrite ordering (the
topn may be created before the window
+ // is pruned), and both ends up consistent on the partition-key
dimension.
+ List<OrderExpression> orderKeys = windowFunc.getOrderKeys().stream()
+ .filter(orderKey ->
!windowFunc.getPartitionKeys().contains(orderKey.getOrderKey().getExpr()))
+ .collect(ImmutableList.toImmutableList());
+ LogicalPartitionTopN<Plan> partitionTopN = new
LogicalPartitionTopN<>(windowFunc.getFunction(),
+ windowFunc.getPartitionKeys(), orderKeys, hasGlobalLimit,
partitionLimit,
+ Optional.empty(), Optional.empty(), child(0));
Review Comment:
if we have prune order key in `EliminateOrderKey`, do we still need to do
same thing here?
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