[GitHub] [iotdb] lancelly commented on a diff in pull request #8683: Fix bug in last query

[GitBox <gi...@apache.org>]

lancelly commented on code in PR #8683:
URL: https://github.com/apache/iotdb/pull/8683#discussion_r1059728166


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server/src/main/java/org/apache/iotdb/db/mpp/plan/planner/distribution/SourceRewriter.java:
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@@ -525,13 +528,46 @@ public List<PlanNode> visitLastQuery(LastQueryNode node, DistributionPlanContext
     PlanNode root = processRawMultiChildNode(node, context);
     if (context.queryMultiRegion) {
       PlanNode newRoot = genLastQueryRootNode(node, context);
+      // add sort op for each if we add LastQueryMergeNode as root
+      if (newRoot instanceof LastQueryMergeNode && node.getMergeOrderParameter().isEmpty()) {
+        OrderByParameter orderByParameter =
+            new OrderByParameter(
+                Collections.singletonList(new SortItem(SortKey.TIMESERIES, Ordering.ASC)));
+        addSortForEachLastQueryNode(root, orderByParameter);
+      }
       root.getChildren().forEach(newRoot::addChild);
       return Collections.singletonList(newRoot);
     } else {
       return Collections.singletonList(root);
     }
   }
 
+  private void addSortForEachLastQueryNode(PlanNode root, OrderByParameter orderByParameter) {
+    if (root instanceof LastQueryNode) {

Review Comment:
   It's possible that the children of LastQueryNode are still LastQueryNodes and these children won't be handled by this method.
   <img width="798" alt="截屏2023-01-01 17 30 24" src="https://user-images.githubusercontent.com/108499334/210166400-3c6728ea-c73d-4893-8a63-526ae68c7c54.png">
   
   



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