[GitHub] [calcite] chunweilei commented on a change in pull request #1966: [CALCITE-3981] Volcano.register should not return stale/merged subset

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

chunweilei commented on a change in pull request #1966:
URL: https://github.com/apache/calcite/pull/1966#discussion_r422464778



##########
File path: core/src/main/java/org/apache/calcite/plan/volcano/VolcanoPlanner.java
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@@ -717,9 +718,10 @@ public RelOptCost getCost(RelNode rel, RelMetadataQuery mq) {
   public RelSubset getSubset(RelNode rel) {
     assert rel != null : "pre: rel != null";
     if (rel instanceof RelSubset) {
-      return (RelSubset) rel;
+      return canonize((RelSubset) rel);
     } else {
-      return mapRel2Subset.get(rel);
+      RelSubset s = mapRel2Subset.get(rel);
+      return s == null ? null : canonize(s);
     }

Review comment:
       I am wondering if we can add some tests. Maybe it is diffcult. 




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