NobiGo commented on code in PR #3851:
URL: https://github.com/apache/calcite/pull/3851#discussion_r1676837040
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core/src/main/java/org/apache/calcite/plan/volcano/VolcanoPlanner.java:
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@@ -982,11 +982,17 @@ void propagateCostImprovements(RelNode rel) {
if (!relNode.getTraitSet().satisfies(subset.getTraitSet())) {
continue;
}
- if (!cost.isLt(subset.bestCost)) {
+
+ // Update subset best and best's cost when we find a cheaper rel
+ if (relNode != subset.best && !cost.isLt(subset.bestCost)) {
continue;
}
- // Update subset best cost when we find a cheaper rel or the current
- // best's cost is changed
+
+ // Update the current best's cost when we find cost is changed
+ if (relNode == subset.best && cost.equals(subset.bestCost)) {
Review Comment:
Hi @YiwenWu , This is because RelSet's one of the subset find a cheaper
rel's cost, We need to update the parents the best rel and best cost. In
theory, this cost will become smaller, But according to the debug info, The SQL
I added in the JdbcAdapterTest shows same rel node 's cost sometimes will
become bigger. So I update it.
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