xndai commented on a change in pull request #1440: [CALCITE-2166] Cumulative
cost of RelSubset.best RelNode is increased…
URL: https://github.com/apache/calcite/pull/1440#discussion_r321991108
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File path: core/src/main/java/org/apache/calcite/plan/volcano/RelSubset.java
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@@ -344,15 +344,29 @@ void propagateCostImprovements0(VolcanoPlanner planner,
RelMetadataQuery mq,
return;
}
try {
- final RelOptCost cost = planner.getCost(rel, mq);
- if (cost.isLt(bestCost)) {
- LOGGER.trace("Subset cost improved: subset [{}] cost was {} now {}",
this, bestCost, cost);
+ RelOptCost cost = planner.getCost(rel, mq);
+ boolean updateBest = cost.isLt(bestCost);
+
+ // Best rel's cost is increased, we need to search for new best rel
+ if (rel == best && bestCost.isLt(cost)) {
+ updateBest = true;
Review comment:
We only need to update best when its own cost is increased. If this is any
other rel node and its cost is larger than current best, we simply ignore (same
behavior as today). I think I have explained the case when this could happen.
Please check the descriptions and JIRA. Let me know if you have further
question. Thanks.
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