danny0405 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_r321990064
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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:
Why we need a decision `rel == best` ? We should always update the best rel
and cost if we found any. The problem here is that when and how this fix is
triggered, can you give more explain ?
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