vlsi commented on a change in pull request #2187:
URL: https://github.com/apache/calcite/pull/2187#discussion_r502822288
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File path:
core/src/main/java/org/apache/calcite/plan/volcano/VolcanoPlanner.java
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@@ -906,6 +903,60 @@ void rename(RelNode rel) {
}
}
+ /**
+ * Checks whether a relexp has made any subset cheaper, and if it so,
+ * propagate new cost to parent rel nodes.
+ *
+ * @param rel Relational expression whose cost has improved
+ */
+ void propagateCostImprovements(RelNode rel) {
+ RelMetadataQuery mq = rel.getCluster().getMetadataQuery();
+ Map<RelNode, RelOptCost> propagateRels = new HashMap<>();
+ PriorityQueue<RelNode> propagateHeap = new PriorityQueue<>((o1, o2) -> {
+ RelOptCost c1 = propagateRels.get(o1);
+ RelOptCost c2 = propagateRels.get(o2);
+ if (c1.equals(c2)) {
+ return 0;
+ } else if (c1.isLt(c2)) {
+ return -1;
+ }
+ return 1;
+ });
+ propagateRels.put(rel, getCost(rel, mq));
+ propagateHeap.offer(rel);
+
+ while (!propagateHeap.isEmpty()) {
+ RelNode relNode = propagateHeap.poll();
+ RelOptCost cost = propagateRels.get(relNode);
+
+ for (RelSubset subset : getSet(relNode).subsets) {
+ if (relNode.getTraitSet().satisfies(subset.getTraitSet())) {
+ // Update subset best cost when we find a cheaper rel or the current
+ // best's cost is changed
+ if (cost.isLt(subset.bestCost)) {
+ subset.timestamp++;
+ LOGGER.trace("Subset cost changed: subset [{}] cost was {} now {}",
+ subset, subset.bestCost, cost);
+
+ subset.bestCost = cost;
+ subset.best = relNode;
+ // since best was changed, cached metadata for this subset should
be removed
+ mq.clearCache(subset);
+
+ subset.getParents().forEach(parent -> {
Review comment:
`forEach` ends with `});` which is slightly less nice than `}`
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