XieJiann commented on code in PR #16992:
URL: https://github.com/apache/doris/pull/16992#discussion_r1115453128
##########
fe/fe-core/src/main/java/org/apache/doris/nereids/NereidsPlanner.java:
##########
@@ -250,6 +252,16 @@ public Group getRoot() {
return cascadesContext.getMemo().getRoot();
}
+ private PhysicalPlan chooseNthPlan(Group rootGroup, PhysicalProperties
physicalProperties, int nthPlan) {
+ if (nthPlan == 1) {
Review Comment:
done
##########
fe/fe-core/src/main/java/org/apache/doris/nereids/memo/Memo.java:
##########
@@ -706,4 +710,172 @@ public String toString() {
}
return builder.toString();
}
+
+ /**
+ * rank all plan and select n-th plan, we write the algorithm according
paper:
+ * * Counting,Enumerating, and Sampling of Execution Plans in a
Cost-Based Query Optimizer
+ * Specifically each physical plan in memo is assigned a unique ID in
rank(). And then we sort the
+ * plan according their cost and choose the n-th plan. Note we don't
generate any physical plan in rank
+ * function.
+ *
+ * In unrank() function, we will extract the actual physical function
according the unique ID
+ */
+ public long rank(long n) {
+ Preconditions.checkArgument(n > 0, "the n %d must be greater than 0 in
nthPlan", n);
+ List<Pair<Long, Double>> plans = rankGroup(root,
PhysicalProperties.GATHER);
+ Queue<Pair<Long, Double>> rankingQueue = new PriorityQueue<>(
+ (l, r) -> -Double.compare(l.second, r.second));
+
+ for (Pair<Long, Double> plan : plans) {
+ if (rankingQueue.size() == 0 || rankingQueue.size() < n) {
+ rankingQueue.add(plan);
+ } else if (rankingQueue.peek().second > plan.second) {
+ rankingQueue.poll();
+ rankingQueue.add(plan);
+ }
+ }
+ return rankingQueue.peek().first;
+ }
+
+ private List<Pair<Long, Double>> rankGroup(Group group, PhysicalProperties
prop) {
+ List<Pair<Long, Double>> res = new ArrayList<>();
+ int prefix = res.size();
+ for (GroupExpression groupExpression :
extractGroupExpressionContainsProp(group, prop)) {
+ for (Pair<Long, Double> idCostPair :
rankGroupExpression(groupExpression, prop)) {
+ res.add(Pair.of(idCostPair.first + prefix, idCostPair.second));
+ }
+ prefix = res.size();
+ }
+ return res;
+ }
+
+ private List<Pair<Long, Double>> rankGroupExpression(GroupExpression
groupExpression,
+ PhysicalProperties prop) {
+ if (!groupExpression.getLowestCostTable().containsKey(prop)) {
+ return new ArrayList<>();
+ }
+ List<Pair<Long, Double>> res = new ArrayList<>();
+
+ List<PhysicalProperties> inputProperties =
groupExpression.getInputPropertiesList(prop);
+ if (groupExpression.getPlan() instanceof LeafPlan) {
+ res.add(Pair.of(0L, groupExpression.getCostByProperties(prop)));
+ return res;
+ }
+
+ double bestChildrenCost = 0;
+ List<List<Pair<Long, Double>>> children = new ArrayList<>();
+ for (int i = 0; i < inputProperties.size(); i++) {
+
Preconditions.checkArgument(!groupExpression.child(i).equals(groupExpression.getOwnerGroup())
+ || !prop.equals(inputProperties.get(i)));
Review Comment:
done
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