Github user JamesRTaylor commented on a diff in the pull request:
https://github.com/apache/phoenix/pull/281#discussion_r153574645
--- Diff:
phoenix-core/src/main/java/org/apache/phoenix/optimize/QueryOptimizer.java ---
@@ -91,8 +91,23 @@ public QueryPlan optimize(PhoenixStatement statement,
SelectStatement select, Co
}
public QueryPlan optimize(QueryPlan dataPlan, PhoenixStatement
statement, List<? extends PDatum> targetColumns, ParallelIteratorFactory
parallelIteratorFactory) throws SQLException {
- List<QueryPlan>plans = getApplicablePlans(dataPlan, statement,
targetColumns, parallelIteratorFactory, true);
- return plans.get(0);
+ List<QueryPlan> plans = getApplicablePlans(dataPlan, statement,
targetColumns, parallelIteratorFactory, false);
+ if (plans.size() == 1) {
+ return plans.get(0);
+ }
+
+ // Get the best plan based on their costs. Costs will be ZERO if
stats are not
+ // available, thus the first plan will be returned.
+ Cost minCost = null;
+ QueryPlan bestPlan = null;
+ for (QueryPlan plan : plans) {
+ Cost cost = plan.getCost();
+ if (minCost == null || cost.compareTo(minCost) < 0) {
+ minCost = cost;
+ bestPlan = plan;
+ }
+ }
+ return bestPlan;
--- End diff --
I'm still not seeing this change. The only existing method that should
change in QueryOptimizer is this private one:
private List<QueryPlan> getApplicablePlans(QueryPlan dataPlan,
PhoenixStatement statement, List<? extends PDatum> targetColumns,
ParallelIteratorFactory parallelIteratorFactory, boolean stopAtBestPlan) throws
SQLException {
The only change necessary should be to call a new method that orders the
plans according to cost.
---
