Github user jianqiao commented on a diff in the pull request:
https://github.com/apache/incubator-quickstep/pull/73#discussion_r73078969
--- Diff: query_optimizer/rules/SwapProbeBuild.cpp ---
@@ -0,0 +1,72 @@
+#include "query_optimizer/rules/SwapProbeBuild.hpp"
+
+#include <cstddef>
+#include <vector>
+
+#include "query_optimizer/cost_model/StarSchemaSimpleCostModel.hpp"
+#include "query_optimizer/expressions/AttributeReference.hpp"
+#include "query_optimizer/physical/HashJoin.hpp"
+#include "query_optimizer/physical/PatternMatcher.hpp"
+#include "query_optimizer/physical/Physical.hpp"
+#include "query_optimizer/physical/TopLevelPlan.hpp"
+#include "query_optimizer/rules/Rule.hpp"
+
+
+namespace quickstep {
+namespace optimizer {
+
+P::PhysicalPtr SwapProbeBuild::applyToNode(const P::PhysicalPtr &input) {
+ P::HashJoinPtr hash_join;
+
+ if (P::SomeHashJoin::MatchesWithConditionalCast(input, &hash_join)) {
+ P::PhysicalPtr left = hash_join->left();
+ P::PhysicalPtr right = hash_join->right();
+
+ P::TopLevelPlanPtr top_level;
+ if (P::SomeTopLevelPlan::MatchesWithConditionalCast(input,
&top_level)) {
--- End diff --
`input` should be already a `HashJoinPtr` here due to the outer `if`
statement.
In fact, `BottomUpRule` does not provide a place for initializing
`cost_model_`. One solution is to add an `initialization()` virtual method in
`class BottomUpRule`, and implement that method in `SwapProbeBuild`.
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