Github user jianqiao commented on a diff in the pull request:
https://github.com/apache/incubator-quickstep/pull/73#discussion_r73079256
--- Diff: query_optimizer/rules/SwapProbeBuild.hpp ---
@@ -0,0 +1,46 @@
+#ifndef QUICKSTEP_QUERY_OPTIMIZER_RULES_SWAP_PROBE_BUILD_HPP_
+#define QUICKSTEP_QUERY_OPTIMIZER_RULES_SWAP_PROBE_BUILD_HPP_
+
+#include <string>
+
+#include "query_optimizer/physical/Physical.hpp"
+#include "query_optimizer/rules/Rule.hpp"
+#include "query_optimizer/rules/BottomUpRule.hpp"
+#include "query_optimizer/cost_model/StarSchemaSimpleCostModel.hpp"
+#include "utility/Macros.hpp"
+
+namespace quickstep {
+namespace optimizer {
+
+/** \addtogroup OptimizerRules
+ * @{
+ */
+
+namespace P = ::quickstep::optimizer::physical;
+namespace E = ::quickstep::optimizer::expressions;
+namespace C = ::quickstep::optimizer::cost;
+
+/**
+ * @brief Rule that applies to a physical plan to arrange probe and
+ * build side based on the cardinalities.
+ */
+class SwapProbeBuild : public BottomUpRule<P::Physical> {
+ public:
+ SwapProbeBuild() {
+ }
+
+ std::string getName() const override { return "SwapProbeBuild"; }
+
+ protected:
+ P::PhysicalPtr applyToNode(const P::PhysicalPtr &input) override;
+
+ private:
+ DISALLOW_COPY_AND_ASSIGN(SwapProbeBuild);
+
+ std::unique_ptr<C::StarSchemaSimpleCostModel> cost_model_;
--- End diff --
Currently use `SimpleCostModel` instead of `StarSchemaSimpleCostModel` for
deciding the build/probe sides.
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