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Posted to commits@quickstep.apache.org by ji...@apache.org on 2017/04/20 22:02:54 UTC

[1/4] incubator-quickstep git commit: Add protobuf support for union all operator. [Forced Update!]

Repository: incubator-quickstep
Updated Branches:
  refs/heads/common-subexpression 255062314 -> 0fad9ec04 (forced update)


Add protobuf support for union all operator.


Project: http://git-wip-us.apache.org/repos/asf/incubator-quickstep/repo
Commit: http://git-wip-us.apache.org/repos/asf/incubator-quickstep/commit/758f07a1
Tree: http://git-wip-us.apache.org/repos/asf/incubator-quickstep/tree/758f07a1
Diff: http://git-wip-us.apache.org/repos/asf/incubator-quickstep/diff/758f07a1

Branch: refs/heads/common-subexpression
Commit: 758f07a1613e68823fab9323461fdcae56714365
Parents: 3c83c93
Author: Tianrun <Ti...@node-0.tianrun-qv23700.quickstep-pg0.wisc.cloudlab.us>
Authored: Mon Apr 17 11:03:13 2017 -0600
Committer: Tianrun <Ti...@node-2.tianrun-qv24978.quickstep-pg0.wisc.cloudlab.us>
Committed: Thu Apr 20 14:41:28 2017 -0600

----------------------------------------------------------------------
 relational_operators/CMakeLists.txt       |  1 +
 relational_operators/UnionAllOperator.cpp | 58 ++++++++++++++++++++++----
 relational_operators/UnionAllOperator.hpp | 11 ++++-
 relational_operators/WorkOrder.proto      | 10 +++++
 relational_operators/WorkOrderFactory.cpp | 40 ++++++++++++++++++
 5 files changed, 110 insertions(+), 10 deletions(-)
----------------------------------------------------------------------


http://git-wip-us.apache.org/repos/asf/incubator-quickstep/blob/758f07a1/relational_operators/CMakeLists.txt
----------------------------------------------------------------------
diff --git a/relational_operators/CMakeLists.txt b/relational_operators/CMakeLists.txt
index 4ea809b..39538ea 100644
--- a/relational_operators/CMakeLists.txt
+++ b/relational_operators/CMakeLists.txt
@@ -586,6 +586,7 @@ target_link_libraries(quickstep_relationaloperators_WorkOrderFactory
                       quickstep_relationaloperators_SortRunGenerationOperator
                       quickstep_relationaloperators_TableGeneratorOperator
                       quickstep_relationaloperators_TextScanOperator
+                      quickstep_relationaloperators_UnionAllOperator
                       quickstep_relationaloperators_UpdateOperator
                       quickstep_relationaloperators_WindowAggregationOperator
                       quickstep_relationaloperators_WorkOrder_proto

http://git-wip-us.apache.org/repos/asf/incubator-quickstep/blob/758f07a1/relational_operators/UnionAllOperator.cpp
----------------------------------------------------------------------
diff --git a/relational_operators/UnionAllOperator.cpp b/relational_operators/UnionAllOperator.cpp
index 141b3cf..1d82aef 100644
--- a/relational_operators/UnionAllOperator.cpp
+++ b/relational_operators/UnionAllOperator.cpp
@@ -65,7 +65,7 @@ void UnionAllOperator::addWorkOrdersSingleRelation(
       container->addNormalWorkOrder(
           new UnionAllWorkOrder(
               query_id_,
-              input_relations_[relation_index],
+              *input_relations_[relation_index],
               input_block_id,
               select_attribute_ids_[relation_index],
               output_destination,
@@ -75,11 +75,11 @@ void UnionAllOperator::addWorkOrdersSingleRelation(
   } else {
     std::size_t num_generated = num_workorders_generated_[relation_index];
     const std::vector<block_id> &all_blocks = input_relations_block_ids_[relation_index];
-    while (num_generated < all_blocks .size()) {
+    while (num_generated < all_blocks.size()) {
       container->addNormalWorkOrder(
           new UnionAllWorkOrder(
               query_id_,
-              input_relations_[relation_index],
+              *input_relations_[relation_index],
               all_blocks[num_generated],
               select_attribute_ids_[relation_index],
               output_destination,
@@ -124,18 +124,60 @@ bool UnionAllOperator::getAllWorkOrders(
                                    relation_index);
     }
   }
-  return stored_generated_ && done_feeding_input_relation_;
+  return done_feeding_input_relation_;
 }
 
 bool UnionAllOperator::getAllWorkOrderProtos(WorkOrderProtosContainer* container) {
-  // TODO(tianrun): Add protobuf for UnionAllWorkOrder to support distributed mode.
-  LOG(FATAL) << "UnionAllOperator is not supported in distributed mode yet.";
-  return true;
+  if (!stored_generated_) {
+    for (std::size_t relation_index = 0; relation_index < input_relations_.size(); ++relation_index) {
+      if (input_relations_are_stored_[relation_index]) {
+        const std::vector<block_id> &all_blocks = input_relations_block_ids_[relation_index];
+        const relation_id relation = input_relations_[relation_index]->getID();
+        const std::vector<attribute_id> &attributes = select_attribute_ids_[relation_index];
+        for (const block_id block : all_blocks) {
+          container->addWorkOrderProto(createWorkOrderProto(block, relation, attributes), op_index_);
+        }
+      }
+    }
+    stored_generated_ = true;
+  }
+
+  for (std::size_t relation_index = 0; relation_index < input_relations_.size(); ++relation_index) {
+    if (!input_relations_are_stored_[relation_index]) {
+      const std::vector<block_id> &all_blocks = input_relations_block_ids_[relation_index];
+      std::size_t num_generated = num_workorders_generated_[relation_index];
+      const relation_id relation = input_relations_[relation_index]->getID();
+      const std::vector<attribute_id> &attributes = select_attribute_ids_[relation_index];
+      while (num_generated < all_blocks.size()) {
+        container->addWorkOrderProto(createWorkOrderProto(all_blocks[num_generated], relation, attributes), op_index_);
+        ++num_generated;
+      }
+      num_workorders_generated_[relation_index] = num_generated;
+    }
+  }
+  return done_feeding_input_relation_;
+}
+
+serialization::WorkOrder* UnionAllOperator::createWorkOrderProto(
+    const block_id block,
+    const relation_id relation,
+    const std::vector<attribute_id> &attributes) {
+  serialization::WorkOrder *proto = new serialization::WorkOrder;
+  proto->set_work_order_type(serialization::UNION_ALL);
+  proto->set_query_id(query_id_);
+
+  proto->SetExtension(serialization::UnionAllWorkOrder::relation_id, relation);
+  proto->SetExtension(serialization::UnionAllWorkOrder::insert_destination_index, output_destination_index_);
+  proto->SetExtension(serialization::UnionAllWorkOrder::block_id, block);
+  for (const attribute_id attr : attributes) {
+    proto->AddExtension(serialization::UnionAllWorkOrder::select_attribute_id, attr);
+  }
+  return proto;
 }
 
 void UnionAllWorkOrder::execute() {
   BlockReference block(
-      storage_manager_->getBlock(input_block_id_, *input_relation_));
+      storage_manager_->getBlock(input_block_id_, input_relation_));
   block->selectSimple(select_attribute_id_,
                       nullptr,
                       output_destination_);

http://git-wip-us.apache.org/repos/asf/incubator-quickstep/blob/758f07a1/relational_operators/UnionAllOperator.hpp
----------------------------------------------------------------------
diff --git a/relational_operators/UnionAllOperator.hpp b/relational_operators/UnionAllOperator.hpp
index 3bfed82..4fc2906 100644
--- a/relational_operators/UnionAllOperator.hpp
+++ b/relational_operators/UnionAllOperator.hpp
@@ -45,6 +45,8 @@ class StorageManager;
 class WorkOrderProtosContainer;
 class WorkOrdersContainer;
 
+namespace serialization { class WorkOrder; }
+
 /** \addtogroup RelationalOperators
  *  @{
  */
@@ -149,6 +151,11 @@ class UnionAllOperator : public RelationalOperator {
                                    InsertDestination *output_destination,
                                    const std::size_t relation_index);
 
+  // Create work order proto
+  serialization::WorkOrder* createWorkOrderProto(const block_id block,
+                                                 const relation_id relation,
+                                                 const std::vector<attribute_id> &attributes);
+
   const std::vector<const CatalogRelation*> input_relations_;
   const std::vector<bool> input_relations_are_stored_;
 
@@ -194,7 +201,7 @@ class UnionAllWorkOrder : public WorkOrder {
    * @param storage_manager The StorageManager to use.
    */
   UnionAllWorkOrder(const std::size_t query_id,
-                    const CatalogRelationSchema *input_relation,
+                    const CatalogRelationSchema &input_relation,
                     const block_id input_block_id,
                     const std::vector<attribute_id> &select_attribute_id,
                     InsertDestination *output_destination,
@@ -211,7 +218,7 @@ class UnionAllWorkOrder : public WorkOrder {
   void execute() override;
 
  private:
-  const CatalogRelationSchema *input_relation_;
+  const CatalogRelationSchema &input_relation_;
   const block_id input_block_id_;
   const std::vector<attribute_id> select_attribute_id_;
 

http://git-wip-us.apache.org/repos/asf/incubator-quickstep/blob/758f07a1/relational_operators/WorkOrder.proto
----------------------------------------------------------------------
diff --git a/relational_operators/WorkOrder.proto b/relational_operators/WorkOrder.proto
index d0d0753..12a65ca 100644
--- a/relational_operators/WorkOrder.proto
+++ b/relational_operators/WorkOrder.proto
@@ -45,6 +45,7 @@ enum WorkOrderType {
   WINDOW_AGGREGATION = 21;
   DESTROY_AGGREGATION_STATE = 22;
   BUILD_AGGREGATION_EXISTENCE_MAP = 23;
+  UNION_ALL = 24;
 }
 
 message WorkOrder {
@@ -291,3 +292,12 @@ message BuildAggregationExistenceMapWorkOrder {
     optional uint32 aggr_state_index = 371;
   }
 }
+
+message UnionAllWorkOrder {
+  extend WorkOrder {
+    optional int32 relation_id = 384;
+    optional int32 insert_destination_index = 385;
+    optional fixed64 block_id = 386;
+    repeated int32 select_attribute_id = 387;
+  }
+}

http://git-wip-us.apache.org/repos/asf/incubator-quickstep/blob/758f07a1/relational_operators/WorkOrderFactory.cpp
----------------------------------------------------------------------
diff --git a/relational_operators/WorkOrderFactory.cpp b/relational_operators/WorkOrderFactory.cpp
index 56f431b..d63bb62 100644
--- a/relational_operators/WorkOrderFactory.cpp
+++ b/relational_operators/WorkOrderFactory.cpp
@@ -49,6 +49,7 @@
 #include "relational_operators/SortRunGenerationOperator.hpp"
 #include "relational_operators/TableGeneratorOperator.hpp"
 #include "relational_operators/TextScanOperator.hpp"
+#include "relational_operators/UnionAllOperator.hpp"
 #include "relational_operators/UpdateOperator.hpp"
 #include "relational_operators/WindowAggregationOperator.hpp"
 #include "relational_operators/WorkOrder.pb.h"
@@ -492,6 +493,23 @@ WorkOrder* WorkOrderFactory::ReconstructFromProto(const serialization::WorkOrder
               proto.GetExtension(serialization::TextScanWorkOrder::insert_destination_index)),
           hdfs);
     }
+    case serialization::UNION_ALL: {
+      LOG(INFO) << "Creating UnionAllWorkOrder for Query " << proto.query_id() << " in Shiftboss " << shiftboss_index;
+      vector<attribute_id> select_attribute_id;
+      for (int i = 0; i < proto.ExtensionSize(serialization::UnionAllWorkOrder::select_attribute_id); ++i) {
+        select_attribute_id.push_back(
+            proto.GetExtension(serialization::UnionAllWorkOrder::select_attribute_id, i));
+      }
+      return new UnionAllWorkOrder(
+          proto.query_id(),
+          catalog_database->getRelationSchemaById(
+              proto.GetExtension(serialization::UnionAllWorkOrder::relation_id)),
+          proto.GetExtension(serialization::UnionAllWorkOrder::block_id),
+          select_attribute_id,
+          query_context->getInsertDestination(
+              proto.GetExtension(serialization::UnionAllWorkOrder::insert_destination_index)),
+          storage_manager);
+    }
     case serialization::UPDATE: {
       LOG(INFO) << "Creating UpdateWorkOrder for Query " << proto.query_id() << " in Shiftboss " << shiftboss_index;
       return new UpdateWorkOrder(
@@ -892,6 +910,28 @@ bool WorkOrderFactory::ProtoIsValid(const serialization::WorkOrder &proto,
              query_context.isValidInsertDestinationId(
                  proto.GetExtension(serialization::TextScanWorkOrder::insert_destination_index));
     }
+    case serialization::UNION_ALL: {
+      if (!proto.HasExtension(serialization::UnionAllWorkOrder::relation_id) ||
+          !proto.HasExtension(serialization::UnionAllWorkOrder::block_id) ||
+          !proto.HasExtension(serialization::UnionAllWorkOrder::insert_destination_index) ||
+          !query_context.isValidInsertDestinationId(
+              proto.GetExtension(serialization::UnionAllWorkOrder::insert_destination_index))) {
+        return false;
+      }
+
+      const relation_id rel_id = proto.GetExtension(serialization::UnionAllWorkOrder::relation_id);
+      if (!catalog_database.hasRelationWithId(rel_id)) {
+        return false;
+      }
+      const CatalogRelationSchema &relation = catalog_database.getRelationSchemaById(rel_id);
+      for (int i = 0; i < proto.ExtensionSize(serialization::UnionAllWorkOrder::select_attribute_id); ++i) {
+        if (!relation.hasAttributeWithId(
+                 proto.GetExtension(serialization::UnionAllWorkOrder::select_attribute_id, i))) {
+          return false;
+        }
+      }
+      return true;
+    }
     case serialization::UPDATE: {
       return proto.HasExtension(serialization::UpdateWorkOrder::relation_id) &&
              catalog_database.hasRelationWithId(


[4/4] incubator-quickstep git commit: Add common-subexpression support.

Posted by ji...@apache.org.
Add common-subexpression support.


Project: http://git-wip-us.apache.org/repos/asf/incubator-quickstep/repo
Commit: http://git-wip-us.apache.org/repos/asf/incubator-quickstep/commit/0fad9ec0
Tree: http://git-wip-us.apache.org/repos/asf/incubator-quickstep/tree/0fad9ec0
Diff: http://git-wip-us.apache.org/repos/asf/incubator-quickstep/diff/0fad9ec0

Branch: refs/heads/common-subexpression
Commit: 0fad9ec0486238feedef1362a32779c417606cb1
Parents: 758f07a
Author: Jianqiao Zhu <ji...@cs.wisc.edu>
Authored: Thu Apr 20 15:28:12 2017 -0500
Committer: Jianqiao Zhu <ji...@cs.wisc.edu>
Committed: Thu Apr 20 17:02:42 2017 -0500

----------------------------------------------------------------------
 expressions/CMakeLists.txt                      |   6 +
 expressions/Expression.hpp                      |  54 ++++
 expressions/ExpressionFactories.cpp             |  11 +
 expressions/Expressions.proto                   |   8 +
 expressions/predicate/CMakeLists.txt            |   4 +-
 expressions/predicate/ComparisonPredicate.cpp   |  87 ++++--
 expressions/predicate/ComparisonPredicate.hpp   |  12 +
 expressions/predicate/NegationPredicate.cpp     |  21 ++
 expressions/predicate/NegationPredicate.hpp     |  12 +
 expressions/predicate/Predicate.cpp             |  16 ++
 expressions/predicate/Predicate.hpp             |  18 +-
 expressions/predicate/PredicateWithList.cpp     |  54 ++++
 expressions/predicate/PredicateWithList.hpp     |  11 +
 expressions/scalar/CMakeLists.txt               |  18 ++
 expressions/scalar/Scalar.cpp                   |  15 +
 expressions/scalar/Scalar.hpp                   |  40 ++-
 expressions/scalar/ScalarAttribute.cpp          |  42 ++-
 expressions/scalar/ScalarAttribute.hpp          |  22 +-
 expressions/scalar/ScalarBinaryExpression.cpp   | 251 ++++++++++-------
 expressions/scalar/ScalarBinaryExpression.hpp   |  23 +-
 expressions/scalar/ScalarCaseExpression.cpp     | 123 ++++++---
 expressions/scalar/ScalarCaseExpression.hpp     |  33 ++-
 expressions/scalar/ScalarLiteral.cpp            |  47 +++-
 expressions/scalar/ScalarLiteral.hpp            |  23 +-
 expressions/scalar/ScalarSharedExpression.cpp   | 141 ++++++++++
 expressions/scalar/ScalarSharedExpression.hpp   | 119 ++++++++
 expressions/scalar/ScalarUnaryExpression.cpp    |  82 ++++--
 expressions/scalar/ScalarUnaryExpression.hpp    |  23 +-
 query_optimizer/CMakeLists.txt                  |   3 +
 query_optimizer/PhysicalGenerator.cpp           |  14 +-
 .../expressions/AttributeReference.cpp          |  18 ++
 .../expressions/AttributeReference.hpp          |   4 +
 .../expressions/BinaryExpression.cpp            |  36 +++
 .../expressions/BinaryExpression.hpp            |   4 +
 query_optimizer/expressions/CMakeLists.txt      |  31 ++-
 query_optimizer/expressions/Cast.cpp            |  16 ++
 query_optimizer/expressions/Cast.hpp            |   4 +
 .../expressions/CommonSubexpression.cpp         |  70 +++++
 .../expressions/CommonSubexpression.hpp         | 133 +++++++++
 query_optimizer/expressions/ExpressionType.hpp  |   3 +-
 query_optimizer/expressions/ExpressionUtil.hpp  |   6 +-
 query_optimizer/expressions/NamedExpression.cpp |   2 +
 query_optimizer/expressions/NamedExpression.hpp |  13 -
 query_optimizer/expressions/PatternMatcher.hpp  |   9 +-
 query_optimizer/expressions/Scalar.hpp          |  19 ++
 query_optimizer/expressions/ScalarLiteral.cpp   |  15 +
 query_optimizer/expressions/ScalarLiteral.hpp   |   4 +
 query_optimizer/expressions/SimpleCase.cpp      |  46 ++++
 query_optimizer/expressions/SimpleCase.hpp      |   4 +
 query_optimizer/expressions/UnaryExpression.cpp |  17 ++
 query_optimizer/expressions/UnaryExpression.hpp |   6 +
 query_optimizer/rules/CMakeLists.txt            |  63 +++++
 query_optimizer/rules/CollapseSelection.cpp     |  57 ++++
 query_optimizer/rules/CollapseSelection.hpp     |  59 ++++
 .../rules/ExtractCommonSubexpression.cpp        | 264 ++++++++++++++++++
 .../rules/ExtractCommonSubexpression.hpp        | 135 +++++++++
 .../rules/ReuseAggregateExpressions.cpp         | 276 +++++++++++++++++++
 .../rules/ReuseAggregateExpressions.hpp         |  98 +++++++
 relational_operators/CMakeLists.txt             |   2 +
 relational_operators/HashJoinOperator.cpp       |  51 +++-
 .../NestedLoopsJoinOperator.cpp                 |   6 +-
 storage/AggregationOperationState.cpp           |   4 +-
 storage/CMakeLists.txt                          |   3 +
 storage/StorageBlock.cpp                        |  10 +-
 storage/WindowAggregationOperationState.cpp     |   8 +-
 types/containers/ColumnVector.hpp               |   3 +
 types/containers/ColumnVectorsValueAccessor.hpp |  24 +-
 .../binary_operations/AddBinaryOperation.hpp    |   4 +
 .../binary_operations/BinaryOperation.hpp       |   4 +
 .../MultiplyBinaryOperation.hpp                 |   4 +
 utility/CMakeLists.txt                          |   7 +
 utility/ColumnVectorCache.hpp                   |  64 +++++
 utility/HashError.hpp                           |  55 ++++
 73 files changed, 2701 insertions(+), 293 deletions(-)
----------------------------------------------------------------------


http://git-wip-us.apache.org/repos/asf/incubator-quickstep/blob/0fad9ec0/expressions/CMakeLists.txt
----------------------------------------------------------------------
diff --git a/expressions/CMakeLists.txt b/expressions/CMakeLists.txt
index b1f1fb1..33606cd 100644
--- a/expressions/CMakeLists.txt
+++ b/expressions/CMakeLists.txt
@@ -25,12 +25,16 @@ QS_PROTOBUF_GENERATE_CPP(expressions_Expressions_proto_srcs
                          expressions_Expressions_proto_hdrs
                          Expressions.proto)
 
+add_library(quickstep_expressions_Expression ../empty_src.cpp Expression.hpp)
 add_library(quickstep_expressions_ExpressionFactories
             ExpressionFactories.cpp
             ExpressionFactories.hpp)
 add_library(quickstep_expressions_Expressions_proto
             ${expressions_Expressions_proto_srcs})
 
+target_link_libraries(quickstep_expressions_Expression
+                      quickstep_utility_Macros
+                      quickstep_utility_TreeStringSerializable)
 target_link_libraries(quickstep_expressions_ExpressionFactories
                       glog
                       quickstep_catalog_CatalogDatabaseLite
@@ -48,6 +52,7 @@ target_link_libraries(quickstep_expressions_ExpressionFactories
                       quickstep_expressions_scalar_ScalarBinaryExpression
                       quickstep_expressions_scalar_ScalarCaseExpression
                       quickstep_expressions_scalar_ScalarLiteral
+                      quickstep_expressions_scalar_ScalarSharedExpression
                       quickstep_expressions_scalar_ScalarUnaryExpression
                       quickstep_types_TypeFactory
                       quickstep_types_TypedValue
@@ -64,6 +69,7 @@ target_link_libraries(quickstep_expressions_Expressions_proto
 # Module all-in-one library:
 add_library(quickstep_expressions ../empty_src.cpp ExpressionsModule.hpp)
 target_link_libraries(quickstep_expressions
+                      quickstep_expressions_Expression
                       quickstep_expressions_ExpressionFactories
                       quickstep_expressions_Expressions_proto
                       quickstep_expressions_aggregation

http://git-wip-us.apache.org/repos/asf/incubator-quickstep/blob/0fad9ec0/expressions/Expression.hpp
----------------------------------------------------------------------
diff --git a/expressions/Expression.hpp b/expressions/Expression.hpp
new file mode 100644
index 0000000..737ff19
--- /dev/null
+++ b/expressions/Expression.hpp
@@ -0,0 +1,54 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ **/
+
+#ifndef QUICKSTEP_EXPRESSIONS_EXPRESSION_HPP_
+#define QUICKSTEP_EXPRESSIONS_EXPRESSION_HPP_
+
+#include "utility/Macros.hpp"
+#include "utility/TreeStringSerializable.hpp"
+
+namespace quickstep {
+
+/** \addtogroup Expressions
+ *  @{
+ */
+
+/**
+ * @brief Base class for all expressions (i.e. scalars and predicates) in the
+ *        backend.
+ */
+class Expression : public TreeStringSerializable<const Expression*> {
+ public:
+  /**
+   * @brief Virtual destructor.
+   **/
+  virtual ~Expression() {}
+
+ protected:
+  Expression() {}
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(Expression);
+};
+
+/** @} */
+
+}  // namespace quickstep
+
+#endif  // QUICKSTEP_EXPRESSIONS_EXPRESSION_HPP_

http://git-wip-us.apache.org/repos/asf/incubator-quickstep/blob/0fad9ec0/expressions/ExpressionFactories.cpp
----------------------------------------------------------------------
diff --git a/expressions/ExpressionFactories.cpp b/expressions/ExpressionFactories.cpp
index 01d22a0..c947181 100644
--- a/expressions/ExpressionFactories.cpp
+++ b/expressions/ExpressionFactories.cpp
@@ -39,6 +39,7 @@
 #include "expressions/scalar/ScalarBinaryExpression.hpp"
 #include "expressions/scalar/ScalarCaseExpression.hpp"
 #include "expressions/scalar/ScalarLiteral.hpp"
+#include "expressions/scalar/ScalarSharedExpression.hpp"
 #include "expressions/scalar/ScalarUnaryExpression.hpp"
 #include "types/TypeFactory.hpp"
 #include "types/TypedValue.hpp"
@@ -210,6 +211,11 @@ Scalar* ScalarFactory::ReconstructFromProto(const serialization::Scalar &proto,
                                       std::move(result_expressions),
                                       else_result_expression.release());
     }
+    case serialization::Scalar::SHARED_EXPRESSION: {
+      return new ScalarSharedExpression(
+          proto.GetExtension(serialization::ScalarSharedExpression::share_id),
+          ReconstructFromProto(proto.GetExtension(serialization::ScalarSharedExpression::operand), database));
+    }
     default:
       FATAL_ERROR("Unknown Scalar data source in ScalarFactory::ReconstructFromProto");
   }
@@ -302,6 +308,11 @@ bool ScalarFactory::ProtoIsValid(const serialization::Scalar &proto,
       // Everything checks out.
       return true;
     }
+    case serialization::Scalar::SHARED_EXPRESSION: {
+      return proto.HasExtension(serialization::ScalarSharedExpression::share_id)
+             && proto.HasExtension(serialization::ScalarSharedExpression::operand);
+      break;
+    }
     default: {
       break;
     }

http://git-wip-us.apache.org/repos/asf/incubator-quickstep/blob/0fad9ec0/expressions/Expressions.proto
----------------------------------------------------------------------
diff --git a/expressions/Expressions.proto b/expressions/Expressions.proto
index 8d923c5..8b4611e 100644
--- a/expressions/Expressions.proto
+++ b/expressions/Expressions.proto
@@ -50,6 +50,7 @@ message Scalar {
     UNARY_EXPRESSION = 2;
     BINARY_EXPRESSION = 3;
     CASE_EXPRESSION = 4;
+    SHARED_EXPRESSION = 5;
   }
 
   required ScalarDataSource data_source = 1;
@@ -123,3 +124,10 @@ message ScalarCaseExpression {
     optional Scalar else_result_expression = 163;
   }
 }
+
+message ScalarSharedExpression {
+  extend Scalar {
+    optional int32 share_id = 196;
+    optional Scalar operand = 197;
+  }
+}

http://git-wip-us.apache.org/repos/asf/incubator-quickstep/blob/0fad9ec0/expressions/predicate/CMakeLists.txt
----------------------------------------------------------------------
diff --git a/expressions/predicate/CMakeLists.txt b/expressions/predicate/CMakeLists.txt
index b90562c..04abfc7 100644
--- a/expressions/predicate/CMakeLists.txt
+++ b/expressions/predicate/CMakeLists.txt
@@ -35,7 +35,7 @@ add_library(quickstep_expressions_predicate_PredicateCost
             ../../empty_src.cpp
             PredicateCost.hpp)
 add_library(quickstep_expressions_predicate_PredicateWithList
-            ../../empty_src.cpp
+            PredicateWithList.cpp
             PredicateWithList.hpp)
 add_library(quickstep_expressions_predicate_TrivialPredicates
             ../../empty_src.cpp
@@ -61,6 +61,7 @@ target_link_libraries(quickstep_expressions_predicate_ComparisonPredicate
                       quickstep_types_containers_ColumnVector
                       quickstep_types_operations_Operation_proto
                       quickstep_types_operations_comparisons_Comparison
+                      quickstep_types_operations_comparisons_ComparisonID
                       quickstep_utility_Macros
                       quickstep_utility_PtrVector)
 target_link_libraries(quickstep_expressions_predicate_ConjunctionPredicate
@@ -92,6 +93,7 @@ target_link_libraries(quickstep_expressions_predicate_NegationPredicate
                       quickstep_utility_Macros)
 target_link_libraries(quickstep_expressions_predicate_Predicate
                       quickstep_catalog_CatalogTypedefs
+                      quickstep_expressions_Expression
                       quickstep_expressions_Expressions_proto
                       quickstep_storage_StorageBlockInfo
                       quickstep_storage_TupleIdSequence

http://git-wip-us.apache.org/repos/asf/incubator-quickstep/blob/0fad9ec0/expressions/predicate/ComparisonPredicate.cpp
----------------------------------------------------------------------
diff --git a/expressions/predicate/ComparisonPredicate.cpp b/expressions/predicate/ComparisonPredicate.cpp
index 5f8612e..2f7b84b 100644
--- a/expressions/predicate/ComparisonPredicate.cpp
+++ b/expressions/predicate/ComparisonPredicate.cpp
@@ -23,6 +23,7 @@
 #include <limits>
 #include <memory>
 #include <string>
+#include <type_traits>
 #include <utility>
 #include <vector>
 
@@ -41,6 +42,7 @@
 #include "types/containers/ColumnVector.hpp"
 #include "types/operations/Operation.pb.h"
 #include "types/operations/comparisons/Comparison.hpp"
+#include "types/operations/comparisons/ComparisonID.hpp"
 #include "utility/Macros.hpp"
 #include "utility/PtrVector.hpp"
 
@@ -190,18 +192,20 @@ TupleIdSequence* ComparisonPredicate::getAllMatches(
 #endif  // QUICKSTEP_ENABLE_VECTOR_COPY_ELISION_SELECTION
 
     if (short_circuit_adapter) {
-      std::unique_ptr<ColumnVector> right_values(right_operand_->getAllValues(
+      ColumnVectorPtr right_values(right_operand_->getAllValues(
           short_circuit_adapter.get(),
-          sub_blocks_ref));
+          sub_blocks_ref,
+          nullptr /* cv_cache */));
       return fast_comparator_->compareStaticValueAndColumnVector(
           left_operand_->getStaticValue(),
           *right_values,
           nullptr,
           filter);
     } else {
-      std::unique_ptr<ColumnVector> right_values(right_operand_->getAllValues(
+      ColumnVectorPtr right_values(right_operand_->getAllValues(
           accessor,
-          sub_blocks_ref));
+          sub_blocks_ref,
+          nullptr /* cv_cache */));
       return fast_comparator_->compareStaticValueAndColumnVector(
           left_operand_->getStaticValue(),
           *right_values,
@@ -222,18 +226,20 @@ TupleIdSequence* ComparisonPredicate::getAllMatches(
 #endif  // QUICKSTEP_ENABLE_VECTOR_COPY_ELISION_SELECTION
 
     if (short_circuit_adapter) {
-      std::unique_ptr<ColumnVector> left_values(left_operand_->getAllValues(
+      ColumnVectorPtr left_values(left_operand_->getAllValues(
           short_circuit_adapter.get(),
-          sub_blocks_ref));
+          sub_blocks_ref,
+          nullptr /* cv_cache */));
       return fast_comparator_->compareColumnVectorAndStaticValue(
           *left_values,
           right_operand_->getStaticValue(),
           nullptr,
           filter);
     } else {
-      std::unique_ptr<ColumnVector> left_values(left_operand_->getAllValues(
+      ColumnVectorPtr left_values(left_operand_->getAllValues(
           accessor,
-          sub_blocks_ref));
+          sub_blocks_ref,
+          nullptr /* cv_cache */));
       return fast_comparator_->compareColumnVectorAndStaticValue(
           *left_values,
           right_operand_->getStaticValue(),
@@ -255,9 +261,10 @@ TupleIdSequence* ComparisonPredicate::getAllMatches(
                                                             filter);
       } else {
         if (short_circuit_adapter) {
-          std::unique_ptr<ColumnVector> right_values(right_operand_->getAllValues(
+          ColumnVectorPtr right_values(right_operand_->getAllValues(
               short_circuit_adapter.get(),
-              sub_blocks_ref));
+              sub_blocks_ref,
+              nullptr /* cv_cache */));
           return fast_comparator_->compareValueAccessorAndColumnVector(
               short_circuit_adapter.get(),
               left_operand_attr_id,
@@ -265,9 +272,10 @@ TupleIdSequence* ComparisonPredicate::getAllMatches(
               nullptr,
               filter);
         } else {
-          std::unique_ptr<ColumnVector> right_values(right_operand_->getAllValues(
+          ColumnVectorPtr right_values(right_operand_->getAllValues(
               accessor,
-              sub_blocks_ref));
+              sub_blocks_ref,
+              nullptr /* cv_cache */));
           return fast_comparator_->compareValueAccessorAndColumnVector(accessor,
                                                                        left_operand_attr_id,
                                                                        *right_values,
@@ -277,9 +285,10 @@ TupleIdSequence* ComparisonPredicate::getAllMatches(
       }
     } else if (right_operand_attr_id != -1) {
       if (short_circuit_adapter) {
-        std::unique_ptr<ColumnVector> left_values(left_operand_->getAllValues(
+        ColumnVectorPtr left_values(left_operand_->getAllValues(
             short_circuit_adapter.get(),
-            sub_blocks_ref));
+            sub_blocks_ref,
+            nullptr /* cv_cache */));
         return fast_comparator_->compareColumnVectorAndValueAccessor(
             *left_values,
             short_circuit_adapter.get(),
@@ -287,9 +296,10 @@ TupleIdSequence* ComparisonPredicate::getAllMatches(
             nullptr,
             filter);
       } else {
-        std::unique_ptr<ColumnVector> left_values(left_operand_->getAllValues(
+        ColumnVectorPtr left_values(left_operand_->getAllValues(
             accessor,
-            sub_blocks_ref));
+            sub_blocks_ref,
+            nullptr /* cv_cache */));
         return fast_comparator_->compareColumnVectorAndValueAccessor(*left_values,
                                                                      accessor,
                                                                      right_operand_attr_id,
@@ -300,23 +310,27 @@ TupleIdSequence* ComparisonPredicate::getAllMatches(
 #endif  // QUICKSTEP_ENABLE_VECTOR_COPY_ELISION_SELECTION
 
     if (short_circuit_adapter) {
-      std::unique_ptr<ColumnVector> left_values(left_operand_->getAllValues(
+      ColumnVectorPtr left_values(left_operand_->getAllValues(
           short_circuit_adapter.get(),
-          sub_blocks_ref));
-      std::unique_ptr<ColumnVector> right_values(right_operand_->getAllValues(
+          sub_blocks_ref,
+          nullptr /* cv_cache */));
+      ColumnVectorPtr right_values(right_operand_->getAllValues(
           short_circuit_adapter.get(),
-          sub_blocks_ref));
+          sub_blocks_ref,
+          nullptr /* cv_cache */));
       return fast_comparator_->compareColumnVectors(*left_values,
                                                     *right_values,
                                                     nullptr,
                                                     filter);
     } else {
-      std::unique_ptr<ColumnVector> left_values(left_operand_->getAllValues(
+      ColumnVectorPtr left_values(left_operand_->getAllValues(
           accessor,
-          sub_blocks_ref));
-      std::unique_ptr<ColumnVector> right_values(right_operand_->getAllValues(
+          sub_blocks_ref,
+          nullptr /* cv_cache */));
+      ColumnVectorPtr right_values(right_operand_->getAllValues(
           accessor,
-          sub_blocks_ref));
+          sub_blocks_ref,
+          nullptr /* cv_cache */));
       return fast_comparator_->compareColumnVectors(*left_values,
                                                     *right_values,
                                                     filter,
@@ -373,4 +387,29 @@ void ComparisonPredicate::initHelper(bool own_children) {
   }
 }
 
+void ComparisonPredicate::getFieldStringItems(
+    std::vector<std::string> *inline_field_names,
+    std::vector<std::string> *inline_field_values,
+    std::vector<std::string> *non_container_child_field_names,
+    std::vector<const Expression*> *non_container_child_fields,
+    std::vector<std::string> *container_child_field_names,
+    std::vector<std::vector<const Expression*>> *container_child_fields) const {
+  Predicate::getFieldStringItems(inline_field_names,
+                                 inline_field_values,
+                                 non_container_child_field_names,
+                                 non_container_child_fields,
+                                 container_child_field_names,
+                                 container_child_fields);
+
+  inline_field_names->emplace_back("comparison");
+  inline_field_values->emplace_back(
+      kComparisonNames[static_cast<std::underlying_type<ComparisonID>::type>(
+          comparison_.getComparisonID())]);
+
+  non_container_child_field_names->emplace_back("left_operand");
+  non_container_child_fields->emplace_back(left_operand_.get());
+  non_container_child_field_names->emplace_back("right_operand");
+  non_container_child_fields->emplace_back(right_operand_.get());
+}
+
 }  // namespace quickstep

http://git-wip-us.apache.org/repos/asf/incubator-quickstep/blob/0fad9ec0/expressions/predicate/ComparisonPredicate.hpp
----------------------------------------------------------------------
diff --git a/expressions/predicate/ComparisonPredicate.hpp b/expressions/predicate/ComparisonPredicate.hpp
index 9030857..1ef2cb1 100644
--- a/expressions/predicate/ComparisonPredicate.hpp
+++ b/expressions/predicate/ComparisonPredicate.hpp
@@ -21,7 +21,9 @@
 #define QUICKSTEP_EXPRESSIONS_PREDICATE_COMPARISON_PREDICATE_HPP_
 
 #include <memory>
+#include <string>
 #include <utility>
+#include <vector>
 
 #include "catalog/CatalogTypedefs.hpp"
 #include "expressions/Expressions.pb.h"
@@ -35,6 +37,7 @@
 
 namespace quickstep {
 
+class Expression;
 class TupleIdSequence;
 class ValueAccessor;
 
@@ -137,6 +140,15 @@ class ComparisonPredicate : public Predicate {
    **/
   std::pair<bool, attribute_id> getAttributeFromAttributeLiteralComparison() const;
 
+ protected:
+  void getFieldStringItems(
+      std::vector<std::string> *inline_field_names,
+      std::vector<std::string> *inline_field_values,
+      std::vector<std::string> *non_container_child_field_names,
+      std::vector<const Expression*> *non_container_child_fields,
+      std::vector<std::string> *container_child_field_names,
+      std::vector<std::vector<const Expression*>> *container_child_fields) const override;
+
  private:
   const Comparison &comparison_;
   std::unique_ptr<Scalar> left_operand_;

http://git-wip-us.apache.org/repos/asf/incubator-quickstep/blob/0fad9ec0/expressions/predicate/NegationPredicate.cpp
----------------------------------------------------------------------
diff --git a/expressions/predicate/NegationPredicate.cpp b/expressions/predicate/NegationPredicate.cpp
index bee1c8d..92a8411 100644
--- a/expressions/predicate/NegationPredicate.cpp
+++ b/expressions/predicate/NegationPredicate.cpp
@@ -19,6 +19,9 @@
 
 #include "expressions/predicate/NegationPredicate.hpp"
 
+#include <string>
+#include <vector>
+
 #include "expressions/Expressions.pb.h"
 #include "expressions/predicate/Predicate.hpp"
 #include "storage/TupleIdSequence.hpp"
@@ -120,4 +123,22 @@ Predicate* NegationPredicate::NegatePredicate(Predicate *operand) {
   }
 }
 
+void NegationPredicate::getFieldStringItems(
+    std::vector<std::string> *inline_field_names,
+    std::vector<std::string> *inline_field_values,
+    std::vector<std::string> *non_container_child_field_names,
+    std::vector<const Expression*> *non_container_child_fields,
+    std::vector<std::string> *container_child_field_names,
+    std::vector<std::vector<const Expression*>> *container_child_fields) const {
+  Predicate::getFieldStringItems(inline_field_names,
+                                 inline_field_values,
+                                 non_container_child_field_names,
+                                 non_container_child_fields,
+                                 container_child_field_names,
+                                 container_child_fields);
+
+  non_container_child_field_names->emplace_back("operand");
+  non_container_child_fields->emplace_back(operand_.get());
+}
+
 }  // namespace quickstep

http://git-wip-us.apache.org/repos/asf/incubator-quickstep/blob/0fad9ec0/expressions/predicate/NegationPredicate.hpp
----------------------------------------------------------------------
diff --git a/expressions/predicate/NegationPredicate.hpp b/expressions/predicate/NegationPredicate.hpp
index 33c6df8..ec005ea 100644
--- a/expressions/predicate/NegationPredicate.hpp
+++ b/expressions/predicate/NegationPredicate.hpp
@@ -21,6 +21,8 @@
 #define QUICKSTEP_EXPRESSIONS_PREDICATE_NEGATION_PREDICATE_HPP_
 
 #include <memory>
+#include <string>
+#include <vector>
 
 #include "catalog/CatalogTypedefs.hpp"
 #include "expressions/Expressions.pb.h"
@@ -30,6 +32,7 @@
 
 namespace quickstep {
 
+class Expression;
 class TupleIdSequence;
 class ValueAccessor;
 
@@ -105,6 +108,15 @@ class NegationPredicate : public Predicate {
 
   bool getStaticResult() const override;
 
+ protected:
+  void getFieldStringItems(
+      std::vector<std::string> *inline_field_names,
+      std::vector<std::string> *inline_field_values,
+      std::vector<std::string> *non_container_child_field_names,
+      std::vector<const Expression*> *non_container_child_fields,
+      std::vector<std::string> *container_child_field_names,
+      std::vector<std::vector<const Expression*>> *container_child_fields) const override;
+
  private:
   void initHelper();
 

http://git-wip-us.apache.org/repos/asf/incubator-quickstep/blob/0fad9ec0/expressions/predicate/Predicate.cpp
----------------------------------------------------------------------
diff --git a/expressions/predicate/Predicate.cpp b/expressions/predicate/Predicate.cpp
index 006e8f1..1f61d62 100644
--- a/expressions/predicate/Predicate.cpp
+++ b/expressions/predicate/Predicate.cpp
@@ -19,6 +19,9 @@
 
 #include "expressions/predicate/Predicate.hpp"
 
+#include <string>
+#include <vector>
+
 #include "storage/TupleIdSequence.hpp"
 #include "storage/ValueAccessor.hpp"
 #include "utility/Macros.hpp"
@@ -57,4 +60,17 @@ TupleIdSequence* Predicate::GenerateSequenceForStaticResult(
   return result;
 }
 
+void Predicate::getFieldStringItems(
+    std::vector<std::string> *inline_field_names,
+    std::vector<std::string> *inline_field_values,
+    std::vector<std::string> *non_container_child_field_names,
+    std::vector<const Expression*> *non_container_child_fields,
+    std::vector<std::string> *container_child_field_names,
+    std::vector<std::vector<const Expression*>> *container_child_fields) const {
+  if (hasStaticResult()) {
+    inline_field_names->emplace_back("static_result");
+    inline_field_values->emplace_back(getStaticResult() ? "true" : "false");
+  }
+}
+
 }  // namespace quickstep

http://git-wip-us.apache.org/repos/asf/incubator-quickstep/blob/0fad9ec0/expressions/predicate/Predicate.hpp
----------------------------------------------------------------------
diff --git a/expressions/predicate/Predicate.hpp b/expressions/predicate/Predicate.hpp
index 5fb3ef5..a7e89ef 100644
--- a/expressions/predicate/Predicate.hpp
+++ b/expressions/predicate/Predicate.hpp
@@ -20,7 +20,10 @@
 #ifndef QUICKSTEP_EXPRESSIONS_PREDICATE_PREDICATE_HPP_
 #define QUICKSTEP_EXPRESSIONS_PREDICATE_PREDICATE_HPP_
 
+#include <type_traits>
+
 #include "catalog/CatalogTypedefs.hpp"
+#include "expressions/Expression.hpp"
 #include "expressions/Expressions.pb.h"
 #include "storage/StorageBlockInfo.hpp"
 #include "utility/Macros.hpp"
@@ -39,7 +42,7 @@ struct SubBlocksReference;
 /**
  * @brief Base class for all predicates.
  **/
-class Predicate {
+class Predicate : public Expression {
  public:
   /**
    * @brief The possible types of predicates.
@@ -67,6 +70,11 @@ class Predicate {
   virtual ~Predicate() {
   }
 
+  std::string getName() const override {
+    return kPredicateTypeNames[
+        static_cast<std::underlying_type<PredicateType>::type>(getPredicateType())];
+  }
+
   /**
    * @brief Serialize this predicate in Protocol Buffer form.
    *
@@ -189,6 +197,14 @@ class Predicate {
   virtual bool getStaticResult() const;
 
  protected:
+  void getFieldStringItems(
+      std::vector<std::string> *inline_field_names,
+      std::vector<std::string> *inline_field_values,
+      std::vector<std::string> *non_container_child_field_names,
+      std::vector<const Expression*> *non_container_child_fields,
+      std::vector<std::string> *container_child_field_names,
+      std::vector<std::vector<const Expression*>> *container_child_fields) const override;
+
   Predicate() {
   }
 

http://git-wip-us.apache.org/repos/asf/incubator-quickstep/blob/0fad9ec0/expressions/predicate/PredicateWithList.cpp
----------------------------------------------------------------------
diff --git a/expressions/predicate/PredicateWithList.cpp b/expressions/predicate/PredicateWithList.cpp
new file mode 100644
index 0000000..6b3d7a7
--- /dev/null
+++ b/expressions/predicate/PredicateWithList.cpp
@@ -0,0 +1,54 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ **/
+
+#include "expressions/predicate/PredicateWithList.hpp"
+
+#include <string>
+#include <vector>
+
+namespace quickstep {
+
+void PredicateWithList::getFieldStringItems(
+    std::vector<std::string> *inline_field_names,
+    std::vector<std::string> *inline_field_values,
+    std::vector<std::string> *non_container_child_field_names,
+    std::vector<const Expression*> *non_container_child_fields,
+    std::vector<std::string> *container_child_field_names,
+    std::vector<std::vector<const Expression*>> *container_child_fields) const {
+  Predicate::getFieldStringItems(inline_field_names,
+                                 inline_field_values,
+                                 non_container_child_field_names,
+                                 non_container_child_fields,
+                                 container_child_field_names,
+                                 container_child_fields);
+
+  container_child_field_names->emplace_back("static_operand_list");
+  container_child_fields->emplace_back();
+  for (const auto &static_operand : static_operand_list_) {
+    container_child_fields->back().emplace_back(&static_operand);
+  }
+
+  container_child_field_names->emplace_back("dynamic_operand_list");
+  container_child_fields->emplace_back();
+  for (const auto &dynamic_operand : dynamic_operand_list_) {
+    container_child_fields->back().emplace_back(&dynamic_operand);
+  }
+}
+
+}  // namespace quickstep

http://git-wip-us.apache.org/repos/asf/incubator-quickstep/blob/0fad9ec0/expressions/predicate/PredicateWithList.hpp
----------------------------------------------------------------------
diff --git a/expressions/predicate/PredicateWithList.hpp b/expressions/predicate/PredicateWithList.hpp
index b1bf7e5..c6fb99d 100644
--- a/expressions/predicate/PredicateWithList.hpp
+++ b/expressions/predicate/PredicateWithList.hpp
@@ -20,6 +20,9 @@
 #ifndef QUICKSTEP_EXPRESSIONS_PREDICATE_PREDICATE_WITH_LIST_HPP_
 #define QUICKSTEP_EXPRESSIONS_PREDICATE_PREDICATE_WITH_LIST_HPP_
 
+#include <string>
+#include <vector>
+
 #include "expressions/predicate/Predicate.hpp"
 #include "utility/Macros.hpp"
 #include "utility/PtrList.hpp"
@@ -58,6 +61,14 @@ class PredicateWithList : public Predicate {
   }
 
  protected:
+  void getFieldStringItems(
+      std::vector<std::string> *inline_field_names,
+      std::vector<std::string> *inline_field_values,
+      std::vector<std::string> *non_container_child_field_names,
+      std::vector<const Expression*> *non_container_child_fields,
+      std::vector<std::string> *container_child_field_names,
+      std::vector<std::vector<const Expression*>> *container_child_fields) const override;
+
   PtrList<Predicate> static_operand_list_;
   PtrList<Predicate> dynamic_operand_list_;
 

http://git-wip-us.apache.org/repos/asf/incubator-quickstep/blob/0fad9ec0/expressions/scalar/CMakeLists.txt
----------------------------------------------------------------------
diff --git a/expressions/scalar/CMakeLists.txt b/expressions/scalar/CMakeLists.txt
index 8f509da..6b52231 100644
--- a/expressions/scalar/CMakeLists.txt
+++ b/expressions/scalar/CMakeLists.txt
@@ -29,6 +29,9 @@ add_library(quickstep_expressions_scalar_ScalarCaseExpression
 add_library(quickstep_expressions_scalar_ScalarLiteral
             ScalarLiteral.cpp
             ScalarLiteral.hpp)
+add_library(quickstep_expressions_scalar_ScalarSharedExpression
+            ScalarSharedExpression.cpp
+            ScalarSharedExpression.hpp)
 add_library(quickstep_expressions_scalar_ScalarUnaryExpression
             ScalarUnaryExpression.cpp
             ScalarUnaryExpression.hpp)
@@ -36,9 +39,11 @@ add_library(quickstep_expressions_scalar_ScalarUnaryExpression
 # Link dependencies:
 target_link_libraries(quickstep_expressions_scalar_Scalar
                       quickstep_catalog_CatalogTypedefs
+                      quickstep_expressions_Expression
                       quickstep_expressions_Expressions_proto
                       quickstep_storage_StorageBlockInfo
                       quickstep_types_TypedValue
+                      quickstep_types_containers_ColumnVector
                       quickstep_utility_Macros)
 target_link_libraries(quickstep_expressions_scalar_ScalarAttribute
                       quickstep_catalog_CatalogAttribute
@@ -65,6 +70,7 @@ target_link_libraries(quickstep_expressions_scalar_ScalarBinaryExpression
                       quickstep_types_containers_ColumnVector
                       quickstep_types_operations_Operation_proto
                       quickstep_types_operations_binaryoperations_BinaryOperation
+                      quickstep_types_operations_binaryoperations_BinaryOperationID
                       quickstep_utility_Macros)
 target_link_libraries(quickstep_expressions_scalar_ScalarCaseExpression
                       quickstep_catalog_CatalogTypedefs
@@ -92,6 +98,16 @@ target_link_libraries(quickstep_expressions_scalar_ScalarLiteral
                       quickstep_types_TypedValue_proto
                       quickstep_types_containers_ColumnVector
                       quickstep_utility_Macros)
+target_link_libraries(quickstep_expressions_scalar_ScalarSharedExpression
+                      quickstep_catalog_CatalogTypedefs
+                      quickstep_expressions_Expressions_proto
+                      quickstep_expressions_scalar_Scalar
+                      quickstep_storage_StorageBlockInfo
+                      quickstep_storage_ValueAccessor
+                      quickstep_types_TypedValue
+                      quickstep_types_containers_ColumnVector
+                      quickstep_utility_ColumnVectorCache
+                      quickstep_utility_Macros)
 target_link_libraries(quickstep_expressions_scalar_ScalarUnaryExpression
                       quickstep_catalog_CatalogTypedefs
                       quickstep_expressions_Expressions_proto
@@ -104,6 +120,7 @@ target_link_libraries(quickstep_expressions_scalar_ScalarUnaryExpression
                       quickstep_types_containers_ColumnVector
                       quickstep_types_operations_Operation_proto
                       quickstep_types_operations_unaryoperations_UnaryOperation
+                      quickstep_types_operations_unaryoperations_UnaryOperationID
                       quickstep_utility_Macros)
 
 # Submodule all-in-one library:
@@ -114,6 +131,7 @@ target_link_libraries(quickstep_expressions_scalar
                       quickstep_expressions_scalar_ScalarBinaryExpression
                       quickstep_expressions_scalar_ScalarCaseExpression
                       quickstep_expressions_scalar_ScalarLiteral
+                      quickstep_expressions_scalar_ScalarSharedExpression
                       quickstep_expressions_scalar_ScalarUnaryExpression)
 
 # Tests:

http://git-wip-us.apache.org/repos/asf/incubator-quickstep/blob/0fad9ec0/expressions/scalar/Scalar.cpp
----------------------------------------------------------------------
diff --git a/expressions/scalar/Scalar.cpp b/expressions/scalar/Scalar.cpp
index a1c436c..c552d8b 100644
--- a/expressions/scalar/Scalar.cpp
+++ b/expressions/scalar/Scalar.cpp
@@ -19,6 +19,9 @@
 
 #include "expressions/scalar/Scalar.hpp"
 
+#include <string>
+#include <vector>
+
 #include "utility/Macros.hpp"
 
 namespace quickstep {
@@ -28,6 +31,7 @@ const char *Scalar::kScalarDataSourceNames[] = {
   "Attribute",
   "UnaryExpression",
   "BinaryExpression",
+  "SharedExpression",
   "SimpleCase"
 };
 
@@ -35,4 +39,15 @@ const TypedValue& Scalar::getStaticValue() const {
   FATAL_ERROR("Called getStaticValue() on a Scalar which does not have a static value");
 }
 
+void Scalar::getFieldStringItems(
+    std::vector<std::string> *inline_field_names,
+    std::vector<std::string> *inline_field_values,
+    std::vector<std::string> *non_container_child_field_names,
+    std::vector<const Expression*> *non_container_child_fields,
+    std::vector<std::string> *container_child_field_names,
+    std::vector<std::vector<const Expression*>> *container_child_fields) const {
+  inline_field_names->emplace_back("result_type");
+  inline_field_values->emplace_back(type_.getName());
+}
+
 }  // namespace quickstep

http://git-wip-us.apache.org/repos/asf/incubator-quickstep/blob/0fad9ec0/expressions/scalar/Scalar.hpp
----------------------------------------------------------------------
diff --git a/expressions/scalar/Scalar.hpp b/expressions/scalar/Scalar.hpp
index 2db850a..472b71c 100644
--- a/expressions/scalar/Scalar.hpp
+++ b/expressions/scalar/Scalar.hpp
@@ -20,18 +20,22 @@
 #ifndef QUICKSTEP_EXPRESSIONS_SCALAR_SCALAR_HPP_
 #define QUICKSTEP_EXPRESSIONS_SCALAR_SCALAR_HPP_
 
+#include <string>
+#include <type_traits>
 #include <utility>
 #include <vector>
 
 #include "catalog/CatalogTypedefs.hpp"
+#include "expressions/Expression.hpp"
 #include "expressions/Expressions.pb.h"
 #include "storage/StorageBlockInfo.hpp"
 #include "types/TypedValue.hpp"
+#include "types/containers/ColumnVector.hpp"
 #include "utility/Macros.hpp"
 
 namespace quickstep {
 
-class ColumnVector;
+class ColumnVectorCache;
 class Type;
 class ValueAccessor;
 
@@ -44,7 +48,7 @@ struct SubBlocksReference;
 /**
  * @brief Base class for anything which evaluates to a Scalar value.
  **/
-class Scalar {
+class Scalar : public Expression {
  public:
   /**
    * @brief The possible provenance of Scalar values.
@@ -55,6 +59,7 @@ class Scalar {
     kUnaryExpression,
     kBinaryExpression,
     kCaseExpression,
+    kSharedExpression,
     kNumScalarDataSources  // Not a real ScalarDataSource, exists for counting purposes.
   };
 
@@ -70,6 +75,11 @@ class Scalar {
   virtual ~Scalar() {
   }
 
+  std::string getName() const override {
+    return kScalarDataSourceNames[
+        static_cast<std::underlying_type<ScalarDataSource>::type>(getDataSource())];
+  }
+
   /**
    * @brief Serialize this scalar in Protocol Buffer form.
    *
@@ -197,11 +207,14 @@ class Scalar {
    *        fast-path (non-scan) evaluation of Predicates embedded in this
    *        scalar (e.g. WHEN predicates in ScalarCaseExpression). May be NULL,
    *        in which case scan-based evaluation is always used.
+   * @param cv_cache If non-NULL, used as memoization table that is updated and
+   *        looked up during evaluation, for results of common subexpressions.
    * @return A ColumnVector of this Scalar's values for each tuple accesible
    *         via accessor.
    **/
-  virtual ColumnVector* getAllValues(ValueAccessor *accessor,
-                                     const SubBlocksReference *sub_blocks_ref) const = 0;
+  virtual ColumnVectorPtr getAllValues(ValueAccessor *accessor,
+                                       const SubBlocksReference *sub_blocks_ref,
+                                       ColumnVectorCache *cv_cache) const = 0;
 
   /**
    * @brief Get this Scalar's value for all specified joined tuples from two
@@ -215,19 +228,30 @@ class Scalar {
    *        from the right relation.
    * @param joined_tuple_ids A series of pairs of tuple ids from the left and
    *        right relations that will be joined.
+   * @param cv_cache If non-NULL, used as memoization table that is updated and
+   *        looked up during evaluation, for results of common subexpressions.
    * @return A ColumnVector of this Scalar's values for all the joined tuples
    *         specified by joined_tuple_ids.
    **/
-  virtual ColumnVector* getAllValuesForJoin(
+  virtual ColumnVectorPtr getAllValuesForJoin(
       const relation_id left_relation_id,
       ValueAccessor *left_accessor,
       const relation_id right_relation_id,
       ValueAccessor *right_accessor,
-      const std::vector<std::pair<tuple_id, tuple_id>> &joined_tuple_ids) const = 0;
+      const std::vector<std::pair<tuple_id, tuple_id>> &joined_tuple_ids,
+      ColumnVectorCache *cv_cache) const = 0;
 
  protected:
-  explicit Scalar(const Type &type) : type_(type) {
-  }
+  void getFieldStringItems(
+      std::vector<std::string> *inline_field_names,
+      std::vector<std::string> *inline_field_values,
+      std::vector<std::string> *non_container_child_field_names,
+      std::vector<const Expression*> *non_container_child_fields,
+      std::vector<std::string> *container_child_field_names,
+      std::vector<std::vector<const Expression*>> *container_child_fields) const override;
+
+  explicit Scalar(const Type &type)
+      : Expression(), type_(type) {}
 
   const Type &type_;
 

http://git-wip-us.apache.org/repos/asf/incubator-quickstep/blob/0fad9ec0/expressions/scalar/ScalarAttribute.cpp
----------------------------------------------------------------------
diff --git a/expressions/scalar/ScalarAttribute.cpp b/expressions/scalar/ScalarAttribute.cpp
index cc42084..036eeba 100644
--- a/expressions/scalar/ScalarAttribute.cpp
+++ b/expressions/scalar/ScalarAttribute.cpp
@@ -19,6 +19,7 @@
 
 #include "expressions/scalar/ScalarAttribute.hpp"
 
+#include <string>
 #include <utility>
 #include <vector>
 
@@ -88,13 +89,15 @@ relation_id ScalarAttribute::getRelationIdForValueAccessor() const {
   return attribute_.getParent().getID();
 }
 
-ColumnVector* ScalarAttribute::getAllValues(ValueAccessor *accessor,
-                                            const SubBlocksReference *sub_blocks_ref) const {
+ColumnVectorPtr ScalarAttribute::getAllValues(
+    ValueAccessor *accessor,
+    const SubBlocksReference *sub_blocks_ref,
+    ColumnVectorCache *cv_cache) const {
   const attribute_id attr_id = attribute_.getID();
   const Type &result_type = attribute_.getType();
   return InvokeOnValueAccessorMaybeTupleIdSequenceAdapter(
       accessor,
-      [&attr_id, &result_type](auto *accessor) -> ColumnVector* {  // NOLINT(build/c++11)
+      [&attr_id, &result_type](auto *accessor) -> ColumnVectorPtr {  // NOLINT(build/c++11)
     if (NativeColumnVector::UsableForType(result_type)) {
       NativeColumnVector *result = new NativeColumnVector(result_type,
                                                           accessor->getNumTuples());
@@ -139,7 +142,7 @@ ColumnVector* ScalarAttribute::getAllValues(ValueAccessor *accessor,
           }
         }
       }
-      return result;
+      return ColumnVectorPtr(result);
     } else {
       IndirectColumnVector *result = new IndirectColumnVector(result_type,
                                                               accessor->getNumTuples());
@@ -147,17 +150,18 @@ ColumnVector* ScalarAttribute::getAllValues(ValueAccessor *accessor,
       while (accessor->next()) {
         result->appendTypedValue(accessor->getTypedValue(attr_id));
       }
-      return result;
+      return ColumnVectorPtr(result);
     }
   });
 }
 
-ColumnVector* ScalarAttribute::getAllValuesForJoin(
+ColumnVectorPtr ScalarAttribute::getAllValuesForJoin(
     const relation_id left_relation_id,
     ValueAccessor *left_accessor,
     const relation_id right_relation_id,
     ValueAccessor *right_accessor,
-    const std::vector<std::pair<tuple_id, tuple_id>> &joined_tuple_ids) const {
+    const std::vector<std::pair<tuple_id, tuple_id>> &joined_tuple_ids,
+    ColumnVectorCache *cv_cache) const {
   DCHECK((attribute_.getParent().getID() == left_relation_id)
          || (attribute_.getParent().getID() == right_relation_id));
 
@@ -173,7 +177,7 @@ ColumnVector* ScalarAttribute::getAllValuesForJoin(
       [&joined_tuple_ids,
        &attr_id,
        &result_type,
-       &using_left_relation](auto *accessor) -> ColumnVector* {  // NOLINT(build/c++11)
+       &using_left_relation](auto *accessor) -> ColumnVectorPtr {  // NOLINT(build/c++11)
     if (NativeColumnVector::UsableForType(result_type)) {
       NativeColumnVector *result = new NativeColumnVector(result_type,
                                                           joined_tuple_ids.size());
@@ -196,7 +200,7 @@ ColumnVector* ScalarAttribute::getAllValuesForJoin(
                   using_left_relation ? joined_pair.first : joined_pair.second));
         }
       }
-      return result;
+      return ColumnVectorPtr(result);
     } else {
       IndirectColumnVector *result = new IndirectColumnVector(result_type,
                                                               joined_tuple_ids.size());
@@ -206,9 +210,27 @@ ColumnVector* ScalarAttribute::getAllValuesForJoin(
                   attr_id,
                   using_left_relation ? joined_pair.first : joined_pair.second));
       }
-      return result;
+      return ColumnVectorPtr(result);
     }
   });
 }
 
+void ScalarAttribute::getFieldStringItems(
+    std::vector<std::string> *inline_field_names,
+    std::vector<std::string> *inline_field_values,
+    std::vector<std::string> *non_container_child_field_names,
+    std::vector<const Expression*> *non_container_child_fields,
+    std::vector<std::string> *container_child_field_names,
+    std::vector<std::vector<const Expression*>> *container_child_fields) const {
+  Scalar::getFieldStringItems(inline_field_names,
+                              inline_field_values,
+                              non_container_child_field_names,
+                              non_container_child_fields,
+                              container_child_field_names,
+                              container_child_fields);
+
+  inline_field_names->emplace_back("attribute");
+  inline_field_values->emplace_back(std::to_string(attribute_.getID()));
+}
+
 }  // namespace quickstep

http://git-wip-us.apache.org/repos/asf/incubator-quickstep/blob/0fad9ec0/expressions/scalar/ScalarAttribute.hpp
----------------------------------------------------------------------
diff --git a/expressions/scalar/ScalarAttribute.hpp b/expressions/scalar/ScalarAttribute.hpp
index c6a41df..4d30fe9 100644
--- a/expressions/scalar/ScalarAttribute.hpp
+++ b/expressions/scalar/ScalarAttribute.hpp
@@ -20,6 +20,7 @@
 #ifndef QUICKSTEP_EXPRESSIONS_SCALAR_SCALAR_ATTRIBUTE_HPP_
 #define QUICKSTEP_EXPRESSIONS_SCALAR_SCALAR_ATTRIBUTE_HPP_
 
+#include <string>
 #include <utility>
 #include <vector>
 
@@ -28,12 +29,13 @@
 #include "expressions/scalar/Scalar.hpp"
 #include "storage/StorageBlockInfo.hpp"
 #include "types/TypedValue.hpp"
+#include "types/containers/ColumnVector.hpp"
 #include "utility/Macros.hpp"
 
 namespace quickstep {
 
 class CatalogAttribute;
-class ColumnVector;
+class ColumnVectorCache;
 class ValueAccessor;
 
 struct SubBlocksReference;
@@ -77,21 +79,31 @@ class ScalarAttribute : public Scalar {
 
   relation_id getRelationIdForValueAccessor() const override;
 
-  ColumnVector* getAllValues(ValueAccessor *accessor,
-                             const SubBlocksReference *sub_blocks_ref) const override;
+  ColumnVectorPtr getAllValues(ValueAccessor *accessor,
+                               const SubBlocksReference *sub_blocks_ref,
+                               ColumnVectorCache *cv_cache) const override;
 
-  ColumnVector* getAllValuesForJoin(
+  ColumnVectorPtr getAllValuesForJoin(
       const relation_id left_relation_id,
       ValueAccessor *left_accessor,
       const relation_id right_relation_id,
       ValueAccessor *right_accessor,
-      const std::vector<std::pair<tuple_id, tuple_id>> &joined_tuple_ids) const override;
+      const std::vector<std::pair<tuple_id, tuple_id>> &joined_tuple_ids,
+      ColumnVectorCache *cv_cache) const override;
 
   const CatalogAttribute& getAttribute() const {
     return attribute_;
   }
 
  protected:
+  void getFieldStringItems(
+      std::vector<std::string> *inline_field_names,
+      std::vector<std::string> *inline_field_values,
+      std::vector<std::string> *non_container_child_field_names,
+      std::vector<const Expression*> *non_container_child_fields,
+      std::vector<std::string> *container_child_field_names,
+      std::vector<std::vector<const Expression*>> *container_child_fields) const override;
+
   const CatalogAttribute &attribute_;
 
  private:

http://git-wip-us.apache.org/repos/asf/incubator-quickstep/blob/0fad9ec0/expressions/scalar/ScalarBinaryExpression.cpp
----------------------------------------------------------------------
diff --git a/expressions/scalar/ScalarBinaryExpression.cpp b/expressions/scalar/ScalarBinaryExpression.cpp
index 5fe6cde..9ac01b9 100644
--- a/expressions/scalar/ScalarBinaryExpression.cpp
+++ b/expressions/scalar/ScalarBinaryExpression.cpp
@@ -21,6 +21,7 @@
 
 #include <memory>
 #include <string>
+#include <type_traits>
 #include <utility>
 #include <vector>
 
@@ -33,6 +34,7 @@
 #include "types/containers/ColumnVector.hpp"
 #include "types/operations/Operation.pb.h"
 #include "types/operations/binary_operations/BinaryOperation.hpp"
+#include "types/operations/binary_operations/BinaryOperationID.hpp"
 
 #include "glog/logging.h"
 
@@ -101,13 +103,15 @@ TypedValue ScalarBinaryExpression::getValueForJoinedTuples(
   }
 }
 
-ColumnVector* ScalarBinaryExpression::getAllValues(
+ColumnVectorPtr ScalarBinaryExpression::getAllValues(
     ValueAccessor *accessor,
-    const SubBlocksReference *sub_blocks_ref) const {
+    const SubBlocksReference *sub_blocks_ref,
+    ColumnVectorCache *cv_cache) const {
   if (fast_operator_.get() == nullptr) {
-    return ColumnVector::MakeVectorOfValue(getType(),
-                                           static_value_,
-                                           accessor->getNumTuplesVirtual());
+    return ColumnVectorPtr(
+        ColumnVector::MakeVectorOfValue(getType(),
+                                        static_value_,
+                                        accessor->getNumTuplesVirtual()));
   } else {
     // NOTE(chasseur): We don't check if BOTH operands have a static value,
     // because if they did then this expression would also have a static value
@@ -117,35 +121,39 @@ ColumnVector* ScalarBinaryExpression::getAllValues(
       const attribute_id right_operand_attr_id
           = right_operand_->getAttributeIdForValueAccessor();
       if (right_operand_attr_id != -1) {
-        return fast_operator_->applyToStaticValueAndValueAccessor(
-            left_operand_->getStaticValue(),
-            accessor,
-            right_operand_attr_id);
+        return ColumnVectorPtr(
+            fast_operator_->applyToStaticValueAndValueAccessor(
+                left_operand_->getStaticValue(),
+                accessor,
+                right_operand_attr_id));
       }
 #endif  // QUICKSTEP_ENABLE_VECTOR_COPY_ELISION_SELECTION
 
-      std::unique_ptr<ColumnVector> right_result(
-          right_operand_->getAllValues(accessor, sub_blocks_ref));
-      return fast_operator_->applyToStaticValueAndColumnVector(
-          left_operand_->getStaticValue(),
-          *right_result);
+      ColumnVectorPtr right_result(
+          right_operand_->getAllValues(accessor, sub_blocks_ref, cv_cache));
+      return ColumnVectorPtr(
+          fast_operator_->applyToStaticValueAndColumnVector(
+              left_operand_->getStaticValue(),
+              *right_result));
     } else if (right_operand_->hasStaticValue()) {
 #ifdef QUICKSTEP_ENABLE_VECTOR_COPY_ELISION_SELECTION
       const attribute_id left_operand_attr_id
           = left_operand_->getAttributeIdForValueAccessor();
       if (left_operand_attr_id != -1) {
-        return fast_operator_->applyToValueAccessorAndStaticValue(
-            accessor,
-            left_operand_attr_id,
-            right_operand_->getStaticValue());
+        return ColumnVectorPtr(
+            fast_operator_->applyToValueAccessorAndStaticValue(
+                accessor,
+                left_operand_attr_id,
+                right_operand_->getStaticValue()));
       }
 #endif  // QUICKSTEP_ENABLE_VECTOR_COPY_ELISION_SELECTION
 
-      std::unique_ptr<ColumnVector> left_result(
-          left_operand_->getAllValues(accessor, sub_blocks_ref));
-      return fast_operator_->applyToColumnVectorAndStaticValue(
-          *left_result,
-          right_operand_->getStaticValue());
+      ColumnVectorPtr left_result(
+          left_operand_->getAllValues(accessor, sub_blocks_ref, cv_cache));
+      return ColumnVectorPtr(
+          fast_operator_->applyToColumnVectorAndStaticValue(
+              *left_result,
+              right_operand_->getStaticValue()));
     } else {
 #ifdef QUICKSTEP_ENABLE_VECTOR_COPY_ELISION_SELECTION
       const attribute_id left_operand_attr_id
@@ -155,44 +163,53 @@ ColumnVector* ScalarBinaryExpression::getAllValues(
 
       if (left_operand_attr_id != -1) {
         if (right_operand_attr_id != -1) {
-          return fast_operator_->applyToSingleValueAccessor(accessor,
-                                                            left_operand_attr_id,
-                                                            right_operand_attr_id);
+          return ColumnVectorPtr(
+              fast_operator_->applyToSingleValueAccessor(
+                  accessor,
+                  left_operand_attr_id,
+                  right_operand_attr_id));
         } else {
-          std::unique_ptr<ColumnVector> right_result(
-              right_operand_->getAllValues(accessor, sub_blocks_ref));
-          return fast_operator_->applyToValueAccessorAndColumnVector(accessor,
-                                                                     left_operand_attr_id,
-                                                                     *right_result);
+          ColumnVectorPtr right_result(
+              right_operand_->getAllValues(accessor, sub_blocks_ref, cv_cache));
+          return ColumnVectorPtr(
+              fast_operator_->applyToValueAccessorAndColumnVector(
+                  accessor,
+                  left_operand_attr_id,
+                  *right_result));
         }
       } else if (right_operand_attr_id != -1) {
-        std::unique_ptr<ColumnVector> left_result(
-            left_operand_->getAllValues(accessor, sub_blocks_ref));
-        return fast_operator_->applyToColumnVectorAndValueAccessor(*left_result,
-                                                                   accessor,
-                                                                   right_operand_attr_id);
+        ColumnVectorPtr left_result(
+            left_operand_->getAllValues(accessor, sub_blocks_ref, cv_cache));
+        return ColumnVectorPtr(
+            fast_operator_->applyToColumnVectorAndValueAccessor(
+                *left_result,
+                accessor,
+                right_operand_attr_id));
       }
 #endif  // QUICKSTEP_ENABLE_VECTOR_COPY_ELISION_SELECTION
 
-      std::unique_ptr<ColumnVector> left_result(
-          left_operand_->getAllValues(accessor, sub_blocks_ref));
-      std::unique_ptr<ColumnVector> right_result(
-          right_operand_->getAllValues(accessor, sub_blocks_ref));
-      return fast_operator_->applyToColumnVectors(*left_result, *right_result);
+      ColumnVectorPtr left_result(
+          left_operand_->getAllValues(accessor, sub_blocks_ref, cv_cache));
+      ColumnVectorPtr right_result(
+          right_operand_->getAllValues(accessor, sub_blocks_ref, cv_cache));
+      return ColumnVectorPtr(
+          fast_operator_->applyToColumnVectors(*left_result, *right_result));
     }
   }
 }
 
-ColumnVector* ScalarBinaryExpression::getAllValuesForJoin(
+ColumnVectorPtr ScalarBinaryExpression::getAllValuesForJoin(
     const relation_id left_relation_id,
     ValueAccessor *left_accessor,
     const relation_id right_relation_id,
     ValueAccessor *right_accessor,
-    const std::vector<std::pair<tuple_id, tuple_id>> &joined_tuple_ids) const {
+    const std::vector<std::pair<tuple_id, tuple_id>> &joined_tuple_ids,
+    ColumnVectorCache *cv_cache) const {
   if (fast_operator_.get() == nullptr) {
-    return ColumnVector::MakeVectorOfValue(getType(),
-                                           static_value_,
-                                           joined_tuple_ids.size());
+    return ColumnVectorPtr(
+        ColumnVector::MakeVectorOfValue(getType(),
+                                        static_value_,
+                                        joined_tuple_ids.size()));
   } else {
     if (left_operand_->hasStaticValue()) {
 #ifdef QUICKSTEP_ENABLE_VECTOR_COPY_ELISION_JOIN
@@ -207,24 +224,27 @@ ColumnVector* ScalarBinaryExpression::getAllValuesForJoin(
         const bool using_left_relation = (right_operand_relation_id == left_relation_id);
         ValueAccessor *right_operand_accessor = using_left_relation ? left_accessor
                                                                     : right_accessor;
-        return fast_operator_->applyToStaticValueAndValueAccessorForJoin(
-            left_operand_->getStaticValue(),
-            right_operand_accessor,
-            using_left_relation,
-            right_operand_attr_id,
-            joined_tuple_ids);
+        return ColumnVectorPtr(
+            fast_operator_->applyToStaticValueAndValueAccessorForJoin(
+                left_operand_->getStaticValue(),
+                right_operand_accessor,
+                using_left_relation,
+                right_operand_attr_id,
+                joined_tuple_ids));
       }
 #endif  // QUICKSTEP_ENABLE_VECTOR_COPY_ELISION_JOIN
 
-      std::unique_ptr<ColumnVector> right_result(
+      ColumnVectorPtr right_result(
           right_operand_->getAllValuesForJoin(left_relation_id,
                                               left_accessor,
                                               right_relation_id,
                                               right_accessor,
-                                              joined_tuple_ids));
-      return fast_operator_->applyToStaticValueAndColumnVector(
-          left_operand_->getStaticValue(),
-          *right_result);
+                                              joined_tuple_ids,
+                                              cv_cache));
+      return ColumnVectorPtr(
+          fast_operator_->applyToStaticValueAndColumnVector(
+              left_operand_->getStaticValue(),
+              *right_result));
     } else if (right_operand_->hasStaticValue()) {
 #ifdef QUICKSTEP_ENABLE_VECTOR_COPY_ELISION_JOIN
       const attribute_id left_operand_attr_id
@@ -238,24 +258,27 @@ ColumnVector* ScalarBinaryExpression::getAllValuesForJoin(
         const bool using_left_relation = (left_operand_relation_id == left_relation_id);
         ValueAccessor *left_operand_accessor = using_left_relation ? left_accessor
                                                                    : right_accessor;
-        return fast_operator_->applyToValueAccessorAndStaticValueForJoin(
-            left_operand_accessor,
-            using_left_relation,
-            left_operand_attr_id,
-            right_operand_->getStaticValue(),
-            joined_tuple_ids);
+        return ColumnVectorPtr(
+            fast_operator_->applyToValueAccessorAndStaticValueForJoin(
+                left_operand_accessor,
+                using_left_relation,
+                left_operand_attr_id,
+                right_operand_->getStaticValue(),
+                joined_tuple_ids));
       }
 #endif  // QUICKSTEP_ENABLE_VECTOR_COPY_ELISION_JOIN
 
-      std::unique_ptr<ColumnVector> left_result(
+      ColumnVectorPtr left_result(
           left_operand_->getAllValuesForJoin(left_relation_id,
                                              left_accessor,
                                              right_relation_id,
                                              right_accessor,
-                                             joined_tuple_ids));
-      return fast_operator_->applyToColumnVectorAndStaticValue(
-          *left_result,
-          right_operand_->getStaticValue());
+                                             joined_tuple_ids,
+                                             cv_cache));
+      return ColumnVectorPtr(
+          fast_operator_->applyToColumnVectorAndStaticValue(
+              *left_result,
+              right_operand_->getStaticValue()));
     } else {
 #ifdef QUICKSTEP_ENABLE_VECTOR_COPY_ELISION_JOIN
       const attribute_id left_operand_attr_id
@@ -284,28 +307,30 @@ ColumnVector* ScalarBinaryExpression::getAllValuesForJoin(
               = (right_operand_relation_id == left_relation_id);
           ValueAccessor *right_operand_accessor = using_left_relation_for_right_operand ? left_accessor
                                                                                         : right_accessor;
-          return fast_operator_->applyToValueAccessorsForJoin(left_operand_accessor,
-                                                              using_left_relation_for_left_operand,
-                                                              left_operand_attr_id,
-                                                              right_operand_accessor,
-                                                              using_left_relation_for_right_operand,
-                                                              right_operand_attr_id,
-                                                              joined_tuple_ids);
+          return ColumnVectorPtr(
+              fast_operator_->applyToValueAccessorsForJoin(left_operand_accessor,
+                                                           using_left_relation_for_left_operand,
+                                                           left_operand_attr_id,
+                                                           right_operand_accessor,
+                                                           using_left_relation_for_right_operand,
+                                                           right_operand_attr_id,
+                                                           joined_tuple_ids));
         }
 #endif  // QUICKSTEP_ENABLE_VECTOR_COPY_ELISION_JOIN_WITH_BINARY_EXPRESSIONS
-        std::unique_ptr<ColumnVector> right_result(
+        ColumnVectorPtr right_result(
             right_operand_->getAllValuesForJoin(left_relation_id,
                                                 left_accessor,
                                                 right_relation_id,
                                                 right_accessor,
                                                 joined_tuple_ids));
 
-        return fast_operator_->applyToValueAccessorAndColumnVectorForJoin(
-            left_operand_accessor,
-            using_left_relation_for_left_operand,
-            left_operand_attr_id,
-            *right_result,
-            joined_tuple_ids);
+        return ColumnVectorPtr(
+            fast_operator_->applyToValueAccessorAndColumnVectorForJoin(
+                left_operand_accessor,
+                using_left_relation_for_left_operand,
+                left_operand_attr_id,
+                *right_result,
+                joined_tuple_ids));
       } else if (right_operand_attr_id != -1) {
         const relation_id right_operand_relation_id
             = right_operand_->getRelationIdForValueAccessor();
@@ -317,34 +342,38 @@ ColumnVector* ScalarBinaryExpression::getAllValuesForJoin(
         ValueAccessor *right_operand_accessor = using_left_relation_for_right_operand ? left_accessor
                                                                                       : right_accessor;
 
-        std::unique_ptr<ColumnVector> left_result(
+        ColumnVectorPtr left_result(
             left_operand_->getAllValuesForJoin(left_relation_id,
                                                left_accessor,
                                                right_relation_id,
                                                right_accessor,
                                                joined_tuple_ids));
-        return fast_operator_->applyToColumnVectorAndValueAccessorForJoin(
-            *left_result,
-            right_operand_accessor,
-            using_left_relation_for_right_operand,
-            right_operand_attr_id,
-            joined_tuple_ids);
+        return ColumnVectorPtr(
+            fast_operator_->applyToColumnVectorAndValueAccessorForJoin(
+                *left_result,
+                right_operand_accessor,
+                using_left_relation_for_right_operand,
+                right_operand_attr_id,
+                joined_tuple_ids));
       }
 #endif  // QUICKSTEP_ENABLE_VECTOR_COPY_ELISION_JOIN
 
-      std::unique_ptr<ColumnVector> left_result(
+      ColumnVectorPtr left_result(
           left_operand_->getAllValuesForJoin(left_relation_id,
                                              left_accessor,
                                              right_relation_id,
                                              right_accessor,
-                                             joined_tuple_ids));
-      std::unique_ptr<ColumnVector> right_result(
+                                             joined_tuple_ids,
+                                             cv_cache));
+      ColumnVectorPtr right_result(
           right_operand_->getAllValuesForJoin(left_relation_id,
                                               left_accessor,
                                               right_relation_id,
                                               right_accessor,
-                                              joined_tuple_ids));
-      return fast_operator_->applyToColumnVectors(*left_result, *right_result);
+                                              joined_tuple_ids,
+                                              cv_cache));
+      return ColumnVectorPtr(
+          fast_operator_->applyToColumnVectors(*left_result, *right_result));
     }
   }
 }
@@ -374,4 +403,38 @@ void ScalarBinaryExpression::initHelper(bool own_children) {
   }
 }
 
+void ScalarBinaryExpression::getFieldStringItems(
+    std::vector<std::string> *inline_field_names,
+    std::vector<std::string> *inline_field_values,
+    std::vector<std::string> *non_container_child_field_names,
+    std::vector<const Expression*> *non_container_child_fields,
+    std::vector<std::string> *container_child_field_names,
+    std::vector<std::vector<const Expression*>> *container_child_fields) const {
+  Scalar::getFieldStringItems(inline_field_names,
+                              inline_field_values,
+                              non_container_child_field_names,
+                              non_container_child_fields,
+                              container_child_field_names,
+                              container_child_fields);
+
+  if (fast_operator_ == nullptr) {
+    inline_field_names->emplace_back("static_value");
+    if (static_value_.isNull()) {
+      inline_field_values->emplace_back("NULL");
+    } else {
+      inline_field_values->emplace_back(type_.printValueToString(static_value_));
+    }
+  }
+
+  inline_field_names->emplace_back("operation");
+  inline_field_values->emplace_back(
+      kBinaryOperationNames[static_cast<std::underlying_type<BinaryOperationID>::type>(
+          operation_.getBinaryOperationID())]);
+
+  non_container_child_field_names->emplace_back("left_operand");
+  non_container_child_fields->emplace_back(left_operand_.get());
+  non_container_child_field_names->emplace_back("right_operand");
+  non_container_child_fields->emplace_back(right_operand_.get());
+}
+
 }  // namespace quickstep

http://git-wip-us.apache.org/repos/asf/incubator-quickstep/blob/0fad9ec0/expressions/scalar/ScalarBinaryExpression.hpp
----------------------------------------------------------------------
diff --git a/expressions/scalar/ScalarBinaryExpression.hpp b/expressions/scalar/ScalarBinaryExpression.hpp
index c84792a..4ac1f62 100644
--- a/expressions/scalar/ScalarBinaryExpression.hpp
+++ b/expressions/scalar/ScalarBinaryExpression.hpp
@@ -21,6 +21,7 @@
 #define QUICKSTEP_EXPRESSIONS_SCALAR_SCALAR_BINARY_EXPRESSION_HPP_
 
 #include <memory>
+#include <string>
 #include <utility>
 #include <vector>
 
@@ -29,6 +30,7 @@
 #include "expressions/scalar/Scalar.hpp"
 #include "storage/StorageBlockInfo.hpp"
 #include "types/TypedValue.hpp"
+#include "types/containers/ColumnVector.hpp"
 #include "types/operations/binary_operations/BinaryOperation.hpp"
 #include "utility/Macros.hpp"
 
@@ -36,7 +38,7 @@
 
 namespace quickstep {
 
-class ColumnVector;
+class ColumnVectorCache;
 class ValueAccessor;
 
 struct SubBlocksReference;
@@ -97,15 +99,26 @@ class ScalarBinaryExpression : public Scalar {
     return static_value_;
   }
 
-  ColumnVector* getAllValues(ValueAccessor *accessor,
-                             const SubBlocksReference *sub_blocks_ref) const override;
+  ColumnVectorPtr getAllValues(ValueAccessor *accessor,
+                               const SubBlocksReference *sub_blocks_ref,
+                               ColumnVectorCache *cv_cache) const override;
 
-  ColumnVector* getAllValuesForJoin(
+  ColumnVectorPtr getAllValuesForJoin(
       const relation_id left_relation_id,
       ValueAccessor *left_accessor,
       const relation_id right_relation_id,
       ValueAccessor *right_accessor,
-      const std::vector<std::pair<tuple_id, tuple_id>> &joined_tuple_ids) const override;
+      const std::vector<std::pair<tuple_id, tuple_id>> &joined_tuple_ids,
+      ColumnVectorCache *cv_cache) const override;
+
+ protected:
+  void getFieldStringItems(
+      std::vector<std::string> *inline_field_names,
+      std::vector<std::string> *inline_field_values,
+      std::vector<std::string> *non_container_child_field_names,
+      std::vector<const Expression*> *non_container_child_fields,
+      std::vector<std::string> *container_child_field_names,
+      std::vector<std::vector<const Expression*>> *container_child_fields) const override;
 
  private:
   void initHelper(bool own_children);

http://git-wip-us.apache.org/repos/asf/incubator-quickstep/blob/0fad9ec0/expressions/scalar/ScalarCaseExpression.cpp
----------------------------------------------------------------------
diff --git a/expressions/scalar/ScalarCaseExpression.cpp b/expressions/scalar/ScalarCaseExpression.cpp
index c81f723..44e40c2 100644
--- a/expressions/scalar/ScalarCaseExpression.cpp
+++ b/expressions/scalar/ScalarCaseExpression.cpp
@@ -193,18 +193,21 @@ TypedValue ScalarCaseExpression::getValueForJoinedTuples(
   }
 }
 
-ColumnVector* ScalarCaseExpression::getAllValues(
+ColumnVectorPtr ScalarCaseExpression::getAllValues(
     ValueAccessor *accessor,
-    const SubBlocksReference *sub_blocks_ref) const {
+    const SubBlocksReference *sub_blocks_ref,
+    ColumnVectorCache *cv_cache) const {
   return InvokeOnValueAccessorMaybeTupleIdSequenceAdapter(
       accessor,
-      [&](auto *accessor) -> ColumnVector* {  // NOLINT(build/c++11)
+      [&](auto *accessor) -> ColumnVectorPtr {  // NOLINT(build/c++11)
     if (has_static_value_) {
-      return ColumnVector::MakeVectorOfValue(type_,
-                                             static_value_,
-                                             accessor->getNumTuples());
+      return ColumnVectorPtr(
+          ColumnVector::MakeVectorOfValue(type_,
+                                          static_value_,
+                                          accessor->getNumTuples()));
     } else if (fixed_result_expression_ != nullptr) {
-      return fixed_result_expression_->getAllValues(accessor, sub_blocks_ref);
+      return fixed_result_expression_->getAllValues(
+          accessor, sub_blocks_ref, cv_cache);
     }
 
     const TupleIdSequence *accessor_sequence = accessor->getTupleIdSequence();
@@ -238,21 +241,23 @@ ColumnVector* ScalarCaseExpression::getAllValues(
     }
 
     // Generate a ColumnVector of all the values for each case.
-    std::vector<std::unique_ptr<ColumnVector>> case_results;
+    std::vector<ColumnVectorPtr> case_results;
     for (std::vector<std::unique_ptr<TupleIdSequence>>::size_type case_idx = 0;
          case_idx < case_matches.size();
          ++case_idx) {
       std::unique_ptr<ValueAccessor> case_accessor(
           accessor->createSharedTupleIdSequenceAdapter(*case_matches[case_idx]));
       case_results.emplace_back(
-          result_expressions_[case_idx]->getAllValues(case_accessor.get(), sub_blocks_ref));
+          result_expressions_[case_idx]->getAllValues(
+              case_accessor.get(), sub_blocks_ref, cv_cache));
     }
 
-    std::unique_ptr<ColumnVector> else_results;
+    ColumnVectorPtr else_results;
     if (!else_matches->empty()) {
       std::unique_ptr<ValueAccessor> else_accessor(
           accessor->createSharedTupleIdSequenceAdapter(*else_matches));
-      else_results.reset(else_result_expression_->getAllValues(else_accessor.get(), sub_blocks_ref));
+      else_results = else_result_expression_->getAllValues(
+          else_accessor.get(), sub_blocks_ref, cv_cache);
     }
 
     // Multiplex per-case results into a single ColumnVector with values in the
@@ -262,17 +267,18 @@ ColumnVector* ScalarCaseExpression::getAllValues(
         accessor_sequence,
         case_matches,
         *else_matches,
-        &case_results,
-        else_results.get());
+        case_results,
+        else_results);
   });
 }
 
-ColumnVector* ScalarCaseExpression::getAllValuesForJoin(
+ColumnVectorPtr ScalarCaseExpression::getAllValuesForJoin(
     const relation_id left_relation_id,
     ValueAccessor *left_accessor,
     const relation_id right_relation_id,
     ValueAccessor *right_accessor,
-    const std::vector<std::pair<tuple_id, tuple_id>> &joined_tuple_ids) const {
+    const std::vector<std::pair<tuple_id, tuple_id>> &joined_tuple_ids,
+    ColumnVectorCache *cv_cache) const {
   // Slice 'joined_tuple_ids' apart by case.
   //
   // NOTE(chasseur): We use TupleIdSequence to keep track of the positions in
@@ -321,7 +327,7 @@ ColumnVector* ScalarCaseExpression::getAllValuesForJoin(
   }
 
   // Generate a ColumnVector of all the values for each case.
-  std::vector<std::unique_ptr<ColumnVector>> case_results;
+  std::vector<ColumnVectorPtr> case_results;
   for (std::vector<std::vector<std::pair<tuple_id, tuple_id>>>::size_type case_idx = 0;
        case_idx < case_matches.size();
        ++case_idx) {
@@ -330,22 +336,24 @@ ColumnVector* ScalarCaseExpression::getAllValuesForJoin(
         left_accessor,
         right_relation_id,
         right_accessor,
-        case_matches[case_idx]));
+        case_matches[case_idx],
+        cv_cache));
   }
 
-  std::unique_ptr<ColumnVector> else_results;
+  ColumnVectorPtr else_results;
   if (!else_positions.empty()) {
     std::vector<std::pair<tuple_id, tuple_id>> else_matches;
     for (tuple_id pos : else_positions) {
       else_matches.emplace_back(joined_tuple_ids[pos]);
     }
 
-    else_results.reset(else_result_expression_->getAllValuesForJoin(
+    else_results = else_result_expression_->getAllValuesForJoin(
         left_relation_id,
         left_accessor,
         right_relation_id,
         right_accessor,
-        else_matches));
+        else_matches,
+        cv_cache);
   }
 
   // Multiplex per-case results into a single ColumnVector with values in the
@@ -355,8 +363,8 @@ ColumnVector* ScalarCaseExpression::getAllValuesForJoin(
       nullptr,
       case_positions,
       else_positions,
-      &case_results,
-      else_results.get());
+      case_results,
+      else_results);
 }
 
 void ScalarCaseExpression::MultiplexNativeColumnVector(
@@ -420,15 +428,15 @@ void ScalarCaseExpression::MultiplexNativeColumnVector(
 void ScalarCaseExpression::MultiplexIndirectColumnVector(
     const TupleIdSequence *source_sequence,
     const TupleIdSequence &case_matches,
-    IndirectColumnVector *case_result,
+    const IndirectColumnVector &case_result,
     IndirectColumnVector *output) {
   if (source_sequence == nullptr) {
     TupleIdSequence::const_iterator output_pos_it = case_matches.begin();
     for (std::size_t input_pos = 0;
-         input_pos < case_result->size();
+         input_pos < case_result.size();
          ++input_pos, ++output_pos_it) {
       output->positionalWriteTypedValue(*output_pos_it,
-                                        case_result->moveTypedValue(input_pos));
+                                        case_result.getTypedValue(input_pos));
     }
   } else {
     std::size_t input_pos = 0;
@@ -438,20 +446,20 @@ void ScalarCaseExpression::MultiplexIndirectColumnVector(
          ++output_pos, ++source_sequence_it) {
       if (case_matches.get(*source_sequence_it)) {
         output->positionalWriteTypedValue(output_pos,
-                                          case_result->moveTypedValue(input_pos++));
+                                          case_result.getTypedValue(input_pos++));
       }
     }
   }
 }
 
-ColumnVector* ScalarCaseExpression::multiplexColumnVectors(
+ColumnVectorPtr ScalarCaseExpression::multiplexColumnVectors(
     const std::size_t output_size,
     const TupleIdSequence *source_sequence,
     const std::vector<std::unique_ptr<TupleIdSequence>> &case_matches,
     const TupleIdSequence &else_matches,
-    std::vector<std::unique_ptr<ColumnVector>> *case_results,
-    ColumnVector *else_result) const {
-  DCHECK_EQ(case_matches.size(), case_results->size());
+    const std::vector<ColumnVectorPtr> &case_results,
+    const ColumnVectorPtr &else_result) const {
+  DCHECK_EQ(case_matches.size(), case_results.size());
 
   if (NativeColumnVector::UsableForType(type_)) {
     std::unique_ptr<NativeColumnVector> native_result(
@@ -461,12 +469,12 @@ ColumnVector* ScalarCaseExpression::multiplexColumnVectors(
     for (std::vector<std::unique_ptr<TupleIdSequence>>::size_type case_idx = 0;
          case_idx < case_matches.size();
          ++case_idx) {
-      DCHECK((*case_results)[case_idx]->isNative());
+      DCHECK(case_results[case_idx]->isNative());
       if (!case_matches[case_idx]->empty()) {
         MultiplexNativeColumnVector(
             source_sequence,
             *case_matches[case_idx],
-            static_cast<const NativeColumnVector&>(*(*case_results)[case_idx]),
+            static_cast<const NativeColumnVector&>(*case_results[case_idx]),
             native_result.get());
       }
     }
@@ -480,7 +488,7 @@ ColumnVector* ScalarCaseExpression::multiplexColumnVectors(
                                   native_result.get());
     }
 
-    return native_result.release();
+    return ColumnVectorPtr(native_result.release());
   } else {
     std::unique_ptr<IndirectColumnVector> indirect_result(
         new IndirectColumnVector(type_, output_size));
@@ -489,12 +497,12 @@ ColumnVector* ScalarCaseExpression::multiplexColumnVectors(
     for (std::vector<std::unique_ptr<TupleIdSequence>>::size_type case_idx = 0;
          case_idx < case_matches.size();
          ++case_idx) {
-      DCHECK(!(*case_results)[case_idx]->isNative());
+      DCHECK(!case_results[case_idx]->isNative());
       if (!case_matches[case_idx]->empty()) {
         MultiplexIndirectColumnVector(
             source_sequence,
             *case_matches[case_idx],
-            static_cast<IndirectColumnVector*>((*case_results)[case_idx].get()),
+            static_cast<const IndirectColumnVector&>(*case_results[case_idx]),
             indirect_result.get());
       }
     }
@@ -504,11 +512,52 @@ ColumnVector* ScalarCaseExpression::multiplexColumnVectors(
       DCHECK(!else_matches.empty());
       MultiplexIndirectColumnVector(source_sequence,
                                     else_matches,
-                                    static_cast<IndirectColumnVector*>(else_result),
+                                    static_cast<const IndirectColumnVector&>(*else_result),
                                     indirect_result.get());
     }
 
-    return indirect_result.release();
+    return ColumnVectorPtr(indirect_result.release());
+  }
+}
+
+void ScalarCaseExpression::getFieldStringItems(
+    std::vector<std::string> *inline_field_names,
+    std::vector<std::string> *inline_field_values,
+    std::vector<std::string> *non_container_child_field_names,
+    std::vector<const Expression*> *non_container_child_fields,
+    std::vector<std::string> *container_child_field_names,
+    std::vector<std::vector<const Expression*>> *container_child_fields) const {
+  Scalar::getFieldStringItems(inline_field_names,
+                              inline_field_values,
+                              non_container_child_field_names,
+                              non_container_child_fields,
+                              container_child_field_names,
+                              container_child_fields);
+
+  if (has_static_value_) {
+    inline_field_names->emplace_back("static_value");
+    if (static_value_.isNull()) {
+      inline_field_values->emplace_back("NULL");
+    } else {
+      inline_field_values->emplace_back(type_.printValueToString(static_value_));
+    }
+  }
+
+  container_child_field_names->emplace_back("when_predicates");
+  container_child_fields->emplace_back();
+  for (const auto &predicate : when_predicates_) {
+    container_child_fields->back().emplace_back(predicate.get());
+  }
+
+  container_child_field_names->emplace_back("result_expressions");
+  container_child_fields->emplace_back();
+  for (const auto &expression : result_expressions_) {
+    container_child_fields->back().emplace_back(expression.get());
+  }
+
+  if (else_result_expression_ != nullptr) {
+    non_container_child_field_names->emplace_back("else_result_expression");
+    non_container_child_fields->emplace_back(else_result_expression_.get());
   }
 }
 

http://git-wip-us.apache.org/repos/asf/incubator-quickstep/blob/0fad9ec0/expressions/scalar/ScalarCaseExpression.hpp
----------------------------------------------------------------------
diff --git a/expressions/scalar/ScalarCaseExpression.hpp b/expressions/scalar/ScalarCaseExpression.hpp
index e6809fa..3d0ed71 100644
--- a/expressions/scalar/ScalarCaseExpression.hpp
+++ b/expressions/scalar/ScalarCaseExpression.hpp
@@ -22,6 +22,7 @@
 
 #include <cstddef>
 #include <memory>
+#include <string>
 #include <utility>
 #include <vector>
 
@@ -31,15 +32,14 @@
 #include "expressions/scalar/Scalar.hpp"
 #include "storage/StorageBlockInfo.hpp"
 #include "types/TypedValue.hpp"
+#include "types/containers/ColumnVector.hpp"
 #include "utility/Macros.hpp"
 
 #include "glog/logging.h"
 
 namespace quickstep {
 
-class ColumnVector;
-class IndirectColumnVector;
-class NativeColumnVector;
+class ColumnVectorCache;
 class TupleIdSequence;
 class Type;
 class ValueAccessor;
@@ -132,15 +132,26 @@ class ScalarCaseExpression : public Scalar {
     }
   }
 
-  ColumnVector* getAllValues(ValueAccessor *accessor,
-                             const SubBlocksReference *sub_blocks_ref) const override;
+  ColumnVectorPtr getAllValues(ValueAccessor *accessor,
+                               const SubBlocksReference *sub_blocks_ref,
+                               ColumnVectorCache *cv_cache) const override;
 
-  ColumnVector* getAllValuesForJoin(
+  ColumnVectorPtr getAllValuesForJoin(
       const relation_id left_relation_id,
       ValueAccessor *left_accessor,
       const relation_id right_relation_id,
       ValueAccessor *right_accessor,
-      const std::vector<std::pair<tuple_id, tuple_id>> &joined_tuple_ids) const override;
+      const std::vector<std::pair<tuple_id, tuple_id>> &joined_tuple_ids,
+      ColumnVectorCache *cv_cache) const override;
+
+ protected:
+  void getFieldStringItems(
+      std::vector<std::string> *inline_field_names,
+      std::vector<std::string> *inline_field_values,
+      std::vector<std::string> *non_container_child_field_names,
+      std::vector<const Expression*> *non_container_child_fields,
+      std::vector<std::string> *container_child_field_names,
+      std::vector<std::vector<const Expression*>> *container_child_fields) const override;
 
  private:
   // Merge the values in the NativeColumnVector 'case_result' into '*output' at
@@ -158,7 +169,7 @@ class ScalarCaseExpression : public Scalar {
   static void MultiplexIndirectColumnVector(
       const TupleIdSequence *source_sequence,
       const TupleIdSequence &case_matches,
-      IndirectColumnVector *case_result,
+      const IndirectColumnVector &case_result,
       IndirectColumnVector *output);
 
   // Create and return a new ColumnVector by multiplexing the ColumnVectors
@@ -171,13 +182,13 @@ class ScalarCaseExpression : public Scalar {
   // the explicit WHEN clauses. Similarly, '*case_results' are the values
   // generated for the tuples matching each WHEN clause, and '*else_results'
   // are the values generated for the ELSE tuples.
-  ColumnVector* multiplexColumnVectors(
+  ColumnVectorPtr multiplexColumnVectors(
       const std::size_t output_size,
       const TupleIdSequence *source_sequence,
       const std::vector<std::unique_ptr<TupleIdSequence>> &case_matches,
       const TupleIdSequence &else_matches,
-      std::vector<std::unique_ptr<ColumnVector>> *case_results,
-      ColumnVector *else_result) const;
+      const std::vector<ColumnVectorPtr> &case_results,
+      const ColumnVectorPtr &else_result) const;
 
   std::vector<std::unique_ptr<Predicate>> when_predicates_;
   std::vector<std::unique_ptr<Scalar>> result_expressions_;



[2/4] incubator-quickstep git commit: Add common-subexpression support.

Posted by ji...@apache.org.
http://git-wip-us.apache.org/repos/asf/incubator-quickstep/blob/0fad9ec0/query_optimizer/rules/ExtractCommonSubexpression.cpp
----------------------------------------------------------------------
diff --git a/query_optimizer/rules/ExtractCommonSubexpression.cpp b/query_optimizer/rules/ExtractCommonSubexpression.cpp
new file mode 100644
index 0000000..ad2aec1
--- /dev/null
+++ b/query_optimizer/rules/ExtractCommonSubexpression.cpp
@@ -0,0 +1,264 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ **/
+
+#include "query_optimizer/rules/ExtractCommonSubexpression.hpp"
+
+#include <memory>
+#include <unordered_set>
+#include <vector>
+
+#include "query_optimizer/OptimizerContext.hpp"
+#include "query_optimizer/expressions/Alias.hpp"
+#include "query_optimizer/expressions/CommonSubexpression.hpp"
+#include "query_optimizer/expressions/ExpressionType.hpp"
+#include "query_optimizer/expressions/NamedExpression.hpp"
+#include "query_optimizer/expressions/PatternMatcher.hpp"
+#include "query_optimizer/expressions/Scalar.hpp"
+#include "query_optimizer/physical/Aggregate.hpp"
+#include "query_optimizer/physical/Physical.hpp"
+#include "query_optimizer/physical/PhysicalType.hpp"
+#include "query_optimizer/physical/Selection.hpp"
+#include "utility/HashError.hpp"
+
+#include "glog/logging.h"
+
+namespace quickstep {
+namespace optimizer {
+
+namespace E = ::quickstep::optimizer::expressions;
+namespace P = ::quickstep::optimizer::physical;
+
+ExtractCommonSubexpression::ExtractCommonSubexpression(
+    OptimizerContext *optimizer_context)
+    : optimizer_context_(optimizer_context) {
+  const std::vector<E::ExpressionType> whitelist = {
+      E::ExpressionType::kAlias,
+      E::ExpressionType::kAttributeReference,
+      E::ExpressionType::kAggregateFunction,
+      E::ExpressionType::kBinaryExpression,
+      E::ExpressionType::kCast,
+      E::ExpressionType::kCommonSubexpression,
+      E::ExpressionType::kScalarLiteral,
+      E::ExpressionType::kUnaryExpression
+  };
+
+  for (const auto &expr_type : whitelist) {
+    homogeneous_whitelist_.emplace(static_cast<int>(expr_type));
+  }
+}
+
+P::PhysicalPtr ExtractCommonSubexpression::apply(const P::PhysicalPtr &input) {
+  DCHECK(input->getPhysicalType() == P::PhysicalType::kTopLevelPlan);
+
+  return applyInternal(input);
+}
+
+P::PhysicalPtr ExtractCommonSubexpression::applyInternal(
+    const P::PhysicalPtr &input) {
+  std::vector<P::PhysicalPtr> new_children;
+  for (const auto &child : input->children()) {
+    new_children.emplace_back(applyInternal(child));
+  }
+
+  const P::PhysicalPtr node =
+      new_children == input->children()
+          ? input
+          : input->copyWithNewChildren(new_children);
+
+  switch (node->getPhysicalType()) {
+    case P::PhysicalType::kSelection: {
+      const P::SelectionPtr selection =
+          std::static_pointer_cast<const P::Selection>(node);
+
+      const std::vector<E::NamedExpressionPtr> new_expressions =
+          DownCast<E::NamedExpression>(
+              transformExpressions(UpCast(selection->project_expressions())));
+
+      if (new_expressions != selection->project_expressions()) {
+        return P::Selection::Create(selection->input(),
+                                    new_expressions,
+                                    selection->filter_predicate());
+      }
+      break;
+    }
+    case P::PhysicalType::kAggregate: {
+      const P::AggregatePtr aggregate =
+          std::static_pointer_cast<const P::Aggregate>(node);
+      std::vector<E::ExpressionPtr> expressions =
+          UpCast(aggregate->aggregate_expressions());
+      for (const auto &expr : aggregate->grouping_expressions()) {
+        expressions.emplace_back(expr);
+      }
+
+      const std::vector<E::ExpressionPtr> new_expressions =
+          transformExpressions(expressions);
+
+      if (new_expressions != expressions) {
+        std::vector<E::AliasPtr> new_aggregate_expressions;
+        std::vector<E::NamedExpressionPtr> new_grouping_expressions;
+        const std::size_t num_aggrs = aggregate->aggregate_expressions().size();
+
+        for (std::size_t i = 0; i < num_aggrs; ++i) {
+          DCHECK(E::SomeAlias::Matches(new_expressions[i]));
+          new_aggregate_expressions.emplace_back(
+              std::static_pointer_cast<const E::Alias>(new_expressions[i]));
+        }
+        for (std::size_t i = num_aggrs; i < new_expressions.size(); ++i) {
+          DCHECK(E::SomeNamedExpression::Matches(new_expressions[i]));
+          new_grouping_expressions.emplace_back(
+              std::static_pointer_cast<const E::NamedExpression>(new_expressions[i]));
+        }
+        return P::Aggregate::Create(aggregate->input(),
+                                    new_grouping_expressions,
+                                    new_aggregate_expressions,
+                                    aggregate->filter_predicate());
+      }
+      break;
+    }
+    default:
+      break;
+  }
+
+  return node;
+}
+
+std::vector<E::ExpressionPtr> ExtractCommonSubexpression::transformExpressions(
+    const std::vector<E::ExpressionPtr> &expressions) {
+  ScalarCounter counter;
+  ScalarHashable hashable;
+  for (const auto &expr : expressions) {
+    visitAndCount(expr, &counter, &hashable);
+  }
+
+  ScalarMap substitution_map;
+  std::vector<E::ExpressionPtr> new_expressions;
+  for (const auto &expr : expressions) {
+    new_expressions.emplace_back(
+        visitAndTransform(expr, 1, counter, hashable, &substitution_map));
+  }
+  return new_expressions;
+}
+
+E::ExpressionPtr ExtractCommonSubexpression::transformExpression(
+    const E::ExpressionPtr &expression) {
+  return transformExpressions({expression}).front();
+}
+
+bool ExtractCommonSubexpression::visitAndCount(
+    const E::ExpressionPtr &expression,
+    ScalarCounter *counter,
+    ScalarHashable *hashable) {
+  bool children_hashable = true;
+
+  const auto homogeneous_whitelist_it =
+      homogeneous_whitelist_.find(static_cast<int>(expression->getExpressionType()));
+  if (homogeneous_whitelist_it != homogeneous_whitelist_.end()) {
+    for (const auto &child : expression->children()) {
+      children_hashable &= visitAndCount(child, counter, hashable);
+    }
+  }
+
+  E::ScalarPtr scalar;
+  if (children_hashable &&
+      E::SomeScalar::MatchesWithConditionalCast(expression, &scalar)) {
+    try {
+      ++(*counter)[scalar];
+    } catch (const HashNotSupported &e) {
+      return false;
+    }
+    hashable->emplace(scalar);
+    return true;
+  }
+  return false;
+}
+
+E::ExpressionPtr ExtractCommonSubexpression::visitAndTransform(
+    const E::ExpressionPtr &expression,
+    const std::size_t max_reference_count,
+    const ScalarCounter &counter,
+    const ScalarHashable &hashable,
+    ScalarMap *substitution_map) {
+  // TODO: figure out whether it is beneficial.
+  if (expression->getExpressionType() == E::ExpressionType::kScalarLiteral ||
+      expression->getExpressionType() == E::ExpressionType::kAttributeReference) {
+    return expression;
+  }
+
+  E::ScalarPtr scalar;
+  const bool is_hashable =
+      E::SomeScalar::MatchesWithConditionalCast(expression, &scalar)
+          && hashable.find(scalar) != hashable.end();
+
+  std::size_t new_max_reference_count;
+  if (is_hashable) {
+    // CommonSubexpression node already generated.
+    const auto substitution_map_it = substitution_map->find(scalar);
+    if (substitution_map_it != substitution_map->end()) {
+      return substitution_map_it->second;
+    }
+
+    const auto counter_it = counter.find(scalar);
+    DCHECK(counter_it != counter.end());
+    DCHECK_LE(max_reference_count, counter_it->second);
+    new_max_reference_count = counter_it->second;
+  } else {
+    new_max_reference_count = max_reference_count;
+  }
+
+  std::vector<E::ExpressionPtr> new_children;
+  const auto homogeneous_whitelist_it =
+      homogeneous_whitelist_.find(static_cast<int>(expression->getExpressionType()));
+  if (homogeneous_whitelist_it == homogeneous_whitelist_.end()) {
+    for (const auto &child : expression->children()) {
+      new_children.emplace_back(transformExpression(child));
+    }
+  } else {
+    for (const auto &child : expression->children()) {
+      new_children.emplace_back(
+          visitAndTransform(child,
+                            new_max_reference_count,
+                            counter,
+                            hashable,
+                            substitution_map));
+    }
+  }
+
+  E::ExpressionPtr output;
+  if (new_children == expression->children()) {
+    output = expression;
+  } else {
+    output = std::static_pointer_cast<const E::Scalar>(
+        expression->copyWithNewChildren(new_children));
+  }
+
+  if (is_hashable && new_max_reference_count > max_reference_count) {
+    DCHECK(E::SomeScalar::Matches(output));
+    const E::CommonSubexpressionPtr common_subexpression =
+        E::CommonSubexpression::Create(
+            optimizer_context_->nextExprId(),
+            std::static_pointer_cast<const E::Scalar>(output));
+    substitution_map->emplace(scalar, common_subexpression);
+    output = common_subexpression;
+  }
+
+  return output;
+}
+
+}  // namespace optimizer
+}  // namespace quickstep

http://git-wip-us.apache.org/repos/asf/incubator-quickstep/blob/0fad9ec0/query_optimizer/rules/ExtractCommonSubexpression.hpp
----------------------------------------------------------------------
diff --git a/query_optimizer/rules/ExtractCommonSubexpression.hpp b/query_optimizer/rules/ExtractCommonSubexpression.hpp
new file mode 100644
index 0000000..0b63b7e
--- /dev/null
+++ b/query_optimizer/rules/ExtractCommonSubexpression.hpp
@@ -0,0 +1,135 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ **/
+
+#ifndef QUICKSTEP_QUERY_OPTIMIZER_RULES_EXTRACT_COMMON_SUBEXPRESSION_HPP_
+#define QUICKSTEP_QUERY_OPTIMIZER_RULES_EXTRACT_COMMON_SUBEXPRESSION_HPP_
+
+#include <memory>
+#include <string>
+#include <unordered_map>
+#include <unordered_set>
+
+#include "query_optimizer/expressions/CommonSubexpression.hpp"
+#include "query_optimizer/expressions/Expression.hpp"
+#include "query_optimizer/expressions/Scalar.hpp"
+#include "query_optimizer/physical/Physical.hpp"
+#include "query_optimizer/rules/Rule.hpp"
+#include "utility/Macros.hpp"
+
+namespace quickstep {
+namespace optimizer {
+
+class OptimizerContext;
+
+/** \addtogroup OptimizerRules
+ *  @{
+ */
+
+class ExtractCommonSubexpression : public Rule<physical::Physical> {
+ public:
+  /**
+   * @brief Constructor.
+   */
+  ExtractCommonSubexpression(OptimizerContext *optimizer_context);
+
+  ~ExtractCommonSubexpression() override {}
+
+  std::string getName() const override {
+    return "ExtractCommonSubexpression";
+  }
+
+  physical::PhysicalPtr apply(const physical::PhysicalPtr &input) override;
+
+ private:
+  physical::PhysicalPtr applyInternal(const physical::PhysicalPtr &input);
+
+  struct ScalarHash {
+    inline std::size_t operator()(const expressions::ScalarPtr &scalar) const {
+      return scalar->hash();
+    }
+  };
+
+  struct ScalarEqual {
+    inline bool operator()(const expressions::ScalarPtr &lhs,
+                           const expressions::ScalarPtr &rhs) const {
+      return lhs->equals(rhs);
+    }
+  };
+
+  using ScalarCounter =
+      std::unordered_map<expressions::ScalarPtr, std::size_t, ScalarHash, ScalarEqual>;
+
+  using ScalarMap =
+      std::unordered_map<expressions::ScalarPtr,
+                         expressions::CommonSubexpressionPtr,
+                         ScalarHash,
+                         ScalarEqual>;
+
+  using ScalarHashable = std::unordered_set<expressions::ScalarPtr>;
+
+  std::vector<expressions::ExpressionPtr> transformExpressions(
+      const std::vector<expressions::ExpressionPtr> &expressions);
+
+  expressions::ExpressionPtr transformExpression(
+      const expressions::ExpressionPtr &expression);
+
+  bool visitAndCount(
+      const expressions::ExpressionPtr &expression,
+      ScalarCounter *counter,
+      ScalarHashable *hashable);
+
+  expressions::ExpressionPtr visitAndTransform(
+      const expressions::ExpressionPtr &expression,
+      const std::size_t max_reference_count,
+      const ScalarCounter &counter,
+      const ScalarHashable &hashable,
+      ScalarMap *substitution_map);
+
+  template <typename ScalarSubclassT>
+  static std::vector<expressions::ExpressionPtr> UpCast(
+      const std::vector<std::shared_ptr<const ScalarSubclassT>> &expressions) {
+    std::vector<expressions::ExpressionPtr> output;
+    for (const auto &expr : expressions) {
+      output.emplace_back(expr);
+    }
+    return output;
+  }
+
+  template <typename ScalarSubclassT>
+  static std::vector<std::shared_ptr<const ScalarSubclassT>> DownCast(
+      const std::vector<expressions::ExpressionPtr> &expressions) {
+    std::vector<std::shared_ptr<const ScalarSubclassT>> output;
+    for (const auto &expr : expressions) {
+      output.emplace_back(std::static_pointer_cast<const ScalarSubclassT>(expr));
+    }
+    return output;
+  }
+
+  OptimizerContext *optimizer_context_;
+  std::unordered_set<int> homogeneous_whitelist_;
+
+  DISALLOW_COPY_AND_ASSIGN(ExtractCommonSubexpression);
+};
+
+/** @} */
+
+}  // namespace optimizer
+}  // namespace quickstep
+
+#endif  // QUICKSTEP_QUERY_OPTIMIZER_RULES_EXTRACT_COMMON_SUBEXPRESSION_HPP_

http://git-wip-us.apache.org/repos/asf/incubator-quickstep/blob/0fad9ec0/query_optimizer/rules/ReuseAggregateExpressions.cpp
----------------------------------------------------------------------
diff --git a/query_optimizer/rules/ReuseAggregateExpressions.cpp b/query_optimizer/rules/ReuseAggregateExpressions.cpp
new file mode 100644
index 0000000..7151fdf
--- /dev/null
+++ b/query_optimizer/rules/ReuseAggregateExpressions.cpp
@@ -0,0 +1,276 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ **/
+
+#include "query_optimizer/rules/ReuseAggregateExpressions.hpp"
+
+#include <cstddef>
+#include <list>
+#include <map>
+#include <unordered_map>
+#include <vector>
+
+#include "expressions/aggregation/AggregateFunction.hpp"
+#include "expressions/aggregation/AggregateFunctionFactory.hpp"
+#include "expressions/aggregation/AggregationID.hpp"
+#include "query_optimizer/OptimizerContext.hpp"
+#include "query_optimizer/expressions/AggregateFunction.hpp"
+#include "query_optimizer/expressions/Alias.hpp"
+#include "query_optimizer/expressions/AttributeReference.hpp"
+#include "query_optimizer/expressions/BinaryExpression.hpp"
+#include "query_optimizer/expressions/ExpressionType.hpp"
+#include "query_optimizer/expressions/ExpressionUtil.hpp"
+#include "query_optimizer/expressions/NamedExpression.hpp"
+#include "query_optimizer/expressions/Scalar.hpp"
+#include "query_optimizer/physical/Aggregate.hpp"
+#include "query_optimizer/physical/PatternMatcher.hpp"
+#include "query_optimizer/physical/Physical.hpp"
+#include "query_optimizer/physical/PhysicalType.hpp"
+#include "query_optimizer/physical/Selection.hpp"
+#include "query_optimizer/physical/TopLevelPlan.hpp"
+#include "types/operations/binary_operations/BinaryOperation.hpp"
+#include "types/operations/binary_operations/BinaryOperationFactory.hpp"
+#include "types/operations/binary_operations/BinaryOperationID.hpp"
+#include "utility/EqualsAnyConstant.hpp"
+#include "utility/HashError.hpp"
+
+#include "glog/logging.h"
+
+namespace quickstep {
+namespace optimizer {
+
+namespace E = ::quickstep::optimizer::expressions;
+namespace P = ::quickstep::optimizer::physical;
+
+void ReuseAggregateExpressions::init(const P::PhysicalPtr &input) {
+  DCHECK(input->getPhysicalType() == P::PhysicalType::kTopLevelPlan);
+
+  const P::TopLevelPlanPtr top_level_plan =
+     std::static_pointer_cast<const P::TopLevelPlan>(input);
+  cost_model_.reset(
+      new cost::StarSchemaSimpleCostModel(top_level_plan->shared_subplans()));
+}
+
+P::PhysicalPtr ReuseAggregateExpressions::applyToNode(
+    const P::PhysicalPtr &input) {
+  P::AggregatePtr aggregate;
+  if (!P::SomeAggregate::MatchesWithConditionalCast(input, &aggregate)) {
+    return input;
+  }
+
+  const std::vector<E::AliasPtr> &agg_exprs = aggregate->aggregate_expressions();
+
+  std::unordered_map<E::ScalarPtr,
+                     std::map<AggregationID, std::vector<std::size_t>>,
+                     ScalarHash, ScalarEqual> agg_expr_info;
+
+  std::list<std::size_t> count_star_info;
+
+  for (std::size_t i = 0; i < agg_exprs.size(); ++i) {
+    DCHECK(agg_exprs[i]->expression()->getExpressionType()
+               == E::ExpressionType::kAggregateFunction);
+    const E::AggregateFunctionPtr agg_expr =
+        std::static_pointer_cast<const E::AggregateFunction>(
+            agg_exprs[i]->expression());
+
+    // Skip DISTINCT aggregations.
+    if (agg_expr->is_distinct()) {
+      continue;
+    }
+
+    const AggregationID agg_id = agg_expr->getAggregate().getAggregationID();
+    const std::vector<E::ScalarPtr> &arguments = agg_expr->getArguments();
+
+    // Currently we only consider aggregate functions with 0 or 1 argument.
+    if (agg_id == AggregationID::kCount) {
+      if (arguments.empty()) {
+        count_star_info.emplace_front(i);
+        continue;
+      } else if (!arguments.front()->getValueType().isNullable()) {
+        count_star_info.emplace_back(i);
+        continue;
+      }
+    }
+    if (arguments.size() == 1) {
+      try {
+        agg_expr_info[arguments.front()][agg_id].emplace_back(i);
+      } catch (const HashNotSupported &e) {
+        continue;
+      }
+    }
+  }
+
+  std::vector<std::unique_ptr<AggregateReference>> agg_refs(agg_exprs.size());
+
+  constexpr std::size_t kInvalidRef = static_cast<std::size_t>(-1);
+  std::size_t count_star_ref;
+
+  if (count_star_info.empty()) {
+    count_star_ref = kInvalidRef;
+  } else {
+    auto it = count_star_info.begin();
+    count_star_ref = *it;
+
+    for (++it; it != count_star_info.end(); ++it) {
+      agg_refs[*it].reset(new AggregateReference(count_star_ref));
+    }
+  }
+
+  for (const auto &it : agg_expr_info) {
+    const auto &ref_map = it.second;
+
+    // First, check whether AVG can be reduced to SUM/COUNT.
+    bool is_avg_processed = false;
+
+    const auto avg_it = ref_map.find(AggregationID::kAvg);
+    if (avg_it != ref_map.end()) {
+      std::size_t count_ref = kInvalidRef;
+
+      if (it.first->getValueType().isNullable()) {
+        const auto count_it = ref_map.find(AggregationID::kCount);
+        if (count_it != ref_map.end()) {
+          DCHECK(!count_it->second.empty());
+          count_ref = count_it->second.front();
+        }
+      } else {
+        count_ref = count_star_ref;
+      }
+
+      if (count_ref != kInvalidRef) {
+        const auto sum_it = ref_map.find(AggregationID::kSum);
+        const std::size_t sum_ref =
+            sum_it == ref_map.end() ? kInvalidRef : sum_it->second.front();
+
+        for (const std::size_t idx : avg_it->second) {
+          agg_refs[idx].reset(new AggregateReference(sum_ref, count_ref));
+        }
+        is_avg_processed = true;
+      }
+    }
+
+    // Then, eliminate duplicate aggregate expressions.
+    for (const auto &ref_it : ref_map) {
+      if (ref_it.first == AggregationID::kAvg && is_avg_processed) {
+        continue;
+      }
+
+      const auto &indices = ref_it.second;
+      DCHECK(!indices.empty());
+      const std::size_t ref = indices.front();
+      for (std::size_t i = 1; i < indices.size(); ++i) {
+        agg_refs[indices[i]].reset(new AggregateReference(ref));
+      }
+    }
+  }
+
+  bool need_transform = false;
+  for (const auto &agg_ref : agg_refs) {
+    if (agg_ref != nullptr) {
+      need_transform = true;
+      break;
+    }
+  }
+
+  if (!need_transform) {
+    return input;
+  }
+
+  const std::vector<E::AttributeReferencePtr> agg_attrs = E::ToRefVector(agg_exprs);
+
+  std::vector<E::AliasPtr> new_agg_exprs;
+  std::vector<E::NamedExpressionPtr> new_select_exprs;
+
+  for (const auto &grouping_expr : aggregate->grouping_expressions()) {
+    new_select_exprs.emplace_back(E::ToRef(grouping_expr));
+  }
+
+  for (std::size_t i = 0; i < agg_refs.size(); ++i) {
+    const auto &agg_ref = agg_refs[i];
+    const E::AliasPtr &agg_expr = agg_exprs[i];
+
+    if (agg_ref == nullptr) {
+      new_agg_exprs.emplace_back(agg_expr);
+      new_select_exprs.emplace_back(
+          E::AttributeReference::Create(agg_expr->id(),
+                                        agg_expr->attribute_name(),
+                                        agg_expr->attribute_alias(),
+                                        agg_expr->relation_name(),
+                                        agg_expr->getValueType(),
+                                        E::AttributeReferenceScope::kLocal));
+    } else {
+      switch (agg_ref->kind) {
+        case AggregateReference::kDirect: {
+          new_select_exprs.emplace_back(
+              E::Alias::Create(agg_expr->id(),
+                               agg_attrs[agg_ref->first_ref],
+                               agg_expr->attribute_name(),
+                               agg_expr->attribute_alias()));
+          break;
+        }
+        case AggregateReference::kAvg: {
+          E::AttributeReferencePtr sum_attr;
+          if (agg_ref->first_ref == kInvalidRef) {
+            const E::AggregateFunctionPtr avg_expr =
+                std::static_pointer_cast<const E::AggregateFunction>(agg_expr->expression());
+
+            const AggregateFunction &sum_func =
+                AggregateFunctionFactory::Get(AggregationID::kSum);
+            const E::AggregateFunctionPtr sum_expr =
+                E::AggregateFunction::Create(sum_func,
+                                             avg_expr->getArguments(),
+                                             avg_expr->is_vector_aggregate(),
+                                             avg_expr->is_distinct());
+            new_agg_exprs.emplace_back(
+                E::Alias::Create(optimizer_context_->nextExprId(),
+                                 sum_expr,
+                                 agg_expr->attribute_name(),
+                                 agg_expr->attribute_alias()));
+
+            sum_attr = E::ToRef(new_agg_exprs.back());
+          } else {
+            sum_attr = agg_attrs[agg_ref->first_ref];
+          }
+
+          const BinaryOperation &divide_op =
+              BinaryOperationFactory::GetBinaryOperation(BinaryOperationID::kDivide);
+          const E::BinaryExpressionPtr avg_expr =
+              E::BinaryExpression::Create(divide_op,
+                                          sum_attr,
+                                          agg_attrs[agg_ref->second_ref]);
+          new_select_exprs.emplace_back(
+              E::Alias::Create(agg_expr->id(),
+                               avg_expr,
+                               agg_expr->attribute_name(),
+                               agg_expr->attribute_alias()));
+        }
+      }
+    }
+  }
+
+  const P::AggregatePtr new_aggregate =
+      P::Aggregate::Create(aggregate->input(),
+                           aggregate->grouping_expressions(),
+                           new_agg_exprs,
+                           aggregate->filter_predicate());
+
+  return P::Selection::Create(new_aggregate, new_select_exprs, nullptr);
+}
+
+
+}  // namespace optimizer
+}  // namespace quickstep

http://git-wip-us.apache.org/repos/asf/incubator-quickstep/blob/0fad9ec0/query_optimizer/rules/ReuseAggregateExpressions.hpp
----------------------------------------------------------------------
diff --git a/query_optimizer/rules/ReuseAggregateExpressions.hpp b/query_optimizer/rules/ReuseAggregateExpressions.hpp
new file mode 100644
index 0000000..5b78e46
--- /dev/null
+++ b/query_optimizer/rules/ReuseAggregateExpressions.hpp
@@ -0,0 +1,98 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ **/
+
+#ifndef QUICKSTEP_QUERY_OPTIMIZER_RULES_REUSE_AGGREGATE_EXPRESSIONS_HPP_
+#define QUICKSTEP_QUERY_OPTIMIZER_RULES_REUSE_AGGREGATE_EXPRESSIONS_HPP_
+
+#include <cstddef>
+#include <memory>
+#include <string>
+#include <vector>
+
+#include "query_optimizer/cost_model/StarSchemaSimpleCostModel.hpp"
+#include "query_optimizer/expressions/Scalar.hpp"
+#include "query_optimizer/physical/Physical.hpp"
+#include "query_optimizer/rules/BottomUpRule.hpp"
+#include "utility/Macros.hpp"
+
+namespace quickstep {
+namespace optimizer {
+
+class OptimizerContext;
+
+/** \addtogroup OptimizerRules
+ *  @{
+ */
+
+class ReuseAggregateExpressions : public BottomUpRule<physical::Physical> {
+ public:
+  ReuseAggregateExpressions(OptimizerContext *optimizer_context)
+      : optimizer_context_(optimizer_context) {}
+
+  std::string getName() const override {
+    return "ReuseAggregateExpressions";
+  }
+
+ protected:
+  void init(const physical::PhysicalPtr &input) override;
+
+  physical::PhysicalPtr applyToNode(const physical::PhysicalPtr &input) override;
+
+ private:
+  struct ScalarHash {
+    inline std::size_t operator()(const expressions::ScalarPtr &scalar) const {
+      return scalar->hash();
+    }
+  };
+
+  struct ScalarEqual {
+    inline bool operator()(const expressions::ScalarPtr &lhs,
+                           const expressions::ScalarPtr &rhs) const {
+      return lhs->equals(rhs);
+    }
+  };
+
+  struct AggregateReference {
+    enum Kind {
+      kDirect = 0,
+      kAvg
+    };
+
+    AggregateReference(const std::size_t ref)
+        : kind(kDirect), first_ref(ref), second_ref(0) {}
+
+    AggregateReference(const std::size_t sum_ref, const std::size_t count_ref)
+        : kind(kAvg), first_ref(sum_ref), second_ref(count_ref) {}
+
+    const Kind kind;
+    const std::size_t first_ref;
+    const std::size_t second_ref;
+  };
+
+  OptimizerContext *optimizer_context_;
+
+  std::unique_ptr<cost::StarSchemaSimpleCostModel> cost_model_;
+
+  DISALLOW_COPY_AND_ASSIGN(ReuseAggregateExpressions);
+};
+
+}  // namespace optimizer
+}  // namespace quickstep
+
+#endif  // QUICKSTEP_QUERY_OPTIMIZER_RULES_REUSE_AGGREGATE_EXPRESSIONS_HPP_

http://git-wip-us.apache.org/repos/asf/incubator-quickstep/blob/0fad9ec0/relational_operators/CMakeLists.txt
----------------------------------------------------------------------
diff --git a/relational_operators/CMakeLists.txt b/relational_operators/CMakeLists.txt
index 39538ea..a6a3cd0 100644
--- a/relational_operators/CMakeLists.txt
+++ b/relational_operators/CMakeLists.txt
@@ -282,6 +282,7 @@ target_link_libraries(quickstep_relationaloperators_HashJoinOperator
                       quickstep_types_TypedValue
                       quickstep_types_containers_ColumnVector
                       quickstep_types_containers_ColumnVectorsValueAccessor
+                      quickstep_utility_ColumnVectorCache
                       quickstep_utility_Macros
                       quickstep_utility_lipfilter_LIPFilterAdaptiveProber
                       quickstep_utility_lipfilter_LIPFilterUtil
@@ -331,6 +332,7 @@ target_link_libraries(quickstep_relationaloperators_NestedLoopsJoinOperator
                       quickstep_storage_TupleStorageSubBlock
                       quickstep_storage_ValueAccessor
                       quickstep_types_containers_ColumnVectorsValueAccessor
+                      quickstep_utility_ColumnVectorCache
                       quickstep_utility_Macros
                       tmb)
 target_link_libraries(quickstep_relationaloperators_RebuildWorkOrder

http://git-wip-us.apache.org/repos/asf/incubator-quickstep/blob/0fad9ec0/relational_operators/HashJoinOperator.cpp
----------------------------------------------------------------------
diff --git a/relational_operators/HashJoinOperator.cpp b/relational_operators/HashJoinOperator.cpp
index 0e75411..ea90828 100644
--- a/relational_operators/HashJoinOperator.cpp
+++ b/relational_operators/HashJoinOperator.cpp
@@ -50,6 +50,7 @@
 #include "types/TypedValue.hpp"
 #include "types/containers/ColumnVector.hpp"
 #include "types/containers/ColumnVectorsValueAccessor.hpp"
+#include "utility/ColumnVectorCache.hpp"
 #include "utility/lip_filter/LIPFilterAdaptiveProber.hpp"
 #include "utility/lip_filter/LIPFilterUtil.hpp"
 
@@ -532,6 +533,7 @@ void HashInnerJoinWorkOrder::executeWithoutCopyElision(ValueAccessor *probe_acce
     }
 
     ColumnVectorsValueAccessor temp_result;
+    std::unique_ptr<ColumnVectorCache> cv_cache = std::make_unique<ColumnVectorCache>();
     for (auto selection_cit = selection_.begin();
          selection_cit != selection_.end();
          ++selection_cit) {
@@ -539,8 +541,10 @@ void HashInnerJoinWorkOrder::executeWithoutCopyElision(ValueAccessor *probe_acce
                                                                   build_accessor.get(),
                                                                   probe_relation_id,
                                                                   probe_accessor,
-                                                                  build_block_entry.second));
+                                                                  build_block_entry.second,
+                                                                  cv_cache.get()));
     }
+    cv_cache.reset();
 
     output_destination_->bulkInsertTuples(&temp_result);
   }
@@ -649,12 +653,14 @@ void HashInnerJoinWorkOrder::executeWithCopyElision(ValueAccessor *probe_accesso
         zipped_joined_tuple_ids.emplace_back(build_tids[i], probe_tids[i]);
       }
 
+      ColumnVectorCache cv_cache;
       for (const Scalar *scalar : non_trivial_expressions) {
         temp_result.addColumn(scalar->getAllValuesForJoin(build_relation_id,
                                                           build_accessor.get(),
                                                           probe_relation_id,
                                                           probe_accessor,
-                                                          zipped_joined_tuple_ids));
+                                                          zipped_joined_tuple_ids,
+                                                          &cv_cache));
       }
     }
 
@@ -765,13 +771,16 @@ void HashSemiJoinWorkOrder::executeWithResidualPredicate() {
 
   std::unique_ptr<ValueAccessor> probe_accessor_with_filter(
       probe_store.createValueAccessor(&filter));
+
   ColumnVectorsValueAccessor temp_result;
+  std::unique_ptr<ColumnVectorCache> cv_cache = std::make_unique<ColumnVectorCache>();
   for (vector<unique_ptr<const Scalar>>::const_iterator selection_it = selection_.begin();
        selection_it != selection_.end();
        ++selection_it) {
     temp_result.addColumn((*selection_it)->getAllValues(
-        probe_accessor_with_filter.get(), &sub_blocks_ref));
+        probe_accessor_with_filter.get(), &sub_blocks_ref, cv_cache.get()));
   }
+  cv_cache.reset();
 
   output_destination_->bulkInsertTuples(&temp_result);
 }
@@ -828,12 +837,15 @@ void HashSemiJoinWorkOrder::executeWithoutResidualPredicate() {
 
   std::unique_ptr<ValueAccessor> probe_accessor_with_filter(
       probe_accessor->createSharedTupleIdSequenceAdapterVirtual(*existence_map));
+
   ColumnVectorsValueAccessor temp_result;
+  std::unique_ptr<ColumnVectorCache> cv_cache = std::make_unique<ColumnVectorCache>();
   for (vector<unique_ptr<const Scalar>>::const_iterator selection_it = selection_.begin();
        selection_it != selection_.end(); ++selection_it) {
     temp_result.addColumn((*selection_it)->getAllValues(
-        probe_accessor_with_filter.get(), &sub_blocks_ref));
+        probe_accessor_with_filter.get(), &sub_blocks_ref, cv_cache.get()));
   }
+  cv_cache.reset();
 
   output_destination_->bulkInsertTuples(&temp_result);
 }
@@ -886,12 +898,15 @@ void HashAntiJoinWorkOrder::executeWithoutResidualPredicate() {
 
   std::unique_ptr<ValueAccessor> probe_accessor_with_filter(
       probe_accessor->createSharedTupleIdSequenceAdapterVirtual(*existence_map));
+
   ColumnVectorsValueAccessor temp_result;
+  std::unique_ptr<ColumnVectorCache> cv_cache = std::make_unique<ColumnVectorCache>();
   for (vector<unique_ptr<const Scalar>>::const_iterator selection_it = selection_.begin();
        selection_it != selection_.end(); ++selection_it) {
     temp_result.addColumn((*selection_it)->getAllValues(
-        probe_accessor_with_filter.get(), &sub_blocks_ref));
+        probe_accessor_with_filter.get(), &sub_blocks_ref, cv_cache.get()));
   }
+  cv_cache.reset();
 
   output_destination_->bulkInsertTuples(&temp_result);
 }
@@ -976,14 +991,18 @@ void HashAntiJoinWorkOrder::executeWithResidualPredicate() {
 
   std::unique_ptr<ValueAccessor> probe_accessor_with_filter(
       probe_accessor->createSharedTupleIdSequenceAdapterVirtual(*existence_map));
+
   ColumnVectorsValueAccessor temp_result;
+  std::unique_ptr<ColumnVectorCache> cv_cache = std::make_unique<ColumnVectorCache>();
   for (vector<unique_ptr<const Scalar>>::const_iterator selection_it = selection_.begin();
        selection_it != selection_.end();
        ++selection_it) {
     temp_result.addColumn(
         (*selection_it)->getAllValues(probe_accessor_with_filter.get(),
-                                      &sub_blocks_ref));
+                                      &sub_blocks_ref,
+                                      cv_cache.get()));
   }
+  cv_cache.reset();
 
   output_destination_->bulkInsertTuples(&temp_result);
 }
@@ -1032,12 +1051,11 @@ void HashOuterJoinWorkOrder::execute() {
            &build_block_entry : *collector.getJoinedTupleMap()) {
     const BlockReference build_block =
         storage_manager_->getBlock(build_block_entry.first, build_relation_);
-    const TupleStorageSubBlock &build_store =
-        build_block->getTupleStorageSubBlock();
+    const TupleStorageSubBlock &build_store = build_block->getTupleStorageSubBlock();
+    std::unique_ptr<ValueAccessor> build_accessor(build_store.createValueAccessor());
 
-    std::unique_ptr<ValueAccessor> build_accessor(
-        build_store.createValueAccessor());
     ColumnVectorsValueAccessor temp_result;
+    std::unique_ptr<ColumnVectorCache> cv_cache = std::make_unique<ColumnVectorCache>();
     for (auto selection_it = selection_.begin();
          selection_it != selection_.end();
          ++selection_it) {
@@ -1047,8 +1065,11 @@ void HashOuterJoinWorkOrder::execute() {
               build_accessor.get(),
               probe_relation_id,
               probe_accessor.get(),
-              build_block_entry.second));
+              build_block_entry.second,
+              cv_cache.get()));
     }
+    cv_cache.reset();
+
     output_destination_->bulkInsertTuples(&temp_result);
   }
 
@@ -1061,8 +1082,9 @@ void HashOuterJoinWorkOrder::execute() {
   if (num_tuples_without_matches > 0) {
     std::unique_ptr<ValueAccessor> probe_accessor_with_filter(
         probe_accessor->createSharedTupleIdSequenceAdapterVirtual(*existence_map));
-    ColumnVectorsValueAccessor temp_result;
 
+    ColumnVectorsValueAccessor temp_result;
+    std::unique_ptr<ColumnVectorCache> cv_cache = std::make_unique<ColumnVectorCache>();
     for (std::size_t i = 0; i < selection_.size(); ++i) {
       if (is_selection_on_build_[i]) {
         // NOTE(harshad, jianqiao): The assumption here is that any operation
@@ -1090,9 +1112,12 @@ void HashOuterJoinWorkOrder::execute() {
       } else {
         temp_result.addColumn(
             selection_[i]->getAllValues(probe_accessor_with_filter.get(),
-                                        &sub_blocks_ref));
+                                        &sub_blocks_ref,
+                                        cv_cache.get()));
       }
     }
+    cv_cache.reset();
+
     output_destination_->bulkInsertTuples(&temp_result);
   }
 }

http://git-wip-us.apache.org/repos/asf/incubator-quickstep/blob/0fad9ec0/relational_operators/NestedLoopsJoinOperator.cpp
----------------------------------------------------------------------
diff --git a/relational_operators/NestedLoopsJoinOperator.cpp b/relational_operators/NestedLoopsJoinOperator.cpp
index f17402f..4ef2a70 100644
--- a/relational_operators/NestedLoopsJoinOperator.cpp
+++ b/relational_operators/NestedLoopsJoinOperator.cpp
@@ -38,6 +38,7 @@
 #include "storage/TupleStorageSubBlock.hpp"
 #include "storage/ValueAccessor.hpp"
 #include "types/containers/ColumnVectorsValueAccessor.hpp"
+#include "utility/ColumnVectorCache.hpp"
 
 #include "glog/logging.h"
 
@@ -417,6 +418,7 @@ void NestedLoopsJoinWorkOrder::executeHelper(const TupleStorageSubBlock &left_st
     // evaluation and data movement, but low enough that temporary memory
     // requirements don't get out of hand).
     ColumnVectorsValueAccessor temp_result;
+    std::unique_ptr<ColumnVectorCache> cv_cache = std::make_unique<ColumnVectorCache>();
     for (vector<unique_ptr<const Scalar>>::const_iterator selection_cit = selection_.begin();
          selection_cit != selection_.end();
          ++selection_cit) {
@@ -424,8 +426,10 @@ void NestedLoopsJoinWorkOrder::executeHelper(const TupleStorageSubBlock &left_st
                                                                   left_accessor.get(),
                                                                   right_input_relation_id,
                                                                   right_accessor.get(),
-                                                                  joined_tuple_ids));
+                                                                  joined_tuple_ids,
+                                                                  cv_cache.get()));
     }
+    cv_cache.reset();
 
     output_destination_->bulkInsertTuples(&temp_result);
   }

http://git-wip-us.apache.org/repos/asf/incubator-quickstep/blob/0fad9ec0/storage/AggregationOperationState.cpp
----------------------------------------------------------------------
diff --git a/storage/AggregationOperationState.cpp b/storage/AggregationOperationState.cpp
index 90543c4..e5dc93e 100644
--- a/storage/AggregationOperationState.cpp
+++ b/storage/AggregationOperationState.cpp
@@ -57,6 +57,7 @@
 #include "types/containers/ColumnVector.hpp"
 #include "types/containers/ColumnVectorsValueAccessor.hpp"
 #include "types/containers/Tuple.hpp"
+#include "utility/ColumnVectorCache.hpp"
 #include "utility/lip_filter/LIPFilterAdaptiveProber.hpp"
 
 #include "gflags/gflags.h"
@@ -491,9 +492,10 @@ void AggregationOperationState::aggregateBlock(const block_id input_block,
     SubBlocksReference sub_blocks_ref(tuple_store,
                                       block->getIndices(),
                                       block->getIndicesConsistent());
+    ColumnVectorCache cv_cache;
     for (const auto &expression : non_trivial_expressions_) {
       non_trivial_results->addColumn(
-          expression->getAllValues(accessor, &sub_blocks_ref));
+          expression->getAllValues(accessor, &sub_blocks_ref, &cv_cache));
     }
   }
 

http://git-wip-us.apache.org/repos/asf/incubator-quickstep/blob/0fad9ec0/storage/CMakeLists.txt
----------------------------------------------------------------------
diff --git a/storage/CMakeLists.txt b/storage/CMakeLists.txt
index cb1f098..c3db584 100644
--- a/storage/CMakeLists.txt
+++ b/storage/CMakeLists.txt
@@ -297,6 +297,7 @@ target_link_libraries(quickstep_storage_AggregationOperationState
                       quickstep_types_containers_ColumnVector
                       quickstep_types_containers_ColumnVectorsValueAccessor
                       quickstep_types_containers_Tuple
+                      quickstep_utility_ColumnVectorCache
                       quickstep_utility_Macros
                       quickstep_utility_lipfilter_LIPFilterAdaptiveProber)
 target_link_libraries(quickstep_storage_AggregationOperationState_proto
@@ -961,6 +962,7 @@ target_link_libraries(quickstep_storage_StorageBlock
                       quickstep_types_containers_ColumnVectorsValueAccessor
                       quickstep_types_containers_Tuple
                       quickstep_types_operations_comparisons_ComparisonUtil
+                      quickstep_utility_ColumnVectorCache
                       quickstep_utility_Macros
                       quickstep_utility_PtrVector)
 # CMAKE_VALIDATE_IGNORE_BEGIN
@@ -1100,6 +1102,7 @@ target_link_libraries(quickstep_storage_WindowAggregationOperationState
                       quickstep_types_containers_ColumnVector
                       quickstep_types_containers_ColumnVectorUtil
                       quickstep_types_containers_ColumnVectorsValueAccessor
+                      quickstep_utility_ColumnVectorCache
                       quickstep_utility_Macros)
 target_link_libraries(quickstep_storage_WindowAggregationOperationState_proto
                       quickstep_expressions_Expressions_proto

http://git-wip-us.apache.org/repos/asf/incubator-quickstep/blob/0fad9ec0/storage/StorageBlock.cpp
----------------------------------------------------------------------
diff --git a/storage/StorageBlock.cpp b/storage/StorageBlock.cpp
index e91c1ac..31f1db2 100644
--- a/storage/StorageBlock.cpp
+++ b/storage/StorageBlock.cpp
@@ -56,6 +56,7 @@
 #include "types/containers/ColumnVectorsValueAccessor.hpp"
 #include "types/containers/Tuple.hpp"
 #include "types/operations/comparisons/ComparisonUtil.hpp"
+#include "utility/ColumnVectorCache.hpp"
 #include "utility/Macros.hpp"
 
 #include "glog/logging.h"
@@ -369,15 +370,18 @@ void StorageBlock::select(const vector<unique_ptr<const Scalar>> &selection,
                                       indices_,
                                       indices_consistent_);
 
-    std::unique_ptr<ValueAccessor> accessor(
-        tuple_store_->createValueAccessor(filter));
+    std::unique_ptr<ValueAccessor> accessor(tuple_store_->createValueAccessor(filter));
+    ColumnVectorCache cv_cache;
 
     for (vector<unique_ptr<const Scalar>>::const_iterator selection_cit = selection.begin();
          selection_cit != selection.end();
          ++selection_cit) {
       // TODO(chasseur): Can probably elide some copies for parts of the
       // selection that are ScalarAttribute or ScalarLiteral.
-      temp_result.addColumn((*selection_cit)->getAllValues(accessor.get(), &sub_blocks_ref));
+      temp_result.addColumn(
+          (*selection_cit)->getAllValues(accessor.get(),
+                                         &sub_blocks_ref,
+                                         &cv_cache));
     }
   }
 

http://git-wip-us.apache.org/repos/asf/incubator-quickstep/blob/0fad9ec0/storage/WindowAggregationOperationState.cpp
----------------------------------------------------------------------
diff --git a/storage/WindowAggregationOperationState.cpp b/storage/WindowAggregationOperationState.cpp
index 58bdf18..30d91db 100644
--- a/storage/WindowAggregationOperationState.cpp
+++ b/storage/WindowAggregationOperationState.cpp
@@ -46,6 +46,7 @@
 #include "types/containers/ColumnVector.hpp"
 #include "types/containers/ColumnVectorsValueAccessor.hpp"
 #include "types/containers/ColumnVectorUtil.hpp"
+#include "utility/ColumnVectorCache.hpp"
 
 #include "glog/logging.h"
 
@@ -236,11 +237,16 @@ void WindowAggregationOperationState::windowAggregateBlocks(
       argument_accessor = new ColumnVectorsValueAccessor();
     }
 
+    std::unique_ptr<ColumnVectorCache> cv_cache = std::make_unique<ColumnVectorCache>();
     for (const std::unique_ptr<const Scalar> &argument : arguments_) {
       argument_accessor->addColumn(argument->getAllValues(tuple_accessor,
-                                                          &sub_block_ref));
+                                                          &sub_block_ref,
+                                                          cv_cache.get()));
     }
 
+    // Release common subexpression cache as early as possible.
+    cv_cache.reset();
+
     InvokeOnAnyValueAccessor(tuple_accessor,
                              [&] (auto *tuple_accessor) -> void {  // NOLINT(build/c++11)
       tuple_accessor->beginIteration();

http://git-wip-us.apache.org/repos/asf/incubator-quickstep/blob/0fad9ec0/types/containers/ColumnVector.hpp
----------------------------------------------------------------------
diff --git a/types/containers/ColumnVector.hpp b/types/containers/ColumnVector.hpp
index fc65656..430a844 100644
--- a/types/containers/ColumnVector.hpp
+++ b/types/containers/ColumnVector.hpp
@@ -43,6 +43,9 @@ namespace quickstep {
 // TODO(chasseur): Look into ways to allocate ColumnVector memory from the
 // StorageManager.
 
+class ColumnVector;
+typedef std::shared_ptr<const ColumnVector> ColumnVectorPtr;
+
 /**
  * @brief A vector of values of the same type. Two implementations exist:
  *        NativeColumnVector (an array of fixed-size data elements) and

http://git-wip-us.apache.org/repos/asf/incubator-quickstep/blob/0fad9ec0/types/containers/ColumnVectorsValueAccessor.hpp
----------------------------------------------------------------------
diff --git a/types/containers/ColumnVectorsValueAccessor.hpp b/types/containers/ColumnVectorsValueAccessor.hpp
index 6dc1124..d9cf49d 100644
--- a/types/containers/ColumnVectorsValueAccessor.hpp
+++ b/types/containers/ColumnVectorsValueAccessor.hpp
@@ -74,22 +74,23 @@ class ColumnVectorsValueAccessor : public ValueAccessor {
    *             this value-accessor is responsible for freeing this column
    *             vector.
    **/
-  void addColumn(ColumnVector *column, const bool owns = true) {
+  void addColumn(ColumnVectorPtr column) {
     // If this is not the first column to be added, make sure it is the same
     // length as the others.
     DCHECK(columns_.empty()
            || (column->isNative()
-               ? (static_cast<const NativeColumnVector*>(column)->size() == column_length_)
-               : (static_cast<const IndirectColumnVector*>(column)->size() == column_length_)));
+               ? (static_cast<const NativeColumnVector*>(column.get())->size() == column_length_)
+               : (static_cast<const IndirectColumnVector*>(column.get())->size() == column_length_)));
     columns_.push_back(column);
     column_native_.push_back(column->isNative());
-    if (owns) {
-      deleter_.addObject(column);
-    }
-    column_length_
-        = column->isNative()
-          ? static_cast<const NativeColumnVector*>(column)->size()
-          : static_cast<const IndirectColumnVector*>(column)->size();
+    column_length_ =
+        column->isNative()
+            ? static_cast<const NativeColumnVector*>(column.get())->size()
+            : static_cast<const IndirectColumnVector*>(column.get())->size();
+  }
+
+  void addColumn(ColumnVector *column) {
+    addColumn(ColumnVectorPtr(column));
   }
 
   inline void beginIteration() {
@@ -309,11 +310,10 @@ class ColumnVectorsValueAccessor : public ValueAccessor {
            && (static_cast<std::vector<ColumnVector*>::size_type>(attr_id) < columns_.size());
   }
 
-  std::vector<ColumnVector*> columns_;
+  std::vector<ColumnVectorPtr> columns_;
   std::vector<bool> column_native_;
   std::size_t column_length_;
   std::size_t current_position_;
-  ScopedDeleter deleter_;
 
   DISALLOW_COPY_AND_ASSIGN(ColumnVectorsValueAccessor);
 };

http://git-wip-us.apache.org/repos/asf/incubator-quickstep/blob/0fad9ec0/types/operations/binary_operations/AddBinaryOperation.hpp
----------------------------------------------------------------------
diff --git a/types/operations/binary_operations/AddBinaryOperation.hpp b/types/operations/binary_operations/AddBinaryOperation.hpp
index bc862bf..2309563 100644
--- a/types/operations/binary_operations/AddBinaryOperation.hpp
+++ b/types/operations/binary_operations/AddBinaryOperation.hpp
@@ -51,6 +51,10 @@ class AddBinaryOperation : public ArithmeticBinaryOperation {
     return instance;
   }
 
+  bool isCommutative() const override {
+    return true;
+  }
+
   bool canApplyToTypes(const Type &left,
                        const Type &right) const override;
 

http://git-wip-us.apache.org/repos/asf/incubator-quickstep/blob/0fad9ec0/types/operations/binary_operations/BinaryOperation.hpp
----------------------------------------------------------------------
diff --git a/types/operations/binary_operations/BinaryOperation.hpp b/types/operations/binary_operations/BinaryOperation.hpp
index 585a1c6..c4841e3 100644
--- a/types/operations/binary_operations/BinaryOperation.hpp
+++ b/types/operations/binary_operations/BinaryOperation.hpp
@@ -334,6 +334,10 @@ class BinaryOperation : public Operation {
     return kBinaryOperationShortNames[static_cast<std::size_t>(operation_id_)];
   }
 
+  virtual bool isCommutative() const {
+    return false;
+  }
+
   /**
    * @brief Determine whether this BinaryOperation can apply to the specified
    *        Types.

http://git-wip-us.apache.org/repos/asf/incubator-quickstep/blob/0fad9ec0/types/operations/binary_operations/MultiplyBinaryOperation.hpp
----------------------------------------------------------------------
diff --git a/types/operations/binary_operations/MultiplyBinaryOperation.hpp b/types/operations/binary_operations/MultiplyBinaryOperation.hpp
index 6edc999..cc005e2 100644
--- a/types/operations/binary_operations/MultiplyBinaryOperation.hpp
+++ b/types/operations/binary_operations/MultiplyBinaryOperation.hpp
@@ -51,6 +51,10 @@ class MultiplyBinaryOperation : public ArithmeticBinaryOperation {
     return instance;
   }
 
+  bool isCommutative() const override {
+    return true;
+  }
+
   bool canApplyToTypes(const Type &left,
                        const Type &right) const override;
 

http://git-wip-us.apache.org/repos/asf/incubator-quickstep/blob/0fad9ec0/utility/CMakeLists.txt
----------------------------------------------------------------------
diff --git a/utility/CMakeLists.txt b/utility/CMakeLists.txt
index ca04462..e1fb770 100644
--- a/utility/CMakeLists.txt
+++ b/utility/CMakeLists.txt
@@ -171,6 +171,7 @@ add_library(quickstep_utility_BloomFilter_proto
 add_library(quickstep_utility_CalculateInstalledMemory CalculateInstalledMemory.cpp CalculateInstalledMemory.hpp)
 add_library(quickstep_utility_Cast ../empty_src.cpp Cast.hpp)
 add_library(quickstep_utility_CheckSnprintf ../empty_src.cpp CheckSnprintf.hpp)
+add_library(quickstep_utility_ColumnVectorCache ../empty_src.cpp ColumnVectorCache.hpp)
 add_library(quickstep_utility_CompositeHash ../empty_src.cpp CompositeHash.hpp)
 add_library(quickstep_utility_BarrieredReadWriteConcurrentBitVector
             ../empty_src.cpp
@@ -182,6 +183,7 @@ add_library(quickstep_utility_ExecutionDAGVisualizer
             ExecutionDAGVisualizer.cpp
             ExecutionDAGVisualizer.hpp)
 add_library(quickstep_utility_Glob Glob.cpp Glob.hpp)
+add_library(quickstep_utility_HashError ../empty_src.cpp HashError.hpp)
 add_library(quickstep_utility_HashPair ../empty_src.cpp HashPair.hpp)
 add_library(quickstep_utility_Macros ../empty_src.cpp Macros.hpp)
 add_library(quickstep_utility_MemStream ../empty_src.cpp MemStream.hpp)
@@ -237,6 +239,9 @@ target_link_libraries(quickstep_utility_CalculateInstalledMemory
                       glog)
 target_link_libraries(quickstep_utility_CheckSnprintf
                       glog)
+target_link_libraries(quickstep_utility_ColumnVectorCache
+                      quickstep_types_containers_ColumnVector
+                      quickstep_utility_Macros)
 target_link_libraries(quickstep_utility_CompositeHash
                       quickstep_types_TypedValue
                       quickstep_utility_HashPair
@@ -344,12 +349,14 @@ target_link_libraries(quickstep_utility
                       quickstep_utility_CalculateInstalledMemory
                       quickstep_utility_Cast
                       quickstep_utility_CheckSnprintf
+                      quickstep_utility_ColumnVectorCache
                       quickstep_utility_CompositeHash
                       quickstep_utility_DAG
                       quickstep_utility_DisjointTreeForest
                       quickstep_utility_EqualsAnyConstant
                       quickstep_utility_ExecutionDAGVisualizer
                       quickstep_utility_Glob
+                      quickstep_utility_HashError
                       quickstep_utility_HashPair
                       quickstep_utility_Macros
                       quickstep_utility_MemStream

http://git-wip-us.apache.org/repos/asf/incubator-quickstep/blob/0fad9ec0/utility/ColumnVectorCache.hpp
----------------------------------------------------------------------
diff --git a/utility/ColumnVectorCache.hpp b/utility/ColumnVectorCache.hpp
new file mode 100644
index 0000000..22715f9
--- /dev/null
+++ b/utility/ColumnVectorCache.hpp
@@ -0,0 +1,64 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ **/
+
+#ifndef QUICKSTEP_UTILITY_COLUMN_VECTOR_CACHE_HPP_
+#define QUICKSTEP_UTILITY_COLUMN_VECTOR_CACHE_HPP_
+
+#include <unordered_map>
+
+#include "types/containers/ColumnVector.hpp"
+#include "utility/Macros.hpp"
+
+#include "glog/logging.h"
+
+namespace quickstep {
+
+/** \addtogroup Expressions
+ *  @{
+ */
+
+class ColumnVectorCache {
+ public:
+  ColumnVectorCache() {}
+
+  inline bool has(const int share_id) const {
+    return cv_cache_.find(share_id) != cv_cache_.end();
+  }
+
+  inline ColumnVectorPtr get(const int share_id) const {
+    DCHECK(has(share_id));
+    return cv_cache_.at(share_id);
+  }
+
+  inline void set(const int share_id, const ColumnVectorPtr &cv) {
+    DCHECK(!has(share_id));
+    cv_cache_.emplace(share_id, cv);
+  }
+
+ private:
+  std::unordered_map<int, ColumnVectorPtr> cv_cache_;
+
+  DISALLOW_COPY_AND_ASSIGN(ColumnVectorCache);
+};
+
+/** @} */
+
+}  // namespace quickstep
+
+#endif  // QUICKSTEP_UTILITY_COLUMN_VECTOR_CACHE_HPP_

http://git-wip-us.apache.org/repos/asf/incubator-quickstep/blob/0fad9ec0/utility/HashError.hpp
----------------------------------------------------------------------
diff --git a/utility/HashError.hpp b/utility/HashError.hpp
new file mode 100644
index 0000000..3a59979
--- /dev/null
+++ b/utility/HashError.hpp
@@ -0,0 +1,55 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ **/
+
+#ifndef QUICKSTEP_UTILITY_HASH_ERROR_HPP_
+#define QUICKSTEP_UTILITY_HASH_ERROR_HPP_
+
+#include <exception>
+
+namespace quickstep {
+
+/** \addtogroup Utility
+ *  @{
+ */
+
+class HashNotSupported : public std::exception {
+ public:
+  /**
+   * @brief Constructor.
+   *
+   * @param message The error message.
+   **/
+  HashNotSupported(const std::string &message)
+      : message_(message) {}
+
+  ~HashNotSupported() throw() {}
+
+  virtual const char* what() const throw() {
+    return message_.c_str();
+  }
+
+ private:
+  const std::string message_;
+};
+
+/** @} */
+
+}  // namespace quickstep
+
+#endif  // QUICKSTEP_UTILITY_HASH_ERROR_HPP_


[3/4] incubator-quickstep git commit: Add common-subexpression support.

Posted by ji...@apache.org.
http://git-wip-us.apache.org/repos/asf/incubator-quickstep/blob/0fad9ec0/expressions/scalar/ScalarLiteral.cpp
----------------------------------------------------------------------
diff --git a/expressions/scalar/ScalarLiteral.cpp b/expressions/scalar/ScalarLiteral.cpp
index 48b5574..15ee48b 100644
--- a/expressions/scalar/ScalarLiteral.cpp
+++ b/expressions/scalar/ScalarLiteral.cpp
@@ -47,24 +47,49 @@ Scalar* ScalarLiteral::clone() const {
   return new ScalarLiteral(internal_literal_, type_);
 }
 
-ColumnVector* ScalarLiteral::getAllValues(
+ColumnVectorPtr ScalarLiteral::getAllValues(
     ValueAccessor *accessor,
-    const SubBlocksReference *sub_blocks_ref) const {
-  return ColumnVector::MakeVectorOfValue(
-      type_,
-      internal_literal_,
-      accessor->getNumTuplesVirtual());
+    const SubBlocksReference *sub_blocks_ref,
+    ColumnVectorCache *cv_cache) const {
+  return ColumnVectorPtr(
+      ColumnVector::MakeVectorOfValue(type_,
+                                      internal_literal_,
+                                      accessor->getNumTuplesVirtual()));
 }
 
-ColumnVector* ScalarLiteral::getAllValuesForJoin(
+ColumnVectorPtr ScalarLiteral::getAllValuesForJoin(
     const relation_id left_relation_id,
     ValueAccessor *left_accessor,
     const relation_id right_relation_id,
     ValueAccessor *right_accessor,
-    const std::vector<std::pair<tuple_id, tuple_id>> &joined_tuple_ids) const {
-  return ColumnVector::MakeVectorOfValue(type_,
-                                         internal_literal_,
-                                         joined_tuple_ids.size());
+    const std::vector<std::pair<tuple_id, tuple_id>> &joined_tuple_ids,
+    ColumnVectorCache *cv_cache) const {
+  return ColumnVectorPtr(
+      ColumnVector::MakeVectorOfValue(type_,
+                                      internal_literal_,
+                                      joined_tuple_ids.size()));
+}
+
+void ScalarLiteral::getFieldStringItems(
+    std::vector<std::string> *inline_field_names,
+    std::vector<std::string> *inline_field_values,
+    std::vector<std::string> *non_container_child_field_names,
+    std::vector<const Expression*> *non_container_child_fields,
+    std::vector<std::string> *container_child_field_names,
+    std::vector<std::vector<const Expression*>> *container_child_fields) const {
+  Scalar::getFieldStringItems(inline_field_names,
+                              inline_field_values,
+                              non_container_child_field_names,
+                              non_container_child_fields,
+                              container_child_field_names,
+                              container_child_fields);
+
+  inline_field_names->emplace_back("internal_literal");
+  if (internal_literal_.isNull()) {
+    inline_field_values->emplace_back("NULL");
+  } else {
+    inline_field_values->emplace_back(type_.printValueToString(internal_literal_));
+  }
 }
 
 }  // namespace quickstep

http://git-wip-us.apache.org/repos/asf/incubator-quickstep/blob/0fad9ec0/expressions/scalar/ScalarLiteral.hpp
----------------------------------------------------------------------
diff --git a/expressions/scalar/ScalarLiteral.hpp b/expressions/scalar/ScalarLiteral.hpp
index c7f5ceb..2a4c396 100644
--- a/expressions/scalar/ScalarLiteral.hpp
+++ b/expressions/scalar/ScalarLiteral.hpp
@@ -20,6 +20,7 @@
 #ifndef QUICKSTEP_EXPRESSIONS_SCALAR_SCALAR_LITERAL_HPP_
 #define QUICKSTEP_EXPRESSIONS_SCALAR_SCALAR_LITERAL_HPP_
 
+#include <string>
 #include <utility>
 #include <vector>
 
@@ -28,11 +29,12 @@
 #include "expressions/scalar/Scalar.hpp"
 #include "storage/StorageBlockInfo.hpp"
 #include "types/TypedValue.hpp"
+#include "types/containers/ColumnVector.hpp"
 #include "utility/Macros.hpp"
 
 namespace quickstep {
 
-class ColumnVector;
+class ColumnVectorCache;
 class Type;
 class ValueAccessor;
 
@@ -101,15 +103,26 @@ class ScalarLiteral : public Scalar {
     return internal_literal_;
   }
 
-  ColumnVector* getAllValues(ValueAccessor *accessor,
-                             const SubBlocksReference *sub_blocks_ref) const override;
+  ColumnVectorPtr getAllValues(ValueAccessor *accessor,
+                               const SubBlocksReference *sub_blocks_ref,
+                               ColumnVectorCache *cv_cache) const override;
 
-  ColumnVector* getAllValuesForJoin(
+  ColumnVectorPtr getAllValuesForJoin(
       const relation_id left_relation_id,
       ValueAccessor *left_accessor,
       const relation_id right_relation_id,
       ValueAccessor *right_accessor,
-      const std::vector<std::pair<tuple_id, tuple_id>> &joined_tuple_ids) const override;
+      const std::vector<std::pair<tuple_id, tuple_id>> &joined_tuple_ids,
+      ColumnVectorCache *cv_cache) const override;
+
+ protected:
+  void getFieldStringItems(
+      std::vector<std::string> *inline_field_names,
+      std::vector<std::string> *inline_field_values,
+      std::vector<std::string> *non_container_child_field_names,
+      std::vector<const Expression*> *non_container_child_fields,
+      std::vector<std::string> *container_child_field_names,
+      std::vector<std::vector<const Expression*>> *container_child_fields) const override;
 
  private:
   TypedValue internal_literal_;

http://git-wip-us.apache.org/repos/asf/incubator-quickstep/blob/0fad9ec0/expressions/scalar/ScalarSharedExpression.cpp
----------------------------------------------------------------------
diff --git a/expressions/scalar/ScalarSharedExpression.cpp b/expressions/scalar/ScalarSharedExpression.cpp
new file mode 100644
index 0000000..4ee2982
--- /dev/null
+++ b/expressions/scalar/ScalarSharedExpression.cpp
@@ -0,0 +1,141 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ **/
+
+#include "expressions/scalar/ScalarSharedExpression.hpp"
+
+#include <string>
+#include <utility>
+#include <vector>
+
+#include "catalog/CatalogTypedefs.hpp"
+#include "expressions/Expressions.pb.h"
+#include "storage/ValueAccessor.hpp"
+#include "types/TypedValue.hpp"
+#include "types/containers/ColumnVector.hpp"
+#include "utility/ColumnVectorCache.hpp"
+
+namespace quickstep {
+
+struct SubBlocksReference;
+
+ScalarSharedExpression::ScalarSharedExpression(const int share_id,
+                                               Scalar *operand)
+    : Scalar(operand->getType()),
+      share_id_(share_id),
+      operand_(operand) {
+}
+
+serialization::Scalar ScalarSharedExpression::getProto() const {
+  serialization::Scalar proto;
+  proto.set_data_source(serialization::Scalar::SHARED_EXPRESSION);
+  proto.SetExtension(serialization::ScalarSharedExpression::share_id, share_id_);
+  proto.MutableExtension(serialization::ScalarSharedExpression::operand)
+      ->CopyFrom(operand_->getProto());
+
+  return proto;
+}
+
+Scalar* ScalarSharedExpression::clone() const {
+  return new ScalarSharedExpression(share_id_, operand_->clone());
+}
+
+TypedValue ScalarSharedExpression::getValueForSingleTuple(const ValueAccessor &accessor,
+                                                          const tuple_id tuple) const {
+  return operand_->getValueForSingleTuple(accessor, tuple);
+}
+
+TypedValue ScalarSharedExpression::getValueForJoinedTuples(
+    const ValueAccessor &left_accessor,
+    const relation_id left_relation_id,
+    const tuple_id left_tuple_id,
+    const ValueAccessor &right_accessor,
+    const relation_id right_relation_id,
+    const tuple_id right_tuple_id) const {
+  return operand_->getValueForJoinedTuples(left_accessor,
+                                           left_relation_id,
+                                           left_tuple_id,
+                                           right_accessor,
+                                           right_relation_id,
+                                           right_tuple_id);
+}
+
+ColumnVectorPtr ScalarSharedExpression::getAllValues(
+    ValueAccessor *accessor,
+    const SubBlocksReference *sub_blocks_ref,
+    ColumnVectorCache *cv_cache) const {
+  if (cv_cache == nullptr) {
+    return operand_->getAllValues(accessor, sub_blocks_ref, cv_cache);
+  } else {
+    ColumnVectorPtr result;
+    if (cv_cache->has(share_id_)) {
+      result = cv_cache->get(share_id_);
+    } else {
+      result = operand_->getAllValues(accessor, sub_blocks_ref, cv_cache);
+      cv_cache->set(share_id_, result);
+    }
+    return result;
+  }
+}
+
+ColumnVectorPtr ScalarSharedExpression::getAllValuesForJoin(
+    const relation_id left_relation_id,
+    ValueAccessor *left_accessor,
+    const relation_id right_relation_id,
+    ValueAccessor *right_accessor,
+    const std::vector<std::pair<tuple_id, tuple_id>> &joined_tuple_ids,
+    ColumnVectorCache *cv_cache) const {
+  if (cv_cache == nullptr) {
+    return operand_->getAllValuesForJoin(left_relation_id,
+                                         left_accessor,
+                                         right_relation_id,
+                                         right_accessor,
+                                         joined_tuple_ids,
+                                         cv_cache);
+  } else {
+    ColumnVectorPtr result;
+    if (cv_cache->has(share_id_)) {
+      result = cv_cache->get(share_id_);
+    } else {
+      result = operand_->getAllValuesForJoin(left_relation_id,
+                                             left_accessor,
+                                             right_relation_id,
+                                             right_accessor,
+                                             joined_tuple_ids,
+                                             cv_cache);
+      cv_cache->set(share_id_, result);
+    }
+    return result;
+  }
+}
+
+void ScalarSharedExpression::getFieldStringItems(
+    std::vector<std::string> *inline_field_names,
+    std::vector<std::string> *inline_field_values,
+    std::vector<std::string> *non_container_child_field_names,
+    std::vector<const Expression*> *non_container_child_fields,
+    std::vector<std::string> *container_child_field_names,
+    std::vector<std::vector<const Expression*>> *container_child_fields) const {
+  inline_field_names->emplace_back("share_id");
+  inline_field_values->emplace_back(std::to_string(share_id_));
+
+  non_container_child_field_names->emplace_back("operand");
+  non_container_child_fields->emplace_back(operand_.get());
+}
+
+}  // namespace quickstep

http://git-wip-us.apache.org/repos/asf/incubator-quickstep/blob/0fad9ec0/expressions/scalar/ScalarSharedExpression.hpp
----------------------------------------------------------------------
diff --git a/expressions/scalar/ScalarSharedExpression.hpp b/expressions/scalar/ScalarSharedExpression.hpp
new file mode 100644
index 0000000..0b6db00
--- /dev/null
+++ b/expressions/scalar/ScalarSharedExpression.hpp
@@ -0,0 +1,119 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ **/
+
+#ifndef QUICKSTEP_EXPRESSIONS_SCALAR_SCALAR_SHARED_EXPRESSION_HPP_
+#define QUICKSTEP_EXPRESSIONS_SCALAR_SCALAR_SHARED_EXPRESSION_HPP_
+
+#include <memory>
+#include <string>
+#include <utility>
+#include <vector>
+
+#include "catalog/CatalogTypedefs.hpp"
+#include "expressions/Expressions.pb.h"
+#include "expressions/scalar/Scalar.hpp"
+#include "storage/StorageBlockInfo.hpp"
+#include "types/TypedValue.hpp"
+#include "types/containers/ColumnVector.hpp"
+#include "utility/Macros.hpp"
+
+namespace quickstep {
+
+class ColumnVectorCache;
+class ValueAccessor;
+
+struct SubBlocksReference;
+
+/** \addtogroup Expressions
+ *  @{
+ */
+
+class ScalarSharedExpression : public Scalar {
+ public:
+  /**
+   * @brief Constructor.
+   **/
+  ScalarSharedExpression(const int shared_id, Scalar *operand);
+
+  /**
+   * @brief Destructor.
+   **/
+  ~ScalarSharedExpression() override {
+  }
+
+  serialization::Scalar getProto() const override;
+
+  Scalar* clone() const override;
+
+  ScalarDataSource getDataSource() const override {
+    return kSharedExpression;
+  }
+
+  TypedValue getValueForSingleTuple(const ValueAccessor &accessor,
+                                    const tuple_id tuple) const override;
+
+  TypedValue getValueForJoinedTuples(
+      const ValueAccessor &left_accessor,
+      const relation_id left_relation_id,
+      const tuple_id left_tuple_id,
+      const ValueAccessor &right_accessor,
+      const relation_id right_relation_id,
+      const tuple_id right_tuple_id) const override;
+
+  bool hasStaticValue() const override {
+    return operand_->hasStaticValue();
+  }
+
+  const TypedValue& getStaticValue() const override {
+    return operand_->getStaticValue();
+  }
+
+  ColumnVectorPtr getAllValues(ValueAccessor *accessor,
+                               const SubBlocksReference *sub_blocks_ref,
+                               ColumnVectorCache *cv_cache) const override;
+
+  ColumnVectorPtr getAllValuesForJoin(
+      const relation_id left_relation_id,
+      ValueAccessor *left_accessor,
+      const relation_id right_relation_id,
+      ValueAccessor *right_accessor,
+      const std::vector<std::pair<tuple_id, tuple_id>> &joined_tuple_ids,
+      ColumnVectorCache *cv_cache) const override;
+
+ protected:
+  void getFieldStringItems(
+      std::vector<std::string> *inline_field_names,
+      std::vector<std::string> *inline_field_values,
+      std::vector<std::string> *non_container_child_field_names,
+      std::vector<const Expression*> *non_container_child_fields,
+      std::vector<std::string> *container_child_field_names,
+      std::vector<std::vector<const Expression*>> *container_child_fields) const override;
+
+ private:
+  const int share_id_;
+  std::unique_ptr<Scalar> operand_;
+
+  DISALLOW_COPY_AND_ASSIGN(ScalarSharedExpression);
+};
+
+/** @} */
+
+}  // namespace quickstep
+
+#endif  // QUICKSTEP_EXPRESSIONS_SCALAR_SCALAR_SHARED_EXPRESSION_HPP_

http://git-wip-us.apache.org/repos/asf/incubator-quickstep/blob/0fad9ec0/expressions/scalar/ScalarUnaryExpression.cpp
----------------------------------------------------------------------
diff --git a/expressions/scalar/ScalarUnaryExpression.cpp b/expressions/scalar/ScalarUnaryExpression.cpp
index 72fdbe1..4ae6e23 100644
--- a/expressions/scalar/ScalarUnaryExpression.cpp
+++ b/expressions/scalar/ScalarUnaryExpression.cpp
@@ -33,6 +33,7 @@
 #include "types/containers/ColumnVector.hpp"
 #include "types/operations/Operation.pb.h"
 #include "types/operations/unary_operations/UnaryOperation.hpp"
+#include "types/operations/unary_operations/UnaryOperationID.hpp"
 
 #ifdef QUICKSTEP_ENABLE_VECTOR_COPY_ELISION_JOIN
 #include "glog/logging.h"
@@ -91,36 +92,43 @@ TypedValue ScalarUnaryExpression::getValueForJoinedTuples(
   }
 }
 
-ColumnVector* ScalarUnaryExpression::getAllValues(
+ColumnVectorPtr ScalarUnaryExpression::getAllValues(
     ValueAccessor *accessor,
-    const SubBlocksReference *sub_blocks_ref) const {
+    const SubBlocksReference *sub_blocks_ref,
+    ColumnVectorCache *cv_cache) const {
   if (fast_operator_.get() == nullptr) {
-    return ColumnVector::MakeVectorOfValue(getType(),
-                                           static_value_,
-                                           accessor->getNumTuplesVirtual());
+    return ColumnVectorPtr(
+        ColumnVector::MakeVectorOfValue(getType(),
+                                        static_value_,
+                                        accessor->getNumTuplesVirtual()));
   } else {
 #ifdef QUICKSTEP_ENABLE_VECTOR_COPY_ELISION_SELECTION
     const attribute_id operand_attr_id = operand_->getAttributeIdForValueAccessor();
     if (operand_attr_id != -1) {
-      return fast_operator_->applyToValueAccessor(accessor, operand_attr_id);
+      return ColumnVectorPtr(
+          fast_operator_->applyToValueAccessor(accessor, operand_attr_id));
     }
 #endif  // QUICKSTEP_ENABLE_VECTOR_COPY_ELISION_SELECTION
 
-    std::unique_ptr<ColumnVector> operand_result(operand_->getAllValues(accessor, sub_blocks_ref));
-    return fast_operator_->applyToColumnVector(*operand_result);
+    ColumnVectorPtr operand_result(
+        operand_->getAllValues(accessor, sub_blocks_ref, cv_cache));
+    return ColumnVectorPtr(
+        fast_operator_->applyToColumnVector(*operand_result));
   }
 }
 
-ColumnVector* ScalarUnaryExpression::getAllValuesForJoin(
+ColumnVectorPtr ScalarUnaryExpression::getAllValuesForJoin(
     const relation_id left_relation_id,
     ValueAccessor *left_accessor,
     const relation_id right_relation_id,
     ValueAccessor *right_accessor,
-    const std::vector<std::pair<tuple_id, tuple_id>> &joined_tuple_ids) const {
+    const std::vector<std::pair<tuple_id, tuple_id>> &joined_tuple_ids,
+    ColumnVectorCache *cv_cache) const {
   if (fast_operator_.get() == nullptr) {
-    return ColumnVector::MakeVectorOfValue(getType(),
-                                           static_value_,
-                                           joined_tuple_ids.size());
+    return ColumnVectorPtr(
+        ColumnVector::MakeVectorOfValue(getType(),
+                                        static_value_,
+                                        joined_tuple_ids.size()));
   } else {
 #ifdef QUICKSTEP_ENABLE_VECTOR_COPY_ELISION_JOIN
     const attribute_id operand_attr_id = operand_->getAttributeIdForValueAccessor();
@@ -132,20 +140,23 @@ ColumnVector* ScalarUnaryExpression::getAllValuesForJoin(
       const bool using_left_relation = (operand_relation_id == left_relation_id);
       ValueAccessor *operand_accessor = using_left_relation ? left_accessor
                                                             : right_accessor;
-      return fast_operator_->applyToValueAccessorForJoin(operand_accessor,
-                                                         using_left_relation,
-                                                         operand_attr_id,
-                                                         joined_tuple_ids);
+      return ColumnVectorPtr(
+          fast_operator_->applyToValueAccessorForJoin(operand_accessor,
+                                                      using_left_relation,
+                                                      operand_attr_id,
+                                                      joined_tuple_ids));
     }
 #endif  // QUICKSTEP_ENABLE_VECTOR_COPY_ELISION_JOIN
 
-    std::unique_ptr<ColumnVector> operand_result(
+    ColumnVectorPtr operand_result(
         operand_->getAllValuesForJoin(left_relation_id,
                                       left_accessor,
                                       right_relation_id,
                                       right_accessor,
-                                      joined_tuple_ids));
-    return fast_operator_->applyToColumnVector(*operand_result);
+                                      joined_tuple_ids,
+                                      cv_cache));
+    return ColumnVectorPtr(
+        fast_operator_->applyToColumnVector(*operand_result));
   }
 }
 
@@ -166,4 +177,35 @@ void ScalarUnaryExpression::initHelper(bool own_children) {
   }
 }
 
+void ScalarUnaryExpression::getFieldStringItems(
+    std::vector<std::string> *inline_field_names,
+    std::vector<std::string> *inline_field_values,
+    std::vector<std::string> *non_container_child_field_names,
+    std::vector<const Expression*> *non_container_child_fields,
+    std::vector<std::string> *container_child_field_names,
+    std::vector<std::vector<const Expression*>> *container_child_fields) const {
+  Scalar::getFieldStringItems(inline_field_names,
+                              inline_field_values,
+                              non_container_child_field_names,
+                              non_container_child_fields,
+                              container_child_field_names,
+                              container_child_fields);
+
+  if (fast_operator_ == nullptr) {
+    inline_field_names->emplace_back("static_value");
+    if (static_value_.isNull()) {
+      inline_field_values->emplace_back("NULL");
+    } else {
+      inline_field_values->emplace_back(type_.printValueToString(static_value_));
+    }
+  }
+
+  inline_field_names->emplace_back("operation");
+  inline_field_values->emplace_back(
+      kUnaryOperationNames[static_cast<int>(operation_.getUnaryOperationID())]);
+
+  non_container_child_field_names->emplace_back("operand");
+  non_container_child_fields->emplace_back(operand_.get());
+}
+
 }  // namespace quickstep

http://git-wip-us.apache.org/repos/asf/incubator-quickstep/blob/0fad9ec0/expressions/scalar/ScalarUnaryExpression.hpp
----------------------------------------------------------------------
diff --git a/expressions/scalar/ScalarUnaryExpression.hpp b/expressions/scalar/ScalarUnaryExpression.hpp
index 608a842..707d0b2 100644
--- a/expressions/scalar/ScalarUnaryExpression.hpp
+++ b/expressions/scalar/ScalarUnaryExpression.hpp
@@ -21,6 +21,7 @@
 #define QUICKSTEP_EXPRESSIONS_SCALAR_SCALAR_UNARY_EXPRESSION_HPP_
 
 #include <memory>
+#include <string>
 #include <utility>
 #include <vector>
 
@@ -29,6 +30,7 @@
 #include "expressions/scalar/Scalar.hpp"
 #include "storage/StorageBlockInfo.hpp"
 #include "types/TypedValue.hpp"
+#include "types/containers/ColumnVector.hpp"
 #include "types/operations/unary_operations/UnaryOperation.hpp"
 #include "utility/Macros.hpp"
 
@@ -36,7 +38,7 @@
 
 namespace quickstep {
 
-class ColumnVector;
+class ColumnVectorCache;
 class ValueAccessor;
 
 struct SubBlocksReference;
@@ -93,15 +95,26 @@ class ScalarUnaryExpression : public Scalar {
     return static_value_;
   }
 
-  ColumnVector* getAllValues(ValueAccessor *accessor,
-                             const SubBlocksReference *sub_blocks_ref) const override;
+  ColumnVectorPtr getAllValues(ValueAccessor *accessor,
+                               const SubBlocksReference *sub_blocks_ref,
+                               ColumnVectorCache *cv_cache) const override;
 
-  ColumnVector* getAllValuesForJoin(
+  ColumnVectorPtr getAllValuesForJoin(
       const relation_id left_relation_id,
       ValueAccessor *left_accessor,
       const relation_id right_relation_id,
       ValueAccessor *right_accessor,
-      const std::vector<std::pair<tuple_id, tuple_id>> &joined_tuple_ids) const override;
+      const std::vector<std::pair<tuple_id, tuple_id>> &joined_tuple_ids,
+      ColumnVectorCache *cv_cache) const override;
+
+ protected:
+  void getFieldStringItems(
+      std::vector<std::string> *inline_field_names,
+      std::vector<std::string> *inline_field_values,
+      std::vector<std::string> *non_container_child_field_names,
+      std::vector<const Expression*> *non_container_child_fields,
+      std::vector<std::string> *container_child_field_names,
+      std::vector<std::vector<const Expression*>> *container_child_fields) const override;
 
  private:
   void initHelper(bool own_children);

http://git-wip-us.apache.org/repos/asf/incubator-quickstep/blob/0fad9ec0/query_optimizer/CMakeLists.txt
----------------------------------------------------------------------
diff --git a/query_optimizer/CMakeLists.txt b/query_optimizer/CMakeLists.txt
index 08b6467..c969f16 100644
--- a/query_optimizer/CMakeLists.txt
+++ b/query_optimizer/CMakeLists.txt
@@ -214,12 +214,15 @@ target_link_libraries(quickstep_queryoptimizer_PhysicalGenerator
                       quickstep_queryoptimizer_logical_Logical
                       quickstep_queryoptimizer_physical_Physical
                       quickstep_queryoptimizer_rules_AttachLIPFilters
+                      quickstep_queryoptimizer_rules_CollapseSelection
+                      quickstep_queryoptimizer_rules_ExtractCommonSubexpression
                       quickstep_queryoptimizer_rules_FuseAggregateJoin
                       quickstep_queryoptimizer_rules_InjectJoinFilters
                       quickstep_queryoptimizer_rules_PruneColumns
                       quickstep_queryoptimizer_rules_PushDownLowCostDisjunctivePredicate
                       quickstep_queryoptimizer_rules_ReduceGroupByAttributes
                       quickstep_queryoptimizer_rules_ReorderColumns
+                      quickstep_queryoptimizer_rules_ReuseAggregateExpressions
                       quickstep_queryoptimizer_rules_StarSchemaHashJoinOrderOptimization
                       quickstep_queryoptimizer_rules_SwapProbeBuild
                       quickstep_queryoptimizer_strategy_Aggregate

http://git-wip-us.apache.org/repos/asf/incubator-quickstep/blob/0fad9ec0/query_optimizer/PhysicalGenerator.cpp
----------------------------------------------------------------------
diff --git a/query_optimizer/PhysicalGenerator.cpp b/query_optimizer/PhysicalGenerator.cpp
index ac51c31..4405761 100644
--- a/query_optimizer/PhysicalGenerator.cpp
+++ b/query_optimizer/PhysicalGenerator.cpp
@@ -27,12 +27,15 @@
 #include "query_optimizer/logical/Logical.hpp"
 #include "query_optimizer/physical/Physical.hpp"
 #include "query_optimizer/rules/AttachLIPFilters.hpp"
+#include "query_optimizer/rules/CollapseSelection.hpp"
+#include "query_optimizer/rules/ExtractCommonSubexpression.hpp"
 #include "query_optimizer/rules/FuseAggregateJoin.hpp"
 #include "query_optimizer/rules/InjectJoinFilters.hpp"
 #include "query_optimizer/rules/PruneColumns.hpp"
 #include "query_optimizer/rules/PushDownLowCostDisjunctivePredicate.hpp"
 #include "query_optimizer/rules/ReduceGroupByAttributes.hpp"
 #include "query_optimizer/rules/ReorderColumns.hpp"
+#include "query_optimizer/rules/ReuseAggregateExpressions.hpp"
 #include "query_optimizer/rules/StarSchemaHashJoinOrderOptimization.hpp"
 #include "query_optimizer/rules/SwapProbeBuild.hpp"
 #include "query_optimizer/strategy/Aggregate.hpp"
@@ -146,8 +149,16 @@ P::PhysicalPtr PhysicalGenerator::optimizePlan() {
     rules.emplace_back(new ReorderColumns());
   }
 
+  rules.emplace_back(new ReuseAggregateExpressions(optimizer_context_));
+
   rules.emplace_back(new FuseAggregateJoin());
 
+  rules.emplace_back(new CollapseSelection());
+
+  rules.emplace_back(new PruneColumns());
+
+  rules.emplace_back(new ExtractCommonSubexpression(optimizer_context_));
+
   // NOTE(jianqiao): Adding rules after InjectJoinFilters (or AttachLIPFilters) requires
   // extra handling of LIPFilterConfiguration for transformed nodes. So currently it is
   // suggested that all the new rules be placed before this point.
@@ -165,7 +176,8 @@ P::PhysicalPtr PhysicalGenerator::optimizePlan() {
              << physical_plan_->toString();
   }
 
-  DVLOG(4) << "Optimized physical plan:\n" << physical_plan_->toString();
+//  DVLOG(4) << "Optimized physical plan:\n" << physical_plan_->toString();
+  std::cerr << "Optimized physical plan:\n" << physical_plan_->toString();
 
   if (FLAGS_visualize_plan) {
     quickstep::PlanVisualizer plan_visualizer;

http://git-wip-us.apache.org/repos/asf/incubator-quickstep/blob/0fad9ec0/query_optimizer/expressions/AttributeReference.cpp
----------------------------------------------------------------------
diff --git a/query_optimizer/expressions/AttributeReference.cpp b/query_optimizer/expressions/AttributeReference.cpp
index f0e49d4..5dc59bb 100644
--- a/query_optimizer/expressions/AttributeReference.cpp
+++ b/query_optimizer/expressions/AttributeReference.cpp
@@ -19,6 +19,7 @@
 
 #include "query_optimizer/expressions/AttributeReference.hpp"
 
+#include <functional>
 #include <string>
 #include <unordered_map>
 #include <vector>
@@ -26,6 +27,7 @@
 #include "expressions/scalar/ScalarAttribute.hpp"
 #include "query_optimizer/expressions/ExprId.hpp"
 #include "query_optimizer/expressions/Expression.hpp"
+#include "query_optimizer/expressions/PatternMatcher.hpp"
 
 #include "glog/logging.h"
 
@@ -57,6 +59,22 @@ std::vector<AttributeReferencePtr> AttributeReference::getReferencedAttributes()
   return new ::quickstep::ScalarAttribute(*found_it->second);
 }
 
+std::size_t AttributeReference::computeHash() const {
+  return std::hash<std::size_t>()(static_cast<std::size_t>(id()));
+}
+
+bool AttributeReference::equals(const ScalarPtr &other) const {
+  AttributeReferencePtr attr;
+  if (SomeAttributeReference::MatchesWithConditionalCast(other, &attr)) {
+    if (id() != attr->id()) {
+      return false;
+    }
+    DCHECK(type_.equals(attr->type_));
+    return true;
+  }
+  return false;
+}
+
 void AttributeReference::getFieldStringItems(
     std::vector<std::string> *inline_field_names,
     std::vector<std::string> *inline_field_values,

http://git-wip-us.apache.org/repos/asf/incubator-quickstep/blob/0fad9ec0/query_optimizer/expressions/AttributeReference.hpp
----------------------------------------------------------------------
diff --git a/query_optimizer/expressions/AttributeReference.hpp b/query_optimizer/expressions/AttributeReference.hpp
index f5207b1..27d8bcb 100644
--- a/query_optimizer/expressions/AttributeReference.hpp
+++ b/query_optimizer/expressions/AttributeReference.hpp
@@ -88,6 +88,8 @@ class AttributeReference : public NamedExpression {
   ::quickstep::Scalar* concretize(
       const std::unordered_map<ExprId, const CatalogAttribute*> &substitution_map) const override;
 
+  bool equals(const ScalarPtr &other) const override;
+
   /**
    * @brief Creates an immutable AttributReference.
    *
@@ -114,6 +116,8 @@ class AttributeReference : public NamedExpression {
   }
 
  protected:
+  std::size_t computeHash() const override;
+
   void getFieldStringItems(
      std::vector<std::string> *inline_field_names,
      std::vector<std::string> *inline_field_values,

http://git-wip-us.apache.org/repos/asf/incubator-quickstep/blob/0fad9ec0/query_optimizer/expressions/BinaryExpression.cpp
----------------------------------------------------------------------
diff --git a/query_optimizer/expressions/BinaryExpression.cpp b/query_optimizer/expressions/BinaryExpression.cpp
index 446dd55..a9ecfb1 100644
--- a/query_optimizer/expressions/BinaryExpression.cpp
+++ b/query_optimizer/expressions/BinaryExpression.cpp
@@ -19,6 +19,7 @@
 
 #include "query_optimizer/expressions/BinaryExpression.hpp"
 
+#include <algorithm>
 #include <string>
 #include <unordered_map>
 #include <vector>
@@ -31,6 +32,7 @@
 #include "query_optimizer/expressions/PatternMatcher.hpp"
 #include "types/operations/binary_operations/BinaryOperation.hpp"
 #include "types/operations/binary_operations/BinaryOperationID.hpp"
+#include "utility/HashPair.hpp"
 
 #include "glog/logging.h"
 
@@ -104,6 +106,40 @@ std::vector<AttributeReferencePtr> BinaryExpression::getReferencedAttributes() c
       right_->concretize(substitution_map));
 }
 
+std::size_t BinaryExpression::computeHash() const {
+  std::size_t left_hash = left_->hash();
+  std::size_t right_hash = right_->hash();
+
+  if (operation_.isCommutative() && left_hash > right_hash) {
+    std::swap(left_hash, right_hash);
+  }
+
+  return CombineHashes(
+      CombineHashes(static_cast<std::size_t>(ExpressionType::kBinaryExpression),
+                    static_cast<std::size_t>(operation_.getBinaryOperationID())),
+      CombineHashes(left_hash, right_hash));
+}
+
+bool BinaryExpression::equals(const ScalarPtr &other) const {
+  BinaryExpressionPtr expr;
+  if (SomeBinaryExpression::MatchesWithConditionalCast(other, &expr)) {
+    ScalarPtr left = left_;
+    ScalarPtr right = right_;
+
+    if (operation_.isCommutative()) {
+      const bool self_order = (left_->hash() < right_->hash());
+      const bool other_order = (expr->left_->hash() < expr->right_->hash());
+      if (self_order ^ other_order) {
+        std::swap(left, right);
+      }
+    }
+
+    return operation_.getBinaryOperationID() == expr->operation_.getBinaryOperationID()
+           && left->equals(expr->left_) && right->equals(expr->right_);
+  }
+  return false;
+}
+
 void BinaryExpression::getFieldStringItems(
     std::vector<std::string> *inline_field_names,
     std::vector<std::string> *inline_field_values,

http://git-wip-us.apache.org/repos/asf/incubator-quickstep/blob/0fad9ec0/query_optimizer/expressions/BinaryExpression.hpp
----------------------------------------------------------------------
diff --git a/query_optimizer/expressions/BinaryExpression.hpp b/query_optimizer/expressions/BinaryExpression.hpp
index 9b11ed1..6a37679 100644
--- a/query_optimizer/expressions/BinaryExpression.hpp
+++ b/query_optimizer/expressions/BinaryExpression.hpp
@@ -90,6 +90,8 @@ class BinaryExpression : public Scalar {
   ::quickstep::Scalar* concretize(
       const std::unordered_map<ExprId, const CatalogAttribute*> &substitution_map) const override;
 
+  bool equals(const ScalarPtr &other) const override;
+
   static BinaryExpressionPtr Create(const BinaryOperation &operation,
                                     const ScalarPtr &left,
                                     const ScalarPtr &right) {
@@ -97,6 +99,8 @@ class BinaryExpression : public Scalar {
   }
 
  protected:
+  std::size_t computeHash() const override;
+
   void getFieldStringItems(
       std::vector<std::string> *inline_field_names,
       std::vector<std::string> *inline_field_values,

http://git-wip-us.apache.org/repos/asf/incubator-quickstep/blob/0fad9ec0/query_optimizer/expressions/CMakeLists.txt
----------------------------------------------------------------------
diff --git a/query_optimizer/expressions/CMakeLists.txt b/query_optimizer/expressions/CMakeLists.txt
index 35fac90..2a5f610 100644
--- a/query_optimizer/expressions/CMakeLists.txt
+++ b/query_optimizer/expressions/CMakeLists.txt
@@ -21,7 +21,11 @@ add_library(quickstep_queryoptimizer_expressions_Alias Alias.cpp Alias.hpp)
 add_library(quickstep_queryoptimizer_expressions_AttributeReference AttributeReference.cpp AttributeReference.hpp)
 add_library(quickstep_queryoptimizer_expressions_BinaryExpression BinaryExpression.cpp BinaryExpression.hpp)
 add_library(quickstep_queryoptimizer_expressions_Cast Cast.cpp Cast.hpp)
-add_library(quickstep_queryoptimizer_expressions_ComparisonExpression ComparisonExpression.cpp
+add_library(quickstep_queryoptimizer_expressions_CommonSubexpression
+            CommonSubexpression.cpp
+            CommonSubexpression.hpp)
+add_library(quickstep_queryoptimizer_expressions_ComparisonExpression
+            ComparisonExpression.cpp
             ComparisonExpression.hpp)
 add_library(quickstep_queryoptimizer_expressions_Exists Exists.cpp Exists.hpp)
 add_library(quickstep_queryoptimizer_expressions_Expression ../../empty_src.cpp Expression.hpp)
@@ -43,7 +47,9 @@ add_library(quickstep_queryoptimizer_expressions_SearchedCase SearchedCase.cpp S
 add_library(quickstep_queryoptimizer_expressions_SimpleCase SimpleCase.cpp SimpleCase.hpp)
 add_library(quickstep_queryoptimizer_expressions_SubqueryExpression SubqueryExpression.cpp SubqueryExpression.hpp)
 add_library(quickstep_queryoptimizer_expressions_UnaryExpression UnaryExpression.cpp UnaryExpression.hpp)
-add_library(quickstep_queryoptimizer_expressions_WindowAggregateFunction WindowAggregateFunction.cpp WindowAggregateFunction.hpp)
+add_library(quickstep_queryoptimizer_expressions_WindowAggregateFunction
+            WindowAggregateFunction.cpp
+            WindowAggregateFunction.hpp)
 
 # Link dependencies:
 target_link_libraries(quickstep_queryoptimizer_expressions_AggregateFunction
@@ -78,6 +84,7 @@ target_link_libraries(quickstep_queryoptimizer_expressions_AttributeReference
                       quickstep_queryoptimizer_expressions_Expression
                       quickstep_queryoptimizer_expressions_ExpressionType
                       quickstep_queryoptimizer_expressions_NamedExpression
+                      quickstep_queryoptimizer_expressions_PatternMatcher
                       quickstep_utility_Macros)
 target_link_libraries(quickstep_queryoptimizer_expressions_BinaryExpression
                       glog
@@ -91,6 +98,7 @@ target_link_libraries(quickstep_queryoptimizer_expressions_BinaryExpression
                       quickstep_queryoptimizer_expressions_Scalar
                       quickstep_types_operations_binaryoperations_BinaryOperation
                       quickstep_types_operations_binaryoperations_BinaryOperationID
+                      quickstep_utility_HashPair
                       quickstep_utility_Macros)
 target_link_libraries(quickstep_queryoptimizer_expressions_Cast
                       glog
@@ -105,6 +113,18 @@ target_link_libraries(quickstep_queryoptimizer_expressions_Cast
                       quickstep_queryoptimizer_expressions_Scalar
                       quickstep_types_Type
                       quickstep_types_operations_unaryoperations_NumericCastOperation
+                      quickstep_utility_HashPair
+                      quickstep_utility_Macros)
+target_link_libraries(quickstep_queryoptimizer_expressions_CommonSubexpression
+                      glog
+                      quickstep_expressions_scalar_ScalarSharedExpression
+                      quickstep_queryoptimizer_OptimizerTree
+                      quickstep_queryoptimizer_expressions_AttributeReference
+                      quickstep_queryoptimizer_expressions_ExprId
+                      quickstep_queryoptimizer_expressions_Expression
+                      quickstep_queryoptimizer_expressions_ExpressionType
+                      quickstep_queryoptimizer_expressions_PatternMatcher
+                      quickstep_queryoptimizer_expressions_Scalar
                       quickstep_utility_Macros)
 target_link_libraries(quickstep_queryoptimizer_expressions_ComparisonExpression
                       glog
@@ -233,6 +253,7 @@ target_link_libraries(quickstep_queryoptimizer_expressions_Scalar
                       glog
                       quickstep_queryoptimizer_expressions_ExprId
                       quickstep_queryoptimizer_expressions_Expression
+                      quickstep_utility_HashError
                       quickstep_utility_Macros)
 target_link_libraries(quickstep_queryoptimizer_expressions_ScalarLiteral
                       glog
@@ -242,9 +263,11 @@ target_link_libraries(quickstep_queryoptimizer_expressions_ScalarLiteral
                       quickstep_queryoptimizer_expressions_ExprId
                       quickstep_queryoptimizer_expressions_Expression
                       quickstep_queryoptimizer_expressions_ExpressionType
+                      quickstep_queryoptimizer_expressions_PatternMatcher
                       quickstep_queryoptimizer_expressions_Scalar
                       quickstep_types_Type
                       quickstep_types_TypedValue
+                      quickstep_utility_HashPair
                       quickstep_utility_Macros)
 target_link_libraries(quickstep_queryoptimizer_expressions_SearchedCase
                       quickstep_expressions_predicate_Predicate
@@ -272,12 +295,14 @@ target_link_libraries(quickstep_queryoptimizer_expressions_SimpleCase
                       quickstep_queryoptimizer_expressions_ExprId
                       quickstep_queryoptimizer_expressions_Expression
                       quickstep_queryoptimizer_expressions_ExpressionType
+                      quickstep_queryoptimizer_expressions_PatternMatcher
                       quickstep_queryoptimizer_expressions_Predicate
                       quickstep_queryoptimizer_expressions_Scalar
                       quickstep_types_Type
                       quickstep_types_operations_comparisons_ComparisonFactory
                       quickstep_types_operations_comparisons_ComparisonID
                       quickstep_utility_Cast
+                      quickstep_utility_HashPair
                       quickstep_utility_Macros)
 target_link_libraries(quickstep_queryoptimizer_expressions_SubqueryExpression
                       glog
@@ -301,6 +326,7 @@ target_link_libraries(quickstep_queryoptimizer_expressions_UnaryExpression
                       quickstep_queryoptimizer_expressions_Scalar
                       quickstep_types_operations_unaryoperations_UnaryOperation
                       quickstep_types_operations_unaryoperations_UnaryOperationID
+                      quickstep_utility_HashPair
                       quickstep_utility_Macros)
 target_link_libraries(quickstep_queryoptimizer_expressions_WindowAggregateFunction
                       glog
@@ -324,6 +350,7 @@ target_link_libraries(quickstep_queryoptimizer_expressions
                       quickstep_queryoptimizer_expressions_AttributeReference
                       quickstep_queryoptimizer_expressions_BinaryExpression
                       quickstep_queryoptimizer_expressions_Cast
+                      quickstep_queryoptimizer_expressions_CommonSubexpression
                       quickstep_queryoptimizer_expressions_ComparisonExpression
                       quickstep_queryoptimizer_expressions_Exists
                       quickstep_queryoptimizer_expressions_Expression

http://git-wip-us.apache.org/repos/asf/incubator-quickstep/blob/0fad9ec0/query_optimizer/expressions/Cast.cpp
----------------------------------------------------------------------
diff --git a/query_optimizer/expressions/Cast.cpp b/query_optimizer/expressions/Cast.cpp
index c0813c5..f4cac8b 100644
--- a/query_optimizer/expressions/Cast.cpp
+++ b/query_optimizer/expressions/Cast.cpp
@@ -33,6 +33,7 @@
 #include "query_optimizer/expressions/Scalar.hpp"
 #include "types/Type.hpp"
 #include "types/operations/unary_operations/NumericCastOperation.hpp"
+#include "utility/HashPair.hpp"
 
 #include "glog/logging.h"
 
@@ -55,6 +56,21 @@ ExpressionPtr Cast::copyWithNewChildren(
                                                 operand_->concretize(substitution_map));
 }
 
+std::size_t Cast::computeHash() const {
+  return CombineHashes(
+      CombineHashes(static_cast<std::size_t>(ExpressionType::kCast),
+                    operand_->hash()),
+      static_cast<std::size_t>(target_type_.getTypeID()));
+}
+
+bool Cast::equals(const ScalarPtr &other) const {
+  CastPtr expr;
+  if (SomeCast::MatchesWithConditionalCast(other, &expr)) {
+    return operand_->equals(expr->operand_) && target_type_.equals(expr->target_type_);
+  }
+  return false;
+}
+
 void Cast::getFieldStringItems(
     std::vector<std::string> *inline_field_names,
     std::vector<std::string> *inline_field_values,

http://git-wip-us.apache.org/repos/asf/incubator-quickstep/blob/0fad9ec0/query_optimizer/expressions/Cast.hpp
----------------------------------------------------------------------
diff --git a/query_optimizer/expressions/Cast.hpp b/query_optimizer/expressions/Cast.hpp
index ac5bd02..11be775 100644
--- a/query_optimizer/expressions/Cast.hpp
+++ b/query_optimizer/expressions/Cast.hpp
@@ -78,6 +78,8 @@ class Cast : public Scalar {
   ::quickstep::Scalar* concretize(
       const std::unordered_map<ExprId, const CatalogAttribute*> &substitution_map) const override;
 
+  bool equals(const ScalarPtr &other) const override;
+
   /**
    * @brief Creates a Cast expression that converts \p operand to \p target_type.
    *
@@ -90,6 +92,8 @@ class Cast : public Scalar {
   }
 
  protected:
+  std::size_t computeHash() const override;
+
   void getFieldStringItems(
       std::vector<std::string> *inline_field_names,
       std::vector<std::string> *inline_field_values,

http://git-wip-us.apache.org/repos/asf/incubator-quickstep/blob/0fad9ec0/query_optimizer/expressions/CommonSubexpression.cpp
----------------------------------------------------------------------
diff --git a/query_optimizer/expressions/CommonSubexpression.cpp b/query_optimizer/expressions/CommonSubexpression.cpp
new file mode 100644
index 0000000..558b1fa
--- /dev/null
+++ b/query_optimizer/expressions/CommonSubexpression.cpp
@@ -0,0 +1,70 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ **/
+
+#include "query_optimizer/expressions/CommonSubexpression.hpp"
+
+#include <string>
+#include <unordered_map>
+#include <vector>
+
+#include "expressions/scalar/ScalarSharedExpression.hpp"
+#include "query_optimizer/OptimizerTree.hpp"
+#include "query_optimizer/expressions/ExprId.hpp"
+#include "query_optimizer/expressions/Expression.hpp"
+#include "query_optimizer/expressions/PatternMatcher.hpp"
+#include "query_optimizer/expressions/Scalar.hpp"
+
+#include "glog/logging.h"
+
+namespace quickstep {
+namespace optimizer {
+namespace expressions {
+
+ExpressionPtr CommonSubexpression::copyWithNewChildren(
+    const std::vector<ExpressionPtr> &new_children) const {
+  DCHECK_EQ(new_children.size(), children().size());
+  DCHECK(SomeScalar::Matches(new_children[0]));
+  return CommonSubexpression::Create(
+      common_subexpression_id_,
+      std::static_pointer_cast<const Scalar>(new_children[0]));
+}
+
+::quickstep::Scalar* CommonSubexpression::concretize(
+    const std::unordered_map<ExprId, const CatalogAttribute*> &substitution_map) const {
+  return new ::quickstep::ScalarSharedExpression(
+      common_subexpression_id_, operand_->concretize(substitution_map));
+}
+
+void CommonSubexpression::getFieldStringItems(
+    std::vector<std::string> *inline_field_names,
+    std::vector<std::string> *inline_field_values,
+    std::vector<std::string> *non_container_child_field_names,
+    std::vector<OptimizerTreeBaseNodePtr> *non_container_child_fields,
+    std::vector<std::string> *container_child_field_names,
+    std::vector<std::vector<OptimizerTreeBaseNodePtr>> *container_child_fields) const {
+  inline_field_names->push_back("common_subexpression_id");
+  inline_field_values->push_back(std::to_string(common_subexpression_id_));
+
+  non_container_child_field_names->push_back("Operand");
+  non_container_child_fields->push_back(operand_);
+}
+
+}  // namespace expressions
+}  // namespace optimizer
+}  // namespace quickstep

http://git-wip-us.apache.org/repos/asf/incubator-quickstep/blob/0fad9ec0/query_optimizer/expressions/CommonSubexpression.hpp
----------------------------------------------------------------------
diff --git a/query_optimizer/expressions/CommonSubexpression.hpp b/query_optimizer/expressions/CommonSubexpression.hpp
new file mode 100644
index 0000000..c642996
--- /dev/null
+++ b/query_optimizer/expressions/CommonSubexpression.hpp
@@ -0,0 +1,133 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ **/
+
+#ifndef QUICKSTEP_QUERY_OPTIMIZER_EXPRESSIONS_COMMON_SUBEXPRESSION_HPP_
+#define QUICKSTEP_QUERY_OPTIMIZER_EXPRESSIONS_COMMON_SUBEXPRESSION_HPP_
+
+#include <memory>
+#include <string>
+#include <unordered_map>
+#include <vector>
+
+#include "query_optimizer/expressions/AttributeReference.hpp"
+#include "query_optimizer/expressions/ExprId.hpp"
+#include "query_optimizer/expressions/Expression.hpp"
+#include "query_optimizer/expressions/ExpressionType.hpp"
+#include "query_optimizer/expressions/Scalar.hpp"
+#include "utility/Macros.hpp"
+
+#include "glog/logging.h"
+
+namespace quickstep {
+
+class Scalar;
+class Type;
+
+namespace optimizer {
+namespace expressions {
+
+/** \addtogroup OptimizerExpressions
+ *  @{
+ */
+
+class CommonSubexpression;
+typedef std::shared_ptr<const CommonSubexpression> CommonSubexpressionPtr;
+
+class CommonSubexpression : public Scalar {
+ public:
+  ExpressionType getExpressionType() const override {
+    return ExpressionType::kCommonSubexpression;
+  }
+
+  std::string getName() const override {
+    return "CommonSubexpression";
+  }
+
+  bool isConstant() const override {
+    return operand_->isConstant();
+  }
+
+  inline ExprId common_subexpression_id() const {
+    return common_subexpression_id_;
+  }
+
+  /**
+   * @return The operand that represents the common subexpression.
+   */
+  const ScalarPtr& operand() const {
+    return operand_;
+  }
+
+  const Type& getValueType() const override {
+    return operand_->getValueType();
+  }
+
+  ExpressionPtr copyWithNewChildren(
+      const std::vector<ExpressionPtr> &new_children) const override;
+
+  std::vector<AttributeReferencePtr> getReferencedAttributes() const override {
+    return operand_->getReferencedAttributes();
+  }
+
+  ::quickstep::Scalar* concretize(
+      const std::unordered_map<ExprId, const CatalogAttribute*> &substitution_map) const override;
+
+  /**
+   * @brief Creates an immutable CommonSubexpression.
+   *
+   * @param operand The operand that represents the common subexpression.
+   * @return An immutable CommonSubexpression that is shared among multiple
+   *         expressions.
+   */
+  static CommonSubexpressionPtr Create(const ExprId common_subexpression_id,
+                                       const ScalarPtr &operand) {
+    return CommonSubexpressionPtr(
+        new CommonSubexpression(common_subexpression_id, operand));
+  }
+
+ protected:
+  void getFieldStringItems(
+      std::vector<std::string> *inline_field_names,
+      std::vector<std::string> *inline_field_values,
+      std::vector<std::string> *non_container_child_field_names,
+      std::vector<OptimizerTreeBaseNodePtr> *non_container_child_fields,
+      std::vector<std::string> *container_child_field_names,
+      std::vector<std::vector<OptimizerTreeBaseNodePtr>> *container_child_fields) const override;
+
+ private:
+  CommonSubexpression(const ExprId common_subexpression_id,
+                      const ScalarPtr &operand)
+      : common_subexpression_id_(common_subexpression_id),
+        operand_(operand) {
+    addChild(operand);
+  }
+
+  ExprId common_subexpression_id_;
+  ScalarPtr operand_;
+
+  DISALLOW_COPY_AND_ASSIGN(CommonSubexpression);
+};
+
+/** @} */
+
+}  // namespace expressions
+}  // namespace optimizer
+}  // namespace quickstep
+
+#endif  // QUICKSTEP_QUERY_OPTIMIZER_EXPRESSIONS_COMMON_SUBEXPRESSION_HPP_

http://git-wip-us.apache.org/repos/asf/incubator-quickstep/blob/0fad9ec0/query_optimizer/expressions/ExpressionType.hpp
----------------------------------------------------------------------
diff --git a/query_optimizer/expressions/ExpressionType.hpp b/query_optimizer/expressions/ExpressionType.hpp
index 5008f1d..ba7f639 100644
--- a/query_optimizer/expressions/ExpressionType.hpp
+++ b/query_optimizer/expressions/ExpressionType.hpp
@@ -32,11 +32,12 @@ namespace expressions {
  * @brief Optimizer expression types.
  **/
 enum class ExpressionType {
-  kAggregateFunction,
+  kAggregateFunction = 0,
   kAlias,
   kAttributeReference,
   kBinaryExpression,
   kCast,
+  kCommonSubexpression,
   kComparisonExpression,
   kExists,
   kInTableQuery,

http://git-wip-us.apache.org/repos/asf/incubator-quickstep/blob/0fad9ec0/query_optimizer/expressions/ExpressionUtil.hpp
----------------------------------------------------------------------
diff --git a/query_optimizer/expressions/ExpressionUtil.hpp b/query_optimizer/expressions/ExpressionUtil.hpp
index 6b8666e..29d90f0 100644
--- a/query_optimizer/expressions/ExpressionUtil.hpp
+++ b/query_optimizer/expressions/ExpressionUtil.hpp
@@ -85,9 +85,9 @@ template <class NamedExpressionType1, class NamedExpressionType2>
 bool ContainsExpression(
     const std::vector<std::shared_ptr<const NamedExpressionType1>> &expressions,
     const std::shared_ptr<const NamedExpressionType2> &expression_to_check) {
-  for (const std::shared_ptr<const NamedExpressionType1> &expression :
-       expressions) {
-    if (expression->equals(expression_to_check)) {
+  for (const auto &expression : expressions) {
+    if (expression->id() == expression_to_check->id()) {
+      DCHECK(expression->getExpressionType() == expression_to_check->getExpressionType());
       return true;
     }
   }

http://git-wip-us.apache.org/repos/asf/incubator-quickstep/blob/0fad9ec0/query_optimizer/expressions/NamedExpression.cpp
----------------------------------------------------------------------
diff --git a/query_optimizer/expressions/NamedExpression.cpp b/query_optimizer/expressions/NamedExpression.cpp
index 992a84a..2c2beac 100644
--- a/query_optimizer/expressions/NamedExpression.cpp
+++ b/query_optimizer/expressions/NamedExpression.cpp
@@ -25,6 +25,8 @@
 #include "query_optimizer/OptimizerTree.hpp"
 #include "types/Type.hpp"
 
+#include "glog/logging.h"
+
 namespace quickstep {
 namespace optimizer {
 namespace expressions {

http://git-wip-us.apache.org/repos/asf/incubator-quickstep/blob/0fad9ec0/query_optimizer/expressions/NamedExpression.hpp
----------------------------------------------------------------------
diff --git a/query_optimizer/expressions/NamedExpression.hpp b/query_optimizer/expressions/NamedExpression.hpp
index 9de8005..6725567 100644
--- a/query_optimizer/expressions/NamedExpression.hpp
+++ b/query_optimizer/expressions/NamedExpression.hpp
@@ -69,19 +69,6 @@ class NamedExpression : public Scalar {
    */
   inline const std::string& relation_name() const { return relation_name_; }
 
-  /**
-   * @brief Compares this named expression with \p other. Two named expressions
-   *        are equal if they have the same ExprId and are both Alias or
-   *        AttributeReference.
-   *
-   * @param other Another named expression to compare with.
-   * @return True if the named expression is equal to \p other.
-   */
-  inline bool equals(const NamedExpressionPtr &other) const {
-    return getExpressionType() == other->getExpressionType() &&
-           id_ == other->id();
-  }
-
  protected:
   /**
    * @brief Constructor.

http://git-wip-us.apache.org/repos/asf/incubator-quickstep/blob/0fad9ec0/query_optimizer/expressions/PatternMatcher.hpp
----------------------------------------------------------------------
diff --git a/query_optimizer/expressions/PatternMatcher.hpp b/query_optimizer/expressions/PatternMatcher.hpp
index 18d6b1c..e30a4d9 100644
--- a/query_optimizer/expressions/PatternMatcher.hpp
+++ b/query_optimizer/expressions/PatternMatcher.hpp
@@ -35,6 +35,7 @@ class Avg;
 class AttributeReference;
 class BinaryExpression;
 class Cast;
+class CommonSubexpression;
 class ComparisonExpression;
 class Count;
 class Exists;
@@ -50,6 +51,7 @@ class Predicate;
 class PredicateLiteral;
 class Scalar;
 class ScalarLiteral;
+class SimpleCase;
 class Sum;
 class UnaryExpression;
 class WindowAggregateFunction;
@@ -145,16 +147,13 @@ using SomeScalar = SomeExpressionNode<Scalar,
                                       ExpressionType::kAttributeReference,
                                       ExpressionType::kBinaryExpression,
                                       ExpressionType::kCast,
-                                      ExpressionType::kComparisonExpression,
-                                      ExpressionType::kLogicalAnd,
-                                      ExpressionType::kLogicalNot,
-                                      ExpressionType::kLogicalOr,
-                                      ExpressionType::kPredicateLiteral,
+                                      ExpressionType::kCommonSubexpression,
                                       ExpressionType::kScalarLiteral,
                                       ExpressionType::kSearchedCase,
                                       ExpressionType::kSimpleCase,
                                       ExpressionType::kUnaryExpression>;
 using SomeScalarLiteral = SomeExpressionNode<ScalarLiteral, ExpressionType::kScalarLiteral>;
+using SomeSimpleCase = SomeExpressionNode<SimpleCase, ExpressionType::kSimpleCase>;
 using SomeUnaryExpression = SomeExpressionNode<UnaryExpression, ExpressionType::kUnaryExpression>;
 using SomeWindowAggregateFunction = SomeExpressionNode<WindowAggregateFunction,
                                                        ExpressionType::kWindowAggregateFunction>;

http://git-wip-us.apache.org/repos/asf/incubator-quickstep/blob/0fad9ec0/query_optimizer/expressions/Scalar.hpp
----------------------------------------------------------------------
diff --git a/query_optimizer/expressions/Scalar.hpp b/query_optimizer/expressions/Scalar.hpp
index 4870118..36a8de5 100644
--- a/query_optimizer/expressions/Scalar.hpp
+++ b/query_optimizer/expressions/Scalar.hpp
@@ -20,11 +20,13 @@
 #ifndef QUICKSTEP_QUERY_OPTIMIZER_EXPRESSIONS_SCALAR_HPP_
 #define QUICKSTEP_QUERY_OPTIMIZER_EXPRESSIONS_SCALAR_HPP_
 
+#include <cstddef>
 #include <memory>
 #include <unordered_map>
 
 #include "query_optimizer/expressions/Expression.hpp"
 #include "query_optimizer/expressions/ExprId.hpp"
+#include "utility/HashError.hpp"
 #include "utility/Macros.hpp"
 
 namespace quickstep {
@@ -65,10 +67,27 @@ class Scalar : public Expression {
       const std::unordered_map<ExprId, const CatalogAttribute*>& substitution_map)
       const = 0;
 
+  virtual bool equals(const ScalarPtr &other) const {
+    return false;
+  }
+
+  std::size_t hash() const {
+    if (hash_cache_ == nullptr) {
+      hash_cache_ = std::make_unique<std::size_t>(computeHash());
+    }
+    return *hash_cache_;
+  }
+
  protected:
   Scalar() {}
 
+  virtual std::size_t computeHash() const {
+    throw HashNotSupported("Unsupported computeHash() in " + getName());
+  }
+
  private:
+  mutable std::unique_ptr<std::size_t> hash_cache_;
+
   DISALLOW_COPY_AND_ASSIGN(Scalar);
 };
 

http://git-wip-us.apache.org/repos/asf/incubator-quickstep/blob/0fad9ec0/query_optimizer/expressions/ScalarLiteral.cpp
----------------------------------------------------------------------
diff --git a/query_optimizer/expressions/ScalarLiteral.cpp b/query_optimizer/expressions/ScalarLiteral.cpp
index d70c4cf..180d760 100644
--- a/query_optimizer/expressions/ScalarLiteral.cpp
+++ b/query_optimizer/expressions/ScalarLiteral.cpp
@@ -28,7 +28,9 @@
 #include "query_optimizer/expressions/AttributeReference.hpp"
 #include "query_optimizer/expressions/ExprId.hpp"
 #include "query_optimizer/expressions/Expression.hpp"
+#include "query_optimizer/expressions/PatternMatcher.hpp"
 #include "types/Type.hpp"
+#include "utility/HashPair.hpp"
 
 #include "glog/logging.h"
 
@@ -51,6 +53,19 @@ ExpressionPtr ScalarLiteral::copyWithNewChildren(
   return new ::quickstep::ScalarLiteral(value_, value_type_);
 }
 
+std::size_t ScalarLiteral::computeHash() const {
+  return CombineHashes(static_cast<std::size_t>(ExpressionType::kScalarLiteral),
+                       value_.getHash());
+}
+
+bool ScalarLiteral::equals(const ScalarPtr &other) const {
+  ScalarLiteralPtr lit;
+  if (SomeScalarLiteral::MatchesWithConditionalCast(other, &lit)) {
+    return value_type_.equals(lit->getValueType()) && value_.fastEqualCheck(lit->value());
+  }
+  return false;
+}
+
 void ScalarLiteral::getFieldStringItems(
     std::vector<std::string> *inline_field_names,
     std::vector<std::string> *inline_field_values,

http://git-wip-us.apache.org/repos/asf/incubator-quickstep/blob/0fad9ec0/query_optimizer/expressions/ScalarLiteral.hpp
----------------------------------------------------------------------
diff --git a/query_optimizer/expressions/ScalarLiteral.hpp b/query_optimizer/expressions/ScalarLiteral.hpp
index 8ebc41c..8a73405 100644
--- a/query_optimizer/expressions/ScalarLiteral.hpp
+++ b/query_optimizer/expressions/ScalarLiteral.hpp
@@ -81,6 +81,8 @@ class ScalarLiteral : public Scalar {
   ::quickstep::Scalar* concretize(
       const std::unordered_map<ExprId, const CatalogAttribute*> &substitution_map) const override;
 
+  bool equals(const ScalarPtr &other) const override;
+
   /**
    * @brief Creates an immutable ScalarLiteral.
    * @param literal_value The literal value.
@@ -92,6 +94,8 @@ class ScalarLiteral : public Scalar {
   }
 
  protected:
+  std::size_t computeHash() const override;
+
   void getFieldStringItems(
       std::vector<std::string> *inline_field_names,
       std::vector<std::string> *inline_field_values,

http://git-wip-us.apache.org/repos/asf/incubator-quickstep/blob/0fad9ec0/query_optimizer/expressions/SimpleCase.cpp
----------------------------------------------------------------------
diff --git a/query_optimizer/expressions/SimpleCase.cpp b/query_optimizer/expressions/SimpleCase.cpp
index 454d7b9..ccdd8e5 100644
--- a/query_optimizer/expressions/SimpleCase.cpp
+++ b/query_optimizer/expressions/SimpleCase.cpp
@@ -31,12 +31,14 @@
 #include "query_optimizer/expressions/AttributeReference.hpp"
 #include "query_optimizer/expressions/ComparisonExpression.hpp"
 #include "query_optimizer/expressions/Expression.hpp"
+#include "query_optimizer/expressions/PatternMatcher.hpp"
 #include "query_optimizer/expressions/Predicate.hpp"
 #include "query_optimizer/expressions/Scalar.hpp"
 #include "types/Type.hpp"
 #include "types/operations/comparisons/ComparisonID.hpp"
 #include "types/operations/comparisons/ComparisonFactory.hpp"
 #include "utility/Cast.hpp"
+#include "utility/HashPair.hpp"
 
 #include "glog/logging.h"
 
@@ -161,6 +163,50 @@ ExpressionPtr SimpleCase::copyWithNewChildren(const std::vector<ExpressionPtr> &
       else_result_expression.release());
 }
 
+std::size_t SimpleCase::computeHash() const {
+  std::size_t hash_code =
+      CombineHashes(static_cast<std::size_t>(ExpressionType::kSimpleCase),
+                    case_operand_->hash());
+  for (std::size_t i = 0; i < condition_operands_.size(); ++i) {
+    hash_code = CombineHashes(hash_code, condition_operands_[i]->hash());
+    hash_code = CombineHashes(hash_code, conditional_result_expressions_[i]->hash());
+  }
+  if (else_result_expression_ != nullptr) {
+    hash_code = CombineHashes(hash_code, else_result_expression_->hash());
+  }
+  return hash_code;
+}
+
+bool SimpleCase::equals(const ScalarPtr &other) const {
+  SimpleCasePtr expr;
+  if (!SomeSimpleCase::MatchesWithConditionalCast(other, &expr)) {
+    return false;
+  }
+  if (!case_operand_->equals(expr->case_operand_)) {
+    return false;
+  }
+  if (condition_operands_.size() != expr->condition_operands_.size()) {
+    return false;
+  }
+  for (std::size_t i = 0; i < condition_operands_.size(); ++i) {
+    if (!condition_operands_[i]->equals(expr->condition_operands_[i])
+        || !conditional_result_expressions_[i]->equals(
+                expr->conditional_result_expressions_[i])) {
+      return false;
+    }
+  }
+  if ((else_result_expression_ == nullptr
+       || expr->else_result_expression_ == nullptr)
+      && else_result_expression_ != expr->else_result_expression_) {
+    return false;
+  }
+  if (!else_result_expression_->equals(expr->else_result_expression_)) {
+    return false;
+  }
+  DCHECK(value_type_.equals(expr->value_type_));
+  return true;
+}
+
 void SimpleCase::getFieldStringItems(
     std::vector<std::string> *inline_field_names,
     std::vector<std::string> *inline_field_values,

http://git-wip-us.apache.org/repos/asf/incubator-quickstep/blob/0fad9ec0/query_optimizer/expressions/SimpleCase.hpp
----------------------------------------------------------------------
diff --git a/query_optimizer/expressions/SimpleCase.hpp b/query_optimizer/expressions/SimpleCase.hpp
index 897d87f..bf3decd 100644
--- a/query_optimizer/expressions/SimpleCase.hpp
+++ b/query_optimizer/expressions/SimpleCase.hpp
@@ -110,6 +110,8 @@ class SimpleCase : public Scalar {
   ::quickstep::Scalar* concretize(
       const std::unordered_map<ExprId, const CatalogAttribute*>& substitution_map) const override;
 
+  bool equals(const ScalarPtr &other) const override;
+
   /**
    * @brief Creates an immutable SimpleCase.
    *
@@ -136,6 +138,8 @@ class SimpleCase : public Scalar {
   }
 
  protected:
+  std::size_t computeHash() const override;
+
   void getFieldStringItems(std::vector<std::string> *inline_field_names,
                            std::vector<std::string> *inline_field_values,
                            std::vector<std::string> *non_container_child_field_names,

http://git-wip-us.apache.org/repos/asf/incubator-quickstep/blob/0fad9ec0/query_optimizer/expressions/UnaryExpression.cpp
----------------------------------------------------------------------
diff --git a/query_optimizer/expressions/UnaryExpression.cpp b/query_optimizer/expressions/UnaryExpression.cpp
index b0fff62..06a2ee1 100644
--- a/query_optimizer/expressions/UnaryExpression.cpp
+++ b/query_optimizer/expressions/UnaryExpression.cpp
@@ -31,6 +31,7 @@
 #include "query_optimizer/expressions/Scalar.hpp"
 #include "types/operations/unary_operations/UnaryOperation.hpp"
 #include "types/operations/unary_operations/UnaryOperationID.hpp"
+#include "utility/HashPair.hpp"
 
 #include "glog/logging.h"
 
@@ -56,6 +57,22 @@ ExpressionPtr UnaryExpression::copyWithNewChildren(
       operation_, operand_->concretize(substitution_map));
 }
 
+std::size_t UnaryExpression::computeHash() const {
+  return CombineHashes(
+      CombineHashes(static_cast<std::size_t>(ExpressionType::kUnaryExpression),
+                    static_cast<std::size_t>(operation_.getUnaryOperationID())),
+      operand_->hash());
+}
+
+bool UnaryExpression::equals(const ScalarPtr &other) const {
+  UnaryExpressionPtr expr;
+  if (SomeUnaryExpression::MatchesWithConditionalCast(other, &expr)) {
+    return operation_.getUnaryOperationID() == expr->operation_.getUnaryOperationID()
+           && operand_->equals(expr->operand_);
+  }
+  return false;
+}
+
 void UnaryExpression::getFieldStringItems(
     std::vector<std::string> *inline_field_names,
     std::vector<std::string> *inline_field_values,

http://git-wip-us.apache.org/repos/asf/incubator-quickstep/blob/0fad9ec0/query_optimizer/expressions/UnaryExpression.hpp
----------------------------------------------------------------------
diff --git a/query_optimizer/expressions/UnaryExpression.hpp b/query_optimizer/expressions/UnaryExpression.hpp
index c4542d0..2a9e97e 100644
--- a/query_optimizer/expressions/UnaryExpression.hpp
+++ b/query_optimizer/expressions/UnaryExpression.hpp
@@ -29,8 +29,10 @@
 #include "query_optimizer/expressions/ExprId.hpp"
 #include "query_optimizer/expressions/Expression.hpp"
 #include "query_optimizer/expressions/ExpressionType.hpp"
+#include "query_optimizer/expressions/PatternMatcher.hpp"
 #include "query_optimizer/expressions/Scalar.hpp"
 #include "types/operations/unary_operations/UnaryOperation.hpp"
+#include "utility/HashPair.hpp"
 #include "utility/Macros.hpp"
 
 #include "glog/logging.h"
@@ -85,6 +87,8 @@ class UnaryExpression : public Scalar {
   ::quickstep::Scalar* concretize(
       const std::unordered_map<ExprId, const CatalogAttribute*> &substitution_map) const override;
 
+  bool equals(const ScalarPtr &other) const override;
+
   /**
    * @brief Creates an immutable UnaryExpression.
    *
@@ -99,6 +103,8 @@ class UnaryExpression : public Scalar {
   }
 
  protected:
+  std::size_t computeHash() const override;
+
   void getFieldStringItems(
       std::vector<std::string> *inline_field_names,
       std::vector<std::string> *inline_field_values,

http://git-wip-us.apache.org/repos/asf/incubator-quickstep/blob/0fad9ec0/query_optimizer/rules/CMakeLists.txt
----------------------------------------------------------------------
diff --git a/query_optimizer/rules/CMakeLists.txt b/query_optimizer/rules/CMakeLists.txt
index 6847951..fa73612 100644
--- a/query_optimizer/rules/CMakeLists.txt
+++ b/query_optimizer/rules/CMakeLists.txt
@@ -21,6 +21,10 @@ add_subdirectory(tests)
 add_library(quickstep_queryoptimizer_rules_AttachLIPFilters AttachLIPFilters.cpp AttachLIPFilters.hpp)
 add_library(quickstep_queryoptimizer_rules_BottomUpRule ../../empty_src.cpp BottomUpRule.hpp)
 add_library(quickstep_queryoptimizer_rules_CollapseProject CollapseProject.cpp CollapseProject.hpp)
+add_library(quickstep_queryoptimizer_rules_CollapseSelection CollapseSelection.cpp CollapseSelection.hpp)
+add_library(quickstep_queryoptimizer_rules_ExtractCommonSubexpression
+            ExtractCommonSubexpression.cpp
+            ExtractCommonSubexpression.hpp)
 add_library(quickstep_queryoptimizer_rules_FuseAggregateJoin FuseAggregateJoin.cpp FuseAggregateJoin.hpp)
 add_library(quickstep_queryoptimizer_rules_GenerateJoins GenerateJoins.cpp GenerateJoins.hpp)
 add_library(quickstep_queryoptimizer_rules_InjectJoinFilters InjectJoinFilters.cpp InjectJoinFilters.hpp)
@@ -34,6 +38,9 @@ add_library(quickstep_queryoptimizer_rules_ReduceGroupByAttributes
             ReduceGroupByAttributes.cpp
             ReduceGroupByAttributes.hpp)
 add_library(quickstep_queryoptimizer_rules_ReorderColumns ReorderColumns.cpp ReorderColumns.hpp)
+add_library(quickstep_queryoptimizer_rules_ReuseAggregateExpressions
+            ReuseAggregateExpressions.cpp
+            ReuseAggregateExpressions.hpp)
 add_library(quickstep_queryoptimizer_rules_Rule ../../empty_src.cpp Rule.hpp)
 add_library(quickstep_queryoptimizer_rules_RuleHelper RuleHelper.cpp RuleHelper.hpp)
 add_library(quickstep_queryoptimizer_rules_StarSchemaHashJoinOrderOptimization
@@ -77,6 +84,31 @@ target_link_libraries(quickstep_queryoptimizer_rules_CollapseProject
                       quickstep_queryoptimizer_rules_Rule
                       quickstep_queryoptimizer_rules_RuleHelper
                       quickstep_utility_Macros)
+target_link_libraries(quickstep_queryoptimizer_rules_CollapseSelection
+                      quickstep_queryoptimizer_expressions_NamedExpression
+                      quickstep_queryoptimizer_physical_PatternMatcher
+                      quickstep_queryoptimizer_physical_Physical
+                      quickstep_queryoptimizer_physical_Selection
+                      quickstep_queryoptimizer_rules_BottomUpRule
+                      quickstep_queryoptimizer_rules_RuleHelper
+                      quickstep_utility_Macros)
+target_link_libraries(quickstep_queryoptimizer_rules_ExtractCommonSubexpression
+                      glog
+                      quickstep_queryoptimizer_OptimizerContext
+                      quickstep_queryoptimizer_expressions_Alias
+                      quickstep_queryoptimizer_expressions_CommonSubexpression
+                      quickstep_queryoptimizer_expressions_Expression
+                      quickstep_queryoptimizer_expressions_ExpressionType
+                      quickstep_queryoptimizer_expressions_NamedExpression
+                      quickstep_queryoptimizer_expressions_PatternMatcher
+                      quickstep_queryoptimizer_expressions_Scalar
+                      quickstep_queryoptimizer_physical_Aggregate
+                      quickstep_queryoptimizer_physical_Physical
+                      quickstep_queryoptimizer_physical_PhysicalType
+                      quickstep_queryoptimizer_physical_Selection
+                      quickstep_queryoptimizer_rules_Rule
+                      quickstep_utility_HashError
+                      quickstep_utility_Macros)
 target_link_libraries(quickstep_queryoptimizer_rules_FuseAggregateJoin
                       quickstep_queryoptimizer_costmodel_StarSchemaSimpleCostModel
                       quickstep_queryoptimizer_expressions_AggregateFunction
@@ -200,6 +232,34 @@ target_link_libraries(quickstep_queryoptimizer_rules_ReorderColumns
                       quickstep_queryoptimizer_physical_TableReference
                       quickstep_queryoptimizer_rules_Rule
                       quickstep_utility_Macros)
+target_link_libraries(quickstep_queryoptimizer_rules_ReuseAggregateExpressions
+                      glog
+                      quickstep_expressions_aggregation_AggregateFunction
+                      quickstep_expressions_aggregation_AggregateFunctionFactory
+                      quickstep_expressions_aggregation_AggregationID
+                      quickstep_queryoptimizer_OptimizerContext
+                      quickstep_queryoptimizer_costmodel_StarSchemaSimpleCostModel
+                      quickstep_queryoptimizer_expressions_AggregateFunction
+                      quickstep_queryoptimizer_expressions_Alias
+                      quickstep_queryoptimizer_expressions_AttributeReference
+                      quickstep_queryoptimizer_expressions_BinaryExpression
+                      quickstep_queryoptimizer_expressions_ExpressionType
+                      quickstep_queryoptimizer_expressions_ExpressionUtil
+                      quickstep_queryoptimizer_expressions_NamedExpression
+                      quickstep_queryoptimizer_expressions_Scalar
+                      quickstep_queryoptimizer_physical_Aggregate
+                      quickstep_queryoptimizer_physical_PatternMatcher
+                      quickstep_queryoptimizer_physical_Physical
+                      quickstep_queryoptimizer_physical_PhysicalType
+                      quickstep_queryoptimizer_physical_Selection
+                      quickstep_queryoptimizer_physical_TopLevelPlan
+                      quickstep_queryoptimizer_rules_BottomUpRule
+                      quickstep_types_operations_binaryoperations_BinaryOperation
+                      quickstep_types_operations_binaryoperations_BinaryOperationFactory
+                      quickstep_types_operations_binaryoperations_BinaryOperationID
+                      quickstep_utility_EqualsAnyConstant
+                      quickstep_utility_HashError
+                      quickstep_utility_Macros)
 target_link_libraries(quickstep_queryoptimizer_rules_Rule
                       glog
                       quickstep_utility_Macros)
@@ -311,6 +371,8 @@ target_link_libraries(quickstep_queryoptimizer_rules
                       quickstep_queryoptimizer_rules_AttachLIPFilters
                       quickstep_queryoptimizer_rules_BottomUpRule
                       quickstep_queryoptimizer_rules_CollapseProject
+                      quickstep_queryoptimizer_rules_CollapseSelection
+                      quickstep_queryoptimizer_rules_ExtractCommonSubexpression
                       quickstep_queryoptimizer_rules_FuseAggregateJoin
                       quickstep_queryoptimizer_rules_GenerateJoins
                       quickstep_queryoptimizer_rules_InjectJoinFilters
@@ -320,6 +382,7 @@ target_link_libraries(quickstep_queryoptimizer_rules
                       quickstep_queryoptimizer_rules_PushDownSemiAntiJoin
                       quickstep_queryoptimizer_rules_ReduceGroupByAttributes
                       quickstep_queryoptimizer_rules_ReorderColumns
+                      quickstep_queryoptimizer_rules_ReuseAggregateExpressions
                       quickstep_queryoptimizer_rules_Rule
                       quickstep_queryoptimizer_rules_RuleHelper
                       quickstep_queryoptimizer_rules_StarSchemaHashJoinOrderOptimization

http://git-wip-us.apache.org/repos/asf/incubator-quickstep/blob/0fad9ec0/query_optimizer/rules/CollapseSelection.cpp
----------------------------------------------------------------------
diff --git a/query_optimizer/rules/CollapseSelection.cpp b/query_optimizer/rules/CollapseSelection.cpp
new file mode 100644
index 0000000..a03faa5
--- /dev/null
+++ b/query_optimizer/rules/CollapseSelection.cpp
@@ -0,0 +1,57 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ **/
+
+#include "query_optimizer/rules/CollapseSelection.hpp"
+
+#include <vector>
+
+#include "query_optimizer/expressions/NamedExpression.hpp"
+#include "query_optimizer/physical/PatternMatcher.hpp"
+#include "query_optimizer/physical/Physical.hpp"
+#include "query_optimizer/physical/Selection.hpp"
+#include "query_optimizer/rules/RuleHelper.hpp"
+
+namespace quickstep {
+namespace optimizer {
+
+namespace E = ::quickstep::optimizer::expressions;
+namespace P = ::quickstep::optimizer::physical;
+
+P::PhysicalPtr CollapseSelection::applyToNode(const P::PhysicalPtr &input) {
+  P::SelectionPtr selection;
+  P::SelectionPtr child_selection;
+
+  if (P::SomeSelection::MatchesWithConditionalCast(input, &selection) &&
+      P::SomeSelection::MatchesWithConditionalCast(selection->input(), &child_selection) &&
+      child_selection->filter_predicate() == nullptr) {
+    std::vector<E::NamedExpressionPtr> project_expressions =
+        selection->project_expressions();
+    PullUpProjectExpressions(child_selection->project_expressions(),
+                             {} /* non_project_expression_lists */,
+                             {&project_expressions} /* project_expression_lists */);
+    return P::Selection::Create(child_selection->input(),
+                                project_expressions,
+                                selection->filter_predicate());
+  }
+
+  return input;
+}
+
+}  // namespace optimizer
+}  // namespace quickstep

http://git-wip-us.apache.org/repos/asf/incubator-quickstep/blob/0fad9ec0/query_optimizer/rules/CollapseSelection.hpp
----------------------------------------------------------------------
diff --git a/query_optimizer/rules/CollapseSelection.hpp b/query_optimizer/rules/CollapseSelection.hpp
new file mode 100644
index 0000000..2417574
--- /dev/null
+++ b/query_optimizer/rules/CollapseSelection.hpp
@@ -0,0 +1,59 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ **/
+
+#ifndef QUICKSTEP_QUERY_OPTIMIZER_RULES_COLLAPSE_SELECTION_HPP_
+#define QUICKSTEP_QUERY_OPTIMIZER_RULES_COLLAPSE_SELECTION_HPP_
+
+#include <string>
+
+#include "query_optimizer/physical/Physical.hpp"
+#include "query_optimizer/rules/BottomUpRule.hpp"
+#include "utility/Macros.hpp"
+
+namespace quickstep {
+namespace optimizer {
+
+/** \addtogroup OptimizerRules
+ *  @{
+ */
+
+/**
+ * @brief Merges nested Selections into one single Selection.
+ */
+class CollapseSelection : public BottomUpRule<physical::Physical> {
+ public:
+  CollapseSelection() {}
+
+  std::string getName() const override {
+    return "CollapseSelection";
+  }
+
+ protected:
+  physical::PhysicalPtr applyToNode(const physical::PhysicalPtr &input) override;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(CollapseSelection);
+};
+
+/** @} */
+
+}  // namespace optimizer
+}  // namespace quickstep
+
+#endif  // QUICKSTEP_QUERY_OPTIMIZER_RULES_COLLAPSE_SELECTION_HPP_