Simplify expression scan planning

src/include/common/constants.h

@@ -32,6 +32,7 @@ struct InternalKeyword {
     static constexpr char RELS[] = "_RELS";
     static constexpr char TAG[] = "_TAG";
     static constexpr char STAR[] = "*";
+    static constexpr char PLACE_HOLDER[] = "_PLACE_HOLDER";
 };
 
 enum PageSizeClass : uint8_t {

src/include/planner/logical_plan/logical_operator/base_logical_operator.h

@@ -22,7 +22,7 @@ enum class LogicalOperatorType : uint8_t {
     DISTINCT,
     DROP_PROPERTY,
     DROP_TABLE,
-    EXPRESSIONS_SCAN,
+    EXPRESSION_SCAN,
     EXPLAIN,
     EXTEND,
     FILTER,

src/include/planner/logical_plan/logical_operator/logical_expressions_scan.h

@@ -6,29 +6,26 @@
 namespace kuzu {
 namespace planner {
 
-class LogicalExpressionsScan : public LogicalOperator {
+// TODO(Xiyang): change to DummyScan once we rewrite our index scan.
+class LogicalExpressionScan : public LogicalOperator {
 public:
-    // LogicalExpressionsScan does not take input from child operator. So its input expressions must
-    // be evaluated statically i.e. must be value.
-    explicit LogicalExpressionsScan(binder::expression_vector expressions)
-        : LogicalOperator{LogicalOperatorType::EXPRESSIONS_SCAN}, expressions{
-                                                                      std::move(expressions)} {}
+    explicit LogicalExpressionScan(std::shared_ptr<binder::Expression> expression)
+        : LogicalOperator{LogicalOperatorType::EXPRESSION_SCAN}, expression{std::move(expression)} {
+    }
 
     void computeFactorizedSchema() override;
     void computeFlatSchema() override;
 
-    inline std::string getExpressionsForPrinting() const override {
-        return binder::ExpressionUtil::toString(expressions);
-    }
+    inline std::string getExpressionsForPrinting() const override { return std::string(); }
 
-    inline binder::expression_vector getExpressions() const { return expressions; }
+    inline std::shared_ptr<binder::Expression> getExpression() const { return expression; }
 
     inline std::unique_ptr<LogicalOperator> copy() override {
-        return make_unique<LogicalExpressionsScan>(expressions);
+        return make_unique<LogicalExpressionScan>(expression);
     }
 
 private:
-    binder::expression_vector expressions;
+    std::shared_ptr<binder::Expression> expression;
 };
 
 } // namespace planner

src/include/planner/query_planner.h

@@ -77,7 +77,7 @@ class QueryPlanner {
 
     void appendAccumulate(common::AccumulateType accumulateType, LogicalPlan& plan);
 
-    void appendExpressionsScan(const expression_vector& expressions, LogicalPlan& plan);
+    void appendDummyScan(LogicalPlan& plan);
 
     void appendDistinct(const expression_vector& expressionsToDistinct, LogicalPlan& plan);
 

src/include/processor/mapper/plan_mapper.h

@@ -55,7 +55,7 @@ class PlanMapper {
     std::unique_ptr<PhysicalOperator> mapOrderBy(planner::LogicalOperator* logicalOperator);
     std::unique_ptr<PhysicalOperator> mapUnionAll(planner::LogicalOperator* logicalOperator);
     std::unique_ptr<PhysicalOperator> mapAccumulate(planner::LogicalOperator* logicalOperator);
-    std::unique_ptr<PhysicalOperator> mapExpressionsScan(planner::LogicalOperator* logicalOperator);
+    std::unique_ptr<PhysicalOperator> mapExpressionScan(planner::LogicalOperator* logicalOperator);
     std::unique_ptr<PhysicalOperator> mapCreateNode(planner::LogicalOperator* logicalOperator);
     std::unique_ptr<PhysicalOperator> mapCreateRel(planner::LogicalOperator* logicalOperator);
     std::unique_ptr<PhysicalOperator> mapSetNodeProperty(planner::LogicalOperator* logicalOperator);

src/optimizer/filter_push_down_optimizer.cpp

@@ -115,7 +115,7 @@ std::shared_ptr<planner::LogicalOperator> FilterPushDownOptimizer::visitScanNode
         auto rhs = primaryKeyEqualityComparison->getChild(1);
         if (rhs->expressionType == common::ExpressionType::LITERAL) {
             // Rewrite to index scan
-            auto expressionsScan = make_shared<LogicalExpressionsScan>(expression_vector{rhs});
+            auto expressionsScan = make_shared<LogicalExpressionScan>(rhs);
             expressionsScan->computeFlatSchema();
             auto indexScan =
                 std::make_shared<LogicalIndexScanNode>(node, rhs, std::move(expressionsScan));

src/planner/operator/base_logical_operator.cpp

@@ -55,8 +55,8 @@ std::string LogicalOperatorUtils::logicalOperatorTypeToString(LogicalOperatorTyp
     case LogicalOperatorType::DROP_TABLE: {
         return "DROP_TABLE";
     }
-    case LogicalOperatorType::EXPRESSIONS_SCAN: {
-        return "EXPRESSIONS_SCAN";
+    case LogicalOperatorType::EXPRESSION_SCAN: {
+        return "EXPRESSION_SCAN";
     }
     case LogicalOperatorType::EXTEND: {
         return "EXTEND";

src/planner/operator/logical_expressions_scan.cpp

@@ -3,29 +3,17 @@
 namespace kuzu {
 namespace planner {
 
-void LogicalExpressionsScan::computeFactorizedSchema() {
+void LogicalExpressionScan::computeFactorizedSchema() {
     createEmptySchema();
     auto groupPos = schema->createGroup();
     schema->setGroupAsSingleState(groupPos); // Mark group holding constant as single state.
-    for (auto& expression : expressions) {
-        // No need to insert repeated constant.
-        if (schema->isExpressionInScope(*expression)) {
-            continue;
-        }
-        schema->insertToGroupAndScope(expression, groupPos);
-    }
+    schema->insertToGroupAndScope(expression, groupPos);
 }
 
-void LogicalExpressionsScan::computeFlatSchema() {
+void LogicalExpressionScan::computeFlatSchema() {
     createEmptySchema();
     schema->createGroup();
-    for (auto& expression : expressions) {
-        // No need to insert repeated constant.
-        if (schema->isExpressionInScope(*expression)) {
-            continue;
-        }
-        schema->insertToGroupAndScope(expression, 0);
-    }
+    schema->insertToGroupAndScope(expression, 0);
 }
 
 } // namespace planner

src/planner/plan/plan_update.cpp

@@ -41,11 +41,7 @@ void QueryPlanner::planCreateClause(
     binder::BoundUpdatingClause& updatingClause, LogicalPlan& plan) {
     auto& createClause = (BoundCreateClause&)updatingClause;
     if (plan.isEmpty()) { // E.g. CREATE (a:Person {age:20})
-        expression_vector expressions;
-        for (auto& setItem : createClause.getAllSetItems()) {
-            expressions.push_back(setItem.second);
-        }
-        appendExpressionsScan(expressions, plan);
+        appendDummyScan(plan);
     } else {
         appendAccumulate(common::AccumulateType::REGULAR, plan);
     }

src/planner/projection_planner.cpp

@@ -27,17 +27,7 @@ void ProjectionPlanner::planProjectionBody(const BoundProjectionBody& projection
 void ProjectionPlanner::planProjectionBody(
     const BoundProjectionBody& projectionBody, LogicalPlan& plan) {
     if (plan.isEmpty()) { // e.g. RETURN 1, COUNT(2)
-        expression_vector expressionsToScan;
-        for (auto& expression : projectionBody.getProjectionExpressions()) {
-            if (expression->expressionType == AGGREGATE_FUNCTION) { // aggregate on const
-                if (expression->getNumChildren() != 0) {            // skip count(*)
-                    expressionsToScan.push_back(expression->getChild(0));
-                }
-            } else {
-                expressionsToScan.push_back(expression);
-            }
-        }
-        queryPlanner->appendExpressionsScan(expressionsToScan, plan);
+        queryPlanner->appendDummyScan(plan);
     }
     // NOTE: As a temporary solution, we rewrite variables in WITH clause as all properties in scope
     // during planning stage. The purpose is to avoid reading unnecessary properties for WITH.

src/planner/query_planner.cpp

@@ -1,6 +1,7 @@
 #include "planner/query_planner.h"
 
 #include "binder/expression/expression_visitor.h"
+#include "binder/expression/literal_expression.h"
 #include "binder/query/bound_regular_query.h"
 #include "binder/visitor/property_collector.h"
 #include "common/join_type.h"
@@ -137,8 +138,7 @@ void QueryPlanner::planUnwindClause(
     auto boundUnwindClause = reinterpret_cast<BoundUnwindClause*>(boundReadingClause);
     for (auto& plan : plans) {
         if (plan->isEmpty()) { // UNWIND [1, 2, 3, 4] AS x RETURN x
-            auto expressions = expression_vector{boundUnwindClause->getExpression()};
-            appendExpressionsScan(expressions, *plan);
+            appendDummyScan(*plan);
         }
         appendUnwind(*boundUnwindClause, *plan);
     }
@@ -291,9 +291,13 @@ void QueryPlanner::planSubqueryIfNecessary(
     }
 }
 
-void QueryPlanner::appendExpressionsScan(const expression_vector& expressions, LogicalPlan& plan) {
+void QueryPlanner::appendDummyScan(LogicalPlan& plan) {
     assert(plan.isEmpty());
-    auto expressionsScan = make_shared<LogicalExpressionsScan>(expressions);
+    auto logicalType = common::LogicalType(common::LogicalTypeID::STRING);
+    auto nullValue = common::Value::createNullValue(logicalType);
+    auto literalExpression = std::make_shared<binder::LiteralExpression>(
+        nullValue.copy(), common::InternalKeyword::PLACE_HOLDER);
+    auto expressionsScan = make_shared<LogicalExpressionScan>(std::move(literalExpression));
     expressionsScan->computeFactorizedSchema();
     plan.setLastOperator(std::move(expressionsScan));
 }

src/processor/mapper/map_expressions_scan.cpp

@@ -8,29 +8,28 @@ using namespace kuzu::planner;
 namespace kuzu {
 namespace processor {
 
-std::unique_ptr<PhysicalOperator> PlanMapper::mapExpressionsScan(LogicalOperator* logicalOperator) {
-    auto& logicalExpressionsScan = (LogicalExpressionsScan&)*logicalOperator;
-    auto outSchema = logicalExpressionsScan.getSchema();
+std::unique_ptr<PhysicalOperator> PlanMapper::mapExpressionScan(LogicalOperator* logicalOperator) {
+    auto logicalExpressionScan = (LogicalExpressionScan*)logicalOperator;
+    auto outSchema = logicalExpressionScan->getSchema();
     auto inSchema = std::make_unique<Schema>();
-    auto expressions = logicalExpressionsScan.getExpressions();
+    auto expression = logicalExpressionScan->getExpression();
     auto tableSchema = std::make_unique<FactorizedTableSchema>();
     // TODO(Ziyi): remove vectors when we have done the refactor of dataChunk.
     std::vector<std::shared_ptr<ValueVector>> vectors;
     std::vector<ValueVector*> vectorsToAppend;
-    for (auto& expression : expressions) {
-        tableSchema->appendColumn(
-            std::make_unique<ColumnSchema>(false, 0 /* all expressions are in the same datachunk */,
-                LogicalTypeUtils::getRowLayoutSize(expression->dataType)));
-        auto expressionEvaluator = expressionMapper.mapExpression(expression, *inSchema);
-        // expression can be evaluated statically and does not require an actual resultset to init
-        expressionEvaluator->init(ResultSet(0) /* dummy resultset */, memoryManager);
-        expressionEvaluator->evaluate();
-        vectors.push_back(expressionEvaluator->resultVector);
-        vectorsToAppend.push_back(expressionEvaluator->resultVector.get());
-    }
+    tableSchema->appendColumn(
+        std::make_unique<ColumnSchema>(false, 0 /* all expressions are in the same datachunk */,
+            LogicalTypeUtils::getRowLayoutSize(expression->dataType)));
+    auto expressionEvaluator = expressionMapper.mapExpression(expression, *inSchema);
+    // expression can be evaluated statically and does not require an actual resultset to init
+    expressionEvaluator->init(ResultSet(0) /* dummy resultset */, memoryManager);
+    expressionEvaluator->evaluate();
+    vectors.push_back(expressionEvaluator->resultVector);
+    vectorsToAppend.push_back(expressionEvaluator->resultVector.get());
     auto table = std::make_shared<FactorizedTable>(memoryManager, std::move(tableSchema));
     table->append(vectorsToAppend);
-    return createFactorizedTableScan(expressions, outSchema, table, nullptr);
+    return createFactorizedTableScan(
+        binder::expression_vector{expression}, outSchema, table, nullptr);
 }
 
 } // namespace processor

src/processor/mapper/plan_mapper.cpp

@@ -104,8 +104,8 @@ std::unique_ptr<PhysicalOperator> PlanMapper::mapOperator(LogicalOperator* logic
     case LogicalOperatorType::ACCUMULATE: {
         physicalOperator = mapAccumulate(logicalOperator);
     } break;
-    case LogicalOperatorType::EXPRESSIONS_SCAN: {
-        physicalOperator = mapExpressionsScan(logicalOperator);
+    case LogicalOperatorType::EXPRESSION_SCAN: {
+        physicalOperator = mapExpressionScan(logicalOperator);
     } break;
     case LogicalOperatorType::CREATE_NODE: {
         physicalOperator = mapCreateNode(logicalOperator);