allow optional match as first match

src/binder/bind/bind_query.cpp

@@ -32,7 +32,6 @@ std::unique_ptr<BoundRegularQuery> Binder::bindQuery(const RegularQuery& regular
 }
 
 std::unique_ptr<BoundSingleQuery> Binder::bindSingleQuery(const SingleQuery& singleQuery) {
-    validateFirstMatchIsNotOptional(singleQuery);
     auto boundSingleQuery = std::make_unique<BoundSingleQuery>();
     for (auto i = 0u; i < singleQuery.getNumQueryParts(); ++i) {
         boundSingleQuery->addQueryPart(bindQueryPart(*singleQuery.getQueryPart(i)));

src/binder/bind/bind_reading_clause.cpp

@@ -31,8 +31,8 @@ std::unique_ptr<BoundReadingClause> Binder::bindMatchClause(const ReadingClause&
     auto& matchClause = reinterpret_cast<const MatchClause&>(readingClause);
     auto [queryGraphCollection, propertyCollection] =
         bindGraphPattern(matchClause.getPatternElements());
-    auto boundMatchClause =
-        make_unique<BoundMatchClause>(std::move(queryGraphCollection), matchClause.getIsOptional());
+    auto boundMatchClause = make_unique<BoundMatchClause>(
+        std::move(queryGraphCollection), matchClause.getMatchClauseType());
     std::shared_ptr<Expression> whereExpression;
     if (matchClause.hasWhereClause()) {
         whereExpression = bindWhereExpression(*matchClause.getWhereClause());

src/binder/binder.cpp

@@ -85,12 +85,6 @@ std::shared_ptr<Expression> Binder::createVariable(
     return expression;
 }
 
-void Binder::validateFirstMatchIsNotOptional(const SingleQuery& singleQuery) {
-    if (singleQuery.isFirstReadingClauseOptionalMatch()) {
-        throw BinderException("First match clause cannot be optional match.");
-    }
-}
-
 void Binder::validateProjectionColumnNamesAreUnique(const expression_vector& expressions) {
     auto existColumnNames = std::unordered_set<std::string>();
     for (auto& expression : expressions) {

src/include/binder/binder.h

@@ -202,11 +202,6 @@ class Binder {
     std::vector<common::table_id_t> bindRelTableIDs(const std::vector<std::string>& tableNames);
 
     /*** validations ***/
-    // E.g. Optional MATCH (a) RETURN a.age
-    // Although this is doable in Neo4j, I don't think the semantic make a lot of sense because
-    // there is nothing to left join on.
-    static void validateFirstMatchIsNotOptional(const parser::SingleQuery& singleQuery);
-
     // E.g. ... RETURN a, b AS a
     static void validateProjectionColumnNamesAreUnique(const expression_vector& expressions);
 

src/include/binder/query/reading_clause/bound_match_clause.h

@@ -7,21 +7,17 @@
 namespace kuzu {
 namespace binder {
 
-/**
- * BoundMatchClause may not have whereExpression
- */
 class BoundMatchClause : public BoundReadingClause {
-
 public:
-    explicit BoundMatchClause(
-        std::unique_ptr<QueryGraphCollection> queryGraphCollection, bool isOptional)
+    explicit BoundMatchClause(std::unique_ptr<QueryGraphCollection> queryGraphCollection,
+        common::MatchClauseType matchClauseType)
         : BoundReadingClause{common::ClauseType::MATCH},
-          queryGraphCollection{std::move(queryGraphCollection)}, isOptional{isOptional} {}
+          queryGraphCollection{std::move(queryGraphCollection)}, matchClauseType{matchClauseType} {}
 
     BoundMatchClause(const BoundMatchClause& other)
         : BoundReadingClause(common::ClauseType::MATCH),
           queryGraphCollection{other.queryGraphCollection->copy()},
-          whereExpression(other.whereExpression), isOptional{other.isOptional} {}
+          whereExpression(other.whereExpression), matchClauseType{other.matchClauseType} {}
 
     ~BoundMatchClause() override = default;
 
@@ -38,7 +34,7 @@ class BoundMatchClause : public BoundReadingClause {
         return hasWhereExpression() ? whereExpression->splitOnAND() : expression_vector{};
     }
 
-    inline bool getIsOptional() const { return isOptional; }
+    inline common::MatchClauseType getMatchClauseType() const { return matchClauseType; }
 
     inline std::unique_ptr<BoundReadingClause> copy() override {
         return std::make_unique<BoundMatchClause>(*this);
@@ -47,7 +43,7 @@ class BoundMatchClause : public BoundReadingClause {
 private:
     std::unique_ptr<QueryGraphCollection> queryGraphCollection;
     std::shared_ptr<Expression> whereExpression;
-    bool isOptional;
+    common::MatchClauseType matchClauseType;
 };
 
 } // namespace binder

src/include/common/clause_type.h

@@ -17,5 +17,10 @@ enum class ClauseType : uint8_t {
     InQueryCall = 5,
 };
 
+enum class MatchClauseType : uint8_t {
+    MATCH = 0,
+    OPTIONAL_MATCH = 1,
+};
+
 } // namespace common
 } // namespace kuzu

src/include/common/join_type.h

@@ -11,5 +11,11 @@ enum class JoinType : uint8_t {
     MARK = 2,
 };
 
+enum class AccumulateType : uint8_t {
+    REGULAR = 0,
+    OPTIONAL = 1,
+    EXISTS = 2,
+};
+
 } // namespace common
 } // namespace kuzu

src/include/common/vector/value_vector.h

@@ -19,6 +19,7 @@ class ValueVector {
     friend class StructVector;
     friend class StringVector;
     friend class ArrowColumnVector;
+    friend class ValueVectorUtils;
 
 public:
     explicit ValueVector(LogicalType dataType, storage::MemoryManager* memoryManager = nullptr);
@@ -34,8 +35,7 @@ class ValueVector {
     inline void setAllNull() { nullMask->setAllNull(); }
     inline void setAllNonNull() { nullMask->setAllNonNull(); }
     inline void setMayContainNulls() { nullMask->setMayContainNulls(); }
-    // Note that if this function returns true, there are no null. However, if it returns false, it
-    // doesn't mean there are nulls, i.e., there may or may not be nulls.
+    // On return true, there are no null. On return false, there may or may not be nulls.
     inline bool hasNoNullsGuarantee() const { return nullMask->hasNoNullsGuarantee(); }
     inline void setRangeNonNull(uint32_t startPos, uint32_t len) {
         for (auto i = 0u; i < len; ++i) {
@@ -45,6 +45,10 @@ class ValueVector {
     inline uint64_t* getNullMaskData() { return nullMask->getData(); }
     inline void setNull(uint32_t pos, bool isNull) { nullMask->setNull(pos, isNull); }
     inline uint8_t isNull(uint32_t pos) const { return nullMask->isNull(pos); }
+    inline void setAsSingleNullEntry() {
+        state->selVector->selectedSize = 1;
+        setNull(state->selVector->selectedPositions[0], true);
+    }
 
     inline uint32_t getNumBytesPerValue() const { return numBytesPerValue; }
 

src/include/parser/query/reading_clause/match_clause.h

@@ -9,10 +9,10 @@ namespace parser {
 
 class MatchClause : public ReadingClause {
 public:
-    explicit MatchClause(
-        std::vector<std::unique_ptr<PatternElement>> patternElements, bool isOptional = false)
+    explicit MatchClause(std::vector<std::unique_ptr<PatternElement>> patternElements,
+        common::MatchClauseType matchClauseType)
         : ReadingClause{common::ClauseType::MATCH}, patternElements{std::move(patternElements)},
-          isOptional{isOptional} {}
+          matchClauseType{matchClauseType} {}
     ~MatchClause() override = default;
 
     inline const std::vector<std::unique_ptr<PatternElement>>& getPatternElements() const {
@@ -26,12 +26,12 @@ class MatchClause : public ReadingClause {
     inline bool hasWhereClause() const { return whereClause != nullptr; }
     inline ParsedExpression* getWhereClause() const { return whereClause.get(); }
 
-    inline bool getIsOptional() const { return isOptional; }
+    inline common::MatchClauseType getMatchClauseType() const { return matchClauseType; }
 
 private:
     std::vector<std::unique_ptr<PatternElement>> patternElements;
     std::unique_ptr<ParsedExpression> whereClause;
-    bool isOptional;
+    common::MatchClauseType matchClauseType;
 };
 
 } // namespace parser

src/include/parser/query/single_query.h

@@ -37,8 +37,6 @@ class SingleQuery {
     inline bool hasReturnClause() const { return returnClause != nullptr; }
     inline ReturnClause* getReturnClause() const { return returnClause.get(); }
 
-    bool isFirstReadingClauseOptionalMatch() const;
-
 private:
     std::vector<std::unique_ptr<QueryPart>> queryParts;
     std::vector<std::unique_ptr<ReadingClause>> readingClauses;

src/include/planner/join_order_enumerator.h

@@ -30,9 +30,9 @@ class JoinOrderEnumerator {
 
     inline void resetState() { context->resetState(); }
 
-    std::unique_ptr<JoinOrderEnumeratorContext> enterSubquery(
+    std::unique_ptr<JoinOrderEnumeratorContext> enterContext(
         binder::expression_vector nodeIDsToScanFromInnerAndOuter);
-    void exitSubquery(std::unique_ptr<JoinOrderEnumeratorContext> prevContext);
+    void exitContext(std::unique_ptr<JoinOrderEnumeratorContext> prevContext);
 
     inline void planMarkJoin(const binder::expression_vector& joinNodeIDs,
         std::shared_ptr<Expression> mark, LogicalPlan& probePlan, LogicalPlan& buildPlan) {

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

@@ -1,27 +1,33 @@
 #pragma once
 
 #include "base_logical_operator.h"
+#include "common/join_type.h"
 
 namespace kuzu {
 namespace planner {
 
 class LogicalAccumulate : public LogicalOperator {
 public:
-    LogicalAccumulate(std::shared_ptr<LogicalOperator> child)
-        : LogicalOperator{LogicalOperatorType::ACCUMULATE, std::move(child)} {}
+    LogicalAccumulate(common::AccumulateType accumulateType, std::shared_ptr<LogicalOperator> child)
+        : LogicalOperator{LogicalOperatorType::ACCUMULATE, std::move(child)}, accumulateType{
+                                                                                  accumulateType} {}
 
-    void computeFactorizedSchema() override;
-    void computeFlatSchema() override;
+    void computeFactorizedSchema() final;
+    void computeFlatSchema() final;
 
-    inline std::string getExpressionsForPrinting() const override { return std::string{}; }
+    inline std::string getExpressionsForPrinting() const final { return std::string{}; }
 
+    inline common::AccumulateType getAccumulateType() const { return accumulateType; }
     inline binder::expression_vector getExpressions() const {
         return children[0]->getSchema()->getExpressionsInScope();
     }
 
-    inline std::unique_ptr<LogicalOperator> copy() override {
-        return make_unique<LogicalAccumulate>(children[0]->copy());
+    inline std::unique_ptr<LogicalOperator> copy() final {
+        return make_unique<LogicalAccumulate>(accumulateType, children[0]->copy());
     }
+
+private:
+    common::AccumulateType accumulateType;
 };
 
 } // namespace planner

src/include/planner/query_planner.h

@@ -48,15 +48,20 @@ class QueryPlanner {
     void planInQueryCall(
         BoundReadingClause* boundReadingClause, std::vector<std::unique_ptr<LogicalPlan>>& plans);
 
-    // CTE & subquery planning
     void planOptionalMatch(const QueryGraphCollection& queryGraphCollection,
-        expression_vector& predicates, LogicalPlan& outerPlan);
+        const expression_vector& predicates, LogicalPlan& leftPlan);
     void planRegularMatch(const QueryGraphCollection& queryGraphCollection,
-        expression_vector& predicates, LogicalPlan& prevPlan);
-    void planExistsSubquery(std::shared_ptr<Expression>& subquery, LogicalPlan& outerPlan);
+        const expression_vector& predicates, LogicalPlan& leftPlan);
+    void planExistsSubquery(std::shared_ptr<Expression> subquery, LogicalPlan& outerPlan);
     void planSubqueryIfNecessary(const std::shared_ptr<Expression>& expression, LogicalPlan& plan);
 
-    void appendAccumulate(LogicalPlan& plan);
+    std::unique_ptr<LogicalPlan> planJoins(
+        const QueryGraphCollection& queryGraphCollection, const expression_vector& predicates);
+    std::unique_ptr<LogicalPlan> planJoinsInNewContext(
+        const expression_vector& expressionsToExcludeScan,
+        const QueryGraphCollection& queryGraphCollection, const expression_vector& predicates);
+
+    void appendAccumulate(common::AccumulateType accumulateType, LogicalPlan& plan);
 
     void appendExpressionsScan(const expression_vector& expressions, LogicalPlan& plan);
 

src/include/processor/mapper/plan_mapper.h

@@ -77,7 +77,7 @@ class PlanMapper {
     std::unique_ptr<PhysicalOperator> mapExplain(planner::LogicalOperator* logicalOperator);
     std::unique_ptr<PhysicalOperator> mapCreateMacro(planner::LogicalOperator* logicalOperator);
 
-    std::unique_ptr<ResultCollector> createResultCollector(
+    std::unique_ptr<ResultCollector> createResultCollector(common::AccumulateType accumulateType,
         const binder::expression_vector& expressions, planner::Schema* schema,
         std::unique_ptr<PhysicalOperator> prevOperator);
     std::unique_ptr<PhysicalOperator> createFactorizedTableScan(

src/include/processor/operator/hash_join/hash_join_probe.h

@@ -94,8 +94,6 @@ class HashJoinProbe : public PhysicalOperator, public SelVectorOverWriter {
     uint64_t getMarkJoinResult();
     uint64_t getJoinResult();
 
-    void setVectorsToNull();
-
 private:
     std::shared_ptr<HashJoinSharedState> sharedState;
     common::JoinType joinType;

src/include/processor/operator/result_collector.h

@@ -1,5 +1,6 @@
 #pragma once
 
+#include "common/join_type.h"
 #include "processor/operator/sink.h"
 #include "processor/result/factorized_table.h"
 
@@ -24,14 +25,17 @@ class ResultCollectorSharedState {
 };
 
 struct ResultCollectorInfo {
+    common::AccumulateType accumulateType;
     std::unique_ptr<FactorizedTableSchema> tableSchema;
     std::vector<DataPos> payloadPositions;
 
-    ResultCollectorInfo(
+    ResultCollectorInfo(common::AccumulateType accumulateType,
         std::unique_ptr<FactorizedTableSchema> tableSchema, std::vector<DataPos> payloadPositions)
-        : tableSchema{std::move(tableSchema)}, payloadPositions{std::move(payloadPositions)} {}
+        : accumulateType{accumulateType}, tableSchema{std::move(tableSchema)},
+          payloadPositions{std::move(payloadPositions)} {}
     ResultCollectorInfo(const ResultCollectorInfo& other)
-        : tableSchema{other.tableSchema->copy()}, payloadPositions{other.payloadPositions} {}
+        : accumulateType{other.accumulateType}, tableSchema{other.tableSchema->copy()},
+          payloadPositions{other.payloadPositions} {}
 
     inline std::unique_ptr<ResultCollectorInfo> copy() const {
         return std::make_unique<ResultCollectorInfo>(*this);
@@ -48,19 +52,22 @@ class ResultCollector : public Sink {
               std::move(child), id, paramsString},
           info{std::move(info)}, sharedState{std::move(sharedState)} {}
 
-    void initLocalStateInternal(ResultSet* resultSet, ExecutionContext* context) override;
+    void executeInternal(ExecutionContext* context) final;
 
-    void executeInternal(ExecutionContext* context) override;
+    void finalize(ExecutionContext* context) final;
 
     inline std::shared_ptr<FactorizedTable> getResultFactorizedTable() {
         return sharedState->getTable();
     }
 
-    std::unique_ptr<PhysicalOperator> clone() override {
+    std::unique_ptr<PhysicalOperator> clone() final {
         return make_unique<ResultCollector>(resultSetDescriptor->copy(), info->copy(), sharedState,
             children[0]->clone(), id, paramsString);
     }
 
+private:
+    void initLocalStateInternal(ResultSet* resultSet, ExecutionContext* context) final;
+
 private:
     std::unique_ptr<ResultCollectorInfo> info;
     std::shared_ptr<ResultCollectorSharedState> sharedState;

src/optimizer/acc_hash_join_optimizer.cpp

@@ -244,7 +244,8 @@ std::shared_ptr<planner::LogicalOperator> HashJoinSIPOptimizer::appendPathSemiMa
 
 std::shared_ptr<planner::LogicalOperator> HashJoinSIPOptimizer::appendAccumulate(
     std::shared_ptr<planner::LogicalOperator> child) {
-    auto accumulate = std::make_shared<LogicalAccumulate>(std::move(child));
+    auto accumulate =
+        std::make_shared<LogicalAccumulate>(common::AccumulateType::REGULAR, std::move(child));
     accumulate->computeFlatSchema();
     return accumulate;
 }

src/optimizer/optimizer.cpp

@@ -12,6 +12,7 @@ namespace kuzu {
 namespace optimizer {
 
 void Optimizer::optimize(planner::LogicalPlan* plan) {
+
     // Factorization structure should be removed before further optimization can be applied.
     auto removeFactorizationRewriter = RemoveFactorizationRewriter();
     removeFactorizationRewriter.rewrite(plan);

src/optimizer/projection_push_down_optimizer.cpp

@@ -63,6 +63,9 @@ void ProjectionPushDownOptimizer::visitExtend(planner::LogicalOperator* op) {
 
 void ProjectionPushDownOptimizer::visitAccumulate(planner::LogicalOperator* op) {
     auto accumulate = (LogicalAccumulate*)op;
+    if (accumulate->getAccumulateType() != common::AccumulateType::REGULAR) {
+        return;
+    }
     auto expressionsBeforePruning = accumulate->getExpressions();
     auto expressionsAfterPruning = pruneExpressions(expressionsBeforePruning);
     if (expressionsBeforePruning.size() == expressionsAfterPruning.size()) {

src/parser/query/single_query.cpp

@@ -1,23 +0,0 @@
-#include "parser/query/single_query.h"
-
-namespace kuzu {
-namespace parser {
-
-bool SingleQuery::isFirstReadingClauseOptionalMatch() const {
-    for (auto& queryPart : queryParts) {
-        if (queryPart->getNumReadingClauses() != 0 &&
-            queryPart->getReadingClause(0)->getClauseType() == common::ClauseType::MATCH) {
-            return ((MatchClause*)queryPart->getReadingClause(0))->getIsOptional();
-        } else {
-            return false;
-        }
-    }
-    if (getNumReadingClauses() != 0 &&
-        getReadingClause(0)->getClauseType() == common::ClauseType::MATCH) {
-        return ((MatchClause*)getReadingClause(0))->getIsOptional();
-    }
-    return false;
-}
-
-} // namespace parser
-} // namespace kuzu

src/parser/transformer.cpp

@@ -135,8 +135,10 @@ std::unique_ptr<ReadingClause> Transformer::transformReadingClause(
 }
 
 std::unique_ptr<ReadingClause> Transformer::transformMatch(CypherParser::OC_MatchContext& ctx) {
+    auto matchClauseType =
+        ctx.OPTIONAL() ? common::MatchClauseType::OPTIONAL_MATCH : common::MatchClauseType::MATCH;
     auto matchClause =
-        std::make_unique<MatchClause>(transformPattern(*ctx.oC_Pattern()), ctx.OPTIONAL());
+        std::make_unique<MatchClause>(transformPattern(*ctx.oC_Pattern()), matchClauseType);
     if (ctx.oC_Where()) {
         matchClause->setWhereClause(transformWhere(*ctx.oC_Where()));
     }

src/planner/CMakeLists.txt

@@ -1,5 +1,6 @@
 add_subdirectory(join_order)
 add_subdirectory(operator)
+add_subdirectory(plan_operator)
 
 add_library(kuzu_planner
         OBJECT