lbug 0.16.1

An in-process property graph database management system built for query speed and scalability
Documentation 
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#include "binder/expression_visitor.h"
#include "binder/query/reading_clause/bound_load_from.h"
#include "binder/query/reading_clause/bound_match_clause.h"
#include "binder/query/reading_clause/bound_table_function_call.h"
#include "planner/planner.h"

using namespace lbug::binder;
using namespace lbug::common;

namespace lbug {
namespace planner {

void Planner::planReadingClause(const BoundReadingClause& readingClause, LogicalPlan& plan) {
    switch (readingClause.getClauseType()) {
    case ClauseType::MATCH: {
        planMatchClause(readingClause, plan);
    } break;
    case ClauseType::UNWIND: {
        planUnwindClause(readingClause, plan);
    } break;
    case ClauseType::TABLE_FUNCTION_CALL: {
        planTableFunctionCall(readingClause, plan);
    } break;
    case ClauseType::LOAD_FROM: {
        planLoadFrom(readingClause, plan);
    } break;
    default:
        UNREACHABLE_CODE;
    }
}

void Planner::planMatchClause(const BoundReadingClause& readingClause, LogicalPlan& plan) {
    auto& boundMatchClause = readingClause.constCast<BoundMatchClause>();
    auto queryGraphCollection = boundMatchClause.getQueryGraphCollection();
    auto predicates = boundMatchClause.getConjunctivePredicates();
    switch (boundMatchClause.getMatchClauseType()) {
    case MatchClauseType::MATCH: {
        if (plan.isEmpty()) {
            auto info = QueryGraphPlanningInfo();
            info.predicates = predicates;
            info.hint = boundMatchClause.getHint();
            plan = planQueryGraphCollection(*queryGraphCollection, info);
        } else {
            planRegularMatch(*queryGraphCollection, predicates, plan, boundMatchClause.getHint());
        }
    } break;
    case MatchClauseType::OPTIONAL_MATCH: {
        planOptionalMatch(*queryGraphCollection, predicates, plan, boundMatchClause.getHint());
    } break;
    default:
        UNREACHABLE_CODE;
    }
}

void Planner::planUnwindClause(const BoundReadingClause& boundReadingClause, LogicalPlan& plan) {
    if (plan.isEmpty()) { // UNWIND [1, 2, 3, 4] AS x RETURN x
        appendDummyScan(plan);
    }
    appendUnwind(boundReadingClause, plan);
}

class PredicatesDependencyAnalyzer {
public:
    explicit PredicatesDependencyAnalyzer(const expression_vector& outputColumns) {
        for (auto& column : outputColumns) {
            columnNameSet.insert(column->getUniqueName());
        }
    }

    void analyze(const expression_vector& predicates) {
        predicatesDependsOnlyOnOutputColumns.clear();
        predicatesWithOtherDependencies.clear();
        for (auto& predicate : predicates) {
            if (hasExternalDependency(predicate)) {
                predicatesWithOtherDependencies.push_back(predicate);
            } else {
                predicatesDependsOnlyOnOutputColumns.push_back(predicate);
            }
        }
    }

private:
    bool hasExternalDependency(const std::shared_ptr<Expression>& expression) {
        auto collector = DependentVarNameCollector();
        collector.visit(expression);
        for (auto& name : collector.getVarNames()) {
            if (!columnNameSet.contains(name)) {
                return true;
            }
        }
        return false;
    }

public:
    expression_vector predicatesDependsOnlyOnOutputColumns;
    expression_vector predicatesWithOtherDependencies;

private:
    std::unordered_set<std::string> columnNameSet;
};

void Planner::planTableFunctionCall(const BoundReadingClause& readingClause, LogicalPlan& plan) {
    auto& boundCall = readingClause.constCast<BoundTableFunctionCall>();
    auto analyzer = PredicatesDependencyAnalyzer(boundCall.getBindData()->columns);
    analyzer.analyze(boundCall.getConjunctivePredicates());
    DASSERT(boundCall.getTableFunc().getLogicalPlanFunc);
    boundCall.getTableFunc().getLogicalPlanFunc(this, readingClause,
        analyzer.predicatesDependsOnlyOnOutputColumns, plan);
    if (!analyzer.predicatesWithOtherDependencies.empty()) {
        appendFilters(analyzer.predicatesWithOtherDependencies, plan);
    }
}

void Planner::planLoadFrom(const BoundReadingClause& readingClause, LogicalPlan& plan) {
    auto& loadFrom = readingClause.constCast<BoundLoadFrom>();
    auto analyzer = PredicatesDependencyAnalyzer(loadFrom.getInfo()->bindData->columns);
    analyzer.analyze(loadFrom.getConjunctivePredicates());
    auto op = getTableFunctionCall(*loadFrom.getInfo());
    planReadOp(std::move(op), analyzer.predicatesDependsOnlyOnOutputColumns, plan);
    if (!analyzer.predicatesWithOtherDependencies.empty()) {
        appendFilters(analyzer.predicatesWithOtherDependencies, plan);
    }
}

void Planner::planReadOp(std::shared_ptr<LogicalOperator> op, const expression_vector& predicates,
    LogicalPlan& plan) {
    if (!plan.isEmpty()) {
        auto tmpPlan = LogicalPlan();
        tmpPlan.setLastOperator(std::move(op));
        if (!predicates.empty()) {
            appendFilters(predicates, tmpPlan);
        }
        appendCrossProduct(plan, tmpPlan, plan);
    } else {
        plan.setLastOperator(std::move(op));
        if (!predicates.empty()) {
            appendFilters(predicates, plan);
        }
    }
}

} // namespace planner
} // namespace lbug