index_entry_comparison.h

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#pragma once

#include <iosfwd>
#include <tuple>
#include <vector>

#include "mongo/bson/simple_bsonobj_comparator.h"
#include "mongo/db/jsobj.h"
#include "mongo/db/record_id.h"

namespace mongo {

struct IndexKeyEntry {
    IndexKeyEntry(BSONObj key, RecordId loc) : key(std::move(key)), loc(std::move(loc)) {}

    BSONObj key;
    RecordId loc;
};

std::ostream& operator<<(std::ostream& stream, const IndexKeyEntry& entry);

inline bool operator==(const IndexKeyEntry& lhs, const IndexKeyEntry& rhs) {
    return SimpleBSONObjComparator::kInstance.evaluate(lhs.key == rhs.key) && (lhs.loc == rhs.loc);
}

inline bool operator!=(const IndexKeyEntry& lhs, const IndexKeyEntry& rhs) {
    return !(lhs == rhs);
}

struct IndexSeekPoint {
    BSONObj keyPrefix;

    int prefixLen = 0;

    bool prefixExclusive = false;

    std::vector<const BSONElement*> keySuffix;

    std::vector<bool> suffixInclusive;
};

class IndexEntryComparison {
public:
    IndexEntryComparison(Ordering order) : _order(order) {}

    bool operator()(const IndexKeyEntry& lhs, const IndexKeyEntry& rhs) const;

    int compare(const IndexKeyEntry& lhs, const IndexKeyEntry& rhs) const;

    static BSONObj makeQueryObject(const BSONObj& keyPrefix,
                                   int prefixLen,
                                   bool prefixExclusive,
                                   const std::vector<const BSONElement*>& keySuffix,
                                   const std::vector<bool>& suffixInclusive,
                                   const int cursorDirection);

    static BSONObj makeQueryObject(const IndexSeekPoint& seekPoint, bool isForward) {
        return makeQueryObject(seekPoint.keyPrefix,
                               seekPoint.prefixLen,
                               seekPoint.prefixExclusive,
                               seekPoint.keySuffix,
                               seekPoint.suffixInclusive,
                               isForward ? 1 : -1);
    }

private:
    // Ordering is used in comparison() to compare BSONElements
    const Ordering _order;

};  // struct IndexEntryComparison

}  // namespace mongo