TrinityCore/src/server/database/Database/QueryResult.h

/*
 * This file is part of the TrinityCore Project. See AUTHORS file for Copyright information
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the
 * Free Software Foundation; either version 2 of the License, or (at your
 * option) any later version.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
 * more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program. If not, see <http://www.gnu.org/licenses/>.
 */

#ifndef QUERYRESULT_H
#define QUERYRESULT_H

#include "Define.h"
#include "DatabaseEnvFwd.h"
#include "Hash.h"
#include <unordered_map>
#include <vector>

namespace Trinity::DB
{
struct FieldLookupByAliasKey
{
    std::size_t HashValue;      ///< Cached hash value (first field to make opeartor== return early, minimizing number of string comparisons)
    std::string_view Alias;

    // implicit constructor from string literal for users of the query result
    consteval FieldLookupByAliasKey(char const* alias) : HashValue(HashFnv1a<>::GetHash(std::span(alias, std::char_traits<char>::length(alias)))), Alias(alias) { }

    // runtime only constructor used internally to fill alias to index mapping
    struct RuntimeInitTag { } static inline constexpr RuntimeInit = { };
    FieldLookupByAliasKey(RuntimeInitTag, std::string_view alias) : HashValue(HashFnv1a<>::GetHash(alias)), Alias(std::move(alias)) { }

    friend bool operator==(FieldLookupByAliasKey const& left, FieldLookupByAliasKey const& right) = default;

    struct Hash { constexpr std::size_t operator()(FieldLookupByAliasKey const& k) const { return k.HashValue; } };
};

using FieldAliasToIndexMap = std::unordered_map<FieldLookupByAliasKey, std::size_t, FieldLookupByAliasKey::Hash>;
}

class TC_DATABASE_API ResultSet
{
    public:
        ResultSet(MySQLResult* result, MySQLField* fields, uint64 rowCount, uint32 fieldCount);
        ~ResultSet();

        bool NextRow();
        uint64 GetRowCount() const { return _rowCount; }
        uint32 GetFieldCount() const { return _fieldCount; }

        Field* Fetch() const { return _currentRow; }
        Field const& operator[](std::size_t index) const;
        Field const& operator[](Trinity::DB::FieldLookupByAliasKey const& alias) const;

        QueryResultFieldMetadata const& GetFieldMetadata(std::size_t index) const;
        QueryResultFieldMetadata const& GetFieldMetadata(Trinity::DB::FieldLookupByAliasKey const& alias) const;

    protected:
        std::vector<QueryResultFieldMetadata> _fieldMetadata;
        Trinity::DB::FieldAliasToIndexMap _fieldIndexByAlias;
        uint64 _rowCount;
        Field* _currentRow;
        uint32 _fieldCount;

    private:
        void CleanUp();
        MySQLResult* _result;
        MySQLField* _fields;

        ResultSet(ResultSet const& right) = delete;
        ResultSet& operator=(ResultSet const& right) = delete;
};

class TC_DATABASE_API PreparedResultSet
{
    public:
        PreparedResultSet(MySQLStmt* stmt, MySQLResult* result, uint64 rowCount, uint32 fieldCount);
        ~PreparedResultSet();

        bool NextRow();
        uint64 GetRowCount() const { return m_rowCount; }
        uint32 GetFieldCount() const { return m_fieldCount; }

        Field* Fetch() const;
        Field const& operator[](std::size_t index) const;
        Field const& operator[](Trinity::DB::FieldLookupByAliasKey const& alias) const;

        QueryResultFieldMetadata const& GetFieldMetadata(std::size_t index) const;
        QueryResultFieldMetadata const& GetFieldMetadata(Trinity::DB::FieldLookupByAliasKey const& alias) const;

    protected:
        std::vector<QueryResultFieldMetadata> m_fieldMetadata;
        Trinity::DB::FieldAliasToIndexMap m_fieldIndexByAlias;
        std::vector<Field> m_rows;
        uint64 m_rowCount;
        uint64 m_rowPosition;
        uint32 m_fieldCount;

    private:
        MySQLBind* m_rBind;
        MySQLStmt* m_stmt;
        MySQLResult* m_metadataResult;    ///< Field metadata, returned by mysql_stmt_result_metadata

        void CleanUp();
        bool _NextRow();

        PreparedResultSet(PreparedResultSet const& right) = delete;
        PreparedResultSet& operator=(PreparedResultSet const& right) = delete;
};

#endif