oral.h

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/**********************************************************************
 * LeechCraft - modular cross-platform feature rich internet client.
 * Copyright (C) 2006-2014  Georg Rudoy
 *
 * Boost Software License - Version 1.0 - August 17th, 2003
 *
 * Permission is hereby granted, free of charge, to any person or organization
 * obtaining a copy of the software and accompanying documentation covered by
 * this license (the "Software") to use, reproduce, display, distribute,
 * execute, and transmit the Software, and to prepare derivative works of the
 * Software, and to permit third-parties to whom the Software is furnished to
 * do so, all subject to the following:
 *
 * The copyright notices in the Software and this entire statement, including
 * the above license grant, this restriction and the following disclaimer,
 * must be included in all copies of the Software, in whole or in part, and
 * all derivative works of the Software, unless such copies or derivative
 * works are solely in the form of machine-executable object code generated by
 * a source language processor.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT. IN NO EVENT
 * SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE
 * FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE,
 * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 * DEALINGS IN THE SOFTWARE.
 **********************************************************************/
 
#pragma once
 
#include <stdexcept>
#include <type_traits>
#include <memory>
#include <optional>
#include <boost/fusion/include/for_each.hpp>
#include <boost/fusion/include/fold.hpp>
#include <boost/fusion/include/filter_if.hpp>
#include <boost/fusion/container/vector.hpp>
#include <boost/fusion/include/vector.hpp>
#include <boost/fusion/include/transform.hpp>
#include <boost/fusion/include/zip.hpp>
#include <boost/fusion/container/generation/make_vector.hpp>
#include <QStringList>
#include <QDateTime>
#include <QPair>
#include <QSqlQuery>
#include <QSqlRecord>
#include <QVariant>
#include <QDateTime>
#include <QtDebug>
#include <util/sll/qtutil.h>
#include <util/sll/prelude.h>
#include <util/sll/typelist.h>
#include <util/sll/typelevel.h>
#include <util/sll/typegetter.h>
#include <util/sll/detector.h>
#include <util/sll/unreachable.h>
#include <util/sll/void.h>
#include <util/db/dblock.h>
#include <util/db/util.h>
#include "oraltypes.h"
#include "oraldetailfwd.h"
#include "impldefs.h"
#include "sqliteimpl.h"
 
namespace LC
{
namespace Util
{
namespace oral
{
    using QSqlQuery_ptr = std::shared_ptr<QSqlQuery>;
 
    class QueryException : public std::runtime_error
    {
        const QSqlQuery_ptr Query_;
    public:
        QueryException (const std::string& str, const QSqlQuery_ptr& q)
        : std::runtime_error (str)
        , Query_ (q)
        {
        }
 
        ~QueryException () noexcept = default;
 
        const QSqlQuery_ptr& GetQueryPtr () const
        {
            return Query_;
        }
 
        const QSqlQuery& GetQuery () const
        {
            return *Query_;
        }
    };
 
    namespace detail
    {
        template<typename U>
        using MorpherDetector = decltype (std::declval<U> ().FieldNameMorpher (QString {}));
 
        template<typename T>
        QString MorphFieldName (QString str) noexcept
        {
            if constexpr (IsDetected_v<MorpherDetector, T>)
                return T::FieldNameMorpher (str);
            else
            {
                if (str.endsWith ('_'))
                    str.chop (1);
                return str;
            }
        }
 
        template<typename Seq, int Idx>
        QString GetFieldName () noexcept
        {
            return MorphFieldName<Seq> (boost::fusion::extension::struct_member_name<Seq, Idx>::call ());
        }
 
        template<typename S>
        constexpr auto SeqSize = boost::fusion::result_of::size<S>::type::value;
 
        template<typename S>
        constexpr auto SeqIndices = std::make_index_sequence<SeqSize<S>> {};
 
        template<typename S>
        struct GetFieldsNames
        {
            QStringList operator() () const noexcept
            {
                return Run (SeqIndices<S>);
            }
        private:
            template<size_t... Vals>
            QStringList Run (std::index_sequence<Vals...>) const noexcept
            {
                return { GetFieldName<S, Vals> ()... };
            }
        };
 
        template<typename S>
        struct AddressOf
        {
            inline static S Obj_ {};
 
            template<auto P>
            static constexpr auto Ptr () noexcept
            {
                return &(Obj_.*P);
            }
 
            template<int Idx>
            static constexpr auto Index () noexcept
            {
                return &boost::fusion::at_c<Idx> (Obj_);
            }
        };
 
        template<auto Ptr, size_t Idx = 0>
        constexpr size_t FieldIndex () noexcept
        {
            using S = MemberPtrStruct_t<Ptr>;
 
            if constexpr (Idx == SeqSize<S>)
                return -1;
            else
            {
                constexpr auto direct = AddressOf<S>::template Ptr<Ptr> ();
                constexpr auto indexed = AddressOf<S>::template Index<Idx> ();
                if constexpr (std::is_same_v<decltype (direct), decltype (indexed)>)
                {
                    if (indexed == direct)
                        return Idx;
                }
 
                return FieldIndex<Ptr, Idx + 1> ();
            }
        }
 
        template<auto Ptr>
        QString GetFieldNamePtr () noexcept
        {
            using S = MemberPtrStruct_t<Ptr>;
            return GetFieldName<S, FieldIndex<Ptr> ()> ();
        }
 
        template<auto Ptr>
        QString GetQualifiedFieldNamePtr () noexcept
        {
            using S = MemberPtrStruct_t<Ptr>;
            return S::ClassName () + "." + GetFieldName<S, FieldIndex<Ptr> ()> ();
        }
 
        template<typename T>
        using TypeNameDetector = decltype (T::TypeName);
 
        template<typename T>
        constexpr bool TypeNameCustomized = IsDetected_v<TypeNameDetector, T>;
 
        template<typename T>
        using BaseTypeDetector = typename T::BaseType;
 
        template<typename T>
        constexpr bool BaseTypeCustomized = IsDetected_v<BaseTypeDetector, T>;
    }
 
    template<typename ImplFactory, typename T, typename = void>
    struct Type2Name
    {
        QString operator() () const noexcept
        {
            if constexpr (HasType<T> (Typelist<int, qlonglong, qulonglong, bool> {}) || std::is_enum_v<T>)
                return "INTEGER";
            else if constexpr (std::is_same_v<T, double>)
                return "REAL";
            else if constexpr (std::is_same_v<T, QString> || std::is_same_v<T, QDateTime> || std::is_same_v<T, QUrl>)
                return "TEXT";
            else if constexpr (std::is_same_v<T, QByteArray>)
                return ImplFactory::TypeLits::Binary;
            else if constexpr (detail::TypeNameCustomized<T>)
                return T::TypeName;
            else if constexpr (detail::BaseTypeCustomized<T>)
                return Type2Name<ImplFactory, typename T::BaseType> {} ();
            else
                static_assert (std::is_same_v<T, struct Dummy>, "Unsupported type");
        }
    };
 
    template<typename ImplFactory, typename T>
    struct Type2Name<ImplFactory, Unique<T>>
    {
        QString operator() () const noexcept { return Type2Name<ImplFactory, T> () () + " UNIQUE"; }
    };
 
    template<typename ImplFactory, typename T>
    struct Type2Name<ImplFactory, NotNull<T>>
    {
        QString operator() () const noexcept { return Type2Name<ImplFactory, T> () () + " NOT NULL"; }
    };
 
    template<typename ImplFactory, typename T, typename... Tags>
    struct Type2Name<ImplFactory, PKey<T, Tags...>>
    {
        QString operator() () const noexcept { return Type2Name<ImplFactory, T> () () + " PRIMARY KEY"; }
    };
 
    template<typename ImplFactory, typename... Tags>
    struct Type2Name<ImplFactory, PKey<int, Tags...>>
    {
        QString operator() () const noexcept { return ImplFactory::TypeLits::IntAutoincrement; }
    };
 
    template<typename ImplFactory, auto Ptr>
    struct Type2Name<ImplFactory, References<Ptr>>
    {
        QString operator() () const noexcept
        {
            const auto& className = MemberPtrStruct_t<Ptr>::ClassName ();
            return Type2Name<ImplFactory, ReferencesValue_t<Ptr>> () () +
                    " REFERENCES " + className + " (" + detail::GetFieldNamePtr<Ptr> () + ") ON DELETE CASCADE";
        }
    };
 
    template<typename T, typename = void>
    struct ToVariant
    {
        QVariant operator() (const T& t) const noexcept
        {
            if constexpr (std::is_same_v<T, QDateTime>)
                return t.toString (Qt::ISODate);
            else if constexpr (std::is_enum_v<T>)
                return static_cast<qint64> (t);
            else if constexpr (IsIndirect<T> {})
                return ToVariant<typename T::value_type> {} (t);
            else if constexpr (detail::TypeNameCustomized<T>)
                return t.ToVariant ();
            else if constexpr (detail::BaseTypeCustomized<T>)
                return ToVariant<typename T::BaseType> {} (t.ToBaseType ());
            else
                return t;
        }
    };
 
    template<typename T, typename = void>
    struct FromVariant
    {
        T operator() (const QVariant& var) const noexcept
        {
            if constexpr (std::is_same_v<T, QDateTime>)
                return QDateTime::fromString (var.toString (), Qt::ISODate);
            else if constexpr (std::is_enum_v<T>)
                return static_cast<T> (var.value<qint64> ());
            else if constexpr (IsIndirect<T> {})
                return FromVariant<typename T::value_type> {} (var);
            else if constexpr (detail::TypeNameCustomized<T>)
                return T::FromVariant (var);
            else if constexpr (detail::BaseTypeCustomized<T>)
                return T::FromBaseType (FromVariant<typename T::BaseType> {} (var));
            else
                return var.value<T> ();
        }
    };
 
    namespace detail
    {
        template<typename T>
        struct IsPKey : std::false_type {};
 
        template<typename U, typename... Tags>
        struct IsPKey<PKey<U, Tags...>> : std::true_type {};
 
        template<typename T>
        QVariant ToVariantF (const T& t) noexcept
        {
            return ToVariant<T> {} (t);
        }
 
        template<typename T>
        auto MakeInserter (const CachedFieldsData& data, const QSqlQuery_ptr& insertQuery, bool bindPrimaryKey) noexcept
        {
            return [data, insertQuery, bindPrimaryKey] (const T& t)
            {
                boost::fusion::fold (t, data.BoundFields_.begin (),
                        [&] (auto pos, const auto& elem)
                        {
                            using Elem = std::decay_t<decltype (elem)>;
                            if (bindPrimaryKey || !IsPKey<Elem>::value)
                                insertQuery->bindValue (*pos++, ToVariantF (elem));
                            return pos;
                        });
 
                if (!insertQuery->exec ())
                {
                    DBLock::DumpError (*insertQuery);
                    throw QueryException ("insert query execution failed", insertQuery);
                }
            };
        }
 
        template<typename Seq, int Idx>
        using ValueAtC_t = typename boost::fusion::result_of::value_at_c<Seq, Idx>::type;
 
        template<typename Seq, typename Idx>
        using ValueAt_t = typename boost::fusion::result_of::value_at<Seq, Idx>::type;
 
        template<typename Seq, typename MemberIdx = boost::mpl::int_<0>>
        struct FindPKey
        {
            static_assert ((boost::fusion::result_of::size<Seq>::value) != (MemberIdx::value),
                    "Primary key not found");
 
            template<typename T>
            struct Lazy
            {
                using type = T;
            };
 
            using result_type = typename std::conditional_t<
                        IsPKey<ValueAt_t<Seq, MemberIdx>>::value,
                        Lazy<MemberIdx>,
                        Lazy<FindPKey<Seq, typename boost::mpl::next<MemberIdx>::type>>
                    >::type;
        };
 
        template<typename Seq>
        using FindPKeyDetector = boost::mpl::int_<FindPKey<Seq>::result_type::value>;
 
        template<typename Seq>
        constexpr auto HasPKey = IsDetected_v<FindPKeyDetector, Seq>;
 
        template<typename Seq>
        constexpr auto HasAutogenPKey () noexcept
        {
            if constexpr (HasPKey<Seq>)
                return !HasType<NoAutogen> (AsTypelist_t<ValueAtC_t<Seq, FindPKey<Seq>::result_type::value>> {});
            else
                return false;
        }
 
        template<typename T>
        CachedFieldsData BuildCachedFieldsData (const QString& table) noexcept
        {
            const auto& fields = detail::GetFieldsNames<T> {} ();
            const auto& qualified = Util::Map (fields, [&table] (const QString& field) { return table + "." + field; });
            const auto& boundFields = Util::Map (fields, [] (const QString& str) { return ':' + str; });
 
            return { table, fields, qualified, boundFields };
        }
 
        template<typename T>
        CachedFieldsData BuildCachedFieldsData () noexcept
        {
            static CachedFieldsData result = BuildCachedFieldsData<T> (T::ClassName ());
            return result;
        }
 
        template<typename Seq>
        class AdaptInsert
        {
            const QSqlDatabase DB_;
            const CachedFieldsData Data_;
 
            constexpr static bool HasAutogen_ = HasAutogenPKey<Seq> ();
 
            IInsertQueryBuilder_ptr QueryBuilder_;
        public:
            template<typename ImplFactory>
            AdaptInsert (const QSqlDatabase& db, CachedFieldsData data, ImplFactory&& factory) noexcept
            : Data_ { RemovePKey (data) }
            , QueryBuilder_ { factory.MakeInsertQueryBuilder (db, Data_) }
            {
            }
 
            auto operator() (Seq& t, InsertAction action = InsertAction::Default) const
            {
                return Run<true> (t, action);
            }
 
            auto operator() (const Seq& t, InsertAction action = InsertAction::Default) const
            {
                return Run<false> (t, action);
            }
        private:
            template<bool UpdatePKey, typename Val>
            auto Run (Val&& t, InsertAction action) const
            {
                const auto query = QueryBuilder_->GetQuery (action);
 
                MakeInserter<Seq> (Data_, query, !HasAutogen_) (t);
 
                if constexpr (HasAutogen_)
                {
                    constexpr auto index = FindPKey<Seq>::result_type::value;
 
                    const auto& lastId = FromVariant<ValueAtC_t<Seq, index>> {} (query->lastInsertId ());
                    if constexpr (UpdatePKey)
                        boost::fusion::at_c<index> (t) = lastId;
                    else
                        return lastId;
                }
            }
 
            static CachedFieldsData RemovePKey (CachedFieldsData data) noexcept
            {
                if constexpr (HasAutogen_)
                {
                    constexpr auto index = FindPKey<Seq>::result_type::value;
                    data.Fields_.removeAt (index);
                    data.BoundFields_.removeAt (index);
                }
                return data;
            }
        };
 
        template<typename Seq, bool HasPKey = HasPKey<Seq>>
        struct AdaptDelete
        {
            std::function<void (Seq)> Deleter_;
        public:
            template<bool B = HasPKey>
            AdaptDelete (const QSqlDatabase& db, const CachedFieldsData& data, std::enable_if_t<B>* = nullptr) noexcept
            {
                const auto index = FindPKey<Seq>::result_type::value;
 
                const auto& boundName = data.BoundFields_.at (index);
                const auto& del = "DELETE FROM " + data.Table_ +
                        " WHERE " + data.Fields_.at (index) + " = " + boundName;
 
                const auto deleteQuery = std::make_shared<QSqlQuery> (db);
                deleteQuery->prepare (del);
 
                Deleter_ = [deleteQuery, boundName] (const Seq& t)
                {
                    constexpr auto index = FindPKey<Seq>::result_type::value;
                    deleteQuery->bindValue (boundName, ToVariantF (boost::fusion::at_c<index> (t)));
                    if (!deleteQuery->exec ())
                        throw QueryException ("delete query execution failed", deleteQuery);
                };
            }
 
            template<bool B = HasPKey>
            AdaptDelete (const QSqlDatabase&, const CachedFieldsData&, std::enable_if_t<!B>* = nullptr) noexcept
            {
            }
 
            template<bool B = HasPKey>
            std::enable_if_t<B> operator() (const Seq& seq)
            {
                Deleter_ (seq);
            }
        };
 
        template<typename T, typename... Args>
        using AggregateDetector_t = decltype (new T { std::declval<Args> ()... });
 
        template<typename T, size_t... Indices>
        T InitializeFromQuery (const QSqlQuery& q, std::index_sequence<Indices...>, int startIdx) noexcept
        {
            if constexpr (IsDetected_v<AggregateDetector_t, T, ValueAtC_t<T, Indices>...>)
                return T { FromVariant<ValueAtC_t<T, Indices>> {} (q.value (startIdx + Indices))... };
            else
            {
                T t;
                const auto dummy = std::initializer_list<int>
                {
                    (static_cast<void> (boost::fusion::at_c<Indices> (t) = FromVariant<ValueAtC_t<T, Indices>> {} (q.value (startIdx + Indices))), 0)...
                };
                Q_UNUSED (dummy);
                return t;
            }
        }
 
        enum class ExprType
        {
            ConstTrue,
 
            LeafStaticPlaceholder,
            LeafData,
 
            Greater,
            Less,
            Equal,
            Geq,
            Leq,
            Neq,
 
            Like,
 
            And,
            Or
        };
 
        inline QString TypeToSql (ExprType type) noexcept
        {
            switch (type)
            {
            case ExprType::Greater:
                return ">";
            case ExprType::Less:
                return "<";
            case ExprType::Equal:
                return "=";
            case ExprType::Geq:
                return ">=";
            case ExprType::Leq:
                return "<=";
            case ExprType::Neq:
                return "!=";
            case ExprType::Like:
                return "LIKE";
            case ExprType::And:
                return "AND";
            case ExprType::Or:
                return "OR";
 
            case ExprType::LeafStaticPlaceholder:
            case ExprType::LeafData:
            case ExprType::ConstTrue:
                return "invalid type";
            }
 
            Util::Unreachable ();
        }
 
        constexpr bool IsRelational (ExprType type) noexcept
        {
            return type == ExprType::Greater ||
                    type == ExprType::Less ||
                    type == ExprType::Equal ||
                    type == ExprType::Geq ||
                    type == ExprType::Leq ||
                    type == ExprType::Neq ||
                    type == ExprType::Like;
        }
 
        template<typename T>
        struct ToSqlState
        {
            int LastID_;
            QVariantMap BoundMembers_;
        };
 
        template<typename T>
        struct WrapDirect
        {
            using value_type = T;
        };
 
        template<typename T>
        using UnwrapIndirect_t = typename std::conditional_t<IsIndirect<T> {},
                T,
                WrapDirect<T>>::value_type;
 
        template<typename Seq, typename L, typename R>
        using ComparableDetector = decltype (std::declval<UnwrapIndirect_t<typename L::template ValueType_t<Seq>>> () ==
                std::declval<UnwrapIndirect_t<typename R::template ValueType_t<Seq>>> ());
 
        template<typename Seq, typename L, typename R>
        constexpr auto AreComparableTypes = IsDetected_v<ComparableDetector, Seq, L, R> || IsDetected_v<ComparableDetector, Seq, R, L>;
 
        template<typename Seq, typename L, typename R, typename = void>
        struct RelationalTypesCheckerBase : std::false_type {};
 
        template<typename Seq, typename L, typename R>
        struct RelationalTypesCheckerBase<Seq, L, R, std::enable_if_t<AreComparableTypes<Seq, L, R>>> : std::true_type {};
 
        template<ExprType Type, typename Seq, typename L, typename R, typename = void>
        struct RelationalTypesChecker : std::true_type {};
 
        template<ExprType Type, typename Seq, typename L, typename R>
        struct RelationalTypesChecker<Type, Seq, L, R, std::enable_if_t<IsRelational (Type)>> : RelationalTypesCheckerBase<Seq, L, R> {};
 
        template<ExprType Type, typename L = void, typename R = void>
        class ExprTree;
 
        template<typename T>
        struct IsExprTree : std::false_type {};
 
        template<ExprType Type, typename L, typename R>
        struct IsExprTree<ExprTree<Type, L, R>> : std::true_type {};
 
        template<typename L, typename R>
        class AssignList
        {
            L Left_;
            R Right_;
        public:
            AssignList (const L& l, const R& r) noexcept
            : Left_ { l }
            , Right_ { r }
            {
            }
 
            template<typename T>
            QString ToSql (ToSqlState<T>& state) const noexcept
            {
                if constexpr (IsExprTree<L> {})
                    return Left_.GetFieldName () + " = " + Right_.ToSql (state);
                else
                    return Left_.ToSql (state) + ", " + Right_.ToSql (state);
            }
 
            template<typename OL, typename OR>
            auto operator, (const AssignList<OL, OR>& tail) noexcept
            {
                return AssignList<AssignList<L, R>, AssignList<OL, OR>> { *this, tail };
            }
        };
 
        template<ExprType Type, typename L, typename R>
        class ExprTree
        {
            L Left_;
            R Right_;
        public:
            ExprTree (const L& l, const R& r) noexcept
            : Left_ (l)
            , Right_ (r)
            {
            }
 
            template<typename T>
            QString ToSql (ToSqlState<T>& state) const noexcept
            {
                static_assert (RelationalTypesChecker<Type, T, L, R>::value,
                        "Incompatible types passed to a relational operator.");
 
                return Left_.ToSql (state) + " " + TypeToSql (Type) + " " + Right_.ToSql (state);
            }
 
            template<typename T>
            QSet<QString> AdditionalTables () const noexcept
            {
                return Left_.template AdditionalTables<T> () + Right_.template AdditionalTables<T> ();
            }
 
            template<typename T>
            constexpr static bool HasAdditionalTables () noexcept
            {
                return L::template HasAdditionalTables<T> () || R::template HasAdditionalTables<T> ();
            }
        };
 
        template<auto... Ptr>
        struct MemberPtrs {};
 
        template<auto Ptr>
        class ExprTree<ExprType::LeafStaticPlaceholder, MemberPtrs<Ptr>, void>
        {
        public:
            template<typename>
            using ValueType_t = MemberPtrType_t<Ptr>;
 
            template<typename T>
            QString ToSql (ToSqlState<T>&) const noexcept
            {
                return MemberPtrStruct_t<Ptr>::ClassName () + "." + GetFieldName ();
            }
 
            QString GetFieldName () const noexcept
            {
                return detail::GetFieldNamePtr<Ptr> ();
            }
 
            template<typename T>
            QSet<QString> AdditionalTables () const noexcept
            {
                using Seq = MemberPtrStruct_t<Ptr>;
                if constexpr (std::is_same_v<Seq, T>)
                    return {};
                else
                    return { Seq::ClassName () };
            }
 
            template<typename T>
            constexpr static bool HasAdditionalTables () noexcept
            {
                return !std::is_same_v<MemberPtrStruct_t<Ptr>, T>;
            }
 
            template<typename R>
            auto operator= (const R&) const noexcept;
        };
 
        template<typename T>
        class ExprTree<ExprType::LeafData, T, void>
        {
            T Data_;
        public:
            template<typename>
            using ValueType_t = T;
 
            ExprTree (const T& t) noexcept
            : Data_ (t)
            {
            }
 
            template<typename ObjT>
            QString ToSql (ToSqlState<ObjT>& state) const noexcept
            {
                const auto& name = ":bound_" + QString::number (++state.LastID_);
                state.BoundMembers_ [name] = ToVariantF (Data_);
                return name;
            }
 
            template<typename>
            QSet<QString> AdditionalTables () const noexcept
            {
                return {};
            }
 
            template<typename>
            constexpr static bool HasAdditionalTables () noexcept
            {
                return false;
            }
        };
 
        template<>
        class ExprTree<ExprType::ConstTrue, void, void> {};
 
        constexpr auto ConstTrueTree_v = ExprTree<ExprType::ConstTrue> {};
 
        template<typename T>
        constexpr auto AsLeafData (const T& node) noexcept
        {
            if constexpr (IsExprTree<T> {})
                return node;
            else
                return ExprTree<ExprType::LeafData, T> { node };
        }
 
        template<auto Ptr>
        template<typename R>
        auto ExprTree<ExprType::LeafStaticPlaceholder, MemberPtrs<Ptr>, void>::operator= (const R& r) const noexcept
        {
            return AssignList { *this, AsLeafData (r) };
        }
 
        template<ExprType Type, typename L, typename R>
        auto MakeExprTree (const L& left, const R& right) noexcept
        {
            using EL = decltype (AsLeafData (left));
            using ER = decltype (AsLeafData (right));
            return ExprTree<Type, EL, ER> { AsLeafData (left), AsLeafData (right) };
        }
 
        template<typename L, typename R>
        constexpr bool EitherIsExprTree () noexcept
        {
            if (IsExprTree<L> {})
                return true;
            if (IsExprTree<R> {})
                return true;
            return false;
        }
 
        template<typename L, typename R>
        using EnableRelOp_t = std::enable_if_t<EitherIsExprTree<L, R> ()>;
 
        template<typename L, typename R, typename = EnableRelOp_t<L, R>>
        auto operator< (const L& left, const R& right) noexcept
        {
            return MakeExprTree<ExprType::Less> (left, right);
        }
 
        template<typename L, typename R, typename = EnableRelOp_t<L, R>>
        auto operator> (const L& left, const R& right) noexcept
        {
            return MakeExprTree<ExprType::Greater> (left, right);
        }
 
        template<typename L, typename R, typename = EnableRelOp_t<L, R>>
        auto operator== (const L& left, const R& right) noexcept
        {
            return MakeExprTree<ExprType::Equal> (left, right);
        }
 
        template<typename L, typename R, typename = EnableRelOp_t<L, R>>
        auto operator!= (const L& left, const R& right) noexcept
        {
            return MakeExprTree<ExprType::Neq> (left, right);
        }
 
        template<ExprType Op>
        struct InfixBinary {};
    }
 
    namespace infix
    {
        constexpr detail::InfixBinary<detail::ExprType::Like> like {};
    }
 
    namespace detail
    {
        template<typename L, ExprType Op>
        struct InfixBinaryProxy
        {
            const L& Left_;
        };
 
        template<typename L, ExprType Op>
        auto operator| (const L& left, InfixBinary<Op>) noexcept
        {
            return InfixBinaryProxy<L, Op> { left };
        }
 
        template<typename L, ExprType Op, typename R>
        auto operator| (const InfixBinaryProxy<L, Op>& left, const R& right) noexcept
        {
            return MakeExprTree<Op> (left.Left_, right);
        }
 
        template<typename L, typename R, typename = EnableRelOp_t<L, R>>
        auto operator&& (const L& left, const R& right) noexcept
        {
            return MakeExprTree<ExprType::And> (left, right);
        }
 
        template<typename L, typename R, typename = EnableRelOp_t<L, R>>
        auto operator|| (const L& left, const R& right) noexcept
        {
            return MakeExprTree<ExprType::Or> (left, right);
        }
 
        template<typename F>
        struct ExprTreeHandler
        {
            QString Sql_;
            F Binder_;
            int LastID_;
 
            ExprTreeHandler (const QString& sql, F&& binder, int lastId) noexcept
            : Sql_ { sql }
            , Binder_ { std::move (binder) }
            , LastID_ { lastId }
            {
            }
        };
 
        template<typename>
        auto HandleExprTree (const ExprTree<ExprType::ConstTrue>&, int lastId = 0) noexcept
        {
            return ExprTreeHandler { QString {}, Void {}, lastId };
        }
 
        template<typename Seq, typename Tree,
                typename = decltype (std::declval<Tree> ().ToSql (std::declval<ToSqlState<Seq>&> ()))>
        auto HandleExprTree (const Tree& tree, int lastId = 0) noexcept
        {
            ToSqlState<Seq> state { lastId, {} };
 
            const auto& sql = tree.ToSql (state);
 
            return ExprTreeHandler
            {
                sql,
                [state] (QSqlQuery& query)
                {
                    for (const auto& pair : Stlize (state.BoundMembers_))
                        query.bindValue (pair.first, pair.second);
                },
                state.LastID_
            };
        }
 
        enum class AggregateFunction
        {
            Count,
            Min,
            Max
        };
 
        template<AggregateFunction, auto Ptr>
        struct AggregateType {};
 
        struct CountAll {};
 
        inline constexpr CountAll *CountAllPtr = nullptr;
 
        template<typename... MemberDirectionList>
        struct OrderBy {};
 
        template<auto... Ptrs>
        struct GroupBy {};
 
        struct SelectWhole {};
 
        template<typename L, typename R>
        struct SelectorUnion {};
 
        template<typename T>
        struct IsSelector : std::false_type {};
 
        template<>
        struct IsSelector<SelectWhole> : std::true_type {};
 
        template<AggregateFunction Fun, auto Ptr>
        struct IsSelector<AggregateType<Fun, Ptr>> : std::true_type {};
 
        template<auto... Ptrs>
        struct IsSelector<MemberPtrs<Ptrs...>> : std::true_type {};
 
        template<typename L, typename R>
        struct IsSelector<SelectorUnion<L, R>> : std::true_type {};
 
        template<typename L, typename R, typename = std::enable_if_t<IsSelector<L> {} && IsSelector<R> {}>>
        SelectorUnion<L, R> operator+ (L, R) noexcept
        {
            return {};
        }
    }
 
    namespace sph
    {
        template<auto Ptr>
        constexpr detail::ExprTree<detail::ExprType::LeafStaticPlaceholder, detail::MemberPtrs<Ptr>> f {};
 
        template<auto... Ptrs>
        constexpr detail::MemberPtrs<Ptrs...> fields {};
 
        constexpr detail::SelectWhole all {};
 
        template<auto... Ptrs>
        struct asc {};
 
        template<auto... Ptrs>
        struct desc {};
 
        template<auto Ptr = detail::CountAllPtr>
        constexpr detail::AggregateType<detail::AggregateFunction::Count, Ptr> count {};
 
        template<auto Ptr>
        constexpr detail::AggregateType<detail::AggregateFunction::Min, Ptr> min {};
 
        template<auto Ptr>
        constexpr detail::AggregateType<detail::AggregateFunction::Max, Ptr> max {};
    };
 
    template<typename... Orders>
    constexpr detail::OrderBy<Orders...> OrderBy {};
 
    template<auto... Ptrs>
    constexpr detail::GroupBy<Ptrs...> GroupBy {};
 
    struct Limit
    {
        uint64_t Count;
 
        Limit (uint64_t count) noexcept
        : Count { count }
        {
        }
    };
 
    struct Offset
    {
        uint64_t Count;
 
        Offset (uint64_t count) noexcept
        : Count { count }
        {
        }
    };
 
    namespace detail
    {
        template<auto... Ptrs, size_t... Idxs>
        auto MakeIndexedQueryHandler (MemberPtrs<Ptrs...>, std::index_sequence<Idxs...>) noexcept
        {
            return [] (const QSqlQuery& q, int startIdx = 0) noexcept
            {
                if constexpr (sizeof... (Ptrs) == 1)
                    return FromVariant<UnwrapIndirect_t<Head_t<Typelist<MemberPtrType_t<Ptrs>...>>>> {} (q.value (startIdx));
                else
                    return std::tuple { FromVariant<UnwrapIndirect_t<MemberPtrType_t<Ptrs>>> {} (q.value (startIdx + Idxs))... };
            };
        }
 
        template<auto Ptr>
        auto MakeIndexedQueryHandler () noexcept
        {
            return [] (const QSqlQuery& q, int startIdx = 0) noexcept
            {
                return FromVariant<UnwrapIndirect_t<MemberPtrType_t<Ptr>>> {} (q.value (startIdx));
            };
        }
 
        template<auto... Ptrs>
        QStringList BuildFieldNames () noexcept
        {
            return { BuildCachedFieldsData<MemberPtrStruct_t<Ptrs>> ().QualifiedFields_.value (FieldIndex<Ptrs> ())... };
        }
 
        enum class SelectBehaviour { Some, One };
 
        struct OrderNone {};
        struct GroupNone {};
        struct LimitNone {};
        struct OffsetNone {};
 
        template<size_t RepIdx, size_t TupIdx, typename Tuple, typename NewType>
        constexpr decltype (auto) GetReplaceTupleElem (Tuple&& tuple, NewType&& arg) noexcept
        {
            if constexpr (RepIdx == TupIdx)
                return std::forward<NewType> (arg);
            else
                return std::get<TupIdx> (tuple);
        }
 
        template<size_t RepIdx, typename NewType, typename Tuple, size_t... TupIdxs>
        constexpr auto ReplaceTupleElemImpl (Tuple&& tuple, NewType&& arg, std::index_sequence<TupIdxs...>) noexcept
        {
            return std::tuple
            {
                GetReplaceTupleElem<RepIdx, TupIdxs> (std::forward<Tuple> (tuple), std::forward<NewType> (arg))...
            };
        }
 
        template<size_t RepIdx, typename NewType, typename... TupleArgs>
        constexpr auto ReplaceTupleElem (std::tuple<TupleArgs...>&& tuple, NewType&& arg) noexcept
        {
            return ReplaceTupleElemImpl<RepIdx> (std::move (tuple),
                    std::forward<NewType> (arg),
                    std::index_sequence_for<TupleArgs...> {});
        }
 
        template<typename Seq, typename T>
        struct DetectShift
        {
            constexpr static int Value = 1;
        };
 
        template<typename Seq, typename... Args>
        struct DetectShift<Seq, std::tuple<Args...>>
        {
            constexpr static int Value = (DetectShift<Seq, Args>::Value + ...);
        };
 
        template<typename Seq>
        struct DetectShift<Seq, Seq>
        {
            constexpr static int Value = SeqSize<Seq>;
        };
 
        template<typename... LArgs, typename... RArgs>
        auto Combine (std::tuple<LArgs...>&& left, std::tuple<RArgs...>&& right) noexcept
        {
            return std::tuple_cat (std::move (left), std::move (right));
        }
 
        template<typename... LArgs, typename R>
        auto Combine (std::tuple<LArgs...>&& left, const R& right) noexcept
        {
            return std::tuple_cat (std::move (left), std::tuple { right });
        }
 
        template<typename L, typename... RArgs>
        auto Combine (const L& left, std::tuple<RArgs...>&& right) noexcept
        {
            return std::tuple_cat (std::tuple { left }, std::move (right));
        }
 
        template<typename L, typename R>
        auto Combine (const L& left, const R& right) noexcept
        {
            return std::tuple { left, right };
        }
 
        struct ResultBehaviour
        {
            struct All {};
            struct First {};
        };
 
        template<typename L, typename R>
        constexpr auto CombineBehaviour (L, R) noexcept
        {
            if constexpr (std::is_same_v<L, ResultBehaviour::First> && std::is_same_v<R, ResultBehaviour::First>)
                return ResultBehaviour::First {};
            else
                return ResultBehaviour::All {};
        }
 
        template<typename ResList>
        decltype (auto) HandleResultBehaviour (ResultBehaviour::All, ResList&& list) noexcept
        {
            return std::forward<ResList> (list);
        }
 
        template<typename ResList>
        auto HandleResultBehaviour (ResultBehaviour::First, ResList&& list) noexcept
        {
            return list.value (0);
        }
 
        template<typename F, typename R>
        struct HandleSelectorResult
        {
            QString Fields_;
            F Initializer_;
            R Behaviour_;
        };
 
        template<typename F, typename R>
        HandleSelectorResult (QString, F, R) -> HandleSelectorResult<F, R>;
 
        class SelectWrapperCommon
        {
        protected:
            const QSqlDatabase DB_;
            const QString LimitNone_;
 
            SelectWrapperCommon (const QSqlDatabase& db, const QString& limitNone)
            : DB_ { db }
            , LimitNone_ { limitNone }
            {
            }
 
            auto RunQuery (const QString& fields, const QString& from,
                    QString where, std::function<void (QSqlQuery&)>&& binder,
                    const QString& orderStr,
                    const QString& groupStr,
                    const QString& limitOffsetStr) const
            {
                if (!where.isEmpty ())
                    where.prepend (" WHERE ");
 
                const auto& queryStr = "SELECT " + fields +
                        " FROM " + from +
                        where +
                        orderStr +
                        groupStr +
                        limitOffsetStr;
 
                QSqlQuery query { DB_ };
                query.prepare (queryStr);
                if (binder)
                    binder (query);
 
                if (!query.exec ())
                {
                    DBLock::DumpError (query);
                    throw QueryException ("fetch query execution failed", std::make_shared<QSqlQuery> (query));
                }
 
                return query;
            }
 
            QString HandleLimitOffset (LimitNone, OffsetNone) const noexcept
            {
                return {};
            }
 
            QString HandleLimitOffset (Limit limit, OffsetNone) const noexcept
            {
                return " LIMIT " + QString::number (limit.Count);
            }
 
            template<typename L>
            QString HandleLimitOffset (L limit, Offset offset) const noexcept
            {
                QString limitStr;
                if constexpr (std::is_same_v<std::decay_t<L>, LimitNone>)
                {
                    Q_UNUSED (limit)
                    limitStr = LimitNone_;
                }
                else if constexpr (std::is_integral_v<L>)
                    limitStr = QString::number (limit);
                else
                    limitStr = QString::number (limit.Count);
                return " LIMIT " + limitStr +
                        " OFFSET " + QString::number (offset.Count);
            }
        };
 
        template<typename T, SelectBehaviour SelectBehaviour>
        class SelectWrapper : SelectWrapperCommon
        {
            const CachedFieldsData Cached_;
 
            template<typename ParamsTuple>
            struct Builder
            {
                const SelectWrapper& W_;
                ParamsTuple Params_;
 
                template<typename NewTuple>
                constexpr auto RepTuple (NewTuple&& tuple) noexcept
                {
                    return Builder<NewTuple> { W_, tuple };
                }
 
                template<typename U>
                constexpr auto Select (U&& selector) && noexcept
                {
                    return RepTuple (ReplaceTupleElem<0> (std::move (Params_), std::forward<U> (selector)));
                }
 
                template<typename U>
                constexpr auto Where (U&& tree) && noexcept
                {
                    return RepTuple (ReplaceTupleElem<1> (std::move (Params_), std::forward<U> (tree)));
                }
 
                template<typename U>
                constexpr auto Order (U&& order) && noexcept
                {
                    return RepTuple (ReplaceTupleElem<2> (std::move (Params_), std::forward<U> (order)));
                }
 
                template<typename U>
                constexpr auto Group (U&& group) && noexcept
                {
                    return RepTuple (ReplaceTupleElem<3> (std::move (Params_), std::forward<U> (group)));
                }
 
                template<typename U = Limit>
                constexpr auto Limit (U&& limit) && noexcept
                {
                    return RepTuple (ReplaceTupleElem<4> (std::move (Params_), std::forward<U> (limit)));
                }
 
                template<typename U = Offset>
                constexpr auto Offset (U&& offset) && noexcept
                {
                    return RepTuple (ReplaceTupleElem<5> (std::move (Params_), std::forward<U> (offset)));
                }
 
                auto operator() () &&
                {
                    return std::apply (W_, Params_);
                }
 
                template<auto... Ptrs>
                constexpr auto Group () && noexcept
                {
                    return std::move (*this).Group (GroupBy<Ptrs...> {});
                }
            };
        public:
            template<typename ImplFactory>
            SelectWrapper (const QSqlDatabase& db, const CachedFieldsData& data, ImplFactory&& factory) noexcept
            : SelectWrapperCommon { db, factory.LimitNone }
            , Cached_ { data }
            {
            }
 
            auto Build () const noexcept
            {
                std::tuple defParams
                {
                    SelectWhole {},
                    ConstTrueTree_v,
                    OrderNone {},
                    GroupNone {},
                    LimitNone {},
                    OffsetNone {}
                };
                return Builder<decltype (defParams)> { *this, defParams };
            }
 
            auto operator() () const
            {
                return (*this) (SelectWhole {}, ConstTrueTree_v);
            }
 
            template<typename Single>
            auto operator() (Single&& single) const
            {
                if constexpr (IsExprTree<std::decay_t<Single>> {})
                    return (*this) (SelectWhole {}, std::forward<Single> (single));
                else
                    return (*this) (std::forward<Single> (single), ConstTrueTree_v);
            }
 
            template<
                    typename Selector,
                    ExprType Type, typename L, typename R,
                    typename Order = OrderNone,
                    typename Group = GroupNone,
                    typename Limit = LimitNone,
                    typename Offset = OffsetNone
                >
            auto operator() (Selector selector,
                    const ExprTree<Type, L, R>& tree,
                    Order order = OrderNone {},
                    Group group = GroupNone {},
                    Limit limit = LimitNone {},
                    Offset offset = OffsetNone {}) const
            {
                const auto& [where, binder, _] = HandleExprTree<T> (tree);
                Q_UNUSED (_);
                const auto& [fields, initializer, resultBehaviour] = HandleSelector (std::forward<Selector> (selector));
                return HandleResultBehaviour (resultBehaviour,
                        Select (fields, BuildFromClause (tree),
                                where, binder,
                                initializer,
                                HandleOrder (std::forward<Order> (order)),
                                HandleGroup (std::forward<Group> (group)),
                                HandleLimitOffset (std::forward<Limit> (limit), std::forward<Offset> (offset))));
            }
        private:
            template<typename Binder, typename Initializer>
            auto Select (const QString& fields, const QString& from,
                    const QString& where, Binder&& binder,
                    Initializer&& initializer,
                    const QString& orderStr,
                    const QString& groupStr,
                    const QString& limitOffsetStr) const
            {
                std::function<void (QSqlQuery&)> binderFunc;
                if constexpr (!std::is_same_v<Void, std::decay_t<Binder>>)
                    binderFunc = binder;
                auto query = RunQuery (fields, from, where, std::move (binderFunc), orderStr, groupStr, limitOffsetStr);
 
                if constexpr (SelectBehaviour == SelectBehaviour::Some)
                {
                    QList<std::result_of_t<Initializer (QSqlQuery)>> result;
                    while (query.next ())
                        result << initializer (query);
                    return result;
                }
                else
                {
                    using RetType_t = std::optional<std::result_of_t<Initializer (QSqlQuery)>>;
                    return query.next () ?
                        RetType_t { initializer (query) } :
                        RetType_t {};
                }
            }
 
            template<ExprType Type, typename L, typename R>
            QString BuildFromClause (const ExprTree<Type, L, R>& tree) const noexcept
            {
                if constexpr (Type != ExprType::ConstTrue)
                {
                    auto result = Cached_.Table_;
                    for (const auto& item : tree.template AdditionalTables<T> ())
                        result += ", " + item;
                    return result;
                }
                else
                    return Cached_.Table_;
            }
 
            auto HandleSelector (SelectWhole) const noexcept
            {
                return HandleSelectorResult
                {
                    Cached_.QualifiedFields_.join (", "),
                    [] (const QSqlQuery& q, int startIdx = 0)
                    {
                        return InitializeFromQuery<T> (q, SeqIndices<T>, startIdx);
                    },
                    ResultBehaviour::All {}
                };
            }
 
            template<auto... Ptrs>
            auto HandleSelector (MemberPtrs<Ptrs...> ptrs) const noexcept
            {
                return HandleSelectorResult
                {
                    BuildFieldNames<Ptrs...> ().join (", "),
                    MakeIndexedQueryHandler (ptrs, std::make_index_sequence<sizeof... (Ptrs)> {}),
                    ResultBehaviour::All {}
                };
            }
 
            auto HandleSelector (AggregateType<AggregateFunction::Count, CountAllPtr>) const noexcept
            {
                return HandleSelectorResult
                {
                    "count(1)",
                    [] (const QSqlQuery& q, int startIdx = 0) { return q.value (startIdx).toLongLong (); },
                    ResultBehaviour::First {}
                };
            }
 
            template<auto Ptr>
            auto HandleSelector (AggregateType<AggregateFunction::Count, Ptr>) const noexcept
            {
                return HandleSelectorResult
                {
                    "count(" + GetQualifiedFieldNamePtr<Ptr> () + ")",
                    [] (const QSqlQuery& q, int startIdx = 0) { return q.value (startIdx).toLongLong (); },
                    ResultBehaviour::First {}
                };
            }
 
            template<auto Ptr>
            auto HandleSelector (AggregateType<AggregateFunction::Min, Ptr>) const noexcept
            {
                return HandleSelectorResult
                {
                    "min(" + GetQualifiedFieldNamePtr<Ptr> () + ")",
                    MakeIndexedQueryHandler<Ptr> (),
                    ResultBehaviour::First {}
                };
            }
 
            template<auto Ptr>
            auto HandleSelector (AggregateType<AggregateFunction::Max, Ptr>) const noexcept
            {
                return HandleSelectorResult
                {
                    "max(" + GetQualifiedFieldNamePtr<Ptr> () + ")",
                    MakeIndexedQueryHandler<Ptr> (),
                    ResultBehaviour::First {}
                };
            }
 
            template<typename L, typename R>
            auto HandleSelector (SelectorUnion<L, R>) const noexcept
            {
                const auto& lSel = HandleSelector (L {});
                const auto& rSel = HandleSelector (R {});
 
                const auto& lHandler = lSel.Initializer_;
                const auto& rHandler = rSel.Initializer_;
 
                return HandleSelectorResult
                {
                    lSel.Fields_ + ", " + rSel.Fields_,
                    [lHandler, rHandler] (const QSqlQuery& q, int startIdx = 0)
                    {
                        constexpr auto shift = DetectShift<T, decltype (lHandler (q))>::Value;
                        return Combine (lHandler (q, startIdx), rHandler (q, startIdx + shift));
                    },
                    CombineBehaviour (lSel.Behaviour_, rSel.Behaviour_)
                };
            }
 
            QString HandleOrder (OrderNone) const noexcept
            {
                return {};
            }
 
            template<auto... Ptrs>
            QList<QString> HandleSuborder (sph::asc<Ptrs...>) const noexcept
            {
                return { (GetQualifiedFieldNamePtr<Ptrs> () + " ASC")... };
            }
 
            template<auto... Ptrs>
            QList<QString> HandleSuborder (sph::desc<Ptrs...>) const noexcept
            {
                return { (GetQualifiedFieldNamePtr<Ptrs> () + " DESC")... };
            }
 
            template<typename... Suborders>
            QString HandleOrder (OrderBy<Suborders...>) const noexcept
            {
                return " ORDER BY " + QStringList { Concat (QList { HandleSuborder (Suborders {})... }) }.join (", ");
            }
 
            QString HandleGroup (GroupNone) const noexcept
            {
                return {};
            }
 
            template<auto... Ptrs>
            QString HandleGroup (GroupBy<Ptrs...>) const noexcept
            {
                return " GROUP BY " + QStringList { GetQualifiedFieldNamePtr<Ptrs> ()... }.join (", ");
            }
        };
 
        template<typename T>
        class DeleteByFieldsWrapper
        {
            const QSqlDatabase DB_;
            const QString Table_;
        public:
            DeleteByFieldsWrapper (const QSqlDatabase& db, const CachedFieldsData& data) noexcept
            : DB_ { db }
            , Table_ (data.Table_)
            {
            }
 
            template<ExprType Type, typename L, typename R>
            void operator() (const ExprTree<Type, L, R>& tree) const noexcept
            {
                const auto& [where, binder, _] = HandleExprTree<T> (tree);
                Q_UNUSED (_);
 
                const auto& selectAll = "DELETE FROM " + Table_ +
                        " WHERE " + where;
 
                QSqlQuery query { DB_ };
                query.prepare (selectAll);
                binder (query);
                query.exec ();
            }
        };
 
        template<typename T, bool HasPKey = HasPKey<T>>
        class AdaptUpdate
        {
            const QSqlDatabase DB_;
            const QString Table_;
 
            std::function<void (T)> Updater_;
        public:
            AdaptUpdate (const QSqlDatabase& db, const CachedFieldsData& data) noexcept
            : DB_ { db }
            , Table_ { data.Table_ }
            {
                if constexpr (HasPKey)
                {
                    constexpr auto index = FindPKey<T>::result_type::value;
 
                    auto statements = Util::ZipWith<QList> (data.Fields_, data.BoundFields_,
                            [] (const QString& s1, const QString& s2) { return s1 + " = " + s2; });
                    auto wherePart = statements.takeAt (index);
                    const auto& update = "UPDATE " + data.Table_ +
                            " SET " + statements.join (", ") +
                            " WHERE " + wherePart;
 
                    const auto updateQuery = std::make_shared<QSqlQuery> (db);
                    updateQuery->prepare (update);
                    Updater_ = MakeInserter<T> (data, updateQuery, true);
                }
            }
 
            template<bool B = HasPKey>
            std::enable_if_t<B> operator() (const T& seq)
            {
                Updater_ (seq);
            }
 
            template<typename SL, typename SR, ExprType WType, typename WL, typename WR>
            int operator() (const AssignList<SL, SR>& set, const ExprTree<WType, WL, WR>& where)
            {
                static_assert (!ExprTree<WType, WL, WR>::template HasAdditionalTables<T> (),
                        "joins in update statements are not supported by SQL");
 
                const auto& [setClause, setBinder, setLast] = HandleExprTree<T> (set);
                const auto& [whereClause, whereBinder, _] = HandleExprTree<T> (where, setLast);
 
                const auto& update = "UPDATE " + Table_ +
                        " SET " + setClause +
                        " WHERE " + whereClause;
 
                QSqlQuery query { DB_ };
                query.prepare (update);
                setBinder (query);
                whereBinder (query);
                if (!query.exec ())
                {
                    DBLock::DumpError (query);
                    throw QueryException ("update query execution failed", std::make_shared<QSqlQuery> (query));
                }
 
                return query.numRowsAffected ();
            }
        };
 
        template<typename T>
        using ConstraintsDetector = typename T::Constraints;
 
        template<typename T>
        using ConstraintsType = Util::IsDetected_t<Constraints<>, ConstraintsDetector, T>;
 
        template<typename T>
        struct ExtractConstraintFields;
 
        template<int... Fields>
        struct ExtractConstraintFields<UniqueSubset<Fields...>>
        {
            QString operator() (const CachedFieldsData& data) const noexcept
            {
                return "UNIQUE (" + QStringList { data.Fields_.value (Fields)... }.join (", ") + ")";
            }
        };
 
        template<int... Fields>
        struct ExtractConstraintFields<PrimaryKey<Fields...>>
        {
            QString operator() (const CachedFieldsData& data) const noexcept
            {
                return "PRIMARY KEY (" + QStringList { data.Fields_.value (Fields)... }.join (", ") + ")";
            }
        };
 
        template<typename... Args>
        QStringList GetConstraintsStringList (Constraints<Args...>, const CachedFieldsData& data) noexcept
        {
            return { ExtractConstraintFields<Args> {} (data)... };
        }
 
        template<typename ImplFactory, typename T, size_t... Indices>
        QList<QString> GetTypes (std::index_sequence<Indices...>) noexcept
        {
            return { Type2Name<ImplFactory, ValueAtC_t<T, Indices>> {} ()... };
        }
 
        template<typename ImplFactory, typename T>
        QString AdaptCreateTable (const CachedFieldsData& data) noexcept
        {
            const auto& types = GetTypes<ImplFactory, T> (SeqIndices<T>);
 
            const auto& constraints = GetConstraintsStringList (ConstraintsType<T> {}, data);
            const auto& constraintsStr = constraints.isEmpty () ?
                    QString {} :
                    (", " + constraints.join (", "));
 
            const auto& statements = Util::ZipWith<QList> (types, data.Fields_,
                    [] (const QString& type, const QString& field) { return field + " " + type; });
            return "CREATE TABLE " +
                    data.Table_ +
                    " (" +
                    statements.join (", ") +
                    constraintsStr +
                    ");";
        }
    }
 
    template<auto... Ptrs>
    InsertAction::Replace::FieldsType<Ptrs...>::operator InsertAction::Replace () const
    {
        return { { detail::BuildCachedFieldsData<MemberPtrStruct_t<Ptrs>> ().Fields_.value (detail::FieldIndex<Ptrs> ())... } };
    }
 
    template<typename Seq>
    InsertAction::Replace::PKeyType<Seq>::operator InsertAction::Replace () const
    {
        static_assert (detail::HasPKey<Seq>, "Sequence does not have any primary keys");
        return { { detail::GetFieldName<Seq, detail::FindPKey<Seq>::result_type::value> () } };
    }
 
    template<typename T>
    struct ObjectInfo
    {
        detail::AdaptInsert<T> Insert;
        detail::AdaptUpdate<T> Update;
        detail::AdaptDelete<T> Delete;
 
        detail::SelectWrapper<T, detail::SelectBehaviour::Some> Select;
        detail::SelectWrapper<T, detail::SelectBehaviour::One> SelectOne;
        detail::DeleteByFieldsWrapper<T> DeleteBy;
 
        ObjectInfo (const ObjectInfo<T>&) = delete;
        ObjectInfo (ObjectInfo<T>&&) = default;
 
        using ObjectType_t = T;
    };
 
    template<typename T, typename ImplFactory = detail::SQLite::ImplFactory>
    ObjectInfo<T> Adapt (const QSqlDatabase& db)
    {
        const auto& cachedData = detail::BuildCachedFieldsData<T> ();
 
        if (!db.tables ().contains (cachedData.Table_, Qt::CaseInsensitive))
            RunTextQuery (db, detail::AdaptCreateTable<ImplFactory, T> (cachedData));
 
        ImplFactory factory;
 
        return
        {
            { db, cachedData, factory },
            { db, cachedData },
            { db, cachedData },
 
            { db, cachedData, factory },
            { db, cachedData, factory },
            { db, cachedData }
        };
    }
 
    template<typename T>
    using ObjectInfo_ptr = std::shared_ptr<ObjectInfo<T>>;
 
    template<typename T, typename ImplFactory = SQLiteImplFactory>
    ObjectInfo_ptr<T> AdaptPtr (const QSqlDatabase& db)
    {
        return std::make_shared<ObjectInfo<T>> (Adapt<T, ImplFactory> (db));
    }
 
    namespace detail
    {
        template<size_t Idx, typename Tuple>
        using UnderlyingObject_t = typename std::decay_t<std::tuple_element_t<Idx, Tuple>>::element_type::ObjectType_t;
 
        template<typename ImplFactory, typename Tuple, size_t... Idxs>
        void AdaptPtrs (const QSqlDatabase& db, Tuple& tuple, std::index_sequence<Idxs...>)
        {
            ((std::get<Idxs> (tuple) = AdaptPtr<UnderlyingObject_t<Idxs, Tuple>, ImplFactory> (db)), ...);
        }
    }
 
    template<typename ImplFactory, typename Tuple>
    void AdaptPtrs (const QSqlDatabase& db, Tuple& tuple)
    {
        detail::AdaptPtrs<ImplFactory> (db, tuple, std::make_index_sequence<std::tuple_size_v<Tuple>> {});
    }
}
}
}