array_types.hpp

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#pragma once
 
/// @file userver/storages/postgres/io/array_types.hpp
/// @brief I/O support for arrays (std::array, std::set, std::unordered_set,
/// std::vector)
/// @ingroup userver_postgres_parse_and_format
 
#include <array>
#include <iterator>
#include <set>
#include <unordered_set>
#include <vector>
 
#include <boost/pfr/core.hpp>
 
#include <userver/utils/impl/projecting_view.hpp>
 
#include <userver/storages/postgres/exceptions.hpp>
#include <userver/storages/postgres/io/buffer_io_base.hpp>
#include <userver/storages/postgres/io/field_buffer.hpp>
#include <userver/storages/postgres/io/row_types.hpp>
#include <userver/storages/postgres/io/traits.hpp>
#include <userver/storages/postgres/io/type_mapping.hpp>
#include <userver/storages/postgres/io/type_traits.hpp>
#include <userver/storages/postgres/io/user_types.hpp>
 
USERVER_NAMESPACE_BEGIN
 
namespace storages::postgres::io {
 
namespace traits {
 
template <typename Container>
struct HasFixedDimensions;
 
namespace detail {
 
template <typename Container>
struct HasFixedDimensionsImpl {
    using type = typename HasFixedDimensions<typename Container::value_type>::type;
};
 
}  // namespace detail
 
template <typename T>
struct HasFixedDimensions
    : std::conditional_t<
          meta::IsFixedSizeContainer<T>,
          detail::HasFixedDimensionsImpl<T>,
          BoolConstant<!kIsCompatibleContainer<T>>>::type {};
 
template <typename Container>
concept kHasFixedDimensions = HasFixedDimensions<Container>::value;  // NOLINT(readability-identifier-naming)
 
template <typename T>
struct FixedDimensions;
 
template <typename T>
struct DimensionSize : std::integral_constant<std::size_t, 0> {};
 
template <typename T, std::size_t N>
struct DimensionSize<std::array<T, N>> : std::integral_constant<std::size_t, N> {};
 
template <typename T>
inline constexpr std::size_t kDimensionSize = DimensionSize<T>::value;
 
namespace detail {
 
template <typename A, typename B>
struct JoinSequences;
 
template <typename T, T... U, T... V>
struct JoinSequences<std::integer_sequence<T, U...>, std::integer_sequence<T, V...>> {
    using type = std::integer_sequence<T, U..., V...>;
};
 
template <typename T>
struct FixedDimensionsImpl {
    static_assert(meta::IsFixedSizeContainer<T>, "Container must have fixed size");
    using type = typename JoinSequences<
        std::integer_sequence<std::size_t, kDimensionSize<T>>,
        typename FixedDimensions<typename T::value_type>::type>::type;
};
 
template <typename T>
struct FixedDimensionsNonContainer {
    using type = std::integer_sequence<std::size_t>;
};
 
}  // namespace detail
 
template <typename T, T... Values>
constexpr std::array<T, sizeof...(Values)> MakeArray(const std::integer_sequence<T, Values...>&) {
    return {Values...};
}
 
template <typename T>
struct FixedDimensions
    : std::conditional_t<
          meta::IsFixedSizeContainer<T>,
          detail::FixedDimensionsImpl<T>,
          detail::FixedDimensionsNonContainer<T>> {};
 
}  // namespace traits
 
namespace detail {
 
template <typename Element>
inline bool ForceInitElementMapping() {
    // composite types can be parsed without an explicit mapping
    if constexpr (io::traits::kIsMappedToPg<Element> || !io::traits::kIsCompositeType<Element>) {
        return ForceReference(CppToPg<Element>::init);
    } else {
        return true;
    }
}
 
template <typename Container>
struct ArrayBinaryParser : BufferParserBase<Container> {
    using BaseType = BufferParserBase<Container>;
    using ValueType = typename BaseType::ValueType;
    using ElementType = typename traits::ContainerFinalElement<Container>::type;
    constexpr static std::size_t dimensions = traits::kDimensionCount<Container>;
    using Dimensions = std::array<std::size_t, dimensions>;
    using DimensionIterator = typename Dimensions::iterator;
    using DimensionConstIterator = typename Dimensions::const_iterator;
    using ElementMapping = CppToPg<ElementType>;
 
    using BaseType::BaseType;
 
    void operator()(FieldBuffer buffer, const TypeBufferCategory& categories) {
        using std::swap;
 
        // read dimension count
        Integer dim_count{0};
        buffer.Read(dim_count, BufferCategory::kPlainBuffer);
        if (dim_count != static_cast<Integer>(dimensions) && ForceInitElementMapping<ElementType>()) {
            if (dim_count == 0) {
                ValueType empty{};
                swap(this->value, empty);
                return;
            }
            throw DimensionMismatch{};
        }
 
        // read flags
        Integer flags{0};
        buffer.Read(flags, BufferCategory::kPlainBuffer);
        // TODO check flags
 
        // read element oid
        Integer elem_oid{0};
        buffer.Read(elem_oid, BufferCategory::kPlainBuffer);
        // TODO check elem_oid
        auto elem_category = GetTypeBufferCategory(categories, elem_oid);
 
        // read dimension data
        Dimensions on_the_wire;
        for (auto& dim : on_the_wire) {
            Integer dim_val = 0;
            buffer.Read(dim_val, BufferCategory::kPlainBuffer);
            dim = dim_val;
 
            Integer lbound = 0;
            buffer.Read(lbound, BufferCategory::kPlainBuffer);
        }
        if (!CheckDimensions(on_the_wire)) {
            throw DimensionMismatch{};
        }
        // read elements
        ValueType tmp;
        ReadDimension(buffer, on_the_wire.begin(), elem_category, categories, tmp);
        swap(this->value, tmp);
    }
 
private:
    bool CheckDimensions(const Dimensions& dims) const {
        if constexpr (traits::kHasFixedDimensions<Container>) {
            return dims == traits::MakeArray(typename traits::FixedDimensions<Container>::type{});
        }
        return CheckDimensions<ValueType>(dims.begin());
    }
    template <typename Element>
    bool CheckDimensions([[maybe_unused]] DimensionConstIterator dim) const {
        if constexpr (meta::IsFixedSizeContainer<Element>) {
            // check subdimensions
            if (*dim != traits::kDimensionSize<Element>) {
                return false;
            }
            if constexpr (traits::kDimensionCount<Element> == 1) {
                return true;
            } else {
                return CheckDimensions<typename Element::value_type>(dim + 1);
            }
        } else if constexpr (traits::kIsCompatibleContainer<Element>) {
            if constexpr (traits::kDimensionCount<Element> == 1) {
                return true;
            } else {
                return CheckDimensions<typename Element::value_type>(dim + 1);
            }
        }
        return true;
    }
 
    template <typename T>
    auto GetInserter(T& value) {
        return std::inserter(value, value.end());
    }
 
    template <typename T, std::size_t N>
    auto GetInserter(std::array<T, N>& array) {
        return array.begin();
    }
 
    template <typename Element>
    void ReadDimension(
        FieldBuffer& buffer,
        DimensionConstIterator dim,
        BufferCategory elem_category,
        const TypeBufferCategory& categories,
        Element& elem
    ) {
        if constexpr (traits::kIsCompatibleContainer<Element>) {
            if constexpr (traits::CanClear<Element>) {
                elem.clear();
            }
            if constexpr (traits::CanReserve<Element>) {
                elem.reserve(*dim);
            }
            auto it = GetInserter(elem);
            for (std::size_t i = 0; i < *dim; ++i) {
                typename Element::value_type val;
                if constexpr (1 < traits::kDimensionCount<Element>) {
                    // read subdimensions
                    ReadDimension(buffer, dim + 1, elem_category, categories, val);
                } else {
                    buffer.ReadRaw(val, categories, elem_category);
                }
                *it++ = std::move(val);
            }
        }
    }
 
    void ReadDimension(
        FieldBuffer& buffer,
        DimensionConstIterator dim,
        BufferCategory elem_category,
        const TypeBufferCategory& categories,
        std::vector<bool>& elem
    ) {
        elem.resize(*dim);
        // NOLINTNEXTLINE(readability-qualified-auto)
        auto value = elem.begin();
        for (std::size_t i = 0; i < *dim; ++i) {
            bool val{false};
            buffer.ReadRaw(val, categories, elem_category);
            *value++ = val;
        }
    }
};
 
template <typename Container>
struct ArrayBinaryFormatter : BufferFormatterBase<Container> {
    using BaseType = BufferFormatterBase<Container>;
    using ValueType = typename BaseType::ValueType;
    using ArrayMapping = CppToPg<Container>;
    using ElementType = typename traits::ContainerFinalElement<Container>::type;
    using ElementMapping = CppToPg<ElementType>;
    constexpr static std::size_t dimensions = traits::kDimensionCount<Container>;
    using Dimensions = std::array<std::size_t, dimensions>;
    using DimensionIterator = typename Dimensions::iterator;
    using DimensionConstIterator = typename Dimensions::const_iterator;
 
    using BaseType::BaseType;
 
    // top level container
    template <typename Buffer>
    void operator()(const UserTypes& types, Buffer& buffer, Oid replace_oid = kInvalidOid) const {
        auto elem_type_oid = ElementMapping::GetOid(types);
        if (replace_oid != kInvalidOid && replace_oid != ArrayMapping::GetOid(types)) {
            elem_type_oid = types.FindElementOid(replace_oid);
        }
 
        // Fast path for default-constructed vectors
        if (this->value.empty()) {
            io::WriteBuffer(types, buffer, static_cast<Integer>(0));  // dims
            io::WriteBuffer(types, buffer, static_cast<Integer>(0));  // flags
            io::WriteBuffer(types, buffer, static_cast<Integer>(elem_type_oid));
            return;
        }
 
        // Write number of dimensions
        io::WriteBuffer(types, buffer, static_cast<Integer>(dimensions));
        // Write flags
        io::WriteBuffer(types, buffer, static_cast<Integer>(0));
        // Write element type oid
        io::WriteBuffer(types, buffer, static_cast<Integer>(elem_type_oid));
        Dimensions dims = GetDimensions();
        // Write data per dimension
        WriteDimensionData(types, buffer, dims);
        // Write flat elements
        WriteData(types, dims.begin(), buffer, this->value);
    }
 
private:
    template <typename Element>
    void CalculateDimensions([[maybe_unused]] DimensionIterator dim, const Element& element) const {
        if constexpr (traits::kIsCompatibleContainer<Element>) {
            *dim = element.size();
            if (!element.empty()) {
                CalculateDimensions(dim + 1, *element.begin());
            }  // TODO else logic error?
        }
    }
    Dimensions GetDimensions() const {
        if constexpr (traits::kHasFixedDimensions<Container>) {
            return traits::MakeArray(typename traits::FixedDimensions<Container>::type{});
        } else {
            Dimensions dims{};
            CalculateDimensions(dims.begin(), this->value);
            return dims;
        }
    }
    template <typename Buffer>
    void WriteDimensionData(const UserTypes& types, Buffer& buffer, const Dimensions& dims) const {
        for (auto dim : dims) {
            io::WriteBuffer(types, buffer, static_cast<Integer>(dim));
            io::WriteBuffer(types, buffer, static_cast<Integer>(1));  // lbound
        }
    }
 
    template <typename Buffer, typename Element>
    void WriteData(const UserTypes& types, DimensionConstIterator dim, Buffer& buffer, const Element& element) const {
        if (*dim != element.size()) {
            throw InvalidDimensions{*dim, element.size()};
        }
        if constexpr (1 < traits::kDimensionCount<Element>) {
            // this is a (sub)dimension of array
            for (const auto& sub : element) {
                WriteData(types, dim + 1, buffer, sub);
            }
        } else {
            // this is the final dimension
            for (const auto& sub : element) {
                io::WriteRawBinary(types, buffer, sub);
            }
        }
    }
 
    template <typename Buffer>
    void WriteData(const UserTypes& types, DimensionConstIterator dim, Buffer& buffer, const std::vector<bool>& element)
        const {
        if (*dim != element.size()) {
            throw InvalidDimensions{*dim, element.size()};
        }
        for (const bool sub : element) {
            io::WriteRawBinary(types, buffer, sub);
        }
    }
};
 
template <typename Container, bool System>
struct ArrayPgOid {
    using Type = Container;
    using ElementType = typename traits::ContainerFinalElement<Container>::type;
    using ElementMapping = CppToPg<ElementType>;
    using Mapping = ArrayPgOid<Container, System>;
 
    static Oid GetOid(const UserTypes& types) { return ElementMapping::GetArrayOid(types); }
};
 
template <typename Container>
struct ArrayPgOid<Container, true> {
    using Type = Container;
    using ElementType = typename traits::ContainerFinalElement<Container>::type;
    using ElementMapping = CppToPg<ElementType>;
    using Mapping = ArrayPgOid<Container, true>;
 
    static constexpr Oid GetOid(const UserTypes&) { return static_cast<Oid>(ElementMapping::array_oid); }
};
 
template <typename Container>
constexpr bool IsElementMappedToSystem() {
    if constexpr (!traits::kIsCompatibleContainer<Container>) {
        return false;
    } else {
        return IsTypeMappedToSystem<typename traits::ContainerFinalElement<Container>::type>();
    }
}
 
template <typename Container>
concept EnableArrayParser =
    traits::kIsCompatibleContainer<Container> &&
    traits::HasParser<typename traits::ContainerFinalElement<Container>::type>;
 
template <typename Container>
concept EnableArrayFormatter =
    traits::kIsCompatibleContainer<Container> &&
    traits::HasFormatter<typename traits::ContainerFinalElement<Container>::type>;
 
}  // namespace detail
 
template <typename T>
requires(traits::detail::EnableContainerMapping<T>())
struct CppToPg<T> : detail::ArrayPgOid<T, detail::IsElementMappedToSystem<T>()> {};
 
template <typename T>
constexpr bool IsTypeMappedToSystemArray() {
    return traits::kIsMappedToPg<T> &&
           std::is_same<typename CppToPg<T>::Mapping, io::detail::ArrayPgOid<typename CppToPg<T>::Type, true>>::value;
}
 
namespace traits {
 
template <typename T>
requires(!detail::CustomParserDefined<T> && io::detail::EnableArrayParser<T>)
struct Input<T> {
    using type = io::detail::ArrayBinaryParser<T>;
};
 
template <typename T>
requires(!detail::CustomFormatterDefined<T> && io::detail::EnableArrayFormatter<T>)
struct Output<T> {
    using type = io::detail::ArrayBinaryFormatter<T>;
};
 
template <typename T>
struct ParserBufferCategory<io::detail::ArrayBinaryParser<T>>
    : std::integral_constant<BufferCategory, BufferCategory::kArrayBuffer> {};
 
// std::vector
template <typename... T>
struct IsCompatibleContainer<std::vector<T...>> : std::true_type {};
 
// std::array
template <typename T, std::size_t Size>
struct IsCompatibleContainer<std::array<T, Size>> : std::true_type {};
 
// std::set
template <typename... T>
struct IsCompatibleContainer<std::set<T...>> : std::true_type {};
 
// std::unordered_set
template <typename... T>
struct IsCompatibleContainer<std::unordered_set<T...>> : std::true_type {};
 
// TODO Add more containers
 
}  // namespace traits
 
namespace detail {
 
/// A helper data type to write a container chunk to postgresql array buffer
/// Mimics container interface (type aliases + begin/end)
template <typename Container>
class ContainerChunk {
public:
    static_assert(
        traits::IsCompatibleContainer<Container>{},
        "Only containers explicitly declared as compatible are supported"
    );
 
    using value_type = typename Container::value_type;
    using const_iterator_type = typename Container::const_iterator;
 
    ContainerChunk(const_iterator_type begin, std::size_t size)
        : begin_{begin},
          end_{std::next(begin, size)},
          size_{size}
    {}
 
    std::size_t size() const { return size_; }
    bool empty() const { return begin_ == end_; }
 
    const_iterator_type begin() const { return begin_; }
    const_iterator_type cbegin() const { return begin_; }
 
    const_iterator_type end() const { return end_; }
    const_iterator_type cend() const { return end_; }
 
private:
    const_iterator_type begin_;
    const_iterator_type end_;
    std::size_t size_;
};
 
/// Utility class to iterate chunks of input array
template <typename Container>
class ContainerSplitter {
public:
    static_assert(
        traits::IsCompatibleContainer<Container>{},
        "Only containers explicitly declared as compatible are supported"
    );
 
    using value_type = ContainerChunk<Container>;
 
    class ChunkIterator {
    public:
        using iterator_category = std::input_iterator_tag;
        using difference_type = std::ptrdiff_t;
        using value_type = ContainerChunk<Container>;
        using reference = value_type;
        using pointer = void;
 
        using UnderlyingIterator = typename Container::const_iterator;
        ChunkIterator(const Container& container, UnderlyingIterator current, std::size_t chunk_elements)
            : chunk_size_{chunk_elements},
              tail_size_{static_cast<size_t>(std::distance(current, container.end()))},
              current_{current}
        {}
 
        bool operator==(const ChunkIterator& rhs) const { return current_ == rhs.current_; }
 
        value_type operator*() const { return {current_, NextStep()}; }
 
        ChunkIterator& operator++() {
            auto step = NextStep();
            std::advance(current_, step);
            tail_size_ -= step;
            return *this;
        }
 
        ChunkIterator operator++(int) {
            ChunkIterator tmp{*this};
            ++(*this);
            return tmp;
        }
 
        std::size_t TailSize() const { return tail_size_; }
 
    private:
        std::size_t NextStep() const { return std::min(chunk_size_, tail_size_); }
 
        std::size_t chunk_size_;
        std::size_t tail_size_;
        UnderlyingIterator current_;
    };
 
    ContainerSplitter(const Container& container, std::size_t chunk_elements)
        : container_{container},
          chunk_size_{chunk_elements}
    {}
 
    std::size_t size() const {
        auto sz = container_.size();
        return sz / chunk_size_ + (sz % chunk_size_ ? 1 : 0);
    }
    bool empty() const { return container_.empty(); }
 
    ChunkIterator begin() const { return {container_, container_.begin(), chunk_size_}; }
 
    ChunkIterator end() const { return {container_, container_.end(), chunk_size_}; }
 
    std::size_t ChunkSize() const { return chunk_size_; }
    const Container& GetContainer() const { return container_; }
 
private:
    const Container& container_;
    const std::size_t chunk_size_;
};
 
template <
    typename Container,
    typename Seq = std::make_index_sequence<boost::pfr::tuple_size_v<typename Container::value_type>>>
struct ColumnsSplitterHelper;
 
/// Utility helper to iterate chunks of input array in column-wise way
template <typename Container, std::size_t... Indexes>
struct ColumnsSplitterHelper<Container, std::index_sequence<Indexes...>> final {
    static_assert(sizeof...(Indexes) > 0, "The aggregate having 0 fields doesn't make sense");
 
    template <std::size_t Index>
    struct FieldProjection {
        using RowType = typename Container::value_type;
        using FieldType = boost::pfr::tuple_element_t<Index, typename Container::value_type>;
 
        const FieldType& operator()(const RowType& value) const noexcept { return boost::pfr::get<Index>(value); }
    };
 
    template <std::size_t Index>
    using FieldView = USERVER_NAMESPACE::utils::impl::ProjectingView<const Container, FieldProjection<Index>>;
 
    template <typename Fn>
    static void Perform(const Container& container, std::size_t chunk_elements, const Fn& fn) {
        DoSplitByChunks(chunk_elements, fn, FieldView<Indexes>{container}...);
    }
 
private:
    template <typename Fn, typename... Views>
    static void DoSplitByChunks(std::size_t chunk_elements, const Fn& fn, const Views&... views) {
        DoIterateByChunks(fn, ContainerSplitter{views, chunk_elements}.begin()...);
    }
 
    template <typename Fn, typename FirstChunkIterator, typename... ChunkIterators>
    static void DoIterateByChunks(const Fn& fn, FirstChunkIterator first, ChunkIterators... chunks) {
        while (first.TailSize() > 0) {
            fn(*first, *chunks...);
 
            ++first;
            (++chunks, ...);
        }
    }
};
 
template <
    typename Container,
    typename Seq = std::make_index_sequence<boost::pfr::tuple_size_v<typename Container::value_type>>>
struct ColumnsDecomposerHelper;
 
template <typename Container, std::size_t... Indexes>
struct ColumnsDecomposerHelper<Container, std::index_sequence<Indexes...>> final {
    static_assert(sizeof...(Indexes) > 0, "The aggregate having 0 fields doesn't make sense");
 
    template <std::size_t Index>
    struct FieldProjection {
        using RowType = typename Container::value_type;
        using FieldType = boost::pfr::tuple_element_t<Index, typename Container::value_type>;
 
        const FieldType& operator()(const RowType& value) const noexcept { return boost::pfr::get<Index>(value); }
    };
 
    template <std::size_t Index>
    using FieldView = USERVER_NAMESPACE::utils::impl::ProjectingView<const Container, FieldProjection<Index>>;
 
    template <typename Fn>
    static auto Perform(const Container& container, const Fn& fn) {
        return fn(FieldView<Indexes>{container}...);
    }
};
 
/// Utility class to iterate chunks of input array in column-wise way
template <typename Container>
class ContainerByColumnsSplitter final {
public:
    ContainerByColumnsSplitter(const Container& container, std::size_t chunk_elements)
        : container_{container},
          chunk_elements_{chunk_elements}
    {}
 
    template <typename Fn>
    void Perform(const Fn& fn) {
        ColumnsSplitterHelper<Container>::Perform(container_, chunk_elements_, fn);
    }
 
private:
    const Container& container_;
    const std::size_t chunk_elements_;
};
 
template <typename Container>
class ContainerByColumnsDecomposer final {
public:
    ContainerByColumnsDecomposer(const Container& container)
        : container_(container)
    {}
 
    template <typename Fn>
    auto Perform(const Fn& fn) {
        return ColumnsDecomposerHelper<Container>::Perform(container_, fn);
    }
 
private:
    const Container& container_;
};
 
}  // namespace detail
 
namespace traits {
template <typename Container>
struct IsCompatibleContainer<io::detail::ContainerChunk<Container>> : IsCompatibleContainer<Container> {};
 
template <typename Container, typename Projection>
struct IsCompatibleContainer<USERVER_NAMESPACE::utils::impl::ProjectingView<const Container, Projection>>
    : IsCompatibleContainer<Container> {};
}  // namespace traits
 
template <typename Container>
detail::ContainerSplitter<Container> SplitContainer(const Container& container, std::size_t chunk_elements) {
    return {container, chunk_elements};
}
 
template <typename Container>
detail::ContainerByColumnsSplitter<Container> SplitContainerByColumns(
    const Container& container,
    std::size_t chunk_elements
) {
    return {container, chunk_elements};
}
 
template <typename Container>
detail::ContainerByColumnsDecomposer<Container> DecomposeContainerByColumns(const Container& container) {
    return {container};
}
 
}  // namespace storages::postgres::io
 
USERVER_NAMESPACE_END