result_set.hpp

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#pragma once
 
/// @file userver/storages/sqlite/result_set.hpp
/// @copybrief storages::sqlite::ResultSet
 
#include <memory>
#include <optional>
#include <vector>
 
#include <userver/storages/sqlite/exceptions.hpp>
#include <userver/storages/sqlite/execution_result.hpp>
#include <userver/storages/sqlite/impl/extractor.hpp>
#include <userver/storages/sqlite/row_types.hpp>
#include <userver/storages/sqlite/sqlite_fwd.hpp>
 
USERVER_NAMESPACE_BEGIN
 
namespace storages::sqlite {
 
/// @brief A proxy for statement execution result.
///
/// This type can't be constructed in user code and is always retrieved from
/// storages::sqlite::Client, storages::sqlite::Transaction or storages::sqlite::Savepoint methods.
class ResultSet {
public:
    explicit ResultSet(impl::ResultWrapperPtr pimpl);
 
    ResultSet(const ResultSet& other) = delete;
    ResultSet(ResultSet&& other) noexcept;
    ResultSet& operator=(ResultSet&&) noexcept;
 
    ~ResultSet();
 
    /// @brief Parse statement result set as std::vector<T>.
    /// T is expected to be an aggregate of supported types.
    ///
    /// Throw exceptions on columns count mismatch or types mismatch.
    ///
    template <typename T>
    std::vector<T> AsVector() &&;
 
    /// @brief Parse statement result set as std::vector<T>.
    /// Result set is expected to have a single column, `T` is expected to be one
    /// of supported types.
    ///
    /// Throw exceptions on columns count not being equal to 1 or type mismatch.
    ///
    template <typename T>
    std::vector<T> AsVector(FieldTag) &&;
 
    /// @brief Parse statement result as T.
    /// Result set is expected to have a single row, `T` is expected to be an
    /// aggregate of supported types.
    ///
    /// Throw exceptions on columns count mismatch or types mismatch.
    /// throws if result set is empty or contains more than one row.
    ///
    template <typename T>
    T AsSingleRow() &&;
 
    /// @brief Parse statement result as T.
    /// Result set is expected to have a single row and a single column,
    /// `T` is expected to be one of supported types.
    ///
    /// Throw exceptions on columns count not being equal to 1 or type mismatch.
    /// throws if result set is empty of contains more than one row.
    ///
    template <typename T>
    T AsSingleField() &&;
 
    /// @brief Parse statement result as std::optional<T>.
    /// Result set is expected to have not more than one row,
    /// `T` is expected to be an aggregate of supported types.
    ///
    /// Throw exceptions on columns count mismatch or types mismatch.
    /// throws if result set contains more than one row.
    ///
    template <typename T>
    std::optional<T> AsOptionalSingleRow() &&;
 
    /// @brief Parse statement result as T.
    /// Result set is expected to have not more than one row,
    /// `T` is expected to be one of supported types.
    ///
    /// Throw exceptions on columns count not being equal to 1 or type mismatch.
    /// throws if result set contains more than one row.
    ///
    template <typename T>
    std::optional<T> AsOptionalSingleField() &&;
 
    /// @brief Get statement execution metadata.
    ExecutionResult AsExecutionResult() &&;
 
private:
    template <typename T>
    friend class CursorResultSet;
 
    void FetchAllResult(impl::ExtractorBase& extractor);
 
    bool FetchResult(impl::ExtractorBase& extractor, size_t batch_size);
 
    impl::ResultWrapperPtr pimpl_;
};
 
template <typename T>
std::vector<T> ResultSet::AsVector() && {
    impl::TypedExtractor<T, RowTag> extractor{*pimpl_};
    FetchAllResult(extractor);
    return extractor.ExtractData();
}
 
template <typename T>
std::vector<T> ResultSet::AsVector(FieldTag) && {
    impl::TypedExtractor<T, FieldTag> extractor{*pimpl_};
    FetchAllResult(extractor);
    return extractor.ExtractData();
}
 
template <typename T>
T ResultSet::AsSingleRow() && {
    auto optional_data = std::move(*this).AsOptionalSingleRow<T>();
    if (!optional_data.has_value()) {
        throw SQLiteException{"Result set is empty"};
    }
    return std::move(*optional_data);
}
 
template <typename T>
T ResultSet::AsSingleField() && {
    auto optional_data = std::move(*this).AsOptionalSingleField<T>();
    if (!optional_data.has_value()) {
        throw SQLiteException{"Result set is empty"};
    }
    return std::move(*optional_data);
}
 
template <typename T>
std::optional<T> ResultSet::AsOptionalSingleRow() && {
    auto rows = std::move(*this).AsVector<T>();
    if (rows.empty()) {
        return std::nullopt;
    }
    if (rows.size() > 1) {
        // TODO: Maybe better logging warning
        throw SQLiteException("Result set contains more than one row");
    }
    return {{std::move(rows.front())}};
}
 
template <typename T>
std::optional<T> ResultSet::AsOptionalSingleField() && {
    auto rows = std::move(*this).AsVector<T>(kFieldTag);
    if (rows.empty()) {
        return std::nullopt;
    }
    if (rows.size() > 1) {
        // TODO: Maybe better logging warning
        throw SQLiteException("Result set contains more than one row");
    }
    return {{std::move(rows.front())}};
}
 
}  // namespace storages::sqlite
 
USERVER_NAMESPACE_END