parameter_store.hpp

Go to the documentation of this file.

#pragma once
 
/// @file userver/storages/postgres/parameter_store.hpp
/// @brief @copybrief storages::postgres::ParameterStore
 
#include <userver/storages/postgres/detail/query_parameters.hpp>
#include <userver/storages/postgres/io/type_traits.hpp>
#include <userver/storages/postgres/io/user_types.hpp>
#include <userver/utils/strong_typedef.hpp>
 
USERVER_NAMESPACE_BEGIN
 
namespace storages::postgres {
 
/// @ingroup userver_containers
///
/// @brief Class for dynamic PostgreSQL parameter list construction.
///
/// Typical use case for this container is to keep parameters around while the
/// query is being constructed on the fly:
/// @snippet storages/postgres/tests/interval_pgtest.cpp Parameters store sample
///
/// Note that storages::postgres::Cluster::Execute with explicitly provided
/// arguments works slightly faster:
/// @snippet storages/postgres/tests/landing_test.cpp Exec sample
class ParameterStore {
public:
    ParameterStore() = default;
    ParameterStore(const ParameterStore&) = delete;
    ParameterStore(ParameterStore&&) = default;
    ParameterStore& operator=(const ParameterStore&) = delete;
    ParameterStore& operator=(ParameterStore&&) = default;
 
    /// @brief Adds a parameter to the end of the parameter list.
    /// @note Currently only enums and built-in/system types are supported.
    template <typename T>
    ParameterStore& PushBack(const T& param) {
        static_assert(
            io::IsTypeMappedToSystem<T>() || io::IsTypeMappedToSystemArray<T>() ||
                (std::is_enum_v<T> && io::traits::kIsMappedToPg<T> &&
                 std::is_same_v<typename io::CppToPg<T>::Mapping, io::CppToUserPg<typename io::CppToPg<T>::Type>>),
            "Currently only built-in and enum types can be used in ParameterStore"
        );
        data_.Write(kNoUserTypes, param);
        return *this;
    }
 
    /// Returns whether the parameter list is empty.
    bool IsEmpty() const { return data_.Size() == 0; }
 
    /// Returns current size of the list.
    size_t Size() const { return data_.Size(); }
 
    /// @cond
    const detail::DynamicQueryParameters& GetInternalData() const { return data_; }
    /// @endcond
 
private:
    static UserTypes kNoUserTypes;
 
    detail::DynamicQueryParameters data_;
};
 
}  // namespace storages::postgres
 
USERVER_NAMESPACE_END