relx::connection::AsyncStreamingResultSet< DataSource > Class Template Reference

Async streaming result set that yields rows asynchronously. More...

#include <relx/connection/postgresql_async_streaming_source.hpp>

Classes
class	async_streaming_iterator
	Iterator that reads data on demand asynchronously. More...

Public Member Functions
	AsyncStreamingResultSet (DataSource source)
	~AsyncStreamingResultSet ()
	Destructor that ensures cleanup when result set goes out of scope.
	AsyncStreamingResultSet (const AsyncStreamingResultSet &)=delete
AsyncStreamingResultSet &	operator= (const AsyncStreamingResultSet &)=delete
	AsyncStreamingResultSet (AsyncStreamingResultSet &&other) noexcept
AsyncStreamingResultSet &	operator= (AsyncStreamingResultSet &&other) noexcept
async_streaming_iterator	begin ()
	Begin async iteration.
async_streaming_iterator	end ()
	End marker for async iteration.
template<typename Func >
boost::asio::awaitable< void >	for_each (Func &&func)
	Process all rows with an async callback.
boost::asio::awaitable< void >	cleanup ()
	Explicitly cleanup the streaming source.
boost::asio::awaitable< void >	auto_reset_connection_state ()
	Internal method to automatically reset connection state (called only once)

Detailed Description

template<typename DataSource>
class relx::connection::AsyncStreamingResultSet< DataSource >

Async streaming result set that yields rows asynchronously.

Definition at line 126 of file postgresql_async_streaming_source.hpp.

Constructor & Destructor Documentation

AsyncStreamingResultSet() [1/3]

template<typename DataSource >

relx::connection::AsyncStreamingResultSet< DataSource >::AsyncStreamingResultSet ( DataSource  source )

inline

Definition at line 163 of file postgresql_async_streaming_source.hpp.

~AsyncStreamingResultSet()

template<typename DataSource >

relx::connection::AsyncStreamingResultSet< DataSource >::~AsyncStreamingResultSet ( )

inline

Destructor that ensures cleanup when result set goes out of scope.

Definition at line 166 of file postgresql_async_streaming_source.hpp.

AsyncStreamingResultSet() [2/3]

template<typename DataSource >

relx::connection::AsyncStreamingResultSet< DataSource >::AsyncStreamingResultSet ( const AsyncStreamingResultSet< DataSource > &  )

delete

AsyncStreamingResultSet() [3/3]

template<typename DataSource >

relx::connection::AsyncStreamingResultSet< DataSource >::AsyncStreamingResultSet ( AsyncStreamingResultSet< DataSource > &&  other )

inlinenoexcept

Definition at line 182 of file postgresql_async_streaming_source.hpp.

Member Function Documentation

auto_reset_connection_state()

template<typename DataSource >

boost::asio::awaitable< void > relx::connection::AsyncStreamingResultSet< DataSource >::auto_reset_connection_state ( )

inline

Internal method to automatically reset connection state (called only once)

Returns

Awaitable that resolves when reset is complete

Definition at line 344 of file postgresql_async_streaming_source.hpp.

begin()

template<typename DataSource >

async_streaming_iterator relx::connection::AsyncStreamingResultSet< DataSource >::begin ( )

inline

Begin async iteration.

Definition at line 205 of file postgresql_async_streaming_source.hpp.

cleanup()

template<typename DataSource >

boost::asio::awaitable< void > relx::connection::AsyncStreamingResultSet< DataSource >::cleanup ( )

inline

Explicitly cleanup the streaming source.

Returns

Awaitable that resolves when cleanup is complete

Definition at line 337 of file postgresql_async_streaming_source.hpp.

end()

template<typename DataSource >

async_streaming_iterator relx::connection::AsyncStreamingResultSet< DataSource >::end ( )

inline

End marker for async iteration.

Definition at line 208 of file postgresql_async_streaming_source.hpp.

for_each()

template<typename DataSource >

template<typename Func >

boost::asio::awaitable< void > relx::connection::AsyncStreamingResultSet< DataSource >::for_each ( Func &&  func )

inline

Process all rows with an async callback.

This method is the recommended way to iterate over async streaming results.

Why for_each is needed instead of range-based for loops:

Async streaming cannot use standard C++ range-based for loops because:

1. Each row fetch is an async operation that must be awaited
2. Range-based for loops expect synchronous iterators with immediate operator++()
3. The async advance() method returns boost::asio::awaitable<void>

Usage Examples:

// Basic processing (void return):
co_await result.for_each([](const auto& row) {
    auto id = row.get<int>("id");
    std::cout << "Processing ID: " << id << std::endl;
});
 
// Early termination (bool return - true breaks):
co_await result.for_each([](const auto& row) -> bool {
    auto id = row.get<int>("id");
    std::cout << "Processing ID: " << id << std::endl;
    return id > 1000; // Break when ID exceeds 1000
});
 
// Async processing:
co_await result.for_each([](const auto& row) -> boost::asio::awaitable<void> {
    auto id = row.get<int>("id");
    co_await some_async_operation(id);
});
 
// Async processing with early termination:
co_await result.for_each([](const auto& row) -> boost::asio::awaitable<bool> {
    auto id = row.get<int>("id");
    co_await some_async_operation(id);
    return should_stop_processing(id); // Return true to break
});

Manual Iteration (for finer-grained control):

If you need more control over the iteration process, you can use manual iteration:

auto it = result.begin();
co_await it.advance(); // Get first row
 
while (!it.is_at_end()) {
    const auto& row = *it;
 
    // Your custom processing logic here
    auto id = row.get<int>("id");
 
    // Custom break conditions
    if (some_complex_condition(row)) {
        break;
    }
 
    // Custom error handling
    try {
        co_await it.advance();
    } catch (const std::exception& e) {
        // Handle iteration errors
        break;
    }
}

Template Parameters

Func	Function type - can be sync/async, void/bool return

Parameters

func

Callback function to process each row Signature: void(const LazyRow&) - Process each row Signature: bool(const LazyRow&) - Process each row, return true to break Signature: boost::asio::awaitable<void>(const LazyRow&) - Async processing Signature: boost::asio::awaitable<bool>(const LazyRow&) - Async processing with early termination

Returns

Awaitable that resolves when all rows are processed or early termination occurs

Definition at line 286 of file postgresql_async_streaming_source.hpp.

operator=() [1/2]

template<typename DataSource >

AsyncStreamingResultSet & relx::connection::AsyncStreamingResultSet< DataSource >::operator= ( AsyncStreamingResultSet< DataSource > &&  other )

inlinenoexcept

Definition at line 187 of file postgresql_async_streaming_source.hpp.

operator=() [2/2]

template<typename DataSource >

AsyncStreamingResultSet & relx::connection::AsyncStreamingResultSet< DataSource >::operator= ( const AsyncStreamingResultSet< DataSource > &  )

delete

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The documentation for this class was generated from the following file:

• relx/connection/postgresql_async_streaming_source.hpp