Postgres by dietmarkuehl · Pull Request #57 · bemanproject/net

dietmarkuehl · 2026-04-27T22:52:47Z

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Copilot

Pull request overview

Adds initial PostgreSQL (libpq) examples and the plumbing needed to integrate a “poll for readiness” operation into beman.net’s execution-based async model.

Changes:

Introduces async_poll sender/CPO and a context_base::poll() virtual to support readiness waiting.
Updates io_context::async_run() scheduling strategy and adds small utility changes (e.g., make_socket(fd), event_type stream output).
Adds Postgres example programs + build-system detection/linkage for libpq.

Reviewed changes

Copilot reviewed 15 out of 15 changed files in this pull request and generated 16 comments.

Show a summary per file

File	Description
include/beman/net/detail/scope.hpp	Modifies `scope::run()` behavior (currently stops driving `io_context`).
include/beman/net/detail/poll_context.hpp	Adds `poll()` implementation and a temporary `<iostream>` include.
include/beman/net/detail/operations.hpp	Adds `async_poll`/`poll_desc` sender description.
include/beman/net/detail/io_context_scheduler.hpp	Exposes `poll()` forwarding on the scheduler.
include/beman/net/detail/io_context.hpp	Adds `make_socket(fd)` and rewrites `async_run()` to use an env scheduler.
include/beman/net/detail/event_type.hpp	Adds `operator<<` for `event_type`.
include/beman/net/detail/context_base.hpp	Adds `poll_operation` type and new pure-virtual `poll()` method.
include/beman/net/detail/basic_socket.hpp	Minor member formatting / TODO comment.
examples/postgres.cpp	New example demonstrating async libpq usage with beman execution/net.
examples/populate-postgres.cpp	New helper example to populate the Postgres table.
examples/postgres.txt	New setup instructions for Postgres role/db/table and `.pgpass`.
examples/empty.cpp	Temporarily disables prior example code behind `#if 0`.
examples/CMakeLists.txt	Conditionally adds Postgres examples and links against `pq`.
CMakeLists.txt	Adds rudimentary `libpq` detection and gates examples subdir.
Makefile	Adds `clang-format` alias target.

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Copilot · 2026-04-27T23:03:02Z

+set(POSTGRESROOT /Library/PostgreSQL/18)
+check_library_exists(pq PQsocket ${POSTGRESROOT}/lib HAS_POSTGRES)


POSTGRESROOT is hard-coded to /Library/PostgreSQL/18, which is platform- and install-specific. Make this configurable (CACHE PATH) and/or use find_package(PostgreSQL) / pkg-config to locate libpq in a cross-platform way; otherwise the build system will behave unexpectedly on non-macOS or different Postgres installs.

Suggested change

set(POSTGRESROOT /Library/PostgreSQL/18)

check_library_exists(pq PQsocket ${POSTGRESROOT}/lib HAS_POSTGRES)

find_package(PostgreSQL QUIET)

if(PostgreSQL_FOUND)

set(HAS_POSTGRES TRUE)

else()

set(HAS_POSTGRES FALSE)

endif()

Copilot · 2026-04-27T23:03:02Z

 auto main() -> int {
+    std::cout << std::unitbuf << "hello world\n";
+#if 0
    net::io_context        context;
    net::ip::tcp::endpoint ep(net::ip::address_v4::any(), 12345);
    net::ip::tcp::acceptor server(context, ep);

    ex::sync_wait(net::async_accept(server));

    context.run();
+#endif


This example now prints a message and compiles out the networking logic with #if 0, which makes the empty example effectively a no-op. If this is temporary debugging, consider removing it before merging or gating it behind an explicit build option.

Copilot · 2026-04-27T23:03:02Z

+        //-dk:TODO return beman::execution::when_all(this->_counting_scope.join(), this->_io_context.async_run());
+        return beman::execution::when_all(this->_counting_scope.join());


scope::run() no longer runs the underlying io_context (it only joins the counting scope). Any I/O scheduled in this scope will never make progress unless callers separately run the io_context, which breaks the scope abstraction. Restore when_all(join(), _io_context.async_run()) (or provide an equivalent that ensures the io_context is driven while the scope is active).

Suggested change

//-dk:TODO return beman::execution::when_all(this->_counting_scope.join(), this->_io_context.async_run());

return beman::execution::when_all(this->_counting_scope.join());

return beman::execution::when_all(this->_counting_scope.join(), this->_io_context.async_run());

Copilot · 2026-04-27T23:03:04Z

+        std::ostringstream ins;
+        ins << "insert into messages (key, message) values(" << i << ", '" << message << "');";
+        std::cout << "inserting: " << ins.str() << '\n';
+        pq::result res(PQexec(conn.get(), ins.str().c_str()));


The SQL is built by concatenating message directly into a quoted literal. If message contains ' (or other special characters), the INSERT will fail (and it also models unsafe query construction). Use PQescapeLiteral / parameterized queries, or at minimum escape single quotes before building the statement.

Suggested change

std::ostringstream ins;

ins << "insert into messages (key, message) values(" << i << ", '" << message << "');";

std::cout << "inserting: " << ins.str() << '\n';

pq::result res(PQexec(conn.get(), ins.str().c_str()));

const char* const insert_sql = "insert into messages (key, message) values($1, $2);";

std::string key = std::to_string(i);

const char* const param_values[] = {key.c_str(), message.c_str()};

std::cout << "inserting: " << insert_sql << " [key=" << key << ", message=" << message << "]\n";

pq::result res(PQexecParams(conn.get(), insert_sql, 2, nullptr, param_values, nullptr, nullptr, 0));

Copilot · 2026-04-27T23:03:04Z

+inline std::ostream& operator<<(std::ostream& os, ::beman::net::event_type e) {
+    switch (e) {
+    default:
+        return os << "invalid(" << ::std::uint8_t(e) << ")";


Streaming std::uint8_t will typically print as a character, not a number. Cast to a larger integer type (e.g., unsigned int) before inserting into the stream so invalid(...) prints a readable numeric value.

Suggested change

return os << "invalid(" << ::std::uint8_t(e) << ")";

return os << "invalid(" << static_cast<unsigned int>(::std::uint8_t(e)) << ")";

Copilot · 2026-04-27T23:03:04Z

@@ -0,0 +1,54 @@
+// examples/postgres.cpp                                              -*-C++-*-


The file header comment says examples/postgres.cpp but this file is populate-postgres.cpp. Update the header to match the actual filename to avoid confusion when navigating or grepping.

Suggested change

// examples/postgres.cpp -*-C++-*-

// examples/populate-postgres.cpp -*-C++-*-

Copilot · 2026-04-27T23:03:05Z

+        auto set_value([[maybe_unused]] operation& o, auto&& receiver) {
+            ::beman::net::detail::ex::set_value(::std::move(receiver),
+                                                //::std::get<0>(o)
+                                                ::beman::net::event_type{});
+        }
+        auto get_scheduler() { return this->d_socket.get_scheduler(); }
+        auto submit([[maybe_unused]] auto* base) -> ::beman::net::detail::submit_result {
+            ::std::get<1>(*base) = this->d_mask;


poll_desc::set_value() always completes with event_type{} (i.e., none), ignoring the operation state. This makes async_poll() return the wrong result. Populate the operation with the observed events in the context implementation and return that stored value here (and avoid overwriting the same slot in submit() if it’s meant to hold the result).

Suggested change

auto set_value([[maybe_unused]] operation& o, auto&& receiver) {

::beman::net::detail::ex::set_value(::std::move(receiver),

//::std::get<0>(o)

::beman::net::event_type{});

}

auto get_scheduler() { return this->d_socket.get_scheduler(); }

auto submit([[maybe_unused]] auto* base) -> ::beman::net::detail::submit_result {

::std::get<1>(*base) = this->d_mask;

auto set_value(operation& o, auto&& receiver) {

::beman::net::detail::ex::set_value(::std::move(receiver), ::std::get<0>(o));

}

auto get_scheduler() { return this->d_socket.get_scheduler(); }

auto submit(auto* base) -> ::beman::net::detail::submit_result {

dietmarkuehl added 14 commits April 12, 2026 22:56

started on creating a postgres connection

3c81ece

saving current intermediate state

2030284

made some progress on the poll() implementation

d22b028

fixed the code to have poll() work for the poll_context

ecabdc4

making progress on querying the database in a nice way

5d39b75

added sync_run to run a local run_loop

aa136c7

trying to fix the run_loop existing on a timer

958a6ee

made some progress on fixing async_run

35bd5dc

a first cut at an asynchronous postgres demo

846e5e9

clang-format and some refinement to improve set_error completions

7e5a81c

added an initial print completions function

fdb0cf5

adding an example and building postgresql binding

31b182d

Merge branch 'main' into postgres

cd4444c

fixed the CMakeLists.txt to conditionally include postgres

1a57468

Copilot AI review requested due to automatic review settings April 27, 2026 22:52

dietmarkuehl requested a review from camio as a code owner April 27, 2026 22:52

Copilot started reviewing on behalf of dietmarkuehl April 27, 2026 22:56 View session

Copilot AI reviewed Apr 27, 2026

View reviewed changes

dietmarkuehl added 12 commits April 27, 2026 22:20

some clean-up and better prepration for the postgres presentation

a12f7f3

minor usability improvement for socket creation

4c80cb8

started adding a simple HTTP server

5c3aba0

added an async in-memory stream

f3ee267

added an in-memory stream

ae1058e

a bit more progress on the HTTP support

e8ce047

fixed noexcept of repeat_effect_until::connect

1ffb393

improved the completion signature of repeat_effect_until

56bf564

fixed when_any version to actually stop

e6e6db2

clang format

593329c

restored building examples

361c877

fix/work around issues located by CI

48857e6

dietmarkuehl merged commit bfaef11 into main May 4, 2026
37 checks passed

dietmarkuehl deleted the postgres branch May 4, 2026 21:11

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Postgres#57

Postgres#57
dietmarkuehl merged 26 commits intomainfrom
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		set(POSTGRESROOT /Library/PostgreSQL/18)
		check_library_exists(pq PQsocket ${POSTGRESROOT}/lib HAS_POSTGRES)

-set(POSTGRESROOT /Library/PostgreSQL/18)
-check_library_exists(pq PQsocket ${POSTGRESROOT}/lib HAS_POSTGRES)
+find_package(PostgreSQL QUIET)
+if(PostgreSQL_FOUND)
+    set(HAS_POSTGRES TRUE)
+else()
+    set(HAS_POSTGRES FALSE)
+endif()

		//-dk:TODO return beman::execution::when_all(this->_counting_scope.join(), this->_io_context.async_run());
		return beman::execution::when_all(this->_counting_scope.join());

-        std::ostringstream ins;
-        ins << "insert into messages (key, message) values(" << i << ", '" << message << "');";
-        std::cout << "inserting: " << ins.str() << '\n';
-        pq::result res(PQexec(conn.get(), ins.str().c_str()));
+        const char* const insert_sql = "insert into messages (key, message) values($1, $2);";
+        std::string       key         = std::to_string(i);
+        const char* const param_values[] = {key.c_str(), message.c_str()};
+        std::cout << "inserting: " << insert_sql << " [key=" << key << ", message=" << message << "]\n";
+        pq::result res(PQexecParams(conn.get(), insert_sql, 2, nullptr, param_values, nullptr, nullptr, 0));

	return os << "invalid(" << ::std::uint8_t(e) << ")";
	return os << "invalid(" << static_cast<unsigned int>(::std::uint8_t(e)) << ")";

	// examples/postgres.cpp --C++--
	// examples/populate-postgres.cpp --C++--

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Pull request overview

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