DuckPG - DuckDB extension with postgresql wire protocol enabled

Changelog for this fork

Compared to the version of the forked one,

std::format is not supported until C++23, so currently, std::ostringstream is used as a workaround.
In /src/duckpg/duckdb_pgwire_extension.cpp, the line 125 is changed to

  stmt.fields.emplace_back(pgwire::FieldDescription{name, oid});

Theory related to this:

struct S {
  int a;
  int b;
}

int main() {
  S s1{2, 3}; // aggregate initialization
  S s2; // default initialization with a and b set to 0;
  // when you call it like this
  std::vector<S> ss;
  ss.emplace_back(2, 3); // This fails as there isn't an allocator for S that expects two int initializers (aggregate initialization is just a convenient syntax & semantic)
  ss.emplace_back(); // This works though because the allocator picked for S is the compiler's default constructor
  ss.emplace_back(S{2,3}); // This works though because the allocator picked for S is the compiler's default copy constructor
}

The FieldDescription struct in the repo does not work because it runs into the same situation.

Adding an explicit constructor would work:

struct S {
  int a;
  int b;

  S(int a, int b): a { a }, b { b } {}
}

int main() {
  // when you call it like this
  std::vector<S> ss;
  ss.emplace_back(2, 3); // This now succeeds because there's an allocator for two int initializer
}

Disclaimer: just my theory, I haven't dug into how Allocator in C++ works though

Introduction

This extension is used for experimentation of adding PostgreSQL wire protocol to the DuckDB ecosystem through an extension named duckdb_pgwire.

The PostgreSQL wire protocol is implemented in standalone component/library named pgwire that heavily inspired by https://github.com/returnString/convergence and https://github.com/jeroenrinzema/psql-wire.

Milestone

Building and Running

Clone the repository along with the submodule with :

git clone --recurse-submodules https://github.com/Huy-DNA/duckpg.git

Build the extension

make -j$(nproc)

Open the duckdb shell or through any duckdb embedded client and load the extension

# example usage with cli
cd build/release
# somehow still require manual loading of the extension even already built onto the duckdb shell/cli
./duckdb -cmd 'load duckdb_pgwire'

And on the other terminal you can use psql and connect to port 15432 with ssl disabled

psql 'postgresql://localhost:15432/main' -c 'select * from generate_series(0, 100)'

Or you can use the postgresql driver in your language choice. You can also run sample client in golang provided in this repo

# from the root directory
cd client/go/cmd/simple
go build && ./simple