PGO

PG...Oh god not nother Postgres client in Erlang...

Why

• No message passing. Clients checkout the socket and use it directly.
• Binary protocol with input oids cached.
• Simple and direct. Tries to limit runtime options as much as possible.
• Instrumented with OpenCensus
• Mix apps currently too hard to use in a Rebar3 project.

Requirements

Erlang/OTP 20 and above. Queries will not run on OTP 19 and below because some of the required functions are defined only in OTP 20+.

This project also depends on merl which is built in by default as of OTP 18.

Use

Pools defined in the pgo application's environment will be started on boot. You can also add pools dynamically with pgo:start_pool/3.

To try pgo simply modify config/example.config by replacing the host, database, user and password values for the database you wish to connect to:

[
  {pgo, [{pools, [{default, [{size, 10},
                             {host, "127.0.0.1"},
                             {database, "test"},
                             {user, "test"}]}]}]}
].

default is the name of the pool, size is the number of connections to create for the pool.

Then start a shell with rebar3, it will boot the applications which will start the pool automatically:

$ rebar3 shell 

1> pgo:query("select 1").
#{command => select, num_rows => 1, rows => [{1}]}

Running Tests

Pool functionality is tested with common test suites:

$ rebar3 ct

Postgres query functionality is tested with eunit, create user test and database test:

$ rebar3 eunit

Acknowledgements

Much is owed to https://github.com/semiocast/pgsql (especially for protocol step logic) and https://github.com/epgsql/epgsql/ (especially for some decoding logic).

The pool implementation is owed to James Fish's found in db_connectionPR 108. While db_connection and postgrex as a whole were both used as inspiration as well.