Erlang epgsql

Connect to CrateDB from Erlang using epgsql.

About

epgsql is the designated Erlang PostgreSQL client library.

Synopsis

rebar.config

{deps,
 [
  {epgsql, ".*", {git, "https://github.com/epgsql/epgsql.git", {tag, "4.8.0"}}}
 ]}.

epgsql_example.erl

-module(epgsql_example).
-export([start/0]).

start() ->
    {ok, C} = epgsql:connect(#{
        host => "localhost",
        username => "crate",
        password => "crate",
        port => 5432,
        ssl => false,
        timeout => 4000
    }),
    {ok, _, Result} = epgsql:squery(C, "SELECT mountain, height FROM sys.summits ORDER BY height DESC LIMIT 3"),
    io:fwrite("~p~n", [Result]),
    ok = epgsql:close(C),
    init:stop().

SSL connection

Start the Erlang SSL application, use the ssl and ssl_opts arguments on epgsql:connect, and replace username, password, and hostname with values matching your environment. Also use this variant to connect to CrateDB Cloud.

start() ->
    ssl:start(),
    {ok, C} = epgsql:connect(#{
        host => "testcluster.cratedb.net",
        username => "admin",
        password => "password",
        port => 5432,
        ssl => true,
        ssl_opts => [{verify, verify_none}],
        timeout => 4000
    }),

Example

Create the files rebar.config and epgsql_example.erl including the synopsis code shared above.

Start CrateDB using Docker or Podman, then invoke the example program.

docker run --rm --publish=5432:5432 docker.io/crate '-Cdiscovery.type=single-node'

rebar3 compile
erlc epgsql_example.erl
rebar3 shell --eval 'epgsql_example:start().'