Erlang PostgreSQL Database Client Pool for epgsql

Configure application env like so:

    application:start(epgsql),
    application:set_env(epgsql_connpool, pools, 
        [ {maindb, 
                [
                    {host,      "127.0.0.1"}, 
                    {username,  "postgres"}, 
                    {password,  ""}, 
                    {size,      10}, 
                    {opts, [
                            {timeout,  5000}, 
                            {database, "my_database"}
                           ]}
                ]
          }
        ]
    ),
    application:start(epgsql_connpool).

And to make queries:
    
    {atomic, NumRows} = 
    epgsql_connpool:transaction( maindb, fun(Db) ->
        Sql = "SELECT count(*) FROM my_table WHERE id = $1;"
        {ok, _, [{Ret}]} = pgsql:equery(Db, Sql, [123]),
        Ret
    end).

With transaction(), all queries made within the fun are surrounded by a 
BEGIN/COMMIT/ROLLBACK.

With dirty(), the statements are run as-is, not in a transaction.