Create ObjectIds in PostGres following the MongoDB semantics. Very similar to the Instagram approach linked below. http://docs.mongodb.org/manual/reference/object-id/ http://instagram-engineering.tumblr.com/post/10853187575/sharding-ids-at-instagram

Generate Mongo Object ID in PostGres

CREATE OR REPLACE FUNCTION generate_object_id() RETURNS varchar AS $$
    DECLARE
        time_component bigint;
        machine_id int := FLOOR(random() * 16777215);
        process_id int;
        seq_id bigint := FLOOR(random() * 16777215);
        result varchar:= '';
    BEGIN
        SELECT FLOOR(EXTRACT(EPOCH FROM clock_timestamp())) INTO time_component;
        SELECT pg_backend_pid() INTO process_id;

        result := result || lpad(to_hex(time_component), 8, '0');
        result := result || lpad(to_hex(machine_id), 6, '0');
        result := result || lpad(to_hex(process_id), 4, '0');
        result := result || lpad(to_hex(seq_id), 6, '0');
        RETURN result;
    END;
$$ LANGUAGE PLPGSQL;

Example Use:

CREATE TABLE IF NOT EXISTS users
(
  id varchar(24) NOT NULL default generate_object_id(),
	name varchar(255) NOT NULL,
);