CREATE SEQUENCE public.global_id_seq;
ALTER SEQUENCE public.global_id_seq OWNER TO postgres;

CREATE OR REPLACE FUNCTION public.id_generator()
    RETURNS bigint
    LANGUAGE 'plpgsql'
AS $BODY$
DECLARE
    our_epoch bigint := 1314220021721;
    seq_id bigint;
    now_millis bigint;
    -- the id of this DB shard, must be set for each
    -- schema shard you have - you could pass this as a parameter too
    shard_id int := 1;
    result bigint:= 0;
BEGIN
    SELECT nextval('public.global_id_seq') % 1024 INTO seq_id;

    SELECT FLOOR(EXTRACT(EPOCH FROM clock_timestamp()) * 1000) INTO now_millis;
    result := (now_millis - our_epoch) << 23;
    result := result | (shard_id << 10);
    result := result | (seq_id);
	return result;
END;
$BODY$;

ALTER FUNCTION public.id_generator() OWNER TO postgres;

create schema shard_1
create table users(
  id bigint not null default id_generator(),
  email varchar(255) not null unique,
  first varchar(50),
  last varchar(50)
);

-- select id_generator();