Postgresql Unique K-ordered 64-bit Integer Generator

Postgresql function - http://www.wekeroad.com/2014/05/29/a-better-id-generator-for-postgresql/.

Gave this function an additional spin by removing separate schema creation, so it could be used in the public schema:

CREATE SEQUENCE global_id_sequence;

CREATE OR REPLACE FUNCTION id_generator(OUT result bigint) AS $$
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;
BEGIN
    SELECT nextval('global_id_sequence') % 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);
END;
$$ LANGUAGE PLPGSQL;

Usage:

CREATE TABLE test_table
(
    id bigint NOT NULL DEFAULT id_generator(),
    name text NOT NULL,
    CONSTRAINT test_table_pkey PRIMARY KEY (id)
)
WITH (
    OIDS=FALSE
);