8 byte pretty much unique ID generator

generator.st

"http://instagram-engineering.tumblr.com/post/10853187575/sharding-ids-at-instagram"

| epoch generator ids runLength shardId seqId|
epoch := '01-01-2014' asDateAndTime asUnixTime. "1388545200"
generator := [:seed1 :seed2 |
	| id |
	id := (DateAndTime now asUnixTime - epoch) bitShift: 64-41. 
	id := id bitOr: (seed1 bitShift: (64-41-13)).
	id := id bitOr: seed2 ].

shardId := 1.
seqId := 1.

ids := IdentitySet new.
runLength := 1000000.
Transcript 
	show: 'Consecutive sample of ';
	show: runLength printString;
	cr; 
	show: (
	Time millisecondsToRun: [
		runLength timesRepeat: [ 
			ids add: (generator value: shardId value: (seqId \\ 1024) ) ]]) printString,'ms';
	tab;
	show: 'Unique IDs: ', ids size printString .

idgenerator.sql

CREATE OR REPLACE FUNCTION insta5.next_id(OUT result bigint) AS $$
DECLARE
    our_epoch bigint := 1314220021721;
    seq_id bigint;
    now_millis bigint;
    shard_id int := 5;
BEGIN
    SELECT nextval('insta5.table_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);
END;
$$ LANGUAGE PLPGSQL;