Função Postgresql – http://www.wekeroad.com/2014/05/29/a-better-id-generator-for-postgresql/ .
Deu a esta função um giro adicional removendo a criação de esquema separada, para que pudesse ser usada no esquema público:
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;
Uso:
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
);