PostgreSQL Snowflake ID Generator Function

snowflake.sql

CREATE SEQUENCE IF NOT EXISTS public.global_id_sequence;

CREATE OR REPLACE FUNCTION id_generator(OUT result BIGINT) AS $$
DECLARE
    epoch BIGINT := 1610850820000;
    seq_id BIGINT;
    now_millis BIGINT;
    shard_id INT := 1;
BEGIN
    SELECT nextval('public.global_id_sequence') % 1024 INTO seq_id;

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