snowflake in postgresql

gistfile1.txt

CREATE SEQUENCE IF NOT EXISTS public.global_id_sequence;

CREATE OR REPLACE FUNCTION id_generator()
    RETURNS bigint
    LANGUAGE 'plpgsql'
AS $BODY$
DECLARE
    epoch BIGINT := 1688745600000;
    seq_id BIGINT;
    now_millis BIGINT;
    shard_id INT := 0; -- before sharding, all use 0 as shard id
    result bigint:= 0;
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);
   	return result;
END;
$BODY$;

ALTER FUNCTION public.id_generator() OWNER TO yochat;
alter sequence public.global_id_sequence owner to yochat;