sharded_id.sql

DELIMITER ;;

DROP FUNCTION IF EXISTS shard_nextval;;
CREATE FUNCTION shard_nextval() RETURNS BIGINT
BEGIN
    INSERT INTO shard_seq VALUES (NULL);
    SET @R_ObjectId_val = LAST_INSERT_ID();
    DELETE FROM shard_seq;
    RETURN @R_ObjectId_val;
END;;

DROP FUNCTION IF EXISTS next_id;;
CREATE FUNCTION next_id() RETURNS BIGINT
BEGIN
    DECLARE our_epoch BIGINT DEFAULT 1325419260000;
    DECLARE seq_id BIGINT;
    DECLARE now_millis BIGINT;
    DECLARE shard_id INT DEFAULT 1;
    DECLARE result BIGINT UNSIGNED;

    SELECT MOD(shard_nextval(), 1024) INTO seq_id;
    SELECT ROUND(UNIX_TIMESTAMP(CURTIME(4)) * 1000) INTO now_millis;
    
    SET result := (now_millis - our_epoch) << 23;
    SET result := result | (shard_id << 10);
    SET result := result | (seq_id);
    RETURN result;
END;;

DELIMITER ;