currval of sequence "follow_id_seq" is not yet defined in this session

postgresql上使用

select currval('follow_id_seq');

报错：

currval of sequence "follow_id_seq" is not yet defined in this session

查阅参考资料，发现错误原因是要查当前值，必须先取一次next：执行以下语句，执行成功：

dbname=# select nextval('follow_id_seq');
 nextval 
---------
    5347
(1 row)

dbname=# select currval('follow_id_seq');
 currval 
---------
    5347
(1 row)

http://sunboyyyl.blog.163.com/blog/static/224738120099135521859/