Sorry, I  was not going to send the 'pull request'. 
It's my using code.

FYI)

| id  | text | update_at |
| ------------- | ------------- | ------------- |
| 1 | aaa | 2014-02-20 00:00:00 |
| 2 | bbb | 2014-02-20 00:00:00 |
| 3 | ccc | 2014-02-20 00:00:01 (x) |
| 4 | ddd | 2014-02-20 00:00:01 |
| 5 | eee | 2014-02-20 00:00:01 |
| 6 | fff | 2014-02-20 00:00:02 |

If I set the "limit" equals 3, I will get "id:3" as a last record.
And its "update_at" is "2014-02-20 00:00:01".

Next time, it will start from "id:6". I have missed "id:4" and "id:5".
So I have removed "limit". It's very easy choice. :)