DuRipeng

@jerryshao @mgaido91 would you please help to review, thanks!

> I am not familiar with this part, sorry @mgaido91 thx for the reply, can you introduce any reviewer familiar with?

@sopel39 Is this issue still available to get a ticket?

@Gabriel39 Maybe I can have a try, assign to me, PLZ?

I try this function in mysql client ``` mysql> select timediff(now(3), seconds_add(now(3), 3)); +------------------------------------------+ | timediff(now(3), seconds_add(now(3), 3)) | +------------------------------------------+ | -00:00:03 | +------------------------------------------+ ``` @Gabriel39 what you expect it...

@Gabriel39 Sorry for late report. Currently I am quite busy on other stuff, maybe we can change assignee if appropriate.

@andygrove @alamb can you please assign this issue to me? Thank you ❤️