Trident Transactional State

[Rajat Gangwar <ra...@gmail.com>]

Hi,

I just started working on Storm, so please forgive if my question is too
trivial. :D

This doc <http://storm.apache.org/releases/1.0.2/Trident-state.html>
clearly explain the intricacies needed for achieving exactly-once semantics.

But then at the end it says *"The nice thing about Trident is that it
internalizes all the fault-tolerance logic within the State – as a user you
don't have to deal with comparing txids, storing multiple values in the
database, or anything like that."*

Does that mean I don't have to store txn-id in my database along with the
data I am persisting ?
If yes, then how does Trident make sure that same row is not updated twice
when DB update happened but acknowledgement is not received ?

Thanks,
Rajat