RE: Global snapshots - Mailing list pgsql-hackers

Hi Andrey-san, all,

From: Andrey V. Lepikhov <a.lepikhov@postgrespro.ru>
> On 7/27/20 11:22 AM, tsunakawa.takay@fujitsu.com wrote:
> > Could you take a look at this patent?  I'm afraid this is the Clock-SI for MVCC.
> Microsoft holds this until 2031.  I couldn't find this with the keyword
> "Clock-SI.""
> >
> >
> > US8356007B2 - Distributed transaction management for database systems
> with multiversioning - Google Patents
> > https://patents.google.com/patent/US8356007
> >
> >
> > If it is, can we circumvent this patent?

> I haven't seen this patent before. This should be carefully studied.


I contacted 6 people individually, 3 holders of the patent and different 3 authors of the Clock-SI paper.  I got
repliesfrom two people.  (It's a regret I couldn't get a reply from the main author of Clock-SI paper.)
 

[Reply from the patent holder Per-Ake Larson]
--------------------------------------------------
Thanks for your interest in my patent. 

The answer to your question is: No, Clock-SI is not based on the patent - it was an entirely independent development.
Thetwo approaches are similar in the sense that there is no global clock, the commit time of a distributed transaction
isthe same in every partition where it modified data, and a transaction gets it snapshot timestamp from a local clock.
Thedifference is whether a distributed transaction gets its commit timestamp before or after the prepare phase in 2PC.
 

Hope this helpful.

Best regards,
Per-Ake
--------------------------------------------------


[Reply from the Clock-SI author Willy Zwaenepoel]
--------------------------------------------------
Thank you for your kind words about our work.

I was unaware of this patent at the time I wrote the paper. The two came out more or less at the same time.

I am not a lawyer, so I cannot tell you if something based on Clock-SI would infringe on the Microsoft patent. The main
distinctionto me seems to be that Clock-SI is based on physical clocks, while the Microsoft patent talks about logical
clocks,but again I am not a lawyer.
 

Best regards,

Willy.
--------------------------------------------------


Does this make sense from your viewpoint, and can we think that we can use Clock-SI without infrindging on the patent?
Accordingto the patent holder, the difference between Clock-SI and the patent seems to be fewer than the similarities.
 


Regards
Takayuki Tsunakawa