RE: Global snapshots - Mailing list pgsql-hackers

Hello,

While I'm thinking of the following issues of the current approach Andrey raised, I'm getting puzzled and can't help
askingcertain things.  Please forgive me if I'm missing some discussions in the past.
 

> 1. Dependency on clocks synchronization
> 2. Needs guarantees of monotonically increasing of the CSN in the case 
> of an instance restart/crash etc.
> 3. We need to delay increasing of OldestXmin because it can be needed 
> for a transaction snapshot at another node.

While Clock-SI seems to be considered the best promising for global serializability here,

* Why does Clock-SI gets so much attention?  How did Clock-SI become the only choice?

* Clock-SI was devised in Microsoft Research.  Does Microsoft or some other organization use Clock-SI?


Have anyone examined the following Multiversion Commitment Ordering (MVCO)?  Although I haven't understood this yet, it
insiststhat no concurrency control information including timestamps needs to be exchanged among the cluster nodes.  I'd
appreciateit if someone could give an opinion.
 

Commitment Ordering Based Distributed Concurrency Control for Bridging Single and Multi Version Resources.
 Proceedings of the Third IEEE International Workshop on Research Issues on Data Engineering: Interoperability in
MultidatabaseSystems (RIDE-IMS), Vienna, Austria, pp. 189-198, April 1993. (also DEC-TR 853, July 1992)
 
https://ieeexplore.ieee.org/document/281924?arnumber=281924


The author of the above paper, Yoav Raz, seems to have had strong passion at least until 2011 about making people
believethe mightiness of Commitment Ordering (CO) for global serializability.  However, he complains (sadly) that
almostall researchers ignore his theory, as written in his following  site and wikipedia page for Commitment Ordering.
Doesanyone know why CO is ignored?
 

Commitment ordering (CO) - yoavraz2
https://sites.google.com/site/yoavraz2/the_principle_of_co


FWIW, some researchers including Michael Stonebraker evaluated the performance of various distributed concurrency
controlmethods in 2017.  Have anyone looked at this?  (I don't mean there was some promising method that we might want
toadopt.)
 

An Evaluation of Distributed Concurrency Control
Rachael Harding, Dana Van Aken, Andrew Pavlo, and Michael Stonebraker. 2017.
Proc. VLDB Endow. 10, 5 (January 2017), 553-564. 
https://doi.org/10.14778/3055540.3055548


Regards
Takayuki Tsunakawa