For those interested in the details on the mentioned columnar storage engine "Ressi", this article doesn't really have anything, it is more about the migration process.

Apparently Ressi was meant to enter production in 2017 according to some older blog posts, so I'm not sure if this is a delay or the result of a long-running consolidation.

There are a few paragraphs about it in the SIGMOD '17 Spanner paper from Google

https://static.googleusercontent.com/media/research.google.c...