Does Spanner have any native bitemporal support? I worked with bitemporal modeling on relational databases and the performance for some queries was heavily affected by the lack of native support for bitemporality, making it unacceptable in some cases. I know there are Crux and Datomic which are designed from the ground up to embrace bitemporality, I would love to have both native bitemporality in Spanner and all the other amazing benefits of Spanner (SaaS).