Chapter 6: Weak Isolation and Distribution Overview and Prevalence the Key Challenge: Reasoning about Anoma- Lies

Conventional database wisdom dictates that serializable transactions are the canonical solution to the problem of concurrent programming, but this is seldom the case in real-world databases. In practice, database systems instead overwhelmingly implement concurrency control that is nonserializable, exposing users to the possibility that their transactions will not appear to have executed in some serial order. In this chapter, we discuss why the use of this socalled “weak isolation” is so widespread, what these nonserializable isolation modes actually do, and why reasoning about them is so difficult.