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This paper describes the design, implementation, and evaluation of Callas, a distributed database system that offers to unmodified, transactional ACID applications the opportunity to achieve a level of performance that can currently only be reached by rewriting all or part of the application in a BASE/NoSQL Style. The key to combining performance and ease of programming is to decouple the ACID abstraction---which Callas offers identically for all transactions---from the mechanism used to support it. MCC, the new Modular approach to Concurrency Control at the core of Callas, makes it possible to partition transactions in groups with the guarantee that, as long as the concurrency control mechanism within each group upholds a given isolation property, that property will also hold among transactions in different groups. Because of their limited and specialized scope, these group-specific mechanisms can be customized for concurrency with unprecedented aggressiveness. In our MySQL Cluster-based prototype, Callas yields an 8.2x throughput gain for TPC-C with no programming effort. |
