Decomposing Transactional Systems

Decomposing Transactional Systems With thanks to Stu Hood, Giorgos Xanthakis, Phil Eaton, and Devan Benz for early reads and feedback. Every transactional system does four things: It executes transactions. It orders transactions. It validates transactions. It persists transactions. Executing a transaction means evaluating the body of the transaction to produce the intended reads and writes. There is still notable variety across systems as to how the body of a transaction is executed. Writes might be applied to storage during this phase, or they might be buffered locally and submitted as a batch at the end. A transaction might be executed more than once for different purposes. Ordering a transaction means assigning the transaction some notion of a time at which it occurred. This could be a version, a timestamp, a log sequence number, or a more complex description of transaction IDs it happened before or after. MVCC databases may assign two versions: an initial read version, and a f ... Read full article.