Design and Implementation of Transactions in a Column-Oriented In-Memory Database System

Coldbase is a column-oriented in-memory database implemented in Java that is used with a specific workload in mind. Coldbase is optimized to receive large streams of timestamped trading data arriving at a fast pace while allowing simple but frequent queries that analyse the data concurrently. By limiting the functionality, Coldbase is able to reach a high performance while keeping the memory consumption low. This thesis presents ColdbaseTX which is an extension to Coldbase that adds support for transactions. It uses an optimistic approach by storing all writes of transaction locally and applying them when the transaction commits. Readers are separated from writers by using two versions of the data which makes it possible to guarantee that readers are never blocked. Benchmarks compare Coldbase to ColdbaseTX regarding both performance and memory efficiency. The results show that ColdbaseTX presents a small overhead in both memory and performance which however is deemed acceptable since the gain is support for transactions.