Transaction time indexing with version compression

Immortal DB is a transaction time database system designed to enable high performance for temporal applications. It is built into a commercial database engine, Microsoft SQL Server. This paper describes how we integrated a temporal indexing technique, the TSB-tree, into Immortal DB to serve as the core access method. The TSB-tree provides high performance access and update for both current and historical data. A main challenge was integrating TSB-tree functionality while preserving original B+tree functionality, including concurrency control and recovery. We discuss the overall architecture, including our unique treatment of index terms, and practical issues such as uncommitted data and log management. Performance is a primary concern. To increase performance, versions are locally delta compressed, exploiting the commonality between adjacent versions of the same record. This technique is also applied to index terms in index pages. There is a tradeoff between query performance and storage space. We discuss optimizing performance regarding this tradeoff throughout the paper. The result of our efforts is a high-performance transaction time database system built into an RDBMS engine, which has not been achieved before. We include a thorough experimental study and analysis that confirms the very good performance that it achieves.