Fine Granular Locking in XML Databases
Jens Erat · KOPS (University of Konstanz) · 2013
XML databases gained highly in popularity over the last years, and queries performed got far more complex. Whereas mainly used for single threaded, often single user applications, usage for real-time, multi-user and parallel client-server environments increases. Along with that, demand for higher concurrency gets louder. This bachelor thesis analyses requirements on and searches for suitable concurrency control algorithms suitable for the sequential XML encoding based on the pre/post plane widely used in native XML databases. For comparing different concepts, two of them have been implemented for BaseX - one of those native database systems: - Conservative and strict two phase locking which was recognized as requirement to support all possible use cases, and - optimistic concurrency control as a very different approach on achieving higher parallelism. A short glimpse on other native XML database systems completes the evaluation of concurrency strategies. While tree locking protocols have been dismissed, possible ways to further enhance concurrency control in BaseX are illustrated and considered.