Xpath on Steroids: Exploiting Relational Engines for Xpath Performance+

摘要

A lot of research has been conducted by the database community on methods and techniques for efficient Xpath processing, with great success. Despite the progress made, significant opportunities for optimization of Xpath still exist. One key to further improvements is to utilize more effectively existing facilities of relational RDBSes for the processing of Xpath queries. After taking a comprehensive look at such facilities, we present techniques for Xpath processing that work by identifying the best relational join algorithms, indices and file organization strategies for Xpath queries. Our techniques both reduce the latency of the resulting SQL translations and guarantee their pipelined execution. We also propose a new technique for XML reconstruction from relations-mapped XML that "splits the difference" between schema-aware and schema-oblivious XML-to-relational mapping for a significant performance improvement. An extensive experimental study confirms the performance benefits of our optimization techniques and shows that a system implementing these techniques on top of a commercial RDBMS is competitive with respect to query performance with other native and relationalbased state-of-the-art Xpath processing systems, commercial as well as research prototypes.