Benefits of path summaries in an XML query optimizer supporting multiple access methods

Abstract

We compare several optimization strategies implemented in an XML query evaluation system. The strategies incorporate the use of path summaries into the query optimizer, and rely on heuristics that exploit data statistics. We present experimental results that demonstrate a wide range of performance improvements for the different strategies supported. In addition, we compare the speedups obtained using path summaries with those reported for index-based methods. The comparison shows that low-cost path summaries combined with optimization strategies achieve essentially the same benefits as more expensive index structures. 1.