Faster XPath processing on commodity relational systems

Vasilis Vassalos
Athens University of Economics and Business
(visiting UCSD)


I will describe a set of methods and techniques that significantly accelerate XPath processing on relational back-ends, 
are easy to implement and have wide applicability. The talk has two parts. 
First, I will describe a new way to process complex XPath queries, applicable to queries 
with all XPath axes, that is based on the splitting of XPath expressions into Primary Path Fragments (PPFs) 
and their subsequent combination using an efficient structural join method. I will also describe 
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. 
The second part of the talk will discuss how to utilize more effectively existing facilities of 
relational RDBSes for the processing of XPath queries. What are the best relational join algorithms, 
indices and file organization strategies for XPath queries? How do we both reduce the latency 
of the resulting SQL translations and guarantee their pipelined execution? 
Experimental results will be provided showing the performance benefits of our techniques.