Database Performance Report
A Comparison of the Relative Performance of
XML and SQL Databases in the Context of the Grid-SAFE
Project
Grid-SAFE is expected to allow its data to be queried using XPath. SAFE, Grid-SAFE's previous incarnation, uses a relational database to store its usage records. An XPath parser could be written to convert XPath queries into SQL queries, but an alternative solution would be to replace the underlying database with an XML database, allowing queries to be directly passed to the database without the need to analyse them. The key question then becomes one of performance - will an XML database provide acceptable levels of performance for the types of query required by the Grid-SAFE system.
An analysis was made of the eXist and Sedna XML databases to see if their performance was sufficient for Grid-SAFE's needs. When compared to the MySQL database currently used by SAFE, the XML databases took between 40 and 400 times longer to gather information in situations Grid-SAFE will commonly find itself in. Both databases were found to be inadequate for Grid-SAFE. Considering that these two XML database are fairly advanced compared with their peers, the practicality of using XPath as the standard query language is called into question.
