Mechanism For Deferred Rewrite Of Multiple Xpath Evaluations Over Binary XML

摘要

A mechanism is provided for improving the performance of particular database queries operating on a view comprising binary-encoded XML. The key to improving performance is to determine whether a XML index is available to improve the computation of XPath data before deriving an optimized execution plan for a particular query. When a XML index is not available to help expedite the computation of binary-encoded XML, then deferring the computation of the XPath data until after the view merge stage avoids unnecessary computation of XPaths that are part of the view but not needed for the particular query.