Efficient Implementation of XQuery Constructor Expressions

Spring Young Researchers' Colloquium on Databases and Information Systems

c©Maxim Grinev Leonid Novak Ilya Taranov

PID  :  79819

来源: CEUR

【 摘 要 】

Element constructor is one of most expensive operations of the XQuery language as it re quires deep copy of the nodes which make up the content of the constructed element. In this paper we propose various optimization and im plementation techniques to avoid copying of the nodes during constructor evaluation. The proposed techniques are based on using spe cial kind of XQuery constructors with modi fied semantics which evaluation does not re quire content node copying. We also provide optimization rules which replace standard con structors with modified ones without changing query result. The proposed techniques are de signed to minimize modifications of an exist ing implementation. Possible technique exten sions which might depend on implementation specific features are also considered. We present results from experimental study of the techniques which demonstrate performance im