TwigStack+: Holistic twig join pruning using extended solution extension

Abstract

XML has been used extensively in many applications as a de facto standard for information representation and exchange over internet. Huge volumes of data are organized or exported in tree-structured form and the desired information can be got by traversing the whole tree structure using a twig pattern query. A new definition, Extended Solution Extension, is proposed in this paper to check the usefulness of an element from both forward and backward directions. Then a novel Extended Solution Extension based algorithm, TwigStack+, is also proposed to reduce the query processing cost, simply because it can check whether other elements can be processed together with the current one. Compared with existing methods, query evaluation cost can be largely reduced. The experimental results on various datasets indicate that the proposed algorithm performs significantly better than the existing ones.