p133-barta - Benefits of Path Summaries in an XML Query...

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Benefi Query Optimizer Supporting Multiple Access Methods cien onto 10 King’s College Rd., M5S 3G4, Toronto, ON, Canada P. Conse inee of Toro 5 King’s College Rd., M5S 3G8 co rto O. Mendelzon omputer Science ersity of Toronto 10 King’s College Rd., M5S to, ON, Canada cs.toronto.edu strat evalu se of nd re mon ement pported. In additio he speedups obtained using summaries with those reported for index-b w z ef Lan fo o anipulat XML documents. XQuery and its widely adopted Path r a d im /SQRL [13], ToX .g. Galax [20]) and work that addresses certain aspects of XQuery processing such as XPath, twig queries and index structures for XML query evaluation. in the area addresses uation, for the rest of nd XML query terms ery processing is the XML system, XML pecial purpose data execution. The most lies on an element on used in region tructure with element ng this type of data essions requires joins tural joins [3]. Also ding are the stack algorithms that y using stacks for ext, PathStack is proven g single path queries [7]. hms the region algebra encoded or the remain on this ents encoded in these ded streams , for elements and attributes, and value streams for CDATA. ontains several XPath ven in Figure 1. l")//supplier, ts of Path Summaries in an XML Attila Barta Dept. of Computer S ce Information Eng University of Tor Mariano ns Albe ring, MIE Dep. of C University nto Univ atibarta@cs.toronto.edu Abstract , Toronto, ON, Canada nsens@cs.toronto.edu 3G4, Toron mendel@ 1. Introduction Over the past few years the Extendible Markup (XML) has become the dominant data information exchange. With the proliferation this format comes the motivation to query and m egies ation path ly on strate s for n, we path ased -cost ation its as Moreover, because extensive work only some aspects of XQuery eval the paper we will use the XQuery a interchangeable. An important aspect of XML qu encoding used. That is, in a native documents can be pre-parsed into s structures in order to speedup query employed such data structure re encoding derived from the notati algebras [9]: an inverted-file-like s name, start, end and level. Utilizi structures for evaluating path expr between lists of encoded elements, referred to as containment queries [33] or struc based on region enco We compare several optimization implemented in an XML query system. The strategies incorporate the u summaries into the query optimizer, a heuristics that exploit data statistics. We present experimental results that de a wide range of performance improv the different strategies su compare t methods. The comparison shows that lo path summaries combined with optimi strategies achieve essentially the same ben more expensive index structures. improve on
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p133-barta - Benefits of Path Summaries in an XML Query...

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