Avoiding Unnecessary Ordering Operations in XPath

Hidders, Jan; Michiels, Philippe

doi:10.1007/978-3-540-24607-7_5

Cited by 10 publications

(15 citation statements)

References 5 publications

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“…For example, the set of nodes selected by the equivalent forward query /descendant:b[descendant::a], as obtained by TRS 2 , is already in document order and has no duplicates. Static inference of these properties is investigated in [Hidders and Michiels 2003]. A technique largely based on TRS 2 is proposed in [Helmer et al 2002], where queries are translated to sequences of algebraic operations that do not generate duplicate nodes. ]…”

Section: Related Work and Applicationsmentioning

confidence: 99%

Forward node-selecting queries over trees

Olteanu

2007

ACM Trans. Database Syst.

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Node-selecting queries over trees lie at the core of several important XML languages for the Web, e.g., the node-selection language XPath, the query language XQuery and the transformation language XSLT. The main syntactic constructs of such queries are the backward predicates, e.g., ancestor and preceding, and the forward predicates, e.g., descendant and following. Forward predicates are included in the depth-first, left-to-right preorder relation associated with the input tree, whereas backward predicates are included in the inverse of this preorder relation.This work is devoted to an expressiveness study of node-selecting queries with proven theoretical and practical applicability, especially in the field of query evaluation against XML streams. The main question it answers positively is whether for each input query with forward and backward predicates there exists an equivalent forward-only output query. This question is then positively answered for input and output queries of varying structural complexity, using LOGLIN and PSPACE reductions.Various existing applications based on the results of this work are reported, including query optimization and streamed evaluation.

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Section: Related Work and Applicationsmentioning

confidence: 99%

Forward node-selecting queries over trees

Olteanu

2007

ACM Trans. Database Syst.

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“…[3,10,11,13,14,20]). and do not consider the physical placement of the data in secondary storage, or costs incurred by representation changes and main-memory access locality.…”

Section: Related Workmentioning

confidence: 97%

“…There is no hope for the construction of efficient XML query evaluation engines if path expressions cannot be evaluated efficiently, so it is no surprise that research about the efficient evaluation of XPath queries proliferates (e.g. [3,4,5,10,11,13,14,18,20,24]). It is surprising, however, that most approaches only consider the logical level.…”

Section: Introductionmentioning

confidence: 99%

Cost-sensitive reordering of navigational primitives

Kanne

Brantner

Moerkotte

2005

Proceedings of the 2005 ACM SIGMOD International Conference on Management of Data

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We present a method to evaluate path queries based on the novel concept of partial path instances. Our method (1) maximizes performance by means of sequential scans or asynchronous I/O, (2) does not require a special storage format, (3) relies on simple navigational primitives on trees, and (4) can be complemented by existing logical and physical optimizations such as duplicate elimination, duplicate prevention and path rewriting.We use a physical algebra which separates those navigation operations that require I/O from those that do not. All I/O operations necessary for the evaluation of a path are isolated in a single operator, which may employ efficient I/O scheduling strategies such as sequential scans or asynchronous I/O.Performance results for queries from the XMark benchmark show that reordering the navigation operations can increase performance up to a factor of four.

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“…Along the same line, translate XPath location steps without positional predicates such that creating duplicates is avoided. These ideas were extended in (Hidders & Michiels, 2003), where redundant sort operations are removed when the result of the path expression will still be in document order. (Brantner et.al, 2005) were the first to present a complete translation procedure for XPath 1.0 into algebraic expressions.…”

Section: Query Representations For Xquery Optimizationmentioning

confidence: 99%

“…Our motivation for doing so is that especially for simple path expressions many optimizations are known, e.g. (Amer-Yahia et al, 2001;Helmer et al, 2002;Hidders & Michiels, 2003;Balmin et al, 2004). Several of these optimizations are only tractable or applicable for simple path expressions.…”

Section: A Notation For Normalization Rulesmentioning

confidence: 99%

Normalization and Translation of XQuery

May

Moerkotte²

2010

Advanced Applications and Structures in XML Processing

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Early approaches to XQuery processing proposed proprietary techniques to optimize and evaluate XQuery statements. In this chapter, we argue for an algebraic optimization and evaluation technique for XQuery as it allows us to benefit from experience gained with relational databases. An algebraic XQuery processing method requires a translation into an algebra representation. While many publications already exist on algebraic optimizations and evaluation techniques for XQuery, an assessment of translation techniques is required. Consequently, we give a comprehensive survey for translating XQuery into various query representations. We relate these approaches to the way normalization and translation is implemented in Natix and discuss these two steps in detail. In our experience, our translation method is a good basis for further optimizations and query evaluation.

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Avoiding Unnecessary Ordering Operations in XPath

Cited by 10 publications

References 5 publications

Forward node-selecting queries over trees

Forward node-selecting queries over trees

Cost-sensitive reordering of navigational primitives

Normalization and Translation of XQuery

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