Optimizing Sorting and Duplicate Elimination in XQuery Path Expressions

Fernández, Mary; Hidders, Jan; Michiels, Philippe; Simèon, Jérǒme; Vercammen, Roel

doi:10.1007/11546924_54

Cited by 19 publications

(12 citation statements)

References 12 publications

(10 reference statements)

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“…However, order is an important issue in XML documents [6,1], and various index structure for ordered trees have been developed for XML documents [21,15,25]. When we view an XML document as an ordered tree, an existing fusion transformation like (F) by naive elimination of element constructors does not work correctly because the context, which is a navigation of newly constructed trees, is missing during the transformation.…”

Section: (F)mentioning

confidence: 99%

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Context-Preserving XQuery Fusion

Kato

Hidaka

et al. 2010

Programming Languages and Systems

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Abstract. XQuery is a DBPL for querying XML databases. The semantics of XQuery is context sensitive and requires preservation of document order. In this paper, we propose, as far as we are aware, the first XQuery fusion that can deal with both the document order and the context of XQuery expressions. More specifically, we carefully design a context representation of XQuery expressions based on the Dewey order encoding, develop a context-preserving XQuery fusion for ordered trees by static emulation of the XML store, and prove that our fusion is correct. Our XQuery fusion has been implemented, and all the examples in this paper have passed the system.

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Section: (F)mentioning

confidence: 99%

“…where n ∈ (R ∪ I) with R being a set of special codes 6 and I being a set of integers. It has a hierarchical structure, the same as in XQuery expressions, because xD is an annotation for an XQuery expression.…”

Section: Extended Dewey Codementioning

confidence: 99%

Context-Preserving XQuery Fusion

Kato

Hidaka

et al. 2010

Programming Languages and Systems

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“…The right-hand side computes the same result employing an ordered cross product and a subsequent selection, which filters all tuples that do not conform to the axis specification. 10 When a particular mapping does not depend on e j and a, those arguments are simply omitted. 11 This circumstance will be discussed at the end of this section.…”

Section: Definitionmentioning

confidence: 99%

Extending a tuple-based XPath algebra to enhance evaluation flexibility

Mathis

2007

Informatik Forsch. Entw.

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Over the recent years, very little effort has been made to give XPath a proper algebraic treatment. One laudable exception is the Natix Algebra (NAL) which defines the translation of XPath queries into algebraic expressions in a concise way, thereby enabling algebraic optimizations. However, NAL does not capture various promising core XML query evaluation algorithms like, for example, the Holistic Twig Join. By integrating a logical structural join operator, we enable NAL to be compiled into a physical algebra containing exactly those missing physical operators. We will provide several important query unnesting rules and demonstrate the effectivity of our approach by an implementation in the XML Transaction Coordinator (XTC) -our prototype of a native XML database system.

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“…Second, for the rules containing element constructors, node comparison operaCopyright c 2011 The Institute of Electronics, Information and Communication Engineers tors [6], [9] such as the is operator are not allowed. Third, we assume unordered mode, which is similar to the SQL rules.…”

Section: Introductionmentioning

confidence: 99%

Revisiting Source-Level XQuery Normalization

Lee

2011

IEICE Trans. Inf. & Syst.

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SUMMARYXQuery has become the standard for querying XML. Just like SQL, XQuery allows nested expressions. To optimize XQuery processing, a lot of research has been done on normalization, i.e., transforming nested expressions to equivalent unnested ones. Previous normalization rules are classified into two categories-source-level and algebra-leveldepending on whether a construct is specified in the XQuery syntax or as equivalent algebraic expressions. From an implementation point of view, the former is preferable to the latter since it can be implemented in a variety of XQuery engines with different algebras. However, existing source-level rules have several problems: They do not handle quantified expressions, incur duplicated query results, and use many temporary files. In this paper, we propose new source-level normalization rules that solve these problems. Through analysis and experiments, we show that our normalization rules can reduce query execution time from hours to a few seconds and can be adapted to a variety of XQuery engines.

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Optimizing Sorting and Duplicate Elimination in XQuery Path Expressions

Cited by 19 publications

References 12 publications

Context-Preserving XQuery Fusion

Context-Preserving XQuery Fusion

Extending a tuple-based XPath algebra to enhance evaluation flexibility

Revisiting Source-Level XQuery Normalization

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