Commutativity Analysis in XML Update Languages

Ghelli, Giorgio; Rose, Kristoffer H.; Simèon, Jérǒme

doi:10.1007/11965893_26

Cited by 11 publications

(8 citation statements)

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“…As observed in [14], commutativity is undecidable in general. To address that issue, we use the path analysis proposed in [14]: for every subplan p we collect the set of accessed paths a(p) and the set of updated paths u(p), which provide a static upper approximation of the nodes in the store that the plans reads and modifies.…”

Section: Definition (Commutativity)mentioning

confidence: 99%

“…Of course, this condition is always satisfied when the two plans are pure, since u(pi) is empty in that case. The main technical difference with [14] is that we extend the path language to deal with tuples. This extension is relatively straightforward and is not included here for space reasons.…”

Section: Definition (Commutativity)mentioning

confidence: 99%

“…To address that issue, we use the path analysis proposed in [14]: for every subplan p we collect the set of accessed paths a(p) and the set of updated paths u(p), which provide a static upper approximation of the nodes in the store that the plans reads and modifies. Two plans p1 and p2 commute if u(p1) is disjoint from a(p2) ∪ u(p2) and vice versa.…”

Section: Definition (Commutativity)mentioning

confidence: 99%

“…We show here that three side conditions suffice for this aim: commutativity, meaning that the evaluation order of two subplans can be exchanged, the aforementioned idempotency, and, in some cases, purity, indicating the absence of side effects. We also discuss how to infer the validity of these conditions for a plan, using static path analysis based on [14]. Using that technique, our optimizer can rewrite the plan above into the join-based plan shown in Figure 2.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

XML query optimization in the presence of side effects

Ghelli

Onose

Rose

et al. 2008

Proceedings of the 2008 ACM SIGMOD International Conference on Management of Data

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The emergence of database languages with side effects, notably for XML, raises significant challenges for database compilers and optimizers. In this paper, we extend an algebra for the W3C XML query language with operations that allow data to be immediately updated. We study the impact of that extension on logical optimization, join detection, and pipelining. The main result of this work is to show that, with proper care, a number of important optimizations based on nested relational algebras remain applicable in the presence of side effects. Our approach relies on an analysis of the conditions that must be checked in order for algebraic rewritings to hold. An implementation and experimental results demonstrate the effectiveness of the approach. INTRODUCTIONIn order to facilitate Web development, a number of languages blending database and programming language capabilities have recently been proposed [5,12,13,17,23]. Two well-known examples are LINQ [17], which extends .NET languages such as C# or Visual Basic with querying primitives, and XQueryP [5], which extends the W3C XML Query language [2] with imperative features. Such languages aim at simplifying existing Web development practices, which typically rely on several different languages used at different tiers. The ability to blend data processing and programming capabilities frees the developer from the need to rely on low-level APIs, or use language embedding, for data access, but also raises significant challenges for compilers. Many database compilers already support expressive languages such as object-oriented languages [8], PL/SQL [11], XSLT [7], or XQuery [2], however, most of the work on query optimization has focused on languages without side effects. Side effects are essential in order to support key programming extensions, such as updates and variable assignment in XQueryP [5], or method calls in object languages [8].In this paper, we propose techniques to adapt existing database compilers to support side effects in XQuery while Permission to make digital or hard copies of all or part of this work for personal or classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage and that copies bear this notice and the full citation on the first page. To copy otherwise, to republish, to post on servers or to redistribute to lists, requires prior specific permission and/or a fee. Copyright 200X ACM X-XXXXX-XX-X/XX/XX ...$5.00.preserving essential optimizations based on algebraic rewritings. Surprisingly, there has been very little work in that area in the past. One notable exception is [10] that uses a state monad [20] to support side effects in a nested-relational calculus. However, optimization at the algebraic, logical and physical level is not addressed. To the best of our knowledge, we provide the first treatment of side effects for a nestedrelational algebra. Due to space constraints, we limit our scope to updates applied during query evaluation, and leave procedural extensions (n...

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Section: Definition (Commutativity)mentioning

confidence: 99%

Section: Definition (Commutativity)mentioning

confidence: 99%

Section: Definition (Commutativity)mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

XML query optimization in the presence of side effects

Ghelli

Onose

Rose

et al. 2008

Proceedings of the 2008 ACM SIGMOD International Conference on Management of Data

Self Cite

View full text Add to dashboard Cite

show abstract

“…This approach is fundamentally different from the other XML update language proposals of which we are aware (such as XQuery! [11] and the draft W3C XQuery Update Facility [2]). Most such proposals contemplate adding unrestricted side-effecting update operations as additional XQuery expressions, which would undermine many of XQuery's advantages as a purely functional language, such as clear semantics and equational optimization laws.…”

Section: Related and Future Workmentioning

confidence: 99%

Regular Expression Subtyping for XML Query and Update Languages

Cheney

Programming Languages and Systems

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Abstract. XML database query languages such as XQuery employ regular expression types with structural subtyping. Subtyping systems typically have two presentations, which should be equivalent: a declarative version in which the subsumption rule may be used anywhere, and an algorithmic version in which the use of subsumption is limited in order to make typechecking syntax-directed and decidable. However, the XQuery standard type system circumvents this issue by using imprecise typing rules for iteration constructs and defining only algorithmic typechecking, and another extant proposal provides more precise types for iteration constructs but ignores subtyping. In this paper, we consider a core XQuery-like language with a subsumption rule and prove the completeness of algorithmic typechecking; this is straightforward for XQuery proper but requires some care in the presence of more precise iteration typing disciplines. We extend this result to an XML update language we have introduced in earlier work.

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Commutativity Analysis in XML Update Languages

Ghelli

Rose

Simèon

2006

Lecture Notes in Computer Science

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Abstract. A common approach to XML updates is to extend XQuery with update operations. This approach results in very expressive languages which are convenient for users but are difficult to reason about. Deciding whether two expressions can commute has numerous applications from view maintenance to rewriting-based optimizations. Unfortunately, commutativity is undecidable in most recent XML update languages. In this paper, we propose a conservative analysis for an expressive XML update language that can be used to determine whether two expressions commute. The approach relies on a form of path analysis that computes upper bounds for the nodes that are accessed or modified in a given update expression. Our main result is a commutativity theorem that can be used to identify commuting expressions.

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Commutativity Analysis in XML Update Languages

Cited by 11 publications

References 11 publications

XML query optimization in the presence of side effects

XML query optimization in the presence of side effects

Regular Expression Subtyping for XML Query and Update Languages

Commutativity Analysis in XML Update Languages

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